Materials

12 pages, 1531 KiB

Open AccessArticle

Blistering Behavior of Beryllium and Beryllium Alloy under High-Dose Helium Ion Irradiation

by Ping-Ping Liu, Qi-Cong Wang, Yu-Mei Jia, Wen-Tuo Han, Xiao-Ou Yi, Qian Zhan and Fa-Rong Wan

Materials 2024, 17(16), 3997; https://doi.org/10.3390/ma17163997 (registering DOI) - 11 Aug 2024

Abstract

Beryllium (Be) has been selected as the solid neutron multiplier material for a tritium breeding blanket module in ITER, which is also the primary option of the Chinese TBM program. But the irradiation swelling of beryllium is severe under high temperature, high irradiation [...] Read more.

Beryllium (Be) has been selected as the solid neutron multiplier material for a tritium breeding blanket module in ITER, which is also the primary option of the Chinese TBM program. But the irradiation swelling of beryllium is severe under high temperature, high irradiation damage and high doses of transmutation-induced helium. Advanced neutron multipliers with high stability at high temperature are desired for the demonstration power plant (DEMO) reactors and the China Fusion Engineering Test Reactor (CFETR). Beryllium alloys mainly composed of Be₁₂M (M is W or Ti) phase were fabricated by HIP, which has a high melting point and high beryllium content. Beryllium and beryllide (Be₁₂Ti and Be₁₂W) samples were irradiated by helium ion with 30 keV and 1 × 10¹⁸cm⁻² at RT. The microstructures of Be, Be₁₂Ti and Be₁₂W samples were analyzed by SEM and TEM before and after ion irradiation. The average size of the first blistering on the surface of Be-W alloy is about 0.8 μm, and that of secondary blistering is about 79 nm. The surface blistering rates of the beryllium and beryllide samples were also compared. These results may provide a preliminary experimental basis for evaluating the irradiation swelling resistance of beryllium alloy. Full article

(This article belongs to the Special Issue Advanced Light Metal and Alloys: Preparation, Characterization, and Applications (2nd Edition))

41 pages, 19874 KiB

Open AccessReview

Green Corrosion Inhibitors for Metal and Alloys Protection in Contact with Aqueous Saline

by Felipe M. Galleguillos Madrid, Alvaro Soliz, Luis Cáceres, Markus Bergendahl, Susana Leiva-Guajardo, Carlos Portillo, Douglas Olivares, Norman Toro, Victor Jimenez-Arevalo and Maritza Páez

Materials 2024, 17(16), 3996; https://doi.org/10.3390/ma17163996 (registering DOI) - 11 Aug 2024

Abstract

Corrosion is an inevitable and persistent issue that affects various metallic infrastructures, leading to significant economic losses and safety concerns, particularly in areas near or in contact with saline solutions such as seawater. Green corrosion inhibitors are compounds derived from natural sources that [...] Read more.

Corrosion is an inevitable and persistent issue that affects various metallic infrastructures, leading to significant economic losses and safety concerns, particularly in areas near or in contact with saline solutions such as seawater. Green corrosion inhibitors are compounds derived from natural sources that are biodegradable in various environments, offering a promising alternative to their conventional counterparts. Despite their potential, green corrosion inhibitors still face several limitations and challenges when exposed to NaCl environments. This comprehensive review delves into these limitations and associated challenges, shedding light on the progress made in addressing these issues and potential future developments as tools in corrosion management. Explicitly the following aspects are covered: (1) attributes of corrosion inhibitors, (2) general corrosion mechanism, (3) mechanism of corrosion inhibition in NaCl, (4) typical electrochemical and surface characterization techniques, (5) theoretical simulations by Density Functional Theory, and (6) corrosion testing standards and general guidelines for corrosion inhibitor selection. This review is expected to advance the knowledge of green corrosion inhibitors and promote further research and applications. Full article

(This article belongs to the Topic Corrosion and Protection of Metallic Materials, 2nd Edition)

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24 pages, 2214 KiB

Open AccessArticle

A Multiscale Inelastic Internal State Variable Corrosion Model

by M. F. Horstemeyer, W. Song, H. E. Cho, D. Wipf, H. J. Martin, D. K. Francis and S. Chaudhuri

Materials 2024, 17(16), 3995; https://doi.org/10.3390/ma17163995 (registering DOI) - 11 Aug 2024

Abstract

We present a corrosion internal state variable (ISV) damage model based upon the integrated computational materials engineering (ICME) hierarchical multiscale paradigm. Structure–property experiments for magnesium alloys were used where the only inputs were the volume fractions of each element of the periodic table. [...] Read more.

We present a corrosion internal state variable (ISV) damage model based upon the integrated computational materials engineering (ICME) hierarchical multiscale paradigm. Structure–property experiments for magnesium alloys were used where the only inputs were the volume fractions of each element of the periodic table. This macroscale ISV corrosion model finds its basis in Horstemeyer’s mechanical damage model, which includes three separate ISVs for damage nucleation, growth, and coalescence, as well as Walton’s inclusion of corrosion, which introduces five new ISVs for pit nucleation, growth, and coalescence, along with general corrosion and intergranular corrosion. While Walton’s corrosion ISVs are phenomenological in nature, herein we develop a multiscale physical basis for the corrosion ISVs. The parameters for the macroscale corrosion ISVs were garnered from the mesoscale Butler–Volmer equations. Pure magnesium with differing amounts of aluminum were used in corrosion tests to exemplify the different pitting, general corrosion, and intergranular corrosion rates, and the macroscale ISV model was calibrated with said data, in which the only inputs to the model are the volume percentages of the elements magnesium and aluminum. Although magnesium alloys were used to motivate and calibrate the model, the model is abstract enough to possibly capture other material systems as well. Full article

