Crystals

5 pages, 153 KB

Open AccessEditorial

Advances in Metal Matrix Composites: Structure, Properties and Applications

by Lucia Lattanzi and Anders E. W. Jarfors

Crystals 2025, 15(12), 1016; https://doi.org/10.3390/cryst15121016 - 27 Nov 2025

Metal matrix composites (MMCs) are attractive materials due to their unique properties that stem from combining a wide range of matrix materials and reinforcements [...] Full article

(This article belongs to the Special Issue Advances in Metal Matrix Composites: Structure, Properties and Applications)

13 pages, 3475 KB

Open AccessArticle

3D Study of Microstructural Influences on Retained Austenite Transformation in Q&P 1180 Steel

by Isaac Chelladurai, Emily V. White, Michael P. Miles, Eric R. Homer, Anil K. Sachdev and David T. Fullwood

Crystals 2025, 15(12), 1015; https://doi.org/10.3390/cryst15121015 - 25 Nov 2025

Abstract

Advanced TRIP steels offer an attractive combination of strength and ductility because of the transformation-induced plasticity (TRIP) phenomenon. The retained austenite (RA) embedded in quenched and partitioning (Q&P) 1180 steel provides vital ductility, relating to the propensity of these grains to transform under [...] Read more.

Advanced TRIP steels offer an attractive combination of strength and ductility because of the transformation-induced plasticity (TRIP) phenomenon. The retained austenite (RA) embedded in quenched and partitioning (Q&P) 1180 steel provides vital ductility, relating to the propensity of these grains to transform under applied deformation. It is well known that the characteristics of the RA grains (size, shape, orientation, etc.) have a strong influence on their stability, but few studies consider the accurate 3-dimensional character of the grains, due to the cost of extracting 3D data. This study observes the characteristics of RA grains in Q&P 1180 steel before and after applying tensile deformation. EBSD maps of serial sectioned layers are reconstructed using DREAM3D. The influence of 3D morphology and other factors on transformation of RA is studied. Apart from relatively traditional metrics, a novel shear affinity factor is introduced as a metric to describe the ease of transformation for an RA grain. The 3D nature of the information collected allows accurate classification of grain shape into the traditional globular/spherical and lamellar/lath categories, along with disk and needle shapes, and enables quantification of the evolution of the shape distributions. Full article

(This article belongs to the Special Issue Microstructure and Mechanical Behavior of Advanced High Strength Steels)

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51 pages, 7076 KB

Open AccessArticle

BayCoN Plots and Systematic Errors in Single-Crystal Diffraction Experiments

by Julian Henn

Crystals 2025, 15(12), 1014; https://doi.org/10.3390/cryst15121014 - 25 Nov 2025

Abstract

Bayesian Conditional Probability (BayCoN) plots provide an empirical means to classify systematic errors in single-crystal diffraction experiments based on weighted residuals. Using a set of 314 structures from IUCrData, four recurring error types are identified and illustrated as follows: (i) incorrect standard uncertainties [...] Read more.

Bayesian Conditional Probability (BayCoN) plots provide an empirical means to classify systematic errors in single-crystal diffraction experiments based on weighted residuals. Using a set of 314 structures from IUCrData, four recurring error types are identified and illustrated as follows: (i) incorrect standard uncertainties of observed intensities, (ii) intensity and significance cut-offs, (iii) cases where weak observed intensities exceed calculated ones, like with incomplete absorption correction, and (iv) cases where they are systematically smaller. Only eleven data sets showed uniform BayCoN plots. The analysis focuses on how the residual distribution reveals and categorizes systematic errors; the impact on model parameters and their uncertainties is not addressed in this work. The proposed classification is intended to assist crystallographers in improving experimental accuracy by recognizing characteristic residual patterns. Full article

(This article belongs to the Section Inorganic Crystalline Materials)

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1 pages, 127 KB

Open AccessCorrection

Correction: Stakhanova et al. Hierarchically Porous Carbon Cloth–Polyaniline (CC–PANI) Composite Supercapacitor Electrodes with Enhanced Stability. Crystals 2024, 14, 457

by Svetlana V. Stakhanova, Ilya S. Krechetov, Kristina E. Shafigullina, Tatiana L. Lepkova, Valentine V. Berestov, Eugene S. Statnik, Zlatotsveta E. Zyryanova, Elena A. Novikova and Alexander M. Korsunsky

Crystals 2025, 15(12), 1013; https://doi.org/10.3390/cryst15121013 - 25 Nov 2025

Abstract

In the published article [...] Full article

(This article belongs to the Special Issue Synthesis, Characterization and Applications of Crystalline Electroconductive Polymers)

16 pages, 4609 KB

Open AccessArticle

Fabrication and Parameter Optimization of High-Melting-Point Pure Cr by Binder Jetting Additive Manufacturing

by Liyuan Shan, Yandong Shi, Xuming Su, Wenkai Li and Caiming Liu

Crystals 2025, 15(12), 1012; https://doi.org/10.3390/cryst15121012 - 24 Nov 2025

Abstract

BJ3DP has unique advantages compared to other energy-beam-based additive manufacturing technologies, such as lower residual stress, arising from the lack of heat during the printing process and the uniformity of the sintering process. However, attaining both high density and dimensional precision in metallic [...] Read more.

