Crystals doi: 10.3390/cryst16050328

Authors: Rui Yao Rongrong Jia Zhenjie Feng

Crystallography is fundamental to elucidating the relationship between microscopic structure and macroscopic material properties, and its progress is closely associated with advances in computational tools and software. This review traces the development of crystallographic software from its origins in the 1960s at Oak Ridge National Laboratory to contemporary integrated platforms. The main aspects covered include the establishment and advancement of structural databases such as CSD and ICSD, the development of single-crystal structure determination programs such as SHELX and Olex2, and the evolution of powder diffraction tools, represented by HighScore Suite and TOPAS, toward integrated platforms. Crystallographic visualization tools have likewise evolved from desktop-based programs such as VESTA and Mercury to modern web-based platforms (JSmol and NGL Viewer). Moreover, we discuss the future directions of crystallographic software, including machine-readable data ecosystems, the application of artificial intelligence in structure determination and prediction, and the development of cloud-based immersive visualization platforms. Overall, this review comprehensively shows the evolution, current situation, and future directions of crystallographic software, which is of certain help to the research and development in related fields.

Crystals doi: 10.3390/cryst16050327

Authors: Xuezhi Wang Yunlin Li Yufu Liu Zhen Lai Yu Hang Xunya Jiang

Here we investigate the topological phase transition of a general one-dimensional (1D) disordered Su–Schrieffer–Heeger (SSH) model, with two tunable parameters, the disorder distribution center ξ and a dimensionless ratio k between the disorder strengths of the intracell and intercell hopping terms. First, for each realization or the ensemble average, we numerically observe a topological phase transition (TPT) with quantized real-space winding number jump and disappearing of zero-energy edge states when the disorder strength increases. Second, surprisingly, we find that the critical point of TPT is determined by the equality between the geometry means of intracell and intercell hopping terms. Third, a new theory based on the redefined sublattices is developed, which proves that the critical condition of TPT of the 1D disordered model is governed by the equality of the products of odd and even hopping terms and agrees with our numerical results. The theory also shows that the sudden change picture of TPT, not the gradual inverse picture, is correct, and that the origin of TPT is from the sub-symmetry of the model. Fourth, other models with different parameters are also studied. The TPTs of these models also follow our theoretical predictions. These results contribute to a better understanding of TPTs in 1D disordered systems.

Crystals doi: 10.3390/cryst16050326

Authors: Wael Z. Tawfik Hasnaa Hamdy Haifa A. Alqhtani Ahmed A. Allam Mohamed A. M. Ali Mohamed Sh. Abdel-wahab

In this study, zinc sulfide (ZnS) and manganese (Mn)-doped ZnS nanopowder were successfully prepared via a simple and cost-effective chemical precipitation method with various concentrations of Mn for use in UV photodetectors. The effects of Mn doping on the structural, morphological, and optoelectronic properties of ZnS nanopowder were studied. Structural analysis showed that all samples had a cubic structure with crystallite sizes approximately in the region of 2–3 nm. The morphological analysis using scanning electron microscopy confirmed the formation of well-dispersed spherical nanoparticles. Photoluminescence spectra show that Mn doping increased the luminescence intensity and caused a red shift in the emission peaks. Electrical properties such as conductivity and dielectric constant showed marked improvement with increasing Mn content. The conductivity increased from 3.7 mΩ−1·m−1 for pure ZnS to 6.3 mΩ−1·m−1 for the 1.03 mol% Mn2+ sample. The performance of photodetectors was evaluated under UV light. It was revealed that the photodetector based on a sample with 1.03 mol% Mn2+ reached an optimum state with an EQE of 9.8%, a detectivity of 4.65 × 109 Jones, and a responsivity of 3.64 × 10−2 A/W, indicating the effectiveness of Mn doping in improving the photo-generated carrier collection.

Crystals doi: 10.3390/cryst16050324

Authors: Yan Sun Yuankai Jiang Hongquan Zhang Xinggang Wang Weibin Jiang Meng Sun

Fe-Cr-based alloys have great potential for large-scale vibration and noise reduction. Appropriate heat treatment is important for improving their damping capacity. However, M23C6-type carbides are common grain boundary precipitates during the heat treatment process, and can affect both damping behavior and mechanical properties. In this work, the effects of Al content and annealing temperature on the microstructure, internal friction (IF), room temperature damping capacity, and tensile properties of Fe-15Cr-(0-4) Al (wt.%) alloys were investigated. When annealed at 800 °C, Al addition can suppress grain boundary precipitation, and no obvious intergranular precipitates were observed in the S2Al-S4Al alloys. The ultimate tensile strength also increased with Al addition, and the S4Al alloy exhibited a 34% higher strength than S0Al while retaining an elongation of 47.7%. The maximum damping value increased with Al addition. However, annealing at 1000 °C promoted continuous grain boundary carbide formation and reduced the elongation. These results indicate that the S4Al alloy annealed at 800 °C provides a favorable balance between damping capacity and mechanical properties.

Crystals doi: 10.3390/cryst16050325

Authors: Vasily Efremenko Yuliia Chabak Ivan Petrišinec Mikhailo Brykov Alexey Efremenko Mattia Franceschi Jerome Ingber Maik Kunert José Antonio Jimenez

The exploitation of advanced high-strength steels in cold climates requires a deep understanding of their structural stability and mechanical reliability. This study investigates the mechanical response of a 0.45C-1.57Si-2.61Mn (wt.%) steel with nanobainite microstructure to moderate sub-zero exposure (SZE) followed by stress-relief tempering. It was found that SZE at –25 °C and –50 °C induces a progressive degradation of tensile properties and impact toughness that persists after rewarming to room temperature. This deterioration is primarily driven by the accumulation of residual stresses due to thermal expansion mismatch between phases, with only minor contributions from athermal martensitic transformation of retained austenite. Notably, stress-relief tempering at 220 °C effectively restores the tensile performance and doubles the impact toughness compared to the as-austempered condition. Despite Mn and Si segregation which caused a scatter in retained austenite content (13.6–21.5 vol.%), the austenite remains stable throughout the SZE and tempering cycles. These results identify a critical threshold (between 0 °C and –25 °C) for SZE-induced degradation in nanobainitic steels and demonstrate that stress-relief tempering is essential for enhancing their performance in cold-climate applications.

