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Crystals
Volume 15
Issue 6
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Crystals, Volume 15, Issue 6 (June 2025) – 95 articles

Cover Story (view full-size image): Crystals of sodium dithiocuprate(I) dodecahydrate, [Na3(H2O)12][CuS2], formed from NaOH/Na2S solutions used for arsenic separation from copper ore. This salt features a linear hydrogen-bonded dithiocuprate(I) anion, a novelty in crystallographically characterized thiocuprates. While we aimed to understand the chemical behavior of the leaching solution by identifying the thioarsenate ions formed, the complex [CuS2]3− was discovered by coincidence using single-crystal analysis. Subsequent targeted synthesis from a modeling solution, based on the leaching solution formulation for arsenic removal, allowed for further crystal characterization through Raman and XRD analyses. By demonstrating that copper can also be leached at high sulfide concentrations, the results presented in this study contribute to the economic development of arsenic removal via sulfide leaching. View this paper
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22 pages, 4680 KiB  
Review
Surface Electric Properties and Their Role in the Bioactivity of Implant Materials: A Comprehensive Review
by Valentina Vadimovna Chebodaeva
Crystals 2025, 15(6), 583; https://doi.org/10.3390/cryst15060583 - 19 Jun 2025
Viewed by 313
Abstract
The surface electric charge of biomaterials plays a pivotal role in determining their bioactivity and biocompatibility, especially in orthopedic and dental applications. This review analyzes recent progress (2015–2024) in understanding how electric properties, particularly surface charge and zeta potential, modulate cellular adhesion, proliferation, [...] Read more.
The surface electric charge of biomaterials plays a pivotal role in determining their bioactivity and biocompatibility, especially in orthopedic and dental applications. This review analyzes recent progress (2015–2024) in understanding how electric properties, particularly surface charge and zeta potential, modulate cellular adhesion, proliferation, and differentiation. Negatively charged surfaces (−20 to −30 mV) were consistently associated with enhanced osteoblast activity and calcium mineralization, while positively charged surfaces often induced pro-inflammatory responses. We explore theoretical models of the electric double layer (EDL), methods for quantifying surface charge, and strategies for modifying surface potential to enhance biological outcomes. A comparative analysis of materials—hydroxyapatite coatings, PCL scaffolds, titanium surfaces, and piezoceramics—is provided. Finally, we highlight knowledge gaps in mechanistic understanding and emphasize the need for standardized protocols in evaluating the electric properties of biomaterials. Full article
(This article belongs to the Section Inorganic Crystalline Materials)
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12 pages, 3031 KiB  
Article
Doping Effects on Magnetic and Electronic Transport Properties in BaZn2As2
by Guoqiang Zhao, Gangxu Gu, Shuai Yang, Yi Peng, Xiang Li, Kenji M. Kojima, Chaojing Lin, Xiancheng Wang, Timothy Ziman, Yasutomo J. Uemura, Bo Gu, Gang Su, Sadamichi Maekawa, Yongqing Li and Changqing Jin
Crystals 2025, 15(6), 582; https://doi.org/10.3390/cryst15060582 - 19 Jun 2025
Viewed by 605
Abstract
Novel diluted magnetic semiconductors derived from BaZn2As2 are of considerable importance owing to their elevated Curie temperature of 260 K, the diversity of magnetic states they exhibit, and their prospective applications in multilayer heterojunctions. However, the transition from the intrinsic [...] Read more.
Novel diluted magnetic semiconductors derived from BaZn2As2 are of considerable importance owing to their elevated Curie temperature of 260 K, the diversity of magnetic states they exhibit, and their prospective applications in multilayer heterojunctions. However, the transition from the intrinsic semiconductor BaZn2As2 (BZA) to its doped compounds has not been extensively explored, especially in relation to the significant intermediate compound Ba(Zn,Mn)2As2 (BZMA). This study aims to address this gap by performing susceptibility and magnetization measurements, in addition to electronic transport analyses, on these compounds in their single crystal form. Key findings include the following: (1) carriers can significantly modulate the magnetism, transitioning from a non-magnetic BZA to a weak magnetic BZMA, and subsequently to a hard ferromagnet (Ba,K)(Zn,Mn)2As2 with potassium (K) doping to BZMA; (2) two distinct sets of metal-insulator transitions were identified, which can be elucidated by the involvement of carriers and the emergence of various magnetic states, respectively; and (3) BZMA exhibits colossal negative magnetoresistance, and by lanthanum (La) doping, a potential n-type (Ba,La)(Zn,Mn)2As2 single crystal was synthesized, demonstrating promising prospects for p-n junction applications. This study enhances our understanding of the magnetic interactions and evolutions among these compounds, particularly in the low-doping regime, thereby providing a comprehensive physical framework that complements previous findings related to the high-doping region. Full article
(This article belongs to the Section Inorganic Crystalline Materials)
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12 pages, 3008 KiB  
Article
Structural, Thermophysical, and Radiation Shielding Properties of Lead–Bismuth Eutectic (LBE) Synthesized by Induction Melting
by Radu Cristian Gavrea, Emanoil Surducan, Răzvan Hirian, Mioara Zagrai and Vasile Rednic
Crystals 2025, 15(6), 581; https://doi.org/10.3390/cryst15060581 - 19 Jun 2025
Viewed by 271
Abstract
Lead–bismuth eutectic alloy (LBE, Pb44.5Bi55.5) has emerged as a promising candidate for use in advanced nuclear and solar energy systems due to its favorable thermophysical characteristics and radiation shielding capabilities. The aim of this research is to assess the [...] Read more.
Lead–bismuth eutectic alloy (LBE, Pb44.5Bi55.5) has emerged as a promising candidate for use in advanced nuclear and solar energy systems due to its favorable thermophysical characteristics and radiation shielding capabilities. The aim of this research is to assess the applicability of the induction melting technique to synthesize LBE. This paper presents a comprehensive evaluation of the structural, thermophysical, and radiation shielding properties of the obtained LBE sample. Various techniques were employed to investigate the solid-to-liquid eutectic transformation, phase composition, morphology, and homogeneity of the obtained material. Experimental and theoretical determinations on density, void, molar volume, thermal conductivity, heat capacity, thermal diffusivity, and electrical conductivity were performed. Radiation shielding performance over photon energies ranging from 0.015 to 15 MeV was simulated using the Phy-X/PSD program. The results revealed the eutectic structure comprising Pb7Bi3 and Bi phases with near-ideal stoichiometry and a melting point of 127.6 °C. The alloy demonstrated a small void that corresponds to a high degree of sample compaction, high specific heat capacity, moderate thermal conductivity, low thermal diffusivity, and effective radiation shielding. These findings confirm that LBE obtained by the induction melting technique possesses the necessary structural stability and functional properties for integration into nuclear reactor and solar thermal technologies. Full article
(This article belongs to the Special Issue Exploring New Materials for the Transition to Sustainable Energy)
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16 pages, 3258 KiB  
Article
Breaking the Efficiency–Quality Tradeoff via Temperature–Velocity Co-Optimization: Multiscale Calculations and Experimental Study of Epitaxial Growth of Iridium on MgO(100)
by Yang Wang, Junhao Chen, Shilin Yang and Jiaqi Zhu
Crystals 2025, 15(6), 580; https://doi.org/10.3390/cryst15060580 - 19 Jun 2025
Viewed by 235
Abstract
The precise control of thermal–kinetic parameters governs epitaxial perfection in functional oxide heterostructures. Herein, using Iridium/MgO(100) as a model system, the traditional “low-speed/high-temperature” paradigm is revolutionized through the combination of ab initio calculations, multiscale simulations, and subsequent deposition experiments. First-principles modeling reveals the [...] Read more.
