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Materials, Volume 16, Issue 12 (June-2 2023) – 295 articles

Cover Story (view full-size image): Over the past decade, researchers have made significant progress in studying buried hetero-structures by using Second Harmonic Generation. In particular, they have focused on the interface between SrTiO3 and LaAlO3, two wide-gap perovskite insulators that exhibit the remarkable appearance of a perfectly two-dimensional electron gas formed at their interface. The discovery has triggered enormous scientific interest due to the limitless possible technological applications of such an effect. Optical Second Harmonic Generation has been found to be especially suitable for investigating these structures. We would like to draw the reader’s attention to this experimental tool which has not fully developed its whole spectrum of capabilities yet, mainly because it is not well known outside the community of non-linear optics scientists. View this paper
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15 pages, 12203 KiB  
Article
Effect of Zr2Al4C5 Content on the Mechanical Properties and Oxidation Behavior of ZrB2-SiC-Zr2Al4C5 Ceramics
by Qilong Guo, Liang Hua, Hao Ying, Ronghao Liu, Mei Lin, Leilei Li and Jing Wang
Materials 2023, 16(12), 4495; https://doi.org/10.3390/ma16124495 - 20 Jun 2023
Viewed by 1144
Abstract
ZrB2-SiC-Zr2Al4C5 multi-phase ceramics with uniform structure and high density were successfully prepared through the introduction of in situ synthesized Zr2Al4C5 into ZrB2-SiC ceramic via SPS at 1800 °C. A [...] Read more.
ZrB2-SiC-Zr2Al4C5 multi-phase ceramics with uniform structure and high density were successfully prepared through the introduction of in situ synthesized Zr2Al4C5 into ZrB2-SiC ceramic via SPS at 1800 °C. A systematic analysis and discussion of the experimental results and proposed mechanisms were carried out to demonstrate the composition-dependent sintering properties, mechanical properties and oxidation behavior. The results showed that the in situ synthesized Zr2Al4C5 could be evenly distributed in the ZrB2-SiC ceramic matrix and inhibited the growth of ZrB2 grains, which played a positive role in the sintering densification of the composite ceramics. With increasing Zr2Al4C5 content, the Vickers hardness and Young’s modulus of composite ceramics gradually decreased. The fracture toughness showed a trend that first increased and then decreased, and was increased by about 30% compared with ZrB2-SiC ceramics. The major phases resulting from the oxidation of samples were ZrO2, ZrSiO4, aluminosilicate and SiO2 glass. With increasing Zr2Al4C5 content, the oxidative weight showed a trend that first increased then decreased; the composite ceramic with 30 vol.% Zr2Al4C5 showed the smallest oxidative weight gain. We believe that the presence of Zr2Al4C5 results in the formation of Al2O3 during the oxidation process, subsequently resulting in a lowering of the viscosity of the glassy silica scale, which in turn intensifies the oxidation of the composite ceramics. This would also increase oxygen permeation through the scale, adversely affecting the oxidation resistance of the composites with high Zr2Al4C5 content. Full article
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16 pages, 2141 KiB  
Article
Modified Natural Diatomite with Various Additives and Its Environmental Potential
by Krzysztof Gondek, Piotr Micek, Agnieszka Baran, Tomasz Bajda, Jerzy Kowal, Marcin Lis, Anna Wyrobisz-Papiewska, Dorota Wojtysiak and Krzysztof Smoroń
Materials 2023, 16(12), 4494; https://doi.org/10.3390/ma16124494 - 20 Jun 2023
Cited by 1 | Viewed by 1138
Abstract
Diatomite has recently been the subject of intensive scientific research aimed at its extensive use in industry, breeding and agriculture. The only active diatomite mine is in Jawornik Ruski, in the Podkarpacie region of Poland. Chemical pollution in the environment, including that from [...] Read more.
Diatomite has recently been the subject of intensive scientific research aimed at its extensive use in industry, breeding and agriculture. The only active diatomite mine is in Jawornik Ruski, in the Podkarpacie region of Poland. Chemical pollution in the environment, including that from heavy metals, poses a threat to living organisms. Reducing the mobility of heavy metals in the environment through the use of diatomite (DT) has recently gained much interest. More effective immobilisation of heavy metals in the environment with DT, mainly through the modification of its physical and chemical properties by various methods, should be applied. The aim of this research was to develop a simple and inexpensive material showing more favourable chemical and physical properties compared with unenriched DT in terms of metal immobilisation. Diatomite (DT), after calcination, was used in the study, considering three grain fractions, i.e., 0–1 mm (DT1); 0–0.5 mm (DT2) and 5–100 µm (DT3). Biochar (BC), dolomite (DL) and bentonite (BN) were used as additives. The proportion of DTs in the mixtures amounted to 75%, and of the additive, 25%. The use of unenriched DTs after calcination poses the risk of releasing heavy metals into the environment. Enrichment of the DTs with BC and DL resulted in a reduction or absence of Cd, Zn, Pb and Ni in aqueous extracts. It was found that for the specific surface area values obtained, the additive used for the DTs was of crucial importance. The reduction in DT toxicity has been proven under the influence of various additives. The mixtures of the DTs with DL and BN had the least toxicity. The obtained results have economic importance, as the production of the best quality sorbents from locally available raw materials reduces transport costs and thus the environmental impact. In addition, the production of highly efficient sorbents reduces the consumption of critical raw materials. It is estimated that the savings from producing sorbents with the parameters described in the article can be significant in comparison with popular competitive materials of other origins. Full article
(This article belongs to the Special Issue Advances in Polymers and Functionalized Materials in the Environment)
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11 pages, 7162 KiB  
Article
Effect of Mechanical Stirring on High-Speed GMAW Hump Bead
by Jun Xiao, Xiaolei Wang, Shengnan Gai, Shujun Chen and Wenhao Huang
Materials 2023, 16(12), 4493; https://doi.org/10.3390/ma16124493 - 20 Jun 2023
Cited by 1 | Viewed by 980
Abstract
High-speed GMAW tends to be accompanied by periodic humping defects, thereby reducing the weld bead quality. A new method was proposed to actively control the weld pool flow for eliminating humping defects. A high-melting point solid pin was designed and inserted into the [...] Read more.
High-speed GMAW tends to be accompanied by periodic humping defects, thereby reducing the weld bead quality. A new method was proposed to actively control the weld pool flow for eliminating humping defects. A high-melting point solid pin was designed and inserted into the weld pool to stir the liquid metal during the welding process. The characteristics of the backward molten metal flow were extracted and compared by a high-speed camera. Combined with particle tracing technology, the momentum of the backward metal flow was calculated and analyzed, and the mechanism of hump suppression in high speed GMAW was further revealed. The stirring pin interacted with the liquid molten pool, resulting in a vortex zone behind the stirring pin, which significantly reduced the momentum of the backward molten metal flow, and thus it inhibited the formation of humping beads. Full article
(This article belongs to the Special Issue Advances in Welding Process and Materials)
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20 pages, 9740 KiB  
Article
High-Temperature Corrosion Behavior of Selected HVOF-Sprayed Super-Alloy Based Coatings in Aggressive Environment at 800 °C
by Zdeněk Česánek, Kateřina Lencová, Jan Schubert, Jakub Antoš, Radek Mušálek, František Lukáč, Marek Palán, Marek Vostřák and Šárka Houdková
Materials 2023, 16(12), 4492; https://doi.org/10.3390/ma16124492 - 20 Jun 2023
Cited by 3 | Viewed by 1240
Abstract
This study is focused on the high-temperature corrosion evaluation of selected thermally sprayed coatings. NiCoCrAlYHfSi, NiCoCrAlY, NiCoCrAlTaReY, and CoCrAlYTaCSi coatings were sprayed on the base material 1.4923. This material is used as a cost-efficient construction material for components of power equipment. All evaluated [...] Read more.