Crystals doi: 10.3390/cryst16050323

Authors: Gal Bubnič Jorge L. Costafreda Domingo A. Martín

The Idrija mercury deposit represents one of the largest mercury formations globally, ranking second only to the Almadén deposit in Spain. The deposit has been exploited for more than five centuries and represents one of the most historically significant and extensively studied mercury mines worldwide. The Karoli orebody is characterized by a high abundance of pyrite (50 to 90 vol.% of the rock) and exceptionally rich cinnabar mineralization, with contents reaching up to 78 wt.% Hg locally. This study investigates the trace-element composition of Py3 pyrite from the Karoli orebody using LA-ICP-MS analysis to examine variations within Py3 pyrite, revealing insights into ore-forming processes and mineralization characteristics. Trace-element analysis of pyrite was performed and complemented by microscopic examination of thin sections. Three different pyrite types were identified: fine-grained framboidal Py1, subhedral to euhedral Py2, and larger, well-developed euhedral Py3. LA-ICP-MS analysis of Py3 pyrite grain revealed low trace-element contents, with maximum values remaining below 100 ppm. These observations, combined with published sulfur and mercury isotope data, suggest that Py3 pyrite crystallized under stable growth conditions from mercury-rich, low-salinity hydrothermal fluids. Our research provides insights into Py3 pyrite formation and the characteristics of the hydrothermal fluids in the Karoli orebody, serving as a solid foundation for further studies. Future research is envisioned to include the analysis of Py2 grains to complement the current dataset, with further investigations of fluid composition, salinity, and fluid inclusions.

Crystals doi: 10.3390/cryst16050322

Authors: Hu Guo Hui Huang Jingrun Luo Liling He Xicheng Huang Zhiming Hao

TATB (1,3,5-triamino-2,4,6-trinitrobenzene) crystals exhibit strong thermoelastic anisotropy, making crystallographic texture a key factor in the thermal-stress response of TATB-based polymer-bonded explosives (PBXs). In this study, computational micromechanics combined with statistical analysis is used to quantify thermal-expansion-induced internal stresses in TATB-textured PBXs at the mesoscale. The results show that the spatial distribution of internal stress is strongly influenced by grain misorientation between neighboring grains, with larger misorientations leading to more severe stress concentrations. Statistical analysis further reveals that the internal stress distributions are generally asymmetric and unimodal. As texture intensity increases, the probability density peak rises, whereas both the mode stress and the average stress decrease. The maximum-to-minimum ratios of these three statistical characteristics reach up to 5.8, 8.9, and 6.1, respectively, indicating that texture intensity can regulate the stress field over a broad range. Gaussian mixture modeling is further employed to characterize the probability distributions of three stress measures. The distribution of maximum principal stress can be adequately described using two Gaussian components, whereas the von Mises and Tresca stress distributions require three components. These findings provide a quantitative basis for understanding and mitigating thermoelastic internal stress in PBXs through texture tailoring.

Crystals doi: 10.3390/cryst16050321

Authors: Yulong Zhao Lan Yu Bin Liu

High-performance full-color displays and white lighting require stable and efficient red, green, and blue emitters; however, they are often limited by wide bandgaps, imbalanced carrier injection/transport, complex device structures, and high material costs. To address these challenges, we designed and synthesized a multifunctional deep-blue molecule (PPI-F-PO) integrating a phenanthroimidazole moiety, a 9,9-diphenylfluorene unit, and a phosphine oxide group. The twisted structure of fluorene, featuring a sp3-hybridized carbon, effectively suppresses conjugation extension and aggregation-caused quenching, whereas the electron-withdrawing phosphine oxide group enhances electron transport. Consequently, it exhibits good thermal stability, high solid-state photoluminescence quantum yield (58.8%), and high triplet energy (ET = 2.54 eV). Non-doped blue OLEDs based on this emitter achieve a maximum external quantum efficiency (EQE) of 2.52% with deep-blue CIE coordinates of (0.16, 0.06). Moreover, using this material as a host, green and orange-red phosphorescent OLEDs exhibit maximum EQEs of 15.4% and 9.7%, respectively, along with low efficiency roll-off. This work demonstrates that a bipolar deep-blue emitter with high triplet energy can act both as a high-efficiency standalone emitter and as a universal host for lower-energy phosphors, thereby simplifying device architecture and reducing material costs for full-color OLEDs.

Crystals doi: 10.3390/cryst16050320

Authors: Shulin Gong Yan Li Yanchun Li Meihui Song Yu Zhang Ye Kuang Changyao Gui

TC4 alloy samples were fabricated via selective laser melting (SLM) under different process parameters. The effects of scanning speed and build orientation on the microstructure and corrosion behavior were systematically investigated using optical microscopy (OM), scanning electron microscopy (SEM), electron backscatter diffraction (EBSD), X-ray diffraction (XRD), and electrochemical measurements. The results show that when increasing scan speed, TC4 alloy consists primarily of α/α’ phases with a minor amount of β phase, along with grain refinement and a higher fraction of low-angle grain boundaries. In 3.5% NaCl solution, the XOY-oriented sample processed at 1000 mm s−1 exhibited higher impedance and formed a stable, highly protective passive film. In simulated body fluid, the XOY orientation at 1200 mm s−1 displayed a larger capacitive arc, indicating superior corrosion resistance. These findings demonstrate that the corrosion performance of SLM-processed TC4 alloy can be optimized for specific service environments by tailoring both process parameters and build orientation.