(This article belongs to the Special Issue Multiscale Characterization and Computational Modeling/Simulation of Metallic Materials)

19 pages, 11810 KiB

Open AccessArticle

Nonlinearity of the Upconversion Response of Er³⁺ in Y₂TiO₅:Er³⁺,Yb³⁺ Ceramics When Varying the Wavelength of Incident NIR Excitation Radiation

by Liviu Dudaș, Daniela Berger and Cristian Matei

Materials 2024, 17(16), 3994; https://doi.org/10.3390/ma17163994 (registering DOI) - 11 Aug 2024

Abstract

The upconversion response of Er³⁺ sensitized by Yb³⁺ in various crystalline hosts and illuminated with a laser light at around 980 nm revealed certain spectral shapes that are typical for each of the crystalline matrices containing the dopants. The purpose of [...] Read more.

The upconversion response of Er³⁺ sensitized by Yb³⁺ in various crystalline hosts and illuminated with a laser light at around 980 nm revealed certain spectral shapes that are typical for each of the crystalline matrices containing the dopants. The purpose of this work was to measure the upconversion response of Er³⁺ as a dopant in Y₂TiO₅, sensitized by Yb³⁺, at different concentrations relative to the substituted Y³⁺ ion, and to reveal the subtleties of the mechanisms of the energy transfers between them and the lattice. Therefore, we synthesized Y₂TiO₅ ceramic samples doped with different concentrations of Er³⁺ and Yb³⁺, below 10% (mol), in order to minimize the distortion of the lattice. The oxide powders, obtained using the sol–gel method, as well as the ceramics were structurally and morphologically characterized using an X-ray diffraction analysis and scanning electron microscopy. When the ceramic samples were irradiated with an NIR laser light, it was found that, at a wavelength variation of only 2 nm of the incident radiation, from 973.5 nm to 975.5 nm, the upconversion spectra differed significantly. This nonlinearity is notable because it is not present in the case of other crystalline host matrices studied by us since the literature lacks information on this subject. We also correlated this effect with the simulated distribution of the average distances between Er³⁺ and Yb³⁺ ions in the host matrix. Full article

(This article belongs to the Section Optical and Photonic Materials)

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22 pages, 3912 KiB

Open AccessReview

Survey of Applicable Methods for Determining Viscoelastic Effects in Ferroelectric and Antiferroelectric Chiral Liquid Crystals

by Dorota Dardas

Materials 2024, 17(16), 3993; https://doi.org/10.3390/ma17163993 (registering DOI) - 11 Aug 2024

Abstract

Viscosity, elasticity, and viscoelastic properties are one of the most fundamental properties of liquid crystalline materials; the main problem in determining these properties is the multitude of physical parameters needed to determine the values of elasticity and viscosity constants. In this paper, a [...] Read more.

Viscosity, elasticity, and viscoelastic properties are one of the most fundamental properties of liquid crystalline materials; the main problem in determining these properties is the multitude of physical parameters needed to determine the values of elasticity and viscosity constants. In this paper, a number of different measurement methods for the complete characterization of viscoelastic properties for smectic liquid crystalline materials and their mixtures are analyzed, both theoretically and experimentally. The way in which viscoelastic material constants are determined depends mainly on the application/purpose of the materials under study. The subject of this work was to review the methods used to determine viscoelastic effects in ferroelectric and antiferroelectric chiral liquid crystals, their mixtures, composite materials, and even in dielectric systems, which would bear the hallmark of a universal method allowing the application of sufficiently low electric fields. In the case of chiral liquid crystals with ferroelectric and antiferroelectric phases and their subphases, the following assumption applies: fulfilment of Hooke’s law (in the case of elastic coefficients) and preservation of laminar flow (in the case of viscosity coefficients). Full article

(This article belongs to the Special Issue Liquid Crystals and Other Partially Disordered Molecular Systems)