This study is focused on the high-temperature corrosion evaluation of selected thermally sprayed coatings. NiCoCrAlYHfSi, NiCoCrAlY, NiCoCrAlTaReY, and CoCrAlYTaCSi coatings were sprayed on the base material 1.4923. This material is used as a cost-efficient construction material for components of power equipment. All evaluated coatings were sprayed using HP/HVOF (High-Pressure/High-Velocity Oxygen Fuel) technology. High-temperature corrosion testing was performed in a molten salt environment typical for coal-fired boilers. All coatings were exposed to the environment of 75% Na2SO4 and 25% NaCl at the temperature of 800 °C under cyclic conditions. Each cycle consisted of 1 h heating in a silicon carbide tube furnace followed by 20 min of cooling. The weight change measurement was performed after each cycle to establish the corrosion kinetics. Optical microscopy (OM), scanning electron microscopy (SEM), and elemental analysis (EDS) were used to analyze the corrosion mechanism. The CoCrAlYTaCSi coating showed the best corrosion resistance of all the evaluated coatings, followed by NiCoCrAlTaReY and NiCoCrAlY. All the evaluated coatings performed better in this environment than the reference P91 and H800 steels. Full article
(This article belongs to the Special Issue Materials Corrosion in Molten Salts and Heat Storage)
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14 pages, 3002 KiB  
Article
Micro-CT Evaluation of Microgaps at Implant-Abutment Connection
by Jakub Kowalski, Adam K. Puszkarz, Mateusz Radwanski, Jerzy Sokolowski, Michal Cichomski, Rim Bourgi, Louis Hardan, Salvatore Sauro and Monika Lukomska-Szymanska
Materials 2023, 16(12), 4491; https://doi.org/10.3390/ma16124491 - 20 Jun 2023
Cited by 1 | Viewed by 2273
Abstract
The assessment of microgaps at the implant–abutment interface is an important factor that may influence clinical success. Thus, the aim of this study was to evaluate the size of microgaps between prefabricated and customised abutments (Astra Tech, Dentsply, York, PA, USA; Apollo Implants [...] Read more.
The assessment of microgaps at the implant–abutment interface is an important factor that may influence clinical success. Thus, the aim of this study was to evaluate the size of microgaps between prefabricated and customised abutments (Astra Tech, Dentsply, York, PA, USA; Apollo Implants Components, Pabianice, Poland) mounted on a standard implant. The measurement of the microgap was performed using micro-computed tomography (MCT). Due to 15-degree rotation of samples, 24 microsections were obtained. Scans were performed at four levels established at the interface between the abutment and the implant neck. Moreover, the volume of the microgap was evaluated. The size of the microgap at all measured levels varied from 0.1 to 3.7 µm for Astra and from 0.1 to 4.9 µm for Apollo (p > 0.05). Moreover, 90% of the Astra specimens and 70% of the Apollo specimens did not exhibit any microgaps. The highest mean values of microgap size for both groups were detected at the lowest portion of the abutment (p > 0.05). Additionally, the average microgap volume was greater for Apollo than for Astra (p > 0.05). It can be concluded that most samples did not exhibit any microgaps. Furthermore, the linear and volumetric dimensions of microgaps observed at the interface between Apollo or Astra abutments and Astra implants were comparable. Additionally, all tested components presented microgaps (if any) that were clinically acceptable. However, the microgap size of the Apollo abutment was higher and more variable than that of the Astra one. Full article
(This article belongs to the Special Issue Biomaterials and Mechanics in Dentistry)
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22 pages, 4002 KiB  
Review
Lead-Free Halide Double Perovskite for High-Performance Photodetectors: Progress and Perspective
by Xiaoyan Li, Junzhe Shi, Jianjun Chen, Zuojun Tan and Hongwei Lei
Materials 2023, 16(12), 4490; https://doi.org/10.3390/ma16124490 - 20 Jun 2023
Cited by 10 | Viewed by 2299
Abstract
Lead halide perovskite has become a promising candidate for high-performance photodetectors (PDs) due to its attractive optical and electrical properties, such as high optical absorption coefficient, high carrier mobility, and long carrier diffusion length. However, the presence of highly toxic lead in these [...] Read more.
Lead halide perovskite has become a promising candidate for high-performance photodetectors (PDs) due to its attractive optical and electrical properties, such as high optical absorption coefficient, high carrier mobility, and long carrier diffusion length. However, the presence of highly toxic lead in these devices has limited their practical applications and even hindered their progress toward commercialization. Therefore, the scientific community has been committed to searching for low-toxic and stable perovskite-type alternative materials. Lead-free double perovskite, which is still in the preliminary stage of exploration, has achieved inspiring results in recent years. In this review, we mainly focus on two types of lead-free double perovskite based on different Pb substitution strategies, including A2M(I)M(III)X6 and A2M(IV)X6. We review the research progress and prospects of lead-free double perovskite photodetectors in the past three years. More importantly, from the perspective of optimizing the inherent defects in materials and improving device performance, we propose some feasible pathways and make an encouraging perspective for the future development of lead-free double perovskite photodetectors. Full article
(This article belongs to the Special Issue Recent Progress of Perovskite Photodetectors)
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10 pages, 5205 KiB  
Article
Improving the Mechanical Properties of Mg-5Al-2Ca-1Mn-0.5Zn Alloy through Rotary Swaging
by Bin Li, Hao Chen, Xiangnan Ke, Guobing Wei and Qingshan Yang
Materials 2023, 16(12), 4489; https://doi.org/10.3390/ma16124489 - 20 Jun 2023
Cited by 2 | Viewed by 905
Abstract
To meet the demand for more extensive applications of Mg alloys, a Mg-5Al-2Ca-1Mn-0.5Zn alloy without RE was prepared in this paper, and its mechanical properties were further improved by conventional hot extrusion and subsequent rotary swaging. The results show that the hardness of [...] Read more.
To meet the demand for more extensive applications of Mg alloys, a Mg-5Al-2Ca-1Mn-0.5Zn alloy without RE was prepared in this paper, and its mechanical properties were further improved by conventional hot extrusion and subsequent rotary swaging. The results show that the hardness of the alloy decreases along the radial central region after rotary swaging. The strength and hardness of the central area are lower, but the ductility is higher. The yield strength and ultimate tensile strength of the alloy in the peripheral area after rotary swaging reach 352 MPa and 386 MPa, respectively, while the elongation remains at 9.6%, exhibiting better strength–ductility synergy. The grain refinement and dislocation increase caused by rotary swaging promoted strength improvement. The activation of non-basal slips during rotary swaging is an important reason for the alloy to maintain good plasticity while improving strength. Full article
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14 pages, 2880 KiB  
Article
Charge Transfer and Charge Trapping Processes in Ca- or Al-Co-doped Lu2SiO5 and Lu2Si2O7 Scintillators Activated by Pr3+ or Ce3+ Ions
by Valentyn Laguta, Lubomir Havlak, Vladimir Babin, Jan Barta, Jan Pejchal and Martin Nikl
Materials 2023, 16(12), 4488; https://doi.org/10.3390/ma16124488 - 20 Jun 2023
Cited by 2 | Viewed by 1157
Abstract
Lutetium oxyorthosilicate Lu2SiO5 (LSO) and pyrosilicate Lu2Si2O7 (LPS) activated by Ce3+ or Pr3+ are known to be effective and fast scintillation materials for the detection of X-rays and γ-rays. Their performances can be [...] Read more.