Crystals doi: 10.3390/cryst16050319

Authors: Cristiano Lo Pò Francesco Ruffino Simona Filice Silvia Scalese Maria Grazia Grimaldi Stefano Boscarino

The Oxygen Evolution Reaction (OER) is the bottleneck in the water splitting reaction since it involves four intermediate steps, constituting the adsorption–desorption of oxygen-based radical groups, and not all of them are energetically favorable. Rapidly growing research interest is focusing on carbon-based materials as novel, highly active and durable non-precious electrocatalysts for the OER, representing a valuable alternative to precious and rare materials with electrochemical properties tuned by defect creation. In this work, we propose a facile and green methodology based on the modification of graphene oxide by laser irradiation to obtain an alternative OER catalyst. GO flakes were chemically and physically modified using pulsed laser irradiation at 532nm with fluences of 1.5J/cm2 and 2.5J/cm2. Different analyses were carried out to correlate the electrochemical performance with the structural, optical, and morphological properties; after that, we correlated the improvements in the OER with respect to the pristine GO with the increase in OH functional groups obtained by laser treatment. The best-performing sample exhibited an overpotential of 380mV, comparable to that of catalysts reported in the literature but with the advantage of not being a precious or rare material.

Crystals doi: 10.3390/cryst16050318

Authors: Yanqiang Lu Haowei Fu Chenhao Wen Jiaqi Wu Jian Guo

This study investigates nanoscale material removal behavior and its correlation with subsurface damage of (100)-oriented β-Ga2O3 subjected to single-point diamond scratching across a range of normal loads. Using multi-scale characterizations, we elucidate the load-dependent transition from elastic deformation to plasticity-dominated removal and, ultimately, to brittle fracture. Under low-load conditions, β-Ga2O3 exhibits a fully plasticity-dominated removal mechanism, characterized by smooth groove formation with surface pile-up and a crack-free subsurface containing only dislocations and stacking faults, suggesting that ductile-regime processing is achievable under appropriate mechanical conditions. As the normal load increases, the material enters a ductile–brittle transition regime, where plastic flow coexists with the initiation of micro shear cracks, accompanied by unstable fluctuations in the friction coefficient. Under high-load conditions, extensive brittle fracture becomes dominant, characterized by severe subsurface mixed cracking and large-scale material spalling. This research contributes to a deeper understanding of the machinability of β-Ga2O3 materials with high hardness and brittleness in ultraprecision surface processing.

Crystals doi: 10.3390/cryst16050317

Authors: Xianrui Jian Longfeng Lv Yuxiao Zou Guofeng Song Bo Cheng Wang Xiaoming Zhang Xiujun Kunpeng Zhai Hanxiao Shao

Circular dichroism is at the core of chiral spectroscopy and polarization light manipulation. However, achieving metal-based devices with high efficiency, compactness, and easy integration in the near-infrared band remains a significant challenge. Traditional metal chiral microstructures, such as broken open rings, helical lines, or waveplates–polarizers I confirm., are limited to circular dichroism values below 50% due to their inherent ohmic losses, severely restricting practical applications. To overcome this bottleneck, this paper proposes a twisted double-layer plasmonic metasurface composed of two anisotropic metal metasurfaces. This design breaks the mirror symmetry of the structure by precisely controlling the in-plane twist angle between the layers, inducing strong coupling and interference effects in the chiral optical response. Simulation results show that this device achieves excellent multi-wavelength circular dichroism control. At a wavelength of 1660 nm, the circular dichroism value reaches 0.48, and it further increases to 0.84 at 2200 nm, significantly surpassing the performance limits of traditional metal structures. This work not only provides a simple and scalable design paradigm for high-performance chiral optical devices but also opens up new avenues for advanced applications such as chiral molecular sensing, polarization coding, and quantum optics in the near-infrared band.

Crystals doi: 10.3390/cryst16050316

Authors: Wael Awadh Muhammad Abdullah Kamran Atheer Abdulhade Ganem Afnan Mohammed Alasmari Shan Sainudeen Ibrahim Alshahrani

This study aimed to assess how various remineralizing agents affect the demineralized enamel calcium/phosphorus ions (Ca/P) ratio and micro-tensile bond strength (μTBS) of orthodontic adhesive modified by Sepiolite nanoparticles (Sep-NPs). In addition, rheological properties and degree of conversion (DC) of the adhesive were investigated. One hundred and forty-four human premolars underwent a cariogenic challenge to induce artificial demineralization. Based on the remineralizing agents used, the samples were divided into four categories: silver diamine fluoride (SDF), rosmarinic acid (RMA), ROCS Medical Mineral Gel System (ROCS MMG), and control. The Ca/P ratio was evaluated using energy-dispersive X-rays. Thirty samples were divided into two subgroups: unmodified adhesive and 1% Sep-infiltrated adhesive. Brackets were bonded, and the μTBS was evaluated. Scanning electron microscopy was used to evaluate the resin–bracket interface. The modified and unmodified adhesives were subjected to DC and rheological testing. The Ca/P ion ratio was highest in the ROCS-MMG group and lowest in the no-remineralization group. Group 3B (ROCS MMG + SepNPs-Orthodontic adhesive) samples displayed the highest bond strength. The lowest μTBS was observed in Group 4A (no remineralization + orthodontic adhesive). ROCS MMG conferred the greatest improvement in µTBS and Ca/P ratio before bracket bonding, followed by SDF, whereas RMA did not enhance bonding outcomes. Sep-NP incorporation at 1% improved µTBS but compromised DC and rheological properties, necessitating concentration optimization before clinical application.

Crystals doi: 10.3390/cryst16050315

Authors: Anton Turygin Mikhail Kosobokov Semion Melnikov Vladimir Shur

The formation and growth of isolated domains during local switching by a biased tip of a scanning probe microscope in a (100) cut of a bismuth titanate Bi4Ti3O12 single crystal were studied experimentally. The as-grown domain structure consists of two domain types: a-type (out-of-plane) and b-type (in-plane). Local switching of the a-type domain area leads to anisotropic growth of a hexagonal a-type domain (a-a switching) with 180° walls. The dependence of the domain size on the pulse duration during domain growth along the b-axis was considered in terms of the anisotropic current-limited domain wall motion. Local switching of the b-type domain area leads to formation of a hexagonal a-type domain (b-a switching) with 90° walls increasing in size linearly with the applied voltage. The dependence of the domain size on the pulse duration was measured over a wide range of humidities. The increase in the domain size at moderate humidity is attributed to the effect of the water meniscus. The decrease in the domain size at high humidity is attributed to backswitching under the action of the residual depolarization field, facilitated by a conductive water layer on the side surfaces of the sample. The obtained results provide useful insights into the domain kinetics of ferroelectrics with C2 symmetry and can pave the way for the development of domain engineering techniques. The obtained results establish a direct relationship between local switching kinetics, crystallographic anisotropy, and environmental conditions. This provides the scientific community with a new framework for understanding domain wall motion in multiaxial ferroelectrics, which is essential for the development of stable and reliable domain-engineered devices.

