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Materials, Volume 12, Issue 9 (May-1 2019) – 212 articles

Cover Story (view full-size image): Shear-transformation zones (STZ) are known to be a characteristic feature of plastic deformation in metallic glasses. Here, the activation of STZs during the unloading phase of a nanoindentation simulation was observed and characterized for the first time. These newly appearing STZs follow the same statistics as the clusters formed during loading. Moreover, during the unloading process, the deactivation of STZs formed during loading was also observed and characterized. Altogether these findings add a new perspective of the unloading mechanism. The figure shows the smallest 1000 STZs formed, ordered by size; the largest cluster is blue and the smallest cluster yellow. View this paper.
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22 pages, 10749 KiB  
Article
Properties of Alkali-Activated Slag Paste Using New Colloidal Nano-Silica Mixing Method
by Taewan Kim, Jae Hong Kim and Yubin Jun
Materials 2019, 12(9), 1571; https://doi.org/10.3390/ma12091571 - 13 May 2019
Cited by 18 | Viewed by 3457
Abstract
Previous studies of alkali-activated slag cement (AASC) using nano-silica have mentioned mostly powdered nano-silica and binder weight replacement methods, which have a rapid decrease in fluidity, a short setting time and a low nano-silica replacement rate (< 5%). In this study, colloidal nano-silica [...] Read more.
Previous studies of alkali-activated slag cement (AASC) using nano-silica have mentioned mostly powdered nano-silica and binder weight replacement methods, which have a rapid decrease in fluidity, a short setting time and a low nano-silica replacement rate (< 5%). In this study, colloidal nano-silica (CNS) was used and the mixing-water weight substitution method was applied. The substitution method was newly applied to improve the dispersibility of nano-silica and to increase the substitution rate. In the experiment, the CNS was replaced by 0, 10, 20, 30, 40, and 50% of the mixing-water weight. As a result, as the substitution rate of CNS increased, the fluidity decreased, and the setting time decreased. High compressive strength values and increased rates were also observed, and the diameter and volume of pores decreased rapidly. In particular, the increase of CNS replacement rate had the greatest effect on decrease of medium capillary pores (50–10 nm) and increase of gel pores (< 10 nm). The new displacement method was able to replace up to 50% of the mixing water. As shown in the experimental results, despite the high substitution rate of 50%, the minimum fluidity of the mixture was secured, and a high-strength and compact matrix could be formed. Full article
(This article belongs to the Special Issue Testing of Cement-Based Materials)
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Figure 1

Figure 1
<p>Particle analysis of slag.</p> Full article ">Figure 2
<p>Flow values according to CNS replacement ratios in 5% and 10% activators.</p> Full article ">Figure 3
<p>Setting times according to CNS replacement ratios in 5% and 10% activators.</p> Full article ">Figure 4
<p>Compressive strength: (<b>a</b>) 5% activator and (<b>b</b>) 10% activator samples.</p> Full article ">Figure 4 Cont.
<p>Compressive strength: (<b>a</b>) 5% activator and (<b>b</b>) 10% activator samples.</p> Full article ">Figure 5
<p>XRD analysis of hydration reactants: (<b>a</b>) 1-day, 5% activator samples (<b>b</b>) 28-day, 5% activator samples, (<b>c</b>) 1-day, 10% activator samples, (<b>d</b>) 28-day, 10% activator samples. M is monosulfate, C is calcite, CSH is C-S-H gel, Ht is hydrotalcite, Q is quartz, A is akermanite, S is stratlingite.</p> Full article ">Figure 5 Cont.
<p>XRD analysis of hydration reactants: (<b>a</b>) 1-day, 5% activator samples (<b>b</b>) 28-day, 5% activator samples, (<b>c</b>) 1-day, 10% activator samples, (<b>d</b>) 28-day, 10% activator samples. M is monosulfate, C is calcite, CSH is C-S-H gel, Ht is hydrotalcite, Q is quartz, A is akermanite, S is stratlingite.</p> Full article ">Figure 6
<p>MIP analysis: (<b>a</b>) 5% activator, 1-day, (<b>b</b>) 5% activator, 28-day, (<b>c</b>) 10% activator, 1-day, (<b>d</b>) 10% activator, 28-day.</p> Full article ">Figure 6 Cont.
<p>MIP analysis: (<b>a</b>) 5% activator, 1-day, (<b>b</b>) 5% activator, 28-day, (<b>c</b>) 10% activator, 1-day, (<b>d</b>) 10% activator, 28-day.</p> Full article ">Figure 7
<p>Total porosity of samples.</p> Full article ">Figure 8
<p>Thermal analysis (DTG): (<b>a</b>) 5% activator, (<b>b</b>) a magnification of less than 300 °C in (<b>a</b>), (<b>c</b>) 10% activator, (<b>d</b>) a magnification of less than 300 °C in (<b>c</b>).</p> Full article ">Figure 8 Cont.
<p>Thermal analysis (DTG): (<b>a</b>) 5% activator, (<b>b</b>) a magnification of less than 300 °C in (<b>a</b>), (<b>c</b>) 10% activator, (<b>d</b>) a magnification of less than 300 °C in (<b>c</b>).</p> Full article ">Figure 9
<p>SEM/BSE image of hydration products: (<b>a</b>) 5% activator, 0% CNS, (<b>b</b>) 5% activator, 20% CNS, (<b>c</b>) 5% activator, 50% CNS, (<b>d</b>) 10% activator, 0% CNS, (<b>e</b>) 10% activator, 20% CNS, (<b>f</b>) 10% activator, 50% CNS.</p> Full article ">Figure 9 Cont.
<p>SEM/BSE image of hydration products: (<b>a</b>) 5% activator, 0% CNS, (<b>b</b>) 5% activator, 20% CNS, (<b>c</b>) 5% activator, 50% CNS, (<b>d</b>) 10% activator, 0% CNS, (<b>e</b>) 10% activator, 20% CNS, (<b>f</b>) 10% activator, 50% CNS.</p> Full article ">Figure 9 Cont.
<p>SEM/BSE image of hydration products: (<b>a</b>) 5% activator, 0% CNS, (<b>b</b>) 5% activator, 20% CNS, (<b>c</b>) 5% activator, 50% CNS, (<b>d</b>) 10% activator, 0% CNS, (<b>e</b>) 10% activator, 20% CNS, (<b>f</b>) 10% activator, 50% CNS.</p> Full article ">
12 pages, 5268 KiB  
Article
Preparing Sodium Alginate/Polyethyleneimine Spheres for Potential Application of Killing Tumor Cells by Reducing the Concentration of Copper Ions in the Lesions of Colon Cancer
by Ru Xu, Chen Su, Longlong Cui, Kun Zhang and Jingan Li
Materials 2019, 12(9), 1570; https://doi.org/10.3390/ma12091570 - 13 May 2019
Cited by 23 | Viewed by 4417
Abstract
Inhibition of residual malignant tumors in patients with colon cancer after operation is one of the difficulties in rehabilitation treatment. At present, using biocompatible materials to remove the copper ion which is the growth dependence of malignant tumors in the lesion site is [...] Read more.
Inhibition of residual malignant tumors in patients with colon cancer after operation is one of the difficulties in rehabilitation treatment. At present, using biocompatible materials to remove the copper ion which is the growth dependence of malignant tumors in the lesion site is considered to be the frontier means to solve this problem. In this work, we developed a sodium alginate (SA)/polyethyleneimine (PEI) hydrogel sphere via cross-linking method (SA/SP/SA; SP = SA/PEI) as an oral biomaterial for adsorbing and removing copper ions from colon cancer lesions. The evaluated results showed that the SA/PEI/SA (SPS) hydrogel sphere obtained the largest swelling rate at pH 8.3 which was the acid-base value of colon microenvironment and absorbed more copper ions compared with the SA control. The cell experiment presented that the SPS hydrogel sphere owned better compatibility on normal fibroblasts and promoted higher death of colon cancer cells compared with SA/PEI (SP) and SA control. Our data suggested that the SA/PEI hydrogel sphere had the potentiality as an oral biomaterial for inhibiting colon cancer cells. Full article
(This article belongs to the Special Issue Biomaterials and Implant Biocompatibility)
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Figure 1
<p>Preparation of SA/PEI/SA (SPS) spheres. SA: sodium alginate; PEI: polyethyleneimine.</p> Full article ">Figure 2
<p>Fourier transform infrared (FTIR) spectra of PEI, SA and SPS samples.</p> Full article ">Figure 3
<p>Photographs of the abbreviation of Zhengzhou University, “ZZU”, which was composed of the SA (the first letter “Z”), SA/PEI (SP) (the second letter “Z”) and SPS (the third letter “U”) hydrogel spheres.</p> Full article ">Figure 4
<p>The (<b>a</b>) cross-section, (<b>b</b>) surface microstructure and (<b>c</b>) surface energy dispersive spectrum (EDS) of the SA, SP and SPS hydrogel sphere observed by scanning electron microscopy (SEM).</p> Full article ">Figure 5
<p>(<b>a</b>) The swelling ratio of the SPS hydrogel sphere after immersed in the phosphate buffer solution for 1 h, 2 h, 3 h, 4 h, 5 h, 6 h and 18 h in the condition of pH 1.2, pH 6.8, pH 7.4 and pH 8.3, separately; (<b>b</b>) the degradation ratio of the SPS hydrogel sphere for 0.5 h, 1 h, 2 h, 4 h, 8 h, 16 h, 24 h, 48 h and 72 h in the condition of pH 1.2, pH 6.8, pH 7.4 and pH 8.3, separately; (<b>c</b>) the swelling ratio of the SA, SP and SPS hydrogel spheres after immersion in the PBS solution in the condition of pH 1.2 for 4 h, and then pH 7.4 for 8 h, and finally pH 8.3 for 60 h. (mean ± SD, n = 5).</p> Full article ">Figure 6
<p>The ability of the SPS, SP and SA hydrogel spheres to absorb copper ions at pH 8.3 (mean ± SD, n = 5).</p> Full article ">Figure 7
<p>Acridine orange (AO) and propidium iodide (PI) staining images of L929 cell in the SPS, SP, SA and control (CON) groups. (The green dots stained by AO indicate living cells, and the red dots stained by PI indicate dead or dying cells).</p> Full article ">Figure 8
<p>Inhibition rate of the SPS, SP and SA hydrogel spheres on the L929 cells (* <span class="html-italic">p</span> &lt; 0.05, mean ± SD, n = 3).</p> Full article ">Figure 9
<p>AO and PI staining images of colon cancer cells in the SPS, SP, SA and CON groups. (The green dots stained by AO indicate living cells, and the red dots stained by PI indicate dead or dying cells).</p> Full article ">Figure 10
<p>Inhibition rate of the SPS, SP and SA hydrogel spheres on the colon cancer cells (* <span class="html-italic">p</span> &lt; 0.05).</p> Full article ">
15 pages, 3326 KiB  
Article
Physical Hydrogels of Oxidized Polysaccharides and Poly(Vinyl Alcohol) for Wound Dressing Applications
by Raluca Ioana Baron, Madalina Elena Culica, Gabriela Biliuta, Maria Bercea, Simona Gherman, Daniela Zavastin, Lacramioara Ochiuz, Mihaela Avadanei and Sergiu Coseri
Materials 2019, 12(9), 1569; https://doi.org/10.3390/ma12091569 - 13 May 2019
Cited by 47 | Viewed by 4622
Abstract
Two natural polymers, i.e., cellulose and water soluble pullulan, have been selectively oxidized employing the TEMPO-mediated protocol, to allow the introduction of C6-OOH groups. Thereafter, the composite hydrogels of poly(vinyl alcohol) (PVA) and different content of the oxidized polysaccharides were prepared [...] Read more.
Two natural polymers, i.e., cellulose and water soluble pullulan, have been selectively oxidized employing the TEMPO-mediated protocol, to allow the introduction of C6-OOH groups. Thereafter, the composite hydrogels of poly(vinyl alcohol) (PVA) and different content of the oxidized polysaccharides were prepared by the freezing/thawing method. The Fourier transform infrared spectroscopy (FTIR) has been used to discuss the degree of interaction between the hydrogels constituents into the physical network. The homogeneity of the prepared hydrogels as revealed by the SEM show an excellent distribution of the oxidized polysaccharides inside the PVA matrix. The samples exhibit self-healing features, since they quickly recover the initial structure after being subjected to a large deformation. The cell viability was performed for the selected hydrogels, all of them showing promising results. The samples are able to load L-arginine both by physical phenomena, such as diffusion, and also by chemical phenomena, when imine-type bonds are likely to be formed. The synergism between the two constituents, PVA and oxidized polysaccharides, into the physical network, propose these hydrogels for many other biomedical applications. Full article
(This article belongs to the Special Issue Research Advances in Natural Polymer-Based Hydrogels)
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Figure 1
<p>General scheme for the oxidation of pullulan and cellulose, performed in the presence of TEMPO, NaClO, NaBr and sodium periodate, respectively.</p> Full article ">Figure 2
<p>The fingerprint region of attenuated total reflection (ATR)-FTIR spectra of the poly(vinyl alcohol) (PVA) hydrogels, in comparison with the neat PVA and OxP/OxC: (<b>a</b>) OxP-PVA; (<b>b</b>) OxC-PVA.</p> Full article ">Figure 3
<p>SEM microphotographs (2000× magnification) of cross-sections of PVA hydrogels containing 0.5%, 5%, 10% and 20% oxidized pullulan (OxP 0.5, OxP 5, OxP 10, OxP 20) and tricarboxy cellulose (OxC 0.5, OxC 5, OxC 10, OxC 20), respectively.</p> Full article ">Figure 4
<p>Swelling behavior of PVA hydrogels containing 0.5%, 5%, 10% and 20% oxidized pullulan (OxP 0.5, OxP 5, OxP 10, OxP 20) and tricarboxy cellulose (OxC 0.5, OxC 5, OxC 10, OxC 20), respectively.</p> Full article ">Figure 5
<p>The viscoelastic moduli (G’ and G”) as a function of the oscillation frequency for hydrogels with 10% OxC (red full symbols) and 5% OxP (blue open symbols) at 25 °C (γ = 1%).</p> Full article ">Figure 6
<p>(<b>a</b>) Elastic modulus (G’) and (<b>b</b>) complex viscosity (η*) for the investigated samples with different content of oxidized polysaccharides (% Oxy) at 25 °C (ω = 1 rad/s, γ = 1%).</p> Full article ">Figure 7
<p>Self-healing behavior of OxC 10 and OxP 5 hydrogels when successive strains of 1% and 400% were applied (ω = 1 rad/s, 25 °C).</p> Full article ">Figure 8
<p>The behavior of OxC 10 and OxP 5 samples in creep and recovery tests: (<b>a</b>) A shear stress of 50 Pa was applied during the creep test; (<b>b</b>) the total elastic recovery (γ<sub>rec</sub>, %) as a function of the applied shear stress during creep test for OxC 10 and OxP 5 hydrogels.</p> Full article ">Figure 9
<p>The most significant results of the cytotoxicity evaluation, performed on the PVA/carboxylated polysaccharide hydrogels by using the MTT assay.</p> Full article ">Figure 10
<p>The most relevant curves showing the in vitro profile of L-arginine from the investigated hydrogels.</p> Full article ">
10 pages, 5676 KiB  
Article
In-Situ Observation of Fracture Behavior of Ti-Aluminide Multi-Layered Composites Produced by a Hybrid Sintering Process
by Xiong Wan, Kai Zhu, Yanjin Xu, Baoshuai Han and Tao Jing
Materials 2019, 12(9), 1568; https://doi.org/10.3390/ma12091568 - 13 May 2019
Cited by 5 | Viewed by 2664
Abstract
The fabrication of Ti-aluminide multi-layered composites have attracted great attention for their excellent mechanical properties, such as high specific strength, high specific stiffness, tolerable toughness, and low density. The preparation of the composite produced by a hybrid procedure composed of Vacuum Hot Pressing [...] Read more.