Lutetium oxyorthosilicate Lu2SiO5 (LSO) and pyrosilicate Lu2Si2O7 (LPS) activated by Ce3+ or Pr3+ are known to be effective and fast scintillation materials for the detection of X-rays and γ-rays. Their performances can be further improved by co-doping with aliovalent ions. Herein, we investigate the Ce3+(Pr3+) → Ce4+(Pr4+) conversion and the formation of lattice defects stimulated by co-doping with Ca2+ and Al3+ in LSO and LPS powders prepared by the solid-state reaction process. The materials were studied by electron paramagnetic resonance (EPR), radioluminescence spectroscopy, and thermally stimulated luminescence (TSL), and scintillation decays were measured. EPR measurements of both LSO:Ce and LPS:Ce showed effective Ce3+ → Ce4+ conversions stimulated by Ca2+ co-doping, while the effect of Al3+ co-doping was less effective. In Pr-doped LSO and LPS, a similar Pr3+ → Pr4+ conversion was not detected by EPR, suggesting that the charge compensation of Al3+ and Ca2+ ions is realized via other impurities and/or lattice defects. X-ray irradiation of LPS creates hole centers attributed to a hole trapped in an oxygen ion in the neighborhood of Al3+ and Ca2+. These hole centers contribute to an intense TSL glow peak at 450–470 K. In contrast to LPS, only weak TSL peaks are detected in LSO and no hole centers are visible via EPR. The scintillation decay curves of both LSO and LPS show a bi-exponential decay with fast and slow component decay times of 10–13 ns and 30–36 ns, respectively. The decay time of the fast component shows a small (6–8%) decrease due to co-doping. Full article
(This article belongs to the Special Issue Advanced Luminescent Materials and Devices)
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11 pages, 3970 KiB  
Article
Fabrication and Process Optimization of Chinese Fir-Derived SiC Ceramic with High-Performance Friction Properties
by Fuling Liu, Shanshan Chang, Yuanjuan Bai, Xianjun Li, Xiaojian Zhou and Jinbo Hu
Materials 2023, 16(12), 4487; https://doi.org/10.3390/ma16124487 - 20 Jun 2023
Cited by 1 | Viewed by 1087
Abstract
In this study, a novel friction material with biomass-ceramic (SiC) dual matrixes was fabricated using Chinese fir pyrocarbon via the liquid-phase silicon infiltration and in situ growth method. SiC can be grown in situ on the surface of a carbonized wood cell wall [...] Read more.
In this study, a novel friction material with biomass-ceramic (SiC) dual matrixes was fabricated using Chinese fir pyrocarbon via the liquid-phase silicon infiltration and in situ growth method. SiC can be grown in situ on the surface of a carbonized wood cell wall by mixing and calcination of wood and Si powder. The samples were characterized using XRD, SEM, and SEM–EDS analysis. Meanwhile, their friction coefficients and wear rates were tested to study their frictional properties. To explore the influence of crucial factors on friction performance, response surface analysis was also conducted to optimize the preparation process. The results showed that longitudinally crossed and disordered SiC nanowhiskers were grown on the carbonized wood cell wall, which could enhance the strength of SiC. The designed biomass-ceramic material had satisfying friction coefficients and low wear rates. The response surface analysis results indicate that the optimal process could be determined (carbon to silicon ratio of 3:7, reaction temperature of 1600 °C, and 5% adhesive dosage). Biomass-ceramic materials utilizing Chinese fir pyrocarbon could display great promise to potentially replace the current iron–copper-based alloy materials used in brake systems. Full article
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16 pages, 10074 KiB  
Article
Migration Behavior of Inclusions at the Solidification Front in Oxide Metallurgy
by Chunliang Yan, Fengming Wang, Wenling Mo, Pengcheng Xiao and Qingjun Zhang
Materials 2023, 16(12), 4486; https://doi.org/10.3390/ma16124486 - 20 Jun 2023
Viewed by 970
Abstract
Distribution of inclusions plays an essential role in inducing intracrystalline ferrite, and the migration behavior of inclusions during solidification has a significant influence on their distribution. The solidification process of DH36 (ASTMA36) steel and the migration behavior of inclusions at the solidification front [...] Read more.
Distribution of inclusions plays an essential role in inducing intracrystalline ferrite, and the migration behavior of inclusions during solidification has a significant influence on their distribution. The solidification process of DH36 (ASTMA36) steel and the migration behavior of inclusions at the solidification front were observed in situ using high-temperature laser confocal microscopy. The annexation, rejection, and drift behavior of inclusions in the solid–liquid two-phase region were analyzed, providing a theoretical basis for regulating the distribution of inclusions. Analysis of inclusion trajectories showed that the velocity of inclusions decreases significantly as they near the solidification front. Further study of the force on inclusions at the solidification frontier shows three situations: attraction, repulsion, and no influence. Additionally, a pulsed magnetic field was applied during the solidification process. The original dendritic growth mode changed to that of equiaxed crystals. The compelling attraction distance for inclusion particles with a diameter of 6 μm at the solidification interface front increased from 46 μm to 89 μm, i.e., the effective length for the solidification front engulfing inclusions can be increased by controlling the flow of molten steel. Full article
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18 pages, 6305 KiB  
Article
Study on Quasi-Static Axial Compression Performance and Energy Absorption of Aluminum Foam-Filled Steel Tubes
by Zhanguang Wang and Jianhua Shao
Materials 2023, 16(12), 4485; https://doi.org/10.3390/ma16124485 - 20 Jun 2023
Viewed by 944
Abstract
To study the axial compression performance of aluminum foam-filled steel tube and empty steel tube as objects, such tubes are studied in this paper, which explores the carrying capacity and deformation behavior of aluminum foam-filled steel tube with different lengths under a quasi-static [...] Read more.