Crystals doi: 10.3390/cryst16050314

Authors: Alexandra Pop Cristian Silvestru Lucian Cristian Pop Levente Kiss

The reaction of (3-py)2Hg (1) with Cu(OAc)2·H2O, in a 1:2 molar ratio, afforded the isolation of [(3-py)2Hg{Cu2(OAc)4}]n (2). This new bimetallic coordination polymer based on copper(II)- and mercury(II)-containing building blocks was characterized by an elemental analysis, IR and UV-Vis spectroscopies, a thermogravimetric analysis, and powder X-ray diffraction. For comparison, the UV-Vis properties of solid 1 are also reported. The structure of both 1 and 2 were established by single-crystal X-ray diffraction. The structural analysis of 2 shows a zig-zag 1D chain with alternating (3-py)2Hg molecules and Cu2(OAc)4 fragments connected via N → Cu coordinative bonds. Further interchain Hg···O, H···π, and π···π interactions support a 2D layer of zig-zag chains.

Crystals doi: 10.3390/cryst16050313

Authors: Obaidullah Alfahmi Mahmoud A. Alzahrani Mohamed A. Afifi Ahmed O. Mosleh Essam B. Moustafa

Aluminum alloy (AA5083) is widely used in the aerospace and marine industries. However, its use is sometimes limited by its low surface hardness, wear resistance, and thermal stability. The microstructural, mechanical, tribological, and dynamic behavior of AA5083 matrix composites incorporated with mono-reinforcements (hexagonal boron nitride (hBN), graphene (G), and carbon nanotubes (CNTs)) and hybrid reinforcements (hBN+CNTs, G+hBN, and CNTs+G) by friction stir processing (FSP) is thoroughly investigated. Microstructural examination demonstrated that extensive dynamic recrystallization was induced by FSP, reducing the base-metal grains (about 215 μm) to very small sizes. The hybrid hBN+CNT composite had the smallest grain size (about 4.5 μm), the mono-CNT composite had the highest microhardness (~60 HV), whereas the hybrid CNTs+G composite had the highest ultimate compressive strength (~350 MPa). This enhancement was attributed to the formation of a 3D network within the hybrid composite, which hindered graphene agglomeration and restacking. Tribological tests revealed that hybridization greatly reduced wear; in particular, hBN-containing hybrids (hBN+CNTs and hBN+G) had the lowest wear rates (~0.037 mg/bar.min), owing to hBN’s solid-lubrication effect. Moreover, dynamic mechanical analysis and free-vibration testing showed the tunability of vibrational characteristics; the mono-CNT composite had the greatest structural stiffness (storage modulus ~72.75 GPa), whereas the G+CNTs hybrid had the best damping ratio (damping ratio ~4.82%). These results demonstrate that hybrid nanoreinforcements can tailor the multifunctional characteristics of AA5083 composites.

Crystals doi: 10.3390/cryst16050312

Authors: Yingyuan Luo Qi Xu Lei Zhu Xueliang Zhang

A homemade NiCr/NiSi thin-film thermocouple integrated with a PCBN turning tool was developed for real-time temperature monitoring during dry turning of AISI 1045 steel. The study addresses a practical limitation of existing cutting-temperature methods, namely the difficulty of combining local in situ sensing near the cutting edge with a transient thermal analysis framework that can interpret the measured signal under repeatable cutting conditions. The sensor was fabricated on an Al2O3 substrate by magnetron sputtering, protected by a SiO2 layer, and tested at cutting speeds corresponding to spindle speeds of 1000, 1500 and 2000 rpm, with a cutting depth of 0.5 mm, a feed rate of 0.1 mm/rev and cutting times of 30–90 s. A three-dimensional transient heat-conduction model and inverse heat-flux reconstruction were then used to interpret the temperature history. The maximum measured temperature increased from 342 °C to 488 °C, and VB increased from 0.082 mm to 0.295 mm, showing a strong temperature–wear association within the investigated parameter window.

Crystals doi: 10.3390/cryst16050311

Authors: Grazia Giuseppina Politano

Spectroscopic ellipsometry (SE) is a non-destructive optical technique widely used to extract film thickness, optical constants, surface roughness, and compositional information. Despite its versatility and high sensitivity, conventional SE analysis typically relies on iterative nonlinear regression of parameterized optical models, which is computationally demanding, strongly dependent on expert intervention, and often affected by convergence and non-uniqueness issues. In recent years, artificial intelligence (AI) has emerged as a promising route to overcome these limitations. This review summarizes recent advances in AI-driven ellipsometry, spanning traditional machine learning (ML) methods, such as artificial neural networks (ANNs), support vector regression (SVR), and support vector machines (SVMs), as well as deep learning (DL) architectures, including convolutional neural networks (CNNs). Representative applications in semiconductors, perovskites, and biosensing are also discussed. Overall, this review highlights the opportunities and current limitations of AI for next-generation ellipsometric characterization.