BJ3DP has unique advantages compared to other energy-beam-based additive manufacturing technologies, such as lower residual stress, arising from the lack of heat during the printing process and the uniformity of the sintering process. However, attaining both high density and dimensional precision in metallic materials remains a challenge in BJ3DP. This study presents a systematic investigation into the fabrication of high-melting-point pure chromium (Cr) via binder jetting 3D printing (BJ3DP), with a focus on optimizing the printing parameters and sintering conditions. An orthogonal experiment identified the optimal printing parameters as a layer thickness of 75 μm and a binder saturation of 60%, which resulted in green parts with a relative density of 57.1%—a representative value for BJ3DP processes that demonstrates effective parameter optimization. Subsequently, the green parts were sintered at 1800 °C for 9 h, resulting in a maximum density of 97.35%. The hardness of the as-sintered BJ3DP Cr parts was superior to that of samples produced by conventional levitation melting (184.20 HV vs. 171.20 HV). This work demonstrates that the no-heat printing strategy of BJ3DP effectively mitigates issues related to residual stress and cracking, providing a viable method for producing high-melting-point metallic materials. Full article

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28 pages, 2460 KB

Open AccessArticle

Interpretation of Copper Rolling Texture Components Development Based on Computer Modeling

by Wiesław Łatas, Mirosław Wróbel, Krzysztof Wierzbanowski and Dorota Byrska-Wójcik

Crystals 2025, 15(12), 1011; https://doi.org/10.3390/cryst15121011 - 24 Nov 2025

Abstract

Plastic deformation processes are widely used in metal forming. At the same time, they produce crystallographic textures that determine a material’s anisotropy—for example, its elastic, plastic, or magnetic anisotropy. Because these properties have significant practical implications and require precise control, understanding the mechanisms [...] Read more.

Plastic deformation processes are widely used in metal forming. At the same time, they produce crystallographic textures that determine a material’s anisotropy—for example, its elastic, plastic, or magnetic anisotropy. Because these properties have significant practical implications and require precise control, understanding the mechanisms of texture formation is essential. Consequently, the evolution of texture during plastic forming remains an important topic for both scientific and engineering communities. The most important models describing crystallographic texture development during plastic deformation were briefly reviewed. Based on a comparison of experimental results with numerical simulations obtained using the authors’ original fluctuating stress state (FSS) model, the main texture components were identified. It was shown that their volume fractions are primarily related to deformation fields in grains of polycrystalline material constrained by extreme boundary conditions, as well as to anisotropy in slip system hardening (A). The influence of both parameters and rolling true strain (1.5 and 2) on the copper rolling texture was evaluated by quantifying the fractions of the texture components, including the strong ones (B, S, Cu) and the weaker ones (G, W, rW). This constitutes the main novelty of the present work. Full article

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16 pages, 3169 KB

Open AccessArticle

Ceramic Bracket Surface Treated with Hydrofluoric Acid, Er, Cr: YSGG Laser, and Phthalocyanine Activated via Low-Level Laser Therapy on Surface Roughness and Shear Bond Strength Bonded to Enamel via Unmodified and Sepiolite-Modified Orthodontic Adhesive-A SEM, EDX, and DC Evaluation

by Salem Almoammar, Muhammad Abdullah Kamran, Abdulrahman Alshehri, Wael Awadh, Amirah Mesfer Alshahrani and Ibrahim Alshahrani

Crystals 2025, 15(12), 1010; https://doi.org/10.3390/cryst15121010 - 24 Nov 2025

Abstract

Influence of surface pretreatment Hydrofluoric acid (HFA), Erbium yttrium scandium gallium garnet (Er, Cr: YSGG) laser (ECL), and Phthalocyanine (Pc) photosensitizer (Ps) activated by Low-level laser therapy (LLLT) via a light-emitting diode (LED) device on surface roughness (Ra) and shear bond strength (SBS) [...] Read more.