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Temperature dependence of the rotational viscosity coefficient γ in a ferroelectric liquid crystal C8. Full article ">Figure 2
Temperature dependence of the elastic coefficient <math display="inline"><semantics> <mrow> <msub> <mrow> <mi>K</mi> </mrow> <mrow> <mi>φ</mi> </mrow> </msub> <mtext> </mtext> </mrow> </semantics></math> in a ferroelectric liquid crystal C8. Full article ">Figure 3
Temperature dependence of the elastic coefficient <math display="inline"><semantics> <mrow> <msub> <mrow> <mi>K</mi> </mrow> <mrow> <mi>φ</mi> </mrow> </msub> </mrow> </semantics></math> in ferroelectric liquid crystal C8 obtained by various methods. In the diagram, ”eo” denotes electro-optical methods and “diel” dielectric methods. Thicknesses of planar samples, 5 µm and 50 µm; thickness of homeotropic sample, 30 µm. Full article ">Figure 4
Temperature dependence of the rotational viscosity coefficient γ in ferroelectric liquid crystal C8 obtained by various methods. In the diagram, “eo” denotes electro-optic methods, “diel” dielectric, and “switch” switching methods. Thicknesses of the planar samples, 2.9 µm, 5 µm, and 50 µm; thickness of the homeotropic sample, 30 µm. Full article ">Figure 5
Temperature dependence of the elastic coefficient <math display="inline"><semantics> <mrow> <msub> <mrow> <mi>K</mi> </mrow> <mrow> <mi>φ</mi> </mrow> </msub> </mrow> </semantics></math> in chiral liquid crystals with a ferroelectric phase: C8 (rhombs), Ce3 (diamonds), Ce8 (hexagons), and MHPOBC (triangles) obtained by electro-optical method using low electric fields. Full article ">Figure 6
Temperature dependence of the elastic coefficient <math display="inline"><semantics> <mrow> <msub> <mrow> <mi>K</mi> </mrow> <mrow> <mi>a</mi> </mrow> </msub> </mrow> </semantics></math> in chiral liquid crystals with antiferroelectric phase: D12 (rhomboids) and MHPOBC (triangles) obtained by electro-optical method using low electric fields. Full article ">Figure 7
Elasticity constant <math display="inline"><semantics> <mrow> <msub> <mrow> <mi>K</mi> </mrow> <mrow> <mi>φ</mi> </mrow> </msub> </mrow> </semantics></math> as a function of temperature for three different materials in the low electric field range: D12, MHPOBC, and Ce 3 showing the different dependence of the elastic constant depending on the type of adjacent phases. To illustrate the difference in helix behavior, schematic drawings are shown for one pitch period for the compounds studied. Green indicates the antiferroelectric phase CA*, red the ferroelectric phase C*. Full article ">

20 pages, 7151 KiB

Open AccessArticle

Copper Ion Removal by Adsorption Using Fly Ash-Based Geopolymers: Process Optimization Insights from Taguchi and ANOVA Statistical Methods

by Loredana Litu, Gabriela Buema, Giannin Mosoarca and Maria Harja

Materials 2024, 17(16), 3992; https://doi.org/10.3390/ma17163992 (registering DOI) - 11 Aug 2024

Abstract

The present study aimed to use geopolymer materials synthesized from different fly ashes, which are promising for the adsorption of copper ions from aqueous solutions. The characterization of fly ashes and prepared adsorbents was performed by energy-dispersive X-ray spectroscopy (EDS) analysis, Brunauer–Emmett–Teller (BET) [...] Read more.

The present study aimed to use geopolymer materials synthesized from different fly ashes, which are promising for the adsorption of copper ions from aqueous solutions. The characterization of fly ashes and prepared adsorbents was performed by energy-dispersive X-ray spectroscopy (EDS) analysis, Brunauer–Emmett–Teller (BET) surface area analysis, and Scanning Electron Microscopy (SEM). Taguchi and ANOVA methods were used to predict the effect of different working parameters on copper ion removal by prepared geopolymers. Based on data obtained by the Taguchi method, it was found that the factor most influencing the adsorption process is the type of adsorbent used, followed by the solution pH, the reaction time, the adsorbent dose, and the initial copper ion concentration. The ANOVA results agree with the Taguchi method. The optimal conditions of the adsorption process were: fly ash C modified by direct activation with 2 M NaOH, at 70 °C for 4 h, solution pH of 5, initial pollutant concentration of 300 mg/L, 40 g/L adsorbent dose, and 120 min of reaction time. Copper ion removal efficiency was determined experimentally under optimal conditions, achieving a value of 99.71%. Full article

(This article belongs to the Special Issue Environmentally Friendly Adsorption Materials)

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22 pages, 2054 KiB

Open AccessArticle

Formability Prediction Using Machine Learning Combined with Process Design for High-Drawing-Ratio Aluminum Alloy Cups

by Yeong-Maw Hwang, Tsung-Han Ho, Yung-Fa Huang and Ching-Mu Chen

Materials 2024, 17(16), 3991; https://doi.org/10.3390/ma17163991 (registering DOI) - 11 Aug 2024

Abstract

Deep drawing has been practiced in various manufacturing industries for many years. With the aid of stamping equipment, materials are sheared to different shapes and dimensions for users. Meanwhile, through artificial intelligence (AI) training, machines can make decisions or perform various functions. The [...] Read more.

Deep drawing has been practiced in various manufacturing industries for many years. With the aid of stamping equipment, materials are sheared to different shapes and dimensions for users. Meanwhile, through artificial intelligence (AI) training, machines can make decisions or perform various functions. The aim of this study is to discuss the geometric and process parameters for A7075 in deep drawing and derive the formable regions of sound products for different forming parameters. Four parameters—forming temperature, punch speed, blank diameter and thickness—are used to investigate their effects on the forming results. Through finite element simulation, a database is established and used for machine learning (ML) training and validation to derive an AI prediction model. Importing the forming parameters into this prediction model can obtain the forming results rapidly. To validate the formable regions of sound products, several experiments are conducted and the results are compared with the prediction results to verify the feasibility of applying ML to deep drawing processes of aluminum alloy A7075 and the reliability of the AI prediction model. Full article

(This article belongs to the Special Issue Characterization of Metallic Materials: Microstructure, Forming and Heat Treatment (Second Edition))

19 pages, 2909 KiB

Open AccessReview

Use of Innovative Methods to Produce Highly Insulating Walls Using 3D-Printing Technology

by Michał Góra, Magdalena Bańkosz and Bożena Tyliszczak

Materials 2024, 17(16), 3990; https://doi.org/10.3390/ma17163990 (registering DOI) - 11 Aug 2024

Abstract

The article explores innovative methods for creating high-insulation walls, essential for the future of energy-efficient and sustainable construction. It focuses on advanced 3D-printing technologies that allow for the construction of walls with superior insulation materials, optimizing thermal properties and significantly reducing energy for [...] Read more.