The precise control of thermal–kinetic parameters governs epitaxial perfection in functional oxide heterostructures. Herein, using Iridium/MgO(100) as a model system, the traditional “low-speed/high-temperature” paradigm is revolutionized through the combination of ab initio calculations, multiscale simulations, and subsequent deposition experiments. First-principles modeling reveals the mechanisms of Volmer–Weber (VW, island growth mode) nucleation at low coverage and Stranski–Krastanov (SK, layer-plus-island growth) transitions driven by interface metallization, stress release, and energy reduction, which facilitates coherent monolayer formation by lowering the energy barrier by ~34%. Molecular dynamics simulations demonstrate that the strategic co-optimization of substrate temperature (Tsub) and deposition rate (Vdep) induces an abrupt cliff-like drop in mosaic spread. Experimental validations confirm that this T-V synergy achieves unprecedented interfacial coherence, whereby AFM roughness reaches 0.34 nm (RMS) and the XRC-FWHM of 0.13° approaches single-crystal benchmarks. Notably, our novel “accelerated heteroepitaxy” protocol reduces growth time without compromising quality, addressing the efficiency–quality paradox in industrial-scale diamond substrate fabrication. These findings establish universal thermal–kinetic design principles applicable to refractory metal/oxide heterostructures for next-generation quantum sensors and high-power electronic devices. Full article
(This article belongs to the Special Issue Crystallization Process and Simulation Calculation, Third Edition)
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17 pages, 2850 KiB  
Article
Influence of NaCl on Phase Development and Corrosion Resistance of Portland Cement
by Byung-Hyun Shin, Miyoung You, Jinyong Park, Junghyun Cho, Seongjun Kim, Jung-Woo Ok, Jonggi Hong, Taekyu Lee, Jong-Seong Bae, Pungkeun Song and Jang-Hee Yoon
Crystals 2025, 15(6), 579; https://doi.org/10.3390/cryst15060579 - 19 Jun 2025
Viewed by 309
Abstract
Portland cement is one of the most widely used construction materials employed in both large-scale structures and everyday applications. Although various materials are often added during production to enhance their performance, NaCl can be introduced in the process for various reasons. Despite this [...] Read more.
Portland cement is one of the most widely used construction materials employed in both large-scale structures and everyday applications. Although various materials are often added during production to enhance their performance, NaCl can be introduced in the process for various reasons. Despite this issue, existing studies lack sufficient quantitative data on the effects of NaCl on cement properties. Therefore, this study aims to investigate the physical and chemical degradation mechanisms in cement containing NaCl. Cement specimens were prepared by mixing cement, water, and NaCl, followed by stirring at 60 rpm and curing at room temperature for seven days. Microstructural changes as a function of the NaCl concentration were analyzed using scanning electron microscopy (SEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). Electrochemical properties were evaluated via open-circuit potential (OCP) measurements, electrochemical impedance spectroscopy (EIS), and potentiodynamic polarization tests. The results indicate that increasing the NaCl concentration leads to the formation of fine precipitates, the degradation of the cement matrix, and the reduced stability of major hydration products. Furthermore, the electrochemical analysis revealed that higher NaCl concentrations weaken the passive layer on the cement surface, resulting in an increased corrosion rate from 1 × 10−7 to 4 × 10−7 on the active polarization of the potentiodynamic polarization curve. Additionally, the pitting potential (Epit) decreased from 0.73 V to 0.61 V with an increasing NaCl concentration up to 3 wt.%. This study quantitatively evaluates the impact of NaCl on the durability of Portland cement and provides fundamental data to ensure the long-term stability of cement structures in chloride-rich environments. Full article
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9 pages, 2014 KiB  
Article
Pd-Gated N-Polar GaN/AlGaN High-Electron-Mobility Transistor for High-Sensitivity Hydrogen Gas Detection
by Long Ge, Haineng Bai, Yidi Teng and Xifeng Yang
Crystals 2025, 15(6), 578; https://doi.org/10.3390/cryst15060578 - 18 Jun 2025
Viewed by 249
Abstract
Hydrogen gas sensing is critical for energy storage, industrial safety, and environmental monitoring. However, traditional sensors still face challenges in selectivity, sensitivity, and stability. This work introduces an innovative N-polar GaN/AlGaN high-electron-mobility transistor (HEMT) with a 10 nm Pd catalytic layer as a [...] Read more.
Hydrogen gas sensing is critical for energy storage, industrial safety, and environmental monitoring. However, traditional sensors still face challenges in selectivity, sensitivity, and stability. This work introduces an innovative N-polar GaN/AlGaN high-electron-mobility transistor (HEMT) with a 10 nm Pd catalytic layer as a hydrogen sensor. The device achieves ppm-level H2 detection with rapid recovery and reusability, which is comparable to or even exceeds the performance of conventional Ga-polar HEMTs. The N-polar structure enhances sensitivity through its unique polarization-induced 2DEG and intrinsic back barrier, while the Pd layer catalyzes H2 dissociation, forming a dipole layer that can modulate the Schottky barrier height. Experimental results demonstrate superior performance at both room temperature and elevated temperatures. Specifically, at 200 °C, the sensor exhibits a response of 102% toward 200 ppm H2, with response/recovery times of 150 s/17 s. This represents a 96% enhancement in sensitivity and a reduction of 180 s/14 s in response/recovery times compared to room-temperature conditions (23 °C). These findings highlight the potential of N-polar HEMTs for high-performance hydrogen sensing applications. Full article
(This article belongs to the Special Issue Recent Advances in III-Nitride Semiconductors and Correlated Wide Bandgap Semiconductors, 2nd Edition)
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16 pages, 5230 KiB  
Article
In Situ Capture of High-Temperature Precipitate Phases in Ti-48Al-2Cr-2Nb Alloy Using Convolutional Neural Networks
by Xiaolei Li, Chuanqing Huang, Sen Zhao, Linlin Cui, Shirui Guo, Bo Zheng, Yinghao Cui, Yongqian Chen, Yue Zhao, Lujun Cui and Chunjie Xu
Crystals 2025, 15(6), 577; https://doi.org/10.3390/cryst15060577 - 18 Jun 2025
Viewed by 205
Abstract
TiAl intermetallic alloy is a crucial high-performance material, and its microstructure evolution at high temperatures is closely related to the process parameters. Observing the lamellar structure is key to exploring growth kinetics, and the feature extraction of precipitate phases can provide an effective [...] Read more.
