Crystals

15 pages, 7660 KiB

Open AccessArticle

Preparation of Titanium Oxycarbide from Ilmenite (FeTiO₃) Concentrate Through Thermal Reduction and Magnetic Separation Processes

by Fuxing Zhu, Bin Deng, Zhipeng Huang, Song Yang, Kaihua Li, Tianzhu Mu and Xueming Lv

Crystals 2025, 15(2), 199; https://doi.org/10.3390/cryst15020199 - 19 Feb 2025

Viewed by 459

Abstract

Ilmenite concentrate has emerged as the key titanium raw material for exploitation and utilization, playing a crucial role in the preparation of metallic titanium and titanium dioxide. However, the presence of impurities such as Fe, Ca, and Mg in ilmenite concentrate severely restricts [...] Read more.

Ilmenite concentrate has emerged as the key titanium raw material for exploitation and utilization, playing a crucial role in the preparation of metallic titanium and titanium dioxide. However, the presence of impurities such as Fe, Ca, and Mg in ilmenite concentrate severely restricts its economic utilization and environmentally friendly applications. In our previous research, a novel process was proposed to prepare TiCl₄ from high-Ca- and Mg-containing ilmenite through carbothermal reduction and boiling chlorination. Nevertheless, the employment of graphite as a reducing agent and hydrochloric acid for metallic iron separation led to elevated production costs. The aim of this study was to explore an alternative and more cost-effective method. Petroleum-derived coke was used as the reducing agent to investigate the feasibility of producing titanium oxycarbide from ilmenite concentrate via carbothermal reduction and magnetic separation. The results showed that petroleum-derived coke is capable of reducing ilmenite concentrate to coral-shaped TiC_xO_y under high-temperature conditions. However, an approximate 100 °C increment in temperature is required to reach an equivalent reduction efficiency compared with graphite. The X-ray diffraction (XRD) analysis results of the reduced products reveal that complete reduction of ilmenite concentrate by petroleum-derived coke can only be achieved when the reduction process is conducted at 1600 °C for 3 h or at 1500 °C for 5 h. The reduced product obtained at 1600 °C, characterized by a substantial presence of dense Ti₂O₃, exhibits a significantly coarser particle size after 30 minutes of ball milling in contrast to the reduced product obtained at 1200 °C, which is rich in M₃O₅ anosovite. Magnetic separation results showed that the reduction product at 1200 °C could not have metallic iron removed by magnetic separation at 1.2 T, while the reduction product at 1600 °C could yield a non-magnetic charge rich in Ti₂O₃ and TiC_xO_y with an iron content as low as 2 ± 0.03 wt.%, which fully meets the requirements for producing TiCl₄ by boiling chlorination. Overall, these research results offer a new approach for the low-cost production of TiCl₄ from ilmenite concentrate with high levels of Ca and Mg impurities through boiling chlorination. Full article

(This article belongs to the Section Polycrystalline Ceramics)

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13 pages, 4469 KiB

Open AccessArticle

Interactions Between Sc₂O₃ Ceramics and Calcium–Magnesium–Alumina–Silicate (CMAS) at Elevated Temperature

by Zupeng Mo, Zijian Mo, Zhiyun Yu, Yifan Cheng, Yiling Miao and Tianquan Liang

Crystals 2025, 15(2), 198; https://doi.org/10.3390/cryst15020198 - 19 Feb 2025

Viewed by 355

Abstract

The thermochemical interactions of Sc₂O₃ ceramics with CMAS at 1250 °C and 1300 °C were investigated in this paper. A continuously dense reaction layer (DRL) forms on the surface of the ceramic at the beginning of the reaction within 15 [...] Read more.

The thermochemical interactions of Sc₂O₃ ceramics with CMAS at 1250 °C and 1300 °C were investigated in this paper. A continuously dense reaction layer (DRL) forms on the surface of the ceramic at the beginning of the reaction within 15 min, and temperature significantly affects the components of the DRL. The DRL is mainly composed of a diopside phase at 1250 °C, whose thickness decreases with reaction time, while it is composed of garnet and minor diopside phases at 1300 °C, and thickens in accordance with the parabolic law with exposure time. The DRL shows good effect on alleviating Mg²⁺ infiltration and some mitigating effect to Al³⁺, and relatively inferior resistance to Ca²⁺ and Si⁴⁺ penetration. The concentration of Sc³⁺ in the residual CMAS increases with reaction temperature and time, and the average contents are about 0.7 at% and 3.7 at% after reactions at 1250 °C and 1300 °C, respectively. The mechanism is discussed systematically. Full article

(This article belongs to the Special Issue Design, Development and Processing of Aluminium Alloys and Their Composite Materials)

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20 pages, 2740 KiB

Open AccessArticle

Thermal Conductivity Modeling for Liquid-Phase-Sintered Silicon Carbide Ceramics Using Machine Learning Computational Methods

by Sami M. Ibn Shamsah

Crystals 2025, 15(2), 197; https://doi.org/10.3390/cryst15020197 - 19 Feb 2025

Viewed by 438

Abstract

Silicon carbide is a covalently bonded engineering material and structural ceramic with excellent mechanical properties, high resistance to oxidation, corrosion, and wear, and tunable thermal conductivity. The exceptional thermal conductivity of silicon carbide ceramic promotes its candidature in many industrial applications, such as [...] Read more.

Silicon carbide is a covalently bonded engineering material and structural ceramic with excellent mechanical properties, high resistance to oxidation, corrosion, and wear, and tunable thermal conductivity. The exceptional thermal conductivity of silicon carbide ceramic promotes its candidature in many industrial applications, such as nuclear fuel capsule materials, substrate materials employed in semiconductor devices, heater plates, and heaters for processing semiconductor and gas seal rings employed in compressor pumps, among others. The synthesis of polycrystalline silicon carbide through the liquid-phase sintering approach results in lower thermal conductivity due to the presence of structural defects associated with grains, lattice impurities, grains’ random orientations, and the presence of secondary phases in polycrystalline silicon carbide ceramic. The conventional experimental method of enhancing thermal conductivity is laborious and expensive. This present work modeled the thermal conductivity of liquid-phase silicon carbide ceramic via intelligent approaches involving genetic algorithm-optimized support vector regression (SVR-GA), an extreme learning machine with a sine activation function (ELMS), and random forest regression (RFR). The descriptors for the models included the nature of sintering additives as well as their weights, sintering conditions, applied pressure, sintering temperature, and time. Using the mean absolute error (MAE) and root mean square error (RMSE) for performance assessment, it was observed that the ELMS outperformed the RFR and SVR-GA models with improvements of 40.50% and 25.76%, respectively, using the MAE metric and improvements of 16.57% and 24.43%, respectively, using the RMSE metric. The developed models were further used to investigate the effect of the weight of sintering additives and sintering time on the thermal conductivity of silicon carbide ceramic. The precision of the developed models facilitated a comprehensive investigation of the effect of sintering factors on thermal conductivity while hidden connections that exist between the factors are uncovered for enhancing application domains for silicon carbide ceramics. Full article

(This article belongs to the Special Issue Precision and Ultra-Precision Machining for Ceramics and Composite Materials)

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18 pages, 18189 KiB

Open AccessArticle

Structural Properties of PE-Based Wood–Plastic Composites Depending on the Share of Lignocellulosic Particles

by Izabela Betlej, Marek Barlak, Sławomir Borysiak, Aneta Bombalska, Barbara Nasiłowska, Ján Sedliačik and Piotr Borysiuk

Crystals 2025, 15(2), 196; https://doi.org/10.3390/cryst15020196 - 18 Feb 2025

Viewed by 433

Abstract

Wood–plastic composites (WPCs) are an excellent example of materials that, thanks to the possibility of using recycled raw materials, directly fit into the circular economy. The properties and quality of composites depend largely on the appropriate selection and proportions of components. These studies [...] Read more.

