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Materials, Volume 17, Issue 5 (March-1 2024) – 259 articles

Cover Story (view full-size image): This research assesses the effectiveness of Co3O4-gC3N4@ZnONPs catalysts in breaking down ciprofloxacin (CFX) and producing hydrogen (H2) via water splitting. Findings reveal that CFX undergoes rapid photodegradation, achieving up to a 99% reduction in 60 minutes, with 5%(Co3O4-gC3N4)@ZnONPs identified as the most efficient catalyst. Recyclability tests showed only a 6% decrease in activity after 15 cycles. The degradation pathway and by-products of CFX were identified using GC-MS, pointing towards a mechanism largely driven by superoxide radicals. Moreover, these catalysts displayed strong capability in generating H2, with outputs reaching 1407 µmol/hg in the visible light range. This highlights their potential for use in environmental cleanup and energy production. View this paper
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22 pages, 2943 KiB  
Article
Biocomposite Materials Derived from Andropogon halepensis: Eco-Design and Biophysical Evaluation
by Marcela-Elisabeta Barbinta-Patrascu, Cornelia Nichita, Bogdan Bita and Stefan Antohe
Materials 2024, 17(5), 1225; https://doi.org/10.3390/ma17051225 - 6 Mar 2024
Cited by 3 | Viewed by 1033
Abstract
This research work presents a “green” strategy of weed valorization for developing silver nanoparticles (AgNPs) with promising interesting applications. Two types of AgNPs were phyto-synthesized using an aqueous leaf extract of the weed Andropogon halepensis L. Phyto-manufacturing of AgNPs was achieved by two [...] Read more.
This research work presents a “green” strategy of weed valorization for developing silver nanoparticles (AgNPs) with promising interesting applications. Two types of AgNPs were phyto-synthesized using an aqueous leaf extract of the weed Andropogon halepensis L. Phyto-manufacturing of AgNPs was achieved by two bio-reactions, in which the volume ratio of (phyto-extract)/(silver salt solution) was varied. The size and physical stability of Andropogon—AgNPs were evaluated by means of DLS and zeta potential measurements, respectively. The phyto-developed nanoparticles presented good free radicals-scavenging properties (investigated via a chemiluminescence technique) and also urease inhibitory activity (evaluated using the conductometric method). Andropogon—AgNPs could be promising candidates for various bio-applications, such as acting as an antioxidant coating for the development of multifunctional materials. Thus, the Andropogon-derived samples were used to treat spider silk from the spider Pholcus phalangioides, and then, the obtained “green” materials were characterized by spectral (UV-Vis absorption, FTIR ATR, and EDX) and morphological (SEM) analyses. These results could be exploited to design novel bioactive materials with applications in the biomedical field. Full article
(This article belongs to the Special Issue Experimental Testing, Manufacturing and Numerical Modelling of Composite and Sandwich Structures)
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Figure 1

Figure 1
<p>Schematic representation of the eco-design and preparation of the materials derived from <span class="html-italic">Andropogon halepensis</span> L. The figure was created with Chemix (<a href="https://chemix.org/" target="_blank">https://chemix.org/</a>, accessed on 25 January 2024) and with PowerPoint and Paint 3D. This figure also contains images taken by us with a camera, an optical microscope, and SEM.</p> Full article ">Figure 2
<p>Comparative presentation of UV-Vis absorption spectra of <span class="html-italic">Andropogon</span>-derived samples. All AgNPs spectra were normalized at their maximum. The top inset shows the SPR bands of the <span class="html-italic">Andropogon</span>-derived AgNPs. The bottom inset shows the spectrum of <span class="html-italic">Andropogon halepensis</span> aqueous extract (EAh).</p> Full article ">Figure 3
<p>Comparative presentation of UV-Vis absorption spectra of the spider silk samples untreated (S) and treated with plant extract (S_EAh) or with silver nanoparticles obtained by <span class="html-italic">Bio-Reaction 1</span> (S_AgNPs_1n and S_AgNPs_1o) and <span class="html-italic">Bio-Reaction 2</span> (S_AgNPs_2n and S_AgNPs_2o).</p> Full article ">Figure 4
<p>Comparative presentation of FTIR ATR spectra of <span class="html-italic">Andropogon halepensis</span> extract (EAh) and the derived AgNPs phyto-synthesized through <span class="html-italic">Bio-Reaction 1</span> (AgNPs_1n and AgNPs_1o) and <span class="html-italic">Bio-Reaction 2</span> (AgNPs_2n and AgNPs_2o). The index “n” refers to the “new” synthesized nanoparticles, while the index “o” refers to the “old” (18 months aged) ones.</p> Full article ">Figure 5
<p>Comparative presentation of FTIR ATR spectra of the spider silk samples untreated (S) and treated with plant extract (S_EAh) or with silver nanoparticles obtained by <span class="html-italic">Bio-Reaction 1</span> (S_AgNPs_1n and S_AgNPs_1o) and <span class="html-italic">Bio-Reaction 2</span> (S_AgNPs_2n and S_AgNPs_2o) (<b>a</b>). Insets show the magnified regions of the FTIR ATR spectra of the biocomposites (<b>b</b>,<b>c</b>).</p> Full article ">Figure 6
<p>Comparative presentation of the electrokinetic potential of the <span class="html-italic">Andropogon</span>-derived silver nanoparticles. The AgNPs samples obtained through <span class="html-italic">Bio-Reaction</span> 1 (AgNPs_1n and AgNPs_1o) are placed next to those obtained through <span class="html-italic">Bio-Reaction</span> 2 (AgNPs_2n and AgNPs_2o) by alternating the aged samples with the fresh ones.</p> Full article ">Figure 7
<p>(<b>a</b>) Comparative presentation of the average particle size (Zav, nm) and PdI index of “green”-developed silver nanoparticles, estimated by dynamic light scattering (DLS) measurements; (<b>b</b>) Size distribution profiles of particle population for all types of phyto-developed AgNPs. For comparison, the aged AgNPs samples (AgNPs_1o and AgNPs_2o) are arranged next to the fresh ones (AgNPs_1n and AgNPs_2n).</p> Full article ">Figure 8
<p>The SEM images of the phyto-developed AgNPs (AgNPs_1n, AgNPs_1o, AgNPs_2n, and AgNPs_2o) and of the spider silk fibers (S) and spider silk biocomposites with plant extract (S_EAh) or with silver nanoparticles (S_AgNPs_1n, S_AgNPs_1o, S_AgNPs_2n, and S_AgNPs_2o).</p> Full article ">Figure 9
<p>The antioxidant activity of the <span class="html-italic">Andropogon halepensis</span> extract (EAh) and the phyto-metallic particles obtained by <span class="html-italic">Bio-Reaction 1</span> (AgNPs_1n and AgNPs_1o) and <span class="html-italic">Bio-Reaction 2</span> (AgNPs_2n and AgNPs_2o), estimated using the chemiluminescence technique.</p> Full article ">
24 pages, 7943 KiB  
Article
Electrical and Electro-Thermal Characteristics of (Carbon Black-Graphite)/LLDPE Composites with PTC Effect
by Eduard-Marius Lungulescu, Cristina Stancu, Radu Setnescu, Petru V. Notingher and Teodor-Adrian Badea
Materials 2024, 17(5), 1224; https://doi.org/10.3390/ma17051224 - 6 Mar 2024
Viewed by 1082
Abstract
Electrical properties and electro-thermal behavior were studied in composites with carbon black (CB) or hybrid filler (CB and graphite) and a matrix of linear low-density polyethylene (LLDPE). LLDPE, a (co)polymer with low crystallinity but with high structural regularity, was less studied for Positive [...] Read more.
Electrical properties and electro-thermal behavior were studied in composites with carbon black (CB) or hybrid filler (CB and graphite) and a matrix of linear low-density polyethylene (LLDPE). LLDPE, a (co)polymer with low crystallinity but with high structural regularity, was less studied for Positive Temperature Coefficient (PTC) applications, but it would be of interest due to its higher flexibility as compared to HDPE. Structural characterization by scanning electron microscopy (SEM) confirmed a segregated structure resulted from preparation by solid state powder mixing followed by hot molding. Direct current (DC) conductivity measurements resulted in a percolation threshold of around 8% (w) for CB/LLDPE composites. Increased filler concentrations resulted in increased alternating current (AC) conductivity, electrical permittivity and loss factor. Resistivity-temperature curves indicate the dependence of the temperature at which the maximum of resistivity is reached (Tmax(R)) on the filler concentration, as well as a differentiation in the Tmax(R) from the crystalline transition temperatures determined by DSC. These results suggest that crystallinity is not the only determining factor of the PTC mechanism in this case. This behavior is different from similar high-crystallinity composites, and suggests a specific interaction between the conductive filler and the polymeric matrix. A strong dependence of the PTC effect on filler concentration and an optimal concentration range between 14 and 19% were also found. Graphite has a beneficial effect not only on conductivity, but also on PTC behavior. Temperature vs. time experiments, revealed good temperature self-regulation properties and current and voltage limitation, and irrespective of the applied voltage and composite type, the equilibrium superficial temperature did not exceed 80 °C, while the equilibrium current traversing the sample dropped from 22 mA at 35 V to 5 mA at 150 V, proving the limitation capacities of these materials. The concentration effects revealed in this work could open new perspectives for the compositional control of both the self-limiting and interrupting properties for various low-temperature applications. Full article
(This article belongs to the Special Issue Advances in Polymer Blends and Composites)
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Figure 1

Figure 1
<p>Typical R vs. T heating (<b>a</b>) and T cooling (<b>b</b>) curve and kinetic parameters.</p> Full article ">Figure 2
<p>SEM images of some studied composites in a fresh state (unconditioned samples) at different magnifications: (<b>a</b>) LLD 190 (50,000×); (<b>b</b>) LLD 192 (50,000×); (<b>c</b>) LLD 192 (5000×); (<b>d</b>) LLD 122 (20,000×).</p> Full article ">Figure 3
<p>DSC curves of LLDPE and two different (CB-Gr)/LLDPE composites.</p> Full article ">Figure 4
<p>T<sub>m</sub> decrease with total carbon content: (1) composites with CB; (2) composites with CB and Gr.</p> Full article ">Figure 5
<p>DSC cooling curves of LLDPE (blank) and three different (CB, Gr)/LLDPE composites.</p> Full article ">Figure 6
<p>FTIR spectra of polymer matrix and different composites: 1—LLD 0; 2—LLD 120; 3—LLD 190; 4—LLD 122; 5—LLD 192.</p> Full article ">Figure 7
<p>σ<sub>DC</sub> vs. time, measured at 1 V for LLD neat samples (1) and LLD 80 (2), and at 100 V for LLD 44 (3) and LLD 82 (4).</p> Full article ">Figure 8
<p>DC conductivity vs. carbon black and graphite content of the studied composites: (○) CB-containing samples; (▲) CB + 2% graphite; (■) CB + 4% graphite.</p> Full article ">Figure 9
<p>Variation of AC conductivity with the frequency of the measuring voltage for different composites with an LLDPE matrix (U = 1 V).</p> Full article ">Figure 10
<p>Variation with frequency of the real part of the relative complex permittivity for different composites with an LLDPE matrix (U = 1 V).</p> Full article ">Figure 11
<p>The variation with frequency of the loss factor for LLD neat samples (U = 1 V).</p> Full article ">Figure 12
<p>R vs. T curves from (CB, Gr)/LLDPE composites at first heating cycle: 1—LLD 192; 2—LLD 190; 3—LLD 162; 4—LLD 160; 5—LLD 142; 6—LLD 140; 7—LLD 122; 8—LLD 82; 9—LLD 120; 10—LLD 100. The vertical red line correspond to the average T<sub>m(DSC)</sub> of the composites (125.5 °C).</p> Full article ">Figure 13
<p><span class="html-italic">R<sub>0</sub>/R<sub>f</sub></span> (•) and <span class="html-italic">PTC</span> intensity (○) of different composites (see numbers on the abscise): 1—LLD 192; 2—LLD 190; 3—LLD 162; 4—LLD 160; 5—LLD 142; 6—LLD 140; 7—LLD 122; 8—LLD 120; 9—LLD 82; 10—LLD 100. In the inset, decreasing R<sub>0</sub>/R<sub>f</sub> values for CB/LLDPE composites as CB content decreases.</p> Full article ">Figure 14
<p><span class="html-italic">T<sub>max(R)</sub></span> and <span class="html-italic">T<sub>max(DSC)</sub></span> vs. carbon content of composites (see numbers on the abscise): 1—LLD 0; 2—LLD 100; 3—LLD 82; 4—LLD 120; 5—LLD 122; 6—LLD 140; 7—LLD 142; 8—LLD 160; 9—LLD 162; 10—LLD 190; 11—LLD 192.</p> Full article ">Figure 15
<p>R vs. T curves from (CB, Gr)/LLDPE composites at first cooling cycle: 1—LLD 192; 2—LLD 190; 3—LLD 162; 4—LLD 160; 5—LLD 142; 6—LLD 140; 7—LLD 122; 8—LLD 82; 9—LLD 120. In inset, LLD 100 sample (note the max. of y scale is 800,000 kΩ). The vertical red line corresponds to average T<sub>c</sub> of the composites (112.8 °C).</p> Full article ">Figure 16
<p>The <span class="html-italic">T</span> vs. <span class="html-italic">t</span> curves for different applied voltages (AC) on the same composite sample LLD 192 (s10): (●) 3 V; (○) 5 V; (+) 8 V; (■) 10 V; (☐) 12 V; (×) 15 V; (▲) 20 V; (∆) 25 V; (♦) 35 V Levelling of temperature increase at 20 and 25 V can be clearly observed.</p> Full article ">Figure 17
<p>The T vs. t and I vs. t curves for LLD 192 sample (U = 50 V).</p> Full article ">Figure 18
<p>The T vs. t curves for LLD 192 at 20 V: (○) DC; (●) AC.</p> Full article ">Figure 19
<p>T<sub>eq</sub> vs. applied voltage for LLD 190 sample.</p> Full article ">
21 pages, 14659 KiB  
Article
Evaluation of Microstructure and Abrasive Wear-Resistance of Medium Alloy SiMo Ductile Cast Iron
by Łukasz Dyrlaga, Renata Zapała, Krzysztof Morgiel, Andrzej Studnicki, Andrzej Szczęsny and Dariusz Kopyciński
Materials 2024, 17(5), 1223; https://doi.org/10.3390/ma17051223 - 6 Mar 2024
Viewed by 865
Abstract
Medium-alloy ductile iron with a SiMo ferritic matrix has very good heat resistance. The addition of chromium and aluminum also increases this resistance. This article presents the impact of chromium and aluminum on the structure of SiMo cast iron, especially their impact on [...] Read more.
Medium-alloy ductile iron with a SiMo ferritic matrix has very good heat resistance. The addition of chromium and aluminum also increases this resistance. This article presents the impact of chromium and aluminum on the structure of SiMo cast iron, especially their impact on the deformation of the spherical graphite precipitates and the formation of M6C and M3C2 carbide phases. These carbides are formed in a ferritic matrix or at the grain boundaries, resulting in increased hardness and a drastic reduction in impact strength. The article presents the influence of heat treatment on the material’s microstructure and resistance to abrasive wear. Chromium and aluminum additions can also indirectly reduce the abrasive wear resistance of SiMo cast iron. The presented research shows the possibility of doubling the abrasive wear resistance of SiMo cast iron. Full article
(This article belongs to the Special Issue Research and Development in the World Foundry Engineering: Materials, Properties and Applications)
►▼ Show Figures

Figure 1

Figure 1
<p>Steel container (bell) containing nodulant and inoculant used in the process of nodularisation of molten metal.</p> Full article ">Figure 2
<p>Type 2 Y ingot with marked test sampling areas and dimensions in mm.</p> Full article ">Figure 3
<p>Scheme of ferritising annealing procedure that was used for SiMo cast iron carried out at METALPOL Węgierska Górka foundry.</p> Full article ">Figure 4
<p>3-POD tribotester: (<b>a</b>) device operation diagram; (<b>b</b>) view of working system (research samples–counter sample).</p> Full article ">Figure 5
<p>Simulation results for cast iron without addition of Cr and Al.</p> Full article ">Figure 6
<p>Simulation results for cast iron with addition of 1% Cr and 2% Al.</p> Full article ">Figure 7
<p>Simulation results for cast iron with addition of 3% Cr and 4% Al.</p> Full article ">Figure 8
<p>Microstructure of sample 0: (<b>a</b>) optical microscope: unetched, magnification 25×; (<b>b</b>) etched with nital, phases: light—ferrite, dark brown—perlite, black with a round shape—graphite, magnification 200×.</p> Full article ">Figure 9
<p>Microstructure of sample A, optical microscope: unetched, magnification 25× (<b>a</b>); etched with nital, phases: light—ferrite, shades of grey—carbides, black—graphite, magnification 200× (<b>b</b>).</p> Full article ">Figure 10
<p>EDS maps of sample A, indicating concentrations of (<b>a</b>) chromium, (<b>b</b>) iron, (<b>c</b>) molybdenum, and (<b>d</b>) manganese; (<b>e</b>,<b>f</b>) HAADF imaging (transmission microscope).</p> Full article ">Figure 11
<p>Microstructure of sample B, optical microscope: (<b>a</b>) unetched, magnification 25×; (<b>b</b>) etched with nital, phases: light—ferrite, shades of grey—carbides, black—graphite, magnification 200× (<b>b</b>).</p> Full article ">Figure 12
<p>Microstructure of sample B, etched with nital, magnification 2000× (SEM), 1 and 2—metal matrix, 3, 4 and 6—carbides, 5—molybdenum carbide precipitates.</p> Full article ">Figure 13
<p>EDS maps of Sample B, indicating concentrations of (<b>a</b>) chromium, (<b>b</b>) iron, (<b>c</b>) molybdenum, (<b>d</b>) manganese, and (<b>e</b>) aluminium; (<b>f</b>) HAADF imaging (transmission microscope).</p> Full article ">Figure 14
<p>Microstructure of Sample C, optical microscope: (<b>a</b>) unetched, magnification 25×; (<b>b</b>) etched with nital, phases: light—ferrite, shades of grey—carbides, black—graphite, magnification 200× (<b>b</b>).</p> Full article ">Figure 15
<p>Sample C etched with nital, magnification 2000× (SEM), 1 and 2—metal matrix, 3 and 4—carbides, 5 and 6—molybdenum carbide precipitates.</p> Full article ">Figure 16
<p>EDS maps of sample C, indicating concentrations of (<b>a</b>) chromium, (<b>b</b>) iron, (<b>c</b>) molybdenum, (<b>d</b>) manganese, and (<b>e</b>) aluminium; (<b>f</b>) HAADF imaging (transmission microscope).</p> Full article ">Figure 17
<p>Microstructure of sample D, optical microscope: (<b>a</b>) unetched, magnification 25×; (<b>b</b>) etched with nital, phases: light—ferrite, shades of grey—carbides, black—graphite, magnification 200× (<b>b</b>).</p> Full article ">Figure 18
<p>EDS maps of sample D, indicating concentrations of (<b>a</b>) chromium, (<b>b</b>) iron, (<b>c</b>) molybdenum, (<b>d</b>) manganese, and (<b>e</b>) aluminium; (<b>f</b>) HAADF imaging (transmission microscope).</p> Full article ">Figure 19
<p>Abrasive wear of tested samples as function of abrasion path with sample load of 230 G.</p> Full article ">Figure 20
<p>Abrasive wear of tested samples as function of abrasion path with sample load of 300 G.</p> Full article ">Figure 21
<p>Abrasive wear of tested samples as function of abrasion path with sample load of 380 G.</p> Full article ">Figure 22
<p>Effect of sample load on abrasive wear.</p> Full article ">Figure 23
<p>Relative resistance R to abrasive wear of tested samples (Reference Sample 0).</p> Full article ">
29 pages, 6030 KiB  
Review
Properties of Cementitious Materials Utilizing Seashells as Aggregate or Cement: Prospects and Challenges
by Yunpeng Zhu, Da Chen, Xiaotong Yu, Ruiwen Liu and Yingdi Liao
Materials 2024, 17(5), 1222; https://doi.org/10.3390/ma17051222 - 6 Mar 2024
Cited by 1 | Viewed by 2350
Abstract
Nowadays, the sustainable development of the construction industry has become a focus of attention. Crushing and grinding waste seashells originating from the fishery industry, such as oyster shells, cockle shells, mussel shells, and scallop shells, into different particle sizes for usage as aggregate [...] Read more.