TiAl intermetallic alloy is a crucial high-performance material, and its microstructure evolution at high temperatures is closely related to the process parameters. Observing the lamellar structure is key to exploring growth kinetics, and the feature extraction of precipitate phases can provide an effective basis for subsequent evolution studies and process parameter settings. Traditional observation methods struggle to promptly grasp the growth state of lamellar structures, and conventional object detection has certain limitations for clustered lamellar structures. This paper introduces a novel method for high-temperature precipitate phase feature extraction based on the YOLOv5-obb rotational object detection network, and a corresponding precipitate phase dataset was created. The improved YOLOv5-obb network was compared with other detection networks. The results show that the proposed YOLOv5-obb network model achieved a precision rate of 93.6% on the validation set for detecting and identifying lamellar structures, with a detection time of 0.02 s per image. It can effectively and accurately identify γ lamellar structures, providing a reference for intelligent morphology detection of alloy precipitate phases under high-temperature conditions. This method achieved good detection performance and high robustness. Additionally, the network can obtain precise positional information for target structures, thus determining the true length of the lamellar structure, which provides strong support for subsequent growth rate calculations. Full article
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13 pages, 3003 KiB  
Article
Nematic Phases in Photo-Responsive Hydrogen-Bonded Liquid Crystalline Dimers
by Christian Anders, Muhammad Abu Bakar, Tejal Nirgude and Mohamed Alaasar
Crystals 2025, 15(6), 576; https://doi.org/10.3390/cryst15060576 - 18 Jun 2025
Viewed by 304
Abstract
We report on the preparation and characterization of a new family of hydrogen-bonded nematogenic liquid crystalline dimers. The dimers are supramolecular complexes that consist of a benzoic acid derivative, acting as the proton donor, featuring a spacer with seven methylene groups and a [...] Read more.
We report on the preparation and characterization of a new family of hydrogen-bonded nematogenic liquid crystalline dimers. The dimers are supramolecular complexes that consist of a benzoic acid derivative, acting as the proton donor, featuring a spacer with seven methylene groups and a terminal decyloxy chain, paired with an azopyridine derivative as the proton acceptor. The latter was either fluorinated or nonfluorinated with variable alkoxy chain length. The formation of a hydrogen bond between the individual components was confirmed using FTIR and 1H NMR spectroscopy. All supramolecules were investigated for their liquid crystalline behaviour via a polarized optical microscope (POM) and differential scanning calorimetry (DSC). All materials exhibit enantiotropic nematic phases as confirmed by X-ray diffraction (XRD) and POM investigations. The nematic phase range depends strongly on the degree and position of fluorine atoms. Additionally, the supramolecules demonstrated a rapid and reversible transition between the liquid crystal phase and the isotropic liquid state because of trans-cis photoisomerization upon light irradiation. Therefore, this study presents a straightforward approach to design photo-responsive nematic materials, which could be of interest for nonlinear optics applications. Full article
(This article belongs to the Special Issue Celebrating the 10th Anniversary of International Crystallography)
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22 pages, 661 KiB  
Article
Modeling Fatigue Data of Complex Metallic Alloys Using a Generalized Student’s t-Birnbaum–Saunders Family of Lifetime Models: A Comparative Study with Applications
by Farouq Mohammad A. Alam, Fouad Khalawi and Abdulkader Monier Daghistani
Crystals 2025, 15(6), 575; https://doi.org/10.3390/cryst15060575 - 18 Jun 2025
Viewed by 276
Abstract
The mechanical reliability of metallic alloys under cyclic loading is crucial for optimizing their microstructure–property relationships. Understanding the statistical behavior of fatigue failure data is essential for designing alloys that endure extreme environmental conditions. This study introduces a generalization of the Student’s t [...] Read more.
The mechanical reliability of metallic alloys under cyclic loading is crucial for optimizing their microstructure–property relationships. Understanding the statistical behavior of fatigue failure data is essential for designing alloys that endure extreme environmental conditions. This study introduces a generalization of the Student’s t-Birnbaum–Saunders distribution to improve the modeling of fatigue life data, which often exhibit heavy tails and are common in advanced alloy systems. Seven different estimation methods are employed to estimate and compare the parameters of the proposed distribution, providing a comprehensive statistical framework for fatigue failure analysis. The goodness-of-fit of the proposed model and its sub-models, along with the joint relative efficiency of parameter estimates, is assessed using real fatigue data within the maximum likelihood framework. Additionally, the robustness of estimation methods is examined through Monte Carlo simulations across various sample sizes and parameter configurations. The results highlight the effectiveness of the generalized Student’s t-Birnbaum–Saunders distribution in capturing the stochastic nature of fatigue failure in metallic alloys, offering valuable insights for materials design and predictive reliability modeling. These findings align with advancements in computational modeling and simulation, contributing to developing alloys with tailored mechanical properties. Full article
(This article belongs to the Special Issue Advances in Processing, Simulation and Characterization of Alloys)
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27 pages, 3716 KiB  
Article
Raman Characterization of Dioxygen Species as Defects in Single-Crystal ZnO Including Their Pressure Dependence
by Dieter Fischer, Dominik Bloos, Aleksandra Krajewska, Graham M. McNally, Dejan Zagorac and Johann Christian Schön
Crystals 2025, 15(6), 574; https://doi.org/10.3390/cryst15060574 - 18 Jun 2025
Viewed by 346
Abstract
The defects in zinc oxide crystals are of crucial importance for their usability in many applications and are not yet fully understood. Here, we demonstrate that dioxygen species are present as defects in the grown ZnO, resulting in a bending of the atom [...] Read more.
The defects in zinc oxide crystals are of crucial importance for their usability in many applications and are not yet fully understood. Here, we demonstrate that dioxygen species are present as defects in the grown ZnO, resulting in a bending of the atom layers that lie perpendicular to the c-axis. In the Raman spectra, these defects cause the appearance of bands different from the known bands of perfect ZnO crystals allowed by symmetry. These additional Raman bands, which have been frequently reported for ZnO in the past, can thus be fully explained by the presence of dioxygen species, and the widespread assumption of second-order modes for the assignments of these bands is not necessary. Furthermore, the Raman spectrum belonging to perfect zinc oxide in the ideal wurtzite structure is presented, obtained from small domains in ZnO(0001) crystals exposed to pressures up to 2 GPa. The dependence of the O-O stretching modes on the applied pressure proves the presence of dioxygen species in ZnO, which is also confirmed by phonon calculations of structure models with embedded dioxygen species. The surface quality of the ZnO crystals studied is also reflected in the Raman spectra and is included in the analysis. Full article
(This article belongs to the Section Inorganic Crystalline Materials)
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16 pages, 1496 KiB  
Article
Annealing of Oxygen-Related Frenkel Defects in Corundum Single Crystals Irradiated with Energetic Xenon Ions
by Kotomin A. Eugene, Ruslan Assylbayev, Guldar Baubekova, Irina Kudryavtseva, Vladimir N. Kuzovkov, Alise Podelinska, Viktor Seeman, Evgeni Shablonin and Aleksandr Lushchik
Crystals 2025, 15(6), 573; https://doi.org/10.3390/cryst15060573 - 18 Jun 2025
Viewed by 272
Abstract
The recovery of radiation damage induced by 231-MeV xenon ions with varying fluence (from 5 × 1011 to 2 × 1014 cm−2) in α-Al2O3 (corundum) single crystals has been studied by means of isochronal thermal annealing [...] Read more.