To study the axial compression performance of aluminum foam-filled steel tube and empty steel tube as objects, such tubes are studied in this paper, which explores the carrying capacity and deformation behavior of aluminum foam-filled steel tube with different lengths under a quasi-static axial load through experimental research. The carrying capacity, deformation behavior, stress distribution, and energy absorption characteristics of empty steel tubes and foam-filled steel tubes are compared through finite element numerical simulation. The results indicate that, compared with the empty steel tube, the aluminum foam-filled steel tube still presents a large residual carrying capacity after the axial force exceeds the ultimate load, and the whole compression process reflects steady-state compression. In addition, the axial and lateral deformation amplitudes of the foam-filled steel tube decrease significantly during the whole compression process. After filling the foam metal, the large stress area decreases and the energy absorption capacity improves. Full article
(This article belongs to the Special Issue Advanced Steel Composites in Construction Engineering)
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17 pages, 6304 KiB  
Article
Creep Behavior of CLT Beams with Finite Thickness Layers of Flexible Adhesives
by Klaudia Śliwa-Wieczorek, Paweł Szeptyński, Tomasz Kozik and Martino Gubert
Materials 2023, 16(12), 4484; https://doi.org/10.3390/ma16124484 - 20 Jun 2023
Cited by 2 | Viewed by 1089
Abstract
Creep behavior of Cross-Laminated-Timber (CLT) beams with a finite-thickness layer of flexible adhesives is investigated. Creep tests were carried out for all component materials as well as for the composite structure itself. Three-point bending creep tests were performed for spruce planks and for [...] Read more.
Creep behavior of Cross-Laminated-Timber (CLT) beams with a finite-thickness layer of flexible adhesives is investigated. Creep tests were carried out for all component materials as well as for the composite structure itself. Three-point bending creep tests were performed for spruce planks and for CLT beams, and uniaxial compression creep tests were performed for two flexible polyurethane adhesives: Sika® PS and Sika® PMM. All materials are characterized with the use of the three-element Generalized Maxwell Model. The results of creep tests for component materials were used in elaboration of the Finite Element (FE) model. The problem of linear theory of viscoelasticity was solved numerically with the use of the Abaqus software. Obtained results of Finite Element Analysis (FEA) are compared with experimental results. Full article
(This article belongs to the Special Issue Rheology and Mechanical Properties of Wood and Wood-Based Materials)
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24 pages, 2090 KiB  
Review
Bioengineering Composite Aerogel-Based Scaffolds That Influence Porous Microstructure, Mechanical Properties and In Vivo Regeneration for Bone Tissue Application
by Mariana Souto-Lopes, Maria Helena Fernandes, Fernando Jorge Monteiro and Christiane Laranjo Salgado
Materials 2023, 16(12), 4483; https://doi.org/10.3390/ma16124483 - 20 Jun 2023
Cited by 5 | Viewed by 1499
Abstract
Tissue regeneration of large bone defects is still a clinical challenge. Bone tissue engineering employs biomimetic strategies to produce graft composite scaffolds that resemble the bone extracellular matrix to guide and promote osteogenic differentiation of the host precursor cells. Aerogel-based bone scaffold preparation [...] Read more.
Tissue regeneration of large bone defects is still a clinical challenge. Bone tissue engineering employs biomimetic strategies to produce graft composite scaffolds that resemble the bone extracellular matrix to guide and promote osteogenic differentiation of the host precursor cells. Aerogel-based bone scaffold preparation methods have been increasingly improved to overcome the difficulties in balancing the need for an open highly porous and hierarchically organized microstructure with compression resistance to withstand bone physiological loads, especially in wet conditions. Moreover, these improved aerogel scaffolds have been implanted in vivo in critical bone defects, in order to test their bone regeneration potential. This review addresses recently published studies on aerogel composite (organic/inorganic)-based scaffolds, having in mind the various cutting-edge technologies and raw biomaterials used, as well as the improvements that are still a challenge in terms of their relevant properties. Finally, the lack of 3D in vitro models of bone tissue for regeneration studies is emphasized, as well as the need for further developments to overcome and minimize the requirement for studies using in vivo animal models. Full article
(This article belongs to the Special Issue Advance in Biomaterials for Tissue Engineering)
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15 pages, 4237 KiB  
Article
Performance Study of a Leaf-Vein-like Structured Vapor Chamber
by Zhihao Zhou, Xu Wang and Yongmin Zhou
Materials 2023, 16(12), 4482; https://doi.org/10.3390/ma16124482 - 20 Jun 2023
Cited by 1 | Viewed by 1060
Abstract
As optoelectronic products continue to advance rapidly, the need for effective heat dissipation has become increasingly crucial due to the emphasis on miniaturization and high integration. The vapor chamber is widely used for cooling electronic systems as a passive liquid–gas two-phase high-efficiency heat [...] Read more.
As optoelectronic products continue to advance rapidly, the need for effective heat dissipation has become increasingly crucial due to the emphasis on miniaturization and high integration. The vapor chamber is widely used for cooling electronic systems as a passive liquid–gas two-phase high-efficiency heat exchange device. In this paper, we designed and manufactured a new kind of vapor chamber using cotton yarn as the wick material, combined with a fractal pattern layout of leaf veins. A comprehensive investigation was conducted to analyze the performance of the vapor chamber under natural convection circumstances. SEM showed that many tiny pores and capillaries were formed between the cotton yarn fibers, which are very suitable as the wick material of the vapor chamber. Additionally, experimental findings demonstrated the favorable flow and heat transfer characteristics of the cotton yarn wick within the vapor chamber, which makes the vapor chamber have significant heat dissipation capability, compared to the other two vapor chambers; this vapor chamber has a thermal resistance of only 0.43 °C/W at a thermal load of 8.7 W. In addition, the vapor chamber showed good antigravity capability, and its performance did not show significant changes between horizontal and vertical positions; the maximum difference in thermal resistance at four tilt angles is only 0.06 °C/W. This paper also studied the influence of vacuum degree and filling amount on the performance of the vapor chamber. These findings indicate that the proposed vapor chamber provides a promising thermal management solution for some mobile electronic devices and provides a new idea for selecting wick materials for vapor chambers. Full article
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17 pages, 10190 KiB  
Article
Effects of In-Situ Reaction, Extrusion Ratio and CeO2 on the Performance of Al-Ti-C-(Ce) Grain Refiners for Refining Pure Aluminum Grains
by Qianwen Bi, Xiaoxu Luo, Lu Guo, Xiaoqing Zuo, Bei Huang, Jianhong Yi and Yun Zhou
Materials 2023, 16(12), 4481; https://doi.org/10.3390/ma16124481 - 20 Jun 2023
Viewed by 978
Abstract
Al-Ti-C-(Ce) grain refiners were prepared by combining in-situ reaction, hot extrusion, and adding CeO2. The effects of second phase TiC particle size and distribution, extrusion ratio, and Ce addition on the grain-refining performance of grain refiners were investigated. The results show [...] Read more.