The article explores innovative methods for creating high-insulation walls, essential for the future of energy-efficient and sustainable construction. It focuses on advanced 3D-printing technologies that allow for the construction of walls with superior insulation materials, optimizing thermal properties and significantly reducing energy for heating and cooling. The integration of thermal insulation within wall structures and innovations in building materials like lightweight composites, aerogels, and nanotechnology-based insulations are highlighted. It discusses the environmental, economic, and technical benefits of these innovations and the challenges to fully leverage 3D printing in construction. Future development directions emphasize materials that enhance thermal efficiency, sustainability, and functionality, promising a new era of sustainable and innovative construction practices. Full article

(This article belongs to the Special Issue Properties, Structures and Practical Applications of Eco-Friendly Cementitious Materials (Eco-CM))

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13 pages, 7175 KiB

Open AccessArticle

Effect of Cyclic Warm-Rolling Technique on Mechanical Properties of MoCu30 Thin Plates with Heterogeneous Structure

by Xianlei Hu, Huan Hu, Ruimin Lai, Qincheng Xie and Ying Zhi

Materials 2024, 17(16), 3989; https://doi.org/10.3390/ma17163989 (registering DOI) - 11 Aug 2024

Abstract

By employing a cyclic warm rolling technique, MoCu30 alloy sheets of different thicknesses were prepared to investigate the effects of various rolling reduction rates on the microstructure and mechanical properties of MoCu30 alloys. Additionally, the evolution of microscale heterogeneous deformation during the tensile [...] Read more.

By employing a cyclic warm rolling technique, MoCu30 alloy sheets of different thicknesses were prepared to investigate the effects of various rolling reduction rates on the microstructure and mechanical properties of MoCu30 alloys. Additionally, the evolution of microscale heterogeneous deformation during the tensile process was observed based on DIC technology. This study reveals that Mo–Cu interfaces at different deformation rates exhibit an amorphous interlayer of 0.5–1.0 μm thickness, which contributes to enhancing the bond strength of Mo–Cu interfaces. As the rolling reduction rate increased, the grain size of the MoCu30 alloy gradually decreased, whereas the dislocation density and hardness increased. Furthermore, the yield strength and tensile strength of the MoCu30 alloy increased gradually, whereas the elongation decreased. At a deformation rate of 74% (2 mm), the yield strength, tensile strength, and elongation of the MoCu30 alloy were 647.9 MPa, 781.8 MPa, and 11.7%, respectively. During the tensile process of Mo–Cu dual-phase heterogeneous material, a unique hierarchical strain banding was formed, which helps to suppress strain localization and prevent premature plastic instability. Full article

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15 pages, 7353 KiB

Open AccessArticle

Light-Cured Junction Formation and Broad-Band Imaging Application in Thermally Mismatched van der Waals Heterointerface

by Liyuan Cheng, Qinglin Quan and Liang Hu

Materials 2024, 17(16), 3988; https://doi.org/10.3390/ma17163988 (registering DOI) - 11 Aug 2024

Abstract

Van der Waals (vdW) heterostructures are mainly fabricated by a classic dry transfer procedure, but the interface quality is often subject to the vdW gap, residual strains, and defect species. The realization of interface fusion and repair holds significant implications for the modulation [...] Read more.

Van der Waals (vdW) heterostructures are mainly fabricated by a classic dry transfer procedure, but the interface quality is often subject to the vdW gap, residual strains, and defect species. The realization of interface fusion and repair holds significant implications for the modulation of multiple photoelectric conversion processes. In this work, we propose a thermally mismatched strategy to trigger broad-band and high-speed photodetection performance based on a type-I heterostructure composed of black phosphorus (BP) and FePS₃ (FPS) nanoflakes. The BP acts as photothermal source to promote interface fusion when large optical power is adopted. The regulation of optical power enables the device from pyroelectric (PE) and/or alternating current photovoltaic (AC–PV) mode to a mixed photovoltaic (PV)/photothermoelectric (PTE)/PE mode. The fused heterostructure device presents an extended detection range (405~980 nm) for the FPS. The maximum responsivity and detectivity are 329.86 mA/W and 6.95 × 10¹⁰ Jones, respectively, and the corresponding external quantum efficiency (EQE) approaches ~100%. Thanks to these thermally-related photoelectric conversion mechanism, the response and decay time constants of device are as fast as 290 μs and 265 μs, respectively, superior to current all FPS-based photodetectors. The robust environmental durability also renders itself as a high-speed and broad-band imaging sensor. Full article

(This article belongs to the Topic Optical and Optoelectronic Properties of Materials and Their Applications)