The fabrication of Ti-aluminide multi-layered composites have attracted great attention for their excellent mechanical properties, such as high specific strength, high specific stiffness, tolerable toughness, and low density. The preparation of the composite produced by a hybrid procedure composed of Vacuum Hot Pressing (VHP) and Hot Isostatic Pressing (HIP) using Ti foils and Al foils has been performed. Further, X-Ray Diffraction (XRD) and Scanning Electron Microscopy (SEM) equipped with Energy Dispersive X-ray Spectrometry (EDXS) were carried out to identify the microstructure and phase formation of the composite. In addition, an in-situ three-point bending test was conducted on the notched specimen to observe the crack propagation behavior carefully. The results indicate that the densified composite was obtained without any apparent voids and pores which could undesirably develop into the source of cracks. Furthermore, all the pure Al foils were totally consumed to form a series of the Ti-Al compounds through the diffusive reaction between the adjacent Ti and Al foils. Moreover, the in-situ observation demonstrates the initiation and propagation of cracks in the intermetallic layers and the role of residual Ti layers to blunt and bridge the cracks by their plastic deformation. This study provides a new strategy for fabricating the Ti-aluminide multi-layered composites. Full article
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Figure 1

Figure 1
<p>Schematic sequence of stacking of the elemental components.</p> Full article ">Figure 2
<p>Schematic illustration of the hybrid processing technology.</p> Full article ">Figure 3
<p>(<b>a</b>) Dimensions of the examined sample, (<b>b</b>) schematic illustration of the experimental stage in a vacuum chamber, and (<b>c</b>) initial morphologies of the area near the notch of the sample.</p> Full article ">Figure 4
<p>Typical microstructure of the as-received specimen.</p> Full article ">Figure 5
<p>(<b>a</b>) Typical back-scattered electron (BSE) image of the Ti-Al reaction zone and Energy Dispersive X-ray Spectrometry (EDXS) linescan analysis results, (<b>b</b>) X-Ray Diffraction (XRD) pattern of this composite.</p> Full article ">Figure 6
<p>Load-displacement curve of the in-situ three-point bending test.</p> Full article ">Figure 7
<p>Scanning Electron Microscopy (SEM) micrographs of the in-situ three-point bending test corresponding to the first part of the Load-displacement curve representing the cracks nucleation and propagation process: (<b>a</b>,<b>b</b>) represent the detailed deformation morphologies of the specimen corresponding to the ”Point a” in <a href="#materials-12-01568-f006" class="html-fig">Figure 6</a>, showing several cracks initiated and propagated within the brittle intermetallic layers; (<b>c</b>–<b>f</b>) correspond to “Point b” in <a href="#materials-12-01568-f006" class="html-fig">Figure 6</a>, showing the crack bridging, slipping bands of Ti layers and more micro-cracks in intermetallic layers; (<b>g</b>,<b>h</b>) correspond to “Point c” in <a href="#materials-12-01568-f006" class="html-fig">Figure 6</a>, showing the shearing band in Ti layers and thorough fracture of the intermetallic layers; (<b>i</b>,<b>j</b>) correspond to “Point d” in <a href="#materials-12-01568-f006" class="html-fig">Figure 6</a>, showing the thorough fracture of the local Ti layers and Intermetallic layers.</p> Full article ">Figure 8
<p>SEM micrographs of the in-situ three-point bending test corresponding to the second part of the Load-displacement curve representing the cracks propagation process and the final morphologies of the specimen after catastrophic fracture:(<b>a</b>,<b>b</b>) represents the detailed deformation morphologies of the specimen corresponding to the ”Point e” in <a href="#materials-12-01568-f006" class="html-fig">Figure 6</a>, showing lots of micro-cracks formed before the novel main crack exposure; (<b>c</b>–<b>e</b>) correspond to “Point f” in <a href="#materials-12-01568-f006" class="html-fig">Figure 6</a>, showing the distribution of micro-cracks with the mushroom shape; (<b>f</b>,<b>g</b>) correspond to “Point g” in <a href="#materials-12-01568-f006" class="html-fig">Figure 6</a>, showing the “zigzag” propagation of the main crack</p> Full article ">
20 pages, 2444 KiB  
Article
Improved Method for Measuring the Permeability of Nanoporous Material and Its Application to Shale Matrix with Ultra-Low Permeability
by Taojie Lu, Ruina Xu, Bo Zhou, Yichuan Wang, Fuzhen Zhang and Peixue Jiang
Materials 2019, 12(9), 1567; https://doi.org/10.3390/ma12091567 - 13 May 2019
Cited by 21 | Viewed by 3752
Abstract
Nanoporous materials have a wide range of applications in clean energy and environmental research. The permeability of nanoporous materials is low, which affects the fluid transport behavior inside the nanopores and thus also affects the performance of technologies based on such materials. For [...] Read more.
Nanoporous materials have a wide range of applications in clean energy and environmental research. The permeability of nanoporous materials is low, which affects the fluid transport behavior inside the nanopores and thus also affects the performance of technologies based on such materials. For example, during the development of shale gas resources, the permeability of the shale matrix is normally lower than 10−3 mD and has an important influence on rock parameters. It is challenging to measure small pressure changes accurately under high pressure. Although the pressure decay method provides an effective means for the measurement of low permeability, most apparatuses and experiments have difficulty measuring permeability in high pressure conditions over 1.38 MPa. Here, we propose an improved experimental method for the measurement of low permeability. To overcome the challenge of measuring small changes in pressure at high pressure, a pressure difference sensor is used. By improving the constant temperature accuracy and reducing the helium leakage rate, we measure shale matrix permeabilities ranging from 0.05 to 2 nD at pore pressures of up to 8 MPa, with good repeatability and sample mass irrelevance. The results show that porosity, pore pressure, and moisture conditions influence the matrix permeability. The permeability of moist shale is lower than that of dry shale, since water blocks some of the nanopores. Full article
(This article belongs to the Special Issue Micro/Nano Materials for Clean Energy and Environment)
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Figure 1

Figure 1
<p>Graphical representation of the characteristic Equation (11). The solid lines represent the tangent function of <span class="html-italic">ϕ</span> and the dotted lines represent the fraction with different values of the non-dimensional number <span class="html-italic">f</span>. The red circles represent the characteristic roots of Equation (11). As <span class="html-italic">f</span> decreases, each characteristic root tends to be a positive integer multiple of π.</p> Full article ">Figure 2
<p>The truncation result of the analytic solution. The solid line represents the result of the truncation for the first 100 characteristic roots of Equation (11) and the dotted line represents the result of the truncation for the first characteristic root. When the dimensionless time is greater than 0.1, there is little difference between the two curves.</p> Full article ">Figure 3
<p>Schematic diagram of the experimental system used for the measurement of shale matrix particle permeability. Shale particle samples are placed in the sample chamber, and a reference chamber with approximately the same volume as the sample chamber is used for gas buffering. The electrical valve C is automatically controlled by the computer. The whole system is placed in a thermostatic water bath to maintain a constant temperature.</p> Full article ">Figure 4
<p>Graphs of the pressure <span class="html-italic">p</span>(<span class="html-italic">t</span>) of the reference chamber and sample chamber, the pressure difference signal Δ<span class="html-italic">p</span>(<span class="html-italic">t</span>) measured by the differential pressure transducer, and the gas temperature <span class="html-italic">T</span>(<span class="html-italic">t</span>) in the pipe.</p> Full article ">Figure 5
<p>The results of the repeatability experiment, involving five trials, using sample 1 under pressures of 1–8 MPa.</p> Full article ">Figure 6
<p>(<b>a</b>) The pressure difference signal Δp(<span class="html-italic">t</span>) and (<b>b</b>) logarithmic pressure decay curve for sample 1 measured at a pressure of 3 MPa and a temperature of 30 °C The black, red, and blue lines indicate sample masses of 6, 10, and 14 g, respectively.</p> Full article ">Figure 7
<p>The permeability values of four groups of shale samples for sample masses of 6, 10, and 14 g measured under a pressure of 3 MPa and a temperature of 30 °C.</p> Full article ">Figure 8
<p>Matrix permeability of four shale particle samples under different pressures. The dotted line is the result of the fitting by the Klinkenberg equation.</p> Full article ">Figure 9
<p>Rarefied gas flow type under different conditions. This can be divided into free molecular flow (<span class="html-italic">K<sub>n</sub></span> &gt; 10), transition flow (0.1 &lt; <span class="html-italic">K<sub>n</sub></span> &lt; 10), slip flow (10<sup>−3</sup> &lt; <span class="html-italic">K<sub>n</sub></span> &lt; 0.1), and continuous flow (<span class="html-italic">K<sub>n</sub></span> &lt; 10<sup>−3</sup>).</p> Full article ">Figure 10
<p>Transverse relaxation amplitude of shale particle sample 1 detected by low-field Nuclear Magnetic Resonance. The <span class="html-italic">T</span><sub>2</sub> measuring sequence is CPMG.</p> Full article ">Figure 11
<p>Matrix permeability of dry and moist (1.5% water) samples of shale sample 1 under different pressures. (<b>a</b>) Matrix permeability vs. pressure. The dotted lines are the results of fitting using the Klinkenberg equation. (<b>b</b>) Matrix permeability vs. 1/<span class="html-italic">p</span>.</p> Full article ">Figure 12
<p>The relative error in the calculated permeability due to ignoring gas compressibility. For systems with a smaller dimensionless number <span class="html-italic">f</span>, when the system initial pressure ratio is large, ignoring the gas compressibility leads to a larger error in the calculated permeability.</p> Full article ">Figure 13
<p>A comparison of the permeability fitting using the general slip regime (GSR) model and the Klinkenberg model. The characteristic flow scales <span class="html-italic">l<sub>f</sub></span> used for the fitting with the GSR model were 100, 200, and 500 nm.</p> Full article ">Figure A1
<p>Pressure difference signal (Δp(<span class="html-italic">t</span>)) for shale particle sample 1 measured by the differential pressure transducer under pressures of 1–8 MPa. (<b>a</b>) average pore pressure under 1–4 MPa with smaller Δp<span class="html-italic"><sub>f</sub></span>; (<b>b</b>) average pore pressure under 5–8 MPa with larger Δp<span class="html-italic"><sub>f</sub></span>.</p> Full article ">Figure A2
<p>Logarithmic pressure decay curve, ln(Δp<span class="html-italic"><sub>f</sub></span>-Δp(<span class="html-italic">t</span>)), for shale particle sample 1 under pressures of 1–8 MPa. (<b>a</b>) average pore pressure under 1–4 MPa; (<b>b</b>) average pore pressure under 5–8 MPa.</p> Full article ">Figure A3
<p>Nitrogen adsorption of sample 1 measured by an ASAP 2420 instrument (Micromeritics Instrument Corp., Norcross, GA, USA). (<b>a</b>) Langmuir surface area plot; (<b>b</b>) BJH desorption dV/dlog(D) pore volume.</p> Full article ">Figure A4
<p>Nitrogen adsorption of sample 2 measured by an ASAP 2420 instrument (Micromeritics). (<b>a</b>) Langmuir surface area plot. (<b>b</b>) BJH desorption dV/dlog(D) pore volume.</p> Full article ">Figure A5
<p>Nitrogen adsorption of sample 3 measured by an ASAP 2420 instrument (Micromeritics). (<b>a</b>) Langmuir surface area plot; (<b>b</b>) BJH desorption dV/dlog(D) pore volume.</p> Full article ">Figure A6
<p>Nitrogen adsorption of sample 4 measured by an ASAP 2420 instrument (Micromeritics). (<b>a</b>) Langmuir surface area plot; (<b>b</b>) BJH desorption dV/dlog(D) pore volume.</p> Full article ">
12 pages, 2957 KiB  
Article
Influence of Randomness in Rubber Materials Parameters on the Reliability of Rubber O-Ring Seal
by Banglong Liang, Xi Yang, Zili Wang, Xing Su, Baopeng Liao, Yi Ren and Bo Sun
Materials 2019, 12(9), 1566; https://doi.org/10.3390/ma12091566 - 13 May 2019
Cited by 20 | Viewed by 4288
Abstract
The properties of materials directly affect the performance of the sealing structures, among which the rubber O-ring seal is one of the most commonly used. In addition, the performance of the O-ring seal is often influenced by the randomness in structure and working [...] Read more.
The properties of materials directly affect the performance of the sealing structures, among which the rubber O-ring seal is one of the most commonly used. In addition, the performance of the O-ring seal is often influenced by the randomness in structure and working conditions, which greatly reduce the reliability of the sealing structure. This paper proposes a reliability-based method to analyze the influence of the randomness in rubber material parameters on the sealing performance of the O-ring. Based on the failure mechanism of the O-ring seal, the stochastic characteristics of the parameters in O-rings are determined through experiments, and the influences of these parameters on the reliability are subsequently analyzed. Moreover, the working conditions are also taken into account to analyze their influence on the performance and reliability of the O-ring seal. The proposed method provides easy access to estimate the reliability of the rubber O-ring seal considering the uncertainty in structure and operational conditions. It is revealed that the material and geometric parameters had greater influence on the reliability of the rubber O-ring. Full article
(This article belongs to the Section Advanced Materials Characterization)
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<p>Geometry model of a rubber O-ring seal.</p> Full article ">Figure 2
<p>(<b>a</b>) Aging test chamber and (<b>b</b>) rubber samples.</p> Full article ">Figure 3
<p>Finite element model of the O-ring.</p> Full article ">Figure 4
<p>(<b>a</b>) Compressive stress and (<b>b</b>) contact stress distribution nephograms.</p> Full article ">Figure 4 Cont.
<p>(<b>a</b>) Compressive stress and (<b>b</b>) contact stress distribution nephograms.</p> Full article ">Figure 5
<p>Distribution of (<b>a</b>) compressive stress and (<b>b</b>) contact stress.</p> Full article ">Figure 6
<p>(<b>a</b>) Contact stress and (<b>b</b>) reliability with varying <math display="inline"><semantics> <mrow> <msub> <mi>C</mi> <mrow> <mn>10</mn> </mrow> </msub> </mrow> </semantics></math>.</p> Full article ">Figure 7
<p>(<b>a</b>) Contact stress and (<b>b</b>) reliability with varying <math display="inline"><semantics> <mrow> <msub> <mi>C</mi> <mrow> <mn>01</mn> </mrow> </msub> </mrow> </semantics></math>.</p> Full article ">Figure 8
<p>(<b>a</b>) Compressive stress and (<b>b</b>) reliability with varying compression quantity <math display="inline"><semantics> <mrow> <mo>Δ</mo> <mi>r</mi> </mrow> </semantics></math>.</p> Full article ">Figure 9
<p>Reliability varying with the (<b>a</b>) mean and (<b>b</b>) variance of oil pressure.</p> Full article ">
13 pages, 4714 KiB  
Article
Effects of Citric Acid on Structures and Properties of Thermoplastic Hydroxypropyl Amylomaize Starch Films
by Yang Qin, Wentao Wang, Hui Zhang, Yangyong Dai, Hanxue Hou and Haizhou Dong
Materials 2019, 12(9), 1565; https://doi.org/10.3390/ma12091565 - 13 May 2019
Cited by 27 | Viewed by 4263
Abstract
Hydroxypropyl amylomaize starch (HPAS) films were prepared by hot press. The effects of initial pH of HPAS on the mechanical properties, molecular interaction, structure, and cross-linking degree of the resultant films were investigated. A weak acidic condition was suitable for cross-linking of citric [...] Read more.
Hydroxypropyl amylomaize starch (HPAS) films were prepared by hot press. The effects of initial pH of HPAS on the mechanical properties, molecular interaction, structure, and cross-linking degree of the resultant films were investigated. A weak acidic condition was suitable for cross-linking of citric acid and HPAS by reactive extrusion. The film of HPAS with an initial pH of 5.66 had the maximum tensile strength of 7.20 MPa and elongation-at-break of 94.53%, and the weight average molecular weight of HPAS increased to 4.17 × 105 g/mol. An appropriate initial pH facilitated the formation of diester bonds between HPAS and citric acid during extrusion, but too low initial pH levels resulted in hydrolysis of starch molecules and reduced the mechanical properties. Full article
(This article belongs to the Special Issue Novel Biodegradable and Renewable Polymer-Based Nanohybrids and Applications)
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<p>Images of HPAS-CA films with different citric acid amount.</p> Full article ">Figure 2
<p>Tensile strength and elongation-at-break of HPAS-CA films with different citric acid amount. Bars sharing the same letter are not significantly different (<span class="html-italic">p</span> &lt; 0.05, same in the other figures).</p> Full article ">Figure 3
<p>Thickness of HPAS-CA films with different citric acid amount.</p> Full article ">Figure 4
<p>SEM images of HPAS-CA films with different citric acid amount at 2000× magnification.</p> Full article ">Figure 4 Cont.
<p>SEM images of HPAS-CA films with different citric acid amount at 2000× magnification.</p> Full article ">Figure 5
<p>XRD patterns of HPAS-CA films with different citric acid amount.</p> Full article ">Figure 6
<p>Attenuated total reflectance Fourier-transform infrared (ATR-FTIR) spectra of HPAS-CA films with different citric acid amount.</p> Full article ">Figure 7
<p>Fitting of peaks to the HPAS-CA films at ~1500–1800 cm<sup>−1</sup>: The experimental spectra are denoted by (—) and fitted peaks by (– – –).</p> Full article ">Figure 8
<p>Reaction of citric acid and hydroxypropyl high amylomaize starch under various pH by melting extrusion.</p> Full article ">Figure 9
<p><sup>13</sup>C solid-state nuclear magnetic resonance (SSNMR) spectrum of HPAS-CA films with different citric acid amount.</p> Full article ">
16 pages, 3168 KiB  
Article
In Situ Surface-Enhanced Raman Spectroscopy of Cellular Components: Theory and Experimental Results
by Mario D’Acunto
Materials 2019, 12(9), 1564; https://doi.org/10.3390/ma12091564 - 13 May 2019
Cited by 9 | Viewed by 3341
Abstract
In the last decade, surface-enhanced Raman spectroscopy (SERS) met increasing interest in the detection of chemical and biological agents due to its rapid performance and ultra-sensitive features. Being SERS a combination of Raman spectroscopy and nanotechnology, it includes the advantages of Raman spectroscopy, [...] Read more.
In the last decade, surface-enhanced Raman spectroscopy (SERS) met increasing interest in the detection of chemical and biological agents due to its rapid performance and ultra-sensitive features. Being SERS a combination of Raman spectroscopy and nanotechnology, it includes the advantages of Raman spectroscopy, providing rapid spectra collection, small sample sizes, characteristic spectral fingerprints for specific analytes. In addition, SERS overcomes low sensitivity or fluorescence interference that represents two major drawbacks of traditional Raman spectroscopy. Nanoscale roughened metal surfaces tremendously enhance the weak Raman signal due to electromagnetic field enhancement generated by localized surface plasmon resonances. In this paper, we detected label-free SERS signals for arbitrarily configurations of dimers, trimers, etc., composed of gold nanoshells (AuNSs) and applied to the mapping of osteosarcoma intracellular components. The experimental results combined to a theoretical model computation of SERS signal of specific AuNSs configurations, based on open cavity plasmonics, give the possibility to quantify SERS enhancement for overcoming spectral fluctuations. The results show that the Raman signal is locally enhanced inside the cell by AuNSs uptake and correspondent geometrical configuration generating dimers are able to enhance locally electromagnetic fields. The SERS signals inside such regions permit the unequivocal identification of cancer-specific biochemical components such as hydroxyapatite, phenylalanine, and protein denaturation due to disulfide bonds breaking between cysteine links or proline. Full article
(This article belongs to the Special Issue Vibrational Spectroscopy for Biomedical Materials Analysis)
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Graphical abstract

Graphical abstract
Full article ">Figure 1
<p>Transmission electron microscopy image of the gold nanoshells (AuNSs) (<b>a</b>); correspondent size distribution (<b>b</b>).</p> Full article ">Figure 2
<p>Averaged Raman spectra collected upon osteo-differentiated mesenchymal stem cells (MSCs) nucleus, blue line, and correspondent spectra collected upon MG-63 nucleus, black line.</p> Full article ">Figure 3
<p>First two principal component (PC)1,2 loading plots.</p> Full article ">Figure 4
<p>Raman chemical maps of a MG-63 cell and an osteo-differentiated MSC. The images a and c represent the cell morphologies with the red box denoting the area under Raman investigation for MG-63 (<b>a</b>) and osteo-differentiated MSC (<b>c</b>), respectively. The images A (area 30 × 40 μm<sup>2</sup>) and C (scale bar 50 μm) were recorded making use of 50× magnification. The images B and D represent the chemical Raman imaging for the MG-63 (<b>b</b>) and the osteo-differentiated MSC (<b>d</b>), respectively, reporting the correspondent distribution of HA (960 cm<sup>−1</sup>). Under the experimental setup adopted, the chemical Raman maps were collected with steps of nearly 1 μm.</p> Full article ">Figure 5
<p>(<b>a</b>) SEM image of a cluster of MG-63 cells, the bright dots denote the AuNSs, scale bar 100 μm. (<b>b</b>) Dark-field illumination at 100× magnification on the DXR Raman microscope of a MG-63 cell crowded by gold nanoshells (AuNSs). The area under investigation is denoted by the red borders, scale bar 10 μm.</p> Full article ">Figure 6
<p>(<b>a</b>) Denotes the bright-field image of MG-63 nuclear area where the bright points display the AuNSs, scale bar 1 μm, (<b>b</b>) represents the correspondent Raman map of the area marked by the red box in (<b>a</b>). The labels 1 and 2 mark a non-SERS and a SERS domain characterized by the AuNSs dimer. (<b>c</b>) Shows the Raman map calculated with Green’s function: the red regions denotes the spatial areas with Γ<sup>2</sup>~10<sup>5</sup>. (<b>d</b>) Displays the Raman spectra in the recorded Raman map, label 1 (blue line), label 2 (red line) and in 2 after data processed with simulated map (<b>c</b>), black line.</p> Full article ">Figure 6 Cont.