Nowadays, the sustainable development of the construction industry has become a focus of attention. Crushing and grinding waste seashells originating from the fishery industry, such as oyster shells, cockle shells, mussel shells, and scallop shells, into different particle sizes for usage as aggregate and cement in concrete or mortar provides an effective and sustainable solution to environmental problems by reducing natural resource dependence. Numerous studies have attempted to analyze the suitability of waste seashell as a possible alternative to natural aggregates and cement in concrete or mortar. This paper presents an up-to-date review of the characteristics of different types of waste seashell, as well as the physical, mechanical, durability, and other notable functional properties of seashell concrete or mortar. From the outcome of the research, waste seashell could be an inert material, and it is important to conduct a series of proper treatment for a better-quality material. It is also seen from the results that although the mechanical properties of seashell concrete have been reduced, they all meet the required criteria set by various international standards and codes. Therefore, it is recommended that the replacement of seashells as aggregate and cement should not exceed 20% and 5%, respectively. Seashell concrete or mortar would then have sufficient workability and strength for non-structural purposes. However, there is still a lack of investigation concerning the different properties of reinforced concrete members using seashells as the replacement of aggregate or cement. Further innovative research can solidify its utilization towards sustainable development. Full article
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Figure 1

Figure 1
<p>Different types of seashells: (<b>a</b>) oyster, (<b>b</b>) crepidula, (<b>c</b>) scallops, (<b>d</b>) clam, (<b>e</b>) mussel, (<b>f</b>) cockle [<a href="#B20-materials-17-01222" class="html-bibr">20</a>,<a href="#B21-materials-17-01222" class="html-bibr">21</a>,<a href="#B22-materials-17-01222" class="html-bibr">22</a>,<a href="#B23-materials-17-01222" class="html-bibr">23</a>].</p> Full article ">Figure 2
<p>Co-occurrence of keywords (density mapping).</p> Full article ">Figure 3
<p>SEM analysis of mussel shell composition by Martínez-García et al. [<a href="#B29-materials-17-01222" class="html-bibr">29</a>]: (<b>a</b>) periostracum (external layer)—prismatic structure layer; (<b>b</b>) periostracum layer front view; (<b>c</b>) prismatic structure layer; (<b>d</b>) nacre layer front view; (<b>e</b>) nacre layer; (<b>f</b>) limestone particle.</p> Full article ">Figure 3 Cont.
<p>SEM analysis of mussel shell composition by Martínez-García et al. [<a href="#B29-materials-17-01222" class="html-bibr">29</a>]: (<b>a</b>) periostracum (external layer)—prismatic structure layer; (<b>b</b>) periostracum layer front view; (<b>c</b>) prismatic structure layer; (<b>d</b>) nacre layer front view; (<b>e</b>) nacre layer; (<b>f</b>) limestone particle.</p> Full article ">Figure 4
<p>Particle surface morphology of (<b>a</b>) limestone powder; (<b>b</b>) Portland cement powder; (<b>c</b>) seashell powder [<a href="#B28-materials-17-01222" class="html-bibr">28</a>].</p> Full article ">Figure 5
<p>SEM observation of microstructure of seashell concrete [<a href="#B20-materials-17-01222" class="html-bibr">20</a>].</p> Full article ">Figure 6
<p>Cracks in seashell particles and cement paste [<a href="#B30-materials-17-01222" class="html-bibr">30</a>].</p> Full article ">Figure 7
<p>SEM of hydrated cement matrix produced in seashell cement mixtures [<a href="#B28-materials-17-01222" class="html-bibr">28</a>]: (<b>a</b>) 100% OPC; (<b>b</b>) 10%Ca mixture; (<b>c</b>) 20%Ca mixture; (<b>d</b>) 40%Ca mixture.</p> Full article ">Figure 8
<p>Relationship between air content and organic matter content [<a href="#B29-materials-17-01222" class="html-bibr">29</a>].</p> Full article ">Figure 9
<p>Twenty-eight-day compressive strength of cementitious materials containing waste seashells: (<b>a</b>) fine aggregate replacement; (<b>b</b>) coarse aggregate replacement; (<b>c</b>) cement replacement [<a href="#B20-materials-17-01222" class="html-bibr">20</a>,<a href="#B23-materials-17-01222" class="html-bibr">23</a>,<a href="#B25-materials-17-01222" class="html-bibr">25</a>,<a href="#B33-materials-17-01222" class="html-bibr">33</a>,<a href="#B40-materials-17-01222" class="html-bibr">40</a>,<a href="#B41-materials-17-01222" class="html-bibr">41</a>,<a href="#B42-materials-17-01222" class="html-bibr">42</a>,<a href="#B53-materials-17-01222" class="html-bibr">53</a>,<a href="#B56-materials-17-01222" class="html-bibr">56</a>,<a href="#B58-materials-17-01222" class="html-bibr">58</a>,<a href="#B62-materials-17-01222" class="html-bibr">62</a>,<a href="#B71-materials-17-01222" class="html-bibr">71</a>,<a href="#B76-materials-17-01222" class="html-bibr">76</a>,<a href="#B83-materials-17-01222" class="html-bibr">83</a>,<a href="#B84-materials-17-01222" class="html-bibr">84</a>,<a href="#B93-materials-17-01222" class="html-bibr">93</a>,<a href="#B94-materials-17-01222" class="html-bibr">94</a>].</p> Full article ">Figure 9 Cont.
<p>Twenty-eight-day compressive strength of cementitious materials containing waste seashells: (<b>a</b>) fine aggregate replacement; (<b>b</b>) coarse aggregate replacement; (<b>c</b>) cement replacement [<a href="#B20-materials-17-01222" class="html-bibr">20</a>,<a href="#B23-materials-17-01222" class="html-bibr">23</a>,<a href="#B25-materials-17-01222" class="html-bibr">25</a>,<a href="#B33-materials-17-01222" class="html-bibr">33</a>,<a href="#B40-materials-17-01222" class="html-bibr">40</a>,<a href="#B41-materials-17-01222" class="html-bibr">41</a>,<a href="#B42-materials-17-01222" class="html-bibr">42</a>,<a href="#B53-materials-17-01222" class="html-bibr">53</a>,<a href="#B56-materials-17-01222" class="html-bibr">56</a>,<a href="#B58-materials-17-01222" class="html-bibr">58</a>,<a href="#B62-materials-17-01222" class="html-bibr">62</a>,<a href="#B71-materials-17-01222" class="html-bibr">71</a>,<a href="#B76-materials-17-01222" class="html-bibr">76</a>,<a href="#B83-materials-17-01222" class="html-bibr">83</a>,<a href="#B84-materials-17-01222" class="html-bibr">84</a>,<a href="#B93-materials-17-01222" class="html-bibr">93</a>,<a href="#B94-materials-17-01222" class="html-bibr">94</a>].</p> Full article ">Figure 10
<p>SEM of concrete: C-S-H gel grew on the smooth surface of oyster shells [<a href="#B42-materials-17-01222" class="html-bibr">42</a>].</p> Full article ">Figure 11
<p>(<b>a</b>) Relationship between splitting tensile strength and compressive strength [<a href="#B43-materials-17-01222" class="html-bibr">43</a>]; (<b>b</b>) relationship between flexural strength and compressive strength [<a href="#B40-materials-17-01222" class="html-bibr">40</a>].</p> Full article ">Figure 11 Cont.
<p>(<b>a</b>) Relationship between splitting tensile strength and compressive strength [<a href="#B43-materials-17-01222" class="html-bibr">43</a>]; (<b>b</b>) relationship between flexural strength and compressive strength [<a href="#B40-materials-17-01222" class="html-bibr">40</a>].</p> Full article ">Figure 12
<p>Stress–strain curves of mortars. (<b>a</b>) Curing day 28. (<b>b</b>) Curing day 90. Reference, mortar containing only river sand; WOS-10, -20, and -30, mortar samples containing 10%, 20%, and 30% crushed WOSs, respectively [<a href="#B33-materials-17-01222" class="html-bibr">33</a>].</p> Full article ">Figure 13
<p>Relationship between compressive strength and water permeability coefficient [<a href="#B40-materials-17-01222" class="html-bibr">40</a>].</p> Full article ">
15 pages, 436 KiB  
Review
Soft Tissue Substitutes in Periodontal and Peri-Implant Soft Tissue Augmentation: A Systematic Review
by Roberto Rotundo, Gian Luca Pancrazi, Alessia Grassi, Lara Ceresoli, Giovanna Laura Di Domenico and Vanessa Bonafede
Materials 2024, 17(5), 1221; https://doi.org/10.3390/ma17051221 - 6 Mar 2024
Viewed by 1456
Abstract
Background: Different extracellular matrix (ECM)-based technologies in periodontal and peri-implant soft tissue augmentation have been proposed in the market. The present review compared the efficacy of soft tissue substitutes (STSs) and autogenous free gingival grafts (FGGs) or connective tissue grafts (CTGs) in mucogingival [...] Read more.
Background: Different extracellular matrix (ECM)-based technologies in periodontal and peri-implant soft tissue augmentation have been proposed in the market. The present review compared the efficacy of soft tissue substitutes (STSs) and autogenous free gingival grafts (FGGs) or connective tissue grafts (CTGs) in mucogingival procedures to increase keratinized tissue (KT) width around teeth and implants. Methods: Two independent examiners performed an electronic search on MEDLINE and the Cochrane Library based on the following PICOS format: (P) adult patients; (I) soft tissue substitutes and FGGs/CTGs; (C) STSs vs. CTGs; STSs vs. FGGs; STSs vs control; (O) KT width gain; (S) systematic reviews, randomized controlled trials. Studies published before November 2023 were included. Results: Around teeth, all biomaterials showed superior performance compared to a coronally advanced flap (CAF) alone for treating gingival recessions. However, when compared to CTGs, acellular dermal matrices (ADMs) yield the most similar outcomes to the gold standard (CTGs), even though in multiple recessions, CTGs continue to be considered the most favorable approach. The use of STSs (acellular matrix or tissue-engineered) in combination with apically positioned flaps (APF) resulted in significantly less gain in KT width compared to that achieved with FGGs and APFs. Around dental implants, free gingival grafts were deemed more effective than soft tissue substitutes in enhancing keratinized mucosa width. Conclusions: Based on the available evidence, questions remain about the alternative use of soft tissue substitutes for conventional grafting procedures using free gingival grafts or connective tissue grafts around teeth and implants. Full article
(This article belongs to the Special Issue Materials and Devices for Multidisciplinary Dental Treatments)
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<p>Flow chart diagram of selected studies. For each soft tissue substitute (STS), the related number of systematic reviews (SR) and randomized controlled trials (RCT) are reported. ADM: allogeneic dermal matrix; CAF: coronally advanced flap; CTG: connective tissue graft; FGG: free gingival graft; TUN: tunnel technique; XDM: xenogeneic dermal matrix; CMX: xenogeneic collagen matrix; VCMX: volume-stable collagen matrix.</p> Full article ">
12 pages, 9954 KiB  
Article
Amino-Modified Graphene Oxide from Kish Graphite for Enhancing Corrosion Resistance of Waterborne Epoxy Coatings
by Shengle Hao, Siming Wan, Shiyu Hou, Bowen Yuan, Chenhui Luan, Ding Nan, Gen Huang, Deping Xu and Zheng-Hong Huang
Materials 2024, 17(5), 1220; https://doi.org/10.3390/ma17051220 - 6 Mar 2024
Viewed by 900
Abstract
Waterborne epoxy (WEP) coatings with enhanced corrosion resistance were prepared using graphene oxide (GO) that was obtained from kish graphite, and amino-functionalized graphene oxide (AGO) was modified by 2-aminomalonamide. The structural characteristics of the GO and AGO were analyzed using X-ray diffraction (XRD), [...] Read more.
Waterborne epoxy (WEP) coatings with enhanced corrosion resistance were prepared using graphene oxide (GO) that was obtained from kish graphite, and amino-functionalized graphene oxide (AGO) was modified by 2-aminomalonamide. The structural characteristics of the GO and AGO were analyzed using X-ray diffraction (XRD), Raman spectroscopy, Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). And the anti-corrosive performance of waterborne epoxy-cased composite coatings with different addition amounts of AGO was investigated using electrochemical measurements, pull-off adhesion tests, and salt spray tests. The results indicate that AGO15/WEP with 0.15 wt.% of AGO has the best anti-corrosive performance, and the lowest frequency impedance modulus increased from 1.03 × 108 to 1.63 × 1010 ohm·cm−2 compared to that of WEP. Furthermore, AGO15/WEP also demonstrates the minimal corrosion products or bubbles in the salt spray test for 200 h, affirming its exceptional long-term corrosion protection capability. Full article
(This article belongs to the Section Carbon Materials)
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<p>The mechanism diagram of AGO synthesis.</p> Full article ">Figure 2
<p>XRD (<b>a</b>), Raman (<b>b</b>), and FT-IR spectra (<b>c</b>) of GO, AGO55, AGO65, AGO75, and AGO85.</p> Full article ">Figure 3
<p>SEM and EDS mapping images of GO (<b>a</b>) and AGO65 (<b>b</b>), TEM images of GO (<b>c</b>) and AGO65 (<b>d</b>).</p> Full article ">Figure 4
<p>The fracture surfaces for (<b>a</b>) WEP, (<b>b</b>) AGO05/WEP, (<b>c</b>) AGO15/WEP, and (<b>d</b>) AGO30/WEP coatings.</p> Full article ">Figure 5
<p>Bode diagrams (<b>a</b>) and Nyquist diagrams (<b>b</b>) of coatings after immersion in a 3.5 wt.% NaCl solution for 24 h.</p> Full article ">Figure 6
<p>Tafel curves of WEP, GO/WEP, and AGO/WEP coatings.</p> Full article ">Figure 7
<p>The adhesion of WEP, GO/WEP, and AGO/WEP coatings.</p> Full article ">Figure 8
<p>Surface morphology of the (<b>a</b>) WEP, (<b>b</b>) GO/WEP, (<b>c</b>) AGO05/WEP, (<b>d</b>) AGO15/WEP, and (<b>e</b>) AGO30/WEP coatings after the salt spray test for 200 h.</p> Full article ">Figure 9
<p>Schematic diagram of the corrosion protection mechanism for (<b>a</b>) WEP, (<b>b</b>) GO/WEP, (<b>c</b>) AGO15/WEP, and (<b>d</b>) AGO30/WEP coatings.</p> Full article ">
9 pages, 1875 KiB  
Article
Influence of Accelerators on Cement Mortars Using Fluid Catalytic Cracking Catalyst Residue (FCC): Enhanced Mechanical Properties at Early Curing Ages
by Lourdes Soriano, María Victoria Borrachero, Ester Giménez-Carbo, Mauro M. Tashima, José María Monzó and Jordi Payá
Materials 2024, 17(5), 1219; https://doi.org/10.3390/ma17051219 - 6 Mar 2024
Viewed by 730
Abstract
Supplementary cementitious materials (SCMs) have been used in the construction industry to mainly reduce the greenhouse gas emissions associated with Portland cement. Of SCMs, the petrochemical industry waste known as fluid catalytic cracking catalyst residue (FCC) is recognized for its high reactivity. Nevertheless, [...] Read more.
Supplementary cementitious materials (SCMs) have been used in the construction industry to mainly reduce the greenhouse gas emissions associated with Portland cement. Of SCMs, the petrochemical industry waste known as fluid catalytic cracking catalyst residue (FCC) is recognized for its high reactivity. Nevertheless, the binders produced using SCMs usually present low mechanical strength at early curing ages. This study aims to assess the effect of different accelerating additives (KOH, sodium silicate SIL, commercial additive SKR) on the mechanical strength of mortars containing FCC. The results show that after only 8 curing hours, the compressive strength gain of the FCC mortars containing SKR was over 100% compared to the FCC mortar with no additive (26.0 vs. 12.8 MPa). Comparing the compressive strength of FCC mortar containing SKR to the control mortar, the enhancement is spetacular (6.85 vs. 26.03 MPa). The effectiveness of the tested accelerators at 8–24 curing hours was KOH ≈ SIL < SKR, whereas it was KOH < SIL < SKR for 48 h–28 days. The thermogravimetric data confirmed the good compatibility of FCC and the commercial accelerator. Full article
(This article belongs to the Special Issue Advances in the Design and Properties of New Ecoconcrete Formulations)
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<p>RAI values or the different accelerating additives during the 8 h to 48 h periods: (<b>a</b>) SKR accelerator; (<b>b</b>) KOH accelerator; (<b>c</b>) SIL accelerator.</p> Full article ">Figure 2
<p>DTG curves for the control pastes at different curing ages: (<b>a</b>) 8 h; (<b>b</b>) 24 h; (<b>c</b>) 48 h; (<b>d</b>) 28 days.</p> Full article ">Figure 3
<p>DTG curves for the FCC pastes at different curing ages: (<b>a</b>) 8 h; (<b>b</b>) 24 h; (<b>c</b>) 48 h; (<b>d</b>) 28 days.</p> Full article ">
14 pages, 5935 KiB  
Article
Suitability of Gelatin Methacrylate and Hydroxyapatite Hydrogels for 3D-Bioprinted Bone Tissue
by Paul Stolarov, Jonathan de Vries, Sean Stapleton, Lauren Morris, Kari Martyniak and Thomas J. Kean
Materials 2024, 17(5), 1218; https://doi.org/10.3390/ma17051218 - 6 Mar 2024
Cited by 2 | Viewed by 1647
Abstract
Background: Complex bone defects are challenging to treat. Autografting is the gold standard for regenerating bone defects; however, its limitations include donor-site morbidity and increased surgical complexity. Advancements in 3D bioprinting (3DBP) offer a promising alternative for viable bone grafts. In this experiment, [...] Read more.
Background: Complex bone defects are challenging to treat. Autografting is the gold standard for regenerating bone defects; however, its limitations include donor-site morbidity and increased surgical complexity. Advancements in 3D bioprinting (3DBP) offer a promising alternative for viable bone grafts. In this experiment, gels composed of varying levels of gelatin methacrylate (GelMA) and hydroxyapatite (HA) and gelatin concentrations are explored. The objective was to increase the hydroxyapatite content and find the upper limit before the printability was compromised and determine its effect on the mechanical properties and cell viability. Methods: Design of Experiments (DoE) was used to design 13 hydrogel bioinks of various GelMA/HA concentrations. These bioinks were assessed in terms of their pipettability and equilibrium modulus. An optimal bioink was designed using the DoE data to produce the greatest stiffness while still being pipettable. Three bioinks, one with the DoE-designed maximal stiffness, one with the experimentally defined maximal stiffness, and a literature-based control, were then printed using a 3D bioprinter and assessed for print fidelity. The resulting hydrogels were combined with human bone-marrow-derived mesenchymal stromal cells (hMSCs) and evaluated for cell viability. Results: The DoE ANOVA analysis indicated that the augmented three-level factorial design model used was a good fit (p < 0.0001). Using the model, DoE correctly predicted that a composite hydrogel consisting of 12.3% GelMA, 15.7% HA, and 2% gelatin would produce the maximum equilibrium modulus while still being pipettable. The hydrogel with the most optimal print fidelity was 10% GelMA, 2% HA, and 5% gelatin. There were no significant differences in the cell viability within the hydrogels from day 2 to day 7 (p > 0.05). There was, however, a significantly lower cell viability in the gel composed of 12.3% GelMA, 15.7% HA, and 2% gelatin compared to the other gels with a lower HA concentration (p < 0.05), showing that a higher HA content or print pressure may be cytotoxic within hydrogels. Conclusions: Extrusion-based 3DBP offers significant advantages for bone–tissue implants due to its high customizability. This study demonstrates that it is possible to create printable bone-like grafts from GelMA and HA with an increased HA content, favorable mechanical properties (145 kPa), and a greater than 80% cell viability. Full article
(This article belongs to the Special Issue Recent Advances in the Field of Mechanical Metamaterials and Their Associated Applications and Fabrication Techniques)
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<p><b>Bioprinter assembly</b>: (<b>A</b>) BioAssemblyBot 3D bioprinter from Advanced Solutions Inc. (<b>B</b>) Cartridges containing the bioinks were inserted into the heating tool and allowed to warm to the desired temperature before printing. (<b>C</b>) Example of 3D construct printed with hydroxyapatite-rich composite hydrogel. (<b>D</b>) 405 nm laser adapter for simultaneous printing and crosslinking.</p> Full article ">Figure 2
<p><b>CAD model used for print fidelity</b>: (<b>A</b>) Square zig-zag pattern of 8.9 mm length, 10.9 mm width, and line thickness of ~0.9 mm using TSIM. (<b>B</b>) Example of an overlaid image with areas of the actual print (Line 1) and theoretical pore size (Line 2) delineated.</p> Full article ">Figure 3
<p><b>DoE surface model</b>: Showing the standard error of design.</p> Full article ">Figure 4
<p><b>Printability of composite hydrogels</b>: G10H33, G12.5H25, G15H17, and G15H33 were not printable, nor could they be pipetted under 37 °C. All other hydrogels were both extrudable and printable.</p> Full article ">Figure 5
<p><b>Three-dimensional surface model of compression results</b>: Higher GelMA and HA % corresponded to higher equilibrium moduli.</p> Full article ">Figure 6
<p><b>Printability and print fidelity of GelMA/HA composite hydrogels</b>: (<b>A</b>) Extrusion bioprinting process and the contents of each bioink. Created using BioRender. (<b>B</b>) Determinations of print settings for extrusion of a continuous filament. (<b>C</b>) Images of printed lines with each gel (Keyence VHX-7000 microscope). Gel 3 produced the highest print fidelity. Scale bar = 1 mm.</p> Full article ">Figure 7
<p><b>Cell viability in GelMA/HA bioinks:</b> (<b>A</b>) hMSC viability in each of the three gels at day 2 and day 7. Gels 2 and 3 showed significantly higher cell viability as compared to Gel 1. There was no difference between pipetted and printed cell viability in Gel 1. There was also no difference in cell viability from day 2 to day 7 in any gel. (<b>B</b>) Live hMSCs stained green and dead hMSCs stained red; composite images are shown.</p> Full article ">
20 pages, 7712 KiB  
Article
The Influence of the Shielding-Gas Flow Rate on the Mechanical Properties of TIG-Welded Butt Joints of Commercially Pure Grade 1 Titanium
by Krzysztof Szwajka, Joanna Zielińska-Szwajka and Tomasz Trzepieciński
Materials 2024, 17(5), 1217; https://doi.org/10.3390/ma17051217 - 6 Mar 2024
Viewed by 911
Abstract
This article proposes as a novelty the differentiation of shielding-gas flow rates from both sides of the tungsten inert gas (TIG)-welded butt joints of commercially pure (CP) grade 1 titanium tubes. Such an approach is aimed at economically reducing the amount of protective [...] Read more.