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(a) Schematic diagram of light-induced interface fusion for BP−–FPS heterostructure. (b,c) Representative light sensitive I–V and I–t curves before and after interface fusion. (d) Optical microscopic image from BP/FPS/Gr vdW heterostructure device. The corresponding height profiles of BP and FPS nanoflakes are shown around. The purple, red, and blue dotted lines denote the BP, FPS, and Gr regions, respectively. (e) Raman peak mapping of BP and FPS components from the B2g mode in BP and the P5 mode in FPS, respectively. (f) Raman spectral comparison for different regions. Full article ">Figure 2
(a,b) I–V characteristic curves in linear (a) and logarithm (b) scales under dark and illumination states with different incident light wavelengths of 405, 520, and 980 nm. Inset in (a) is the 3D model illustration of the BP−–FPS−–Gr device. (c) Temporal photocurrent excited by different light sources. (d) Enlarged view for photocurrent versus time (I–t) curve under illumination of 980 nm. A +2 V bias voltage is applied to the device. Full article ">Figure 3
(a) Optical microscopic image of selected Raman mapping region. (b–d) Raman intensity mapping images from BP modes. (e–h) Raman intensity mapping images from FPS modes. The white and black dotted lines represent the BP and FPS regions, respectively. Full article ">Figure 4
(a,b) I–V characteristic curves in linear (a) and logarithm (b) scales under dark and illumination with incident light wavelengths of 405, 520, and 980 nm. (c,d) Cycled photoresponse measurements (c) and temporal photocurrent (d) illuminated by different light sources. The device is driven under −2 V bias voltage. Full article ">Figure 5
(a–e) AFM height image (a) and corresponding KPFM images collected under dark condition (b) and different illumination wavelengths of 405 nm (c), 520 nm (d), and 980 nm (e). The contact potential differences between BP and FPS region are shown in images. The white and grey dotted lines are the regions of BP and FPS, respectively. (f,g) Band alignments before and after BP−–FPS contact. Full article ">Figure 6
(a,c,e) Scanning photocurrent mapping of vdW heterostructure device working at −0.2 V under illumination of 405 nm (a), 520 nm (c), and 980 nm (e). The green and black dotted lines are the regions of BP and FPS, respectively. (b,d,f) Corresponding energy band bending diagrams, spectral absorption, and possible photodetection mechanisms. Full article ">Figure 7
(a) Durability tests of device under different illumination conditions. (b) Single-pixel photodetection apparatus. (c) Broad-band imaging photos using customized “HDU” mask. Full article ">

16 pages, 3652 KiB

Open AccessArticle

An Enhanced Numerical Calculation Method to Study the Anchorage Performance of Rebars

by Jianhang Chen, Junming Ma, Xiaofan Zeng, Banquan Zeng, Krzysztof Skrzypkowski, Krzysztof Zagórski, Anna Zagórska and Saisai Wu

Materials 2024, 17(16), 3987; https://doi.org/10.3390/ma17163987 (registering DOI) - 11 Aug 2024

Abstract

When modelling the anchorage performance of rebars with the tri-linear law, the calculation process of the load–deformation relation is complicated. The reason is that when the rebar–grout interface entered the elastic–softening–debonding stage, the softening section length and debonding section length vary simultaneously. To [...] Read more.

When modelling the anchorage performance of rebars with the tri-linear law, the calculation process of the load–deformation relation is complicated. The reason is that when the rebar–grout interface entered the elastic–softening–debonding stage, the softening section length and debonding section length vary simultaneously. To solve this issue, this paper proposes an enhanced numerical calculation method. When the rebar–grout interface entered the elastic–softening–debonding stage, the softening section length was fixed to a specific value. One loop function was created to calculate the debonding section length. With this method, the number of iteration calculations significantly decreased. The credibility of this calculation method was confirmed with experimental results. Two case studies were conducted to compare the load–deformation relation obtained with the original calculation method and enhanced calculation method. The results showed that good consistency existed between the results obtained by those two methods. This finding can significantly improve the calculation efficiency when studying the anchorage performance of rebars. Moreover, this paper provides new insight for users to optimise the modelling process of rebars. Full article

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12 pages, 4913 KiB

Open AccessArticle

Salt Crystallization in Limestone: Materials Decay and Chemomechanical Approach

by Marta Cappai, Marta Casti and Giorgio Pia

Materials 2024, 17(16), 3986; https://doi.org/10.3390/ma17163986 (registering DOI) - 11 Aug 2024

Abstract

Salt crystallization is a particularly relevant issue in the conservation of limestones used in Cultural Heritage sites. In this study, various facies of limestones were characterized through porosimetric and mechanical tests. The samples were subjected to experiments to determine their resistance to salt [...] Read more.

Salt crystallization is a particularly relevant issue in the conservation of limestones used in Cultural Heritage sites. In this study, various facies of limestones were characterized through porosimetric and mechanical tests. The samples were subjected to experiments to determine their resistance to salt crystallization by verifying the number of cycles at which 50% of them began to lose weight. This number of experimental cycles was compared with the result calculated by the analytical procedure of a chemomechanical model found in the literature. The comparison showed a significant capability of the model to predict the experimental data. Full article

(This article belongs to the Special Issue Stone Building Materials: Characterization, Decay, and Conservation (Second Volume))