<p>(<b>a</b>) Denotes the bright-field image of MG-63 nuclear area where the bright points display the AuNSs, scale bar 1 μm, (<b>b</b>) represents the correspondent Raman map of the area marked by the red box in (<b>a</b>). The labels 1 and 2 mark a non-SERS and a SERS domain characterized by the AuNSs dimer. (<b>c</b>) Shows the Raman map calculated with Green’s function: the red regions denotes the spatial areas with Γ<sup>2</sup>~10<sup>5</sup>. (<b>d</b>) Displays the Raman spectra in the recorded Raman map, label 1 (blue line), label 2 (red line) and in 2 after data processed with simulated map (<b>c</b>), black line.</p> Full article ">Figure 7
<p>The labels (<b>a</b>), (<b>b</b>), and (<b>c</b>) as in <a href="#materials-12-01564-f006" class="html-fig">Figure 6</a>, in a nuclear area (5 μm × 5 μm) of a MG-63 cell, in <a href="#materials-12-01564-f006" class="html-fig">Figure 6</a>c red region denotes Γ<sup>2</sup>~10<sup>5</sup>. (<b>d</b>) Represents the correspondent spectra in 1 (blue line), 2 (green line), and in 2 after SERS map (red line).</p> Full article ">Figure 7 Cont.
<p>The labels (<b>a</b>), (<b>b</b>), and (<b>c</b>) as in <a href="#materials-12-01564-f006" class="html-fig">Figure 6</a>, in a nuclear area (5 μm × 5 μm) of a MG-63 cell, in <a href="#materials-12-01564-f006" class="html-fig">Figure 6</a>c red region denotes Γ<sup>2</sup>~10<sup>5</sup>. (<b>d</b>) Represents the correspondent spectra in 1 (blue line), 2 (green line), and in 2 after SERS map (red line).</p> Full article ">
11 pages, 3163 KiB  
Article
Ultra-Thin ReS2 Nanosheets Grown on Carbon Black for Advanced Lithium-Ion Battery Anodes
by Yaping Yan, Kyeong-Youn Song, Minwoo Cho, Tae Hoon Lee, Chiwon Kang and Hoo-Jeong Lee
Materials 2019, 12(9), 1563; https://doi.org/10.3390/ma12091563 - 13 May 2019
Cited by 7 | Viewed by 3770
Abstract
ReS2 nanosheets are grown on the surface of carbon black (CB) via an efficient hydrothermal method. We confirmed the ultra-thin ReS2 nanosheets with ≈1–4 layers on the surface of the CB (ReS2@CB) by using analytical techniques of field emission [...] Read more.
ReS2 nanosheets are grown on the surface of carbon black (CB) via an efficient hydrothermal method. We confirmed the ultra-thin ReS2 nanosheets with ≈1–4 layers on the surface of the CB (ReS2@CB) by using analytical techniques of field emission scanning electron microscopy (FESEM) and high-resolution transmission electron microscopy (HRTEM). The ReS2@CB nanocomposite showed high specific capacities of 760, 667, 600, 525, and 473 mAh/g at the current densities of 0.1 (0.23 C), 0.2 (0.46 C), 0.3 (0.7 C), 0.5 (1.15 C) and 1.0 A/g (2.3 C), respectively, in conjunction with its excellent cycling performance (432 mAh/g at 2.3 C; 91.4% capacity retention) after 100 cycles. Such LIB performance is greatly higher than pure CB and ReS2 powder samples. These results could be due to the following reasons: (1) the low-cost CB serves as a supporter enabling the formation of ≈1–4 layered nanosheets of ReS2, thus avoiding its agglomeration; (2) the CB enhances the electrical conductivity of the ReS2@CB nanocomposite; (3) the ultra-thin (1–4 layers) ReS2 nanosheets with imperfect structure can function as increasing the number of active sites for reaction of Li+ ions with electrolytes. The outstanding performance and unique structural characteristics of the ReS2@CB anodes make them promising candidates for the ever-increasing development of advanced LIBs. Full article
(This article belongs to the Section Energy Materials)
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<p>The schematic diagram illustrating each synthesis process for ReS<sub>2</sub>@CB structure.</p> Full article ">Figure 2
<p>SEM images of the (<b>a</b>,<b>b</b>) ReS<sub>2</sub>@CB, (<b>c</b>,<b>d</b>) pure CB and (<b>e</b>,<b>f</b>) ReS<sub>2</sub> powder.</p> Full article ">Figure 3
<p>(<b>a</b>) XRD pattern of the ReS<sub>2</sub>@CB, ReS<sub>2</sub> powder, and CB; (<b>b</b>,<b>c</b>) TEM images of the microstructures of the ReS<sub>2</sub>@CB; (<b>d</b>,<b>e</b>) HR-TEM images of the ReS<sub>2</sub>@CB and pure CB; and (<b>f</b>) TEM image of the ReS<sub>2</sub> powder.</p> Full article ">Figure 4
<p>XPS spectra of the ReS<sub>2</sub>@CB: survey spectra (<b>a</b>), and high-resolution spectra of Re 4f (<b>b</b>) and S 2p (<b>c</b>).</p> Full article ">Figure 5
<p>(<b>a</b>) CV curve of the ReS<sub>2</sub>@CB, (<b>b</b>) galvanostatic charge/discharge (GCD) process of the ReS<sub>2</sub>@CB in the initial four cycles; (<b>c</b>) rate capability of the as-prepared samples at different current densities; and (<b>d</b>) cycling performance of each sample at 1 A/g and the corresponding coulombic efficiency of the ReS<sub>2</sub>@CB.</p> Full article ">Figure 6
<p>(<b>a</b>) EIS data of the ReS<sub>2</sub>@CB and ReS<sub>2</sub> powder samples, (<b>b</b>) CV curves of the ReS<sub>2</sub>@CB electrode at the different scan rates, (<b>c</b>) correlation between logarithmic peak current (cathodic and anodic peaks) versus logarithmic voltage scan rate, and (<b>d</b>) comparison of capacity at the different current densities for the ReS<sub>2</sub>@CB with those of reported ReS<sub>2</sub>-based composite anodes.</p> Full article ">
14 pages, 4171 KiB  
Article
A Study on Tannery Sludge as a Raw Material for Cement Mortar
by Jurgita Malaiškienė, Olga Kizinievič and Viktor Kizinievič
Materials 2019, 12(9), 1562; https://doi.org/10.3390/ma12091562 - 13 May 2019
Cited by 21 | Viewed by 3390
Abstract
The paper analyses the properties (chemical and mineral composition, microstructure, density, etc.) of recycled tannery sludge (TS) and the possibilities for using it in cement mortar mixture. Mortar specimens containing 3–12% of tannery sludge by weight of cement and 3–9% of tannery sludge [...] Read more.
The paper analyses the properties (chemical and mineral composition, microstructure, density, etc.) of recycled tannery sludge (TS) and the possibilities for using it in cement mortar mixture. Mortar specimens containing 3–12% of tannery sludge by weight of cement and 3–9% of tannery sludge by weight of sand were tested. Flowability, density, ultrasonic pulse velocity (UPV), flexural and compressive strength, water absorption and sorptivity of the mortar were analysed. X-ray diffraction (XRD) and scanning electron microscopy (SEM) analysis of tannery sludge and mortar are presented. The tests revealed that replacement of 6% of cement with tannery sludge in the mix increased flexural and compressive strength and UPV values, whereas water absorption decreased. SEM and XRD analysis revealed that specimens with tannery sludge contained lower amounts of ettringite and higher amounts of portlandite; the obtained structure was denser and contained more calcium hydrosilicates (C-S-H). Chromium leaching values in cement mortars were found not to exceed the limit values set forth in Directive 2003/33/EC. Full article
(This article belongs to the Section Construction and Building Materials)
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<p>X-ray diffraction patterns of tannery sludge: C—calcite, Q—quartz.</p> Full article ">Figure 2
<p>Scanning electron microscopy (SEM) image of tannery sludge (TS).</p> Full article ">Figure 3
<p>Relationship between mortar slump and TS content in the mix.</p> Full article ">Figure 4
<p>The impact of TS content in the mix on mortar density.</p> Full article ">Figure 5
<p>The impact of TS content on ultrasound pulse velocity (UPV).</p> Full article ">Figure 6
<p>The effect of TS content in the mix on flexural strength.</p> Full article ">Figure 7
<p>The effect of TS content in the mix on compressive strength.</p> Full article ">Figure 8
<p>Water absorption when a part of cement is replaced with TS.</p> Full article ">Figure 9
<p>Water absorption when a part of sand is replaced with TS.</p> Full article ">Figure 10
<p>The impact of TS content on sorptivity.</p> Full article ">Figure 11
<p>The impact of TS on the sorptivity in mortars used for renovation application.</p> Full article ">Figure 12
<p>Microstructure images of (<b>a</b>) specimen without TS, and (<b>b</b>) specimen with 6% of sand replaced with TS (magnification: ×7000).</p> Full article ">Figure 13
<p>X-ray diffraction (XRD) patterns (E—ettringite, Q—quartz, D—dolomite, C—calcite, P—portlandite, A—alite).</p> Full article ">
8 pages, 3258 KiB  
Article
Revealing the Microstructure Evolution and Carbonation Hardening Mechanism of β-C2S Pastes by Backscattered Electron Images
by Songhui Liu, Xuemao Guan, Haibo Zhang, Yuli Wang and Mifeng Gou
Materials 2019, 12(9), 1561; https://doi.org/10.3390/ma12091561 - 13 May 2019
Cited by 17 | Viewed by 3556
Abstract
β-dicalcium silicate (β-C2S) minerals were prepared. The compositions, microstructures, and distributions of the carbonation products of hardened β-C2S paste were revealed by X-ray diffraction (XRD), Fourier transform-infrared (FT-IR) spectroscopy, and backscattered electron (BSE) image analysis. The results show that [...] Read more.
β-dicalcium silicate (β-C2S) minerals were prepared. The compositions, microstructures, and distributions of the carbonation products of hardened β-C2S paste were revealed by X-ray diffraction (XRD), Fourier transform-infrared (FT-IR) spectroscopy, and backscattered electron (BSE) image analysis. The results show that a dense hardened paste of β-C2S can be obtained after 24 h of carbonation curing. The hardened pastes are composed of pores, silica gel, calcium carbonate, and unreacted dicalcium silicate, with relative volume fractions of 1.3%, 42.1%, 44.9%, and 11.7%, respectively. The unreacted dicalcium silicate is encapsulated with a silica gel rim, and the pores between the original dicalcium silicate particles are filled with calcium carbonate. The sufficient carbonation products that rapidly formed during the carbonation curing process, forming a dense microstructure, are responsible for the carbonation hardening of the β-C2S mineral. Full article
(This article belongs to the Special Issue Microstructures and Durability of Cement-Based Materials)
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<p>X-ray diffraction and Fourier transform-infrared spectra of β-C<sub>2</sub>S before and after carbonation. (<b>a</b>) XRD; (<b>b</b>) FT-IR.</p> Full article ">Figure 2
<p>Backscattered electron (BSE) and energy-dispersive spectroscopy (EDS) images of β-C<sub>2</sub>S after carbonation. (<b>a</b>) BSE image; (<b>b</b>) elemental maps for composite element; (<b>c</b>–<b>f</b>) elemental maps for individual C, O, Si, and Ca, respectively; (<b>g</b>–<b>i</b>) EDS analysis of points A, B, and C.</p> Full article ">Figure 3
<p>BSE images and phase distribution maps of β-C<sub>2</sub>S after carbonation. (<b>a</b>) BSE image; (<b>b</b>) images of the composite phases; (<b>c–f</b>) images of the individual phases after the gray level separation.</p> Full article ">Figure 4
<p>The gray level frequency and the cumulative distribution curves for different phases.</p> Full article ">Figure 5
<p>Schematic of carbonation hardening for β-C<sub>2</sub>S.</p> Full article ">
11 pages, 2073 KiB  
Article
How to Boost the Activity of the Monolayer Pt Supported on TiC Catalysts for Oxygen Reduction Reaction: A Density Functional Theory Study
by Hui Zhu, Houyi Liu, Lei Yang and Beibei Xiao
Materials 2019, 12(9), 1560; https://doi.org/10.3390/ma12091560 - 13 May 2019
Cited by 4 | Viewed by 3103
Abstract
Developing the optimized electrocatalysts with high Pt utilization as well as the outstanding performance for the oxygen reduction reaction (ORR) has raised great attention. Herein, the effects of the interlayer ZrC, HfC, or TiN and the multilayer Pt shell on the adsorption ability [...] Read more.
Developing the optimized electrocatalysts with high Pt utilization as well as the outstanding performance for the oxygen reduction reaction (ORR) has raised great attention. Herein, the effects of the interlayer ZrC, HfC, or TiN and the multilayer Pt shell on the adsorption ability and the catalytic activity of the TiC@Pt core-shell structures are systemically investigated by density functional theory (DFT) calculations. For the sandwich structures, the presence of TiN significantly enhances the adsorption ability of the Pt shell, leading to the deterioration of the activity whilst the negligible influence of the ZrC and HfC insertion results the comparable performance with respect to TiC@Pt1ML. In addition, increasing the thickness of the Pt shell reduces the oxyphilic capacity and then mitigates the OH poisoning. From the free energy plots, the superior activity of TiC@Pt2ML is identified in comparison with 1ML and 3ML Pt shell. Herein, the improved activity with its high Pt atomic utilization makes the potential TiC@Pt2ML electrocatalyst for the future fuel cells. Full article
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<p>The catalyst structures and the stable adsorption configurations.</p> Full article ">Figure 2
<p>(<b>a</b>) The adsorption energy <span class="html-italic">E</span><sub>ads</sub> of the ORR intermediates as a function of <span class="html-italic">E</span><sub>ads</sub> (OH); and (<b>b</b>) the partial density of states (PDOS) for the Pt surface atoms.</p> Full article ">Figure 3
<p>The free energies at the potential of 0 V (<b>a</b>) and 1.23 V (<b>b</b>). The RDS Δ<span class="html-italic">G</span> are shown in the insets.</p> Full article ">Figure 4
<p>The reaction pathway of the O<sub>2</sub> dissociation mechanism on TiC@Pt<sub>2ML</sub>.</p> Full article ">
14 pages, 2924 KiB  
Article
Structure Inheritance in Nanoparticle Ink Direct-Writing Processes and Crack-Free Nano-Copper Interconnects Printed by a Single-Run Approach
by Shujie Liu, Yujie Li, Songling Xing, Lei Liu, Guisheng Zou and Peng Zhang
Materials 2019, 12(9), 1559; https://doi.org/10.3390/ma12091559 - 13 May 2019
Cited by 13 | Viewed by 3533
Abstract
When nanoparticle conductive ink is used for printing interconnects, cracks and pores are common defects that deteriorate the electrical conductivity of the printed circuits. Influences of the ink solvent, the solid fraction of the ink, the pre-printing treatment and the sintering parameters on [...] Read more.