Al-Ti-C-(Ce) grain refiners were prepared by combining in-situ reaction, hot extrusion, and adding CeO2. The effects of second phase TiC particle size and distribution, extrusion ratio, and Ce addition on the grain-refining performance of grain refiners were investigated. The results show that about 10 nm TiC particles are dispersed on the surface and inside of 100–200 nm Ti particles by in-situ reaction. The Al-Ti-C grain refiners, which are made, by hot extrusion, of a mixture of in-situ reaction Ti/TiC composite powder and Al powder, increase the effective nucleation phase of α-Al and hinder grain growth due to the fine and dispersed TiC; this results in the average size of pure aluminum grains to decrease from 1912.4 μm to 504.8 μm (adding 1 wt.% Al-Ti-C grain refiner). Additionally, with the increase of the extrusion ratio from 13 to 30, the average size of pure aluminum grains decreases further to 470.8 μm. This is because the micropores in the matrix of grain refiners are reduced, and the nano-TiC aggregates are dispersed with the fragmentation of Ti particles, resulting in a sufficient Al-Ti reaction and an enhanced nucleation effect of nano-TiC. Furthermore, Al-Ti-C-Ce grain refiners were prepared by adding CeO2. Under the conditions of holding for 3–5 min and adding a 5.5 wt.% Al-Ti-C-Ce grain refiner, the average size of pure aluminum grains is reduced to 48.4–48.8 μm. The reason for the excellent grain-refining and good anti-fading performance of the Al-Ti-C-Ce grain refiner is presumedly related to the Ti2Al20Ce rare earth phases and [Ce] atoms, which hinder agglomeration, precipitation, and dissolution of the TiC and TiAl3 particles. Full article
(This article belongs to the Section Metals and Alloys)
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14 pages, 3522 KiB  
Article
Comparative Study of Corrosion Behaviors of WC-NiMo and WC-Co Cemented Carbides
by Nádia Alves Nery Balbino, Edmilson Otoni Corrêa, Danilo Roque Huanca, Flávio Amaury de Freitas Matos and Livio de Carvalho Valeriano
Materials 2023, 16(12), 4480; https://doi.org/10.3390/ma16124480 - 20 Jun 2023
Cited by 3 | Viewed by 1170
Abstract
In this paper, the influence of a nickel binder metal and molybdenum carbide as an additional alloying element on the microstructure and corrosion behavior of WC-based cemented carbides, processed by conventional powder metallurgy, was studied, and a comparison with conventional cemented carbide (WC-Co) [...] Read more.
In this paper, the influence of a nickel binder metal and molybdenum carbide as an additional alloying element on the microstructure and corrosion behavior of WC-based cemented carbides, processed by conventional powder metallurgy, was studied, and a comparison with conventional cemented carbide (WC-Co) was carried out. The sintered alloys were characterized, before and after corrosive tests, by analyses using optical microscopy, scanning electron microscopy, energy dispersive X-ray spectroscopy, and X-ray diffraction. The corrosion resistance of the cemented carbides was investigated by open circuit potential, potentiodynamic polarization, and electrochemical impedance spectroscopy in a 3.5 wt.% NaCl solution. The WC-NiMo cemented carbides showed microstructures similar to those of WC-Co; however, pores and binder islands were observed in the microstructures. The corrosion tests showed promising results, the WC-NiMo cemented carbide showed superior corrosion resistance and higher passivation capacity than the WC-Co cemented carbide. The WC-NiMo alloy showed a higher EOC 0.18 V vs. Ag|AgCl|KCl3mol/L than the WC-Co (EOC0.45 V vs. Ag|AgCl|KCl3mol/L). The potentiodynamic polarization curves showed lower current density values throughout the potential range for the WC-NiMo alloy, and it was observed that Ecorr was less negative (0.416 V vs. Ag|AgCl|KCl3mol/L) than for WC-Co (0.543 V vs. V vs. Ag|AgCl|KCl3mol/L). The EIS analysis confirmed low rate corrosion of WC-NiMo associated with the formation of a passive thin layer. This alloy showed a higher Rct (1970.70 Ω). Full article
(This article belongs to the Special Issue The 15th Anniversary of Materials—Recent Advances in Corrosion)
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14 pages, 6732 KiB  
Article
Performance Optimization of Pb0.97La0.03Sc0.45Ta0.45Ti0.1O3 Ceramics by Annealing Process
by Zihan Su, Lingyu Wan, Fenglai Mo, Jiayu Li, Boxun Liu, Chuangjian Liang, Jinsong Xu, Devki N. Talwar, Hang Li and Huilu Yao
Materials 2023, 16(12), 4479; https://doi.org/10.3390/ma16124479 - 20 Jun 2023
Viewed by 977
Abstract
The annealing effects on Pb0.97La0.03Sc0.45Ta0.45Ti0.1O3 (PLSTT) ceramics prepared by the solid-state reaction method are systemically investigated using experimental and theoretical techniques. Comprehensive studies are performed on the PLSTT samples by varying annealing [...] Read more.
The annealing effects on Pb0.97La0.03Sc0.45Ta0.45Ti0.1O3 (PLSTT) ceramics prepared by the solid-state reaction method are systemically investigated using experimental and theoretical techniques. Comprehensive studies are performed on the PLSTT samples by varying annealing time (AT) from t (=0, 10, 20, 30, 40, 50 and 60) h. The properties involving ferroelectric polarization (FP), electrocaloric (EC) effect, energy harvesting performance (EHP) and energy storage performance (ESP) are reported, compared and contrasted. All these features are seen to gradually improve with the increase in AT, and they all reach the climaxed-shaped values and then decrease by further increasing the AT. For t = 40 h, the maximum FP (23.2 µC/cm2) is attained at an electric field of 50 kV/cm, while the high EHP effects (0.297 J/cm3) and positive EC are achieved (for ΔT~0.92 K and ΔS~0.92 J/(K·kg)) at 45 kV/cm. The EHP value of the PLSTT ceramics increased by 21.7% while the polarization value was enhanced by 33.3%. At t = 30 h, the ceramics have attained the best ESP value of 0.468 J/cm3 with an energy loss of 0.05 J/cm3. We strongly believe that the AT plays a crucial role in the optimization of different traits of the PLSTT ceramics. Full article
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16 pages, 8277 KiB  
Article
Polyvinylpyrrolidone—Alginate—Carbonate Hydroxyapatite Porous Composites for Dental Applications
by Anna A. Forysenkova, Inna V. Fadeeva, Dina V. Deyneko, Alevtina N. Gosteva, Georgy V. Mamin, Darya V. Shurtakova, Galina A. Davydova, Viktoriya G. Yankova, Iulian V. Antoniac and Julietta V. Rau
Materials 2023, 16(12), 4478; https://doi.org/10.3390/ma16124478 - 20 Jun 2023
Cited by 6 | Viewed by 1842
Abstract
An alternative approach for the currently used replacement therapy in dentistry is to apply materials that restore tooth tissue. Among them, composites, based on biopolymers with calcium phosphates, and cells can be applied. In the present work, a composite based on polyvinylpyrrolidone (PVP) [...] Read more.
An alternative approach for the currently used replacement therapy in dentistry is to apply materials that restore tooth tissue. Among them, composites, based on biopolymers with calcium phosphates, and cells can be applied. In the present work, a composite based on polyvinylpyrrolidone (PVP) and alginate (Alg) with carbonate hydroxyapatite (CHA) was prepared and characterized. The composite was investigated by X-ray diffraction, infrared spectroscopy, electron paramagnetic resonance (EPR) and scanning electron microscopy methods, and the microstructure, porosity, and swelling properties of the material were described. In vitro studies included the MTT test using mouse fibroblasts, and adhesion and survivability tests with human dental pulp stem cells (DPSC). The mineral component of the composite corresponded to CHA with an admixture of amorphous calcium phosphate. The presence of a bond between the polymer matrix and CHA particles was shown by EPR. The structure of the material was represented by micro- (30–190 μm) and nano-pores (average 8.71 ± 4.15 nm). The swelling measurements attested that CHA addition increased the polymer matrix hydrophilicity by 200%. In vitro studies demonstrated the biocompatibility of PVP-Alg-CHA (95 ± 5% cell viability), and DPSC located inside the pores. It was concluded that the PVP-Alg-CHA porous composite is promising for dentistry applications. Full article
(This article belongs to the Special Issue Advanced Dental Materials: From Design to Application)
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15 pages, 3491 KiB  
Article
Influence of Process Parameter and Alloy Composition on Misoriented Eutectics in Single-Crystal Nickel-Based Superalloys
by Tobias Wittenzellner, Shieren Sumarli, Zijin Dai, Ocson Cocen, Helge Schaar, Fu Wang, Dexin Ma and Andreas Bührig-Polaczek
Materials 2023, 16(12), 4477; https://doi.org/10.3390/ma16124477 - 20 Jun 2023
Viewed by 1291
Abstract
The nucleation and the growth of misoriented micro-structure components in single crystals depend on various process parameters and alloy compositions. Therefore, in this study, the influence of different cooling rates on carbon-free, as well as carbon-containing, nickel-based superalloys was investigated. Castings were carried [...] Read more.