Crystals doi: 10.3390/cryst16050310

Authors: Mohammed Saleh Alshaikh

The commercialization of perovskite solar cells (PSCs) hinges on replacing toxic lead-based absorbers with environmentally benign alternatives while maintaining competitive power conversion efficiencies (PCE). However, the enormous parameter space governing lead-free device architectures—spanning absorber thickness, defect density, doping concentration, and charge transport layer (CTL) selection—renders traditional trial-and-error optimization impractical. This paper introduces PerovskiteOpt-AI, a machine learning (ML)-driven multi-parameter optimization framework that integrates SCAPS-1D device simulation with Gaussian process (GP) surrogate modeling and Bayesian optimization (BO) to systematically identify high-efficiency lead-free PSC configurations. A synthetic dataset of 12,000 device-level simulations generated for the FTO/WS2/CsSnI3/CuSCN/Au architecture by varying eight critical parameters. An ensemble of ML models—random forest (RF), XGBoost, and GP regression (GPR)—is trained and benchmarked, with XGBoost achieving an R2 of 0.9987 and RMSE of 0.041% for PCE prediction. The GP surrogate is then coupled with a BO loop employing expected improvement (EI) acquisition to navigate the design space, converging on an optimized PCE of 27.83% ± 0.21% within 150 iterations—a 38.6% relative improvement over the baseline. Shapley additive explanations (SHAP) analysis reveals that absorber defect density and perovskite thickness are the dominant efficiency drivers, while conduction band offset at the ETL/absorber interface governs open-circuit voltage. The proposed framework reduces the computational cost of full-factorial parametric sweeps by over 95%, establishing a scalable paradigm for accelerated, interpretable design of next-generation lead-free consumer-grade photovoltaic devices.

Crystals doi: 10.3390/cryst16050309

Authors: Hailin Guo Dasen Wang Shiyan Zhao Chaoxiang Xia Ning Pei

To address the issues of heat accumulation and potential thermal damage during radio-frequency (RF) ion beam machining of KDP crystals, an energy deposition model and a temperature field model were developed based on Sigmund’s sputtering theory, a Gaussian beam distribution model, and heat conduction theory. Combined with the Monte Carlo method, the effects of incident energy, incident angle, and ion species on the disturbed layer depth and sputtering yield were systematically investigated. Furthermore, the influences of beam divergence angle and deflection angle on the surface energy deposition density distribution were analyzed. On this basis, the evolution of the temperature field and thermal stress field in KDP crystals under both stationary and linearly moving Gaussian surface heat sources was numerically simulated. The results indicate that the proposed model can effectively characterize the thermal response during ion beam machining of KDP crystals. The disturbed layer depth, sputtering yield, and energy deposition density distribution exhibit pronounced sensitivity to processing parameters. Under a stationary heat source, significant local heat accumulation and stress concentration tend to occur on the material surface. In contrast, a moving heat source can mitigate excessive temperature rise at a single location to some extent, although it also produces a heat-affected zone extending along the scanning path. These findings provide a theoretical basis for the optimization of low-damage RF ion beam machining parameters for KDP crystals.

Crystals doi: 10.3390/cryst16050308

Authors: Stanislav Kurajica Katarina Mužina Ana Petračić

The synthesis of a manganese-doped α-alumina pink pigment via the spray drying technique was explored. Three samples were prepared: pure α-alumina and two doped variants, where 3 and 6% of aluminum were substituted with manganese. The materials were analyzed using differential thermal and thermogravimetric analysis, X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray spectroscopy, and UV-Vis reflectance spectroscopy. Calcination at 1000 °C resulted in α-alumina with minor traces of hausmannite. The incorporation of manganese into the α-alumina crystal lattice was confirmed through lattice constant calculations and EDS. Higher-temperature treatments eliminated hausmannite but led to the formation of manganese aluminate. Washing the samples with hot concentrated hydrochloric acid removed hausmannite, unveiling the desired pink coloration.

Crystals doi: 10.3390/cryst16050307

Authors: Ye Yuan Yihua Sun Dong Zhang Sheng Liu Xiaopeng Jia Liao Lu Hongwei Lin Haoxiang Zhang

Nickel nanoparticles were synthesized via liquid-phase reduction of NiCl2·6H2O with N2H4·H2O. The efficacy of different dispersing agents in preventing agglomeration was systematically compared, establishing a clear processing-dispersion correlation. Four different types of dispersants were selected to compare their effects on the microstructure and dispersibility of nano nickel powder. Among them, Ni nanoparticles prepared using sodium dodecyl sulfate (SDS) as dispersants exhibit superior microscopic morphology and dispersion. And then, the mass ratio between the precursor and dispersant was systematically optimized, resulting in spherical nickel nanoparticles with controllable particle size and favorable physical properties. When the mass ratio of SDS to Ni salt reached 150%, the prepared spherical Ni nanoparticles had the optimal dispersion and a minimum average particle size of 79 ± 12 nm. By estimating Nv, the concentration of nickel nanoparticles is about 2.15 × 1017 particles cm−3 at this ratio. After thermal treatment, the quality of the samples became stable beyond 415 °C with a maximum weight reduction of 6.75% at 150% SDS/Ni-salt ratio, and no residual surface sulfur was detected. The saturation magnetization of Ni nanopowders gently decreased with decreasing dispersant content from 35.3 emu·g−1 to 31.6 emu·g−1 at 300 K, while soft ferromagnetic behavior was maintained, which is more beneficial for the stability of multilayer ceramic capacitor performance.

Crystals doi: 10.3390/cryst16050306

Authors: Catalin N. Marin Madalin O. Bunoiu Paula Sfirloaga Iosif Malaescu

An aluminum-doped NaTaO3 perovskite sample was prepared by the ultrasonic method, employing an immersed sonotrode, followed by thermal treatment at 600 °C for 6 h in air. X-ray diffraction analysis reveals a biphasic system with relatively low crystallinity, consisting of a dominant NaTaO3 perovskite phase and a secondary Na2Ta4O11 phase. Optical investigations indicate a reduced band gap energy of 3.77 eV compared to undoped NaTaO3 (4 eV), suggesting enhanced absorption toward the infrared region and improved photocatalytic potential. Fourier Transform Infrared FTIR Spectroscopy highlights the emergence of a distinct absorption band at 670 cm−1, attributed to Ta–O and Al–O stretching vibrations, evidencing successful incorporation of Al dopants. Complex impedance analysis over the frequency and temperature ranges of (20 Hz–2 MHz) and (29–100) °C identifies, for the first time, the semiconductor–conductor transition temperature at 58 °C. Nyquist analysis further supports the coexistence of grain and grain boundary contributions, modeled via equivalent R and CPE parallel circuits. Conductivity studies confirm obedience to Jonscher’s universal law, with a change in σDC slope near 54 °C, corroborating semiconductor–conductor transition behavior. Dielectric measurements similarly indicate a relaxation process linked to interfacial polarization, with a transition temperature of (~54 °C). Overall, the ultrasonic synthesis route uniquely enables a biphasic structure that facilitates the observation of a low-temperature semiconductor-to-conductor transition, absent in analogous single-phase materials obtained via sol–gel methods.