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X-ray diffraction pattern of Miocene limestone. Full article ">Figure 2
Pore cumulative curves for different series of Miocene limestones studied (— C1; — C2; — C3; — C4; — C5; — C6). In particular, considering three different pore radius ranges in relation to the hazard level of salt crystallization (with the highest risk identified in the range between 1 and 0.05 μm [<a href="#B1-materials-17-03986" class="html-bibr">1</a>,<a href="#B3-materials-17-03986" class="html-bibr">3</a>,<a href="#B44-materials-17-03986" class="html-bibr">44</a>]), it can be observed that approximately 50% of the porosity is distributed within the high-risk vulnerability range. Indeed, such pore size distributions lead to high crystallization pressures that can cause significant damage to the material’s microstructure [<a href="#B22-materials-17-03986" class="html-bibr">22</a>]. Consequently, the average pore radius (APR) of the distribution falls within the critical range, with values between 0.322 μm and 0.185 μm. Full article ">Figure 3
Scheme of experimental procedure for the determination of resistance to salt crystallization. The starting point of each cycle coincides with the preparation of the solution. Full article ">Figure 4
Mass variation of studied limestones during salt crystallization test. Filled points correspond to the cycles in which 50% of samples have lost mass. Full article ">Figure 5
(a) σ* at different temperatures (○ = 2.5 °C; ◊ = 7.5 °C; Δ = 12.5 °C; × = 20 °C; □ = 25 °C; + = 30 °C) with a concentration of 6.1% sodium sulfate in water; (b) σ* at different concentrations (○ = 6.1%; ◊ = 5%; Δ = 4%; × = 3%; □ = 2%) at a temperature of 25 °C. The gray band indicates the critical stress range between 2.17 and 3.65 MPa. Full article ">Figure 6
Model calculations for predicting macroscopic tensile strength and comparison with critical macroscopic tensile strength. Filled points represent the value for which 50% of samples have lost mass. Calculations have been performed for T = 25 °C, at a concentration of 0.0645 ± 0.0001 g·mL−1. Full article ">

13 pages, 2403 KiB

Open AccessArticle

Treatment of Localized Gingival Recession with an Enamel Matrix Protein-Coated Xenogeneic Dermal Matrix: A Randomized Controlled Trial

by Marcus Rieder, Gernot Wimmer, Alwin Sokolowski, Armin Sokolowski, Michael Payer and Behrouz Arefnia

Materials 2024, 17(16), 3985; https://doi.org/10.3390/ma17163985 (registering DOI) - 10 Aug 2024

Abstract

This study aims to evaluate the influence of the additional use of enamel matrix derivate (EMD) in the treatment of gingival recession defects using a coronally advanced flap (CAF) and a xenogeneic dermal matrix (XDM) by means of digital and clinical assessment methods. [...] Read more.

This study aims to evaluate the influence of the additional use of enamel matrix derivate (EMD) in the treatment of gingival recession defects using a coronally advanced flap (CAF) and a xenogeneic dermal matrix (XDM) by means of digital and clinical assessment methods. In this prospective randomized controlled study, recession height and area, width and thickness of keratinized gingiva, pocket probing depth, and clinical attachment levels were measured at the baseline and followed up for one year. Fifteen patients (n = 15) with 24 gingival recession defects were treated between 2019 and 2021. On average, the digitally assessed root coverage of the control group (CAF + XDM) was not significantly different compared to the test group (CAF + XDM + EMD), with 69 ± 28% and 36 ± 32%, respectively (p = 0.094). One year postoperatively, there were no differences found regarding keratinized tissue width (KTW) between the control group and test group (p = 0.690). However, the control group showed superior results in the thickness of keratinized gingiva (p = 0.044). The present study showed that there were no statistically significant differences in the root coverage results in the CAF + XDM + EMD group compared to the CAF + XDM group. The adjunctive use of EMD to a CAF and XDM in the treatment of gingival recession defects does not appear to have any clinical benefit. Full article

(This article belongs to the Special Issue Biomaterials in Periodontology and Implant Dentistry)

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20 pages, 7272 KiB

Open AccessArticle

Preparation of Supercapacitor Carbon Electrode Materials by Low-Temperature Carbonization of High-Nitrogen-Doped Raw Materials from Food Waste

by Qingnan Mu, Chang Liu, Yao Guo, Kun Wang, Zhijie Gao, Yuhan Du, Changqing Cao, Peigao Duan and Krzysztof Kapusta

Materials 2024, 17(16), 3984; https://doi.org/10.3390/ma17163984 (registering DOI) - 10 Aug 2024

Abstract

To address the problem of the low nitrogen (N) content of carbon materials prepared through the direct carbonization of food waste, soybean meal and egg whites with high N contents were selected to carry out carbonization experiments on food waste. At 220 °C, [...] Read more.

To address the problem of the low nitrogen (N) content of carbon materials prepared through the direct carbonization of food waste, soybean meal and egg whites with high N contents were selected to carry out carbonization experiments on food waste. At 220 °C, the effects of hydrothermal carbonization and microwave carbonization on the properties of supercapacitor electrode materials were investigated. The results show that food waste doped with soybean meal and egg whites could achieve good N doping. At a current density of 1 A·g⁻¹, the specific capacitance of the doped carbon prepared by hydrothermal doping is as high as 220.00 F·g⁻¹, which is much greater than that of the raw material prepared through the hydrothermal carbonization of food waste alone, indicating that the hydrothermal carbonization reactions of soybean meal, egg white, and food waste promote the electrochemical properties of the prepared carbon materials well. However, when a variety of raw materials are mixed for pyrolysis carbonization, different raw materials cannot be fully mixed in the pyrolysis process, and under the etching action of potassium hydroxide, severe local etching and local nonetching occur, resulting in a severe increase in the pore size distribution and deterioration of the electrochemical performance of the prepared carbon materials. At a current density of 1 A·g⁻¹, the specific capacitance of these prepared carbon materials is 157.70 F·g⁻¹, whereas it is only 62.00 F·g⁻¹ at a high current density of 20 A·g⁻¹. Therefore, this study suggests that the hydrothermal carbonization process is superior to the microwave pyrolysis carbonization process for preparing supercapacitor electrode materials with multiple samples doped with each other. Full article