The nucleation and the growth of misoriented micro-structure components in single crystals depend on various process parameters and alloy compositions. Therefore, in this study, the influence of different cooling rates on carbon-free, as well as carbon-containing, nickel-based superalloys was investigated. Castings were carried out using the Bridgman and Bridgman–Stockbarger techniques under industrial and laboratory conditions, respectively, to analyze the impact of temperature gradients and withdrawing rates on six alloy compositions. Here, it was confirmed that eutectics could assume a random crystallographic orientation due to homogeneous nucleation in the residual melt. In carbon-containing alloys, eutectics also nucleated at low surface-to-volume ratio carbides due to the accumulation of eutectic-forming elements around the carbide. This mechanism occurred in alloys with high carbon contents and at low cooling rates. Furthermore, micro-stray grains were formed by the closure of residual melt in Chinese-script-shaped carbides. If the carbide structure was open in the growth direction, they could expand into the interdendritic region. Eutectics additionally nucleated on these micro-stray grains and consequently had a different crystallographic orientation compared with the single crystal. In conclusion, this study revealed the process parameters that induced the formation of misoriented micro-structures, which prevented the formation of these solidification defects by optimizing the cooling rate and the alloy composition. Full article
(This article belongs to the Section Metals and Alloys)
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15 pages, 4605 KiB  
Article
Synthesis and Evaluation of Engineering Properties of Polymer-Coated Glass Beads
by Boyoung Yoon, Hyunwook Choo and Changho Lee
Materials 2023, 16(12), 4476; https://doi.org/10.3390/ma16124476 - 20 Jun 2023
Cited by 1 | Viewed by 1371
Abstract
Modern construction projects are often challenging, which has increased the demand for innovative materials that ensure improved safety, durability, and functionality. To explore the potential of enhancing soil material functionality, this study synthesized polyurethane on the surface of glass beads and evaluated their [...] Read more.
Modern construction projects are often challenging, which has increased the demand for innovative materials that ensure improved safety, durability, and functionality. To explore the potential of enhancing soil material functionality, this study synthesized polyurethane on the surface of glass beads and evaluated their mechanical properties. The synthesis of polymer proceeded according to a predetermined procedure, where the polymerization was confirmed through analysis of chemical structure by Fourier transform infrared spectroscopy (FT-IR) and microstructure observation by a scanning electron microscope (SEM) after complete synthesis. The constrained modulus (M) and the maximum shear modulus (Gmax) of mixtures with synthesized materials were examined by using an oedometer cell equipped with bender elements under a zero lateral strain condition. Both M and Gmax decreased with an increase in the contents of polymerized particles due to a decrease in the number of interparticle contacts and contact stiffness induced by the surface modification. The adhesion property of the polymer induced a stress-dependent change in M but was observed to have little effect on Gmax. Compared to the behavior of the rubber-sand mixtures, polymerized particles show the advantage of a smaller reduction of M. Full article
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11 pages, 3606 KiB  
Article
High Entropy Borides Synthesized by the Thermal Reduction of Metal Oxides in a Microwave Plasma
by Bria Storr, Carolina Amezaga, Luke Moore, Seth Iwan, Yogesh K. Vohra, Cheng-Chien Chen and Shane A. Catledge
Materials 2023, 16(12), 4475; https://doi.org/10.3390/ma16124475 - 20 Jun 2023
Viewed by 1622
Abstract
Metal oxide thermal reduction, enabled by microwave-induced plasma, was used to synthesize high entropy borides (HEBs). This approach capitalized on the ability of a microwave (MW) plasma source to efficiently transfer thermal energy to drive chemical reactions in an argon-rich plasma. A predominantly [...] Read more.
Metal oxide thermal reduction, enabled by microwave-induced plasma, was used to synthesize high entropy borides (HEBs). This approach capitalized on the ability of a microwave (MW) plasma source to efficiently transfer thermal energy to drive chemical reactions in an argon-rich plasma. A predominantly single-phase hexagonal AlB2-type structural characteristic of HEBs was obtained by boro/carbothermal reduction as well as by borothermal reduction. We compare the microstructural, mechanical, and oxidation resistance properties using the two different thermal reduction approaches (i.e., with and without carbon as a reducing agent). The plasma-annealed HEB (Hf0.2, Zr0.2, Ti0.2, Ta0.2, Mo0.2)B2 made via boro/carbothermal reduction resulted in a higher measured hardness (38 ± 4 GPa) compared to the same HEB made via borothermal reduction (28 ± 3 GPa). These hardness values were consistent with the theoretical value of ~33 GPa obtained by first-principles simulations using special quasi-random structures. Sample cross-sections were evaluated to examine the effects of the plasma on structural, compositional, and mechanical homogeneity throughout the HEB thickness. MW-plasma-produced HEBs synthesized with carbon exhibit a reduced porosity, higher density, and higher average hardness when compared to HEBs made without carbon. Full article
(This article belongs to the Special Issue Design, Processing and Properties of High Entropy Ceramics)
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11 pages, 3116 KiB  
Article
Microstructural and Performance Analysis of TP304H/T22 Dissimilar Steel Welded Joints
by Jian Sun, Tong Wang, Fuguang Liu, Zhoubo Zhang, Yunhui Chen, He Lin, Hui Liu, Xiaohui Zhao and Xiaole Cheng
Materials 2023, 16(12), 4474; https://doi.org/10.3390/ma16124474 - 20 Jun 2023
Cited by 1 | Viewed by 1256
Abstract
In the power plant boiler industry, dissimilar steel welding is widely used in the connection of thermal power generation units. As an important component of the unit, research on the organizational properties of dissimilar steel welded joints has significant guidance for the life [...] Read more.