Crystals doi: 10.3390/cryst16050305

Authors: Rui Ding Kewang Tang Yuan Fang Oleksandr Ivasenko

Diacetylene monomers are known to undergo solid-state 1,4-addition polymerization when their crystal packing satisfies strict geometric criteria; however, the influence of bulky terminal protecting groups on the lattice adjustments required for bond formation remains insufficiently understood. Here, we synthesized amide derivatives of 2,4-hexadiyne-1,6-diamine, crystallized them via antisolvent vapor diffusion, and evaluated their thermal and photochemical reactivity. Single-crystal analysis shows that Boc-protected monomers (Boc-DA) form hydrogen-bond-directed parallel stacks that align diyne units in geometries nominally consistent with topochemical polymerization, yet they exhibit negligible photoreactivity under ambient UV irradiation. Structural inspection indicates that steric congestion from the tert-butoxycarbonyl termini restricts the subtle axial contraction and molecular shifts required for bond formation. Reducing steric bulk or applying combined thermal and photochemical activation enables polymerization of these diacetylenes. These findings demonstrate that globally favorable packing arrangements can coexist with local steric barriers that impose kinetic constraints on reactivity. Modulating terminal-group size and applying multimodal activation therefore provide a simple and tunable strategy to control diacetylene polymerization, offering design principles for switchable polydiacetylene materials in crystal engineering.

Crystals doi: 10.3390/cryst16050304

Authors: Rostislav Králík Barbora Kihoulou Lucia Bajtošová Tomáš Krajňák Miroslav Cieslar

Rapid solidification by melt-spinning produces aluminum alloys with extremely refined microstructures but also introduces strong structural gradients across the ribbon thickness. In this work, the microstructural evolution of a rapidly solidified Al-Cu-Li-Mg-Sc-Zr alloy was investigated during model homogenization using in situ STEM heating experiments and correlated with bulk electrical-resistivity measurements. The as-cast ribbons exhibit two distinct solidification zones: a near-contact region consisting of columnar cells containing fine Cu-rich spherical precipitates, and a central region composed of larger eutectic cells enriched in Al2Cu and Al7Cu2Fe phases. Stepwise in situ STEM annealing between 200 °C and 500 °C reveals a sequence of transformations, including matrix depletion due to precipitation of strengthening phases, coarsening of primary phases, and formation of Al3(Sc,Zr) dispersoids. Above 500 °C, rapid dissolution of Cu-rich primary phases occurs, leaving only a limited number of stable grain-boundary particles of the Al7Cu2Fe phase, eliminating the original two-zone structure, and resulting in a fully homogenized ribbon. Ex situ annealing confirms that the resulting microstructure is uniform across the ribbon thickness and enables consistent precipitation strengthening during artificial aging. The proposed annealing treatment is based on numerical models for homogenization of eutectic systems. The final annealing step combines homogenization and solution treatment at 530 °C for periods close to 5 min—two orders of magnitude shorter than standard holding times. Microhardness measurements from both ribbon surfaces reveal an identical peak-aged hardness of 135 HV, validating the effectiveness of the short-time homogenization strategy for rapidly solidified Al-Cu-Li-Mg-based alloys.

Crystals doi: 10.3390/cryst16050303

Authors: Jiayue Xu Ming Xi Dong Zhang Chenkai Fang Dahuai Zheng Hongde Liu Yaoqing Chu Hui Shen Tian Tian

A series of Hf co-doped uranium-doped lithium niobate (LN:U,Hf) crystals with a diameter of one inch were grown by the modified Bridgman method. XPS analysis showed that U ions coexist in mixed valence states of U4+, U5+, and U6+. At 442 nm, LN:U,Hf1.0 exhibited a fast photorefractive response of 0.32 s together with a high saturation diffraction efficiency of 82.01%. With increasing Hf concentration, the optical damage resistance was significantly enhanced, and LN:U,Hf5.0 achieved an optical damage threshold of 2.8 × 105 W/cm2. Two-beam coupling experiments indicated that electrons are the dominant charge carriers and diffusion is the main transport mechanism. It demonstrates that co-doping Hf4+ provides an effective route to simultaneously enhance photorefractive response and optical damage resistance in LN:U, offering potential for high-power and fast-response photonic devices.

Crystals doi: 10.3390/cryst16050302

Authors: Mariya Aleksandrova Svetozar Andreev

This paper investigates the stability of perovskite films under bonding conditions, focusing on the impact of bonding temperature on the electrical, morphological, and elemental characteristics of perovskite solar cells (PSCs) incorporating a barium–strontium titanate (BST) barrier layer. This study aimed to elucidate the interdiffusion phenomena at interfaces and their effect on device performance. We found that increasing the bonding temperature significantly degrades PSC performance, with efficiencies dropping from 21% at 100 °C to 65% at 180 °C relative to unbonded devices. A critical bonding temperature of 150 °C was identified, which correlates with a pronounced drop in short-circuit current and a peak in series resistance, phenomena primarily attributed to severe elemental interdiffusion and defect formation at the interfaces. Morphological (SEM) and elemental (EDS) analyses confirmed the temperature-dependent nature of interdiffusion across the Au/BST/perovskite interfaces. These findings underscore the critical role of bonding temperature in triggering interfacial degradation, a factor that mediates the stability of BST-interfaced PSCs during packaging.