Influence of surface pretreatment Hydrofluoric acid (HFA), Erbium yttrium scandium gallium garnet (Er, Cr: YSGG) laser (ECL), and Phthalocyanine (Pc) photosensitizer (Ps) activated by Low-level laser therapy (LLLT) via a light-emitting diode (LED) device on surface roughness (Ra) and shear bond strength (SBS) of ceramic bracket bonded to enamel via unmodified and Sepiolite-modified adhesive. Sixty non-cavitated human maxillary premolars were obtained. Ninety ceramic brackets were classified into three groups based on different pretreatment methods: Group 1: HFA; Group 2: ECL; and Group 3: Pc-LLLT. Twenty samples from each cohort were allocated into two subgroups by adhesive type: unmodified Transbond XT(A) and adhesive-modified Sep-NPs(B) (n = 10). Ra was measured using profilometry followed by surface topography via SEM, SBS via universal testing machine, and degree of conversion (DC) through FTIR spectroscopy. ANOVA and Tukey’s post hoc tests compared Ra, SBS, and DC across groups (p ˂ 0.05). Maximum Ra was observed in the ECL group (1087.43 ± 0.043 µm), while Group 3 (Pc-LLLT) showed the lowest Ra (706.53 ± 0.054 µm). Maximum SBS was recorded in Group 2B (ECL + SepNPs modified adhesive) (8.79 ± 0.48 MPa), while Group 3A (Pc-LLLT + unmodified adhesive) (5.23 ± 0.32 MPa) showed minimum bond integrity. ECL serves as an appropriate substitute for HFA in improving Ra and SBS of ceramic brackets to enamel. SepNPs improved the SBS of orthodontic adhesive to enamel with no significant difference in DC. Full article

(This article belongs to the Section Inorganic Crystalline Materials)

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20 pages, 8006 KB

Open AccessArticle

Correlating Microstructural and Mechanical Property Alteration with Process Parameters Using Thermal Signature Monitoring of Laser-Welded Inconel 625 Superalloy

by Gulshad Nawaz Ahmad, Mohammad Shahid Raza, Barun Haldar, Indrajeet Kumar, Nirmal Kumar Singh and Abdullah A. Elfar

Crystals 2025, 15(12), 1009; https://doi.org/10.3390/cryst15121009 - 24 Nov 2025

Abstract

Inconel 625 is widely employed in high-temperature and corrosive environments, where the integrity of welded joints critically influences component performance. This study systematically investigates how laser beam welding (LBW) heat input governs cooling behaviour, microstructure evolution, elemental segregation, and the mechanical performance of [...] Read more.

Inconel 625 is widely employed in high-temperature and corrosive environments, where the integrity of welded joints critically influences component performance. This study systematically investigates how laser beam welding (LBW) heat input governs cooling behaviour, microstructure evolution, elemental segregation, and the mechanical performance of Inconel 625 weld joints aiming to become sustainable joints. A single-spot monochromatic non-contact type infrared pyrometer is used to monitor the thermal cycles of the molten weld pool and the cooling rate and melt pool lifetime were determined based on the thermal cycle data. The impact of cooling rate and melt pool lifetime on weld geometry, microstructure, micro-segregation, and mechanical properties were thoroughly investigated. The findings revealed that the fibre laser welding produced sound, defect-free joints across all experimental heat-input conditions and the weld quality was fairly dictated by cooling rate during solidification. Reducing heat input (by using faster laser scan speeds) increased the cooling rate (1.45 × 10³ to 3.65 × 10³ °C/s), resulting in a shortened melt-pool lifetime and altered weld bead geometry from hourglass to truncated-cone profiles. Eventually, the fusion-zone microstructure transitioned from coarse cellular/columnar dendrites at high heat inputs to refined dendrites at low heat inputs. The EDS analysis revealed pronounced Nb and Mo segregation in slowly cooled welds and Laves phase formation due to insufficient time for solute redistribution and γ-Ni matrixes were consistent noted with XRD-observed peaks. The presence of the brittle Laves phase adversely affects the microhardness and tensile strength of the weld joints. Mechanical testing confirmed that decreasing heat input (in faster laser scan speeds) enhanced micro-hardness and tensile strength due to grain refinement and solute entrapment in the γ matrix. The highest joint strength (989.3 ± 10.4 MPa) and elongation (40.3 ± 1.8%) approached those of the work material, and these findings establish processing parameter–structure–property relationships for the LBW of Inconel 625. The co-relation in the present manuscript can be used in the future for process monitoring and for controlling the mechanical properties of laser welding and may provide a practical guidance for optimizing weld quality in advanced industrial applications. Full article