This article proposes as a novelty the differentiation of shielding-gas flow rates from both sides of the tungsten inert gas (TIG)-welded butt joints of commercially pure (CP) grade 1 titanium tubes. Such an approach is aimed at economically reducing the amount of protective gas used in TIG closed butt welding. The effect of the shielding-gas flow rate on the properties of CP grade 1 titanium butt-welded joints made using the tungsten inert gas (TIG)-welding method. Butt-welded joints were made for different values of the shielding-gas flow from the side of the root of the weld. Argon 5.0 was used as the shielding gas in the welding process. As part of the research, the welded joints obtained were analysed using optical and scanning electron microscopy. The microstructural characteristics of the joints were examined using an optical microscope, and the mechanical properties were determined using hardness and tensile tests. It was observed that as the flow of the shielding gas decreases, the hardness of the weld material increases and its brittleness also increases. A similar trend related to the amount of gas flow was also noticeable for the tensile strength of the joints. The increase in the hardness of the weld and the heat-affected zone compared to the base metal is mainly related to the increase in the amount of acicular structure (α′ phase). The optimal gas flow rates from the side of the root of weld were found at the values of 12 dm3/min. Full article
(This article belongs to the Special Issue Advances in Welding Techniques, Welding Inspection, and Welding Testing Methods)
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<p>The shape of the CP (Grade 1) titanium specimens.</p> Full article ">Figure 2
<p>(<b>a</b>) The supply of the shielding gas from the side of the root of weld, (<b>b</b>) the welding positioner and (<b>c</b>) the TIG torch.</p> Full article ">Figure 3
<p>Samples prepared for static tensile testing.</p> Full article ">Figure 4
<p>(<b>a</b>) The positioned specimen and (<b>b</b>) the hardness measurement locations (1–7).</p> Full article ">Figure 5
<p>(<b>a</b>,<b>b</b>) Optical microstructures of the test material.</p> Full article ">Figure 6
<p>Microstructure of the base metal.</p> Full article ">Figure 7
<p>The results of the microhardness measurements of the welded joints for (<b>a</b>) TIG_1, (<b>b</b>) TIG_2, (<b>c</b>) TIG_3, (<b>d</b>) TIG_4 and (<b>e</b>) TIG_5.</p> Full article ">Figure 8
<p>(<b>a</b>) Tensile curves and (<b>b</b>) and the average grain size in the welded joint.</p> Full article ">Figure 9
<p>View of samples after the static tensile test.</p> Full article ">Figure 10
<p>Photographs of welded joints made from the face of the weld and the root of the weld.</p> Full article ">Figure 11
<p>Microstructure of the TIG_3 sample: (<b>a</b>) locations of weld assessment and (<b>b</b>) views of the microstructure under 5× magnification (<b>left</b>) and 20× (<b>right</b>).</p> Full article ">Figure 12
<p>Pores revealed in the TIG_1 weld.</p> Full article ">Figure 13
<p>Microstructure of the TIG_1 weld: (<b>a</b>) base metal, (<b>b</b>) HAZ and (<b>c</b>) weld zone.</p> Full article ">Figure 14
<p>Microstructure of the TIG_3 welded joint: (<b>a</b>) microstructure of the base metal, (<b>b</b>) microstructure of the HAZ and (<b>c</b>) weld microstructure.</p> Full article ">Figure 15
<p>X-ray diffraction patterns across the welded joints.</p> Full article ">
0 pages, 1639 KiB  
Communication
Controllable Technology for Thermal Expansion Coefficient of Commercial Materials for Solid Oxide Electrolytic Cells
by Ya Sun, Dun Jin, Xi Zhang, Qing Shao, Chengzhi Guan, Ruizhu Li, Fupeng Cheng, Xiao Lin, Guoping Xiao and Jianqiang Wang
Materials 2024, 17(5), 1216; https://doi.org/10.3390/ma17051216 - 6 Mar 2024
Cited by 1 | Viewed by 1047
Abstract
Solid oxide electrolysis cell (SOEC) industrialization has been developing for many years. Commercial materials such as 8 mol% Y2O3-stabilized zirconia (YSZ), Gd0.1Ce0.9O1.95 (GDC), La0.6Sr0.4Co0.2Fe0.8O3−δ (LSCF), [...] Read more.
Solid oxide electrolysis cell (SOEC) industrialization has been developing for many years. Commercial materials such as 8 mol% Y2O3-stabilized zirconia (YSZ), Gd0.1Ce0.9O1.95 (GDC), La0.6Sr0.4Co0.2Fe0.8O3−δ (LSCF), La0.6Sr0.4CoO3−δ (LSC), etc., have been used for many years, but the problem of mismatched thermal expansion coefficients of various materials between cells has not been fundamentally solved, which affects the lifetime of SOECs and restricts their industry development. Currently, various solutions have been reported, such as element doping, manufacturing defects, and introducing negative thermal expansion coefficient materials. To promote the development of the SOEC industry, a direct treatment method for commercial materials—quenching and doping—is reported to achieve the controllable preparation of the thermal expansion coefficient of commercial materials. The quenching process only involves the micro-treatment of raw materials and does not have any negative impact on preparation processes such as powder slurry and sintering. It is a simple, low-cost, and universal research strategy to achieve the controllable preparation of the thermal expansion coefficient of the commercial material La0.6Sr0.4Co0.2Fe0.8O3−δ (LSCF) through a quenching process by doping elements and increasing oxygen vacancies in the material. Commercial LSCF materials are heated to 800 °C in a muffle furnace, quickly removed, and cooled and quenched in 3.4 mol/L of prepared Y(NO3)3. The thermal expansion coefficient of the treated material can be reduced to 13.6 × 10−6 K−1, and the blank sample is 14.1 × 10−6 K−1. In the future, it may be possible to use the quenching process to select appropriate doping elements in order to achieve similar thermal expansion coefficients in SOECs. Full article
(This article belongs to the Section Energy Materials)
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<p>Thermal expansion coefficient test. (<b>a</b>) Scatter plot of thermal expansion coefficient with temperature variation (<b>b</b>) Histogram of thermal expansion coefficient with temperature variation.</p> Full article ">Figure 2
<p>Material XRD characterization.</p> Full article ">Figure 3
<p>TEM and mapping.</p> Full article ">
16 pages, 6462 KiB  
Article
Synergistic Effect of Carbon Micro/Nano-Fillers and Surface Patterning on the Superlubric Performance of 3D-Printed Structures
by Katerina Gkougkousi, Alexandros E. Karantzalis, Pantelis G. Nikolakopoulos and Konstantinos G. Dassios
Materials 2024, 17(5), 1215; https://doi.org/10.3390/ma17051215 - 6 Mar 2024
Viewed by 1061
Abstract
Superlubricity, the tribological regime where the coefficient of friction between two sliding surfaces almost vanishes, is currently being investigated as a viable route towards the energy efficiency envisioned by major long-term strategies for a sustainable future. This current study provides new insights towards [...] Read more.
Superlubricity, the tribological regime where the coefficient of friction between two sliding surfaces almost vanishes, is currently being investigated as a viable route towards the energy efficiency envisioned by major long-term strategies for a sustainable future. This current study provides new insights towards the development of self-lubricating systems by material and topological design, systems which tend to exhibit near-superlubric tribological performance, by reporting the synergistic effect of selective surface patterning and presence of carbon micro/nano-fillers on the frictional coefficients of additively manufactured structures. Geometric and biomimetic surface patterns were prepared by fused deposition modelling (FDM), using printing filaments of a polymeric matrix infused with graphene nanoplatelets (GNPs) and carbon fibers (Cf). The calorimetric, spectroscopic, mechanical and optical microscopy characterization of the starting materials and as-printed structures provided fundamental insights for their tribological characterization under a ball-on-disk configuration. In geometrically patterned PLA-based structures, a graphene presence reduced the friction coefficient by ca. 8%, whereas PETG exhibited the lowest coefficients, in the vicinity of 0.1, indicating a high supelubric potential. Biomimetic patterns exhibited an inferior frictional response due to their topologically and tribologically anisotropy of the surfaces. Overall, a graphene presence in the starting materials demonstrated great potential for friction reduction, while PETG showed a tribological performance not only superior to PLA, but also compatible with superlubric performance. Methodological and technical challenges are discussed in the text. Full article
(This article belongs to the Special Issue Nanocomposite Based Materials for Various Applications)
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<p>Dimensional characteristics of as-designed geometric cubic structures (<b>a</b>,<b>c</b>) and biomimetic snakeskin structures (<b>b</b>,<b>d</b>).</p> Full article ">Figure 2
<p>Main instrumentation used for (<b>a</b>) mechanical testing, (<b>b</b>) surface topography and roughness and (<b>c</b>) tribometry.</p> Full article ">Figure 3
<p>Raman spectra of composite PLA filaments with embedded graphene nanoplates.</p> Full article ">Figure 4
<p>Raman spectra of composite PETG filaments with embedded carbon fibers.</p> Full article ">Figure 5
<p>Optical microscopy images of interior of composite PETG filaments with embedded carbon fibers at different magnifications: (<b>a</b>,<b>b</b>) longitudinal sections and (<b>c</b>,<b>d</b>) cross sections.</p> Full article ">Figure 6
<p>Statistical angle of misalignment, with respect to filament axis, of carbon fibers embedded in PETG composite filaments.</p> Full article ">Figure 7
<p>Range of carbon fiber lengths embedded in the PETG composite filaments.</p> Full article ">Figure 8
<p>Optical microscopy images of 3D-printed structures at different magnification levels. Top row (<b>a</b>,<b>b</b>): structures made from composite PETG-C<sub>f</sub> filaments. Bottom row (<b>c</b>,<b>d</b>): structures made from composite PLA-GNP filaments.</p> Full article ">Figure 9
<p>Typical stress–strain curves of tensile coupons, 3D printed following the same cycle as the tribological structures, for characterization of the mechanical properties of the as-printed materials.</p> Full article ">Figure 10
<p>Temporal variation of friction coefficient, under ball-on-disk configuration, for geometric structures additively manufactured from four different precursors: (<b>a</b>) PLA, (<b>b</b>) PLA-GNP, (<b>c</b>) PETG, (<b>d</b>) PETG-C<sub>f</sub>. Blue symbols are the friction coefficient and red lines represent their mean values in each instance of the experiment.</p> Full article ">Figure 11
<p>Temporal variation of friction coefficient, under ball-on-disk configuration, for biomimetic snakeskin structures additively manufactured from four different precursors: (<b>a</b>) PLA, (<b>b</b>) PLA-GNP, (<b>c</b>) PETG, (<b>d</b>) PETG-C<sub>f</sub>. Blue symbols are the friction coefficient and red lines represent their mean values in each instance of the experiment.</p> Full article ">Figure 11 Cont.
<p>Temporal variation of friction coefficient, under ball-on-disk configuration, for biomimetic snakeskin structures additively manufactured from four different precursors: (<b>a</b>) PLA, (<b>b</b>) PLA-GNP, (<b>c</b>) PETG, (<b>d</b>) PETG-C<sub>f</sub>. Blue symbols are the friction coefficient and red lines represent their mean values in each instance of the experiment.</p> Full article ">
12 pages, 4516 KiB  
Article
Preparation of CS-LS/AgNPs Composites and Photocatalytic Degradation of Dyes
by Jiabao Wu, Xinpeng Chen, Aijing Li, Tieling Xing and Guoqiang Chen
Materials 2024, 17(5), 1214; https://doi.org/10.3390/ma17051214 - 6 Mar 2024
Viewed by 1057
Abstract
Synthetic dyes are prone to water pollution during use, jeopardizing biodiversity and human health. This study aimed to investigate the adsorption and photocatalytic assist potential of sodium lignosulfonate (LS) in in situ reduced silver nanoparticles (AgNPs) and chitosan (CS)-loaded silver nanoparticles (CS-LS/AgNPs) as [...] Read more.
Synthetic dyes are prone to water pollution during use, jeopardizing biodiversity and human health. This study aimed to investigate the adsorption and photocatalytic assist potential of sodium lignosulfonate (LS) in in situ reduced silver nanoparticles (AgNPs) and chitosan (CS)-loaded silver nanoparticles (CS-LS/AgNPs) as adsorbents for Rhodamine B (RhB). The AgNPs were synthesized by doping LS on the surface of chitosan for modification. Fourier transform infrared (FT-IR) spectrometry, energy-dispersive spectroscopy (EDS), scanning electron microscopy (SEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) were used to confirm the synthesis of nanomaterials. The adsorption and photocatalytic removal experiments of RhB were carried out under optimal conditions (initial dye concentration of 20 mg/L, adsorbent dosage of 0.02 g, time of 60 min, and UV power of 250 W), and the kinetics of dye degradation was also investigated, which showed that the removal rate of RhB by AgNPs photocatalysis can reach 55%. The results indicated that LS was highly effective as a reducing agent for the large-scale production of metal nanoparticles and can be used for dye decolorization. This work provides a new catalyst for the effective removal of dye from wastewater, and can achieve high-value applications of chitosan and lignin. Full article
(This article belongs to the Special Issue Properties and Applications of Advanced Textile Materials)
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Graphical abstract
Full article ">Figure 1
<p>Structural of (<b>a</b>) Rhodamine B (RhB), (<b>b</b>) Telon Red A2R, and (<b>c</b>) Direct Dark Brown ME.</p> Full article ">Figure 2
<p>Synthesis pathway of CS-LS/AgNPs.</p> Full article ">Figure 3
<p>SEM analysis of CS-LS/AgNPs: (<b>a</b>) CS, (<b>b</b>) CS-LS, (<b>c</b>) CS-LS/AgNPs, (<b>d</b>) EDS analysis, (<b>e</b>–<b>h</b>) elemental mapping of CS-LS/AgNPs, and (<b>i</b>) N<sub>2</sub> sorption isotherm of CS-LS/AgNPs.</p> Full article ">Figure 4
<p>(<b>a</b>) FTIR, (<b>b</b>)XRD, (<b>c</b>) XPS survey of CS-LS/AgNPs, and XPS high-resolution pattern of (<b>d</b>) Ag 3d, (<b>e</b>) C 1s, and (<b>f</b>) S 2p.</p> Full article ">Figure 5
<p>(<b>a</b>–<b>f</b>) Effect of different factors on RhB decoloration in CS-LS/AgNPs, degradation percentage of CS-LS/AgNPs on (<b>g</b>) Telon Red A2R and (<b>h</b>) Direct Dark Brown ME.</p> Full article ">Figure 6
<p>(<b>a</b>,<b>b</b>) Linear fittings of pseudo-first-order and pseudo-second-order kinetics; (<b>c</b>) comparisons of the corresponding apparent rate constants for the degradation of RhB, A2R, and ME.</p> Full article ">Figure 7
<p>Cyclic stability of CS-LS/AgNPs for RhB dye decolorization: (<b>a</b>) Dye decolorisation process per cycle and (<b>b</b>) final degradation percentage on RhB dye after each cycle.</p> Full article ">Figure 8
<p>Effects of scavengers on the photodegradation of RhB over CS-LS/AgNPs.</p> Full article ">Figure 9
<p>Potential mechanism of CS-LS/AgNPs photoadsorption.</p> Full article ">
17 pages, 4395 KiB  
Article
Finite Element Analysis and Fatigue Test of INTEGRA Dental Implant System
by Rafał Zieliński, Sebastian Lipa, Martyna Piechaczek, Jerzy Sowiński, Agata Kołkowska and Wojciech Simka
Materials 2024, 17(5), 1213; https://doi.org/10.3390/ma17051213 - 6 Mar 2024
Cited by 2 | Viewed by 1293
Abstract
The study involved numerical FEA (finite element analysis) of dental implants. Based on this, fatigue tests were conducted according to the PN-EN 14801 standard required for the certification of dental products. Thanks to the research methodology developed by the authors, it was possible [...] Read more.
The study involved numerical FEA (finite element analysis) of dental implants. Based on this, fatigue tests were conducted according to the PN-EN 14801 standard required for the certification of dental products. Thanks to the research methodology developed by the authors, it was possible to conduct a thorough analysis of the impact of external and internal factors such as material, geometry, loading, and assembly of the dental system on the achieved value of fatigue strength limit in the examined object. For this purpose, FEM studies were based on identifying potential sites of fatigue crack initiation in reference to the results of the test conducted on a real model. The actions described in the study helped in the final evaluation of the dental system design process named by the manufacturer as INTEGRA OPTIMA 3.35. The objective of the research was to identify potential sites for fatigue crack initiation in a selected dental system built on the INTEGRA OPTIMA 3.35 set. The material used in the research was titanium grade 4. A map of reduced von Mises stresses was used to search for potential fatigue crack areas. The research [loading] was conducted on two mutually perpendicular planes positioned in such a way that the edge intersecting the planes coincided with the axis of the system. The research indicated that the connecting screw showed the least sensitivity (stress change) to the change in the loading plane, while the value of preload has a significant impact on the achieved fatigue strength of the system. In contrast, the endosteal implant (root) and the prosthetic connector showed the greatest sensitivity to the change in the loading plane. The method of mounting [securing] the endosteal implant using a holder, despite meeting the standards, may contribute to generating excessive stress concentration in the threaded part. Observation of the prosthetic connector in the Optima 3.35 system, cyclically loaded with a force of F ≈ 300 N in the area of the upper hexagonal peg, revealed a fatigue fracture. The observed change in stress peak in the dental connector for two different force application surfaces shows that the positioning of the dental system (setting of the socket in relation to the force action plane) is significantly decisive in estimating the limited fatigue strength. Full article
(This article belongs to the Special Issue State-of-the-Art Biomaterials Science and Bioengineering in Poland)
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<p>Geometrical model of the OPTIMA 3.35 dental set.</p> Full article ">Figure 2
<p>Contact condition screw—implant (thread domain)—friction coefficient in the thread µ = 0.4.</p> Full article ">Figure 3
<p>(<b>a</b>) FEA mesh of the entire set with division into elements and (<b>b</b>) boundary conditions—point of force application.</p> Full article ">Figure 4
<p>The tested system OPTIMA 3.35 on a brass base.</p> Full article ">Figure 5
<p>(<b>a</b>) Research Workstation: Dora 14801. (<b>b</b>) The most favorable mounting of the system to the holder at the testing station met the guidelines of PN-EN 14801.</p> Full article ">Figure 6
<p>(<b>a</b>) Map of reduced stresses of the endosteal implant for T = 0.08. (<b>b</b>) Map of reduced stresses of the connecting screw joining the endosteal implant with the prosthetic connector for T = 0.08. (<b>c</b>) Map of reduced stresses of the prosthetic connector for T = 0.08. Arrow shows the highest stresses.</p> Full article ">Figure 7
<p>Geometry of the hexagonal peg and marked [in red] planes of load action.</p> Full article ">Figure 8
<p>Boundary conditions for the OPTIMA 3.35 dental set; loading in the X-Z plane.</p> Full article ">Figure 9
<p>Number of stress cycles (S-N curve) or Wöhler curve for the Optima 3.35 dental system (material: titanium).</p> Full article ">Figure 10
<p>Identification of the most stressed areas in the connector and SEM microscope study results; visible: fatigue focus observed in the upper area of the fracture—corner, perifocal area, primary displacements, and fatigue lines. Load force F ≈ 300 N.</p> Full article ">Figure 11
<p>SEM Image (30×) of the breakthrough in the area of the connecting screw under the load force F ≈ 300 N (plastic fracture).</p> Full article ">Figure 12
<p>Macro photo of a broken hexagonal peg of the prosthetic connector.</p> Full article ">
14 pages, 1560 KiB  
Article
Biocomposites Based on Wheat Flour with Urea-Based Eutectic Plasticizer and Spent Coffee Grounds: Preparation, Physicochemical Characterization, and Study of Their Influence on Plant Growth
by Magdalena Zdanowicz, Marta Rokosa, Magdalena Pieczykolan, Adrian Krzysztof Antosik and Katarzyna Skórczewska
Materials 2024, 17(5), 1212; https://doi.org/10.3390/ma17051212 - 6 Mar 2024
Cited by 1 | Viewed by 1091
Abstract
In this study, we conducted the first plasticization of wheat flour (WF) with the addition of choline chloride:urea (1:5 molar ratio) eutectic mixture as a plasticizer and spent coffee grounds (cf) as a filler. Thermoplastic wheat flour (TPWF) films were obtained via twin-screw [...] Read more.