Wood–plastic composites (WPCs) are an excellent example of materials that, thanks to the possibility of using recycled raw materials, directly fit into the circular economy. The properties and quality of composites depend largely on the appropriate selection and proportions of components. These studies included composites produced on the basis of an HDPE-recycled matrix filled with sawdust or bark particles in the amounts of 40%, 50%, and 60%. Their structural features were analyzed for the produced composites. It was shown that a smaller share of filler ensures its more even distribution in the matrix. In turn, the type of filler affects the crystallinity and thermal transformations of the composite. The use of bark as a filler provides more favorable structural parameters of WPCs. Full article

(This article belongs to the Section Inorganic Crystalline Materials)

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17 pages, 6112 KiB

Open AccessArticle

Adsorption and Decomposition Mechanisms of Vapor Growth Carbon Fiber on SiO₂ in Non-Catalytic Conditions: A First-Principles Study

by Chen Ma, Fanguang Zeng and Shenbo Yang

Crystals 2025, 15(2), 195; https://doi.org/10.3390/cryst15020195 - 18 Feb 2025

Viewed by 387

Abstract

In this study, the authors employed first-principles calculations to investigate the adsorption and decomposition processes involved in non-catalytic growth of vapor-growth carbon fiber (VGCF) using a non-catalytic growth method. The adsorption and decomposition mechanisms of methane and its decomposition products on the substrate [...] Read more.

In this study, the authors employed first-principles calculations to investigate the adsorption and decomposition processes involved in non-catalytic growth of vapor-growth carbon fiber (VGCF) using a non-catalytic growth method. The adsorption and decomposition mechanisms of methane and its decomposition products on the substrate were investigated with the adsorption energy, transition state analysis, and projected density of states (PDOS). The results indicated that the surface adsorption difficulty for CH₄ and its decomposition products followed the following order: H > CH₄ ≈ CH₃ > CH₂ > CH > C. The adsorption energy analysis indicates that the adsorption of CH₄, CH₃, and H is classified as physical adsorption, whereas the adsorption of CH₂, CH, and C is classified as chemical adsorption. Adsorption of all particles is exothermic and adsorption can occur. The transition state calculations indicate that the decomposition of CH₄ is the rate-determining step in the decomposition reaction. PDOS analysis not only verified the results of adsorption energy analysis but also investigated the effect of adsorption particles. This work is helpful for advancing the application of non-catalytic growth processes to the synthesis of VGCF and enhancing the understanding of the mechanisms governing non-catalytic VGCF formation. Full article

(This article belongs to the Section Inorganic Crystalline Materials)

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2 pages, 535 KiB

Open AccessCorrection

Correction: Zou et al. Crystal Growth, Photoluminescence and Radioluminescence Properties of Ce³⁺-Doped Ba₃Y(PO₄)₃ Crystal. Crystals 2024, 14, 431

by Zhenggang Zou, Jiaolin Weng, Chun Liu, Yiyang Lin, Jiawei Zhu, Yijian Sun, Jianhui Huang, Guoliang Gong and Herui Wen

Crystals 2025, 15(2), 194; https://doi.org/10.3390/cryst15020194 - 18 Feb 2025

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Abstract

The original version of the manuscript [...] Full article

(This article belongs to the Section Crystal Engineering)

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15 pages, 3184 KiB

Open AccessArticle

Kinetics of Reduction of Iron Ore Powder by Industrial Lignin from Pulping and Papermaking Waste Biomass Energy

by Wendi Zhou, Dongwen Xiang, Qiang Zhang, Guoqing Wu, Yajie Wang, Dong Li, Qinghua Zhang and Huaxin Hu

Crystals 2025, 15(2), 193; https://doi.org/10.3390/cryst15020193 - 17 Feb 2025

Viewed by 332

Abstract

To explore the application of industrial lignin, a waste biomass resource, in the field of metallurgy, the kinetic behavior of iron ore powder reduction by Shenmu bituminous coal, Lu’an anthracite, and industrial lignin under different carbon–oxygen molar ratios (n_c:n [...] Read more.

To explore the application of industrial lignin, a waste biomass resource, in the field of metallurgy, the kinetic behavior of iron ore powder reduction by Shenmu bituminous coal, Lu’an anthracite, and industrial lignin under different carbon–oxygen molar ratios (n_c:n_o = 0.5, 0.7, 1.0, 1.2, and 1.5) was studied using a thermogravimetric analyzer and reduction furnace. The results show that the reduction process of iron ore powder with three reducing agents conforms to the D1 model, that is, the kinetic equation is

G (α) = α^{2}

. Under the same carbon–oxygen molar ratio, the activation energy of the iron ore powder reduced by industrial lignin is lower than that of pulverized coal. The activation energy increases first, then decreases and then increases with the increase in the carbon–oxygen molar ratio. When the molar ratio of carbon to oxygen is 1.2, the reaction activation energy is the lowest. At this time, the reaction activation energy of industrial lignin reduction iron ore powder is 14.21 kJ·mol⁻¹, that of Shenmu bituminous coal is 16.81 kJ·mol⁻¹, and that of Lu’an anthracite is 37.13 kJ·mol⁻¹. Full article

(This article belongs to the Section Crystalline Metals and Alloys)

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57 pages, 13524 KiB

Open AccessReview

Recent Developments in Transmission Electron Microscopy for Crystallographic Characterization of Strained Semiconductor Heterostructures

by Tao Gong, Longqing Chen, Xiaoyi Wang, Yang Qiu, Huiyun Liu, Zixing Yang and Thomas Walther

Crystals 2025, 15(2), 192; https://doi.org/10.3390/cryst15020192 - 17 Feb 2025

Viewed by 909

Abstract

With recent electronic devices relying on sub-nanometer features, the understanding of device performance requires a direct probe of the atomic arrangement. As an ideal tool for crystallographic analysis at the nanoscale, aberration-corrected transmission electron microscopy (ACTEM) has the ability to provide atomically resolved [...] Read more.

With recent electronic devices relying on sub-nanometer features, the understanding of device performance requires a direct probe of the atomic arrangement. As an ideal tool for crystallographic analysis at the nanoscale, aberration-corrected transmission electron microscopy (ACTEM) has the ability to provide atomically resolved images and core-loss spectra. Herein, the techniques for crystallographic structure analysis based on ACTEM are reviewed and discussed, particularly ACTEM techniques for measuring strain, dislocations, phase transition, and lattice in-plane misorientation. In situ observations of crystal evolution during the application of external forces or electrical fields are also introduced, so a correlation between crystal quality and device performance can be obtained. Full article

(This article belongs to the Section Inorganic Crystalline Materials)

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24 pages, 24136 KiB

Open AccessReview

Innovation in Metal Casting Processes: A Review of Metal Matrix Nanocomposites in Metal and Bimetal Castings

by Tayyab Subhani, Mohamed Ramadan, Naglaa Fathy, Abdel Khaliq and K. S. Abdel Halim

Crystals 2025, 15(2), 191; https://doi.org/10.3390/cryst15020191 - 17 Feb 2025

Viewed by 549

Abstract

The arrival of nanotechnology in the field of metal castings is considered a promising approach to significantly improve the quality, performance and lifetime of castings. A better understanding of the implementation of nanotechnology in the metal casting process and its dynamics is essential [...] Read more.