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

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11 pages, 1109 KB

Open AccessArticle

Formation Energy Prediction of Doped Perovskite Structures Based on Transfer Learning with Small Datasets

by Yang Yu, Mingxuan Deng, Tianhao Rui, Zhuangzhuang Ma, Linyuan Lu, Yunhao Wang, Tianxing Lan, Yulin Lan, Hengcheng Wan, Yiyan Li, Zhipeng Li and Haibin Zhang

Crystals 2025, 15(12), 1008; https://doi.org/10.3390/cryst15121008 - 24 Nov 2025

Abstract

Doped perovskites are widely studied in the domain of perovskite material design. However, due to the limited data available for the target materials, machine learning methods based on small datasets become particularly important. In this study, we propose a transfer learning strategy aimed [...] Read more.

Doped perovskites are widely studied in the domain of perovskite material design. However, due to the limited data available for the target materials, machine learning methods based on small datasets become particularly important. In this study, we propose a transfer learning strategy aimed at predicting doped perovskites on limited data samples. This strategy first utilizes the ABO₃-type perovskite dataset to develop a deep learning source model based on its formation energies. Then, fine-tuning is performed on the doped perovskite structure dataset to obtain a model with good transferability, applicable to the doped perovskite oxide target domain. Based on the transfer learning model, we further predict the formation energies of 12,897 A₂BB′O₆ compounds, 10,401 AA′B₂O₆ compounds, and 49,723 AA′BB′O₆ compounds. With the tolerance factor

t \in [0.7 - 1.1]

, octahedral factor

μ \in [0.45 - 0.7]

, and the modified tolerance factor

τ \in [0, 4.18]

for screening, we successfully predict 3389 A₂B′BO₆, 3002 AA′B₂O₆, and 13,563 AA′BB′O₆ structures as potential stable doped perovskite candidates. Among these filtered results, 821 A₂B′BO₆, 69 AA′B₂O₆, and 6 AA′BB′O₆ compounds have been reported in the OQMD database. For each doped perovskite, we select the candidate with the lowest formation energy and perform DFT validation. This resulted in three newly reported stable doped perovskite materials: CaSrHfScO₆, BaSrHf₂O₆, and Ba₂HfNdO₆. The transfer learning-based perovskite material design method proposed in this study not only effectively addresses the challenges of model training on small datasets but also significantly improves the accuracy and stability of doped perovskite material predictions. Through transfer learning, the model can fully leverage the data and knowledge from the ABO₃-type perovskite, effectively overcoming the problem of limited data. This strategy provides a new approach for efficient perovskite material design, enabling broader structural and performance predictions under limited experimental data conditions, and offering a powerful tool for the development of novel functional materials. Full article

(This article belongs to the Special Issue Emerging Perovskite Materials and Applications)

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16 pages, 10522 KB

Open AccessArticle

Particle Size-Dependent Mechanical Behaviors of Disordered Copper Nanoparticle Assemblies: A Molecular Dynamics Study

by Jianjun Bian and Liang Yang

Crystals 2025, 15(12), 1007; https://doi.org/10.3390/cryst15121007 - 23 Nov 2025

Abstract

The mechanical behavior of nanoparticle assemblies depends strongly on particle size, yet the underlying mechanisms remain insufficiently understood. In present study, we employ a scheme combining discrete element method (DEM) and molecular dynamics (MD) simulations to examine size-dependent strength and deformation in disordered [...] Read more.

The mechanical behavior of nanoparticle assemblies depends strongly on particle size, yet the underlying mechanisms remain insufficiently understood. In present study, we employ a scheme combining discrete element method (DEM) and molecular dynamics (MD) simulations to examine size-dependent strength and deformation in disordered copper nanoparticle assemblies. Granular packings generated by DEM were transformed into atomic models and subjected to uniaxial compression in MD simulations. Assemblies composed of nanoparticles with radius smaller than ~2.5 nm fully densify during relaxation, forming nanopolycrystalline solids, whereas larger particles preserve porous architectures. This structural divergence governs subsequent deformation. Small-particle assemblies deform through grain boundary migration and grain growth, exhibiting an inverse Hall–Petch-type strength dependence. In contrast, large-particle assemblies deform primarily via interparticle contact evolution and densification, with strength conforming to a Gibson–Ashby-type prediction. A scaling law captures the strength variation across size range in this regime. These results establish the competition between surface energy-driven densification and contact-dominated deformation as the controlling factor in the mechanical response of nanoparticle assemblies, providing guidance for designing nanoparticle-based materials with tailored mechanical performance. Full article

(This article belongs to the Section Inorganic Crystalline Materials)

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14 pages, 5937 KB

Open AccessArticle

Variation in Carbon Content During the Melting of γ-TiAl in a Graphite Crucible

by Byungil Kang, Taekyu Ha, Seul Lee and Youngjig Kim

Crystals 2025, 15(12), 1006; https://doi.org/10.3390/cryst15121006 - 22 Nov 2025

Abstract

Liquid γ-TiAl alloy was prepared by vacuum induction melting within graphite crucibles, then cast using a centrifugal technique. In this process, the degree of superheat (ΔT)—defined as the temperature above the melting point—was carefully controlled, with experiments conducted at ΔT of 200 K [...] Read more.