The recovery of radiation damage induced by 231-MeV xenon ions with varying fluence (from 5 × 1011 to 2 × 1014 cm−2) in α-Al2O3 (corundum) single crystals has been studied by means of isochronal thermal annealing of radiation-induced optical absorption (RIOA). The integral of elementary Gaussians (product of RIOA spectrum decomposition) OK has been considered as a concentration measure of relevant oxygen-related Frenkel defects (neutral and charged interstitial-vacancy pairs, F-H, F+-H−). The annealing kinetics of these four ion-induced point lattice defects has been modelled in terms of diffusion-controlled bimolecular recombination reactions and compared with those carried out earlier for the case of corundum irradiation by fast neutrons. The changes in the parameters of interstitial (mobile component in the recombination process) annealing kinetics—activation energy E and pre-exponential factor X—in ion-irradiated crystals are considered. Full article
(This article belongs to the Section Materials for Energy Applications)
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11 pages, 2022 KiB  
Article
Eu-Tb-Doped Y-BTC MOF: A Step Towards Optimization of an Energy Conversion System
by Francesca Lo Presti, Anna Lucia Pellegrino, Francesca Loschi, Emil Milan, Adolfo Speghini and Graziella Malandrino
Crystals 2025, 15(6), 572; https://doi.org/10.3390/cryst15060572 - 17 Jun 2025
Viewed by 348
Abstract
Lanthanide-based metal–organic frameworks (Ln-MOFs) represent a key material in various optical applications. Thus, they offer the possibility of fine-tuning their functional properties by adjusting the composition, stoichiometry, and ligand nature. This work reports for the first time the environmentally friendly one-pot synthesis of [...] Read more.
Lanthanide-based metal–organic frameworks (Ln-MOFs) represent a key material in various optical applications. Thus, they offer the possibility of fine-tuning their functional properties by adjusting the composition, stoichiometry, and ligand nature. This work reports for the first time the environmentally friendly one-pot synthesis of Eu-Tb-doped yttrium-1,3,5-benzenetricarboxylate MOF, i.e., Y-BTC: Eu (10%), Tb (10%), under mild conditions of temperature and pressure. Structural and morphological investigations were conducted through ATR-IR, XRD, and FE-SEM characterization. The doping percentage was analyzed by EDX spectroscopy. The luminescence properties confirm the down-shifting behavior of the MOF, paving the way for using this Eu-Tb-doped Y-BTC system in photovoltaic technology. Full article
(This article belongs to the Special Issue Crystalline Materials for Energy Conversion Applications in Solar Cells)
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23 pages, 9574 KiB  
Article
Optimization of Critical Parameters in Friction Stir Spot Welding of AA5052 Aluminum Alloy Using Response Surface Methodology
by Mohamed M. El-Sayed Seleman, Sabbah Ataya, Nashmi H. Alrasheedi, Mohamed M. Z. Ahmed, Hagar A. Reyad, Ashraf Bakkar and Ramy A. Fouad
Crystals 2025, 15(6), 571; https://doi.org/10.3390/cryst15060571 - 17 Jun 2025
Viewed by 395
Abstract
Understanding and optimizing the relationship between critical processing parameters (rotational speed and dwell time) and the resulting weld performance is crucial for the effective application of friction stir spot welding (FSSW) in joining aluminum alloys. FSSW is an increasingly important solid-state, clean technology [...] Read more.
Understanding and optimizing the relationship between critical processing parameters (rotational speed and dwell time) and the resulting weld performance is crucial for the effective application of friction stir spot welding (FSSW) in joining aluminum alloys. FSSW is an increasingly important solid-state, clean technology alternative for joining lightweight alloys such as AA5052-H32 in various industries. To optimize this technique for lap joint configurations, the current study examines the influence of rotational speeds (500, 1000, and 1500 rpm) and dwell times (1, 2, and 3 s) on the heat input energy, hardness across weld zones, and tensile/shear load, using a full factorial Design-Expert (DOE) analysis. The FSSW responses of the numerical model were validated using the experimental results for the spot-welded joints. The findings indicate that the dwell time significantly affected the mechanical properties, while the tool rotational speed had a substantial effect on the heat input energy and mechanical properties. Fracture surfaces predominantly exhibited ductile failure with diverse dimple morphologies, consistent with the enhanced tensile properties under optimal parameters. The presence of finer dimples suggests a mixed-mode fracture involving shear. Full article
(This article belongs to the Special Issue Advances in Processing, Simulation and Characterization of Alloys)
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15 pages, 2443 KiB  
Article
Thermally Stable Anilate-Based 3D CPs/MOFs
by Fabio Manna, Noemi Monni, Mariangela Oggianu, Juan Modesto Clemente-Juan, Miguel Clemente-León and Maria Laura Mercuri
Crystals 2025, 15(6), 570; https://doi.org/10.3390/cryst15060570 - 17 Jun 2025
Viewed by 242
Abstract
The synthesis and characterization of two novel redox-active MOFs/CPs based on 3d transition metal ions and 3,6-ditriazolyl-2,5-dihydroxybenzoquinone (trz2An) are reported herein. By combining trz2An with NiII and MnII ions via the hydrothermal method, two phases, formulated as [...] Read more.
The synthesis and characterization of two novel redox-active MOFs/CPs based on 3d transition metal ions and 3,6-ditriazolyl-2,5-dihydroxybenzoquinone (trz2An) are reported herein. By combining trz2An with NiII and MnII ions via the hydrothermal method, two phases, formulated as [Ni2(trz2An)2]·2.5H2O (1) and [Mn(trz2An)(H2O)]·1.5H2O (2), are obtained. Both compounds crystallize as neutral polymeric 3D frameworks, where the metal ions are coordinated through the oxygen atoms of the anilate linkers forming either straight (1) or zig-zag (2) 1D chains. In particular, (1) is a MOF, where these chains are connected through the nitrogen atom at the 4 position of the triazolyl group, which completes the coordination sphere of each metal ion, affording a 3D structure containing a void volume of 28.7% and voids that can be useful for the sorption of small molecules. Interestingly, (1) and (2) show a redox behavior due to the presence of the anilate linker, being reduced electrochemically in the −0.7 to −0.9 V range due to the benzoquinone–semiquinone one-electron reduction and magnetic behavior dominated by antiferromagnetic interactions in the anilate 1D chains. Full article
(This article belongs to the Section Macromolecular Crystals)
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23 pages, 3401 KiB  
Article
Modulation of Protein Dynamics by Glycerol in Water-Soluble Chlorophyll-Binding Protein (WSCP)
by Mina Hajizadeh, Maksym Golub, Inga Bektas, Leonid L. Rusevich, Jan P. Embs, Wiebke Lohstroh, Harald Paulsen and Jörg Pieper
Crystals 2025, 15(6), 569; https://doi.org/10.3390/cryst15060569 - 17 Jun 2025
Cited by 1 | Viewed by 251
Abstract
Proteins are inherently dynamic entities that rely on flexibility across multiple timescales to perform their biological functions. The surrounding environment plays a critical role in modulating protein dynamics by exerting plasticizing or stabilizing effects. In order to characterize the conformational dynamics of Water-Soluble [...] Read more.