Crystals doi: 10.3390/cryst16050301

Authors: Xuefeng Chu Siming Qiao Haiyang Zhao Bingxue Li Junjie Pan Longyu Guo Dingxuan Zhang Chao Wang Sa Lv Faxin Peng Haoran Niu Xuan Fang Xiaotian Yang

Electrochemical exfoliation is an efficient approach for producing MoS2 nanosheets, yet the correlation between exfoliation conditions, structural evolution, and nonlinear optical (NLO) properties remains insufficiently understood. In this work, MoS2 nanosheets were prepared using two representative electrolyte systems, acetonitrile/TPABr and aqueous Na2SO4, under controlled voltages. The results reveal distinct exfoliation mechanisms, where ion intercalation dominates in the nonaqueous system, while bubble-assisted processes prevail in the aqueous system. Structural and chemical analyses (Raman, XRD, EDS, and XPS) demonstrate that the nonaqueous system yields MoS2 with higher crystallinity and lower oxidation degree, whereas the aqueous system shows increased oxidation with the coexistence of Mo5+ and Mo6+ species. Correspondingly, enhanced nonlinear absorption and optical limiting performance are observed. A clear mechanism–structure–property relationship is established, highlighting the critical role of electrolyte environment and applied voltage in tailoring NLO responses. This work provides insights into the controlled preparation of MoS2 nanosheets for photonic and optoelectronic applications.

Crystals doi: 10.3390/cryst16050300

Authors: Aziz Arzine Khaoula Faiz Amal Bouribab Najoua Soulo Pascal Retailleau Mohammed Chalkha Asmae Nakkabi Samir Chtita Bouchra Louasté Taibi Ben Hadda Karim Chkirate Joel T. Mague Adam Duong Reem M. Aljowaiee Mourad A. M. Aboul-Soud Mohamed El Yazidi

In the present study, a series of isoxazole derivatives were severally evaluated for their antifungal activity against the yeast Candida albicans and molds such as Aspergillus niger, Aspergillus flavus, and Fusarium oxysporum. The results demonstrate that the isoxazole derivatives exhibit considerable antifungal potential, particularly isoxazole-sulfonate ester 4b (Ar= 4-(Cl)C6H4, Ar′= 4-(CH3)C6H4), which was found to be active with significant inhibition zones; the diameters of the C. albicans and F. oxysporum samples were measured at 17.00 ± 0.00 mm and 14.00 ± 0.00 mm, respectively. Furthermore, compounds 4a (Ar= 4-(CH3)C6H4, Ar′= 4-(CH3)C6H4), 4c (Ar: 4-(Cl)C6H4, Ar′: 4-(NO2)C6H4) and 4d (Ar: 4-(Cl)C6H4, Ar′: 3-(Cl)-2-(OCH3)C6H3) demonstrated MIC and MFC values of 20 µg/mL against C. albicans. In addition, the anti-hemolytic activity of these derivatives was evaluated. Compounds 4a, 4e (Ar: 4-(Cl)C6H4, Ar′: 3,4-(OCH3)2C6H3) and aroylisoxazole 3a (Ar: 4-(CH3)C6H4) demonstrated a high degree of anti-hemolytic activity (>99%) at all concentrations evaluated (10, 15, and 20 mg/mL). Molecular docking and molecular dynamics studies over 200 ns revealed protein–ligand complexes to have high affinity and stability, which agrees with the experimental results. The compounds 4d, 4e, and 3a have shown significant interaction with the target proteins of C. albicans, A. flavus, and F. oxysporum, respectively. The results have revealed that the major interaction sites are hydrogen bonding, hydrophobic interactions, and the presence of a water molecule, especially with key residues like TYR_84, ASP_120, SER_90, and THR_89. The crystal structure of compound 4a was also obtained.

Crystals doi: 10.3390/cryst16050299

Authors: Daniel J. Campbell John Collini Kefeng Wang Limin Wang Brandon Wilfong David Graf Efrain E. Rodriguez Johnpierre Paglione

The MnP family of binary compounds presents an intriguingly simple platform to mix-and-match elemental components. Replacement on the transition metal or pnictogen site can alter magnetism, electronic correlations, and electrical properties. Here we report low-temperature properties of CoP, including measurements at magnetic fields exceeding 30 T, revealing de Haas–van Alphen oscillations and a nearly two orders of magnitude increase in resistance. When viewed together with prior work, it is possible to put together a global picture of the role of different atoms in variations in magnetic ordering, lattice coherence, and topological band structure features in this material family.

Crystals doi: 10.3390/cryst16050298

Authors: Alessandra Crispini Francesca Aiello Francesca Scarpelli

Flavanones retrieved in the leaves of Glycyrrhiza glabra (licorice), specifically glabranin (GLA), pinocembrin (PIN) and licoflavanone (LIC), represent a valuable source of bioactive natural products, although their isolation and handling are often complicated by their structural similarity and unfavorable physical properties. In this work, crystal engineering strategies were explored both to facilitate the selective separation of licorice flavanones and to improve their solid-state characteristics. Co-crystallization was investigated as a tool for the selective recognition of PIN from a GLA-rich chromatographic fraction. Guided by structural considerations and predictive analyses performed using the Co-Crystal Design and Hydrogen Bond Propensity (HBP) tools in CCDC Mercury (within CCDC-Materials), co-crystallization experiments were performed with pyridinic co-formers. 4,4′-Bipyridine (BPY) selectively formed a new co-crystal with PIN, enabling the capture of traces of this flavanone directly from the GLA-rich fraction. In contrast, nicotinic acid (NIC) did not form a co-crystal with PIN, consistently with the predicted preference for NIC self-association. In addition, a co-amorphous system between LIC and BPY was obtained by quench cooling, yielding a fully amorphous solid with improved handling properties compared to the waxy precursor. These results highlight the potential of crystal engineering approaches for the selective separation and solid-state modification of natural flavanones.