The arrival of nanotechnology in the field of metal castings is considered a promising approach to significantly improve the quality, performance and lifetime of castings. A better understanding of the implementation of nanotechnology in the metal casting process and its dynamics is essential for the successful production of metal matrix nanocomposite castings. This review focuses on past and present techniques for metal matrix nanocomposite castings to facilitate future fabrication processes and improve the performance of casting products. The advantages, limitations, difficulties and optimal processing conditions of nanocomposite castings are presented and thoroughly discussed. Both types of metal matrix nanocomposites (i.e., ferrous and nonferrous metallic matrices, are discussed in the present review), as well as nanocomposites in the working surface layer and interlayer of bimetallic materials. Significant improvements in the surface microstructure and shear strength of bimetallic bearings are achieved using nanoparticles as additions to the surface working layer and interlayer areas. Special emphasis is given to the factors affecting these fabrication processes in achieving high-quality products. The dispersion of nanoparticles in the metallic matrix is another critical issue, which is discussed comprehensively. Moreover, the strengthening mechanisms that evolve due to the incorporation of nanoparticles in the metallic matrices, which deserve separate attention, are discussed. The economic and political factors that simultaneously lead to evolutionary and drastic changes in metal matrix nanocomposite castings are also considered. Finally, the present article indicates future fabrication routes and describes the development of metal matrix nanocomposite castings under the influence of nanotechnology after incorporating the novel casting opportunities presented by nanotechnology. Full article

(This article belongs to the Section Crystalline Metals and Alloys)

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14 pages, 30887 KiB

Open AccessArticle

Mechanisms and Applications of Impurity-Driven Surface Modification in Magnesium Sulfate Crystallization

by Minhang Yang, Huaigang Cheng, Jing Zhao and Wenting Cheng

Crystals 2025, 15(2), 190; https://doi.org/10.3390/cryst15020190 - 17 Feb 2025

Viewed by 368

Abstract

Impurities significantly constrain the production of high-purity magnesium sulfate crystals, essential for advanced magnesium-based materials. Sodium–magnesium co-precipitation affects the crystals’ purity and surface smoothness, with NaCl embedding into crystal surfaces during cooling crystallization in the MgSO₄-NaCl-H₂O system. Trace impurities, [...] Read more.

Impurities significantly constrain the production of high-purity magnesium sulfate crystals, essential for advanced magnesium-based materials. Sodium–magnesium co-precipitation affects the crystals’ purity and surface smoothness, with NaCl embedding into crystal surfaces during cooling crystallization in the MgSO₄-NaCl-H₂O system. Trace impurities, however, inhibit NaCl adhesion, alter SO₄²⁻ coordination structures, and enhance the purity and morphology of MgSO₄·6H₂O crystals. Adding 300 mmol/L K₂SO₄ reduces sodium content in crystals from 0.57% to 0.03% and surface roughness from 2.76 nm to 0.415 nm. The binding energies of Na⁺ on MgSO₄·6H₂O crystal planes are lower than those of impurity ions, which compete for active growth sites and prevent Na⁺ nucleation. This finding challenges the assumption that higher-purity solutions yield higher-purity crystals. Full article

(This article belongs to the Section Inorganic Crystalline Materials)

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15 pages, 7828 KiB

Open AccessArticle

The Effect of Carbon on the Crystallization and Electrochemical Behavior of Portland Cement

by Jeunghyeuon Cho, Byung-Hyun Shin, Miyoung You, Seongjun Kim, Jinyong Park, Jung-Woo Ok, Jonggi Hong, Taekyu Lee, Jong-Seong Bae, Pungkeun Song and Jang-Hee Yoon

Crystals 2025, 15(2), 189; https://doi.org/10.3390/cryst15020189 - 17 Feb 2025

Cited by 1 | Viewed by 423

Abstract

Cement is one of the most widely used structural materials and serves as the primary component of concrete. Among the various types, Portland cement is the most commonly utilized due to its excellent strength and corrosion resistance. Recently, efforts have been made to [...] Read more.

Cement is one of the most widely used structural materials and serves as the primary component of concrete. Among the various types, Portland cement is the most commonly utilized due to its excellent strength and corrosion resistance. Recently, efforts have been made to incorporate various functional additives into Portland cement to impart new properties; however, studies on the resulting changes in corrosion resistance remain insufficient. While the existing research has largely focused on impurities in cement, systematic studies on the effects of interstitial elements on the crystallization and electrochemical behavior of cement are scarce. This study investigates the influence of carbon (C) addition on the crystallographic structure and electrochemical properties of Portland cement. C concentrations from 0 to 10 wt.% were added. The microstructure and crystallographic structure with different C concentrations were analyzed using FE-SEM and XRD. The bonding characteristics of cement components according to the C composition were measured using XPS, hardness was measured using Vickers hardness, and electroconductivity was calculated using a 4-point probe. The electrochemical behavior was evaluated according to the ASTM G 61 standards through OCP, EIS, and potentiodynamic polarization tests. As the composition of C increased, the number of voids and cracks decreased, while the electrical conductivity increased from 1.7 × 10⁻⁴ to 4.3 × 10⁻². Additionally, the resistance tended to decrease with the increase in C composition. Therefore, the concentration of C needs to be controlled depending on the required function of the cement. Full article

(This article belongs to the Special Issue Crystallization Process and Simulation Calculation, Third Edition)

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20 pages, 552 KiB

Open AccessArticle

On Modeling X-Ray Diffraction Intensity Using Heavy-Tailed Probability Distributions: A Comparative Study

by Farouq Mohammad A. Alam

Crystals 2025, 15(2), 188; https://doi.org/10.3390/cryst15020188 - 16 Feb 2025

Viewed by 486

Abstract

Crystallography, a cornerstone of materials science, provides critical insights into material structures through techniques such as X-ray diffraction (XRD). Among the metrics derived from XRD, intensity serves as a key parameter, reflecting the electron density distribution and offering information about atomic arrangements and [...] Read more.

Crystallography, a cornerstone of materials science, provides critical insights into material structures through techniques such as X-ray diffraction (XRD). Among the metrics derived from XRD, intensity serves as a key parameter, reflecting the electron density distribution and offering information about atomic arrangements and sample quality. Due to its inherent variability and susceptibility to extreme values, intensity is best modeled using heavy-tailed, location-scale probability distributions. This paper investigates the model parameter estimation problem for three such distributions—log-Cauchy, half-Cauchy, and Cauchy Birnbaum–Saunders—using several methods, including maximum likelihood and the maximum product of spacings estimation methods. Monte Carlo simulations are conducted to assess the performance of these methods across various scenarios. Additionally, two real XRD intensity datasets are analyzed to compare the applicability and effectiveness of the proposed models. The results demonstrate the potential of heavy-tailed distributions for modeling XRD intensity data, providing a robust framework for future research and practical applications in material characterization. Full article

(This article belongs to the Special Issue Advances in Processing, Simulation and Characterization of Alloys)

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17 pages, 5708 KiB

Open AccessArticle

Boosting the Optical Activity of Titanium Oxide Through Conversion from Nanoplates to Nanotubes and Nanoparticle-Supported Nanolayers

by Adil Alshoaibi

Crystals 2025, 15(2), 187; https://doi.org/10.3390/cryst15020187 - 16 Feb 2025

Viewed by 460

Abstract

The nano-architecture of titanium oxide is a key element of a wide range of applications, mainly optical and catalytic activities. Therefore, the current study focuses on engineering and designing three interesting nanostructures of titanium oxides: nanoplates, nanotubes, and nanoparticle-supported nanolayers. The nanoplates of [...] Read more.