Proteins are inherently dynamic entities that rely on flexibility across multiple timescales to perform their biological functions. The surrounding environment plays a critical role in modulating protein dynamics by exerting plasticizing or stabilizing effects. In order to characterize the conformational dynamics of Water-Soluble Chlorophyll-Binding Protein (WSCP), we measured Quasielastic Neutron Scattering (QENS) spectra over a wide temperature range between 100 and 300 K. The impact of glycerol, a common stabilizer, is investigated by comparing WSCP dissolved in a glycerol–water-containing buffer (WSCPW+G) with WSCP in a water-containing buffer (WSCPW). The results indicate that conformational protein dynamics are widely suppressed below 200 K but increase above this threshold, with the appearance of localized protein motions on the picosecond timescale. Glycerol appears to limit protein mobility between 280 and 300 K due to its high viscosity and hydrogen bonding in contrast to WSCP in water. Inelastic Neutron Scattering (INS) reveals the vibrational dynamics of WSCP with pronounced low-energy protein vibrations observed at about 2.5 and 6 meV. In the presence of glycerol, however, a stiffening of the vibrational motions which shifts the vibrational peaks to higher frequencies is observed. Full article
(This article belongs to the Section Biomolecular Crystals)
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16 pages, 3633 KiB  
Article
Time-Dependent Rheological Behavior of Surface-Coated Calcite Powder: Implications for Industrial Applications
by Orkun Ersoy, Harun Köse and Dilek Karapınar Güler
Crystals 2025, 15(6), 568; https://doi.org/10.3390/cryst15060568 - 17 Jun 2025
Viewed by 245
Abstract
In this study, the effects of stearic acid coating concentration (0.85%, 1%, and 1.15% wt.) and storage duration (up to 30 days) on the flow properties of surface-modified micronized calcite powder were investigated to evaluate their implications for critical industrial processes including transportation, [...] Read more.
In this study, the effects of stearic acid coating concentration (0.85%, 1%, and 1.15% wt.) and storage duration (up to 30 days) on the flow properties of surface-modified micronized calcite powder were investigated to evaluate their implications for critical industrial processes including transportation, feeding, dispersion, and production capacity. The results demonstrated that both stearic acid concentration and storage duration significantly influenced the rheological properties of the coated calcite powders, suggesting that the calcite surfaces had dynamic characteristics. The Conditioned Bulk Density (CBD) values increased significantly from day 1 to day 30, indicating efficient packing of the powders. Although stearic acid-coated calcite powders initially demonstrated enhanced flowability (SE: 5.1→3.7 mJ/g; BFE: 77→59.3 mJ) within the first 8 days, a subsequent increase (SE: 4.6 mJ/g; BFE: 74.3 mJ) by day 30 indicated a time-dependent surface reorganization of the coated particles. The reduction in the Flow Rate Index (FRI) values after a 30-day period indicated a decrease in cohesiveness. The stability index (SI) values initially indicated instability but improved after 30 days. These findings highlight the importance of considering the coating amount and time-dependent behavior when designing experiments, formulating products, and establishing quality control procedures involving calcite fillers. Full article
(This article belongs to the Special Issue Advanced Surface Engineering Materials: Characterization and Properties (2nd Edition))
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36 pages, 5287 KiB  
Review
Preparation, Properties, and Applications of 2D Janus Transition Metal Dichalcogenides
by Haoyang Zhao and Jeffrey Chor Keung Lam
Crystals 2025, 15(6), 567; https://doi.org/10.3390/cryst15060567 - 16 Jun 2025
Viewed by 770
Abstract
Structural symmetry significantly influences the fundamental characteristics of two-dimensional (2D) materials. In conventional transition metal dichalcogenides (TMDs), the absence of in-plane symmetry introduces distinct optoelectronic behaviors. To further enrich the functionality of such materials, recent efforts have focused on disrupting out-of-plane symmetry—often through [...] Read more.
Structural symmetry significantly influences the fundamental characteristics of two-dimensional (2D) materials. In conventional transition metal dichalcogenides (TMDs), the absence of in-plane symmetry introduces distinct optoelectronic behaviors. To further enrich the functionality of such materials, recent efforts have focused on disrupting out-of-plane symmetry—often through the application of external electric fields—which leads to the generation of an intrinsic electric field within the lattice. This internal field alters the electronic band configuration, broadening the material’s applicability in fields like optoelectronics and spintronics. Among various engineered 2D systems, Janus transition metal dichalcogenides (JTMDs) have shown as a compelling class. Their intrinsic structural asymmetry, resulting from the replacement of chalcogen atoms on one side, naturally breaks out-of-plane symmetry and surpasses certain limitations of traditional TMDs. This unique arrangement imparts exceptional physical properties, such as vertical piezoelectric responses, pronounced Rashba spin splitting, and notable changes in Raman modes. These distinctive traits position JTMDs as promising candidates for use in sensors, spintronic devices, valleytronic applications, advanced optoelectronics, and catalytic processes. In this Review, we discuss the synthesis methods, structural features, properties, and potential applications of 2D JTMDs. We also highlight key challenges and propose future research directions. Compared with previous reviews, this work focusing on the latest scientific research breakthroughs and discoveries in recent years, not only provides an in-depth discussion of the out-of-plane asymmetry in JTMDs but also emphasizes recent advances in their synthesis techniques and the prospects for scalable industrial production. In addition, it highlights the rapid development of JTMD-based applications in recent years and explores their potential integration with machine learning and artificial intelligence for the development of next-generation intelligent devices. Full article
(This article belongs to the Special Issue Structural Engineering of Low-Dimensional Materials for Desired Properties)
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14 pages, 2451 KiB  
Article
Mechanical and Electronic Properties of Fe(II) Doped Calcite: Ab Initio Calculations
by Zhangci Wu, Xiao Zhi, Fujie Jia, Jiayuan Ye and Neng Li
Crystals 2025, 15(6), 566; https://doi.org/10.3390/cryst15060566 - 16 Jun 2025
Viewed by 273
Abstract
Calcite (CaCO3), a widely used mineral in materials science and environmental engineering, exhibits excellent stability but has limited mechanical strength and a wide electronic band gap, restricting its broader functional applications. To address these limitations, we systematically investigated the effects of [...] Read more.
Calcite (CaCO3), a widely used mineral in materials science and environmental engineering, exhibits excellent stability but has limited mechanical strength and a wide electronic band gap, restricting its broader functional applications. To address these limitations, we systematically investigated the effects of Fe(II) doping on the electronic and mechanical properties of calcite using density functional theory calculations. The results reveal that Fe atoms preferentially form a layered distribution within the lattice and significantly alter the electronic structure, notably reducing the band gap through the introduction of Fe 3d-derived states near the Fermi level. Concurrently, the incorporation of Fe strengthens the elastic constants and enhances the shear resistance, especially in directions aligned with the dopant layering. These improvements are attributed to the strong Fe-O bonding and localized lattice distortions. Furthermore, the interplay between the dopant distribution and magnetic ordering suggests that spin polarization could serve as a potential handle for property tuning. This study highlights Fe-doped calcite as a promising candidate for functional mineral-based materials and provides theoretical insights into the magnetic and structural design of carbonate systems. Full article
(This article belongs to the Special Issue Design and Synthesis of Functional Crystal Materials)
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16 pages, 2624 KiB  
Article
Grain Size Engineering and Tuning of Magnetic Properties in Ultra-Thin NiMnGa Glass-Coated Microwires: Insights from Annealing Effects
by Mohamed Salaheldeen, Valentina Zhukova, Julian Gonzalez and Arcady Zhukov
Crystals 2025, 15(6), 565; https://doi.org/10.3390/cryst15060565 - 16 Jun 2025
Cited by 1 | Viewed by 289
Abstract
We studied the influence of annealing on the magnetic properties and microstructure of ultrathin (metallic nucleus diameter ≈ 5 μm, total diameter ≈ 19 μm) Heusler-type NiMnGa glass-coated microwires prepared using the Taylor–Ulitovsky method. The as-prepared NiMnGa microwires exhibit unexpectedly strong magnetic anisotropy, [...] Read more.