Liquid γ-TiAl alloy was prepared by vacuum induction melting within graphite crucibles, then cast using a centrifugal technique. In this process, the degree of superheat (ΔT)—defined as the temperature above the melting point—was carefully controlled, with experiments conducted at ΔT of 200 K (i.e., 200 Kelvin above the melting temperature). It was observed that carbon content in the alloy increased nonlinearly as the melt was held longer in the graphite crucible; for example, carbon concentration rose from an initial value of approximately 0.21 at% to 0.98 at% after 100 s of holding and to 2.11 at% at 650 s of holding. When the melt was held for over 100 s at ΔT = 200 K, titanium carbide (TiC) and titanium aluminum carbide (Ti₂AlC) particles formed along the crucible wall. This resulted in changes to the phase fractions and a corresponding increase in aluminum concentration in the melt. Two types of Ti₂AlC phases were observed: one consisted of coarse Ti₂AlC particles, which were crystallized through peritectic reaction from the TiC carbide and liquid phase. The other consisted of fine Ti₂AlC particles, which were decomposed from the α₂ (Ti₃Al) phase within the interlamellar regions. After 20 s of holding at ΔT = 200 K, carbon rapidly dissolved into a solid solution. Prolonged holding led to significant grain refinement: the microstructure evolved from columnar to equiaxed grains, primarily due to TiC crystallization. This transition is significant because finer, equiaxed grains can enhance mechanical properties such as strength and toughness. The findings provide valuable insight into the interaction between graphite crucibles and γ-TiAl melts, demonstrating how controlled superheat and holding time influence carbon uptake, carbide formation, and microstructural evolution—factors critical for optimizing the performance and manufacturability of γ-TiAl components. Full article

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10 pages, 3852 KB

Open AccessArticle

Influence of Silicon Content on Mechanical and Tribological Properties of FeSi Steels

by Marcela Motýľová, Ivan Petrišinec, Róbert Džunda and Jana Andrejovská

Crystals 2025, 15(12), 1005; https://doi.org/10.3390/cryst15121005 - 22 Nov 2025

Abstract

Non-oriented (NO) Fe–Si electrical steels are key materials for magnetic cores of electrical machines, requiring a balance between magnetic and mechanical properties. This study systematically examined the effect of silicon content (1.06 wt%, 2.15 wt%, and 3.09 wt%) on the microstructure, mechanical, and [...] Read more.

Non-oriented (NO) Fe–Si electrical steels are key materials for magnetic cores of electrical machines, requiring a balance between magnetic and mechanical properties. This study systematically examined the effect of silicon content (1.06 wt%, 2.15 wt%, and 3.09 wt%) on the microstructure, mechanical, and tribological behavior of three produced NO steel grades. Mechanical properties were assessed using tensile tests, microhardness, and nanoindentation, while tribological performance was evaluated under dry reciprocating sliding (ball-on-flat) against a 100Cr6 steel ball at loads of 5 N, 10 N, and 25 N. Increasing silicon content led to larger grain size, higher hardness (227 HV–361 HV) and strength, but lower ductility. Tribological behavior depended on both composition and load. The most stable friction regime occurred at 10 N. The medium-Si steel (N3, 2.15 wt%) exhibited the best performance with a low coefficient of friction (COF ≈ 0.52–0.55); N5 (3.09 wt%) showed a similar COF, while N1 (1.06 wt%) had a slightly higher value. At 25 N, an inverse relationship between hardness and friction appeared: softer N1 had the lowest COF (≈0.68–0.70), whereas harder N3 and N5 reached ≈ 0.74–0.78. Scanning electron microscopy (SEM) observations revealed abrasive wear for N3/N5 and plastic flow (galling) for N1. Overall, an optimal silicon content provides the best compromise between hardness and tribological stability depending on load conditions. Full article

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13 pages, 3069 KB

Open AccessArticle

Boosting Charge Separation in NiS/C₃N₄ Type-II Heterojunction for Efficient Photoelectrocatalytic Water Reduction

by Xiaobo Liang, Lingdan Dong, Yanning Chen, Chunhai Qi, Chunyi Xu, Wenhao Zhang, Lingling Bi and Liang Zhao

Crystals 2025, 15(12), 1004; https://doi.org/10.3390/cryst15121004 - 21 Nov 2025

Abstract

To tackle the intrinsic limitations of fast charge recombination and sluggish reaction kinetics in carbon nitride (C₃N₄) for photoelectrocatalytic (PEC) water reduction reaction, we constructed a NiS/C₃N₄ heterojunction photoelectrode via a sequential approach combining chemical vapor [...] Read more.