(This article belongs to the Special Issue Recycling and Resource Utilization of Waste)

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24 pages, 33071 KiB

Open AccessArticle

Structure and Mechanical Properties of AlMgSi(Cu) Extrudates Straightened with Dynamic Deformation

by Dariusz Leśniak, Józef Zasadziński, Wojciech Libura, Beata Leszczyńska-Madej, Marek Bogusz, Tomasz Latos and Bartłomiej Płonka

Materials 2024, 17(16), 3983; https://doi.org/10.3390/ma17163983 (registering DOI) - 10 Aug 2024

Abstract

Before artificial ageing, extruded aluminium profiles are subjected to stretching with a small cold deformation in the range of 0.5–2%. This deformation improves the geometrical stability of the extruded product and causes changes in the microstructure of the profile, which leads to the [...] Read more.

Before artificial ageing, extruded aluminium profiles are subjected to stretching with a small cold deformation in the range of 0.5–2%. This deformation improves the geometrical stability of the extruded product and causes changes in the microstructure of the profile, which leads to the strain hardening of the material after artificial ageing. The work has resulted in the creation of the prototype of an original device, which is unique in the world, for the dynamic stretching of the extruded profiles after quenching. The semi-industrial unit is equipped with a hydraulic system for stretching and a pneumatic system for cold dynamic deformation. The aim of this research paper is to produce advantageous microstructural changes and increase the strength properties of the extruded material. The solution of the dynamic stretching of the profiles after extrusion is a great challenge and an innovation not yet practised. The paper presents the results of microstructural and mechanical investigations carried out on extruded AlMgSi(Cu) alloys quenched on the run-out table of the press, dynamically stretched under different conditions, and artificially aged for T5 temper. Different stretching conditions were applied: a static deformation of 0.5% at a speed of 0.02 m/s, and dynamic deformation of 0.25%, 0.5%, 1%, and 1.5% at speeds of 0.05 and 2 m/s. After the thermomechanical treatment of the profiles, microstructural observations were carried out using an optical microscope (OM) and a scanning electron microscope (SEM). A tensile test was also carried out on the specimens stretched under different conditions. In all the cases, the dynamically stretched profiles showed higher strength properties, especially those deformed at a higher speed of 2 m/s, where the increase in UTS was observed in the range of 7–18% compared to the classical (static) stretching. The microstructure of the dynamically stretched profiles is more homogeneous with a high proportion of fine dispersoids. Full article

(This article belongs to the Special Issue Metalworking Processes: Theoretical and Experimental Study)

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15 pages, 90496 KiB

Open AccessArticle

Improving Mechanical Performance of Self-Binding Fiberboards from Untreated Perennial Low-Input Crops by Variation of Particle Size

by Lüders Moll, Alexander Klein, Sören Jannis Heidemann, Georg Völkering, Jessica Rumpf and Ralf Pude

Materials 2024, 17(16), 3982; https://doi.org/10.3390/ma17163982 (registering DOI) - 10 Aug 2024

Abstract

Studies on self-binding hot-pressed fiberboards using agricultural byproducts aim to identify alternatives to scarce wood resources. Particle size and mixture significantly impact strength, although direct comparisons are difficult due to differences in study methods. We evaluated fiberboards made from the two perennial biomass [...] Read more.

Studies on self-binding hot-pressed fiberboards using agricultural byproducts aim to identify alternatives to scarce wood resources. Particle size and mixture significantly impact strength, although direct comparisons are difficult due to differences in study methods. We evaluated fiberboards made from the two perennial biomass crops Miscanthus and Paulownia and compared them to Picea (spruce), using five distinct particle size blends prepared from milled and sieved particles, respectively. The boards were evaluated for their modulus of elasticity, modulus of rupture, reaction to fire, water absorption, and thickness swelling. All specimens exhibited normal ignitability, as defined by Euroclass E according to EN13501-1. The results indicate that mechanical performance improves with increasing density, which correlates with higher proportions of finer particles. Notably, the finer Miscanthus blends and all Paulownia samples met the modulus of elasticity requirements of EN 622. Full article

(This article belongs to the Special Issue Recent Developments in Bio-Based Particleboards and Fiberboards)

15 pages, 4356 KiB

Open AccessArticle

Intensity Analysis Method of Acoustic Emission Signals for the Damage Monitoring of Post-Tensioned Concrete Beams

by Ezio Bruno, Giuseppe Scionti, Luigi Calabrese and Edoardo Proverbio

Materials 2024, 17(16), 3981; https://doi.org/10.3390/ma17163981 (registering DOI) - 10 Aug 2024

Abstract

Acoustic emission (AE) is well suited for the real-time monitoring and detection of damage in reinforced concrete structures. In this study, loading/unloading cycles up to failure were applied on three different full-scale beams, each with varying defect morphologies. An intensity analysis method was [...] Read more.