We studied the influence of annealing on the magnetic properties and microstructure of ultrathin (metallic nucleus diameter ≈ 5 μm, total diameter ≈ 19 μm) Heusler-type NiMnGa glass-coated microwires prepared using the Taylor–Ulitovsky method. The as-prepared NiMnGa microwires exhibit unexpectedly strong magnetic anisotropy, characterized by a coercivity exceeding 3 kOe at room temperature. Furthermore, their Curie temperature (Tc) lies above room temperature. Additionally, a spontaneous exchange bias of approximately 120 Oe is observed in the as-prepared sample at 100 K. Annealing the microwires leads to a decrease in coercivity, spontaneous exchange bias, and Tc values. Notably, the annealing process shifts the Tc of the samples closer to room temperature, making them more suitable for magnetic solid-state refrigeration applications. Moreover, the hysteresis observed in the temperature dependence of magnetization for the samples annealed for 1 h and 2 h, along with the magnetic softening observed at around 260 K, is attributed to a first-order phase transformation. The observed changes are discussed in the context of internal stress relaxation after annealing, the nanocrystalline structure of both the as-prepared and annealed samples, the recrystallization process, and the magnetic ordering of phases identified in the as-prepared sample and those appearing during recrystallization. The glass coating on microwires offers benefits like better flexibility and resistance to damage and corrosion. However, it is important to recognize that this coating can substantially alter the microwires’ magnetic characteristics. Consequently, precise control over the annealing process is vital to obtain the specific martensitic transformation needed. Full article
(This article belongs to the Special Issue Recent Advances in Microstructure and Properties of Metals and Alloys)
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15 pages, 2028 KiB  
Article
Physicochemical Properties of Demineralized Bone Matrix and Calcium Hydroxide Composites Used as Bone Graft Material
by Octarina, Florencia Livia Kurniawan, Firda Amalia Larosa, Olivia Nauli Komala and Meircurius Dwi Condro Surboyo
Crystals 2025, 15(6), 564; https://doi.org/10.3390/cryst15060564 - 15 Jun 2025
Viewed by 458
Abstract
Vertical bone defects can result in alveolar bone resorption, which may be addressed using composite grafts. A combination of demineralized bone matrix (DBM) and calcium hydroxide (Ca(OH)2) has potential as a bone substitute due to its biological and structural properties. This [...] Read more.
Vertical bone defects can result in alveolar bone resorption, which may be addressed using composite grafts. A combination of demineralized bone matrix (DBM) and calcium hydroxide (Ca(OH)2) has potential as a bone substitute due to its biological and structural properties. This study aimed to identify the optimal DBM–Ca(OH)2 ratio by evaluating their physicochemical properties relevant to bone regeneration. DBM gel and Ca(OH)2 powder were combined at ratios of 1:1, 2:1, 3:1, and 4:1. The mixtures were freeze-dried, ground, and sieved to create granules. The composites were analyzed in terms of their structural and chemical characteristics, including crystallinity, calcium ion release, functional group composition, particle size, surface morphology, and elemental distribution. Increasing the proportion of DBM reduced crystallinity and calcium ion release while influencing particle size. Among all groups, the 2:1 composite demonstrated the most balanced properties: moderate crystallinity, relatively high calcium release, and favorable particle size. Chemical analyses confirmed the presence and interaction of both organic and inorganic components, while elemental mapping showed a uniform distribution of the key elements essential for bone formation. The DBM–Ca(OH)2 composite at a 2:1 ratio has the most promising physicochemical profile, making it a strong candidate for bone graft applications. However, a limitation of this study is the absence of biological testing. Future research should investigate the in vitro and in vivo performance of this composite in bone regeneration. Full article
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11 pages, 2111 KiB  
Article
Nanoporous Copper Fabricated by Dealloying Single-Phase Mn-Cu-Al Alloy and Its Non-Enzymatic Glucose Detection
by Jinyi Wang, Bowen Fan, Jincheng Yu, Mengqiong Huang, Jiana Song, Zhaokun Yang and Yuan Ji
Crystals 2025, 15(6), 563; https://doi.org/10.3390/cryst15060563 - 14 Jun 2025
Viewed by 337
Abstract
Single-phase ternary Mn-Cu-Al alloy ribbons were fabricated by melt-spinning a Mn48Cu28Al24 ingot on a rotating copper roller. They were used as dealloying precursor for forming the nanoporous structure in HCl solution. The basic dealloying behavior was examined by [...] Read more.
Single-phase ternary Mn-Cu-Al alloy ribbons were fabricated by melt-spinning a Mn48Cu28Al24 ingot on a rotating copper roller. They were used as dealloying precursor for forming the nanoporous structure in HCl solution. The basic dealloying behavior was examined by controlling the dealloying time from 5 min to 180 min at 50 °C. Due to the active chemical property, Mn and Al elements are easily etched in acid solutions. Meanwhile, Cu elements retained and rearranged. A three-dimensional bicontinous nanoporous structure was fabricated, with a ligament size of 55 nm~100 nm and pore size of 35 nm~85 nm. The porosity evolution of dealloyed MnCuAl alloy was divided into three stages. First, the dissolution of Mn and Al is so significant that formation of pores is dominant. Stage two, the rapid growth of both ligament size and pore size. The ligament/pore ratio is nearly unchanged. The last stage is ligament coarsening. Moreover, the electrocatalytic activity for glucose oxidation of dealloyed samples is examined. The 40 min dealloyed MnCuAl ribbon exhibited the highest sensitivity and relatively maximum current density. Full article
(This article belongs to the Section Inorganic Crystalline Materials)
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15 pages, 3537 KiB  
Article
High-Efficiency Broadband Selective Photothermal Absorbers Based on Multilayer Chromium Films
by Chu Li, Er-Tao Hu, Yu-Xiang Zheng, Song-You Wang, Yue-Mei Yang, Young-Pak Lee, Jun-Peng Guo, Qing-Yuan Cai, Wei-Bo Duan and Liang-Yao Chen
Crystals 2025, 15(6), 562; https://doi.org/10.3390/cryst15060562 - 14 Jun 2025
Viewed by 328
Abstract
Photothermal conversion is a pivotal energy transformation mechanism in solar energy systems. Achieving high-efficiency and broadband photothermal conversion within the solar radiation spectrum holds strategic significance in driving the innovative development of renewable energy technologies. In this study, a transmission matrix method was [...] Read more.