To tackle the intrinsic limitations of fast charge recombination and sluggish reaction kinetics in carbon nitride (C₃N₄) for photoelectrocatalytic (PEC) water reduction reaction, we constructed a NiS/C₃N₄ heterojunction photoelectrode via a sequential approach combining chemical vapor deposition and hydrothermal treatment. Compared with pristine C₃N₄, the introduction of NiS significantly reduced interfacial charge transfer resistance and effectively suppressed the photogenerated carrier recombination. Among all compositions investigated, the NiS-0.2 photoelectrode demonstrated a maximum photocurrent density of −13.44 mA cm⁻² at −0.8 V vs. RHE, representing a more than 6.7-fold enhancement in comparison to bare C₃N₄ (−2.00 mA cm⁻²). This remarkable improvement is attributed to the construction of an efficient type-II heterojunction between C₃N₄ and NiS. Under the driving force of the internal electric field at the interface, photoinduced electrons migrate from the conduction band of C₃N₄ to NiS, whereas holes move from the valence band of NiS to C₃N₄. This spatial separation mechanism, coupled with the role of NiS as an efficient active site for the water reduction reaction, synergistically enhances the overall PEC performance. This work offers a rational and feasible approach for designing efficient, stable, and cost-effective C₃N₄-based photoelectrodes. Full article

(This article belongs to the Section Inorganic Crystalline Materials)

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16 pages, 2349 KB

Open AccessArticle

Optical and Vibrational Properties of AlN Nanoparticles with Different Geometries: A DFT and TD-DFT Study

by Fotios I. Michos, Christina Papaspiropoulou, Nikos Aravantinos-Zafiris and Michail M. Sigalas

Crystals 2025, 15(12), 1003; https://doi.org/10.3390/cryst15121003 - 21 Nov 2025

Abstract

In this work, by using density functional theory (DFT) and time-dependent DFT (TD-DFT) a comprehensive theoretical study on the structural, electronic, optical, and vibrational properties of aluminum nitride (Al_xN_x) nanoparticles (NPs) is presented. More than thirty nanostructures were constructed [...] Read more.

In this work, by using density functional theory (DFT) and time-dependent DFT (TD-DFT) a comprehensive theoretical study on the structural, electronic, optical, and vibrational properties of aluminum nitride (Al_xN_x) nanoparticles (NPs) is presented. More than thirty nanostructures were constructed based on an initial cubic-like Al₄N₄ building block, including one-dimensional (1D), two-dimensional (2D), and three-dimensional (3D) configurations, as well as asymmetric and defected geometries (also known as exotic geometries). The absorption spectrum was evaluated using the CAM-B3LYP functional while geometry optimizations and vibrational frequencies were performed using the PBE functional. All calculations were performed using the triple-ζ valence plus polarization basis set def2-TZVP. The optical spectra revealed strong geometry-dependent modulation of absorption, with red-shifted and broadened UV–Vis features emerging in elongated and low-symmetry geometries. IR analysis indicates a growing number and intensity of vibrational modes with increasing dimensionality, particularly in the 300–470 cm⁻¹ range, which corresponds to Al–N stretching and bending vibrations. Testing different exchange–correlation functionals showed that CAM-B3LYP is a good choice for excited-state calculations, matching well with the EOM-CCSD functional, which, while offering higher precision, imposes significantly higher computational requirements. Overall, the results demonstrate that structural variation in Al_xN_x NPs leads to tunable optoelectronic and spectroscopic behavior. These findings and calculations highlight the potential of AlN-based nanomaterials for applications in ultraviolet photonics, sensors, and future nanoscale optoelectronic devices. Full article

(This article belongs to the Section Inorganic Crystalline Materials)

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20 pages, 7256 KB

Open AccessArticle

Influence of Y₂O₃ Content and Sintering Temperature on Microstructure and Mechanical Properties of YSZ Ceramics

by Madi Abilev, Dias Yerbolat, Mazhyn Skakov, Almira Zhilkashinova, Alexandr Pavlov and Igor Karpov

Crystals 2025, 15(11), 1002; https://doi.org/10.3390/cryst15111002 - 20 Nov 2025

Abstract

This study investigates the influence of Y₂O₃ content and sintering temperature on the microstructure, phase composition, and physico-mechanical properties of zirconia-based ceramics with Al₂O₃ addition. It was shown that varying the stabilizer content within 3.0–6.0 wt.% Y [...] Read more.