Acoustic emission (AE) is well suited for the real-time monitoring and detection of damage in reinforced concrete structures. In this study, loading/unloading cycles up to failure were applied on three different full-scale beams, each with varying defect morphologies. An intensity analysis method was employed to assess the damage sensitivities of the defective structures under stress conditions. Specifically, the calm ratio, load ratio, severity, and historical index were identified as statistical parameters that can provide global information on the damage level. Consequently, they can be easily used as damage evolution indexes for reinforced concrete structures. Correlations between these parameters were investigated to better discriminate between their potentials and identify critical levels that might not be evident using parametric analysis. The AEI chart helps locate damaging areas, aiding focused repairs. For defected beams with broken strands, at low load, HI and SI fall in zone B (damage detected). At cycles 4 and 6, with significant deflection, they fall into a critical zone, E (severe damage). Comparing post-tensioned beams revealed defects correlating with damage susceptibility. B3 beams with diffused defects displayed high activity at higher loads. Applying a load–calm ratio chart, initial minor damage worsened progressively. Severe damage was prominent in defective B2 and B3 beams, reaching zone 3. The variation in the acquired parameters over time can then be considered as an affordable and reliable indicator of damage progression. Full article

(This article belongs to the Special Issue Modelling, Assessing and Controlling Deterioration Process of Reinforced Concrete Structures)

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38 pages, 5633 KiB

Open AccessReview

Fundamental Aspects of Stretchable Mechanochromic Materials: Fabrication and Characterization

by Christina Tang

Materials 2024, 17(16), 3980; https://doi.org/10.3390/ma17163980 (registering DOI) - 10 Aug 2024

Abstract

Mechanochromic materials provide optical changes in response to mechanical stress and are of interest in a wide range of potential applications such as strain sensing, structural health monitoring, and encryption. Advanced manufacturing such as 3D printing enables the fabrication of complex patterns and [...] Read more.

Mechanochromic materials provide optical changes in response to mechanical stress and are of interest in a wide range of potential applications such as strain sensing, structural health monitoring, and encryption. Advanced manufacturing such as 3D printing enables the fabrication of complex patterns and geometries. In this work, classes of stretchable mechanochromic materials that provide visual color changes when tension is applied, namely, dyes, polymer dispersed liquid crystals, liquid crystal elastomers, cellulose nanocrystals, photonic nanostructures, hydrogels, and hybrid systems (combinations of other classes) are reviewed. For each class, synthesis and processing, as well as the mechanism of color change are discussed. To enable materials selection across the classes, the mechanochromic sensitivity of the different classes of materials are compared. Photonic systems demonstrate high mechanochromic sensitivity (Δnm/% strain), large dynamic color range, and rapid reversibility. Further, the mechanochromic behavior can be predicted using a simple mechanical model. Photonic systems with a wide range of mechanical properties (elastic modulus) have been achieved. The addition of dyes to photonic systems has broadened the dynamic range, i.e., the strain over which there is an optical change. For applications in which irreversible color change is desired, dye-based systems or liquid crystal elastomer systems can be formulated. While many promising applications have been demonstrated, manufacturing uniform color on a large scale remains a challenge. Standardized characterization methods are needed to translate materials to practical applications. The sustainability of mechanochromic materials is also an important consideration. Full article

(This article belongs to the Section Smart Materials)

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14 pages, 3694 KiB

Open AccessArticle

Crystal Lattice Recovery and Optical Activation of Yb Implanted into β-Ga₂O₃

by Mahwish Sarwar, Renata Ratajczak, Vitalii Yu. Ivanov, Sylwia Gieraltowska, Aleksandra Wierzbicka, Wojciech Wozniak, René Heller, Stefan Eisenwinder and Elżbieta Guziewicz

Materials 2024, 17(16), 3979; https://doi.org/10.3390/ma17163979 (registering DOI) - 10 Aug 2024

Abstract

β-Ga₂O₃ is an ultra-wide bandgap semiconductor (E_g~4.8 eV) of interest for many applications, including optoelectronics. Undoped Ga₂O₃ emits light in the UV range that can be tuned to the visible region of the spectrum by [...] Read more.

β-Ga₂O₃ is an ultra-wide bandgap semiconductor (E_g~4.8 eV) of interest for many applications, including optoelectronics. Undoped Ga₂O₃ emits light in the UV range that can be tuned to the visible region of the spectrum by rare earth dopants. In this work, we investigate the crystal lattice recovery of

(\bar{2} 01)

-oriented β-Ga₂O₃ crystals implanted with Yb ions to the fluence of 1 ×10¹⁴ at/cm². Post-implantation annealing at a range of temperature and different atmospheres was used to investigate the β-Ga₂O₃ crystal structure recovery and optical activation of Yb ions. Ion implantation is a renowned technique used for material doping, but in spite of its many advantages such as the controlled introduction of dopants in concentrations exceeding the solubility limits, it also causes damage to the crystal lattice, which strongly influences the optical response from the material. In this work, post-implantation defects in β-Ga₂O₃:Yb crystals, their transformation, and the recovery of the crystal lattice after thermal treatment have been investigated by channeling Rutherford backscattering spectrometry (RBS/c) supported by McChasy simulations, and the optical response was tested. It has been shown that post-implantation annealing at temperatures of 700–900 °C results in partial crystal lattice recovery, but it is accompanied by the out-diffusion of Yb ions toward the surface if the annealing temperature and time exceed 800 °C and 10 min, respectively. High-temperature implantation at 500–900 °C strongly limits post-implantation damage to the crystal lattice, but it does not cause the intense luminescence of Yb ions. This suggests that the recovery of the crystal lattice is not a sufficient condition for strong rare-earth photoluminescence at room temperature and that oxygen annealing is beneficial for intense infrared luminescence compared to other tested environments. Full article

(This article belongs to the Special Issue Advances in Electronic Films: Preparation, Characterization, and Applications)

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