In this study, we conducted the first plasticization of wheat flour (WF) with the addition of choline chloride:urea (1:5 molar ratio) eutectic mixture as a plasticizer and spent coffee grounds (cf) as a filler. Thermoplastic wheat flour (TPWF) films were obtained via twin-screw extrusion and then thermocompression. Their physicochemical characterization included mechanical tests, dynamic mechanical thermal analysis (DMTA), and sorption tests. XRD analysis revealed that the eutectic plasticizer led to a high degree of WF amorphization, which affected the physicochemical properties of TPWF. The results indicated that it was easy for the TPWF biocomposites to undergo thermocompression even with a high amount of the filler (20 pph per flour). The addition of the cf into TPWF led to an increase in tensile strength and a decrease in the swelling degree of the biocomposites. Biodegradation tests in soil revealed that the materials wholly degraded within 11 weeks. Moreover, a study of cultivated plants indicated that the biocomposites did not exhibit a toxic influence on the model rowing plant. Full article
(This article belongs to the Special Issue Food Industry Wastes and By-Products in Polymer Technology)
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<p>Extruded pellets (<b>left</b>) of TPWF/CCU and TPWF/CCU/cf (<b>right</b>).</p> Full article ">Figure 2
<p>DMTA results for TPWF films. Storage modulus (E′) for TPS with CCU (<b>up</b>) and tan δ (<b>down</b>).</p> Full article ">Figure 3
<p>XRD pattern for native wheat flour (WF), spent coffee grounds (cf), thermoplasticized TPWF with CCU 1:5 and its biocomposites (TPWF/CCU/cf and TPWF/CCU+cf).</p> Full article ">Figure 4
<p>TGA results for native wheat flour (WF), thermoplasticized WF with DES (TPWF/CCU), and TPWF with spent coffee grounds (TPWF/CCU/cf and TPWF/CCU+cf).</p> Full article ">Figure 5
<p>Mass loss curves for the biodegradation test in the soil of TPWF films and their biocomposites.</p> Full article ">
13 pages, 3425 KiB  
Article
Design of an Optical Device Based on Kirigami Approach
by Marta De Giorgi
Materials 2024, 17(5), 1211; https://doi.org/10.3390/ma17051211 - 6 Mar 2024
Viewed by 705
Abstract
The aim of this work was to design a kirigami-based metamaterial with optical properties. This idea came from the necessity of a study that can improve common camouflage techniques to yield a product that is cheap, light, and easy to manufacture and assemble. [...] Read more.
The aim of this work was to design a kirigami-based metamaterial with optical properties. This idea came from the necessity of a study that can improve common camouflage techniques to yield a product that is cheap, light, and easy to manufacture and assemble. The author investigated the possibility of exploiting a rotation to achieve transparency and color changing. One of the most important examples of a kirigami structure is a geometry based on rotating squares, which is a one-degree-of-freedom mechanism. In this study, light polarization and birefringence were exploited to obtain transparency and color-changing properties using two polarizers and common cellophane tape. These elements were assembled with a rotating-square structure that allowed the rotation of a polarizer placed on the structure with respect to a fixed polarizer equipped with cellophane layers. Full article
(This article belongs to the Special Issue The 15th Anniversary of Materials—Recent Advances in Advanced Materials Characterization)
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<p>Rotating-square mechanism [<a href="#B12-materials-17-01211" class="html-bibr">12</a>].</p> Full article ">Figure 2
<p>Example of experimental setup for observing birefringence [<a href="#B20-materials-17-01211" class="html-bibr">20</a>].</p> Full article ">Figure 3
<p>Characterization of a polarizer. Transparency vs. angle between the polarizers. Experimental data (orange circles) vs. mathematical model output (blue line).</p> Full article ">Figure 4
<p>Color output from cellotape between two polarizers at 0° (<b>a</b>), 45° (<b>b</b>), and at 90° (<b>c</b>).</p> Full article ">Figure 5
<p>Measurement of cellophane tape thickness.</p> Full article ">Figure 6
<p>Validation of the mathematical model: intensity of light vs. cosine of the angle between polarizers. <b>Left column</b>: results from [<a href="#B20-materials-17-01211" class="html-bibr">20</a>]. <b>Right column</b>: output obtained from the developed mathematical model for different orientations of tape (10°, 30°, 45°).</p> Full article ">Figure 7
<p>(<b>a</b>) Model output for a specific angle between polarizers: Normalized output vs. wavelength. The orange line represents the threshold imposed for defining which of the wavelengths is dominant. (<b>b</b>) Hitten circle. (<b>c</b>) Overlapping of patches—mixing color.</p> Full article ">Figure 8
<p>Results from color prediction: (<b>a</b>) an example with 1 layer of tape; (<b>b</b>–<b>d</b>) examples with 2 layers of tape example at different angles: &lt;10°, 45°&gt;, &lt;30°, 60°&gt;, &lt;67°, 32°&gt;, respectively.</p> Full article ">Figure 9
<p>Final assembly of acrylic rotating square 10 mm thick: open (<b>a</b>) and closed (<b>b</b>) position; PDMS rotating squares 10 mm thick: 3D-printed mold parts (<b>c</b>,<b>d</b>) and demolded structure (<b>e</b>).</p> Full article ">Figure 10
<p>Experimental setup and experimental results: 0% strain (open); transitory state; 100% strain (closed).</p> Full article ">
12 pages, 5207 KiB  
Article
Deformation Behavior of an Extruded 7075 Aluminum Alloy at Elevated Temperatures
by Tuo Ye, Erli Xia, Sawei Qiu, Jie Liu, Huanyu Yue, Jian Tang and Yuanzhi Wu
Materials 2024, 17(5), 1210; https://doi.org/10.3390/ma17051210 - 6 Mar 2024
Cited by 3 | Viewed by 997
Abstract
Hot compression tests were conducted to explore the deformation behavior of an extruded 7075 aluminum alloy bar at elevated temperatures. Specimens with 0°, 45°, and 90° angles along the extrusion direction were prepared. The compression temperatures were 300 and 400 °C, and the [...] Read more.
Hot compression tests were conducted to explore the deformation behavior of an extruded 7075 aluminum alloy bar at elevated temperatures. Specimens with 0°, 45°, and 90° angles along the extrusion direction were prepared. The compression temperatures were 300 and 400 °C, and the strain rates ranged from 0.001 to 0.1 s−1. The corresponding microstructures were characterized via OM and TEM, and the macroscopic texture was tested using XRD. The results indicated that the strength of the 7075 alloy decreases with higher compression temperatures and is in a proportional relationship with respect to the strain rate. During high-temperature compression, it is easier to stimulate atomic diffusion in the matrix, which can improve thermal activation abilities and facilitate dynamic recovery and dynamic recrystallization. In addition, the coarsening of precipitates also contributed to dynamic softening. When compressed at 300 °C, the stress levels of the 0° specimens ranked first, and those for the 45° specimens were the lowest. When compressed at 400 °C, the flow stresses of the specimens along three directions were comparable. The anisotropic mechanical behavior can be explained by the fiber grains and brass {011} <211> texture component. However, higher temperature deformation leads to recrystallization, which can weaken the anisotropy of mechanical properties. Full article
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<p>The diagram of the sample location in the original 7075 aluminum alloy bar.</p> Full article ">Figure 2
<p>Diagram of the hot compression processes and parameters.</p> Full article ">Figure 3
<p>Microstructure and XRD observation area of the sample.</p> Full article ">Figure 4
<p>The initial microstructure of 7075 aluminum alloy: (<b>a</b>) optical microscope (OM) observation and (<b>b</b>) transmission electron microscope (TEM) observation.</p> Full article ">Figure 5
<p>True stress–strain curves of 7075 alloy bar with different compression conditions: (<b>a</b>) 0°, 300 °C; (<b>b</b>) 45°, 300 °C; (<b>c</b>) 90°, 300 °C; (<b>d</b>) 0°, 400 °C; (<b>e</b>) 45°, 400 °C; (<b>f</b>) 90°, 400 °C.</p> Full article ">Figure 6
<p>OM of 7075 alloys compressed using different conditions: (<b>a</b>) 0°, 300 °C, 0.1 s<sup>−1</sup>; (<b>b</b>) 0°, 400 °C, 0.1 s<sup>−1</sup>; (<b>c</b>) 0°, 400 °C, 0.01 s<sup>−1</sup>; (<b>d</b>) 0°, 400 °C, 0.001 s<sup>−1</sup>.</p> Full article ">Figure 7
<p>TEM images of 7075 alloy samples after deformation under different conditions: (<b>a</b>) 0°, 300 °C, 0.1 s<sup>−1</sup>; (<b>b</b>) 0°, 300 °C, 0.1 s<sup>−1</sup>; (<b>c</b>) 45°, 300 °C, 0.1 s<sup>−1</sup>; (<b>d</b>) 90°, 300 °C, 0.1 s<sup>−1</sup>; (<b>e</b>) 0°, 400 °C, 0.1 s<sup>−1</sup>; (<b>f</b>) 0°, 400 °C, 0.1 s<sup>−1</sup>; (<b>g</b>) 45°, 400 °C, 0.1 s<sup>−1</sup>; (<b>h</b>) 90°, 400 °C, 0.1 s<sup>−1</sup>; (<b>i</b>) 90°, 400 °C, 0.01 s<sup>−1</sup>; (<b>j</b>) 0°, 400 °C, 0.01 s<sup>−1</sup>; (<b>k</b>) 0°, 400 °C, 0.001 s<sup>−1</sup>; (<b>l</b>) 0°, 400 °C, 0.001 s<sup>−1</sup>.</p> Full article ">Figure 8
<p>Original grain structure of the extruded 7075 aluminum alloy.</p> Full article ">Figure 9
<p>XRD-derived ODF sections of macrotextures measured in the extruded 7075 aluminum alloy bar.</p> Full article ">
14 pages, 4205 KiB  
Article
In Situ Preparation of rGO-Cement Using Thermal Reduction Method and Performance Study
by Jie Yao, Ao Guan, Wenqiang Ruan and Ying Ma
Materials 2024, 17(5), 1209; https://doi.org/10.3390/ma17051209 - 6 Mar 2024
Viewed by 1003
Abstract
In this study, the combination of freeze-drying and high-temperature thermal reduction methods was employed to in situ prepare reduced graphene oxide (rGO)-Cement based on graphene oxide (GO)-Cement. The electrical conductivity and mechanical properties of the rGO-Cement were investigated. Microscopic analysis methods such as [...] Read more.
In this study, the combination of freeze-drying and high-temperature thermal reduction methods was employed to in situ prepare reduced graphene oxide (rGO)-Cement based on graphene oxide (GO)-Cement. The electrical conductivity and mechanical properties of the rGO-Cement were investigated. Microscopic analysis methods such as Raman spectra, X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM) were used to confirm the successful transformation of GO-Cement to rGO-Cement. The research results demonstrated that with an increase in rGO content, the electrical resistivity of the rGO-Cement decreased first and then increased, reaching a percolation threshold at the dosage of 0.7 wt.%. The compressive strength and flexural strength of the rGO-Cement increased first and then decreased. The optimal dosage of rGO was 0.7%. The in situ preparation of rGO-Cement using the thermal reduction method holds a great potential for various applications, providing new ideas and methods for the modification and enhancement of cement materials. Full article
(This article belongs to the Section Carbon Materials)
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<p>XRD pattern of cement.</p> Full article ">Figure 2
<p>Preparation of rGO-Cement powder and its pure slurry.</p> Full article ">Figure 3
<p>(<b>a</b>) Schematic diagram of resistivity test sample, (<b>b</b>) schematic diagram of voltage regulator power supply, and (<b>c</b>) schematic diagram of resistivity test principle.</p> Full article ">Figure 4
<p>Raman spectra of GO-Cement particles and rGO-Cement particles at 0.50 wt.% GO.</p> Full article ">Figure 5
<p>XPS spectra of 0.50 wt.% GO-Cement and 0.50 wt.% rGO-Cement.</p> Full article ">Figure 6
<p>C1s spectra of (<b>a</b>) 0.50 wt.% GO-Cement and (<b>b</b>) 0.50 wt.% rGO-Cement.</p> Full article ">Figure 7
<p>SEM images of (<b>a</b>) 0.50 wt.% GO-Cement and (<b>b</b>) 0.50 wt.% rGO-Cement.</p> Full article ">Figure 8
<p>Effects of GO-doping amounts on the resistivity of rGO-Cement matrix composite.</p> Full article ">Figure 9
<p>Mechanical properties of cement with different amounts of rGO: (<b>a</b>) the compressive strength and (<b>b</b>) the flexural strength.</p> Full article ">Figure 10
<p>XRD patterns of cement at 28d: (<b>a</b>) 0.50 wt.% GO-Cement and (<b>b</b>) 0.50 wt.% rGO-Cement.</p> Full article ">
26 pages, 5515 KiB  
Article
Marble Powder as a Soil Stabilizer: An Experimental Investigation of the Geotechnical Properties and Unconfined Compressive Strength Analysis
by Ibrahim Haruna Umar and Hang Lin
Materials 2024, 17(5), 1208; https://doi.org/10.3390/ma17051208 - 5 Mar 2024
Cited by 6 | Viewed by 1549
Abstract
Fine-grained soils present engineering challenges. Stabilization with marble powder has shown promise for improving engineering properties. Understanding the temporal evolution of Unconfined Compressive Strength (UCS) and geotechnical properties in stabilized soils could aid strength assessment. This study investigates the stabilization of fine-grained clayey [...] Read more.
Fine-grained soils present engineering challenges. Stabilization with marble powder has shown promise for improving engineering properties. Understanding the temporal evolution of Unconfined Compressive Strength (UCS) and geotechnical properties in stabilized soils could aid strength assessment. This study investigates the stabilization of fine-grained clayey soils using waste marble powder as an alternative binder. Laboratory experiments were conducted to evaluate the geotechnical properties of soil–marble powder mixtures, including Atterberg’s limits, compaction characteristics, California Bearing Ratio (CBR), Indirect Tensile Strength (ITS), and Unconfined Compressive Strength (UCS). The effects of various factors, such as curing time, molding water content, and composition ratios, on UCS, were analyzed using Exploratory Data Analysis (EDA) techniques, including histograms, box plots, and statistical modeling. The results show that the CBR increased from 10.43 to 22.94% for unsoaked and 4.68 to 12.46% for soaked conditions with 60% marble powder, ITS rose from 100 to 208 kN/m2 with 60–75% marble powder, and UCS rose from 170 to 661 kN/m2 after 28 days of curing, molding water content (optimum at 22.5%), and composition ratios (optimum at 60% marble powder). Complex modeling yielded R2 (0.954) and RMSE (29.82 kN/m2) between predicted and experimental values. This study demonstrates the potential of utilizing waste marble powder as a sustainable and cost-effective binder for soil stabilization, transforming weak soils into viable construction materials. Full article
(This article belongs to the Special Issue Reliability Modeling of Complex Systems in Materials and Devices)
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<p>Particle size distribution curve.</p> Full article ">Figure 2
<p>UCS machine.</p> Full article ">Figure 3
<p>Component of boxplot.</p> Full article ">Figure 4
<p>Atterberg’s limits.</p> Full article ">Figure 5
<p>Compaction characteristics.</p> Full article ">Figure 6
<p>California Bearing Ratio (CBR).</p> Full article ">Figure 7
<p>Indirect Tensile Strength (ITS).</p> Full article ">Figure 8
<p>Distribution of Unconfined Compressive Strength (UCS) values for the fine-grained soil samples stabilized with marble powder.</p> Full article ">Figure 9
<p>UCS values across different curing times for the fine-grained soil samples stabilized with marble powder. The bar colors represent the curing time of the mixtures: pink for 0 days, blue for 3 days, green for 7 days, yellow for 14 days, and purple for 28 days.</p> Full article ">Figure 10
<p>UCS values across different molding water contents for the fine-grained soil samples stabilized with marble powder. The bar green shades represent the percentage of water content added to the soil mixtures: lighter shades for 20%, medium shades for 22.5% and darker shades for 24.5%.</p> Full article ">Figure 11
<p>UCS values across different composition ratios for the fine-grained soil stabilized with marble powder. The bar colors represent the percentage of marble powder added to the soil mixtures: pink for 0%, brown for 15%, green for 30%, cyan for 45%, blue for 60%, and purple for 75%.</p> Full article ">Figure 12
<p>Actual vs. predicted UCS values.</p> Full article ">Figure 13
<p>Normalizing feature importances for model prediction improvement. The bar colors represent the percentage of parameters importance: pink for soil, green for marble, cyan for curing time, and purple for molding water content.</p> Full article ">
20 pages, 35324 KiB  
Article
A Stochastic Dynamics Method for Time-Varying Damping Depending on Temperature/Frequency for Several Alloy Materials
by Wenjun Huang, Guorui Yu, Wentao Xu and Ruchuan Zhou
Materials 2024, 17(5), 1207; https://doi.org/10.3390/ma17051207 - 5 Mar 2024
Cited by 1 | Viewed by 736
Abstract
In the field of aerospace and advanced equipment manufacturing, accurate response analysis has been paid more attention, requiring a more comprehensive study of the variation of mechanical parameters with the service environment. The damping variation characteristics of 304 aluminum alloy, Sa564 high-strength alloy, [...] Read more.
In the field of aerospace and advanced equipment manufacturing, accurate response analysis has been paid more attention, requiring a more comprehensive study of the variation of mechanical parameters with the service environment. The damping variation characteristics of 304 aluminum alloy, Sa564 high-strength alloy, GW63K magnesium alloy, and Q235 steel were investigated in this paper, which plays a significant role in the dynamic responses of structures. Variable damping ratios were revealed by the damping tests based on a dynamic mechanical analysis (DMA). The numerical method of temperature/frequency-dependent damping parameters in stochastic dynamics was focused on. With a large variation in the damping ratio, a numerical constitutive relation for temperature-dependent damping was proposed, and an efficient stochastic dynamics method was derived to analyze the responses of structures based on the pseudo excitation method (PEM) and variable damping theory. The computational accuracy and validity of the proposed method are confirmed during the vibration tests and numerical analysis. Based on the comparison results of the two damping models and the experiments on GW63K alloy, we proved that the proposed method is more accurate to the real response of the actual engineering structure. The differences in dynamic responses between the constant damping and experiments are significant, and more attention should be paid to the numerical method of stochastic dynamic response of variable damping materials in the aviation and aerospace fields and high-temperature environments. Full article
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<p>DMA-800 and clamping method.</p> Full article ">Figure 2
<p>Test specimens.</p> Full article ">Figure 3
<p>Calibration results for alloy damping test.</p> Full article ">Figure 4
<p>Microscopic images of 304 alloy.</p> Full article ">Figure 5
<p>Temperature-dependent damping of Sa564 alloy.</p> Full article ">Figure 6
<p>Temperature-dependent damping of Q235 alloy.</p> Full article ">Figure 7
<p>Temperature-dependent damping of 304 alloy.</p> Full article ">Figure 8
<p>Temperature-dependent damping of GW63K alloy.</p> Full article ">Figure 9
<p>Numerical constitutive relation of temperature-dependent damping of GW63K alloy.</p> Full article ">Figure 10
<p>Test model.</p> Full article ">Figure 11
<p>Acceleration responses envelops comparison of GW63K magnesium alloy specimens.</p> Full article ">Figure 12
<p>Velocity responses envelops comparison of GW63K magnesium alloy specimens.</p> Full article ">Figure 13
<p>Displacement responses envelops comparison of GW63K magnesium alloy specimens.</p> Full article ">Figure 14
<p>Three-dimensional model of magnesium alloy support.</p> Full article ">Figure 15
<p>Comparison of displacement response envelopes.</p> Full article ">Figure 16
<p>Comparison of velocity response envelopes.</p> Full article ">Figure 17
<p>Comparison of acceleration response envelopes.</p> Full article ">Figure 18
<p>Displacement responses for the magnesium alloy support (constant damping).</p> Full article ">Figure 19
<p>Displacement responses (middle section).</p> Full article ">Figure 20
<p>Displacement responses (end section).</p> Full article ">Figure 21
<p>Shaking table experiment for bearing.</p> Full article ">Figure 22
<p>Three-dimensional numerical model of bearing.</p> Full article ">Figure 23
<p>Frequency-dependent damping behavior in GW63K alloy.</p> Full article ">Figure 24
<p>The excitation signal in time domain of vibration test bench.</p> Full article ">Figure 25
<p>Acceleration response comparison of magnesium alloy bearing.</p> Full article ">
11 pages, 2344 KiB  
Article
C60- and CdS-Co-Modified Nano-Titanium Dioxide for Highly Efficient Photocatalysis and Hydrogen Production
by Meifang Zhang, Xiangfei Liang, Yang Gao and Yi Liu
Materials 2024, 17(5), 1206; https://doi.org/10.3390/ma17051206 - 5 Mar 2024
Cited by 1 | Viewed by 1102
Abstract
The inherent properties of TiO2, including a wide band gap and restricted spectral response range, hinder its commercial application and its ability to harness only 2–3% of solar energy. To address these challenges and unlock TiO2’s full potential in [...] Read more.