This study investigates the influence of Y₂O₃ content and sintering temperature on the microstructure, phase composition, and physico-mechanical properties of zirconia-based ceramics with Al₂O₃ addition. It was shown that varying the stabilizer content within 3.0–6.0 wt.% Y₂O₃ leads to observable changes in the phase composition and grain size, as well as affecting the density and microhardness of the material. The sintering conditions ensuring the required density and homogeneous microstructure at moderate temperatures were determined. This research is aimed at optimizing synthesis and heat treatment parameters to produce a dense material with minimal porosity and stable mechanical characteristics. The samples were shaped by uniaxial pressing and sintered in the temperature range of 1530–1570 °C. The structure and phase composition were analyzed using X-ray diffraction and scanning electron microscopy, while the physico-mechanical properties were evaluated by measuring apparent density, porosity, and microhardness. The sintering temperature of 1550 °C was identified as optimal for achieving the highest performance characteristics while maintaining structural homogeneity. The addition of Al₂O₃ contributes to a reduction in the sintering temperature without compromising the material’s properties. Full article

(This article belongs to the Section Polycrystalline Ceramics)

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19 pages, 5760 KB

Open AccessArticle

Effect of Over-Temperature on Creep Damage of Bi-Based Brazing Filler Alloy

by Jun Hong, Tao Wang, Baoyin Zhu, Dongpeng Li, Haitao Dong, Dungui Zuo and Gongye Zhang

Crystals 2025, 15(11), 1001; https://doi.org/10.3390/cryst15111001 - 20 Nov 2025

Abstract

This work investigates the creep damage behavior and life prediction of Bi-based brazing alloys and their corresponding joints under intermittent over-temperature conditions, and proposes an integrated real-time monitoring and analytical framework. Temperature–time histories of structural components are acquired using both fixed and mobile [...] Read more.

This work investigates the creep damage behavior and life prediction of Bi-based brazing alloys and their corresponding joints under intermittent over-temperature conditions, and proposes an integrated real-time monitoring and analytical framework. Temperature–time histories of structural components are acquired using both fixed and mobile infrared thermography systems to quantify thermal fluctuations. These data are subsequently coupled with a materials database and an enhanced Kachanov–Rabotnov creep damage constitutive model to simulate the evolution of thermally induced stresses and the accumulation of damage. Structural parameters, including weld seam thickness and porosity, are incorporated to perform sensitivity analyses. Experimental findings reveal a pronounced decline in the yield strength of the Bi-based brazing alloy with increasing temperature, identifying this degradation as the principal driver of creep failure. Fractographic observations show intergranular rupture characteristics during creep, in distinct contrast to the transgranular fracture mechanisms observed under tensile loading. Model predictions exhibit excellent concordance with experimental data and faithfully capture the life evolution across varying thermal–mechanical conditions. The results demonstrate that the proposed system enables real-time assessment of the health state, residual life, and failure risk of critical components. Moreover, it provides a robust theoretical foundation and practical guidance for operational safety management and maintenance decision-making in large enclosed containment structures, including those employed in nuclear power systems. Full article

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

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17 pages, 1865 KB

Open AccessArticle

Halogens On, H-Bonds Off—Insights into Structure Control of Dihalogenated Imidazole Derivatives

by Luca Mensing, Marcus Layh and Marian Hebenbrock

Crystals 2025, 15(11), 1000; https://doi.org/10.3390/cryst15111000 - 20 Nov 2025

Abstract

Halogen bonds play an important role in the targeted generation of solid-state structures, with polyhalogenated compounds enabling the simultaneous formation of various interactions. In this manuscript, we investigate the interactions of dihalogenated compounds in the solid state. Unlike investigated in previous studies, the [...] Read more.