In the power plant boiler industry, dissimilar steel welding is widely used in the connection of thermal power generation units. As an important component of the unit, research on the organizational properties of dissimilar steel welded joints has significant guidance for the life design of the joint. For the long-term service state of TP304H/T22 dissimilar steel welded joints, the microstructure’s morphological evolution, the microhardness, and the tensile properties of tube samples were analyzed using tests and numerical simulations. The results show that the microstructure of each part of the welded joint was free of damaged features, such as a creep cavity and intergranular cracks. The microhardness of the weld was higher than that of the base metal. In the tensile test, the welded joints broke at the weld metal at room temperature and at the side of the TP304H base metal at a temperature of 550 °C. The tensile fracture morphology demonstrated a change from a ductile fracture to a hybrid fracture when the temperature rose. The fusion zone and base metal on the TP304H side were the stress concentration areas of the welded joint, which easily sprouted cracks. This study holds significant reference value in assessing the safety and reliability of dissimilar steel welded joints in superheater units. Full article
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22 pages, 11967 KiB  
Article
Microstructural Changes and Determination of a Continuous Cooling Transformation (CCT) Diagram Using Dilatometric Analysis of M398 High-Alloy Tool Steel Produced by Microclean Powder Metallurgy
by Michal Krbata, Robert Ciger, Marcel Kohutiar, Maros Eckert, Igor Barenyi, Bohdan Trembach, Andrej Dubec, Jana Escherova, Matúš Gavalec and Naďa Beronská
Materials 2023, 16(12), 4473; https://doi.org/10.3390/ma16124473 - 19 Jun 2023
Cited by 6 | Viewed by 1408
Abstract
The paper deals with the dilatometric study of high-alloy martensitic tool steel with the designation M398 (BÖHLER), which is produced by the powder metallurgy process. These materials are used to produce screws for injection molding machines in the plastic industry. Increasing the life [...] Read more.
The paper deals with the dilatometric study of high-alloy martensitic tool steel with the designation M398 (BÖHLER), which is produced by the powder metallurgy process. These materials are used to produce screws for injection molding machines in the plastic industry. Increasing the life cycle of these screws leads to significant economic savings. This contribution focuses on creating the CCT diagram of the investigated powder steel in the range of cooling rates from 100 to 0.01 °C/s. JMatPro® API v7.0 simulation software was used to compare the experimentally measured CCT diagram. The measured dilatation curves were confronted with a microstructural analysis, which was evaluated using a scanning electron microscope (SEM). The M398 material contains a large number of carbide particles that occur in the form of M7C3 and MC and are based on Cr and V. EDS analysis was used to evaluate the distribution of selected chemical elements. A comparison of the surface hardness of all samples in relation to the given cooling rates was also carried out. Subsequently, the nanoindentation properties of the formed individual phases as well as the carbides, where the nanohardness and reduced modulus of elasticity (carbides and matrix) were evaluated. Full article
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15 pages, 11416 KiB  
Article
A Micromechanical Analysis to the Viscoplastic Behavior of Sintered Silver Joints under Shear Loading
by Kun Ma, Xun Liu, Yameng Sun, Yifan Song, Zheng Feng, Yang Zhou and Sheng Liu
Materials 2023, 16(12), 4472; https://doi.org/10.3390/ma16124472 - 19 Jun 2023
Viewed by 1547
Abstract
Ag paste has been recognized as a promising substitute for Sn/Pb solder in SiC or GaN power electronic devices, owing to its ability to withstand high temperatures and facilitate low-temperature packing. The reliability of these high-power circuits is greatly influenced by the mechanical [...] Read more.
Ag paste has been recognized as a promising substitute for Sn/Pb solder in SiC or GaN power electronic devices, owing to its ability to withstand high temperatures and facilitate low-temperature packing. The reliability of these high-power circuits is greatly influenced by the mechanical properties of sintered Ag paste. However, there exist substantial voids inside the sintered silver layer after sintering, and the conventional macroscopic constitutive models have certain limitation to describe the shear stress–strain relationship of sintered silver materials. To analyze the void evolution and microstructure of sintered silver, Ag composite pastes composed of micron flake silver and nano-silver particles were prepared. The mechanical behaviors were studied at different temperatures (0–125 °C) and strain rates (1 × 10−4–1 × 10−2) for Ag composite pastes. The crystal plastic finite element method (CPFEM) was developed to describe the microstructure evolution and shear behaviors of sintered silver at varied strain rates and ambient temperatures. The model parameters were obtained by fitting experimental shear test data to a representative volume element (RVE) model built on representative volume elements, also known as Voronoi tessellations. The numerical predictions were compared with the experimental data, which showed that the introduced crystal plasticity constitutive model can describe the shear constitutive behavior of a sintered silver specimen with reasonable accuracy. Full article
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44 pages, 7544 KiB  
Review
Recent Advances in Molybdenum Disulfide and Its Nanocomposites for Energy Applications: Challenges and Development
by Kamal Batcha Mohamed Ismail, Manoharan Arun Kumar, Shanmugam Mahalingam, Junghwan Kim and Raji Atchudan
Materials 2023, 16(12), 4471; https://doi.org/10.3390/ma16124471 - 19 Jun 2023
Cited by 6 | Viewed by 2644
Abstract
Energy storage and conversion are critical components of modern energy systems, enabling the integration of renewable energy sources and the optimization of energy use. These technologies play a key role in reducing greenhouse gas emissions and promoting sustainable development. Supercapacitors play a vital [...] Read more.
Energy storage and conversion are critical components of modern energy systems, enabling the integration of renewable energy sources and the optimization of energy use. These technologies play a key role in reducing greenhouse gas emissions and promoting sustainable development. Supercapacitors play a vital role in the development of energy storage systems due to their high power density, long life cycles, high stability, low manufacturing cost, fast charging-discharging capability and eco-friendly. Molybdenum disulfide (MoS2) has emerged as a promising material for supercapacitor electrodes due to its high surface area, excellent electrical conductivity, and good stability. Its unique layered structure also allows for efficient ion transport and storage, making it a potential candidate for high-performance energy storage devices. Additionally, research efforts have focused on improving synthesis methods and developing novel device architectures to enhance the performance of MoS2-based devices. This review article on MoS2 and MoS2-based nanocomposites provides a comprehensive overview of the recent advancements in the synthesis, properties, and applications of MoS2 and its nanocomposites in the field of supercapacitors. This article also highlights the challenges and future directions in this rapidly growing field. Full article
(This article belongs to the Special Issue Smart Materials and Devices for Energy Harvesting, Volume II)
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9 pages, 5836 KiB  
Article
Coefficients of Thermal Expansion in La3Ga5SiO14 and Ca3TaGa3Si2O14 Crystals
by Dmitry Roshchupkin and Dmitry Kovalev
Materials 2023, 16(12), 4470; https://doi.org/10.3390/ma16124470 - 19 Jun 2023
Cited by 1 | Viewed by 1236
Abstract
The ordered Ca3TaGa3Si2O14 and disordered La3Ga5SiO14 crystals of the lantangallium silicate family were grown via the Czochralski method. The independent coefficients of thermal expansion of crystals αc and αa [...] Read more.
The ordered Ca3TaGa3Si2O14 and disordered La3Ga5SiO14 crystals of the lantangallium silicate family were grown via the Czochralski method. The independent coefficients of thermal expansion of crystals αc and αa were determined using X-ray powder diffraction based on the analysis of X-ray diffraction spectra measured in the temperature range of 25~1000 °C. It is shown that, in the temperature range of 25~800 °C, the thermal expansion coefficients are linear. At temperatures above 800 °C, there is a nonlinear character of the thermal expansion coefficients, associated with a decrease in the Ga content in the crystal lattice. Full article
(This article belongs to the Special Issue Crystalline Materials: Growth, Characterization, and Devices)
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9 pages, 3996 KiB  
Article
Impact of Charge-Trapping Effects on Reliability Instability in AlxGa1−xN/GaN High-Electron-Mobility Transistors with Various Al Compositions
by Walid Amir, Surajit Chakraborty, Hyuk-Min Kwon and Tae-Woo Kim
Materials 2023, 16(12), 4469; https://doi.org/10.3390/ma16124469 - 19 Jun 2023
Cited by 1 | Viewed by 1459
Abstract
In this study, we present a detailed analysis of trapping characteristics at the AlxGa1−xN/GaN interface of AlxGa1−xN/GaN high-electron-mobility transistors (HEMTs) with reliability assessments, demonstrating how the composition of the Al in the AlxGa [...] Read more.