The nano-architecture of titanium oxide is a key element of a wide range of applications, mainly optical and catalytic activities. Therefore, the current study focuses on engineering and designing three interesting nanostructures of titanium oxides: nanoplates, nanotubes, and nanoparticle-supported nanolayers. The nanoplates of titanium oxides were prepared and confirmed by TEM images, X-ray diffraction, and EDX analysis. These nanoplates have an anatase phase, with the distance across the corners in the range of 15 nm. These nanoplates were modified and developed through a rolling process with sodium doping to generate the Na-doped TiO₂ nanotubes. These nanotubes were observed by TEM images and X-ray diffraction. In addition, the doping process of titanium oxides with sodium was confirmed by EDX analysis. A novel nano-architecture of titanium oxide was designed by supporting titanium oxide nanoparticles over Zn/Al nanolayers. The optical properties and activity of titanium oxides with the different morphologies indicated that titanium oxides became a highly photo-active photocatalyst after conversion to nanotubes. This finding was observed through the reduction in the band gap energy to 2.7 eV. Additionally, after 37 min of exposure to UV light, the titanium oxide nanotubes totally broke down and transformed the green dye of NGB into carbon dioxide and water. Furthermore, the kinetic analysis verified that the green dyes’ degradation was expedited by the high activity of nanotubes. Ultimately, based on these findings, it was possible to design an efficient photocatalyst for water purification by converting nanoplates into nanotubes, doping titanium sites with sodium ions, and creating new active sites for titanium oxides through defect-induced super radical formation. Full article

(This article belongs to the Special Issue Synthesis and Characterization of Oxide Nanoparticles)

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24 pages, 6808 KiB

Open AccessArticle

Single-Particle Radiation Sensitivity of Ultrawide-Bandgap Semiconductors to Terrestrial Atmospheric Neutrons

by Daniela Munteanu and Jean-Luc Autran

Crystals 2025, 15(2), 186; https://doi.org/10.3390/cryst15020186 - 15 Feb 2025

Viewed by 388

Abstract

Semiconductors characterized by ultrawide bandgaps (UWBGs), exceeding the SiC bandgap of 3.2 eV and the GaN bandgap of 3.4 eV, are currently under focus for applications in high-power and radio-frequency (RF) electronics, as well as in deep-ultraviolet optoelectronics and extreme environmental conditions. These [...] Read more.

Semiconductors characterized by ultrawide bandgaps (UWBGs), exceeding the SiC bandgap of 3.2 eV and the GaN bandgap of 3.4 eV, are currently under focus for applications in high-power and radio-frequency (RF) electronics, as well as in deep-ultraviolet optoelectronics and extreme environmental conditions. These semiconductors offer numerous advantages, such as a high breakdown field, exceptional thermal stability, and minimized power losses. This study used numerical simulation to investigate, at the material level, the single-particle radiation response of various UWBG semiconductors, such as aluminum gallium nitride alloys (Al_xGa_1−xN), diamond, and β-phase gallium oxide (β-Ga₂O₃), when exposed to ground-level neutrons. Through comprehensive Geant4 simulations covering the entire spectrum of atmospheric neutrons at sea level, this study provides an accurate comparison of the neutron radiation responses of these UWBG semiconductors focusing on the interaction processes, the number and nature of secondary ionizing products, their energy distributions, and the production of electron–hole pairs at the origin of single-event effects (SEEs) in microelectronics devices. Full article

(This article belongs to the Special Issue Crystalline Materials for Radiation Detection: A New Perspective (2nd Edition))

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15 pages, 2427 KiB

Open AccessArticle

Effects of Beam Center Position Shifts on Data Processing in Serial Crystallography

by Ki Hyun Nam

Crystals 2025, 15(2), 185; https://doi.org/10.3390/cryst15020185 - 15 Feb 2025

Viewed by 394

Abstract

Serial crystallography (SX) enables the determination of biologically relevant structures at room temperature while minimizing radiation damage. During SX experiments, the beam center on diffraction images can shift due to X-ray beam movements or detector displacement. Consequently, the geometry file for the beam [...] Read more.

Serial crystallography (SX) enables the determination of biologically relevant structures at room temperature while minimizing radiation damage. During SX experiments, the beam center on diffraction images can shift due to X-ray beam movements or detector displacement. Consequently, the geometry file for the beam center is optimized; however, the effects of deviations from the optimal position on data processing efficiency remain unclear. This study examines how changes in the beam center influence data quality by analyzing the indexing efficiency and structure refinement of lysozyme and glucose isomerase datasets, considering shifts in the beam center parameter. The results revealed that as the beam center deviated farther from its optimal position, the indexing efficiency declined, with the extent of the effect varying significantly across indexing algorithms. XDS and MOSFLM algorithms maintained high indexing efficiencies (>90%) for shifts of ≤4 pixels (688 μm) and ≤2 pixels (344 μm), respectively, compared to data processed at the optimized beam center. Conversely, the DirAx and XGANDALF algorithms exhibited indexing efficiencies below 90% for a two-pixel shift in the beam center. These findings enhance our understanding of how beam center shifts affect SX data processing and provide valuable insights for developing effective data processing strategies. Full article

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22 pages, 6031 KiB

Open AccessArticle

Investigation of the Electrical Properties of Polycrystalline Crednerite CuMn_1−xMg_xO₂ (x = 0–0.06)-Type Materials in a Low-Frequency Field

by Iosif Malaescu, Maria Poienar and Catalin N. Marin

Crystals 2025, 15(2), 184; https://doi.org/10.3390/cryst15020184 - 14 Feb 2025

Viewed by 491

Abstract

CuMn_1−xMg_xO₂ (x = 0–0.06) polycrystalline samples were prepared using the hydrothermal method at T = 100 °C for 24 h in Teflon-line stainless steel autoclaves. The samples were crystallized, forming crednerite structures (C2/m space group), and the Mg [...] Read more.