The inherent properties of TiO2, including a wide band gap and restricted spectral response range, hinder its commercial application and its ability to harness only 2–3% of solar energy. To address these challenges and unlock TiO2’s full potential in photocatalysis, C60- and CdS-co-modified nano-titanium dioxide has been adopted in this work to reduce the band gap, extend the absorption wavelength, and control photogenerated carrier recombination, thereby enhancing TiO2’s light-energy-harnessing capabilities and hydrogen evolution capacity. Using the sol-gel method, we successfully synthesized CdS-C60/TiO2 composite nanomaterials, harnessing the unique strengths of CdS and C60. The results showed a remarkable average yield of 34.025 μmol/h for TiO2 co-modified with CdS and C60, representing a substantial 17-fold increase compared to pure CdS. Simultaneously, the average hydrogen generation of C60-modified CdS surged to 5.648 μmol/h, a notable two-fold improvement over pure CdS. This work opens up a new avenue for the substantial improvement of both the photocatalytic degradation efficiency and hydrogen evolution capacity, offering promise of a brighter future in photocatalysis research. Full article
(This article belongs to the Special Issue Novel Nanomaterials for Energy Storage and Catalysis)
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<p>(<b>a</b>) XRD patterns and (<b>b</b>) UV–Vis diffuse reflectance spectra of P25, CdS, CdS-C<sub>60</sub>, CdS-TiO<sub>2</sub>, and CdS-C<sub>60</sub>/TiO<sub>2</sub>. Energy-Dispersive X-ray (EDX) elemental microanalysis of (<b>c</b>) CdS, (<b>d</b>) CdS-TiO<sub>2</sub>, (<b>e</b>) CdS-C<sub>60</sub>/TiO<sub>2</sub>.</p> Full article ">Figure 2
<p>(<b>a</b>) FT–IR spectra of P25, pristine TiO<sub>2</sub>, CdS, (<b>b</b>) CdS-C<sub>60</sub>, CdS-TiO<sub>2</sub>, and CdS-C<sub>60</sub>-TiO<sub>2</sub>.</p> Full article ">Figure 3
<p>Spectrum of adsorption of MG solution in the presence of (<b>a</b>) CdS; (<b>b</b>) CdS-TiO<sub>2</sub>; (<b>c</b>) CdS-C<sub>60</sub>; and (<b>d</b>) CdS-C<sub>60</sub>/TiO<sub>2</sub> under different irradiation times when exposed to halogen tungsten lamp. For A–G, each absorbance spectrum was recorded over a 5 min interval; for G–J, each absorbance spectrum was recorded over a 10 min interval; for J–L, each absorbance spectrum was recorded over a 30 min interval with visible light illumination. (<b>e</b>) Absorbance variations as a function of irradiation time (<b>f</b>), ln (c<sub>0</sub>/c), and the linear of control for P25, CdS, CdS-C<sub>60</sub>, CdS-TiO<sub>2</sub>, CdS-C<sub>60</sub>/TiO<sub>2</sub> in MG deterioration after 120 min exposure to radiation at ambient temperature. [MG] = 4 mg/L; [P25] (CdS, CdS-C<sub>60</sub>, CdS-TiO<sub>2</sub>, CdS-C<sub>60</sub>/TiO<sub>2</sub>) = 0.6 g/L.</p> Full article ">Figure 4
<p>(<b>a</b>) Several kinds of hydrogen production with a time change map; (<b>b</b>) different catalysts per hour of hydrogen production.</p> Full article ">Figure 5
<p>The photodegradation mechanism schematic for CdS-C<sub>60</sub>-TiO<sub>2</sub>.</p> Full article ">
18 pages, 3586 KiB  
Article
The Impact of Marangoni and Buoyancy Convections on Flow and Segregation Patterns during the Solidification of Fe-0.82wt%C Steel
by Ibrahim Sari, Menghuai Wu, Mahmoud Ahmadein, Sabbah Ataya, Nashmi Alrasheedi and Abdellah Kharicha
Materials 2024, 17(5), 1205; https://doi.org/10.3390/ma17051205 - 5 Mar 2024
Cited by 1 | Viewed by 912
Abstract
Due to the high computational costs of the Eulerian multiphase model, which solves the conservation equations for each considered phase, a two-phase mixture model is proposed to reduce these costs in the current study. Only one single equation for each the momentum and [...] Read more.
Due to the high computational costs of the Eulerian multiphase model, which solves the conservation equations for each considered phase, a two-phase mixture model is proposed to reduce these costs in the current study. Only one single equation for each the momentum and enthalpy equations has to be solved for the mixture phase. The Navier–Stokes and energy equations were solved using the 3D finite volume method. The model was used to simulate the liquid–solid phase transformation of a Fe-0.82wt%C steel alloy under the effect of both thermocapillary and buoyancy convections. The alloy was cooled in a rectangular ingot (100 × 100 × 10 mm3) from the bottom cold surface to the top hot free surface by applying a heat transfer coefficient of h = 600 W/m2/K, which allows for heat exchange with the outer medium. The purpose of this work is to study the effect of the surface tension on the flow and segregation patterns. The results before solidification show that Marangoni flow was formed at the free surface of the molten alloy, extending into the liquid depth and creating polygonized hexagonal patterns. The size and the number of these hexagons were found to be dependent on the Marangoni number, where the number of convective cells increases with the increase in the Marangoni number. During solidification, the solid front grew in a concave morphology, as the centers of the cells were hotter; a macro-segregation pattern with hexagonal cells was formed, which was analogous to the hexagonal flow cells generated by the Marangoni effect. After full solidification, the segregation was found to be in perfect hexagonal shapes with a strong compositional variation at the free surface. This study illuminates the crucial role of surface-tension-driven Marangoni flow in producing hexagonal patterns before and during the solidification process and provides valuable insights into the complex interplay between the Marangoni flow, buoyancy convection, and solidification phenomena. Full article
(This article belongs to the Special Issue Advances in Multicomponent Alloy Design, Simulation and Properties)
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Graphical abstract

Graphical abstract
Full article ">Figure 1
<p>Sketch of the simulated domain of the solidification ingot.</p> Full article ">Figure 2
<p>Velocity field for different configurations of geometry and thermal gradient. The thermal gradient and the ingot thickness for cases (<b>a</b>–<b>c</b>) are DT = 65, 100, 65 K and e = 10, 1.25, and 1.25 mm, respectively.</p> Full article ">Figure 3
<p>Hexagonal patterns produced by Marangoni effect at the free top surface: (<b>a</b>) taken before the solidification; (<b>b</b>) zoomed-in view of one hexagon inside the dashed square; (<b>c</b>) velocity vector and colored magnitude level inside one hexagon at the vertical cut plane. <math display="inline"><semantics> <mrow> <mi mathvariant="normal">M</mi> <mi mathvariant="normal">a</mi> </mrow> </semantics></math> = 1186.8 and <math display="inline"><semantics> <mrow> <mi mathvariant="normal">R</mi> <mi mathvariant="normal">a</mi> </mrow> </semantics></math> = 2615.5.</p> Full article ">Figure 4
<p>Velocity (<b>left</b> column) and temperature (<b>right</b> column) fields at the free surface and e = 0.4 mm horizontally cut plane (<span class="html-italic">xz</span> plane).</p> Full article ">Figure 5
<p>The calculated solid fraction after t = 4863 s at (<b>a</b>) a vertical cut plane (<span class="html-italic">yz</span> plane) and (<b>c</b>) a horizontally cut plane (<span class="html-italic">xz</span> plane). Also, see (<b>b</b>) for the mixture concentration at the liquid–solid interface of horizontally cut plane (<span class="html-italic">xz</span> plane).</p> Full article ">Figure 6
<p>Mixture concentration (<b>left</b>) and solid fraction (<b>right</b>), presented at the level of the free surface.</p> Full article ">Figure 7
<p>Three-dimensional zoomed-in view of one hexagonal cell showing the segregation and velocity vectors at the free surface and inside the mushy zone.</p> Full article ">Figure 8
<p>The contour of mixture concentration at the end of solidification of the Fe-0.82wt% ingot at various cut levels: 0.1 mm (<b>left</b>), 5 mm (<b>middle</b>); and 9 mm (<b>right</b>).</p> Full article ">Figure 9
<p>Segregation difference versus the sample (ingot) height at 0.1, 2, 5, 7, and 9 mm cut planes from the bottom to the top, respectively.</p> Full article ">Figure 10
<p>Normalized macro-segregation along the black line presented on the left picture in one hexagon obtained in the static case at e = 5 mm after full solidification.</p> Full article ">
21 pages, 4304 KiB  
Article
A 3D Meso-Scale Model and Numerical Uniaxial Compression Tests on Concrete with the Consideration of the Friction Effect
by Jiawei Wang, Xinlu Yu, Yingqian Fu and Gangyi Zhou
Materials 2024, 17(5), 1204; https://doi.org/10.3390/ma17051204 - 5 Mar 2024
Cited by 1 | Viewed by 889
Abstract
Achieving the real mechanical performance of construction materials is significantly important for the design and engineering of structures. However, previous researchers have shown that contact friction performs an important role in the results of uniaxial compression tests. Strong discreteness generally appears in concrete-like [...] Read more.
Achieving the real mechanical performance of construction materials is significantly important for the design and engineering of structures. However, previous researchers have shown that contact friction performs an important role in the results of uniaxial compression tests. Strong discreteness generally appears in concrete-like construction materials due to the random distribution of the components. A numerical meso-scale finite-element (FE) method provides the possibility of generating an ideal material with the same component percentages and distribution. Thus, a well-designed meso-FE model was employed to investigate the effect of friction on the mechanical behavior and failure characteristics of concrete under uniaxial compression loading. The results showed that the mechanical behavior and failure profiles of the simulation matched well with the experimental results. Based on this model, the effect of friction was determined by changing the contact friction coefficient from 0.0 to 0.7. It was found that frictional contact had a slight influence on the elastic compressive mechanical behavior of concrete. However, the nonlinear hardening behavior of the stress–strain curves showed a fairly strong relationship with the frictional contact. The final failure profiles of the experiments showed a “sand-glass” shape that might be expected to result from the contact friction. Thus, the numerical meso-scale FE model showed that contact friction had a significant influence on both the mechanical performance and the failure profiles of concrete. Full article
(This article belongs to the Special Issue Multiscale Modeling and Simulation of Cementitious Materials Behavior)
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Figure 1
<p>Experimental setups of uniaxial compression using an MTS machine (<b>a</b>) to load the specimens with speckles (<b>b</b>) spread on the surface of cubes calculated using the DIC method (<b>c</b>).</p> Full article ">Figure 2
<p>Several typical coarse aggregates used in this model.</p> Full article ">Figure 3
<p>Total grading passing percentage of aggregates used in this model.</p> Full article ">Figure 4
<p>Insertion of aggregates in the cube with three different grading sizes. (<b>a</b>) Grading from 9.50 mm to 12.7 mm, (<b>b</b>) grading from 4.75 mm to 12.7 mm, and (<b>c</b>) grading from 2.36 mm to 12.7 mm.</p> Full article ">Figure 5
<p>The three-phase structure of the concrete employed in the meso-scale FE model. (<b>a</b>) Macro-scale model of the cube, (<b>b</b>) three phases of Zone A, and (<b>c</b>) elements of Zone B in the three-phase model.</p> Full article ">Figure 6
<p>The response of concrete to uniaxial loading in the CDP model. (<b>a</b>) Tensile cracking and (<b>b</b>) compressive crushing.</p> Full article ">Figure 7
<p>Exponential damage evolution of ITZ layer.</p> Full article ">Figure 8
<p>The mesh size of (<b>a</b>) 2 mm, (<b>b</b>) 1 mm, (<b>c</b>) 0.5 mm, and (<b>d</b>) 0.1 mm.</p> Full article ">Figure 9
<p>The engineering stress–strain curves with different element sizes.</p> Full article ">Figure 10
<p>The mesh convergence using four different mesh configurations with an average element size of 0.1 mm–2 mm.</p> Full article ">Figure 11
<p>The boundary and loading conditions with the consideration of the contacting friction.</p> Full article ">Figure 12
<p>The stress–strain curves obtained from the experimental and numerical results.</p> Full article ">Figure 13
<p>The final profiles of specimens showed a “sand-glass” (indicated as the red line) shape in both numerical and experimental results. (<b>a</b>) Final profiles of the experiment. (<b>b</b>) Final profiles of the meso-FE model.</p> Full article ">Figure 14
<p>The first cracking profile that led to the nonlinear response of the stress–strain curves. (<b>a</b>) Compressive strain = 0.001 in the simulation. (<b>b</b>) Compressive strain 0.001 in the experiment.</p> Full article ">Figure 15
<p>The evolution of the maximum principal stress (<b>a1</b>–<b>a5</b>), maximum principal strain (<b>b1</b>–<b>b5</b>), and damage maps (<b>c1</b>–<b>c5</b>) under the condition of uniaxial compression, where the numbers 1 to 5 are related to the points of the macro-stress–strain curve in (<b>d</b>).</p> Full article ">Figure 16
<p>The compressive stress–strain curves of different contacting friction properties with the change of friction coefficients ranging from 0.0 to 0.7.</p> Full article ">Figure 17
<p>Characteristic parameters with changes in friction coefficients ranging from 0.0 to 0.7: elastic limit, <math display="inline"><semantics> <msub> <mi>σ</mi> <mi>E</mi> </msub> </semantics></math>, strength, <math display="inline"><semantics> <msub> <mi>σ</mi> <mi>S</mi> </msub> </semantics></math> (<b>a</b>), normalized stress or strain increment (<b>b</b>), <math display="inline"><semantics> <mrow> <mo>Δ</mo> <mi>σ</mi> </mrow> </semantics></math> or <math display="inline"><semantics> <mrow> <mo>Δ</mo> <mi>ε</mi> </mrow> </semantics></math> (<b>c</b>), and average elastic modulus, <span class="html-italic">E</span> (<b>d</b>).</p> Full article ">Figure 18
<p>The final failure profiles with different friction coefficients shown in the damage cloud map.</p> Full article ">
20 pages, 18651 KiB  
Article
The Influence of Flame Exposure and Solid Particle Erosion on Tensile Strength of CFRP Substrate with Manufactured Protective Coating
by Przemysław Golewski and Michał Budka
Materials 2024, 17(5), 1203; https://doi.org/10.3390/ma17051203 - 5 Mar 2024
Cited by 1 | Viewed by 940
Abstract
This paper presents the results of laboratory tests for new materials made of a carbon fibre-reinforced polymer (CFRP) composite with a single-sided protective coating. The protective coatings were made of five different powders—Al2O3, aluminium, quartz sand, crystalline silica and [...] Read more.
This paper presents the results of laboratory tests for new materials made of a carbon fibre-reinforced polymer (CFRP) composite with a single-sided protective coating. The protective coatings were made of five different powders—Al2O3, aluminium, quartz sand, crystalline silica and copper—laminated in a single process during curing of the prepreg substrate with an epoxy matrix. The specimens were subjected to flame exposure and solid particle erosion tests, followed by uniaxial tensile tests. A digital image correlation (DIC) system was used to observe the damage location and deformation of the specimens. All coatings subjected to solid particle erosion allowed an increase in tensile failure force ranging from 5% to 31% compared to reference specimens made of purely CFRP. When exposed to flame, only three of the five materials tested, Al2O3, aluminium, quartz sand, could be used to protect the surface, which allowed an increase in tensile failure force of 5.6%. Full article
(This article belongs to the Topic Advanced Manufacturing and Surface Technology)
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<p>SEM images: (<b>a</b>) Al<sub>2</sub>O<sub>3</sub>, (<b>b</b>) aluminium, (<b>c</b>) quartz sand, (<b>d</b>) crystalline silica (×200), (<b>e</b>) crystalline silica (×2000) (<b>f</b>) copper.</p> Full article ">Figure 2
<p>Process of making the protective coating.</p> Full article ">Figure 3
<p>Schematics of laboratory stands: (<b>a</b>) for flame exposure (1—thermal imaging camera, 2—sample, 3—gas burner); (<b>b</b>) for solid particle erosion test.</p> Full article ">Figure 4
<p>Performing flame exposure tests: (<b>a</b>) Al<sub>2</sub>O<sub>3</sub>, (<b>b</b>) aluminium, (<b>c</b>) quartz sand, (<b>d</b>) crystalline silica, (<b>e</b>) copper, (<b>f</b>) reference.</p> Full article ">Figure 5
<p>Thermal camera images for 30 s flame exposure: (<b>a</b>) Al<sub>2</sub>O<sub>3</sub>, (<b>b</b>) aluminium, (<b>c</b>) quartz sand, (<b>d</b>) crystalline silica, (<b>e</b>) copper, (<b>f</b>) reference.</p> Full article ">Figure 6
<p>Batch-averaged temperature values on a 30 mm × 30 mm field for 30 s flame exposure.</p> Full article ">Figure 7
<p>Force–displacement diagrams and principal strain maps for specimens subjected to flame exposure: (<b>a</b>) Al<sub>2</sub>O<sub>3</sub>, (<b>b</b>) aluminium, (<b>c</b>) quartz sand, (<b>d</b>) crystalline silica, (<b>e</b>) copper, (<b>f</b>) reference.</p> Full article ">Figure 8
<p>Force–displacement diagrams and principal strain maps for specimens subjected to erosion exposure: (<b>a</b>) Al<sub>2</sub>O<sub>3</sub>, (<b>b</b>) aluminium, (<b>c</b>) quartz sand, (<b>d</b>) crystalline silica, (<b>e</b>) copper, (<b>f</b>) reference.</p> Full article ">Figure 8 Cont.
<p>Force–displacement diagrams and principal strain maps for specimens subjected to erosion exposure: (<b>a</b>) Al<sub>2</sub>O<sub>3</sub>, (<b>b</b>) aluminium, (<b>c</b>) quartz sand, (<b>d</b>) crystalline silica, (<b>e</b>) copper, (<b>f</b>) reference.</p> Full article ">Figure 9
<p>Deformation of the sample after removal from the autoclave.</p> Full article ">Figure 10
<p>Surface view of specimens for flame exposure tests: (<b>a</b>) Al<sub>2</sub>O<sub>3</sub>, (<b>b</b>) aluminium, (<b>c</b>) quartz sand, (<b>d</b>) crystalline silica, (<b>e</b>) copper, (<b>f</b>) reference.</p> Full article ">Figure 10 Cont.
<p>Surface view of specimens for flame exposure tests: (<b>a</b>) Al<sub>2</sub>O<sub>3</sub>, (<b>b</b>) aluminium, (<b>c</b>) quartz sand, (<b>d</b>) crystalline silica, (<b>e</b>) copper, (<b>f</b>) reference.</p> Full article ">Figure 11
<p>Surface view of specimens for solid particle erosion: (<b>a</b>) Al<sub>2</sub>O<sub>3</sub>, (<b>b</b>) aluminium, (<b>c</b>) quartz sand, (<b>d</b>) crystalline silica, (<b>e</b>) copper, (<b>f</b>) reference.</p> Full article ">Figure 12
<p>Results of uniaxial tensile tests: (<b>a</b>) summary of results averaged over a batch of maximum forces, (<b>b</b>) summary of results averaged over a batch of absorbed energy.</p> Full article ">Figure A1
<p>Microstructure of coatings: (<b>a</b>) cross-sectional view of the sample, (<b>b</b>) Al<sub>2</sub>O<sub>3</sub>, (<b>c</b>) aluminium, (<b>d</b>) quartz sand, (<b>e</b>) crystalline silica, (<b>f</b>) copper.</p> Full article ">Figure A2
<p>View of samples after flame exposure tests: (<b>a</b>) Al<sub>2</sub>O<sub>3</sub>, (<b>b</b>) aluminium, (<b>c</b>) quartz sand, (<b>d</b>) crystalline silica, (<b>e</b>) copper, (<b>f</b>) reference.</p> Full article ">Figure A2 Cont.
<p>View of samples after flame exposure tests: (<b>a</b>) Al<sub>2</sub>O<sub>3</sub>, (<b>b</b>) aluminium, (<b>c</b>) quartz sand, (<b>d</b>) crystalline silica, (<b>e</b>) copper, (<b>f</b>) reference.</p> Full article ">Figure A3
<p>View of samples after erosion tests: (<b>a</b>) Al<sub>2</sub>O<sub>3</sub>, (<b>b</b>) aluminium, (<b>c</b>) quartz sand, (<b>d</b>) crystalline silica, (<b>e</b>) copper, (<b>f</b>) reference.</p> Full article ">
19 pages, 6604 KiB  
Article
The Potential of 3D Printing in Thermal Insulating Composite Materials—Experimental Determination of the Impact of the Geometry on Thermal Resistance
by Beata Anwajler, Jerzy Szołomicki, Paweł Noszczyk and Michał Baryś
Materials 2024, 17(5), 1202; https://doi.org/10.3390/ma17051202 - 5 Mar 2024
Cited by 5 | Viewed by 1410
Abstract
This paper focuses on the analysis of the thermal properties of prototype insulation structures produced using SLS and SLA additive technologies. There is a noticeable lack of analysis in the scientific literature regarding the geometry of 3D-printed structures in terms of their thermal [...] Read more.