In this study, we present a detailed analysis of trapping characteristics at the AlxGa1−xN/GaN interface of AlxGa1−xN/GaN high-electron-mobility transistors (HEMTs) with reliability assessments, demonstrating how the composition of the Al in the AlxGa1−xN barrier impacts the performance of the device. Reliability instability assessment in two different AlxGa1−xN/GaN HEMTs [x = 0.25, 0.45] using a single-pulse ID–VD characterization technique revealed higher drain-current degradation (∆ID) with pulse time for Al0.45Ga0.55N/GaN devices which correlates to the fast-transient charge-trapping in the defect sites near the interface of AlxGa1−xN/GaN. Constant voltage stress (CVS) measurement was used to analyze the charge-trapping phenomena of the channel carriers for long-term reliability testing. Al0.45Ga0.55N/GaN devices exhibited higher-threshold voltage shifting (∆VT) caused by stress electric fields, verifying the interfacial deterioration phenomenon. Defect sites near the interface of the AlGaN barrier responded to the stress electric fields and captured channel electrons—resulting in these charging effects that could be partially reversed using recovery voltages. The quantitative extraction of volume trap density (Nt) using 1/f low-frequency noise characterizations unveiled a 40% reduced Nt for the Al0.25Ga0.75N/GaN device, further verifying the higher trapping phenomena in the Al0.45Ga0.55N barrier caused by the rougher Al0.45Ga0.55N/GaN interface. Full article
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21 pages, 3391 KiB  
Article
Mechanical and Chemical Resistance of UV Coating Systems Prepared under Industrial Conditions
by Milena Henke, Barbara Lis and Tomasz Krystofiak
Materials 2023, 16(12), 4468; https://doi.org/10.3390/ma16124468 - 19 Jun 2023
Cited by 3 | Viewed by 1706
Abstract
In the upcoming years, it is expected that more furniture will be built from honeycomb panels due to the growing demand for lightweight, long-lasting furnishings. High-density fiberboard (HDF), previously used in the furniture industry as back walls in box furniture or drawer components, [...] Read more.
In the upcoming years, it is expected that more furniture will be built from honeycomb panels due to the growing demand for lightweight, long-lasting furnishings. High-density fiberboard (HDF), previously used in the furniture industry as back walls in box furniture or drawer components, has become a popular facing material used in the production of honeycomb core panels. Varnishing the facing sheets of lightweight honeycomb core boards with the use of analog printing technology and UV lamps is a challenge for the industry. The aim of this study was to determine the effect of selected varnishing parameters on coating resistance by experimentally testing 48 coating variants. It was found that the interactions between the following variables were crucial in achieving adequate resistance: lamp power, the amounts of varnish applied, and the number of layers. The highest scratch, impact, and abrasion resistance values were observed for samples with optimal curing provided by more layers and maximum curing with 90 W/cm lamps. Based on the pareto chart, a model was generated that predicted the optimal settings for the highest scratch resistance. Resistance to cold liquids made with a colorimeter increases with lamp power. Full article
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17 pages, 6607 KiB  
Article
Fracture Toughness and Fatigue Crack Growth Analyses on a Biomedical Ti-27Nb Alloy under Constant Amplitude Loading Using Extended Finite Element Modelling
by Mohammed Y. Abdellah and Hamzah Alharthi
Materials 2023, 16(12), 4467; https://doi.org/10.3390/ma16124467 - 19 Jun 2023
Cited by 5 | Viewed by 1152
Abstract
The human body normally uses alternative materials such as implants to replace injured or damaged bone. Fatigue fracture is a common and serious type of damage in implant materials. Therefore, a deep understanding and estimation or prediction of such loading modes, which are [...] Read more.
The human body normally uses alternative materials such as implants to replace injured or damaged bone. Fatigue fracture is a common and serious type of damage in implant materials. Therefore, a deep understanding and estimation or prediction of such loading modes, which are influenced by many factors, is of great importance and attractiveness. In this study, the fracture toughness of Ti-27Nb, a well-known implant titanium alloy biomaterial, was simulated using an advanced finite element subroutine. Furthermore, a robust direct cyclic finite element fatigue model based on a fatigue failure criterion derived from Paris’ law is used in conjunction with an advanced finite element model to estimate the initiation of fatigue crack growth in such materials under ambient conditions. The R-curve was fully predicted, yielding a minimum percent error of less than 2% for fracture toughness and less than 5% for fracture separation energy. This provides a valuable technique and data for fracture and fatigue performance of such bio-implant materials. Fatigue crack growth was predicted with a minimum percent difference of less than nine for compact tensile test standard specimens. The shape and mode of material behaviour have a significant effect on the Paris law constant. The fracture modes showed that the crack path is in two directions. The finite element direct cycle fatigue method was recommended to determine the fatigue crack growth of biomaterials. Full article
(This article belongs to the Special Issue Advances in Materials Fracture with Multiscale Modeling)
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14 pages, 8553 KiB  
Article
The Relationship between the Structural Characteristics of α-Fe2O3 Catalysts and Their Lattice Oxygen Reactivity Regarding Hydrogen
by Nadezhda Kirik, Alexander Krylov, Andrey Boronin, Sergey Koshcheev, Leonid Solovyov, Evgenii Rabchevskii, Nina Shishkina and Alexander Anshits
Materials 2023, 16(12), 4466; https://doi.org/10.3390/ma16124466 - 19 Jun 2023
Cited by 3 | Viewed by 1171
Abstract
In this paper, the relationship between the structural features of hematite samples calcined in the interval of 800–1100 °C and their reactivity regarding hydrogen studied in the temperature-programmed reaction (TPR-H2) was studied. The oxygen reactivity of the samples decreases with the [...] Read more.
In this paper, the relationship between the structural features of hematite samples calcined in the interval of 800–1100 °C and their reactivity regarding hydrogen studied in the temperature-programmed reaction (TPR-H2) was studied. The oxygen reactivity of the samples decreases with the increasing calcination temperature. The study of calcined hematite samples used X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM), X-ray Photoelectron Spectroscopy (XPS), and Raman spectroscopy, and their textural characteristics were studied also. According to XRD results, hematite samples calcined in the temperature range under study are monophase, represented by the α-Fe2O3 phase, in which crystal density increases with increasing calcination temperature. The Raman spectroscopy results also register only the α-Fe2O3 phase; the samples consist of large, well-crystallized particles with smaller particles on their surface, having a significantly lower degree of crystallinity, and their proportion decreases with increasing calcination temperature. XPS results show the α-Fe2O3 surface enriched with Fe2+ ions, whose proportion increases with increasing calcination temperature, which leads to an increase in the lattice oxygen binding energy and a decrease in the α-Fe2O3 reactivity regarding hydrogen. Full article
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