Photothermal conversion is a pivotal energy transformation mechanism in solar energy systems. Achieving high-efficiency and broadband photothermal conversion within the solar radiation spectrum holds strategic significance in driving the innovative development of renewable energy technologies. In this study, a transmission matrix method was employed to design an interference-type solar selective absorber based on multilayer Cr-SiO2 planar films, successfully achieving an average absorption of 94% throughout the entire solar spectral range. Further analysis indicates that this newly designed absorber shows excellent absorption performance even at a relatively large incident angle (up to 60°). Additionally, the newly designed absorber demonstrates lower polarization sensitivity, enabling efficient operation under complicated incident conditions. With its simple fabrication process and ease of preparation, the proposed absorber holds substantial potential for applications in photothermal conversion fields such as solar thermal collectors. Full article
(This article belongs to the Special Issue Preparation and Characterization of Optoelectronic Functional Films)
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12 pages, 1740 KiB  
Article
Crystal Plasticity Finite Element Analysis of Spherical Nanoindentation Stress–Strain Curve of Single-Crystal Copper
by Haoming Xia, Zhanfeng Wang, Shichao Qu, Weijie Shan and Rongkai Tan
Crystals 2025, 15(6), 561; https://doi.org/10.3390/cryst15060561 - 13 Jun 2025
Viewed by 382
Abstract
In this paper, we perform crystal plasticity finite element (CPFE) simulations of spherical nanoindentation to extract the indentation stress–strain (ISS) curve for a single-crystalline copper. The load–displacement curves on the Cu (010) surface at incremental indentation depths are obtained. Surface pile-up topography is [...] Read more.
In this paper, we perform crystal plasticity finite element (CPFE) simulations of spherical nanoindentation to extract the indentation stress–strain (ISS) curve for a single-crystalline copper. The load–displacement curves on the Cu (010) surface at incremental indentation depths are obtained. Surface pile-up topography is explored and characterized by the activated slip systems on the indented surface and stress distribution on the cross-section to reveal the crystal anisotropy. And the effect of indentation depth on the stiffness and surface pile-up height is further analyzed. Finally, the zero point is defined, and the indentation stress–strain (ISS) curve is extracted from load–displacement curves. The validity of the ISS curve is demonstrated for crystalline copper materials by comparing measured results published in the literature. Full article
(This article belongs to the Special Issue Performance and Processing of Metal Materials)
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18 pages, 9592 KiB  
Article
Tribo-Mechanical Characteristics of Modified Cu-Cr-Zr Resistance Spot Welding Electrode with Nickel
by Ahmad Mostafa, Reham Alhdayat and Rasheed Abdullah
Crystals 2025, 15(6), 560; https://doi.org/10.3390/cryst15060560 - 13 Jun 2025
Viewed by 1802
Abstract
This study investigates the tribo-mechanical properties of a modified Cu-Cr-Zr alloy with nickel addition, aimed at enhancing its suitability as a resistance spot welding (RSW) electrode material. Two alloy compositions, designated as Sample A (Cu-0.871%Cr-0.156%Zr) and Sample B (modified with 8.94% Ni), were [...] Read more.
This study investigates the tribo-mechanical properties of a modified Cu-Cr-Zr alloy with nickel addition, aimed at enhancing its suitability as a resistance spot welding (RSW) electrode material. Two alloy compositions, designated as Sample A (Cu-0.871%Cr-0.156%Zr) and Sample B (modified with 8.94% Ni), were prepared. Microstructural examination revealed a coarse, mixed equiaxed–columnar grain structure in Sample A, while Sample B exhibited a refined dendritic morphology of about 50 μm PDAS, due to nickel-induced solute partitioning, improving microhardness from 72.763 HV to 83.981 HV. The wear behavior was evaluated using a pin-on-disc tribometer with a full factorial design, assessing the effects of rotational speed, load, and time on mass loss and surface roughness. Sample A exhibited increased mass loss and roughness with higher loads and speeds, indicating severe wear. In contrast, Sample B showed reduced mass loss and roughness at higher loads, suggesting a polishing effect from plastic deformation. Design of experiments analysis identified load as the dominant factor for mass loss in Sample A, with speed primarily affecting roughness, while in Sample B, load negatively influenced both responses, with speed–time interactions being significant. These findings highlight the nickel-modified alloy’s superior wear resistance and hardness, making it a promising candidate for RSW electrodes in high-production environments. Full article
(This article belongs to the Special Issue Advances in Metal Matrix Composites (Second Edition))
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15 pages, 4734 KiB  
Article
Hyaluronic Acid Dipeptide Gels Studied by Raman Spectroscopy
by Vlasta Mohaček-Grošev and Jože Grdadolnik
Crystals 2025, 15(6), 559; https://doi.org/10.3390/cryst15060559 - 13 Jun 2025
Viewed by 464
Abstract
This study presents a detailed Raman spectroscopic investigation of hydrogels composed of sodium hyaluronate and two N-terminally blocked dipeptides: N-acetyl-L-alanine-methyl-amide (NAcAlaNHMA) and N-acetyl-L-tyrosine-methyl-amide (NAcTyrNHMA). Vibrational spectra of the dipeptides in both crystalline and aqueous forms were analyzed and supported by density functional theory [...] Read more.
This study presents a detailed Raman spectroscopic investigation of hydrogels composed of sodium hyaluronate and two N-terminally blocked dipeptides: N-acetyl-L-alanine-methyl-amide (NAcAlaNHMA) and N-acetyl-L-tyrosine-methyl-amide (NAcTyrNHMA). Vibrational spectra of the dipeptides in both crystalline and aqueous forms were analyzed and supported by density functional theory (DFT) calculations. Spectral features of the hyaluronan component were elucidated by simulating the vibrational modes of its two principal disaccharide building blocks. Gels were prepared with varying dipeptide-to-hyaluronan ratios, and their structural characteristics were examined using Raman spectroscopy and atomic force microscopy. The results showed that while NAcAlaNHMA exhibited no significant interaction with the HA matrix, NAcTyrNHMA demonstrated specific binding behavior, as evidenced by notable shifts in its N–H and C–O–H vibrational bands. These findings indicate that NAcTyrNHMA binds to hyaluronic acid via hydrogen bonding, likely involving carboxyl and hydroxyl functional groups. This study highlights the potential for selective tuning of HA-based hydrogels using dipeptides, with implications for biomedical applications such as drug delivery, antimicrobial gels and biomaterial design. Full article
(This article belongs to the Section Biomolecular Crystals)
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21 pages, 4577 KiB  
Review
Recent Advances in Tantalum Carbide MXenes: Synthesis, Structure, Properties, and Novel Applications
by Mingfeng Li, Li Xu, Mengdi Guo, Hao Shang, Xiao Luo and Yanan Ma
Crystals 2025, 15(6), 558; https://doi.org/10.3390/cryst15060558 - 11 Jun 2025
Viewed by 759
Abstract
Tantalum carbide MXenes, notably Ta4C3Tx and Ta2CTx, exhibit distinctive physicochemical properties that distinguish them from the well-studied Ti3C2Tx MXene. The combination of exceptional electrochemical properties, efficient photothermal conversion, and [...] Read more.
Tantalum carbide MXenes, notably Ta4C3Tx and Ta2CTx, exhibit distinctive physicochemical properties that distinguish them from the well-studied Ti3C2Tx MXene. The combination of exceptional electrochemical properties, efficient photothermal conversion, and tunable surface terminations highlights the versatility of Ta-MXenes. These characteristics render them highly valuable for versatile applications. This minireview summarizes recent progress in tantalum carbide MXenes and their composites, focusing on applications in energy storage, conversion, sensing, and biomedicine. First, synthesis methods for tantalum carbide MXenes are summarized. Subsequently, their key properties are discussed, followed by a systematic review of diverse applications. Finally, this review offers a summary and outlook on the challenges and opportunities in the field of tantalum carbide MXenes research. Full article
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11 pages, 3461 KiB  
Article
Magnetotransport Measurements in Overdoped Mn:Bi2Te3 Thin Films
by Angadjit Singh, Varun S. Kamboj, Crispin H. W. Barnes and Thorsten Hesjedal
Crystals 2025, 15(6), 557; https://doi.org/10.3390/cryst15060557 - 11 Jun 2025
Viewed by 765
Abstract
Introducing magnetic dopants into topological insulators (TIs) provides a pathway to realizing novel quantum phenomena, including the quantum anomalous Hall effect (QAHE) and axionic states. One of the most commonly used 3d transition metal dopants is Mn, despite its known tendency to [...] Read more.