This paper focuses on the analysis of the thermal properties of prototype insulation structures produced using SLS and SLA additive technologies. There is a noticeable lack of analysis in the scientific literature regarding the geometry of 3D-printed structures in terms of their thermal properties. The aim of this paper was to analyze printed samples of prototype thermal insulation composite structures and their potential for use in building applications. The research material consisted of closed and open cell foams of varying structural complexity. Increasing the complexity of the composite core structure resulted in a statistically significant decrease in the value of the thermal conductivity coefficient λ and the heat transfer coefficient U, and an increase in the thermal resistance Rc. The experimental results showed that the geometric structure of the air voids in the material is a key factor in regulating heat transfer. The control of porosity in materials produced by additive technology can be an effective tool for designing structures with high insulation efficiency. The best performance of the prototype materials produced by the SLS method was a three-layer cellular composite with a gyroid core structure. It was also shown that the four-layer gyroid structure panels with an outer layer of metallized polyethylene film produced using 3D SLA printing had the best thermal insulation. As a result, the analysis confirmed the possibility of producing energy-efficient insulation materials using 3D printing. These materials can be used successfully in construction and other industries. Further research will significantly improve the quality, accuracy, and speed of printing insulation materials, reduce the negative impact on the natural environment, and develop intelligent adaptive solutions. Full article
(This article belongs to the Special Issue Advances in Functional Polymers and Composite for 3D Manufacturing, Insulations and Energy Storage)
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<p>Division of incremental technologies (elaborated by authors).</p> Full article ">Figure 2
<p>Methodological process used in this study (elaborated by authors).</p> Full article ">Figure 3
<p>Geometry of structures, 3D SLS-printed test samples: (<b>a</b>) circular, (<b>b</b>) square, (<b>c</b>) triangular, (<b>d</b>) hexagonal, (<b>e</b>) Kelvin tetrahedron, (<b>f</b>) gyroid, (<b>g</b>) diamond, (<b>h</b>) 2D Voronoi (elaborated by authors).</p> Full article ">Figure 4
<p>Example of a three-layer cellular composite sample with an inner core structure based on a Kelvin tetrahedral model produced by 3D SLS printing. Based on [<a href="#B12-materials-17-01202" class="html-bibr">12</a>].</p> Full article ">Figure 5
<p>Sketch of 3D-printed cellular composites with different layering: (<b>a</b>) 1-layer; (<b>b</b>) 2-layer; (<b>c</b>) 3-layer; (<b>d</b>) 4-layer (elaborated by authors).</p> Full article ">Figure 6
<p>Test stand for measuring thermal properties of structured panels with the geometry of the inner core of the gyroid made using 3D SLA technology; (<b>a</b>) four-layer panel with outer black polyethylene film, (<b>b</b>) four-layer panel with outer metallized polyethylene film (elaborated by authors).</p> Full article ">Figure 7
<p>Schematic of the test stand for thermal insulation testing (elaborated by authors).</p> Full article ">Figure 8
<p>Photograph of the test stand (elaborated by authors).</p> Full article ">Figure 9
<p>Thermograms for individual structures in SLS printing technology: (<b>a</b>) circular, (<b>b</b>) square, (<b>c</b>) triangular, (<b>d</b>) hexagonal, (<b>e</b>) Kelvin tetrahedral, (<b>f</b>) gyroidal, (<b>g</b>) diamond, (<b>h</b>) 2D Voronoi (elaborated by authors).</p> Full article ">Figure 10
<p>Thermograms for structures printed using SLA technology: (<b>a</b>) single-layer gyroid, (<b>b</b>) double-layer gyroid (elaborated by authors).</p> Full article ">Figure 11
<p>Graphical interpretation of the optimization of composite structures based on the thermal conductivity coefficient (λ), thermal resistance coefficient (R), and thermal transmittance coefficient (U) determined from the SLS 3D-printed samples.</p> Full article ">Figure 12
<p>Graphical interpretation of the optimization of composite structures based on the thermal conductivity coefficient (λ), thermal resistance coefficient (R), and thermal transmittance coefficient (U) determined from the SLA 3D-printed samples.</p> Full article ">Figure 13
<p>The coefficients of thermal conductivity for 3D-printed geometries.</p> Full article ">Figure 14
<p>Estimated heat transfer coefficients for various 3D geometries. Black border: thickness 50 mm, red border: thickness 100 mm.</p> Full article ">Figure 15
<p>Cross section of a window frame with an example of using 3D-printed geometries to make window frames: (<b>a</b>) a typical window frame, (<b>b</b>) a 3D-printed frame.</p> Full article ">
19 pages, 46658 KiB  
Article
Comparison of the Field Trapping Ability of MgB2 and Hybrid Disc-Shaped Layouts
by Michela Fracasso, Roberto Gerbaldo, Gianluca Ghigo, Daniele Torsello, Yiteng Xing, Pierre Bernstein, Jacques Noudem and Laura Gozzelino
Materials 2024, 17(5), 1201; https://doi.org/10.3390/ma17051201 - 5 Mar 2024
Viewed by 904
Abstract
Superconductors have revolutionized magnet technology, surpassing the limitations of traditional coils and permanent magnets. This work experimentally investigates the field-trapping ability of a MgB2 disc at various temperatures and proposes new hybrid (MgB2-soft iron) configurations using a numerical approach based [...] Read more.
Superconductors have revolutionized magnet technology, surpassing the limitations of traditional coils and permanent magnets. This work experimentally investigates the field-trapping ability of a MgB2 disc at various temperatures and proposes new hybrid (MgB2-soft iron) configurations using a numerical approach based on the vector potential (A→) formulation. The experimental characterization consists in measurements of trapped magnetic flux density carried out using cryogenic Hall probes located at different radial positions over the MgB2 sample, after a field cooling (FC) process and the subsequent removal of the applied field. Measurements were performed also as a function of the distance from the disc surface. The numerical modelling of the superconductor required the evaluation of the critical current density dependence on the magnetic flux density (Jc(B)) obtained through an iterative procedure whose output were successfully validated by the comparison between experimental and computed data. The numerical model, upgraded to also describe the in-field behavior of ARMCO soft iron, was then employed to predict the field-trapping ability of hybrid layouts of different shapes. The most promising results were achieved by assuming a hollow superconducting disc filled with a ferromagnetic (FM) cylinder. With such a geometry, optimizing the radius of the FM cylinder while the external dimensions of the superconducting disc are kept unchanged, an improvement of more than 30% is predicted with respect to the full superconducting disc, assuming a working temperature of 20 K. Full article
(This article belongs to the Special Issue Novel Superconducting Materials and Applications of Superconductivity)
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<p>Scanning electron microscopy image of the microstructure of the MgB<sub>2</sub> disc.</p> Full article ">Figure 2
<p>Schematic view of the MgB<sub>2</sub> disc (<b>a</b>) and of the Hall probes’ positions (<b>b</b>). The radial positions with respect to the sample center are the following: Hall probe #1: 8.0 mm, #2: 5.75 mm, #3: 3.5 mm, #4: 0.0 mm (sample center), #5: 2.0 mm, #6: 4.0 mm, #7: 6.0 mm, and #8: 8.5 mm.</p> Full article ">Figure 3
<p>Trapped field values measured by the Hall probes at the radial positions reported in the figure legends as a function of the distance from the top surface of the MgB<sub>2</sub> disc. The data were obtained at T = 20 K (<b>a</b>), T = 25 K (<b>b</b>), and T = 30 K (<b>c</b>).</p> Full article ">Figure 3 Cont.
<p>Trapped field values measured by the Hall probes at the radial positions reported in the figure legends as a function of the distance from the top surface of the MgB<sub>2</sub> disc. The data were obtained at T = 20 K (<b>a</b>), T = 25 K (<b>b</b>), and T = 30 K (<b>c</b>).</p> Full article ">Figure 4
<p><math display="inline"><semantics> <msub> <mi>J</mi> <mi>c</mi> </msub> </semantics></math> dependence on the applied magnetic field at T = 20 K obtained from the <math display="inline"><semantics> <msub> <mi mathvariant="normal">B</mi> <mrow> <mi>t</mi> <mi>r</mi> <mi>a</mi> <mi>p</mi> <mi>p</mi> <mi>e</mi> <mi>d</mi> <mo>,</mo> <mi>z</mi> </mrow> </msub> </semantics></math> vs. <math display="inline"><semantics> <mrow> <msub> <mi>μ</mi> <mn>0</mn> </msub> <msub> <mi>H</mi> <mrow> <mi>a</mi> <mi>p</mi> <mi>p</mi> <mi>l</mi> </mrow> </msub> </mrow> </semantics></math> curve measured at <span class="html-italic">r</span> = 0 (Hall probe #4) applying Equation (<a href="#FD6-materials-17-01201" class="html-disp-formula">6</a>) (black symbols) and calculated with a polynomial fit (see text—red solid line).</p> Full article ">Figure 5
<p>Comparison between the experimental (symbols) and computed (lines) magnetic flux density (<b>a</b>) and trapped field (<b>b</b>) values, both plotted as a function of the applied magnetic field. The computed curves were obtained using the <math display="inline"><semantics> <mrow> <msub> <mi>J</mi> <mi>c</mi> </msub> <mrow> <mo>(</mo> <mi>B</mi> <mo>)</mo> </mrow> </mrow> </semantics></math> polynomial law plotted in <a href="#materials-17-01201-f004" class="html-fig">Figure 4</a> (red curve) and the exponential <math display="inline"><semantics> <msub> <mi mathvariant="normal">J</mi> <mi>c</mi> </msub> </semantics></math>(B) relationship reported in Equation (<a href="#FD7-materials-17-01201" class="html-disp-formula">7</a>) (cyan curve). The measurement was carried out by Hall probe #4 located on the disc’s axis at 20 K and 1.5 mm above the disc surface, decreasing the applied field after field cooling in an external field <math display="inline"><semantics> <mrow> <msub> <mi>μ</mi> <mn>0</mn> </msub> <msub> <mi>H</mi> <mrow> <mi>a</mi> <mi>p</mi> <mi>p</mi> <mi>l</mi> </mrow> </msub> </mrow> </semantics></math> = 4 T.</p> Full article ">Figure 6
<p>Comparison among <math display="inline"><semantics> <msubsup> <mi>J</mi> <mi>c</mi> <mn>0</mn> </msubsup> </semantics></math> and <math display="inline"><semantics> <msubsup> <mi>J</mi> <mi>c</mi> <mrow> <mi>i</mi> <mo>+</mo> <mn>1</mn> </mrow> </msubsup> </semantics></math> vs. <math display="inline"><semantics> <mrow> <msub> <mi>μ</mi> <mn>0</mn> </msub> <msub> <mi mathvariant="normal">H</mi> <mrow> <mi>a</mi> <mi>p</mi> <mi>p</mi> <mi>l</mi> </mrow> </msub> </mrow> </semantics></math> curves obtained from the values of the trapped field assessed by measurement applying Equation (<a href="#FD6-materials-17-01201" class="html-disp-formula">6</a>) (black curve) and through computations (coloured curves). The latter represent the results obtained after each iteration of the iterative process presented in the main text. The final aim was to define a <math display="inline"><semantics> <msub> <mi>J</mi> <mi>c</mi> </msub> </semantics></math>(B) suitable to reproduce the experimental data, which was identified in the <math display="inline"><semantics> <msubsup> <mi mathvariant="normal">J</mi> <mi>c</mi> <mn>9</mn> </msubsup> </semantics></math> curve (light-blue curve).</p> Full article ">Figure 7
<p>Comparison between the experimental (symbols) and numerically computed (lines) magnetic flux density (<b>a</b>) and trapped field (<b>b</b>) values, both plotted as a function of the applied magnetic field. The computed curves were obtained using the <math display="inline"><semantics> <mrow> <msub> <mi>J</mi> <mi>c</mi> </msub> <mrow> <mo>(</mo> <mi>B</mi> <mo>)</mo> </mrow> </mrow> </semantics></math> polynomial law plotted in <a href="#materials-17-01201-f004" class="html-fig">Figure 4</a> (red curve), the exponential <math display="inline"><semantics> <mrow> <msub> <mi>J</mi> <mi>c</mi> </msub> <mrow> <mo>(</mo> <mi>B</mi> <mo>)</mo> </mrow> </mrow> </semantics></math> in Equation (<a href="#FD7-materials-17-01201" class="html-disp-formula">7</a>) (cyan curve), and the <math display="inline"><semantics> <mrow> <msubsup> <mi>J</mi> <mi>c</mi> <mn>9</mn> </msubsup> <mrow> <mo>(</mo> <mi>B</mi> <mo>)</mo> </mrow> </mrow> </semantics></math> polynomial law extracted following the procedure described in the main text (orange curve). The measurement was carried out at 20 K, decreasing the applied field after field cooling in an external field <math display="inline"><semantics> <mrow> <msub> <mi>μ</mi> <mn>0</mn> </msub> <msub> <mi mathvariant="normal">H</mi> <mrow> <mi>a</mi> <mi>p</mi> <mi>p</mi> <mi>l</mi> </mrow> </msub> </mrow> </semantics></math> = 4T. Data refer to Hall probe #4 position, placed on the sample’s axis, 1.5 mm above the disc top surface.</p> Full article ">Figure 8
<p>Comparison between the magnetic flux density (<b>a</b>) and trapped field (<b>b</b>) measured by Hall probes #4 and #6 at 20 K when decreasing the external field after field cooling in <math display="inline"><semantics> <mrow> <msub> <mi>μ</mi> <mn>0</mn> </msub> <msub> <mi>H</mi> <mrow> <mi>a</mi> <mi>p</mi> <mi>p</mi> <mi>l</mi> </mrow> </msub> </mrow> </semantics></math> = 4 T (symbols) and the corresponding computed values (lines).</p> Full article ">Figure 9
<p>Comparison between the trapped magnetic flux density measured by all the Hall probes as a function of the distance from the top surface of the disc, at 20 K, in remnant state after field cooling in <math display="inline"><semantics> <mrow> <msub> <mi>μ</mi> <mn>0</mn> </msub> <msub> <mi>H</mi> <mrow> <mi>a</mi> <mi>p</mi> <mi>p</mi> <mi>l</mi> </mrow> </msub> </mrow> </semantics></math> = 4 T (symbols), and the corresponding values computed by numerical simulations (lines).</p> Full article ">Figure 10
<p>Comparison between the magnetic flux density measured by all of the Hall probes as a function of the distance from the top surface of the disc, at T = 25 K (<b>a</b>), and T = 30 K (<b>b</b>) after field cooling in an applied field of <math display="inline"><semantics> <mrow> <msub> <mi>μ</mi> <mn>0</mn> </msub> <msub> <mi>H</mi> <mrow> <mi>a</mi> <mi>p</mi> <mi>p</mi> <mi>l</mi> </mrow> </msub> </mrow> </semantics></math> = 3 T and 2 T, respectively (symbols), and the corresponding values computed by numerical simulations (lines).</p> Full article ">Figure 11
<p>Schematic view of the hybrid layouts numerically investigated. The superconducting components (grey) are discs with the same size as the disc characterized experimentally, except the layout <span class="html-italic">geom4</span>, as detailed in the main text. The dimensions of the ferromagnetic components (cyan) are characterized by two recurring values <math display="inline"><semantics> <mrow> <mi>d</mi> <mo>=</mo> <mn>2.43</mn> </mrow> </semantics></math> mm and <math display="inline"><semantics> <mrow> <msup> <mi>d</mi> <mo>′</mo> </msup> <mo>=</mo> <mn>5.04</mn> </mrow> </semantics></math> mm.</p> Full article ">Figure 12
<p>(<b>Left</b>) Magnetic flux density <math display="inline"><semantics> <msub> <mi mathvariant="normal">B</mi> <mi>z</mi> </msub> </semantics></math> calculated 1 mm above the top surfaces of the hybrid configurations. (<b>Right</b>) magnification of the <math display="inline"><semantics> <msub> <mi mathvariant="normal">B</mi> <mi>z</mi> </msub> </semantics></math> values in the zone close to the disc’s axis.</p> Full article ">Figure 13
<p>(<b>a</b>) <math display="inline"><semantics> <msub> <mi mathvariant="normal">B</mi> <mrow> <mi>t</mi> <mi>r</mi> <mi>a</mi> <mi>p</mi> <mi>p</mi> <mi>e</mi> <mi>d</mi> <mo>,</mo> <mi>z</mi> </mrow> </msub> </semantics></math> dependence on the radial position calculated 1 mm above the surface with the FM layers. (<b>b</b>–<b>d</b>) 3D maps of the trapped field magnitude calculated 1 mm from the surface with the FM layers for <span class="html-italic">geom2</span>, <span class="html-italic">geom3</span>, and <span class="html-italic">geom5</span>, respectively.</p> Full article ">Figure 14
<p>These are 3D maps of the trapped flux density magnitude calculated 1 mm above the top surfaces of superconducting disc (<b>a</b>) and layout <span class="html-italic">geom4</span>, the latter as the radius of the ferromagnetic cylinder increases: <math display="inline"><semantics> <mrow> <mi>d</mi> <mo>=</mo> <mn>1.21</mn> </mrow> </semantics></math> mm (<b>b</b>), <math display="inline"><semantics> <mrow> <mi>d</mi> <mo>=</mo> <mn>1.82</mn> </mrow> </semantics></math> mm (<b>c</b>), <math display="inline"><semantics> <mrow> <mi>d</mi> <mo>=</mo> <mn>2.43</mn> </mrow> </semantics></math> mm (<b>d</b>), <math display="inline"><semantics> <mrow> <mi>d</mi> <mo>=</mo> <mn>3.03</mn> </mrow> </semantics></math> mm (<b>e</b>), and <math display="inline"><semantics> <mrow> <mi>d</mi> <mo>=</mo> <mn>3.64</mn> </mrow> </semantics></math> mm (<b>f</b>).</p> Full article ">Figure 15
<p>Magnetic flux density <math display="inline"><semantics> <msub> <mi mathvariant="normal">B</mi> <mi>z</mi> </msub> </semantics></math> calculated 1 mm above the top surfaces of layouts named <span class="html-italic">geom4</span> for different values of the FM cylinder radius. The outer radius of the hollow superconducting disc surrounding the FM was kept constant and equal to 10.08 mm.</p> Full article ">Figure 16
<p>Magnitude of the trapped flux density values (colour maps) and distribution of the magnetic flux lines for the SC disc (<b>a</b>) and the five layouts <span class="html-italic">geom4</span> with an FM cylinder of radius <math display="inline"><semantics> <mrow> <mi>d</mi> <mo>=</mo> <mn>1.21</mn> </mrow> </semantics></math> mm (<b>b</b>), <math display="inline"><semantics> <mrow> <mi>d</mi> <mo>=</mo> <mn>1.82</mn> </mrow> </semantics></math> mm (<b>c</b>), <math display="inline"><semantics> <mrow> <mi>d</mi> <mo>=</mo> <mn>2.43</mn> </mrow> </semantics></math> mm (<b>d</b>), <math display="inline"><semantics> <mrow> <mi>d</mi> <mo>=</mo> <mn>3.03</mn> </mrow> </semantics></math> mm (<b>e</b>), and <math display="inline"><semantics> <mrow> <mi>d</mi> <mo>=</mo> <mn>3.64</mn> </mrow> </semantics></math> mm (<b>f</b>) calculated at T = 20 K.</p> Full article ">Figure 17
<p>Magnetic flux density <math display="inline"><semantics> <msub> <mi mathvariant="normal">B</mi> <mi>z</mi> </msub> </semantics></math> calculated 1 mm above the top surfaces of the layouts <span class="html-italic">geom4</span> for different values of the FM cylinder radius and assuming a working temperature of T = 25 K (<b>left</b>) and T = 30 K (<b>right</b>).</p> Full article ">Figure 18
<p>Percentage increase of the magnetic flux density trapped in remnant state by the five layouts <span class="html-italic">geom4</span> with respect to the magnetic flux density trapped by the superconducting disc alone.</p> Full article ">
13 pages, 10214 KiB  
Article
Influences of Composite Electrodeposition Parameters on the Properties of Ni-Doped Co-Mn Composite Spinel Coatings
by Wei Tong, Weiqiang Wang, Xiayu Leng and Jianli Song
Materials 2024, 17(5), 1200; https://doi.org/10.3390/ma17051200 - 5 Mar 2024
Cited by 1 | Viewed by 765
Abstract
To enhance the comprehensive performance of solid oxide fuel cells (SOFCs) ferritic stainless steel (FSS) interconnectors, a novel approach involving composite electrodeposition and thermal conversion is proposed to prepare Ni-doped Co-Mn composite spinel protective coatings on FSS surfaces. The process involves the composite [...] Read more.
To enhance the comprehensive performance of solid oxide fuel cells (SOFCs) ferritic stainless steel (FSS) interconnectors, a novel approach involving composite electrodeposition and thermal conversion is proposed to prepare Ni-doped Co-Mn composite spinel protective coatings on FSS surfaces. The process involves the composite electrodeposition of a Ni-doped Co-Mn precursor coating, followed by thermal conversion to obtain the Co-Mn-Ni composite spinel coating. Crofer 22H was used as the substrate and orthogonal experiments were designed to investigate the influences of deposition solution pH, stirring rate, cathode current density, and the element content of Mn and Ni on the surface morphology and properties of the composite coatings, respectively. The characterization of the prepared coatings was conducted through macroscopic and microscopic morphology observations of the component surface, energy dispersive spectroscopy (EDS) analysis, and area specific resistance (ASR) testing, etc. Finally, the optimized composite electrodeposition parameters and the Mn-Ni content ratio in the solution were obtained. Experimental results indicated that the composite spinel coating prepared with the optimized process parameters exhibited excellent adhesion to the substrate, and the diffusion and migration of Cr element has been effectively inhibited. Compared with the substrate, the ASR of the coated components has also been decreased simultaneously, which provided an effective method for the surface modification of SOFC FSS interconnectors. Full article
(This article belongs to the Section Advanced Composites)
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<p>Schematic diagram of the preparation process for the composite spinel coating.</p> Full article ">Figure 2
<p>(<b>a</b>) Macroscopic morphology of the composite precursor coating of the sample; (<b>b</b>) SEM morphology of the precursor coating; (<b>c</b>) macroscopic morphology of the composite spinel coating of the sample; and (<b>d</b>) SEM morphology of the spinel coating.</p> Full article ">Figure 3
<p>SEM morphologies (<b>left</b>) and Mn element EDS distribution (<b>right</b>) on the spinel coating surface: (<b>a</b>) at pH4; (<b>b</b>) at pH5; and (<b>c</b>) at pH6.</p> Full article ">Figure 3 Cont.