When nanoparticle conductive ink is used for printing interconnects, cracks and pores are common defects that deteriorate the electrical conductivity of the printed circuits. Influences of the ink solvent, the solid fraction of the ink, the pre-printing treatment and the sintering parameters on the interconnect morphology and conductivity were investigated. It was found that the impacts of all these factors coupled with each other throughout the whole procedure, from the pre-printing to the post-printing processes, and led to a structure inheritance effect. An optimum process route was developed for producing crack-free interconnects by a single-run direct-writing approach using home-made nano-copper ink. A weak gel was promoted in the ink before printing in the presence of long-chain polymers and bridging molecules by mechanical agitation. The fully developed gel network prevented the phase separation during ink extrusion and crack formations during drying. With the reducing agents in the ink and slow evaporation of the ink solvent, compact packing and neck joining of copper nanoparticles were obtained after a two-step sintering process. The crack-free interconnects successfully produced have a surface roughness smaller than 1.5 μm and the square resistances as low as 0.01 Ω/□. Full article
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Graphical abstract

Graphical abstract
Full article ">Figure 1
<p>(<b>a</b>) A schematic picture of the home-made direct-writing installation. (<b>b</b>) The temperature profiles set and measured for both the one-step and two-step sintering strategies. (<b>c</b>) A typical TEM image of the nano-copper particles. The inset in (<b>c</b>) is a high resolution TEM image of a particle. The organic layer capped around the particle is pointed out by a white arrow. The scale bar in the inset stands for 5 nm. (<b>d</b>) Particles dispersed in the ink solvent by the steric hindrance effect as the organic chains extended fully and (<b>e</b>) particles aggregated when the organic chains curled up.</p> Full article ">Figure 2
<p>Interconnects prepared by using nano-copper inks with solid fractions of (<b>a</b>) 20%, (<b>b</b>) 30%, (<b>c</b>) 40% and (<b>d</b>) 50%, respectively. The insets show microstructures at large magnifications. The scale bars in the insets stand for 500 nm. (<b>e</b>) The length and width of cracks in the interconnects varying with the solid fractions of the inks. Water was used as the ink solvent.</p> Full article ">Figure 3
<p>Interconnects prepared by using nano-copper inks with solvents of (<b>a</b>) water, (<b>b</b>) ethylene glycol, (<b>c</b>) ethanol, (<b>d</b>) the hydrazine hydrate solution, (<b>e</b>) the hydrazine hydrate solution mixed with ethylene glycol, (<b>f</b>) the hydrazine hydrate solution mixed with ethanol, (<b>g</b>) ethylene glycol mixed with ethanol and (<b>h</b>) a mixed solvent composed of the hydrazine hydrate solution, ethylene glycol and ethanol, respectively. The insets show microstructures at small magnifications. The scale bars in the insets stand for 40 μm. The white arrow in the inset of (<b>g</b>) marks out a block of organic material. (<b>i</b>) Typical XRD patterns measured for interconnects printed with the water- and ethanol-based inks. Quite a lot Cu<sub>2</sub>O was detected in the interconnect printed with the water-based ink.</p> Full article ">Figure 4
<p>Microstructures of the interconnects sintered with (<b>a</b>) the one-step and (<b>b</b>) the two-step processes, respectively.</p> Full article ">Figure 5
<p>Microstructures of the interconnects printed using inks pretreated by (<b>a</b>) ultrasound and (<b>b</b>) the mechanical-ultrasonic combined method, respectively. The insets show the corresponding printing processes. The scale bars in the insets stand for 20 mm.</p> Full article ">Figure 6
<p>(Color online only) Schematic pictures of the printing procedures influenced by various key factors and corresponding microstructures obtained. (<b>a1</b>,<b>a2</b>) Particle configurations in the ink pretreated with and without the mechanical agitation, respectively. (<b>a3</b>) The printing procedure from extrusion to sintering. (<b>a4</b>,<b>a5</b>) Optical microscope images of the interconnect structures printed on glass substrates and dried in air for 5 min with and without the mechanical-ultrasonic combined pretreatment, respectively. (<b>b1</b>–<b>b8</b>,<b>c1</b>–<b>c8</b>,<b>d1</b>–<b>d8</b>,<b>e1</b>–<b>e8</b>) Particle configurations developed in each stage of the printing procedure using inks with the solid fractions of 20%, 30%, 40% and 50%, respectively. (<b>b6</b>–<b>e6</b>,<b>b8</b>–<b>e8</b>) Typical SEM microstructural images of the printed interconnect structures. Among them, (<b>d6-2</b>–<b>d6-4</b>,<b>d8-2</b>–<b>d8-4</b>) were obtained from the cross sections of the interconnects. The others were top views of the interconnects. (<b>d2-1</b>–<b>d2-3</b>) Schematic pictures to show influences of the printing parameters d (the distance between the nozzle and the substrate surface) and v (the moving speed of the sample platform) on the morphologies of the printed imprints when a ink with a solid fraction of 40% is applied. (<b>e2-1</b>) A macroscopic image of the printing process using a nano-copper ink with a solid fraction of 50%. Particle clusters blocked the nozzle and a discontinuous imprint was left on the substrate.</p> Full article ">Figure 7
<p>(<b>a</b>) A copper film and (<b>b</b>) an interconnect wire printed by the optimized single-run direct-writing procedure. Metallic luster of the interconnect wire could be clearly seen in (<b>b</b>) from the corresponding view angle. (<b>c</b>) A typical SEM image and (<b>d</b>) a 3D optical image of the top surface layer of the interconnect wire shown in (<b>b</b>).</p> Full article ">
11 pages, 3291 KiB  
Article
Mutual Inductance and Coupling Effects in Acoustic Resonant Unit Cells
by Changlin Ding, Yibao Dong, Kun Song, Shilong Zhai, Yuanbo Wang and Xiaopeng Zhao
Materials 2019, 12(9), 1558; https://doi.org/10.3390/ma12091558 - 13 May 2019
Cited by 10 | Viewed by 3236
Abstract
We present an acoustic metamaterial (AMM) consisting of a dumbbell-shaped split hollow sphere (DSSHS). Transmission results of experiments and simulations both presented a transmitted dip at the resonant frequency of AMM, which demonstrated its negative modulus property. As the two split holes in [...] Read more.
We present an acoustic metamaterial (AMM) consisting of a dumbbell-shaped split hollow sphere (DSSHS). Transmission results of experiments and simulations both presented a transmitted dip at the resonant frequency of AMM, which demonstrated its negative modulus property. As the two split holes in the DSSHS had strong coupling effects for the acoustic medium in the local region, the dip could be simply manipulated by tuning the distance between the split holes. When the distance was large enough, the mutual inductance tended to disappear, and a weak interaction existed in the structure. According to the property of weak interaction, a multiband AMM and a broadband AMM with a negative modulus could be achieved by arraying DSSHS clusters with different distances. Furthermore, mutual inductance and coupling in DSSHS reinforced the local resonance, and this kind of cell could be used to design the acoustic metasurface to abnormally control the refractive waves. Full article
(This article belongs to the Special Issue Advances in Acoustic Metamaterials)
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<p>(<b>a</b>) The 3D schematic diagraph of DSSHS in acoustic waveguide; (<b>b</b>) the cross-sectional diagram of DSSHS and the acoustic effective L-C circuit.</p> Full article ">Figure 2
<p>(<b>a</b>) The 3D printed DSSHS structure; (<b>b</b>) the fabricated specimen of DSSHS AMM.</p> Full article ">Figure 3
<p>Physical diagram of the impendence tube testing equipment.</p> Full article ">Figure 4
<p>(<b>a</b>) The simulated and (<b>b</b>) experimental transmissions of the DSSHS AMMs with tuned distances, <span class="html-italic">d</span><sub>0</sub>, from 0.5 to 4 mm.</p> Full article ">Figure 5
<p>The relationship between resonant frequency and distance, <span class="html-italic">d</span><sub>0</sub>, of two spit holes in DSSHS.</p> Full article ">Figure 6
<p>The acoustic field distribution at 1150 Hz of (<b>a</b>) DSSHS and (<b>b</b>) SHS. The transmitted acoustic field of DSSHS with different hole distances at resonant frequency, (<b>c</b>) 1, (<b>d</b>) 2, (<b>e</b>) 4, and (<b>f</b>) 19 mm.</p> Full article ">Figure 7
<p>The transmission of broadband AMM.</p> Full article ">Figure 8
<p>The effective parameters of broadband AMM: (<b>a</b>) effective mass density and (<b>b</b>) effective modulus.</p> Full article ">Figure 9
<p>The transmitted acoustic field of the DSSHS metasurface. The white arrows indicate the direction of energy of acoustic waves.</p> Full article ">
12 pages, 2646 KiB  
Article
Biomechanical Loading Comparison between Titanium and Unsintered Hydroxyapatite/Poly-L-Lactide Plate System for Fixation of Mandibular Subcondylar Fractures
by Shintaro Sukegawa, Takahiro Kanno, Norio Yamamoto, Keisuke Nakano, Kiyofumi Takabatake, Hotaka Kawai, Hitoshi Nagatsuka and Yoshihiko Furuki
Materials 2019, 12(9), 1557; https://doi.org/10.3390/ma12091557 - 13 May 2019
Cited by 12 | Viewed by 4485
Abstract
Osteosynthesis absorbable materials made of uncalcined and unsintered hydroxyapatite (u-HA) particles, poly-l-lactide (PLLA), and u-HA/PLLA are bioresorbable, and these plate systems have feasible bioactive osteoconductive capacities. However, their strength and stability for fixation in mandibular subcondylar fractures remain unclear. This in [...] Read more.
Osteosynthesis absorbable materials made of uncalcined and unsintered hydroxyapatite (u-HA) particles, poly-l-lactide (PLLA), and u-HA/PLLA are bioresorbable, and these plate systems have feasible bioactive osteoconductive capacities. However, their strength and stability for fixation in mandibular subcondylar fractures remain unclear. This in vitro study aimed to assess the biomechanical strength of u-HA/PLLA bioresorbable plate systems after internal fixation of mandibular subcondylar fractures. Tensile and shear strength were measured for each u-HA/PLLA and titanium plate system. To evaluate biomechanical behavior, 20 hemimandible replicas were divided into 10 groups, each comprising a titanium plate and a bioresorbable plate. A linear load was applied anteroposteriorly and lateromedially to each group to simulate the muscular forces in mandibular condylar fractures. All samples were analyzed for each displacement load and the displacement obtained by the maximum load. Tensile and shear strength of the u-HA/PLLA plate were each approximately 45% of those of the titanium plates. Mechanical resistance was worst in the u-HA/PLLA plate initially loaded anteroposteriorly. Titanium plates showed the best mechanical resistance during lateromedial loading. Notably, both plates showed similar resistance when a lateromedially load was applied. In the biomechanical evaluation of mandibular condylar fracture treatment, the u-HA/PLLA plates had sufficiently high resistance in the two-plate fixation method. Full article
(This article belongs to the Special Issue Absorbable Metals for Biomedical Applications)
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<p>Mechanical strength models were prepared by fixing the plate with screws to the polyetherketoneketone plate. (<b>A</b>) Tensile strength; (<b>B</b>) shear strength.</p> Full article ">Figure 2
<p>(<b>A</b>) The mandibular subcondylar fracture replicas were held in place by double titanium (Ti) straight plates (thickness: 1.0 mm) with four monocortical screws (2.0 mm in diameter and 6 mm long screws; group A) or by double unsintered hydroxyapatite (u-HA)/ poly-<span class="html-small-caps">l</span>-lactide (PLLA) straight plates (thickness: 1.4 mm), each with four monocortical screws (2.0 mm in diameter and 6 mm long; group B). A linear load was applied at a displacement speed of 1 mm/min. (<b>B</b>) Anteroposterior (vertical) linear loading. (<b>C</b>) Lateromedial (lateral) linear loading.</p> Full article ">Figure 3
<p>(<b>A</b>) Comparison of titanium plates and unsintered hydroxyapatite (u-HA)/poly-<span class="html-small-caps">l</span>-lactide (PLLA) bioresorbable plates with regard to maximum tensile test force and test force at 1 mm displacement in the tensile test. (<b>B</b>) Comparison of titanium plates and u-HA/PLLA bioresorbable plates with regard to maximum tensile test force and test force at 1 mm displacement in the shear test.</p> Full article ">Figure 4
<p>Load values of the titanium plates and unsintered hydroxyapatite (u-HA)/poly-<span class="html-small-caps">l</span>-lactide (PLLA) bioresorbable plates according to the amount of displacement in the anteroposterior loading test.</p> Full article ">Figure 5
<p>Change in subcondylar fracture segments under anteroposterior loading. Ti, titanium (plates); u-HA/PLLA, unsintered hydroxyapatite/poly-<span class="html-small-caps">l</span>-lactide (bioresorbable plates).</p> Full article ">Figure 6
<p>Load values of the titanium and unsintered hydroxyapatite (u-HA)/poly-<span class="html-small-caps">l</span>-lactide (PLLA) bioresorbable plates according to the amount of displacement in the lateromedial loading test.</p> Full article ">Figure 7
<p>Change in subcondylar fracture segment under lateromedial loading. Ti, titanium (plates); u-HA/PLLA, unsintered hydroxyapatite/poly-<span class="html-small-caps">l</span>-lactide (bioresorbable plates).</p> Full article ">
9 pages, 3904 KiB  
Article
Effect of Heat Treatment on Microstructure and Properties of Clad Plates 316L/Q370qE
by Zimeng Wang, Shumei Kang, Meiling Xu, Yanqiang Cheng and Ming Dong
Materials 2019, 12(9), 1556; https://doi.org/10.3390/ma12091556 - 12 May 2019
Cited by 6 | Viewed by 2752
Abstract
Mechanical properties of Q370qE carbon steel can be improved by cladding it with 316L stainless steel. After rolling these materials together, microstructure, hardness, shear strength, and corrosion properties of the cladded metals were evaluated. Hardness and shear tests were performed according to appropriate [...] Read more.
Mechanical properties of Q370qE carbon steel can be improved by cladding it with 316L stainless steel. After rolling these materials together, microstructure, hardness, shear strength, and corrosion properties of the cladded metals were evaluated. Hardness and shear tests were performed according to appropriate standards to evaluate the bonds. The results show that the remarkable diffusion of Ni and Cr formed a hard transition zone. The width of this diffusion zone increases with increasing temperature. The shear strength of the clad interface reached a minimum of 385 MPa. In addition, the surfaces of samples were examined by neutral salt spray (NSS) tests and potentiodynamic polarization tests to examine corrosion behavior. The 316L side primarily exhibited pitting corrosion, while the Q370qE side was dominated by uniform corrosion. Full article
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<p>Schematic representation of the process for 316L/Q370qE clad plate (<b>a</b>) surface treatment and stacking; (<b>b</b>) hot rolling; (<b>c</b>) sampling schematic.</p> Full article ">Figure 2
<p>Microstructures of the Q370qE side (<b>a</b>) 500 °C; (<b>b</b>) 600 °C; (<b>c</b>) 800 °C; (<b>d</b>) 1000 °C.</p> Full article ">Figure 3
<p>Microstructures of the 316L side and SEM results: (<b>a</b>) 500 °C; (<b>b</b>) 600 °C; (<b>c</b>) 800 °C; (<b>d</b>) 1000 °C.</p> Full article ">Figure 4
<p>Line analyses of transition zone: (<b>a</b>,<b>b</b>) 500 °C; (<b>c</b>,<b>d</b>) 600 °C; (<b>e</b>,<b>f</b>) 800 °C; (<b>g</b>,<b>h</b>) 1000 °C.</p> Full article ">Figure 5
<p>Hardness distribution near phase interface.</p> Full article ">Figure 6
<p>Shear strength of the interface.</p> Full article ">Figure 7
<p>Microstructures of the interface: (<b>a</b>) 500 °C; (<b>b</b>) 600 °C; (<b>c</b>) 800 °C; (<b>d</b>) 1000 °C.</p> Full article ">Figure 8
<p>Polarization curve at the interface.</p> Full article ">
12 pages, 25446 KiB  
Article
Design of a 2 × 4 Hybrid MMI-MZI Configuration with MMI Phase-Shifters
by Boris B. Niraula and Conrad Rizal
Materials 2019, 12(9), 1555; https://doi.org/10.3390/ma12091555 - 12 May 2019
Cited by 3 | Viewed by 4205
Abstract
This paper reports design of a 2 × 4 hybrid multimode interferometer-Mach-zehnder interferometer (MMI-MZI) configuration consiting of compact thermo-optical switches on the silicon-on-insulator (SOI) platform. The device consists of two identical MMI slab waveguides as power splitters and couplers that are connected with [...] Read more.