Halogen bonds play an important role in the targeted generation of solid-state structures, with polyhalogenated compounds enabling the simultaneous formation of various interactions. In this manuscript, we investigate the interactions of dihalogenated compounds in the solid state. Unlike investigated in previous studies, the introduction of protective groups in these compounds prevents the formation of dominant hydrogen bonds. The structures of diiodo imidazole derivatives are compared with the analogous dibromo compounds. A total of four different protective groups (two benzylic and two oxycarbonyl protective groups) are introduced and the respective compounds are characterized by X-ray crystallography. The significance of the protective groups for the solid-state structure can be distinguished on the basis of the additional donor atoms and functional groups. It can be seen that the iodo compounds in particular are capable of forming halogen bonds and that additional structural motifs can be generated by suitable protective groups. Full article

(This article belongs to the Special Issue Analysis of Halogen and Other σ-Hole Bonds in Crystals (2nd Edition))

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Graphical abstract

16 pages, 4366 KB

Open AccessArticle

Influence of Fly Ash on the Macro Properties and Mineral Crystal Characteristics of Alkali-Activated Slag Grouting Materials

by Guodong Huang, Jiahao Xu, Jun Qi, Fengan Zhang and Baoxuan Dou

Crystals 2025, 15(11), 999; https://doi.org/10.3390/cryst15110999 - 20 Nov 2025

Abstract

Alkali-activated slag grouting materials exhibited excellent mechanical properties but still faced technical challenges such as insufficient fluidity and overly rapid setting. To enhance their workability, this study introduced fly ash as a modifying component, leveraging its morphological and activity effects to systematically investigate [...] Read more.

Alkali-activated slag grouting materials exhibited excellent mechanical properties but still faced technical challenges such as insufficient fluidity and overly rapid setting. To enhance their workability, this study introduced fly ash as a modifying component, leveraging its morphological and activity effects to systematically investigate the composite influence on fluidity, setting time, and compressive strength. The mechanism was further elucidated through microstructural analysis of the mineral crystallization characteristics of polycondensation products. The results indicated that with increasing fly ash content, the fluidity of the grouting material continuously improved, and both the initial and final setting times were significantly prolonged, albeit at the expense of a gradual decline in compressive strength. At a 20% fly ash content, the fluidity spread increased to 292 mm, the initial and final setting times were extended to 70 min and 103 min, respectively, while the 1 d and 28 d compressive strengths reached 11.8 MPa and 48.1 MPa, achieving an optimal overall performance that met practical grouting requirements. Microscopic analysis revealed that fly ash enhanced the rheological properties and delayed the setting process through the “ball-bearing effect” and its low early-age reactivity. However, as the fly ash content rose, the active calcium content in the system continuously decreased, inhibiting the formation and development of key mineral crystals such as calcium silicate and calcium aluminosilicate, thereby leading to the reduction in compressive strength. Full article

(This article belongs to the Section Crystal Engineering)

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21 pages, 5717 KB

Open AccessArticle

Effect of Partial Fe-Substitution by Y and/or Ce in BaFeO₃-Based Oxides on Oxygen Diffusion

by Anna Khodimchuk, Irina Svishch, Egor Gordeev and Natalia Porotnikova

Crystals 2025, 15(11), 998; https://doi.org/10.3390/cryst15110998 - 19 Nov 2025

Abstract

The chemical diffusion coefficients of oxygen (

D^{δ}

) for the oxides BaFe_0.9Ce_0.1O_3−δ (BFC10), BaFe_0.9Y_0.1O_3−δ (BFY10), and BaFe_0.8Ce_0.1Y_0.1O_3−δ (BFCY1010) were determined by [...] Read more.

The chemical diffusion coefficients of oxygen (

D^{δ}

) for the oxides BaFe_0.9Ce_0.1O_3−δ (BFC10), BaFe_0.9Y_0.1O_3−δ (BFY10), and BaFe_0.8Ce_0.1Y_0.1O_3−δ (BFCY1010) were determined by the oxygen pressure relaxation method in the T = 600–800 °C and pO₂ = 0.1–3.5 kPa ranges. The oxygen diffusion coefficients at 700 °C were found to be 1.80·10⁻⁵, 3.92·10⁻⁵, and 1.85·10⁻⁵ cm²/s for BFC10, BFY10, and BFCY1010, respectively. It was established that the volume oxygen diffusion increases in the order

D^{δ}

(BFY10) >

D^{δ}

(BFCY1010) >

D^{δ}

(BFC10), which correlates with the data on oxygen non-stoichiometry (δ), and is associated with the oxygen vacancy content in oxides. The values of effective activation energies were determined: 1.21 ± 0.04, 1.31 ± 0.10, and 1.18 ± 0.09 eV for BFC10, BFY10, and BFCY1010, respectively. A comparative analysis of oxygen transport highlights the potential of co-doped BaFe_0.8Ce_0.1Y_0.1O_3−δ as a promising cobalt-free cathode material with triple (oxygen, proton, electron) conductivity. Full article

(This article belongs to the Section Inorganic Crystalline Materials)

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