CuMn_1−xMg_xO₂ (x = 0–0.06) polycrystalline samples were prepared using the hydrothermal method at T = 100 °C for 24 h in Teflon-line stainless steel autoclaves. The samples were crystallized, forming crednerite structures (C2/m space group), and the Mg²⁺ substitution onto the Mn³⁺ site induced small changes in the unit cell parameters and volume. Based on complex impedance measurements made between 20 Hz and 2 MHz, at different concentrations of Mg ions (x), the electrical conductivity (σ), the electric modulus (M), and the complex dielectric permittivity (ε) were determined. The conductivity spectrum, σ(f, x), follows the Jonscher universal law and enables the determination of the static conductivity (σ_DC) of the samples. The results showed that, when increasing the concentration x from 0 to 6%, σ_DC varied from 15.36 × 10⁻⁵ S/m to 16.42 × 10⁻⁵ S/m, with a minimum of 4.85 × 10⁻⁵ S/m found at a concentration of x = 4%. Using variable range hopping (VRH) and correlated barrier hopping (CBH) theoretical models, the electrical mechanism in the samples was explained. The band gap energy (W_m), charge carrier mobility (μ), number density (N_C) of effective charge carriers, and hopping frequency (ω_h) were evaluated at different concentrations (x) of substitution with Mg. In addition, using measurements of the temperature dependence of σ_DC(T) between 300 and 400 K, the thermal activation energy (E_A) of the samples was evaluated. Additionally, the dielectric behavior of the samples was explained by the interfacial relaxation process. This knowledge of the electrical properties of the CuMn_1−xMgxO₂ (x = 0–0.06) polycrystalline crednerite is of interest for their use in photocatalytic, electronic, or other applications. Full article

(This article belongs to the Section Inorganic Crystalline Materials)

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20 pages, 4387 KiB

Open AccessArticle

Polymorphism of the Transition Metal Oxidotellurates NiTeO₄ and CuTe₂O₅

by Matthias Weil and Enrique J. Baran

Crystals 2025, 15(2), 183; https://doi.org/10.3390/cryst15020183 - 14 Feb 2025

Viewed by 457

Abstract

As part of crystal growth experiments on transition metal oxidotellurates using chemical vapor transport reactions or hydrothermal conditions, single crystals of Ni^IITe^VIO₄ and Cu^IITe^IV₂O₅ were obtained for the first time in the [...] Read more.

As part of crystal growth experiments on transition metal oxidotellurates using chemical vapor transport reactions or hydrothermal conditions, single crystals of Ni^IITe^VIO₄ and Cu^IITe^IV₂O₅ were obtained for the first time in the form of new modifications, as revealed by crystal structure determinations from X-ray data. In the course of these investigations, the crystal structure model of the only phase of Ni^IITe^VIO₄ reported so far (from now on named α-) was corrected. Both α-(space group P2₁/c, Z = 2) and the new β-polymorph of Ni^IITe^VIO₄ (space group I4₁/a, Z = 8) can be considered derivatives (hettotypes) of the rutile structure (aristotype), as shown by detailed symmetry relationships. For CuTe₂O₅ also, only one crystalline phase has been described so far (from now on named α-) that corresponds to the mineral rajite (space group P2₁/c, Z = 2). Its anion comprises two different trigonal-pyramidal TeO₃ groups linked through corner-sharing into a ditellurite unit. The anion part of the new β-CuTe₂O₅ modification (space group P2₁/c, Z = 2), likewise, comprises two Te^IV atoms but is more complex. Here, one Te^IV atom exhibits a coordination number of 4 and is part of a

{}_{\propto}^{1}[

TeO_2/2O_2/1] chain, and the other has a coordination number of 5 and is part of a

{}_{\propto}^{1}[

TeO_2/2O_3/1]₂ dimer. The two types of anions are linked into a tri-periodic framework where both Te^IV atoms are stereochemically active. The α- and β-CuTe₂O₅ modifications show no closer structural relationship, which is also reflected in their clearly different Raman spectra. Data mining for knowledge discovery in a structure database reveals that polymorphism is a rather common phenomenon for the family of inorganic oxidotellurates. Full article

(This article belongs to the Special Issue Crystalline Materials: Polymorphism)

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24 pages, 8456 KiB

Open AccessReview

Two-Dimensional Metal–Organic Framework Nanostructures and Their Composites in Chemical Warfare Agent Detoxification: A Review

by Cheng-an Tao, Shiyin Zhao, Yujiao Li and Jianfang Wang

Crystals 2025, 15(2), 182; https://doi.org/10.3390/cryst15020182 - 13 Feb 2025

Cited by 1 | Viewed by 901

Abstract

This review summarizes the application of two-dimensional metal–organic framework (2D MOF) nanostructures and their composites in the detoxification of chemical warfare agents (CWAs). Two-dimensional MOFs, characterized by their high specific surface area, abundant active sites, and structural tunability, exhibit promising catalytic performance in [...] Read more.

This review summarizes the application of two-dimensional metal–organic framework (2D MOF) nanostructures and their composites in the detoxification of chemical warfare agents (CWAs). Two-dimensional MOFs, characterized by their high specific surface area, abundant active sites, and structural tunability, exhibit promising catalytic performance in CWA detoxification. Various preparation methods, including top–down exfoliation and bottom–up assembly, are discussed for the synthesis of 2D MOF nanosheets. The catalytic performance of 2D MOFs and their composites in detoxifying CWAs is evaluated, highlighting their advantages in terms of reaction kinetics and ease of recycling. Additionally, the advances and challenges in this field are discussed, aiming to promote further research into and development of 2D MOF-based materials for CWA detoxification. Full article

(This article belongs to the Section Hybrid and Composite Crystalline Materials)

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24 pages, 5102 KiB

Open AccessArticle

The Application of an Abaqus Preprocessor Based on Python Language in a DAHC Negative Poisson Ratio Structure

by Xiaoting Sun, Guibo Yu, Xiujie Zhu, Jinli Che, Yuanyuan Yan and Wei Wang

Crystals 2025, 15(2), 181; https://doi.org/10.3390/cryst15020181 - 13 Feb 2025

Viewed by 529

Abstract

The double-arrow hollow cylinder (DAHC) has excellent mechanical properties under axial compression loads due to its negative Poisson ratio structure. To improve finite element simulation efficiency for parameter optimization analysis, an automatic modeling program for DAHC negative Poisson ratio structures was developed on [...] Read more.

The double-arrow hollow cylinder (DAHC) has excellent mechanical properties under axial compression loads due to its negative Poisson ratio structure. To improve finite element simulation efficiency for parameter optimization analysis, an automatic modeling program for DAHC negative Poisson ratio structures was developed on the ABAQUS platform using Python. The sample was manufactured using selective laser melting additive manufacturing based on the solid model and then simulated using the finite element method. The accuracy of the automatic modeling method was confirmed by comparing load–displacement curves and deformation cloud images with static compression test results. The DAHC automatic modeling program based on Python can reduce workload during parameter optimization analysis and improve finite element analysis efficiency. Full article

(This article belongs to the Section Inorganic Crystalline Materials)

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16 pages, 4320 KiB

Open AccessArticle

Low-Cost Foamed Ceramics with Enhanced Mechanical Performance and Uniform Pore Size Structure

by Junchi Weng, Xiulin Shen, Yixian Yang, Xuejia Zhang, Mengke Fan, Ge Gao, Zeming Guo, Zhenfei Lv and Xiujuan Feng

Crystals 2025, 15(2), 180; https://doi.org/10.3390/cryst15020180 - 13 Feb 2025

Viewed by 486

Abstract

Due to the lack of effective utilization, fly ash and red mud accumulate in large quantities and cause serious harm to the environment. In this experiment, a low-cost preparation of foamed ceramics was realized by applying the foaming agent addition method using fly [...] Read more.