This paper reports design of a 2 × 4 hybrid multimode interferometer-Mach-zehnder interferometer (MMI-MZI) configuration consiting of compact thermo-optical switches on the silicon-on-insulator (SOI) platform. The device consists of two identical MMI slab waveguides as power splitters and couplers that are connected with two identical MMI-based phase shifters, and linear tapers at both ends of the MMIs to minimize the power coupling loss. A thin Al pad is used as a heating element and a trench is created around this pad to prevent heat from spreading, and to minimize loss. The calculated average thermo-optical switching power consumption, excess loss, and power imbalance are 1.4 mW, 0.9 dB, and 0.1 dB, respectively. The overall footprint of the device is 6 × 304 μ m 2 . The new heating method has advantages of compact size, ease of fabrication on SOI platform with the current CMOS technology, and offers low excess loss and power consumption as demanded by devices based on SOI technology. The device can act as two independent optical switches in one device. Full article
(This article belongs to the Special Issue Photonic Materials and Devices)
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<p>Schematics of the MMI device: Decoupler (MMI<math display="inline"><semantics> <msub> <mrow/> <mn>1</mn> </msub> </semantics></math>) and Coupler (MMI<math display="inline"><semantics> <msub> <mrow/> <mn>2</mn> </msub> </semantics></math>). The inset in the top middle shows a tapered access waveguide and in the top right the cross-sectional view of the MMIs. Input ports: a<math display="inline"><semantics> <msub> <mrow/> <mrow> <mi>i</mi> <mn>1</mn> </mrow> </msub> </semantics></math> and a<math display="inline"><semantics> <msub> <mrow/> <mrow> <mi>i</mi> <mn>2</mn> </mrow> </msub> </semantics></math> of MMI<math display="inline"><semantics> <msub> <mrow/> <mn>1</mn> </msub> </semantics></math> and output ports: a<math display="inline"><semantics> <msub> <mrow/> <mrow> <mi>o</mi> <mn>11</mn> </mrow> </msub> </semantics></math>, a<math display="inline"><semantics> <msub> <mrow/> <mrow> <mi>o</mi> <mn>22</mn> </mrow> </msub> </semantics></math>, a<math display="inline"><semantics> <msub> <mrow/> <mrow> <mi>o</mi> <mn>33</mn> </mrow> </msub> </semantics></math>, and a<math display="inline"><semantics> <msub> <mrow/> <mrow> <mi>o</mi> <mn>44</mn> </mrow> </msub> </semantics></math> of MMI<math display="inline"><semantics> <msub> <mrow/> <mn>2</mn> </msub> </semantics></math>.</p> Full article ">Figure 2
<p>The schematics showing the principle of operation of optical switches. It shows the top view of the MMI<math display="inline"><semantics> <msub> <mrow/> <mn>1</mn> </msub> </semantics></math>/MMI<math display="inline"><semantics> <msub> <mrow/> <mn>2</mn> </msub> </semantics></math>, and phase shifters MMI<math display="inline"><semantics> <msub> <mrow/> <mn>3</mn> </msub> </semantics></math>/MMI<math display="inline"><semantics> <msub> <mrow/> <mn>4</mn> </msub> </semantics></math>, and corresponding waveguide width, length, and positions of access waveguides. The device parameters were calculated using MATLAB Mode Solver [<a href="#B18-materials-12-01555" class="html-bibr">18</a>] as well as FDTD simulation [<a href="#B19-materials-12-01555" class="html-bibr">19</a>]. The device acts as two independent optical switches depending on whether the input is fed through a<math display="inline"><semantics> <msub> <mrow/> <mrow> <mi>i</mi> <mn>1</mn> </mrow> </msub> </semantics></math> (<b>A</b>) or a<math display="inline"><semantics> <msub> <mrow/> <mrow> <mi>i</mi> <mn>2</mn> </mrow> </msub> </semantics></math> (<b>B</b>).</p> Full article ">Figure 3
<p>Electric field inside the the access waveguides and MMI<math display="inline"><semantics> <msub> <mrow/> <mn>1</mn> </msub> </semantics></math> where the input is fed through (<b>a</b>) port a<math display="inline"><semantics> <msub> <mrow/> <mrow> <mi>i</mi> <mn>1</mn> </mrow> </msub> </semantics></math> and (<b>b</b>) port a<math display="inline"><semantics> <msub> <mrow/> <mrow> <mi>i</mi> <mn>2</mn> </mrow> </msub> </semantics></math>. Two-dimensional FDTD numerical method was used to optimize and verify the design [<a href="#B19-materials-12-01555" class="html-bibr">19</a>], as it was shown to produce sufficiently accurate results in simulating devices based on SOI channel waveguides.</p> Full article ">Figure 4
<p>(<b>a</b>) Field profile of a MMI<math display="inline"><semantics> <msub> <mrow/> <mn>3</mn> </msub> </semantics></math> phase shifter without a heater. The 4 <math display="inline"><semantics> <mi mathvariant="sans-serif">μ</mi> </semantics></math>m long tapered access waveguides are connected at both ends of the MMIs to reduce power losses (<b>b</b>) Intensity profile of the 1 × 1 MMI<math display="inline"><semantics> <msub> <mrow/> <mn>3</mn> </msub> </semantics></math> phase shifter as a function of L<math display="inline"><semantics> <msub> <mrow/> <mrow> <mi>M</mi> <mi>M</mi> <msub> <mi>I</mi> <mn>3</mn> </msub> </mrow> </msub> </semantics></math>.</p> Full article ">Figure 5
<p>Cascaded MMI devices as tunable optical switches. Case I: The input is fed through a<math display="inline"><semantics> <msub> <mrow/> <mrow> <mi>i</mi> <mn>1</mn> </mrow> </msub> </semantics></math> <math display="inline"><semantics> <mrow> <mo>Δ</mo> <msub> <mi>ϕ</mi> <mrow> <mi>M</mi> <mi>M</mi> <mi>I</mi> <mn>3</mn> </mrow> </msub> </mrow> </semantics></math> = <math display="inline"><semantics> <mrow> <mo>Δ</mo> <msub> <mi>ϕ</mi> <mrow> <mi>M</mi> <mi>M</mi> <mi>I</mi> <mn>4</mn> </mrow> </msub> </mrow> </semantics></math> = 0, Case II: <math display="inline"><semantics> <mrow> <mo>Δ</mo> <msub> <mi>ϕ</mi> <mrow> <mi>M</mi> <mi>M</mi> <mi>I</mi> <mn>3</mn> </mrow> </msub> </mrow> </semantics></math> = <math display="inline"><semantics> <mi>π</mi> </semantics></math>/2 and <math display="inline"><semantics> <mrow> <mo>Δ</mo> <msub> <mi>ϕ</mi> <mrow> <mi>M</mi> <mi>M</mi> <mi>I</mi> <mn>4</mn> </mrow> </msub> </mrow> </semantics></math> = 0, and Case III): <math display="inline"><semantics> <mrow> <mo>Δ</mo> <msub> <mi>ϕ</mi> <mrow> <mi>M</mi> <mi>M</mi> <mi>I</mi> <mn>3</mn> </mrow> </msub> </mrow> </semantics></math> = 0.85 <math display="inline"><semantics> <mi>π</mi> </semantics></math> and <math display="inline"><semantics> <mrow> <mo>Δ</mo> <msub> <mi>ϕ</mi> <mrow> <mi>M</mi> <mi>M</mi> <mi>I</mi> <mn>4</mn> </mrow> </msub> </mrow> </semantics></math> = 0.4 <math display="inline"><semantics> <mi>π</mi> </semantics></math>. The dark bold arrows indicate the light input and output positions and the numbers are the normalized optical powers.</p> Full article ">Figure 6
<p>Calculated powers from the output ports of the MMI<math display="inline"><semantics> <msub> <mrow/> <mn>2</mn> </msub> </semantics></math>: bar (a<math display="inline"><semantics> <msub> <mrow/> <mrow> <mi>o</mi> <mn>11</mn> </mrow> </msub> </semantics></math>) and cross (a<math display="inline"><semantics> <msub> <mrow/> <mrow> <mi>o</mi> <mn>44</mn> </mrow> </msub> </semantics></math>) as a function of the heating power in MMI<math display="inline"><semantics> <msub> <mrow/> <mn>3</mn> </msub> </semantics></math>, and input is fed at a<math display="inline"><semantics> <msub> <mrow/> <mrow> <mi>i</mi> <mn>1</mn> </mrow> </msub> </semantics></math>. The solid lines are fitted curve using KyPlot [<a href="#B25-materials-12-01555" class="html-bibr">25</a>].</p> Full article ">
11 pages, 6048 KiB  
Article
The Effect of ECAP Temperature on the Microstructure and Properties of a Rolled Rare Earth Magnesium Alloy
by Yun Tan, Wei Li, Weiwei Hu, Xiaofang Shi and Liang Tian
Materials 2019, 12(9), 1554; https://doi.org/10.3390/ma12091554 - 12 May 2019
Cited by 15 | Viewed by 2992
Abstract
Deformation of an as-rolled rare earth Mg-2Y-0.6Nd-0.6Zr alloy, at different temperatures, was carried out along the BC (90° anticlockwise rotation of the samples after each ECAP pass) route by equal channel angular pressing (ECAP). The effects of the deformation temperature and the predeformation [...] Read more.
Deformation of an as-rolled rare earth Mg-2Y-0.6Nd-0.6Zr alloy, at different temperatures, was carried out along the BC (90° anticlockwise rotation of the samples after each ECAP pass) route by equal channel angular pressing (ECAP). The effects of the deformation temperature and the predeformation on the microstructure of the magnesium alloy were determined by the microstructure examination. The slip systems and texture change of the Mg-2Y-0.6Nd-0.6Zr alloy were investigated by X-ray diffraction (XRD) and electron backscattered diffraction (EBSD), after equal channel angular deformation. The results showed that after seven passes of rolling, the grain size in the Mg-2Y-0.6Nd-0.6Zr alloy was refined to approximately 22 µm and the slip occurred mainly by a cylindrical slip and a pyramidal slip. After one pass of ECAP at 340 °C, the internal average grain size was significantly reduced to 11 µm, the cylindrical diffraction intensity clearly weakened, and the pyramidal diffraction intensity increased. EBSD pole figure analysis revealed that the base texture of the rolled Mg-2Y-0.6Nd-0.6Zr alloy weakened from 24.31 to 11.34 after ECAP. The mechanical properties indicated that the tensile strength and elongation of the rolled Mg-2Y-0.6Nd-0.6Zr alloy reached maximum values, when the deformation temperature was 340 °C. Full article
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<p>Equal channel angular pressing (ECAP) mold diagram.</p> Full article ">Figure 2
<p>The dimension of the uniaxial tensile specimen (Unit: mm).</p> Full article ">Figure 3
<p>Photograph of rolled samples.</p> Full article ">Figure 4
<p>Optical microstructures of the Mg-2Y-0.6Nd-0.6Zr magnesium alloy: (<b>a</b>) As-cast state, and (<b>b</b>) as-rolled state.</p> Full article ">Figure 5
<p>Mg-2Y-0.6Nd-0.6Zr alloy stress and strain curves of the as-cast and as-rolled states.</p> Full article ">Figure 6
<p>Optical microstructures of the deformed Mg-2Y-0.6Nd-0.6Zr alloy after ECAP at different temperatures: (<b>a</b>) 300 °C, (<b>b</b>) 320 °C, (<b>c</b>) 340 °C, and (<b>d</b>) 360 °C.</p> Full article ">Figure 7
<p>XRD spectra of Mg-2Y-0.6Nd-0.6Zr alloy during ECAP deformation at different temperatures.</p> Full article ">Figure 8
<p>Electron backscattered diffraction (EBSD) analysis results: pole figures of the as-rolled state (<b>a</b>) and extruded state (<b>b</b>).</p> Full article ">Figure 9
<p>Schmid factor maps of the Mg-2Y-0.6Nd-0.6Zr alloy samples. (<b>a</b>) As rolled and (<b>b</b>) at 340 °C.</p> Full article ">Figure 10
<p>Tensile strength and elongation of the Mg-2Y-0.6Nd-0.6Zr alloy extruded by the ECAP, in a uniform state, at different temperatures: (<b>a</b>) Ultimate tensile strength, and (<b>b</b>) elongation.</p> Full article ">Figure 11
<p>Tensile fracture SEM morphology of the ECAP extruded-rolled Mg-2Y-0.6Nd-0.6Zr alloy: (<b>a</b>) As cast, (<b>b</b>) as rolled, (<b>c</b>) 300 °C, (<b>d</b>) 320 °C, (<b>e</b>) 340 °C, and (<b>f</b>) 360 °C.</p> Full article ">
12 pages, 4670 KiB  
Article
The Correlation of Microstructure and Mechanical Properties of In-Situ Al-Mg2Si Cast Composite Processed by Equal Channel Angular Pressing
by Mahdi Chegini, Mohammad Hossein Shaeri, Reza Taghiabadi, Sajjad Chegini and Faramarz Djavanroodi
Materials 2019, 12(9), 1553; https://doi.org/10.3390/ma12091553 - 12 May 2019
Cited by 10 | Viewed by 3301
Abstract
In this paper, the effect of equal channel angular pressing (ECAP) on microstructure and mechanical properties of hypereutectic Al-20%Mg2Si and Al-15%Mg2Si, as well as hypoeutectic Al-10%Mg2Si composites has been investigated. After fabricating the composites by in-situ casting, [...] Read more.
In this paper, the effect of equal channel angular pressing (ECAP) on microstructure and mechanical properties of hypereutectic Al-20%Mg2Si and Al-15%Mg2Si, as well as hypoeutectic Al-10%Mg2Si composites has been investigated. After fabricating the composites by in-situ casting, the composites were processed using the ECAP process up to two passes at room temperature. Microstructural studies have been carried out using a field emission scanning electron microscopy equipped with an energy dispersive X-ray spectrometer. Mechanical properties were also documented using Vickers microhardness and shear punch tests. In the hypereutectic composites, a decrease in the average size of pro-eutectic Mg2Si (Mg2Sip) particles, breakages in eutectic networks, and lengthening of the Al (α) phase in direction of shear bands were observed after the ECAP process. For instance, the average size of Mg2Sip Particles in Al-20%Mg2Si composite reduced from 40 to 17 μm after 2 passes of ECAP. Furthermore, a uniform distribution of Mg2Sip particles was developed in the matrix. In hypoeutectic composite, the ECAP process caused a uniform distribution of eutectic Mg2Si (Mg2SiE) in the matrix that considered a favorable microstructure. Microhardness measurements and shear punch results showed an ascending trend after each pass of ECAP for all specimens. For example, microhardness and shear strength of Al-20%Mg2Si increased from 88 HV and 109 MPa to 119 HV and 249 MPa after two passes indicating 35% and 34% increments, respectively. Density and porosity calculations by Archimedes principle revealed that the density of the composites increased after two passes of ECAP due to the reduction of porosity. Full article
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<p>FESEM images of Al-20%Mg<sub>2</sub>Si composite; (<b>a</b>,<b>d</b>) before the equal channel angular pressing (ECAP) process, (<b>b</b>,<b>e</b>) after the first pass, and (<b>c</b>,<b>f</b>) after the second pass of ECAP.</p> Full article ">Figure 2
<p>Three-dimensional FESEM image and EDS analysis of Mg<sub>2</sub>Si<sub>P</sub> phases in Al-20%Mg<sub>2</sub>Si composite.</p> Full article ">Figure 3
<p>FESEM images of Al-15%Mg<sub>2</sub>Si composites; (<b>a</b>) before the ECAP, (<b>b</b>) after the first pass, and (<b>c</b>) after the second pass of ECAP.</p> Full article ">Figure 4
<p>Variations of the Mg<sub>2</sub>Si<sub>P</sub> particles’ average size in Al-20%Mg<sub>2</sub>Si and Al-15%Mg<sub>2</sub>Si composites as a function of ECAP pass number.</p> Full article ">Figure 5
<p>FESEM images of Al-10%Mg<sub>2</sub>Si composite; (<b>a</b>) before the ECAP process, (<b>b</b>) after the first pass and (<b>c</b>) after the second pass of the ECAP process.</p> Full article ">Figure 6
<p>The variation of density and porosity percentage of Al-Mg<sub>2</sub>Si containing 10, 15 and 20% Mg<sub>2</sub>Si as a function of ECAP pass number; (<b>a</b>) density and (<b>b</b>) porosity percentage.</p> Full article ">Figure 7
<p>The Vickers’ microhardness (HV) of the Al-Mg<sub>2</sub>Si composites with different amount of Mg<sub>2</sub>Si, as a function of the number of ECAP passes.</p> Full article ">Figure 8
<p>(<b>a</b>) The shear stress-normalized displacement curve of Al-20%Mg<sub>2</sub>Si composite before and after the ECAP process. (<b>b</b>) Ultimate shear strength and shear yield strength diagrams of Al-20%Mg<sub>2</sub>Si composite as a function of the number of ECAP passes.</p> Full article ">Figure 9
<p>(<b>a</b>) The shear stress-normalized displacement curve of Al-15%Mg<sub>2</sub>Si composite before and after the ECAP process. (<b>b</b>) Ultimate shear strength and shear yield strength diagrams of Al-15%Mg<sub>2</sub>Si composite as a function of the number of ECAP passes.</p> Full article ">Figure 10
<p>(<b>a</b>) The shear stress-normalized displacement curve of Al-10%Mg<sub>2</sub>Si composite before and after the ECAP process. (<b>b</b>) Ultimate shear strength and shear yield strength diagrams of Al-10%Mg<sub>2</sub>Si composite as a function of the number of ECAP passes.</p> Full article ">
11 pages, 11213 KiB  
Article
Cavitation Wear of Basalt-Based Glass Ceramic
by Marko Pavlovic, Marina Dojcinovic, Radica Prokic-Cvetkovic, Ljubisa Andric, Zoran Ceganjac and Ljiljana Trumbulovic
Materials 2019, 12(9), 1552; https://doi.org/10.3390/ma12091552 - 12 May 2019
Cited by 12 | Viewed by 3481
Abstract
This paper examines the possibility of using basalt-based glass ceramics for construction of structural parts of equipment in metallurgy and mining. An ultrasonic vibration method with a stationary sample pursuant to the ASTM G32 standard was used to evaluate the possibility of the [...] Read more.
This paper examines the possibility of using basalt-based glass ceramics for construction of structural parts of equipment in metallurgy and mining. An ultrasonic vibration method with a stationary sample pursuant to the ASTM G32 standard was used to evaluate the possibility of the glass ceramic samples application in such operating conditions. As the starting material for synthesis of samples, olivine–pyroxene basalt from the locality Vrelo–Kopaonik Mountain (Serbia) was used. In order to obtain pre-determined structure and properties of basalt-based glass ceramics, raw material preparation methods through the sample crushing, grinding, and mechanical activation processes have been examined together with sample synthesis by means of melting, casting, and thermal treatment applied for the samples concerned. The mass loss of samples in function of the cavitation time was monitored. Sample surface degradation level was quantified using the image analysis. During the test, changes in sample morphology were monitored by means of the scanning electronic microscopy method. The results showed that basalt-based glass ceramics are highly resistant to cavitation wear and can be used in similar exploitation conditions as a substitute for other metal materials. Full article
(This article belongs to the Special Issue Mechanical Properties and Applications of Advanced Ceramics)
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<p>X-ray diffraction (XRD) of basalt samples: (<b>a</b>) raw basalt; (<b>b</b>) basalt-based glass ceramics.</p> Full article ">Figure 2
<p>Scanning electron microscopy (SEM) microphotographs of basalt samples: (<b>a</b>) raw basalt; (<b>b</b>) glass-ceramic based on basalt.</p> Full article ">Figure 3
<p>Microphotographs of raw basalt (RB) and basalt-based glass ceramic (GCB) samples: (<b>a</b>) crystals of olivine in the basis of plagioclases; (<b>b</b>) elongated phenocrystals of plagioclases; (<b>c</b>) cryptocrystalline glass basis of GCB sample; (<b>d</b>) altered spinel with bubble partially filled with glass.</p> Full article ">Figure 4
<p>The present bubbles in the basalt structure: (<b>a</b>) raw basalt (RB) sample; (<b>b</b>) basalt-based glass ceramic (GCB) sample.</p> Full article ">Figure 5
<p>Results of raw basalt (RB) and basalt-based glass ceramic (GCB) samples during the cavitation erosion testing: (<b>a</b>) mass loss of samples; (<b>b</b>) surface degradation level; (<b>c</b>) average area of the formed pits; (<b>d</b>) number of the formed pits.</p> Full article ">Figure 6
<p>Photos of both raw and glass ceramics based on basalt samples before and during cavitation erosion test after implementation of red filter and respective line profiles.</p> Full article ">Figure 7
<p>Scanning electron microscopy (SEM) micro-photos of deformed raw basalt (RB) sample surfaces with different magnitudes (500× left, 1000× right) and cavitation effects times: (<b>a</b>,<b>b</b>) 15 min; (<b>c</b>,<b>d</b>) 30 min; (<b>e</b>,<b>f</b>) 60 min; (<b>g</b>,<b>h</b>) 120 min.</p> Full article ">Figure 8
<p>Scanning electron microscopy (SEM) micro-photos of deformed basalt-based glass ceramic (GCB) sample surface with different magnitude (500× left, 1000× right) and cavitation effect times: (<b>a</b>,<b>b</b>) 15 min; (<b>c</b>,<b>d</b>) 30 min; (<b>e</b>,<b>f</b>) 60 min; (<b>g</b>,<b>h</b>) 120 min.</p> Full article ">
25 pages, 7156 KiB  
Article
Ti–Zr–Si–Nb Nanocrystalline Alloys and Metallic Glasses: Assessment on the Structure, Thermal Stability, Corrosion and Mechanical Properties
by Camelia Gabor, Daniel Cristea, Ioana-Laura Velicu, Tibor Bedo, Andrea Gatto, Elena Bassoli, Bela Varga, Mihai Alin Pop, Victor Geanta, Radu Stefanoiu, Mirela Maria Codescu, Eugen Manta, Delia Patroi, Monica Florescu, Sorin Ion Munteanu, Ioana Ghiuta, Nicoleta Lupu and Daniel Munteanu
Materials 2019, 12(9), 1551; https://doi.org/10.3390/ma12091551 - 12 May 2019
Cited by 8 | Viewed by 4543
Abstract
The development of novel Ti-based amorphous or β-phase nanostructured metallic materials could have significant benefits for implant applications, due to improved corrosion and mechanical characteristics (lower Young’s modulus, better wear performance, improved fracture toughness) in comparison to the standardized α+β titanium [...] Read more.