<p>SEM morphologies (<b>left</b>) and Mn element EDS distribution (<b>right</b>) on the spinel coating surface: (<b>a</b>) at pH4; (<b>b</b>) at pH5; and (<b>c</b>) at pH6.</p> Full article ">Figure 4
<p>SEM morphologies of the spinel coating surface under the current density of 25 mA/cm<sup>2</sup> and at a stirring rate of (<b>a</b>) 600 rpm, (<b>b</b>) 700 rpm, and (<b>c</b>) 800 rpm.</p> Full article ">Figure 5
<p>SEM morphologies of the spinel coating surface under the current density of 35 mA/cm<sup>2</sup> and at a stirring rate of (<b>a</b>) 600 rpm, (<b>b</b>) 700 rpm, and (<b>c</b>) 800 rpm.</p> Full article ">Figure 6
<p>SEM morphologies of the spinel coating surface under the current density of 45 mA/cm<sup>2</sup> and at a stirring rate of (<b>a</b>) 600 rpm, (<b>b</b>) 700 rpm, and (<b>c</b>) 800 rpm.</p> Full article ">Figure 7
<p>SEM morphology of the precursor coating surface at a Mn<sub>3</sub>O<sub>4</sub> content of (<b>a</b>) 133 g/L, (<b>b</b>) 167 g/L, and (<b>c</b>) 200 g/L (Oxides tended to aggregate in red circles).</p> Full article ">Figure 8
<p>Mn and Ni content in the precursor coating.</p> Full article ">Figure 9
<p>ASR curves for the spinel coatings varied with different contents of NiO in the solution.</p> Full article ">Figure 10
<p>ASR curves of the spinel samples and bare substrate varying in the range of 600–800 °C.</p> Full article ">Figure 11
<p>(<b>a</b>) Cross-sectional morphology of the precursor coating; (<b>b</b>) EDS line scan of the precursor coating; (<b>c</b>) cross-sectional morphology of the spinel coating; and (<b>d</b>) EDS line scan of the spinel coating.</p> Full article ">Figure 12
<p>ASR of the spinel samples with different Mn<sub>3</sub>O<sub>4</sub> and NiO additions at 800 °C.</p> Full article ">
22 pages, 25261 KiB  
Article
Simulation Study on Temperature and Stress Fields in Mg-Gd-Y-Zn-Zr Alloy during CMT Additive Manufacturing Process
by Mingkun Zhao, Zhanyong Zhao, Wenbo Du, Peikang Bai and Zhiquan Huang
Materials 2024, 17(5), 1199; https://doi.org/10.3390/ma17051199 - 5 Mar 2024
Viewed by 972
Abstract
A new heat source combination, consisting of a uniform body heat source and a tilted double ellipsoidal heat source, has been developed for cold metal transfer (CMT) wire-arc additive manufacturing of Mg-Gd-Y-Zn-Zr alloy. Simulations were conducted to analyze the temperature field and stress [...] Read more.
A new heat source combination, consisting of a uniform body heat source and a tilted double ellipsoidal heat source, has been developed for cold metal transfer (CMT) wire-arc additive manufacturing of Mg-Gd-Y-Zn-Zr alloy. Simulations were conducted to analyze the temperature field and stress distribution during the process. The optimal combination of feeding speed and welding speed was found to be 8 m/min and 8 mm/s, respectively, resulting in the lowest thermal accumulation and residual stress. Z-axis residual stress was identified as the main component of residual stress. Electron Backscatter Diffraction (EBSD) testing showed weak texture strength, and Kernel Average Misorientation (KAM) analysis revealed that the 1st layer had the highest residual stress, while the 11th layer had higher residual stress than the 6th layer. Microhardness in the 1st, 11th, and 6th layers varies due to residual stress impacts on dislocation density. Higher residual stress increases dislocation density, raising microhardness in components. The experimental results were highly consistent with the simulated results. Full article
(This article belongs to the Special Issue Additive Manufacturing and Microstructure Characteristics of Metallic Material)
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<p>Model established using Creo for a wire feeding speed of 8 m/min.</p> Full article ">Figure 2
<p>Schematic diagram of model establishment: (<b>a</b>) schematic diagram of CMT process; (<b>b</b>) schematic diagram of stress field data extracted along the path; (<b>c</b>) details of finite element meshing; (<b>d</b>) schematic diagram of sampling position.</p> Full article ">Figure 3
<p>Heat source diagram: (<b>a</b>) double ellipsoid heat source loading diagram in arc weld bead; (<b>b</b>) combined heat source loading diagram in arc weld bead; (<b>c</b>) traditional double ellipsoid heat source diagram; (<b>d</b>) comparison of the melt pool morphology between the novel heat source and the double ellipsoid heat source under the same process parameters.</p> Full article ">Figure 4
<p>The thermophysical parameters of Mg-9.2Gd-3.2Y-2Zn-0.4Zr alloy calculated using JMatPro during cooling from 800 °C to room temperature.</p> Full article ">Figure 5
<p>Comparison of simulated molten pool morphology and actual molten pool morphology.</p> Full article ">Figure 6
<p>Thermal history simulation results under different process parameters, where A, B, and C represent wire feeding speeds, and within the parentheses of A, B, and C are the welding speeds: (<b>a</b>–<b>c</b>) represent the thermal history of the nodes at the center of the first, sixth, and eleventh layers of the second weld track, respectively; (<b>d</b>) denotes the minimum temperature during the additive manufacturing process.</p> Full article ">Figure 7
<p>Comparison of simulated melt pools using the process parameters with the maximum and minimum heat input: (<b>a</b>–<b>c</b>) depict comparative simulation results for the melt pools in the first, sixth, and eleventh layers, respectively.</p> Full article ">Figure 8
<p>Residual stress distribution along path A, B under varying process parameters: (<b>a</b>–<b>c</b>) display the residual stress distributions for wire feeding speeds of 8 m/min, 9 m/min, and 10 m/min, respectively; (<b>d</b>) illustrates the actual cross-sectional morphology of the melt pool; (<b>e</b>) schematic diagram of stress field data extracted along the path.</p> Full article ">Figure 9
<p>Distribution of residual stress along path C, D under different process parameters: (<b>a</b>–<b>c</b>) illustrate the distributions of residual stress at wire feeding speeds of 8 m/min, 9 m/min, and 10 m/min, respectively; (<b>d</b>) schematic diagram of stress field data extracted along the path.</p> Full article ">Figure 10
<p>Distribution of residual stress along path E, F under disparate process parameters: (<b>a</b>–<b>c</b>) correspond to the residual stress distributions at wire feeding speeds of 8 m/min, 9 m/min, and 10 m/min, respectively; (<b>d</b>) schematic diagram of stress field data extracted along the path.</p> Full article ">Figure 11
<p>Residual stress distribution of longitudinal section under the process parameters of a wire feeding speed of 8 m/min and a welding speed of 8 mm/s: (<b>a</b>) equivalent stress distribution; (<b>b</b>) residual stress distribution in X direction; (<b>c</b>) residual stress distribution in Y direction; (<b>d</b>) residual stress distribution in Z direction.</p> Full article ">Figure 12
<p>Distribution of the KAM in the longitudinal section under the process parameters of an 8 m/min wire feeding speed and an 8 mm/s welding speed: (<b>a</b>–<b>c</b>) represent the KAM distribution at the first, sixth, and eleventh layers, respectively; (<b>d</b>) the comparison of residual stress simulation values with experimental values for each layer.</p> Full article ">Figure 13
<p>Electron Backscatter Diffraction (EBSD) maps under the process parameters with a wire feeding speed of 8 m/min and a welding speed of 8 mm/s: (<b>a</b>–<b>c</b>) respectively correspond to the pole figures and Inverse Pole Figure (IPF) maps of the first, sixth, and eleventh layers.</p> Full article ">Figure 14
<p>Hardness magnitude and Grain Boundary Density (GND) distribution under the process parameters with a wire feeding speed of 8 m/min and a welding speed of 8 mm/s: (<b>a</b>) presents the hardness values for the coarse-grained and fine-grained zones in each layer; (<b>b</b>–<b>d</b>) depict the GND distribution for the first, sixth, and eleventh layers, respectively.</p> Full article ">Figure 15
<p>Engineering stress–strain curves for compressed specimens.</p> Full article ">
12 pages, 3631 KiB  
Article
Effect of Tungsten Inert Gas Remelting on Microstructure and Corrosion Resistance of Q450NQR1 High-Strength Weathering Steel-Welded Joints
by Xuemei Li, Yang Liu, Rui Guo, Zicheng Li, Qingming Hu, Meng Liu, Lei Zhu and Xiangxia Kong
Materials 2024, 17(5), 1198; https://doi.org/10.3390/ma17051198 - 4 Mar 2024
Viewed by 885
Abstract
In this paper, the corrosion environment of a railway coal truck was simulated with 1.0%H2SO4 + 3%NaCl solution. The effect of weld toe Tungsten Inert Gas (TIG) remelting on the microstructure and corrosion resistance of welded joints of Q450NQR1 high-strength [...] Read more.
In this paper, the corrosion environment of a railway coal truck was simulated with 1.0%H2SO4 + 3%NaCl solution. The effect of weld toe Tungsten Inert Gas (TIG) remelting on the microstructure and corrosion resistance of welded joints of Q450NQR1 high-strength weathering steel was studied. The results show that the weld toe melts to form a remelting area after TIG remelting. After TIG remelting, the weld geometry was improved, and the stress concentration factor decreased from 1.17 to 1.06 at the weld toe, a decrease of 9.4%. TIG remelting refines the microstructure of the weld toe and improves the corrosion resistance of the welded joint. The surface of the TIG-remelted sample is uniformly corroded with no “deep and narrow” pits after the removal of corrosion products. The weight loss rate and corrosion rate of remelted welds are lower than those of unremelted welds. The structure of corrosion products is loose at the initial stage of corrosion, and the corrosion products are transformed into Fe3O4 and Fe2O3 protective rust layers with a dense structure after 480 h of corrosion. With the extension of corrosion time, the tensile strength and percentage elongation of the specimen decreased linearly. The decreasing rates of tensile strength of remelted and unremelted specimens were 0.09 and 0.11, respectively, and the decreasing rates of elongation after fracture were 0.0061 and 0.0076, respectively. Full article
(This article belongs to the Section Corrosion)
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<p>Schematic diagram of tensile specimen.</p> Full article ">Figure 2
<p>The cross-sectional morphology of the test specimen after TIG remelting.</p> Full article ">Figure 3
<p>Microstructure of welded joints between unremelted and TIG remelting specimens (<b>a</b>) MWZ (<b>b</b>) MFZ (<b>c</b>) TWZ (<b>d</b>) TFZ.</p> Full article ">Figure 4
<p>Macroscopic morphology of the corroded surface of welded joints at different corrosion periods. (<b>a</b>) unremelted 240 h, (<b>b</b>) unremelted 360 h, (<b>c</b>) unremelted 480 h, (<b>d</b>) unremelted 600 h, (<b>e</b>) TIG remelting 240 h, (<b>f</b>) TIG remelting 360 h, (<b>g</b>) TIG remelting 480 h, (<b>h</b>) TIG remelting 600 h.</p> Full article ">Figure 5
<p>The surface morphology of the heat-affected zone after removal of corrosion products from TIG remelting and unremelted specimens. (<b>a</b>) unremelted 240 h, (<b>b</b>) unremelted 360 h, (<b>c</b>) unremelted 480 h, (<b>d</b>) unremelted 600 h, (<b>e</b>) TIG remelting 240 h, (<b>f</b>) TIG remelting 360 h, (<b>g</b>) TIG remelting 480 h, (<b>h</b>) TIG remelting 600 h.</p> Full article ">Figure 6
<p>Average weight loss rate (<b>a</b>) and corrosion rate (<b>b</b>) of unremelted and TIG remelting samples under different corrosion periods.</p> Full article ">Figure 7
<p>The corrosion products microstructure on the TIG remelting specimens surface. (<b>a</b>) 240 h, (<b>b</b>) 360 h, (<b>c</b>) 480 h, (<b>d</b>) 600 h.</p> Full article ">Figure 8
<p>Tensile strength (<b>a</b>) and percentage elongation after fracture (<b>b</b>) of unremelted and TIG remelting samples under different corrosion periods.</p> Full article ">
56 pages, 21190 KiB  
Review
An In-Depth Exploration of Unconventional Machining Techniques for INCONEL® Alloys
by André F. V. Pedroso, Naiara P. V. Sebbe, Francisco J. G. Silva, Raul D. S. G. Campilho, Rita C. M. Sales-Contini, Rui P. Martinho and Rafaela B. Casais
Materials 2024, 17(5), 1197; https://doi.org/10.3390/ma17051197 - 4 Mar 2024
Cited by 1 | Viewed by 1243
Abstract
Build-up-edge (BUE), high-temperature machining and tool wear (TW) are some of the problems associated with difficult-to-machine materials for high-temperature applications, contributing significantly to high-cost manufacturing and poor tool life (TL) management. A detailed review of non-traditional machining processes that ease the machinability of [...] Read more.
Build-up-edge (BUE), high-temperature machining and tool wear (TW) are some of the problems associated with difficult-to-machine materials for high-temperature applications, contributing significantly to high-cost manufacturing and poor tool life (TL) management. A detailed review of non-traditional machining processes that ease the machinability of INCONEL®, decrease manufacturing costs and suppress assembly complications is thus of paramount significance. Progress taken within the field of INCONEL® non-conventional processes from 2016 to 2023, the most recent solutions found in the industry, and the prospects from researchers have been analysed and presented. In ensuing research, it was quickly noticeable that some techniques are yet to be intensely exploited. Non-conventional INCONEL® machining processes have characteristics that can effectively increase the mechanical properties of the produced components without tool-workpiece contact, posing significant advantages over traditional manufacturing. Full article
(This article belongs to the Special Issue Tools for Machining and Forming: Novel Materials and Wear Behaviour)
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Figure 1

Figure 1
<p>Measured true-stress–strain (<span class="html-italic">σ<sub>tr</sub></span>–<span class="html-italic">ε<sub>tr</sub></span>) curves (discrete points) for (<b>a</b>) INCONEL<sup>®</sup> 718 and (<b>b</b>) INCONEL<sup>®</sup> 625. Corresponding computed results (solid lines) from the material model after calibration. The tests were performed with a nominal <math display="inline"><semantics> <mrow> <mover accent="true"> <mrow> <mi>ε</mi> </mrow> <mo>˙</mo> </mover> </mrow> </semantics></math> = 0.01 Hz for INCONEL<sup>®</sup> 625, while INCONEL<sup>®</sup> 718 was tested with 0.01 &lt; <math display="inline"><semantics> <mrow> <mover accent="true"> <mrow> <mi>ε</mi> </mrow> <mo>˙</mo> </mover> </mrow> </semantics></math> &lt; 1 Hz [<a href="#B8-materials-17-01197" class="html-bibr">8</a>].</p> Full article ">Figure 2
<p>(<b>a</b>) <span class="html-italic">σ</span><sub>yc</sub> and (<b>b</b>) <span class="html-italic">σ</span><sub>yc</sub>/<span class="html-italic">ρ</span> dependent on <span class="html-italic">T</span>. Typical <span class="html-italic">σ</span><sub>yc</sub>/<span class="html-italic">ρ</span> requirements for thermal protection sheet, turbine blades and disks are shown in [<a href="#B9-materials-17-01197" class="html-bibr">9</a>].</p> Full article ">Figure 3
<p>Classification of modern machining technologies (adapted from [<a href="#B28-materials-17-01197" class="html-bibr">28</a>]).</p> Full article ">Figure 4
<p>Image of the width and height of the wear scar on insert A (SiAlON grade 1). The image was captured on an Alicona infinite-focus microscope [<a href="#B36-materials-17-01197" class="html-bibr">36</a>].</p> Full article ">Figure 5
<p>Different arrangements of tool-sidewall outlet holes: (<b>a</b>) schematic, (<b>b</b>) photo [<a href="#B53-materials-17-01197" class="html-bibr">53</a>].</p> Full article ">Figure 6
<p>Schematic model of the electrochemical machining (ECM) behaviour of INCONEL<sup>®</sup> 718 in C<sub>6</sub>H<sub>5</sub>K<sub>3</sub>O<sub>7</sub> solution, (<b>a</b>) passivating film with a thin and loose porous structure, (<b>b</b>) few electrolytic products are formed where the passivating film is broken, and INCONEL<sup>®</sup> 718 particles are gradually exposed to the electrolyte. A new passivation is regenerated during pulse-off time (<span class="html-italic">T</span><sub>off</sub>), (<b>c</b>) passivation film and micro-pitting caused by C<sub>6</sub>H<sub>5</sub>K<sub>3</sub>O<sub>7</sub> solution. (<b>d</b>) Elimination of electrolytic products, which stabilises the pulse ECM dissolution process and improves INCONEL<sup>®</sup> 718 surface quality [<a href="#B54-materials-17-01197" class="html-bibr">54</a>].</p> Full article ">Figure 7
<p>Principles of helical wire electrochemical discharge machining (HWECDM). (<b>a</b>) Anode reaction follows as M—ne<sup>−</sup> → M<sup>n+</sup>, whereas cathode reaction follows as 2HOCH<sub>2</sub>CH<sub>2</sub>OH + 2e<sup>−</sup> → 2HOCH<sub>2</sub>CH<sub>2</sub>O<sup>−</sup> + H<sub>2</sub>↑. (<b>b</b>) The electrical conductivity of the working medium between the electrodes diminishes, resulting in an increase in the resistance of the electrolyte and an elevation of the electrical potential gradient between the electrodes. (<b>c</b>) A discharge channel forms at a protruding point of the helical wire electrode, leading to material removal from the workpiece. (<b>d</b>) The by-products of electrochemical machining (ECM) and electrical discharge machining (EDM) are expelled from the machining gap due to the combined effects of the explosive force from periodic electrical discharges and the axial movement of the helical wire electrode [<a href="#B55-materials-17-01197" class="html-bibr">55</a>].</p> Full article ">Figure 8
<p>A 3D schematic of the experimental electrochemical machining (ECM) proceeding [<a href="#B56-materials-17-01197" class="html-bibr">56</a>].</p> Full article ">Figure 9
<p>(<b>a</b>) EDM drilling schematic. (<b>b</b>) Examination of energy balance, crater formation, heat flux and pressure distribution during a single discharge in electrical discharge machining (EDM). (<b>c</b>) A comparison between simulated and measured crater shapes is presented as an illustration. (<b>d</b>) Investigation of the velocity field induced by the Marangoni effect [<a href="#B61-materials-17-01197" class="html-bibr">61</a>] in the EDM melt pool simulation; (<b>e</b>) recast layer measurements, the craters are performed with the same set of parameters, the material is almost entirely ejected on the left and not ejected on the right (adapted from [<a href="#B58-materials-17-01197" class="html-bibr">58</a>]).</p> Full article ">Figure 10
<p>A 3D overview of the machined surface showing topography [<a href="#B42-materials-17-01197" class="html-bibr">42</a>].</p> Full article ">Figure 11
<p>X-ray diffraction (XRD) spectra for the electrical discharge machining (EDM) treated work surface of (<b>a</b>) INCONEL<sup>®</sup> 601, (<b>b</b>) INCONEL<sup>®</sup> 625, (<b>c</b>) INCONEL<sup>®</sup> 718 and (<b>d</b>) INCONEL<sup>®</sup> 825 acquired under the parameter settings [<span class="html-italic">V</span><sub>g</sub> = 60 V, <span class="html-italic">I</span><sub>p</sub> = 5 A, <span class="html-italic">T</span><sub>on</sub> = 200 μs, <span class="html-italic">τ</span> = 70% and <span class="html-italic">F</span><sub>p</sub> = 0.3 bar] [<a href="#B65-materials-17-01197" class="html-bibr">65</a>].</p> Full article ">Figure 12
<p>The 3D surface topographies of the electrical discharge machining (EDM)-treated surface under varying degrees of thermal deformation. Sample no. 4 with a deformation of 95.54 μm presented under (<b>a</b>) annular light and (<b>b</b>) coaxial light. Sample no. 33 with a deformation of 44.75 μm displayed under (<b>c</b>) annular light and (<b>d</b>) coaxial light [<a href="#B66-materials-17-01197" class="html-bibr">66</a>].</p> Full article ">Figure 13
<p>The innovative flushing mechanism implemented in the wire electro discharge machining (WEDM) by Farooq et al. [<a href="#B67-materials-17-01197" class="html-bibr">67</a>].</p> Full article ">Figure 14