Due to the lack of effective utilization, fly ash and red mud accumulate in large quantities and cause serious harm to the environment. In this experiment, a low-cost preparation of foamed ceramics was realized by applying the foaming agent addition method using fly ash and red mud. The results indicated that temperature and foaming agent content significantly affected the macrostructure, microstructure, crystalline phases, and properties of the foamed ceramics. Specifically, a formulation comprising 45 wt.% fly ash, 45 wt.% red mud, 10 wt.% clay, and 1 wt.% SiC (addition), sintered at 1210 °C, yielded a compressive strength of 8.2 MPa, a bulk density of 1.17 g/cm³, a water absorption rate of 32.05%, and an apparent porosity of 37.59%. The as-prepared materials demonstrate potential as cost-effective building materials, putting forward an effective approach for the high-value utilization of fly ash and red mud. Full article

(This article belongs to the Special Issue Structure and Properties of Ceramic Materials)

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14 pages, 9863 KiB

Open AccessArticle

Crystal Morphology of Antarctic Micrometeorites Based on Melting–Cooling Processes During Atmospheric Entry

by Taki Sönmez and Namık Aysal

Crystals 2025, 15(2), 179; https://doi.org/10.3390/cryst15020179 - 13 Feb 2025

Viewed by 401

Abstract

Micrometeorites (MMs), which are cosmic dust grains ranging from 10 microns to 2 mm in size, can reach the Earth’s surface through collisions with asteroids or by fragmentation of comets in space. When MMs enter the atmosphere, they are heated to varying degrees [...] Read more.

Micrometeorites (MMs), which are cosmic dust grains ranging from 10 microns to 2 mm in size, can reach the Earth’s surface through collisions with asteroids or by fragmentation of comets in space. When MMs enter the atmosphere, they are heated to varying degrees depending on their size, mass, speed, and angle of entry. As a result of friction during atmospheric entry, MMs undergo partial melting and subsequently recrystallize during undercooling. In this study, we focused on molten micrometeorites and identified four main types: silicate, glassy, ferruginous, and intermediate forms. The mineralogical compositions of MMs were determined using Raman spectroscopy, while their chemical compositions and phase changes were analyzed using SEM-EDX and LA-ICP-MS methods. The primary silicate phases include olivine, pyroxene, and plagioclase, whereas the opaque mineral phases comprise magnetite, troilite, and kamacite (Fe-Ni alloys). Olivine exhibits Fo values ranging from 41 to 96 mol%, and the pyroxenes consist of enstatite and pigeonite compositions (Wo_3–8En_79–97Fs_2–19). Olivine and magnetite display dendritic and skeletal crystal morphologies due to melting and undercooling during atmospheric entry. Full article

(This article belongs to the Special Issue Solidification and Crystallization of Inorganic Materials)

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9 pages, 5868 KiB

Open AccessArticle

A Novel Method to Determine Deformation Strain in a High-Temperature Mushy Zone for a Typical Electrical Strip Under Twin-Roll Strip Casting

by Wenli Hu, Yali Hou, Jianhui Shi, Jinhua Zhao and Lifeng Ma

Crystals 2025, 15(2), 178; https://doi.org/10.3390/cryst15020178 - 13 Feb 2025

Cited by 1 | Viewed by 406

Abstract

An evaluation method was proposed to calculate the deformation strain of a high-temperature mushy zone (HTMZ) related to twin-roll strip casting (TSC) with regard to typical 6.5 wt.% Si electrical steel (6.5 Si steel) on the basis of the crystal—plasticity theory. The viscoplasticity [...] Read more.

An evaluation method was proposed to calculate the deformation strain of a high-temperature mushy zone (HTMZ) related to twin-roll strip casting (TSC) with regard to typical 6.5 wt.% Si electrical steel (6.5 Si steel) on the basis of the crystal—plasticity theory. The viscoplasticity self-consistent (VPSC) model was applied to calculate the evolution discipline of crystallographic orientation (CRO) for the studied 6.5 Si steel processed by different deformation strains under a deformation mode of plane strain, and the deformation strain of HTMZ for the studied 6.5 Si steel related to TSC was further estimated by comparing the CRO feature achieved by theoretical calculation and experimental characterization. Results indicate that the distribution feature of CRO obtained by theoretical calculation becomes increasingly similar to those obtained through experimental characterization with the deformation strains increasing from 0 to 1.5. The ratio between the distribution intensities corresponding to R-Cube texture, the typical rolling texture of α-fiber, and the Cube texture achieved by theoretical calculation is the closest to the value obtained by experimental characterization at deformation strain of 1.4, and the deformation strain of HTMZ for the studied 6.5 Si steel involved in TSC is determined to be ~1.4. Full article

(This article belongs to the Section Crystalline Metals and Alloys)

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15 pages, 9424 KiB

Open AccessArticle

Liquid Crystalline Structures Formed by Sphere–Rod Amphiphilic Molecules in Solvents

by Nilanthi P. Haputhanthrige, Yifan Zhou, Jingfan Wei, Min Gao, Tianbo Liu and Oleg D. Lavrentovich

Crystals 2025, 15(2), 177; https://doi.org/10.3390/cryst15020177 - 13 Feb 2025

Viewed by 594

Abstract

Self-assembly of amphiphilic molecules is an important phenomenon attracting a broad range of research. In this work, we study the self-assembly of KTOF₄ sphere–rod amphiphilic molecules in mixed water–dioxane solvents. The molecules are of a T-shaped geometry, comprised of a hydrophilic spherical [...] Read more.

Self-assembly of amphiphilic molecules is an important phenomenon attracting a broad range of research. In this work, we study the self-assembly of KTOF₄ sphere–rod amphiphilic molecules in mixed water–dioxane solvents. The molecules are of a T-shaped geometry, comprised of a hydrophilic spherical Keggin-type cluster attached by a flexible bridge to the center of a hydrophobic rod-like oligodialkylfluorene (OF), which consists of four OF units. Transmission electron microscopy (TEM) uncovers self-assembled spherical structures of KTOF₄ in dilute solutions. These spheres are filled with smectic-like layers of KTOF₄ separated by layers of the solution. There are two types of layer packings: (i) concentric spheres and (ii) flat layers. The concentric spheres form when the dioxane volume fraction in the solution is 35–50 vol%. The flat layers are formed when the dioxane volume fraction is either below (20 and 30 vol%.) or above (55 and 60 vol%.) the indicated range. The layered structures show no in-plane orientational order and thus resemble thermotropic smectic A liquid crystals and their lyotropic analogs. The layered packings reveal edge and screw dislocations. Evaporation of the solvent produces a bulk birefringent liquid crystal phase with textures resembling the ones of uniaxial nematic liquid crystals. These findings demonstrate that sphere–rod molecules produce a variety of self-assembled structures that are controlled by the solvent properties. Full article

(This article belongs to the Special Issue Liquid Crystal Research and Novel Applications in the 21st Century)

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16 pages, 6263 KiB

Open AccessArticle

Stabilizing Perovskite Solar Cells by Methyltriphenylphosphonium Iodide Studied with Maximum Power Point Tracking

by Niklas Manikowsky, Zekarias Teklu Gebremichael, Chikezie Williams Ugokwe, Bashudev Bhandari, Steffi Stumpf, Ulrich S. Schubert and Harald Hoppe

Crystals 2025, 15(2), 176; https://doi.org/10.3390/cryst15020176 - 13 Feb 2025

Viewed by 638

Abstract

The use of organic halide salts to passivate metal halide perovskite (MHP) surface defects has been studied extensively. Passivating the surface defects of the MHP is of critical importance for realizing highly efficient and stable perovskite solar cells (PSCs). Here, the successful application [...] Read more.