The development of novel Ti-based amorphous or β-phase nanostructured metallic materials could have significant benefits for implant applications, due to improved corrosion and mechanical characteristics (lower Young’s modulus, better wear performance, improved fracture toughness) in comparison to the standardized α+β titanium alloys. Moreover, the devitrification phenomenon, occurring during heating, could contribute to lower input power during additive manufacturing technologies. Ti-based alloy ribbons were obtained by melt-spinning, considering the ultra-fast cooling rates this method can provide. The titanium alloys contain in various proportions Zr, Nb, and Si (Ti60Zr10Si15Nb15, Ti64Zr10Si15Nb11, Ti56Zr10Si15Nb19) in various proportions. These elements were chosen due to their reported biological safety, as in the case of Zr and Nb, and the metallic glass-forming ability and biocompatibility of Si. The morphology and chemical composition were analyzed by scanning electron microscopy and energy-dispersive X-ray spectroscopy, while the structural features (crystallinity, phase attribution after devitrification (after heat treatment)) were assessed by X-ray diffraction. Some of the mechanical properties (hardness, Young’s modulus) were assessed by instrumented indentation. The thermal stability and crystallization temperatures were measured by differential thermal analysis. High-intensity exothermal peaks were observed during heating of melt-spun ribbons. The corrosion behavior was assessed by electrocorrosion tests. The results show the potential of these alloys to be used as materials for biomedical applications. Full article
(This article belongs to the Section Biomaterials)
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<p>X-Ray Diffraction patterns of Ti–Zr–Si–Nb bulk alloys.</p> Full article ">Figure 2
<p>X-ray diffraction patterns of Ti–Zr–Si–Nb alloys obtained with 28 m/s peripheral speed—MS1.</p> Full article ">Figure 3
<p>X-ray diffraction patterns of Ti–Zr–Si–Nb alloys obtained with 36 m/s peripheral speed—MS2.</p> Full article ">Figure 4
<p>X-ray diffraction patterns of Ti–Zr–Si–Nb alloys obtained with 36 m/s peripheral speed—MS2, after heat treatment.</p> Full article ">Figure 5
<p>Surface morphology and chemical mapping for the bulk Ti<sub>60</sub>Zr<sub>10</sub>Si<sub>15</sub>Nb<sub>15</sub> alloy.</p> Full article ">Figure 6
<p>Surface morphology and chemical mapping for the bulk Ti<sub>64</sub>Zr<sub>10</sub>Si<sub>15</sub>Nb<sub>11</sub> alloy.</p> Full article ">Figure 7
<p>Surface morphology and chemical mapping for the bulk Ti<sub>56</sub>Zr<sub>10</sub>Si<sub>15</sub>Nb<sub>19</sub> alloy.</p> Full article ">Figure 8
<p>Surface morphology and chemical mapping (Si) for the melt spun alloys, obtained with 28 m/s peripheral speed.</p> Full article ">Figure 9
<p>Surface morphology for the melt spun alloys, obtained with 36 m/s peripheral speed.</p> Full article ">Figure 10
<p>Hardness and Young’s modulus as a function of processing parameters.</p> Full article ">Figure 11
<p>Instrumented indentation loading-unloading curves for the Ti<sub>64</sub>Zr<sub>10</sub>Si<sub>15</sub>Nb<sub>11</sub> bulk alloy, obtained on the softer eutectic and the harder intermetallic compound.</p> Full article ">Figure 12
<p>Instrumented indentation imprints on the thermally treated melt-spun ribbons: (<b>a</b>) Ti<sub>60</sub>Zr<sub>10</sub>Si<sub>15</sub>Nb<sub>15</sub> ribbon—MS2; (<b>b</b>) Ti<sub>64</sub>Zr<sub>10</sub>Si<sub>15</sub>Nb<sub>11</sub> ribbon—MS2; (<b>c</b>) Ti<sub>56</sub>Zr<sub>10</sub>Si<sub>15</sub>Nb<sub>19</sub> ribbon—MS2.</p> Full article ">Figure 13
<p>Polarization curves in NaCl 0.9% for bulk alloy samples.</p> Full article ">Figure 14
<p>Evans diagrams in NaCl 0.9% for bulk alloy samples.</p> Full article ">Figure 15
<p>Nyquist impedance spectra in complex plane in NaCl 0.9% solution.</p> Full article ">Figure 16
<p>Equivalent electrical circuits for the bulk alloy samples: (<b>A</b>) For sample Ti<sub>60</sub>Zr<sub>10</sub>Si<sub>15</sub>Nb<sub>15</sub> and Ti<sub>64</sub>Zr<sub>10</sub>Si<sub>15</sub>Nb<sub>11</sub>, (<b>B</b>) for sample Ti<sub>56</sub>Zr<sub>10</sub>Si<sub>15</sub>Nb<sub>19</sub>.</p> Full article ">Figure 17
<p>Bode plots for NaCl 0.9%.</p> Full article ">Figure 18
<p>DTA variation as a function of temperature, up to 1530 °C, for Ti<sub>56</sub>Zr<sub>10</sub>Si<sub>15</sub>Nb<sub>19</sub> alloy, bulk (black) and melt-spun ribbons (green—MS1, blue—MS2).</p> Full article ">Figure 19
<p>DTA variation as a function of temperature, up to 1530 °C, for Ti<sub>60</sub>Zr<sub>10</sub>Si<sub>15</sub>Nb<sub>15</sub> alloy, bulk (black) and melt-spun ribbons (green—MS1, blue—MS2).</p> Full article ">Figure 20
<p>DTA variation as a function of temperature, up to 1530 °C, for Ti<sub>64</sub>Zr<sub>10</sub>Si<sub>15</sub>Nb<sub>11</sub> alloy, bulk (black) and melt-spun ribbons (green—MS1, blue—MS2).</p> Full article ">
12 pages, 3541 KiB  
Article
Key Role of Transfer Layer in Load Dependence of Friction on Hydrogenated Diamond-Like Carbon Films in Humid Air and Vacuum
by Yunhai Liu, Lei Chen, Bin Zhang, Zhongyue Cao, Pengfei Shi, Yong Peng, Ningning Zhou, Junyan Zhang and Linmao Qian
Materials 2019, 12(9), 1550; https://doi.org/10.3390/ma12091550 - 12 May 2019
Cited by 42 | Viewed by 3965
Abstract
The friction of hydrogenated diamond-like carbon (H-DLC) films was evaluated under the controlled environments of humid air and vacuum by varying the applied load. In humid air, there is a threshold applied load below which no obvious friction drop occurs and above which [...] Read more.
The friction of hydrogenated diamond-like carbon (H-DLC) films was evaluated under the controlled environments of humid air and vacuum by varying the applied load. In humid air, there is a threshold applied load below which no obvious friction drop occurs and above which the friction decreases to a relatively low level following the running-in process. By contrast, superlubricity can be realized at low applied loads but easily fails at high applied loads under vacuum conditions. Further analysis indicates that the graphitization of the sliding H-DLC surface has a negligible contribution to the sharp drop of friction during the running-in process under both humid air and vacuum conditions. The low friction in humid air and the superlow friction in vacuum are mainly attributed to the formation and stability of the transfer layer on the counterface, which depend on the load and surrounding environment. These results can help us understand the low-friction mechanism of H-DLC film and define optimized working conditions in practical applications, in which the transfer layer can be maintained for a long time under low applied load conditions in vacuum, whereas a high load can benefit the formation of the transfer layer in humid air. Full article
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<p>(<b>a</b>) Indentation force-depth curve of H-DLC film with maximum depth of 80 nm. (<b>b</b>) Raman spectrum of pristine H-DLC film. Two peaks involving D peak at ~1335 cm<sup>−1</sup> and G peak at ~1540 cm<sup>−1</sup> were deduced.</p> Full article ">Figure 2
<p>Friction behaviors of H-DLC films against Al<sub>2</sub>O<sub>3</sub> balls at different normal loads in (<b>a</b>,<b>b</b>) humid air and (<b>c</b>,<b>d</b>) vacuum. (<b>a</b>) and (<b>b</b>) respectively show sliding cycle dependence of friction coefficient and average friction coefficients in steady region as function of normal load in humid air. (<b>c</b>) and (<b>d</b>) respectively show friction coefficient curves and average friction coefficients in vacuum.</p> Full article ">Figure 3
<p>Three-dimensional images and corresponding cross-section profiles of wear tracks on H-DLC films formed at different normal loads in (<b>a</b>) humid air and (<b>b</b>) vacuum. Upper-left inset in each topographical picture shows AFM image inside wear track with scan area of 10 × 10 μm.</p> Full article ">Figure 4
<p>Raman spectra of worn surfaces on H-DLC films formed at various applied loads in (<b>a</b>) humid air and (<b>b</b>) vacuum.</p> Full article ">Figure 5
<p>Three-dimensional images of (top) Al<sub>2</sub>O<sub>3</sub> balls and (bottom) Raman spectra in contact regions on ball surfaces after sliding 6000 cycles in humid air (<b>a–c</b>) and vacuum (<b>d–f</b>). Loads were 1, 3, and 5 N, respectively.</p> Full article ">Figure 6
<p>Characterizations of Al<sub>2</sub>O<sub>3</sub> ball surface after sliding ~510 cycles and ~1000 cycles at 5 N in vacuum. (<b>a</b>) Friction coefficient decreases to superlubricity state at ~510 sliding cycles. (<b>b</b>,<b>c</b>) respectively show topography of used Al<sub>2</sub>O<sub>3</sub> ball and Raman spectrum measured in contact region during superlubricity stage. (<b>d</b>) Friction coefficient increases with superlubricity failure. (<b>e</b>,<b>f</b>) show topography and Raman spectrum of Al<sub>2</sub>O<sub>3</sub> ball surface in this stage.</p> Full article ">Figure 7
<p>Friction behaviors of H-DLC film slid against Al<sub>2</sub>O<sub>3</sub> ball in humid air following sliding tests in vacuum (10<sup>−3</sup> Pa) after ~5000 cycles. Upper insets compare topographical images of Al<sub>2</sub>O<sub>3</sub> ball after sliding tests in humid air (<b>A</b>) and vacuum (<b>B</b>). Sliding velocity and normal load were maintained at 200 mm/s and 10 N during entire experiment, respectively.</p> Full article ">Figure 8
<p>Schematics showing formation and stability of transfer layer on counterface after sliding H-DLC films at different load conditions in humid air and vacuum.</p> Full article ">
10 pages, 3025 KiB  
Article
Experimental Verification of Isotropic and Anisotropic Anhysteretic Magnetization Models
by Michał Nowicki, Roman Szewczyk and Paweł Nowak
Materials 2019, 12(9), 1549; https://doi.org/10.3390/ma12091549 - 11 May 2019
Cited by 13 | Viewed by 3973
Abstract
The anhysteretic magnetization curve is the key element of modeling magnetic hysteresis loops. Despite the fact that it is intensively exploited, known models of anhysteretic curve have not been verified experimentally. This paper presents the validation of four anhysteretic curve models considering four [...] Read more.
The anhysteretic magnetization curve is the key element of modeling magnetic hysteresis loops. Despite the fact that it is intensively exploited, known models of anhysteretic curve have not been verified experimentally. This paper presents the validation of four anhysteretic curve models considering four different materials, including isotropic, such as Mn-Zn soft ferrite, as well as anisotropic amorphous and nanocrystalline alloys. The presented results indicate that only the model that considers anisotropic energy is valid for a wide set of modern magnetic materials. The most suitable of the verified models is the anisotropic extension function-based model, which considers uniaxial anisotropy. Full article
(This article belongs to the Special Issue Soft Magnetic Materials: Synthesis, Characterization, and Applications)
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<p>Schematic diagram of measurement test stand.</p> Full article ">Figure 2
<p>Results of measurements of hysteresis loops and anhysteretic magnetization curves (anhysteretic magnetization curve: red line, magnetic hysteresis loop: blue line): (<b>a</b>) Mn-Zn ferrite F3001, (<b>b</b>) Co<sub>67</sub>Fe<sub>4</sub>Mo<sub>1</sub>B<sub>11</sub>Si<sub>17</sub> amorphous alloy, (<b>c</b>) Fe<sub>73.5</sub>Cu<sub>1</sub>Nb<sub>3</sub>Si<sub>15.5</sub>B<sub>7</sub> nanocrystalline alloy with perpendicular anisotropy, (<b>d</b>) Fe<sub>67</sub>Co<sub>18</sub>B<sub>14</sub>Si<sub>1</sub> amorphous alloy with parallel anisotropy.</p> Full article ">Figure 3
<p>Results of modeling the anhysteretic curve using the erf-based function (measurements: red line, modeling: black line): (<b>a</b>) Mn-Zn ferrite F3001, (<b>b</b>) Co<sub>67</sub>Fe<sub>4</sub>Mo<sub>1</sub>B<sub>11</sub>Si<sub>17</sub> amorphous alloy, (<b>c</b>) Fe<sub>73.5</sub>Cu<sub>1</sub>Nb<sub>3</sub>Si<sub>15.5</sub>B<sub>7</sub> nanocrystalline alloy with perpendicular anisotropy, (<b>d</b>) Fe<sub>67</sub>Co<sub>18</sub>B<sub>14</sub>Si<sub>1</sub> amorphous alloy with parallel anisotropy.</p> Full article ">Figure 4
<p>Results of modeling the anhysteretic curve using the exp-based function (measurements: red line, modeling: black line): (<b>a</b>) Mn-Zn ferrite F3001, (<b>b</b>) Co<sub>67</sub>Fe<sub>4</sub>Mo<sub>1</sub>B<sub>11</sub>Si<sub>17</sub> amorphous alloy, (<b>c</b>) Fe<sub>73.5</sub>Cu<sub>1</sub>Nb<sub>3</sub>Si<sub>15.5</sub>B<sub>7</sub> nanocrystalline alloy with perpendicular anisotropy, (<b>d</b>) Fe<sub>67</sub>Co<sub>18</sub>B<sub>14</sub>Si<sub>1</sub> amorphous alloy with parallel anisotropy.</p> Full article ">Figure 5
<p>Results of modeling the anhysteretic curve using the arctan-based function (measurements: red line, modeling: black line): (<b>a</b>) Mn-Zn ferrite F3001, (<b>b</b>) Co<sub>67</sub>Fe<sub>4</sub>Mo<sub>1</sub>B<sub>11</sub>Si<sub>17</sub> amorphous alloy, (<b>c</b>) Fe<sub>73.5</sub>Cu<sub>1</sub>Nb<sub>3</sub>Si<sub>15.5</sub>B<sub>7</sub> nanocrystalline alloy with perpendicular anisotropy, (<b>d</b>) Fe<sub>67</sub>Co<sub>18</sub>B<sub>14</sub>Si<sub>1</sub> amorphous alloy with parallel anisotropy.</p> Full article ">Figure 6
<p>Results of modeling the anhysteretic curve using the isotropic Langevin function (measurements: red line, modeling: black line): (<b>a</b>) Mn-Zn ferrite F3001, (<b>b</b>) Co<sub>67</sub>Fe<sub>4</sub>Mo<sub>1</sub>B<sub>11</sub>Si<sub>17</sub> amorphous alloy, (<b>c</b>) Fe<sub>73.5</sub>Cu<sub>1</sub>Nb<sub>3</sub>Si<sub>15.5</sub>B<sub>7</sub> nanocrystalline alloy with perpendicular anisotropy, (<b>d</b>) Fe<sub>67</sub>Co<sub>18</sub>B<sub>14</sub>Si<sub>1</sub> amorphous alloy with parallel anisotropy.</p> Full article ">Figure 7
<p>Results of modeling the anhysteretic curve using the anisotropic extension-based model (measurements: red line, modeling: black line): (<b>a</b>) Mn-Zn ferrite F3001, (<b>b</b>) Co<sub>67</sub>Fe<sub>4</sub>Mo<sub>1</sub>B<sub>11</sub>Si<sub>17</sub> amorphous alloy, (<b>c</b>) Fe<sub>73.5</sub>Cu<sub>1</sub>Nb<sub>3</sub>Si<sub>15.5</sub>B<sub>7</sub> nanocrystalline alloy with perpendicular anisotropy, (<b>d</b>) Fe<sub>67</sub>Co<sub>18</sub>B<sub>14</sub>Si<sub>1</sub> amorphous alloy with parallel anisotropy.</p> Full article ">
7 pages, 1186 KiB  
Article
Generalized Stacking Fault Energy of {10-11}<11-23> Slip System in Mg-Based Binary Alloys: A First Principles Study
by Yuchen Dou, Hong Luo, Jing Zhang and Xiaohua Tang
Materials 2019, 12(9), 1548; https://doi.org/10.3390/ma12091548 - 11 May 2019
Cited by 9 | Viewed by 3179
Abstract
In this work, the generalized stacking fault energies (GSFEs) of {10-11}<11-23> slip system in a wide range of Mg-X (X = Ag, Al, Bi, Ca, Dy, Er, Gd, Ho, Li, Lu, Mn, Nd, Pb, Sc, Sm, Sn, Y, Yb, Zn and Zr) binary [...] Read more.