Introducing magnetic dopants into topological insulators (TIs) provides a pathway to realizing novel quantum phenomena, including the quantum anomalous Hall effect (QAHE) and axionic states. One of the most commonly used 3d transition metal dopants is Mn, despite its known tendency to be highly mobile and to cause phase segregation. In this study, we present a detailed magnetotransport investigation of Mn-overdoped Bi2Te3 thin films using field-effect transistor architectures. Building on our previous structural investigations of these samples, we examine how high Mn content influences their electronic transport properties. From our earlier studies, we know that high Mn doping concentrations lead to the formation of secondary phases, which significantly alter weak antilocalization behavior and suppress topological surface transport. To probe the gate response of these doped films over extended areas, we fabricate field-effect transistor structures, and we observe uniform electrostatic control of conduction across the magnetic phase. Inspired by recent developments in intrinsic topological systems such as the MnTe-Bi2Te3 septuple-layer compounds, we explore the influence of embedded ferromagnetic chalcogenide inclusions as an alternative route to engineer magnetic topological states and potentially expand the operational temperature range of QAHE-enabled devices. Full article
(This article belongs to the Special Issue Advances in Thin-Film Materials and Their Applications)
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55 pages, 20925 KiB  
Review
Current Trends and Emerging Strategies in Friction Stir Spot Welding for Lightweight Structures: Innovations in Tool Design, Robotics, and Composite Reinforcement—A Review
by Suresh Subramanian, Elango Natarajan, Ali Khalfallah, Gopal Pudhupalayam Muthukutti, Reza Beygi, Borhen Louhichi, Ramesh Sengottuvel and Chun Kit Ang
Crystals 2025, 15(6), 556; https://doi.org/10.3390/cryst15060556 - 11 Jun 2025
Cited by 1 | Viewed by 1784
Abstract
Friction stir spot welding (FSSW) is a solid-state joining technique increasingly favored in industries requiring high-quality, defect-free welds in lightweight and durable structures, such as the automotive, aerospace, and marine industries. This review examines the current advancements in FSSW, focusing on the relationships [...] Read more.
Friction stir spot welding (FSSW) is a solid-state joining technique increasingly favored in industries requiring high-quality, defect-free welds in lightweight and durable structures, such as the automotive, aerospace, and marine industries. This review examines the current advancements in FSSW, focusing on the relationships between microstructure, properties, and performance under load. FSSW offers numerous benefits over traditional welding, particularly for joining both similar and dissimilar materials. Key process parameters, including tool design, rotational speed, axial force, and dwell time, are discussed for their impact on weld quality. Innovations in robotics are enhancing FSSW’s accuracy and efficiency, while numerical simulations aid in optimizing process parameters and predicting material behavior. The addition of nano/microparticles, such as carbon nanotubes and graphene, has further improved weld strength and thermal stability. This review identifies areas for future research, including refining robotic programming, using artificial intelligence for autonomous welding, and exploring nano/microparticle reinforcement in FSSW composites. FSSW continues to advance solid-state joining technologies, providing critical insights for optimizing weld quality in sheet material applications. Full article
(This article belongs to the Special Issue Welding and Joining of Metallic Materials: Microstructure and Mechanical Properties, 2nd Edition)
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25 pages, 9151 KiB  
Article
Numerical Simulation and Metal Fluidity Analysis of Refill Friction Stir Spot Welding Based on 6061 Aluminum Alloy
by Di Jiang, Igor Kolupaev, Hongfeng Wang and Xiaole Ge
Crystals 2025, 15(6), 555; https://doi.org/10.3390/cryst15060555 - 10 Jun 2025
Viewed by 951
Abstract
Simulation analysis is a key technical means for studying the internal metal flow patterns in refill friction stir spot welding zones. This study used DeformV11.0 software to establish an accurate and reliable numerical simulation model for 6061-T6 aluminum alloy refill friction stir spot [...] Read more.
Simulation analysis is a key technical means for studying the internal metal flow patterns in refill friction stir spot welding zones. This study used DeformV11.0 software to establish an accurate and reliable numerical simulation model for 6061-T6 aluminum alloy refill friction stir spot welding. The microstructure of different stages during actual welding was obtained using the stop method, and combined with the simulation results, shows that the temperature in the spot welding zone is highest during the dwell stage, with a high degree of match between the temperature distribution and actual measurements. This stage is also crucial for affecting the refill process. The results indicate that the metal flow rate in the center of the spot welding zone is slow and the pressure is low, while the flow rate on both sides is fast, and the temperature and pressure are high. In addition, the metal in the weld zone flows plastically in a shear friction and in situ spinning manner, and the weld zone achieves connection in a form similar to “complete friction plug riveting”. A “spiral suction–refill injection layer stacking” model was established to describe the forming mechanism of refill friction stir spot welding. Full article
(This article belongs to the Special Issue Microstructure and Mechanical Behaviour of Structural Materials: 2nd Edition)
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14 pages, 1591 KiB  
Article
Synergistic Control of Liquid Crystallinity and Phosphorescence in Gold(I) Complexes via Strategic Alkyl Chain Design
by Arushi Rawat, Kohsuke Matsumoto, Ganesan Prabusankar and Osamu Tsutsumi
Crystals 2025, 15(6), 554; https://doi.org/10.3390/cryst15060554 - 10 Jun 2025
Viewed by 1132
Abstract
Liquid crystals exhibit unique properties that can be tailored in response to external stimuli. Significant research is directed toward the development of luminescent materials exhibiting liquid crystallinity for various applications. The present work reports Au(I) complexes featuring N-heterocyclic carbene and phenyl acetylide ligands. [...] Read more.
Liquid crystals exhibit unique properties that can be tailored in response to external stimuli. Significant research is directed toward the development of luminescent materials exhibiting liquid crystallinity for various applications. The present work reports Au(I) complexes featuring N-heterocyclic carbene and phenyl acetylide ligands. Metal complexes enable the utilization of the triplet excitons through their inherent spin–orbit coupling, promoting intersystem crossing from singlet (Sn) to triplet (Tn) states to observe room-temperature phosphorescence (RTP). The strong bonds between carbene and Au enhance the thermal stability, and the substituted benzimidazole ring alters the thermodynamic and photophysical properties of the complexes. Incorporating the acetylide ligands with long alkoxy chains led to the formation of liquid crystalline (LC) phases, which exhibited stability over a wide temperature range. Additionally, the luminescence behavior was affected by the ethynyl ligands, and high quantum yields of RTP were observed. This study establishes the development of LC Au(I) complexes with a thermodynamically stable LC mesophase over a wide temperature range for applications in the field of light-emitting functional materials. Full article
(This article belongs to the Special Issue State-of-the-Art Liquid Crystals Research in Japan (2nd Edition))
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