The use of organic halide salts to passivate metal halide perovskite (MHP) surface defects has been studied extensively. Passivating the surface defects of the MHP is of critical importance for realizing highly efficient and stable perovskite solar cells (PSCs). Here, the successful application of a multifunctional organic salt, methyltriphenylphosphonium iodide (MTPPI), used as a passivation additive for grain boundary defects and as a molecular sealing layer in terms of stabilization, has been used to stabilize the mixed cation perovskite RbCsMAFA-PbIBr. To assess the passivating and stabilizing effects of MTPPI on RbCsMAFA-PbIBr PSCs, maximum power point tracking (MPPT) was applied as the most realistic and closest-to-application condition for the ageing test. Here, perovskite solar cells were aged under a light source yielding an excitation intensity corresponding to one sun with maximum power point tracking, which was interrupted periodically by current–voltage sweeps. This allowed for the extraction of all photovoltaic parameters necessary for a proper understanding of the ageing process. The MTPPI additive can donate iodine anions to halide vacancies and compensate a negative surface excess charge with cation interactions. On top of this, the large and bulky methyltriphenylphosphonium (MTPP⁺) cation may block both the escape of volatile perovskite components and the ingress of oxygen and water vapour. These collective roles of MTPPI have improved both the efficiency and stability of the solar cells compared to the reference without passivation additives. Full article

(This article belongs to the Special Issue Preparation and Characterization of Optoelectronic Functional Films)

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15 pages, 4260 KiB

Open AccessArticle

Comparison of Ultrasonic Nonlinear Beamforming Algorithms for Defect Imaging in Crystalline Particle-Filled Explosives

by Lida Yu and Haining Li

Crystals 2025, 15(2), 175; https://doi.org/10.3390/cryst15020175 - 12 Feb 2025

Viewed by 460

Abstract

Ultrasonic imaging methods show significant advantages in detecting internal defects of composite crystalline materials. For polymer-bonded explosives (PBXs) with highly filled crystalline particles, the strong acoustic attenuation caused by their heterogeneous crystalline structure leads to low signal-to-noise ratios (SNRs) in the full matrix [...] Read more.

Ultrasonic imaging methods show significant advantages in detecting internal defects of composite crystalline materials. For polymer-bonded explosives (PBXs) with highly filled crystalline particles, the strong acoustic attenuation caused by their heterogeneous crystalline structure leads to low signal-to-noise ratios (SNRs) in the full matrix capture (FMC) signals and strong background noise in reconstructed images. To realize the high-SNR imaging of defects in PBXs, this paper is the first to schematically reorganize the nonlinear post-process algorithms which have the potential to realize high-SNR imaging of defects in crystalline particle-filled explosives. Six kinds of beamforming algorithms (DAS, F-DMAS, BB-DMAS, DMAS3, L-DMAS, and DS-DMAS) were applied to the same FMC data to reconstruct the images of prefabricated side-drilled holes (SDHs) in PBXs. The image quality in terms of SNR, lateral and axial resolution, and calculation efficiency was compared and evaluated quantitatively. The experimental results show that the nonlinear beamforming algorithms showed significant improvements in SNR and resolution. In particular, L-DMAS and DS-DMAS exhibited excellent imaging capability in SDH defect detection compared to the other algorithms, with effective suppression of crystalline structural noise. Full article

(This article belongs to the Special Issue Nondestructive Characterization and Evaluation of Crystalline Materials)

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13 pages, 3806 KiB

Open AccessArticle

Influence of the Annealing Temperature on the Properties of {ZnO/CdO}₃₀ Superlattices Deposited on c-Plane Al₂O₃ Substrate by MBE

by Anastasiia Lysak, Aleksandra Wierzbicka, Piotr Dłużewski, Marcin Stachowicz, Jacek Sajkowski and Ewa Przezdziecka

Crystals 2025, 15(2), 174; https://doi.org/10.3390/cryst15020174 - 10 Feb 2025

Viewed by 539

Abstract

{CdO/ZnO}_m superlattices (SLs) have been grown on c-plane sapphire substrates by plasma-assisted molecular beam epitaxy (PA-MBE). The observation of satellite peaks in the XRD studies of the as-grown and annealed samples confirms the presence of a periodic superlattice structure. The properties [...] Read more.

{CdO/ZnO}_m superlattices (SLs) have been grown on c-plane sapphire substrates by plasma-assisted molecular beam epitaxy (PA-MBE). The observation of satellite peaks in the XRD studies of the as-grown and annealed samples confirms the presence of a periodic superlattice structure. The properties of as-grown and annealed SLs deposited on c-oriented sapphire were investigated by transmission electron microscopy, X-ray diffraction and temperature dependent PL studies. The deformation of the SLs structure was observed after rapid thermal annealing. As the thermal annealing temperature increases, the diffusion of Cd ions from the quantum well layers into the ZnO barrier increases. The formation of CdZnO layers causes changes in the luminescence spectrum in the form of peak shifts, broadening and changes in the spacing of the satellite peaks visible in X-ray analysis. Full article

(This article belongs to the Special Issue Materials and Devices Grown via Molecular Beam Epitaxy)

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14 pages, 2343 KiB

Open AccessArticle

A Study of the Sorption Properties and Changes in the Structure and State of the Ti-25Al-25Nb (at.%) Alloy System Under Thermocyclic Loading

by Yernat Kozhakhmetov, Yerkezhan Tabiyeva, Nurya Mukhamedova, Azamat Urkunbay, Madina Aidarova, Aibar Kizatov and Elfira Sagymbekova

Crystals 2025, 15(2), 173; https://doi.org/10.3390/cryst15020173 - 10 Feb 2025

Viewed by 563

Abstract

This study is focused on the sorption properties and the changes in the structure and state of Ti-25Al-25Nb (at.%) system alloys under thermal cyclic loading. These samples were produced by combining high-energy processing methods through mechanization and spark plasma sintering in the temperature [...] Read more.

This study is focused on the sorption properties and the changes in the structure and state of Ti-25Al-25Nb (at.%) system alloys under thermal cyclic loading. These samples were produced by combining high-energy processing methods through mechanization and spark plasma sintering in the temperature range of 1100–1300 °C, followed by two-stage heat treatment at temperatures of 800 °C and 1250 °C. Thermal cyclic experiments on hydrogen sorption/desorption with samples of the Ti-25Al-25Nb (at.%) system were conducted at the VIKA experimental installation at a saturation temperature of about 500 °C and a degassing temperature of 610 °C. It took about 41 min to reach pressure equilibrium at 500 °C. The hydrogen diffusion coefficient was calculated based on the Barrer formula and was 9.1 × 10⁻⁵ cm²/s at 500 °C. The maximum hydrogen content was recorded after the first sorption/desorption cycle and was 1.91 wt%. Due to the multiple thermal cyclic effects in the hydrogen medium, the predominantly two-phase (O + B2) alloy structure underwent transformation to form a new structure (O-AlNbTi₂). In the phase composition of the Ti-25Al-25Nb (at.%) alloy, the formation of hydrides in the form of independent phases as a result of thermal cycling was not detected. Hydrogen absorption is most likely to be associated with the formation of an interstitial solution based on existing crystalline phases. Full article

(This article belongs to the Section Materials for Energy Applications)

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14 pages, 7852 KiB

Open AccessArticle

Effects of Y Additions on the Microstructure and Mechanical Properties of CoCr_1.7Ni Medium-Entropy Alloys

by Shaoshuai Zhou, Xiaoyong Shu, Linli Hu, Xunyu Yuan, Panpan Qiu and Xiwen Xu

Crystals 2025, 15(2), 172; https://doi.org/10.3390/cryst15020172 - 10 Feb 2025

Viewed by 498

Abstract

In order to improve the room temperature yield strength of X and enhance its engineering applicability, a series of CoCr_1.7NiY_x (x = 0, 0.01, 0.02, 0.03, 0.04, and 0.1 at.%) medium-entropy alloys were synthesized to investigate the effect of [...] Read more.