In this work, the generalized stacking fault energies (GSFEs) of {10-11}<11-23> slip system in a wide range of Mg-X (X = Ag, Al, Bi, Ca, Dy, Er, Gd, Ho, Li, Lu, Mn, Nd, Pb, Sc, Sm, Sn, Y, Yb, Zn and Zr) binary alloys has been studied. The doping concentration in the doping plane and the Mg-X system is 12.5 at.% and 1.79 at.%, respectively. Two slip modes (slip mode I and II) were considered. For pure magnesium, these two slip modes are equivalent to each other. However, substituting a solute atom into the magnesium matrix will cause different effects on these two slip modes. Based on the calculated GSFEs, two design maps were constructed to predict solute effects on the behavior of the {10-11}<11-23> dislocations. The design maps suggest that the addition of Ag, Al, Ca, Dy, Er, Gd, Ho, Lu, Nd, Sm, Y, Yb and Zn could facilitate the {10-11}<11-23> dislocations. Full article
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<p>Atomic configurations for the {10-11}&lt;11-23&gt; slip system. A solute atom is substituted into the fourth plane for the Mg55X1 systems. The iso-surface level is 0.0175 a0<sup>−3</sup> (a0: Bohr radius). (<b>a</b>) Slip mode I. The lower four layers of atoms are fixed; and the upper three layers of atoms are displaced along the 1/3[11-23] direction. (<b>b</b>) Slip mode II. The upper four layers of atoms are fixed; and the lower three layers of atoms are displaced along the 1/3[-1-12-3] direction. (<b>c</b>) Electronic structures of the Mg55Y1. Two periodic images are shown. The iso-surface level is 0.0175 a<sub>0</sub><sup>−3</sup> (a<sub>0</sub> is Bohr radius). (<b>d</b>) A slice view of electronic structure of the Mg55Y1. Two periodic images are shown.</p> Full article ">Figure 2
<p>Calculated {10-11}&lt;11-23&gt; generalized stacking fault energies (GSFEs) for pure magnesium and Mg55Y1. For pure magnesium, slip mode I is equal to slip mode II. However, substituting a solute atom into the magnesium matrix will cause different effects on these two slip modes. Taking Mg55Y1 as an example, under slip mode I, the stable SFE has disappeared.</p> Full article ">Figure 3
<p>Alloy effects on GSFE0.7 b and GSFE0.3b-GSFE0.4b. (<b>a</b>) Slip mode I. (<b>b</b>) Slip mode II. From left to right the probability of the mobile &lt;c+a&gt; transformation could get increased. From top to bottom, the nucleation of the {10-11}&lt;11-23&gt; dislocations could get easier.</p> Full article ">
20 pages, 4856 KiB  
Article
Ethylene Glycol Dicyclopentenyl (Meth)Acrylate Homo and Block Copolymers via Nitroxide Mediated Polymerization
by Alexandre Maupu, Yara Kanawati, Adrien Métafiot and Milan Maric
Materials 2019, 12(9), 1547; https://doi.org/10.3390/ma12091547 - 11 May 2019
Cited by 3 | Viewed by 4302
Abstract
Nitroxide-mediated polymerization (NMP), (homo and block copolymerization with styrene (S) and butyl methacrylate/S) of ethylene glycol dicyclopentenyl ether (meth)acrylates (EGDEA and EGDEMA) was studied using BlocBuilder alkoxyamines. EGDEA homopolymerization was not well-controlled, independent of temperature (90–120 °C), or additional free nitroxide (0–10 mol%) [...] Read more.
Nitroxide-mediated polymerization (NMP), (homo and block copolymerization with styrene (S) and butyl methacrylate/S) of ethylene glycol dicyclopentenyl ether (meth)acrylates (EGDEA and EGDEMA) was studied using BlocBuilder alkoxyamines. EGDEA homopolymerization was not well-controlled, independent of temperature (90–120 °C), or additional free nitroxide (0–10 mol%) used. Number average molecular weights (Mn) achieved for poly(EGDEA) were 4.0–9.5 kg mol−1 and were accompanied by high dispersity (Ð = Mw/Mn = 1.62–2.09). Re-initiation and chain extension of the poly(EGDEA) chains with styrene (S) indicated some block copolymer formation, but a high fraction of chains were terminated irreversibly. EGDEA-stat-S statistical copolymerizations with a low mol fraction S in initial feed, fS,0 = 0.05, were slightly better controlled compared to poly(EGDEA) homopolymerizations (Ð was reduced to 1.44 compared to 1.62 at similar conditions). EGDEMA, in contrast, was successfully polymerized using a small fraction of S (fS,0 ~ 10 mol%) to high conversion (72%) to form well-defined EGDEMA-rich random copolymer (molar composition = FEGDEMA = 0.87) of Mn = 14.3 kg mol−1 and Ð = 1.38. EGDEMA-rich compositions were also polymerized with the unimolecular succinimidyl ester form of BlocBuilder initiator, NHS-BlocBuilder with similar results, although Ðs were higher ~1.6. Chain extensions resulted in monomodal shifts to higher molecular weights, indicating good chain end fidelity. Full article
(This article belongs to the Special Issue Novel Materials and Applicaitons by Controlled Radical Polymerization)
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Graphical abstract

Graphical abstract
Full article ">Figure 1
<p>Structures of BlocBuilder, SG1 free nitroxide and ethylene glycol dicyclopentenyl ether (meth)acrylate (EGDEA and EGDEMA).</p> Full article ">Figure 2
<p><b><sup>1</sup></b>H NMR of a sample of the reaction mixture for the homopolymerization of EGDEA (Expt. ID: E-T90, temperature = 90 °C, t<sub>polymerization</sub> = 150 min, <span class="html-italic">M<sub>n</sub></span> = 3.0 kg mol<sup>−1</sup>, <span class="html-italic">Ð</span> = 1.54).</p> Full article ">Figure 3
<p><b><sup>1</sup></b>H NMR of an EGDEMA/S copolymer (EGDEMA/S-N-80-90) with <span class="html-italic">M<sub>n</sub></span> = 5.6 kg mol<sup>−1</sup>, <span class="html-italic">Ð</span> = 1.27, <span class="html-italic">F<sub>S</sub></span> = 0.77. Note that the cyclopentenyl peaks at about 5.5 ppm were used to indicate EGDEMA composition while the aromatic protons at 6.5–7.0 ppm were used to indicate S composition.</p> Full article ">Figure 4
<p>Semi-logarithmic kinetic plots of ln[(1−X)<sup>−1</sup>], where X represents the overall monomer conversion, versus time for ethylene glycol dicyclopentenyl ether acrylate (EGDEA) homopolymerizations at 90–120 °C via nitroxide mediated polymerization with BlocBuilder<sup>TM</sup> and 5 mol% additional SG1 free nitroxide relative to BlocBuilder<sup>TM</sup>.</p> Full article ">Figure 5
<p>Number average molecular weight (<span class="html-italic">M<sub>n</sub></span>) and dispersity (<span class="html-italic">Ð</span>) of homopolymers of ethylene glycol dicyclopentenyl ether acrylate (EGDEA) with <span class="html-italic">r</span> = 0.05 (added free SG1 nitroxide relative to BlocBuilder initially) at various temperatures (E-T90 = EGDEA homopolymerization at 90 °C; E-T100 = EGDEA homopolymerization at 100 °C; E-T110 = EGDEA homopolymerization at 110 °C; E-T120 = EGDEA homopolymerization at 120 °C). The straight solid line indicates the predicted <span class="html-italic">M<sub>n</sub></span> versus conversion if the polymerization was living (M<sub>n, theoretical</sub> at 100% conversion ≈ 20 kg mol<sup>−1</sup> for this set of polymerizations).</p> Full article ">Figure 6
<p>Semi-logarithmic kinetic plots of ln[(1−X)<sup>−1</sup>], where X represents the overall monomer conversion, versus time for ethylene glycol dicyclopentenyl ether acrylate (EGDEA) homopolymerizations at 90 °C via Nitroxide-Mediated Polymerization with BlocBuilder<sup>TM</sup> and <span class="html-italic">r</span> = 0–10% excess SG1 free nitroxide relative to BlocBuilder<sup>TM</sup>.</p> Full article ">Figure 7
<p>Number average molecular weight (<span class="html-italic">M<sub>n</sub></span>) and dispersity (<span class="html-italic">Ð</span>) of homopolymers of ethylene glycol dicyclopentenyl ether acrylate (EGDEA) measured by GPC calibrated with poly(methyl methacrylate) standards (symbols: E-0 (<span class="html-italic">r</span> = 0): blue diamonds, E-5: red squares (<span class="html-italic">r</span> = 0.05), E-10: green triangles (<span class="html-italic">r</span> = 0.10)).</p> Full article ">Figure 8
<p>Number-average molecular weight (<span class="html-italic">M<sub>n</sub></span>) and dispersity (<b>Ð</b>) versus conversion of (<b>a</b>) EGDEA homopolymerization and (<b>b</b>) EGDEA/S copolymerization with <span class="html-italic">f<sub>S</sub></span><sub>,0</sub> = 0.05 in the initial monomer composition at 90 °C. This data is referred to expt. IDs EGDEA and EGDEA/S in <a href="#materials-12-01547-t007" class="html-table">Table 7</a>.</p> Full article ">Figure 9
<p>Number-average molecular weight (<span class="html-italic">M<sub>n</sub></span>) and dispersity (<span class="html-italic">Ð</span>) of statistical copolymer of ethylene glycol dicyclopentenyl ether methacrylate (EGDEMA) and styrene (S) measured by GPC calibrated with poly(methyl methacrylate) standards (Expt. ID. EGDEMA/S in <a href="#materials-12-01547-t007" class="html-table">Table 7</a>). This polymerization was done at 90 °C in 50 wt.% dioxane solution.</p> Full article ">Figure 10
<p>GPC traces of corresponding macroinitiator EGDEA (dashed line, sample E-T90, <span class="html-italic">M<sub>n</sub></span> = 4.0 kg mol<sup>−1</sup>, <span class="html-italic">Ð</span> = 1.62) and chain extended block copolymer EGDEA-S (solid line, <span class="html-italic">M<sub>n</sub></span> = 58.6 kg mol<sup>−1</sup>, <span class="html-italic">Ð</span> = 1.97, <span class="html-italic">F<sub>EGDEA</sub></span> = 0.08). Chromatogram of chain-extended block copolymer showed no significant change after fractionation.</p> Full article ">Figure 11
<p>GPC chromatograms of the chain extension with styrene at 100 °C from a poly(EGDEMA-<span class="html-italic">stat</span>-S) macroinitiator (see <a href="#materials-12-01547-t008" class="html-table">Table 8</a> for properties of the macroinitiator with ID = EGDEMA/S-15-90).</p> Full article ">Figure 12
<p>GPC traces from an EGDEMA/S macroinitiator (EGDEMA/S-N-80-90, <span class="html-italic">M<sub>n</sub></span> = 5.6 kg mol<sup>−1</sup>, <span class="html-italic">Đ</span> = 1.27, <span class="html-italic">F<sub>EGDEMA</sub></span> = 0.23) to the chain extended species with BMA/S at various polymerizations to form the poly(EGDEMA/S-block-BMA/S) block copolymer (<span class="html-italic">M<sub>n</sub></span> = 32.3 kg mol<sup>−1</sup>, <span class="html-italic">Đ</span> = 1.69, <span class="html-italic">F<sub>BMA</sub></span>= 0.64, <span class="html-italic">F<sub>EGDEMA</sub></span> = 0.05).</p> Full article ">Figure 13
<p><sup>1</sup>H NMR spectrum in CDCl<sub>3</sub> of poly(EGDEMA/S-block-BMA/S) showing the integrations to provide the overall compositions of the block copolymer.</p> Full article ">
13 pages, 5218 KiB  
Article
Effect of Intermetallic Compounds on the Thermal and Mechanical Properties of Al–Cu Composite Materials Fabricated by Spark Plasma Sintering
by Kyungju Kim, Dasom Kim, Kwangjae Park, Myunghoon Cho, Seungchan Cho and Hansang Kwon
Materials 2019, 12(9), 1546; https://doi.org/10.3390/ma12091546 - 10 May 2019
Cited by 38 | Viewed by 4040
Abstract
Aluminium–copper composite materials were successfully fabricated using spark plasma sintering with Al and Cu powders as the raw materials. Al–Cu composite powders were fabricated through a ball milling process, and the effect of the Cu content was investigated. Composite materials composed of Al–20Cu, [...] Read more.
Aluminium–copper composite materials were successfully fabricated using spark plasma sintering with Al and Cu powders as the raw materials. Al–Cu composite powders were fabricated through a ball milling process, and the effect of the Cu content was investigated. Composite materials composed of Al–20Cu, Al–50Cu, and Al–80Cu (vol.%) were sintered by a spark plasma sintering process, which was carried out at 520 °C and 50 MPa for 5 min. The phase analysis of the composite materials by X-ray diffraction (XRD) and energy-dispersive spectroscopy (EDS) indicated that intermetallic compounds (IC) such as CuAl2 and Cu9Al4 were formed through reactions between Cu and Al during the spark plasma sintering process. The mechanical properties of the composites were analysed using a Vickers hardness tester. The Al–50Cu composite had a hardness of approximately 151 HV, which is higher than that of the other composites. The thermal conductivity of the composite materials was measured by laser flash analysis, and the highest value was obtained for the Al–80Cu composite material. This suggests that the Cu content affects physical properties of the Al–Cu composite material as well as the amount of intermetallic compounds formed in the composite material. Full article
(This article belongs to the Special Issue Thermal Analysis of Materials)
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<p>Scanning electron microscopy (SEM) images of (<b>a</b>) pure Al, (<b>b</b>) pure Cu, (<b>c</b>) Al–20Cu, (<b>d</b>) Al–50Cu, and (<b>e</b>) Al–80Cu powders, and (<b>f</b>) X-ray diffraction (XRD) patterns of the composite powders.</p> Full article ">Figure 2
<p>(<b>a</b>) Photograph of the Al–Cu composites after spark plasma sintering (SPS), (<b>b</b>) evolution of the relative density of composites, and (<b>c</b>) cross-sectional light microscopy images.</p> Full article ">Figure 3
<p>Variation of (<b>a</b>) the temperature and (<b>b</b>) displacement, as function of holding time SPS.</p> Full article ">Figure 4
<p>SEM micrographs of (<b>a</b>) Al–20Cu, (<b>b</b>) Al–50Cu, and (<b>c</b>) Al–80Cu composites, and (<b>d</b>) XRD patterns of Al–Cu composites.</p> Full article ">Figure 5
<p>SEM micrograph and energy-dispersive spectroscopy (EDS) line scanning results along the yellow line for (<b>a</b>) Al–20Cu, (<b>b</b>) Al–50Cu, and (<b>c</b>) Al–80Cu.</p> Full article ">Figure 6
<p>Area fractions of Al, Cu, Cu<sub>9</sub>Al<sub>4</sub>, and CuAl<sub>2</sub> obtained using image analysis software ImageJ: (<b>a</b>) Al–20Cu, (<b>b</b>) Al–50Cu, and (<b>c</b>) Al–80Cu.</p> Full article ">Figure 7
<p>Vickers hardness of the fabricated pure Al, pure Cu, and Al–Cu composites.</p> Full article ">
15 pages, 2453 KiB  
Article
Reliability-Based Low Fatigue Life Analysis of Turbine Blisk with Generalized Regression Extreme Neural Network Method
by Chunyi Zhang, Jingshan Wei, Huizhe Jing, Chengwei Fei and Wenzhong Tang
Materials 2019, 12(9), 1545; https://doi.org/10.3390/ma12091545 - 10 May 2019
Cited by 34 | Viewed by 3964
Abstract
Turbine blisk low cycle fatigue (LCF) is affected by various factors such as heat load, structural load, operation parameters and material parameters; it seriously influences the reliability and performance of the blisk and aeroengine. To study the influence of thermal-structural coupling on the [...] Read more.
Turbine blisk low cycle fatigue (LCF) is affected by various factors such as heat load, structural load, operation parameters and material parameters; it seriously influences the reliability and performance of the blisk and aeroengine. To study the influence of thermal-structural coupling on the reliability of blisk LCF life, the generalized regression extreme neural network (GRENN) method was proposed by integrating the basic thoughts of generalized regression neural network (GRNN) and the extreme response surface method (ERSM). The mathematical model of the developed GRENN method was first established in respect of the LCF life model and the ERSM model. The method and procedure for reliability and sensitivity analysis based on the GRENN model were discussed. Next, the reliability and sensitivity analyses of blisk LCF life were performed utilizing the GRENN method under a thermal-structural interaction by regarding the randomness of gas temperature, rotation speed, material parameters, LCF performance parameters and the minimum fatigue life point of the objective of study. The analytical results reveal that the reliability degree was 0.99848 and the fatigue life is 9419 cycles for blisk LCF life when the allowable value is 6000 cycles so that the blisk has some life margin relative to 4500 cycles in the deterministic analysis. In comparison with ERSM, the computing time and precision of the proposed GRENN under 10,000 simulations is 1.311 s and 99.95%. This is improved by 15.18% in computational efficiency and 1.39% in accuracy, respectively. Moreover, high efficiency and high precision of the developed GRENN become more obvious with the increasing number of simulations. In light of the sensitivity analysis, the fatigue ductility index and temperature are the key factors of determining blisk LCF life because their effect probabilities reach 41% and 26%, respectively. Material density, rotor speed, the fatigue ductility coefficient, the fatigue strength coefficient and the fatigue ductility index are also significant parameters for LCF life. Poisson’s ratio and elastic modulus of materials have little effect. The efforts of this paper validate the feasibility and validity of GRENN in the reliability analysis of blisk LCF life and give the influence degrees of various random parameters on blisk LCF life, which are promising to provide useful insights for the probabilistic optimization of turbine blisk LCF life. Full article
(This article belongs to the Special Issue Advanced Approaches Applied to Materials Development and Design Predictions)
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<p>Schematic diagram of generalized regression extreme neural network (GRENN) method.</p> Full article ">Figure 2
<p>Flow chart of reliability analysis with GRENN method.</p> Full article ">Figure 3
<p>FE model and gridding of a turbine blisk.</p> Full article ">Figure 4
<p>Nephgrams of the responses of blisk stress and fatigue life.</p> Full article ">Figure 5
<p>Predicted results of the GRENN model with 30 groups of samples.</p> Full article ">Figure 6
<p>Reliability analysis results of blisk fatigue life with the GRENN method.</p> Full article ">Figure 7
<p>Sensitivity degree distributions of random parameters on blisk LCF life.</p> Full article ">
17 pages, 3702 KiB  
Article
Prediction and Sensitivity Analysis of Bubble Dissolution Time in 3D Selective Laser Sintering Using Ensemble Decision Trees
by Hai-Bang Ly, Eric Monteiro, Tien-Thinh Le, Vuong Minh Le, Morgan Dal, Gilles Regnier and Binh Thai Pham
Materials 2019, 12(9), 1544; https://doi.org/10.3390/ma12091544 - 10 May 2019
Cited by 68 | Viewed by 4883
Abstract
The presence of defects like gas bubble in fabricated parts is inherent in the selective laser sintering process and the prediction of bubble shrinkage dynamics is crucial. In this paper, two artificial intelligence (AI) models based on Decision Trees algorithm were constructed in [...] Read more.