<p>Interaction plots for material removal rate (MRR). (<b>a</b>) <span class="html-italic">T</span><sub>off</sub> vs. <span class="html-italic">T</span><sub>on</sub>; (<b>b</b>) <span class="html-italic">T</span><sub>on</sub> vs. <span class="html-italic">V</span><sub>g</sub>; (<b>c</b>) <span class="html-italic">V</span><sub>g</sub> vs. <span class="html-italic">I</span><sub>p</sub>; (<b>d</b>) <span class="html-italic">T</span><sub>on</sub> vs. <span class="html-italic">I</span><sub>p</sub> [<a href="#B68-materials-17-01197" class="html-bibr">68</a>].</p> Full article ">Figure 15
<p>High-frequency electrical discharge-assisted milling (HF-EDAM) based on copper-beryllium bundle electrodes: (<b>a</b>) electrical discharge machining (EDM) process in HF-EDAM, (<b>b</b>) composition of the depth of cut (<span class="html-italic">a</span><sub>p</sub>) after EDM and (<b>c</b>) milling process in HF-EDAM [<a href="#B60-materials-17-01197" class="html-bibr">60</a>].</p> Full article ">Figure 16
<p>Classification diagram of metal additive manufacturing (AM) processes, highlighting beam-based and beamless processes (adapted from [<a href="#B79-materials-17-01197" class="html-bibr">79</a>]).</p> Full article ">Figure 17
<p>A comparison of <span class="html-italic">R</span><sub>a</sub> values concerning the machining length between additively manufactured (AMed) and wrought INCONEL<sup>®</sup> 625 for different cutting environments: (<b>a</b>) dry; (<b>b</b>) electrostatic minimum quantity lubrication (EMQL); (<b>c</b>) CO<sub>2</sub> (<span class="html-italic">l</span>) [<a href="#B88-materials-17-01197" class="html-bibr">88</a>].</p> Full article ">Figure 18
<p>The roughness profiles and 3D topographies measured in the centre of the grooves (machining in building direction) [<a href="#B85-materials-17-01197" class="html-bibr">85</a>].</p> Full article ">Figure 19
<p>Interaction between laser-powder bed fusion (LPBF) and machining processes through orientation distribution function (ODF) patterns [<a href="#B92-materials-17-01197" class="html-bibr">92</a>].</p> Full article ">Figure 20
<p>(<b>a</b>) Evaluation of surface roughness (SR) in micro slots. (<b>b</b>) Measurement of burr width at slot edges [<a href="#B95-materials-17-01197" class="html-bibr">95</a>].</p> Full article ">Figure 21
<p>Comparison of surface roughness (SR) values for INCONEL<sup>®</sup> 625 alloy specimens, whether wrought or produced through wire arc additive manufacturing (WAAM), drilled using die-sinking micro-electrical discharge machining (EDM), micro-EDM drilling, orbital and conventional drilling methods [<a href="#B96-materials-17-01197" class="html-bibr">96</a>].</p> Full article ">Figure 22
<p>The tribocorrosion model is founded on the distinct structures of the examined materials, where stages I, II and III represent different phases in the material loss process [<a href="#B97-materials-17-01197" class="html-bibr">97</a>].</p> Full article ">Figure 23
<p>Scanning electron microscopy (SEM) images of <span class="html-italic">VB</span> were captured under different cutting conditions: P1, P9, P8, P16, P4, P12, P5, P13 for laser-assisted cutting, and C1, C8, C4, C5 for CT [<a href="#B102-materials-17-01197" class="html-bibr">102</a>].</p> Full article ">Figure 24
<p>Tool wear (TW) on machining INCONEL<sup>®</sup> 718 and 625 at <span class="html-italic">v</span><sub>c</sub> = 100 m/min, <span class="html-italic">f</span> = 0.13 mm/rev at room and heating <span class="html-italic">T</span> = 600 °C [<a href="#B103-materials-17-01197" class="html-bibr">103</a>].</p> Full article ">Figure 25
<p>Schematic of laser induction-assisted machining (LIAM) applied to the workpiece with a flat shape [<a href="#B104-materials-17-01197" class="html-bibr">104</a>].</p> Full article ">Figure 26
<p>Tool wear (TW) in INCONEL<sup>®</sup> 718 conventional manufacturing (CM) and induction-assisted machining (IAM) [<a href="#B105-materials-17-01197" class="html-bibr">105</a>].</p> Full article ">Figure 27
<p>The schematic diagram of induction-assisted machining (IAM) [<a href="#B107-materials-17-01197" class="html-bibr">107</a>].</p> Full article ">Figure 28
<p>Schematic diagram of (<b>a</b>) laser-assisted machining (LAM), (<b>b</b>) induction-assisted machining (IAM), (<b>c</b>) finite element analysis (FEA) model and (<b>d</b>) results of laser thermal induction; (<b>e</b>) FEA model and (<b>f</b>) results of magnetic induction (adapted from [<a href="#B110-materials-17-01197" class="html-bibr">110</a>]).</p> Full article ">Figure 29
<p>Conceptual diagram of (<b>a</b>) laser-assisted machining (LAM) and (<b>b</b>) LAM with heat shield, (<b>c</b>) thermal finite element analysis (FEA) on LAM, (<b>d</b>) thermal FEA on LAM with heat shield (adapted from [<a href="#B111-materials-17-01197" class="html-bibr">111</a>]).</p> Full article ">Figure 30
<p>Principle of laser belt processing (LBP) and preparation of a grooved surface: (<b>a</b>) pyramid abrasive; (<b>b</b>) belt grinding; (<b>c</b>) micro-groove structure ground by belt; (<b>d</b>) laser scanning trajectory; (<b>e</b>) laser processing; (<b>f</b>) microgroove structure processed by laser; (<b>g</b>) microgroove structure processed by laser belt; (<b>h</b>) laser belt processing; (<b>i</b>) laser belt processing process [<a href="#B112-materials-17-01197" class="html-bibr">112</a>].</p> Full article ">Figure 31
<p>Distribution of <span class="html-italic">T</span> and <span class="html-italic">σ</span><sub>y</sub> along the depth direction during laser scanning [<a href="#B113-materials-17-01197" class="html-bibr">113</a>].</p> Full article ">Figure 32
<p>Ultrasonic peening milling (UPM) process illustrated in a four-flute end milling cutter scheme (adapted from [<a href="#B117-materials-17-01197" class="html-bibr">117</a>]).</p> Full article ">Figure 33
<p>(<b>a</b>) Schematic representation of the ultrasonic-assisted turning (UAT) setup, (<b>b</b>,<b>c</b>) depiction of tool engagement and disengagement during the machining process, (<b>d</b>) a comprehensive comparison between conventional cutting and (<b>e</b>) high-speed ultrasonic vibration cutting (HUVC) within a single vibration cycle (adapted from [<a href="#B115-materials-17-01197" class="html-bibr">115</a>,<a href="#B116-materials-17-01197" class="html-bibr">116</a>]; caption: <span class="html-italic">T</span>—ultrasonic vibration period, <span class="html-italic">D</span><sub>c</sub>—duty cycle).</p> Full article ">Figure 34
<p>Comparison of surface topographies achieved through conventional manufacturing (CM) and ultrasonic peening milling (UPM) [<a href="#B119-materials-17-01197" class="html-bibr">119</a>].</p> Full article ">Figure 35
<p>CMed 3D surface topography of S1: (<b>a</b>) surface measurement topography, (<b>b</b>) stereoscopic topography and (<b>c</b>) detailed topography; <span class="html-italic">v</span><sub>c</sub> = 40 m/min, <span class="html-italic">s</span> = 2124 rpm [<a href="#B120-materials-17-01197" class="html-bibr">120</a>].</p> Full article ">Figure 36
<p>CMed 3D surface topography of S2: (<b>a</b>) surface measurement topography, (<b>b</b>) stereoscopic topography, and (<b>c</b>) detailed topography; <span class="html-italic">v</span><sub>c</sub> = 100 m/min, <span class="html-italic">s</span> = 5358 rpm [<a href="#B120-materials-17-01197" class="html-bibr">120</a>].</p> Full article ">Figure 37
<p>UPMed 3D surface topography of S3: (<b>a</b>) surface measurement topography, (<b>b</b>) stereoscopic topography, and (<b>c</b>) detailed topography; <span class="html-italic">v</span><sub>c</sub> = 100 m/min, <span class="html-italic">s</span> = 5358 rpm [<a href="#B120-materials-17-01197" class="html-bibr">120</a>].</p> Full article ">Figure 38
<p>Top section view (<b>a</b>) and cross-section view (<b>b</b>) of the <span class="html-italic">T</span> field induced by a laser rotating at 3500 rpm. Top section view (<b>c</b>) and cross-section view (<b>d</b>) at a rotational speed of 7000 rpm, featuring a 0.2 mm radius and x-directional moving speed of 1000 mm/min (trochoidal path, <span class="html-italic">T</span> is expressed in the unit of Kelvin) [<a href="#B125-materials-17-01197" class="html-bibr">125</a>].</p> Full article ">Figure 39
<p>Desirability condition <span class="html-italic">P</span><sub>water</sub> = 300 MPa, <span class="html-italic">G</span><sub>d</sub> = 1 mm, <span class="html-italic">T</span><sub>SP</sub> = 72 mm/min, and abrasive material is constituted by 100% SiC. (<b>a</b>) Scanning electron microscopy (SEM) image, (<b>b</b>) 3D surface image, (<b>c</b>) 2D roughness profile image [<a href="#B130-materials-17-01197" class="html-bibr">130</a>].</p> Full article ">Figure 40
<p>(<b>a</b>) Schematic of the magnetic abrasive finishing (similar to a honing operation) and the magnetic internal tool used, (<b>b</b>) zoomed-in schematic with force analysis model diagram (adapted from [<a href="#B132-materials-17-01197" class="html-bibr">132</a>]).</p> Full article ">Figure 41
<p>Microstructural characteristics and hardness variations from the surface to the core across the thickness of the specimens were investigated under various heat treatment (HT) and magnetic abrasive finishing (MAF) conditions: (<b>a</b>–<b>c</b>) orientation maps obtained through electron back-scattered diffraction (EBSD) observations, (<b>d</b>–<b>f</b>) corresponding grain orientation spread (GOS) maps derived from EBSD observations, (<b>g</b>) hardness progression from the surface, and (<b>h</b>) engineering stress–strain curves representing samples subjected to different post-processing conditions (adapted from [<a href="#B99-materials-17-01197" class="html-bibr">99</a>]).</p> Full article ">Figure 42
<p>Visual representations of specimens subjected to complete heat treatment prior to magnetic abrasive finishing (MAF) (heat treatment (HT) + A) and subsequent to the MAF process (HT + A + MAF): (<b>a</b>) surface appearance pre-MAF and (<b>b</b>) post-MAF; (<b>c</b>) surface section following electrical discharge machining (EDM) pre-MAF and (<b>d</b>) post-MAF [<a href="#B137-materials-17-01197" class="html-bibr">137</a>].</p> Full article ">Figure 43
<p>Surface morphology and elements of samples treated with different conditions (<b>a</b>) untreated, (<b>b</b>) treated with H<sub>2</sub>O, (<b>c</b>) treated with <span class="html-italic">wt</span> % = 20% emulsion, (<b>d</b>) treated with <span class="html-italic">wt</span> % = 40% emulsion [<a href="#B133-materials-17-01197" class="html-bibr">133</a>].</p> Full article ">Figure 44
<p>Grinding surface texture. (<b>a</b>) Conventional abrasive belt grinding (CABG) surface; (<b>b</b>) magnified view of CABG surface; (<b>c</b>) ultrasonic-assisted abrasive belt grinding (UAABG) surface; (<b>d</b>) magnified view of UAABG surface [<a href="#B134-materials-17-01197" class="html-bibr">134</a>].</p> Full article ">Figure 45
<p>Depth and force of different grinding depress depth under up-grinding conditions (<b>a1</b>–<b>d1</b>) 3D texture graphs, (<b>a2</b>–<b>d2</b>) cross-sectional profile of 2D texture, seen from Y-axis, (<b>a3</b>–<b>d3</b>) grinding forces according to X, Y and Z-axis [<a href="#B136-materials-17-01197" class="html-bibr">136</a>].</p> Full article ">Figure 46
<p>Depth and force of different grinding depress depth under down-grinding conditions (<b>a1</b>–<b>d1</b>) 3D texture graphs, (<b>a2</b>–<b>d2</b>) cross-sectional profile of 2D texture, seen from Y-axis, (<b>a3</b>–<b>d3</b>) grinding forces according to X, Y and Z-axis [<a href="#B136-materials-17-01197" class="html-bibr">136</a>].</p> Full article ">
28 pages, 9843 KiB  
Review
Photonic Crystal Structures for Photovoltaic Applications
by Anna Starczewska and Mirosława Kępińska
Materials 2024, 17(5), 1196; https://doi.org/10.3390/ma17051196 - 4 Mar 2024
Cited by 2 | Viewed by 2098
Abstract
Photonic crystals are artificial structures with a spatial periodicity of dielectric permittivity on the wavelength scale. This feature results in a spectral region over which no light can propagate within such a material, known as the photonic band gap (PBG). It leads to [...] Read more.
Photonic crystals are artificial structures with a spatial periodicity of dielectric permittivity on the wavelength scale. This feature results in a spectral region over which no light can propagate within such a material, known as the photonic band gap (PBG). It leads to a unique interaction between light and matter. A photonic crystal can redirect, concentrate, or even trap incident light. Different materials (dielectrics, semiconductors, metals, polymers, etc.) and 1D, 2D, and 3D architectures (layers, inverse opal, woodpile, etc.) of photonic crystals enable great flexibility in designing the optical response of the material. This opens an extensive range of applications, including photovoltaics. Photonic crystals can be used as anti-reflective and light-trapping surfaces, back reflectors, spectrum splitters, absorption enhancers, radiation coolers, or electron transport layers. This paper presents an overview of the developments and trends in designing photonic structures for different photovoltaic applications. Full article
(This article belongs to the Special Issue Advances in Photoelectric Materials: Preparation, Properties, and Applications)
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Figure 1

Figure 1
<p>Models of photonic crystals: (<b>a</b>) one-dimensional (1D), (<b>b</b>) two-dimensional (2D), (<b>c</b>) three-dimensional (3D). The different colors represent materials with various refractive indices.</p> Full article ">Figure 2
<p>The Bragg mirror scheme and the reflectance and transmission spectra calculated for the Bragg mirror consist of 10 pairs of layers 75 nm thick and a refractive index of 2.0 and layers 100 nm thick and a refractive index of 1.5 [<a href="#B32-materials-17-01196" class="html-bibr">32</a>].</p> Full article ">Figure 3
<p>Exemplary 2D photonic crystals: (<b>a</b>) hole-type and (<b>b</b>) rod-type. Crystal lattices presented in 2D PCs: (<b>c</b>) square, (<b>d</b>) hexagonal, and (<b>e</b>) “honeycomb”.</p> Full article ">Figure 4
<p>Examples of 3D PCs [<a href="#B33-materials-17-01196" class="html-bibr">33</a>]: (<b>a</b>) Yablonovite, consisting of a triangular system of holes prepared by drilling the slab at a specific angle; (<b>b</b>) woodpile, formed “layer by layer” by a stock of dielectric 1D bars with alternating orthogonal orientations; (<b>c</b>) opal, obtained by self-organization from monodisperse colloidal suspensions.</p> Full article ">Figure 5
<p>(<b>a</b>) Typical SEM micrograph of SiO<sub>2</sub> bare opal [<a href="#B54-materials-17-01196" class="html-bibr">54</a>] and (<b>b</b>) photonic bands calculated for SiO<sub>2</sub> bare opal compared with measured reflectance spectra for a normal incidence of light on a (111) surface [<a href="#B53-materials-17-01196" class="html-bibr">53</a>].</p> Full article ">Figure 6
<p>(<b>a</b>) Typical SEM micrograph of SbSI inverse opal; (<b>b</b>) photonic band structure of inverse opal calculated in the Γ-L direction with the PBG marked in grey; (<b>c</b>) reflection spectra of SbSI inverse opals registered in RT; spectra are vertically displaced for better clarity; the range of strongly absorbed wavelengths are marked with orange. Reprinted from [<a href="#B65-materials-17-01196" class="html-bibr">65</a>], Copyright (2020), with permission from Elsevier.</p> Full article ">Figure 7
<p>Different anti-reflective and light trapping surfaces: (<b>a</b>) interference thin film; (<b>b</b>) texturized thin film; (<b>c</b>) texturization in the form of a regular set of, e.g., micropyramids; (<b>d</b>) 1D photonic crystal; (<b>e</b>) rod-type 2D photonic crystal (<b>f</b>) hole-type 2D photonic crystal.</p> Full article ">Figure 8
<p>Different photonic crystal back reflectors: (<b>a</b>) 1D (DBR); (<b>b</b>) 1D with a reflection grating; (<b>c</b>) textured 1D; (<b>d</b>,<b>e</b>) 2D; (<b>f</b>) the combination of 1D and 2D; (<b>g</b>) 3D inverse opal.</p> Full article ">Figure 9
<p>(<b>a</b>) A 1D PC designed to reflect in the visible solar spectrum with the corresponding reflection spectrum; (<b>b</b>) comparison of the visible solar spectrum, PC transmittance (dashed red line), and silicon solar cell spectral response (blue dots) [<a href="#B99-materials-17-01196" class="html-bibr">99</a>]; (<b>c</b>) the scheme of SCs containing 1D PCs and their absorbance spectra calculated for different periods at λ<sub>B</sub> = 850 nm [<a href="#B103-materials-17-01196" class="html-bibr">103</a>]; and (<b>d</b>) variation in J<sub>ph</sub> according to the number of periods [<a href="#B103-materials-17-01196" class="html-bibr">103</a>]. <a href="#materials-17-01196-f009" class="html-fig">Figure 9</a>a,b are reproduced from [<a href="#B99-materials-17-01196" class="html-bibr">99</a>], licensed under a Creative Commons Attribution (CC BY) license, <a href="#materials-17-01196-f009" class="html-fig">Figure 9</a>c,d are reproduced from [<a href="#B103-materials-17-01196" class="html-bibr">103</a>], licensed under a Creative Commons Attribution (CC BY) license.</p> Full article ">Figure 10
<p>Schematic light propagation through a tandem solar cell structure with IRL.</p> Full article ">Figure 11
<p>Examples of PC structures in the active layer: (<b>a</b>) 1D grating based on [<a href="#B129-materials-17-01196" class="html-bibr">129</a>]; (<b>b</b>) double 1D grating based on [<a href="#B11-materials-17-01196" class="html-bibr">11</a>]; (<b>c</b>) double layer of 2D PCs based on [<a href="#B128-materials-17-01196" class="html-bibr">128</a>]; (<b>d</b>) double 2D PCs based on [<a href="#B116-materials-17-01196" class="html-bibr">116</a>]; (<b>e</b>) 2D lattice of cylinders based on [<a href="#B123-materials-17-01196" class="html-bibr">123</a>]; (<b>f</b>) 2D lattice of air cylinders based on [<a href="#B7-materials-17-01196" class="html-bibr">7</a>,<a href="#B127-materials-17-01196" class="html-bibr">127</a>]; (<b>g</b>) 2D PCs based on [<a href="#B124-materials-17-01196" class="html-bibr">124</a>]; (<b>h</b>) lattice of nanocones based on [<a href="#B131-materials-17-01196" class="html-bibr">131</a>]; (<b>i</b>) inverse opal based on [<a href="#B125-materials-17-01196" class="html-bibr">125</a>].</p> Full article ">Figure 12
<p>The PC is made by alternating deposition of SiO<sub>2</sub> nanoparticles and TiO<sub>2</sub> layers [<a href="#B140-materials-17-01196" class="html-bibr">140</a>]. Reproduced from [<a href="#B140-materials-17-01196" class="html-bibr">140</a>], licensed under an ACS Author Choice License.</p> Full article ">Figure 13
<p>(<b>a</b>) Crystalline silicon solar cell structures with no thermal emitter, an ideal thermal emitter, a uniform silica layer, and a uniform silica layer with 2D silica pyramids [<a href="#B159-materials-17-01196" class="html-bibr">159</a>]); (<b>b</b>) a comparison of emissivity/absorptivity spectra [<a href="#B159-materials-17-01196" class="html-bibr">159</a>]; and (<b>c</b>) the thermal scheme assumed by ref. [<a href="#B159-materials-17-01196" class="html-bibr">159</a>]. Reproduced from [<a href="#B159-materials-17-01196" class="html-bibr">159</a>], licensed under the Open Access Publishing Agreement.</p> Full article ">Figure 14
<p>(<b>a</b>) Diagram of a PDMS/SiO<sub>2</sub> radiative cooling system [<a href="#B176-materials-17-01196" class="html-bibr">176</a>]; (<b>b</b>) comparison of operating temperature as a function of heat transfer coefficients and (<b>c</b>) solar irradiance for different radiative cooling systems [<a href="#B176-materials-17-01196" class="html-bibr">176</a>]. Reproduced from [<a href="#B176-materials-17-01196" class="html-bibr">176</a>], licensed under Optica Open Access Publishing Agreement.</p> Full article ">Figure 15
<p>(<b>a</b>) Fabrication procedure of the inverse opal-like TiO<sub>2</sub> electron transport layer-based perovskite solar cells. [<a href="#B183-materials-17-01196" class="html-bibr">183</a>]; (<b>b</b>) absorption spectrum of the perovskite-coated TiO<sub>2</sub> inverse opal ETL film (red line) and conventional P25 mesoporous film (black line) on the FTO glass [<a href="#B183-materials-17-01196" class="html-bibr">183</a>]. Reproduced from [<a href="#B183-materials-17-01196" class="html-bibr">183</a>], licensed under a Creative Commons Attribution (CC BY 4.0) license.</p> Full article ">
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