In order to improve the room temperature yield strength of X and enhance its engineering applicability, a series of CoCr_1.7NiY_x (x = 0, 0.01, 0.02, 0.03, 0.04, and 0.1 at.%) medium-entropy alloys were synthesized to investigate the effect of Y addition on the microstructures and mechanical properties of the CoCr_1.7Ni-based alloy. The X-ray diffraction results show that the alloys exhibit face-centered cubic (FCC) + body-centered cubic (BCC) + hexagonal close packing (HCP) triphasic structure when the Y is adopted, whereas the CoCr_1.7Ni-based alloy has a FCC+BCC biphasic structure. The volume fraction of BCC and HCP phase increased with increasing Y content, which led to alloy grain refinement. As a result, the microhardness and strength of alloys were both enhanced. The addition of Y resulted in dispersion strengthening and solid solution strengthening of CoCr_1.7Ni alloy, the appearance of HCP, and an increase in BCC, which improved the room temperature yield strength and hardness of CoCr_1.7Ni alloy. In particular, for CoCr_1.7NiY_0.1 alloy, its microhardness and yield strength, respectively, increased by 98.18% and 260.59% as compared with those of CoCr_1.7Ni alloy. Full article

(This article belongs to the Special Issue Advances in Processing, Simulation and Characterization of Alloys)

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12 pages, 1742 KiB

Open AccessArticle

Simulation of Lead-Free Perovskite Solar Cells with Improved Performance

by Saood Ali, Praveen Kumar, Khursheed Ahmad and Rais Ahmad Khan

Crystals 2025, 15(2), 171; https://doi.org/10.3390/cryst15020171 - 10 Feb 2025

Cited by 1 | Viewed by 673

Abstract

At present, lead halide PVSKSCs are promising photovoltaic cells but have some limitations, including their low stability in ambient conditions and the toxicity of lead. Thus, it will be of great significance to explore lead-free perovskite materials as an alternative absorber layer. In [...] Read more.

At present, lead halide PVSKSCs are promising photovoltaic cells but have some limitations, including their low stability in ambient conditions and the toxicity of lead. Thus, it will be of great significance to explore lead-free perovskite materials as an alternative absorber layer. In recent years, the numerical simulation of perovskite solar cells (PVSKSCs) via the solar cell capacitance simulation (SCAPS) method has attracted the attention of the scientific community. In this work, we adopted SCAPS for the theoretical study of lead (Pb)-free PVSKSCs. A cesium bismuth iodide (CsBi₃I₁₀; CBI) perovskite-like material was used as an absorber layer. The thickness of the CBI layer was optimized. In addition, different electron transport layers (ETLs), such as titanium dioxide (TiO₂), tin oxide (SnO₂), zinc oxide (ZnO), and zinc selenide (ZnSe), and different hole transport layers, such as spiro-OMeTAD (2,2,7,7-tetrakis(N,N-di(4-methoxyphenylamine)-9,9′-spirobifluorene), poly(3-hexylthiophene-2,5-diyl) (P₃HT), poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine (PTAA), and copper oxide (Cu₂O), were explored for the simulation of CBI-based PVSKSCs. A device structure of FTO/ETL/CBI/HTL/Au was adopted for simulation studies. The simulation studies showed the improved photovoltaic performance of CBI-based PVSKSCs using spiro-OMeTAD and TiO₂ as the HTL and ETL, respectively. An acceptable PCE of 11.98% with a photocurrent density (J_sc) of 17.360258 mA/cm², a fill factor (FF) of 67.10%, and an open-circuit voltage (V_oc) of 1.0282 V were achieved under the optimized conditions. It is expected that the present study will be beneficial for researchers working towards the development of CBI-based PVSKSCs. Full article

(This article belongs to the Section Materials for Energy Applications)

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17 pages, 10341 KiB

Open AccessArticle

Unveiling the Strengthening and Ductility Mechanisms of a CoCr₀.₄NiSi₀.₃ Medium-Entropy Alloy at Cryogenic Temperatures

by Li Zhang, Lingwei Zhang and Xiang Chen

Crystals 2025, 15(2), 170; https://doi.org/10.3390/cryst15020170 - 10 Feb 2025

Viewed by 547

Abstract

Materials utilized in extreme environments, such as those necessitating protection and impact resistance at cryogenic temperatures, must exhibit high strength, ductility, and structural stability. However, most alloys fail to maintain adequate toughness at cryogenic temperatures, thereby compromising their safety during cryogenic temperature service. [...] Read more.

Materials utilized in extreme environments, such as those necessitating protection and impact resistance at cryogenic temperatures, must exhibit high strength, ductility, and structural stability. However, most alloys fail to maintain adequate toughness at cryogenic temperatures, thereby compromising their safety during cryogenic temperature service. This study investigates the quasi-static mechanical properties of a CoCr₀.₄NiSi₀.₃ medium-entropy alloy (MEA) at room temperature, −75 °C, and −150 °C. The deformation behavior and mechanisms responsible for strengthening and toughening at reduced cryogenic temperatures are analyzed, revealing that decreasing cryogenic temperature enhances the strength of the as-cast MEA. Specifically, both the yield strength (YS) and ultimate tensile strength (UTS) of the MEA increase significantly with decreasing temperature during cryogenic tensile testing. Under tensile testing at −150 °C, the YS reaches 617.5 MPa, the UTS is 1055.0 MPa, and the elongation to fracture remains approximately 21.0% at both −150 °C and −75 °C. After cryogenic temperature tensile deformation, the matrix exhibits a dispersed distribution of nanoscaled tetragonal and orthorhombic phases, a coherent hexagonal close-packed phase, L1₂ phase and layered long-period stacking ordered (LPSO) structures, which are rarely observed in the cryogenic deformation of metals and alloys. The metastable phase evolution path of this MEA at cryogenic temperatures is closely associated with the decomposition of perfect dislocations into a/6<112> Shockley partial dislocations and their subsequent evolution at reduced cryogenic temperatures. At −75 °C, the a/6<112> Shockley partial dislocation interacts with the L1₂ phase to form antiphase boundaries (APBs) approximately 3 nm thick. At −150 °C, two phase transition paths from stacking faults (SFs) to nanotwins and LPSO occur, leading to the formation of layered LPSO structures and deformation-induced nanotwins. The dispersion of these coherent nanophases and nanotwins induced by the reduced stacking fault energy under cryogenic temperatures is the key factor contributing to the excellent balance of strength and plasticity in the as-cast MEA, providing an important basis for research on the cryogenic mechanical properties of CoCrNi-based MEAs. Full article

(This article belongs to the Special Issue Microstructure and Mechanical Behaviour of Structural Materials: 2nd Edition)

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