The presence of defects like gas bubble in fabricated parts is inherent in the selective laser sintering process and the prediction of bubble shrinkage dynamics is crucial. In this paper, two artificial intelligence (AI) models based on Decision Trees algorithm were constructed in order to predict bubble dissolution time, namely the Ensemble Bagged Trees (EDT Bagged) and Ensemble Boosted Trees (EDT Boosted). A metadata including 68644 data were generated with the help of our previously developed numerical tool. The AI models used the initial bubble size, external domain size, diffusion coefficient, surface tension, viscosity, initial concentration, and chamber pressure as input parameters, whereas bubble dissolution time was considered as output variable. Evaluation of the models’ performance was achieved by criteria such as Mean Absolute Error (MAE), Root Mean Squared Error (RMSE) and coefficient of determination (R2). The results showed that EDT Bagged outperformed EDT Boosted. Sensitivity analysis was then conducted thanks to the Monte Carlo approach and it was found that three most important inputs for the problem were the diffusion coefficient, initial concentration, and bubble initial size. This study might help in quick prediction of bubble dissolution time to improve the production quality from industry. Full article
(This article belongs to the Special Issue Selective Laser Sintering (SLS) of Materials)
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<p>Schematization of using Monte Carlo method for the propagation of input variability.</p> Full article ">Figure 2
<p>Methodology of the proposed analysis.</p> Full article ">Figure 3
<p>Histogram of relative error between predicted and output values of training (<b>left</b>) and testing (<b>right</b>) part of Ensemble Bagged Trees (EDT Bagged) and Ensemble Boosted Trees (EDT Boosted) algorithms.</p> Full article ">Figure 4
<p>Error distribution (Root Mean Squared Error (RMSE), Mean Absolute Error (MAE), and coefficient of determination (R<sup>2</sup>)) of different models for 1000 simulations: (<b>a</b>–<b>c</b>) EDT Boosted and (<b>d</b>–<b>f</b>) EDT Bagged algorithms.</p> Full article ">Figure 5
<p>Statistical convergence analysis of (<b>a</b>) RMSE, (<b>b</b>) MAE, and (<b>c</b>) R<sup>2</sup> over 1000 Monte Carlo simulations for EDT Bagged and EDT Boosted algorithms. Blue lines representing ±1% deviation around the average value.</p> Full article ">Figure 6
<p>Histogram of RMSE, MAE, and R<sup>2</sup> for 14,000 simulations in case of: (<b>a</b>–<b>c</b>) EDT Boosted model, and (<b>d</b>–<b>f</b>) EDT Bagged algorithm.</p> Full article ">Figure 7
<p>Statistical convergence analysis of RMSE, MAE, and R<sup>2</sup> in case of: (<b>a</b>–<b>c</b>) diffusion coefficient excluded, (<b>d</b>–<b>f</b>) initial saturation excluded, and (<b>g</b>–<b>i</b>) initial bubble size excluded. Blue lines representing ±1% deviation around the average value.</p> Full article ">
24 pages, 13363 KiB  
Review
Synthetic Polymer Aerogels in Particulate Form
by Patrina Paraskevopoulou, Despoina Chriti, Grigorios Raptopoulos and George C. Anyfantis
Materials 2019, 12(9), 1543; https://doi.org/10.3390/ma12091543 - 10 May 2019
Cited by 36 | Viewed by 6490
Abstract
Aerogels have been defined as solid colloidal or polymeric networks of nanoparticles that are expanded throughout their entire volume by a gas. They have high surface areas, low thermal conductivities, low dielectric constants, and high acoustic attenuation, all of which are very attractive [...] Read more.
Aerogels have been defined as solid colloidal or polymeric networks of nanoparticles that are expanded throughout their entire volume by a gas. They have high surface areas, low thermal conductivities, low dielectric constants, and high acoustic attenuation, all of which are very attractive properties for applications that range from thermal and acoustic insulation to dielectrics to drug delivery. However, one of the most important impediments to that potential has been that most efforts have been concentrated on monolithic aerogels, which are prone to defects and their production requires long and costly processing. An alternative approach is to consider manufacturing aerogels in particulate form. Recognizing that need, the European Commission funded “NanoHybrids”, a 3.5 years project under the Horizon 2020 framework with 12 industrial and academic partners aiming at aerogel particles from bio- and synthetic polymers. Biopolymer aerogels in particulate form have been reviewed recently. This mini-review focuses on the emerging field of particulate aerogels from synthetic polymers. That category includes mostly polyurea aerogels, but also some isolated cases of polyimide and phenolic resin aerogels. Particulate aerogels covered include powders, micro granules and spherical millimeter-size beads. For the benefit of the reader, in addition to the literature, some new results from our laboratory concerning polyurea particle aerogels are also included. Full article
(This article belongs to the Special Issue Aerogels and Their Functionalization for Practical Applications)
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<p>SEM images of PUA powders precipitated into acetone from the sols of the monomer pairs, as indicated, at 50% reaction conversion. Initial solution concentration: 0.04 g mL<sup>–1</sup>. Scale bar: 400 nm. Adapted from Ref. [<a href="#B89-materials-12-01543" class="html-bibr">89</a>] with permission from The Royal Society of Chemistry.</p> Full article ">Figure 2
<p>SEM images of the polymers prepared from the reaction of 2,4-TDI and 4,4′-ODA in acetone at 30 °C for 4 h under reciprocating shaking (150 oscillations per min), at five different monomer concentrations (% w/w), as indicated. Adapted from Ref. [<a href="#B90-materials-12-01543" class="html-bibr">90</a>] with permission from The Royal Society of Chemistry.</p> Full article ">Figure 3
<p>SEM images of PUA particles prepared at 30 °C in acetonitrile (<b>a</b>), and in acetone (<b>b</b>) under reciprocating shaking (150 oscillations per minute). Monomer concentration: 1.0% w/w [<a href="#B90-materials-12-01543" class="html-bibr">90</a>]. Adapted from Ref. [<a href="#B90-materials-12-01543" class="html-bibr">90</a>] with permission from The Royal Society of Chemistry.</p> Full article ">Figure 4
<p>(<b>a</b>) Experimental setup for the synthesis of PUA aerogel powders with disruption of gelation (vigorous agitation, 250–300 rpm; suspension and emulsion polymerization, 400 rpm). (<b>b</b>) The half-moon shaped blade used for agitation.</p> Full article ">Figure 5
<p>Photographs and SEM images at different magnifications of PUA powders prepared from Desmodur N3300 and water in propylene carbonate (<b>a</b>) or acetone (<b>b</b>) via vigorous agitation of the sol (monomer concentration: 5.5% w/w). Scale lengths are indicated in the right-bottom corner of each frame.</p> Full article ">Figure 6
<p>Photograph and SEM images at different magnifications of PUA powder prepared from Desmodur N3300 and water in propylene carbonate/hexane via suspension polymerization (monomer concentration: 11% w/w). Scale lengths are indicated in the right-bottom corner of each frame.</p> Full article ">Figure 7
<p>Photographs and SEM images at different magnifications of PUA powders prepared from Desmodur N3300 in propylene carbonate/hexane via emulsion polymerization. (<b>a</b>) CTAB 3.5% w/w; monomer concentration: 5.5% w/w. (<b>b</b>) CTAB 0.7% w/w; monomer concentration: 2.75% w/w. (<b>c</b>) CTAB 3.5% w/w; monomer concentration: 2.75% w/w. (<b>d</b>) NIKKOL BL-9EX 0.7% w/w; monomer concentration: 11% w/w. Scale lengths are indicated in the right-bottom corner of each frame.</p> Full article ">Figure 8
<p>Photographs and SEM images at different magnifications of PUA powders prepared from Desmodur RE (monomer concentration: 4% w/w) and water in: (<b>a</b>) DMF via vigorous agitation of the sol and (<b>b</b>) DMF/hexane via precipitation polymerization. Scale lengths are indicated in the right-bottom corner of each frame.</p> Full article ">Figure 9
<p>Photographs of PUA aerogel beads (wet-gels and aerogels) [<a href="#B94-materials-12-01543" class="html-bibr">94</a>].</p> Full article ">Figure 10
<p>SEM images of spherical PUA aerogel beads at different magnifications: skin and interior, as indicated [<a href="#B94-materials-12-01543" class="html-bibr">94</a>].</p> Full article ">Figure 11
<p>Photograph (<b>a</b>) and SEM image (<b>b</b>) of PI aerogel powders obtained from the imidization of PMDA/4,4′-MDA-derived PAA. Adapted by permission from Springer Nature Customer Service Centre GmbH: Ref. [<a href="#B98-materials-12-01543" class="html-bibr">98</a>].</p> Full article ">Figure 12
<p>SEM images of: (<b>a</b>) PI aerogel microparticles, (<b>b</b>) their skeletal networks in comparison with corresponding monoliths, and (<b>c</b>) the surface of PI aerogel microparticles. Adapted with permission from Ref. [<a href="#B54-materials-12-01543" class="html-bibr">54</a>]. Copyright 2016 American Chemical Society.</p> Full article ">Figure 13
<p>(<b>a</b>) Setup for the fabrication of PI aerogel microparticles. (<b>b</b>) Glass bottle with PAA before curing. (<b>c</b>) PI aerogel microparticles after curing. Copyright (2014) Wiley. Used with permission from Ref. [<a href="#B99-materials-12-01543" class="html-bibr">99</a>].</p> Full article ">Figure 14
<p>SEM images of: (<b>a</b>) PI aerogel microparticles; (<b>b</b>,<b>c</b>) their surfaces; (<b>d</b>,<b>e</b>) their interior. Copyright (2014) Wiley. Used with permission from Ref. [<a href="#B99-materials-12-01543" class="html-bibr">99</a>].</p> Full article ">Figure 15
<p>SEM image of the interior of a PI aerogel monolith derived from PMDA, 4,4′-ODA and TAPB. Copyright (2007) Wiley. Used with permission from Ref. [<a href="#B100-materials-12-01543" class="html-bibr">100</a>].</p> Full article ">Figure 16
<p>SEM images of outer surfaces (<b>a</b>,<b>c</b>) and inner surfaces of skins and bulk morphologies (<b>b</b>,<b>d</b>) of RF foam aerogel beads obtained via reactions catalyzed by triethylamine (a, b: 0.39% w/w), or tri(n-butyl)amine (c, d: 0.039% w/w). Scale bar: 2 μm. Reprinted by permission of Taylor &amp; Francis Ltd., <a href="http://www.tandfonline.com" target="_blank">http://www.tandfonline.com</a>, Ref. [<a href="#B111-materials-12-01543" class="html-bibr">111</a>].</p> Full article ">Figure 17
<p>SEM image of: (<b>a</b>) PBO aerogel microparticles (inset: surface of the sphere), (<b>b</b>) fractured surface of PBZ aerogel microparticles, and (<b>c</b>,<b>d</b>) ensemble of spherical polybenzoxazine domains that formed the internal structure of aerogel microparticles and monolith, respectively. Adapted with permission from Ref. [<a href="#B54-materials-12-01543" class="html-bibr">54</a>]. Copyright 2016 American Chemical Society.</p> Full article ">Scheme 1
<p>Synthesis of PUA aerogels from isocyanates and amines (<b>a</b>), isocyanates and water (<b>b</b>), or isocyanates and boric acid (<b>c</b>).</p> Full article ">Scheme 2
<p>Structures of the di- and triisocyanates used for the synthesis of the materials discussed in this review.</p> Full article ">Scheme 3
<p>Structures of the di- and tetraamines used for the synthesis of the materials discussed in this review.</p> Full article ">Scheme 4
<p>Structures of surfactants CTAB and NIKKOL BL-9EX.</p> Full article ">Scheme 5
<p>Synthesis of chemically identical polyimide (PI) aerogels via two different routes: (<b>a</b>) from a dianhydride and a diamine (the DuPont route), (<b>b</b>) from the same dianhydride and the corresponding diisocyanate to the diamine of part (a). PMDA: pyromellitic dianhydride; 4,4′-MDA: 4,4′-diaminodiphenylmethane; and, 4,4′-MDI: 4,4′-methylenebis(phenyl isocyanate).</p> Full article ">Scheme 6
<p><b>Scheme 6</b>. Synthesis of RF aerogels.</p> Full article ">Scheme 7
<p>Synthesis of PBO aerogels via polymerization of a BO monomer derived from the reaction of bisphenol A, aniline, and formaldehyde.</p> Full article ">
12 pages, 3703 KiB  
Article
Fluoride Fiber-Based Plasmonic Biosensor with Two-Dimensional Material Heterostructures: Enhancement of Overall Figure-of-Merit via Optimization of Radiation Damping in Near Infrared Region
by Anuj K. Sharma, Ankit Kumar Pandey and Baljinder Kaur
Materials 2019, 12(9), 1542; https://doi.org/10.3390/ma12091542 - 10 May 2019
Cited by 19 | Viewed by 3639
Abstract
Two-dimensional (2D) heterostructure materials show captivating properties for application in surface plasmon resonance (SPR) sensors. A fluoride fiber-based SPR sensor is proposed and simulated with the inclusion of a 2D heterostructure as the analyte interacting layer. The monolayers of two 2D heterostructures (BlueP/MoS [...] Read more.
Two-dimensional (2D) heterostructure materials show captivating properties for application in surface plasmon resonance (SPR) sensors. A fluoride fiber-based SPR sensor is proposed and simulated with the inclusion of a 2D heterostructure as the analyte interacting layer. The monolayers of two 2D heterostructures (BlueP/MoS2 and BlueP/WS2, respectively) are considered in near infrared (NIR). In NIR, an HBL (62HfF4-33BaF2-5LaF3) fluoride glass core and NaF clad are considered. The emphasis is placed on figure of merit (FOM) enhancement via optimization of radiation damping through simultaneous tuning of Ag thickness (dm) and NIR wavelength (λ) at the Ag-2D heterostructure–analyte interfaces. Field distribution analysis is performed in order to understand the interaction of NIR signal with analyte at optimum radiation damping (ORD) condition. While the ORD leads to significantly larger FOM for both, the BlueP/MoS2 (FOM = 19179.69 RIU−1 (RIU: refractive index unit) at dm = 38.2 nm and λ = 813.4 nm)-based sensor shows massively larger FOM compared with the BlueP/WS2 (FOM = 7371.30 RIU−1 at dm = 38.2 nm and λ = 811.2 nm)-based sensor. The overall sensing performance was more methodically evaluated in terms of the low degree of photodamage of the analyte, low signal scattering, high power loss, and large field variation. The BlueP/MoS2-based fiber SPR sensor under ORD conditions opens up new paths for biosensing with highly enhanced overall performance. Full article
(This article belongs to the Special Issue Flexible Sensors and Actuators for Novel Wearable Solutions)
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<p>Schematic diagram of the proposed multilayered FOSPR sensor with output power loss spectra. L is the sensing length of fiber, D is the fiber core diameter. The BlueP/TMD layer acts as the analyte interacting layer.</p> Full article ">Figure 2
<p>Spectral variation of the real part (n) and imaginary part (κ) of RI for monolayer (<b>a</b>) BlueP/WS<sub>2</sub> heterostructure, and (<b>b</b>) BlueP/MoS<sub>2</sub> heterostructure (this is the interpolated graph based on discrete data provided by ref [<a href="#B24-materials-12-01542" class="html-bibr">24</a>]).</p> Full article ">Figure 3
<p>Simulated 2D (d<sub>m</sub>, λ) variation of FOM of a BlueP/WS<sub>2</sub> heterostructure-based fiber SPR sensor. The magnified figure in the inset shows the maximum achieved FOM value for the optimized set of d<sub>m</sub> and λ values.</p> Full article ">Figure 4
<p>Simulated 2D (dm, λ) variation of FOM of a BlueP/MoS<sub>2</sub> heterostructure-based fiber SPR sensor. The magnified figure in the inset shows the maximum achieved FOM value for the optimized set of d<sub>m</sub> and λ values.</p> Full article ">Figure 5
<p>Simulated power loss (dB) variation with α (deg.) for N-MET analyte with d<sub>m</sub> = 38.20 nm for proposed fiber SPR sensor with (<b>a</b>) BlueP/WS<sub>2</sub> heterostructure and (<b>b</b>) BlueP/MoS<sub>2</sub> heterostructure. The corresponding resonance condition and FWHM values are shown in the inset.</p> Full article ">Figure 6
<p>Magnetic field strength (A/m) at BlueP/WS<sub>2</sub>–analyte interface with λ = 811.20 nm, Ag = 38.2 nm, monolayer BlueP/WS<sub>2</sub> thickness of 0.75 nm for (<b>a</b>) N-tissue as an analyte (RI = 1.3502 + 0.005i), and (<b>b</b>) MET as an analyte (RI = 1.3703 + 0.0032i).</p> Full article ">Figure 7
<p>Magnetic field strength (A/m) at the BlueP/MoS<sub>2</sub>–analyte interface with λ = 813.40 nm, Ag = 38.20 nm, monolayer BlueP/MoS<sub>2</sub> thickness of 0.75 nm for (<b>a</b>) N-tissue as an analyte (RI = 1.3501 + 0.005i), and (<b>b</b>) MET as an analyte (RI = 1.3703 + 0.0032i).</p> Full article ">
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