Crystals doi: 10.3390/cryst16050297

Authors: Qiuli Yan Wenkai Liang Qingfeng Guo

Yellow and pink calcite samples from the Huanggangliang and Xilingol mining areas in Inner Mongolia were investigated to elucidate the relationships among chemical composition, unit-cell parameters, coloration, and luminescence. Electron probe micro-analysis, laser ablation inductively coupled plasma mass spectrometry, X-ray diffraction, infrared spectroscopy, Raman spectroscopy, UV-Vis absorption spectroscopy, and photoluminescence measurements show that samples of yellow and pink calcite differ significantly in impurity incorporation and optical behavior. Yellow calcite is relatively enriched in Mg and rare earth elements, especially Y and Ce, whereas pink calcite contains markedly higher Mn and Fe contents. The pink calcite has smaller lattice parameters and unit-cell volume, consistent with greater substitution of Ca2+ by smaller-radius cations. Spectra reveal that the pink coloration is mainly related to Mn-associated absorption bands at 402 and 527 nm, whereas the yellow color is attributed to weak impurity- and defect-related absorption. Under ultraviolet excitation, yellow calcite exhibits a broad blue–white emission centered at ~470 nm, whereas pink calcite shows an intense orange–red emission near 625 nm characteristic of Mn2+. Variable-temperature photoluminescence further demonstrates that the pink calcite has higher thermal stability, with a thermal-quenching activation energy of 0.218 eV, compared with 0.074 eV for the yellow calcite. These results demonstrate that trace element incorporation plays a key role in regulating the coloration and luminescence of calcite and provide useful insight into the optical behavior of carbonate minerals.

Crystals doi: 10.3390/cryst16050296

Authors: Jie Zhao Zehao Cao Yilongrui Chen Zongtai He

Broadband antireflective surface technology constitutes a crucial technique in optoelectronic devices, playing a key role in reducing optical losses. Ultrafast laser processing provides a flexible route for fabricating micro-nano structures on metallic surfaces because it enables efficient fabrication, high spatial resolution, and minimal chemical consumption. This study uses a variable-angle scanning strategy to texture the copper surface, produce a series of antireflection arrayed micro-nano structures, and study the spectral reflectance characteristics of the copper surface. The results exhibit that 90° orthogonal scanning favors the formation of an arrayed microcone structure, which shows lower reflectance than the non-orthogonal scanning strategies in the 200–1300 nm band, with a minimum reflectance of 0.94%. The 60° and 45° cross-scanning based on the non-orthogonal strategy favors the formation of microcavity structures, and shows low reflectance in the 1300–2500 nm band, with the maximum reflectance remaining below 5%. Laser-induced periodic surface structures (LIPSS) are observed on the structures fabricated by all strategies. This work demonstrates that the scanning angle itself can be used to switch the dominant surface morphology and thereby tailor the spectral antireflection response, and lies in establishing a clear processing–structure–spectral response relationship for copper surfaces, which provides a designable route for wavelength-selective optical absorption in photothermal conversion, infrared detection, and sensing applications.

Crystals doi: 10.3390/cryst16050295

Authors: Evgenii Fomin Ilya Bryukhanov

Dynamic recrystallization processes are known to significantly affect both the mechanical properties and the microstructure of materials. In this paper, we investigate the influence of discontinuous dynamic recrystallization (dDRX) during deformation at high strain rates (from 104 to 105 s−1) and elevated temperatures in pure aluminum and copper (in the range of 700–800 K for aluminum and 800–1100 K for copper). For this purpose, we propose a theoretical model in which the material is described within the framework of continuum mechanics, plastic deformations are modeled using a dislocation plasticity approach, the equation of state is represented by a neural network, and the microstructure evolution is simulated using the cellular automata method. The model is applied to uniaxial compression and tension of copper and aluminum polycrystals with an initial average grain size of 14 μm. It is shown that grain refinement occurs in all systems. The average grain size decreases from 14 μm to 4–5 μm. The distribution of plastic and total strains in the polycrystals is presented. In all considered systems, deformation localization is observed, and the localization pattern changes due to the nucleation of new grains and grain boundary surfaces during dynamic recrystallization.

Crystals doi: 10.3390/cryst16050294

Authors: Naihe Yi Hongwei Zhang Jingnan Hong Zhuo Zhang Hongjie She Sen Yang Weibing Ma

In this study, the sintering behavior and electrical properties of 0.7Pb(Zr0.46Ti0.54)O3 (PZT)–0.1Pb(Zn1/3Nb2/3)O3 (PZN)–0.2Pb(Ni1/3Nb2/3)O3 (PNN) piezoelectric ceramics with different Pb(Fe2/3W1/3)O3 (PFW) doping contents were investigated to obtain a formulation that can be co-fired with silver (Ag) electrodes below 900 °C for multilayer ceramics. PFW was introduced as a sintering aid, which effectively reduced the sintering temperature of the ceramics from 1200 °C to 850 °C. The sample with x = 0.12 exhibited the largest average grain size of 1.72 μm, achieving excellent comprehensive properties with piezoelectric constant (d33) = 477 pC/N, planar electromechanical coupling factor (kp) = 0.68, dielectric loss tangent (tanδ) = 0.0154, and relative density of 98.2%. Furthermore, the feasibility of fabricating piezoelectric actuators based on this optimized composition was verified. Multilayer piezoelectric devices were prepared via screen printing combined with a carbon-based sacrificial layer method. No obvious interdiffusion was observed at the interface between the Ag internal electrodes and the ceramic matrix. The 9-layer device attained a high d33 = 1470 pC/N and produced a large displacement of 5.5 μm (corresponding to a strain = 1.83%) with a voltage of 500 V. The thickness of the multilayer piezoelectric film was approximately 0.3 mm. Through this, the feasibility of manufacturing a multilayered actuator with an Ag electrode was confirmed through the composition of 0.58PZT–0.1PZN–0.2PNN–0.12PFW.

Crystals doi: 10.3390/cryst16050292

Authors: Quanhao Luo Jiaming Yang Xueliang Zhang Xuanchen Wei Huan He Aoping He Tao Liu Tianquan Liang

The electrolytic aluminum industry is facing severe challenges, such as excessive carbon consumption, resulting in more cost and environmental pollution due to the oxidation of carbon anodes. The isothermal oxidation resistance of B4C-SiO2-Albite (BSA) composite coating influenced by the in situ formation behavior and self-healing ability of the borosilicate glass at 1173 K was investigated through XRD, TG-DSC, Raman, FTIR spectroscopy, and SEM/EDS in this paper. The results show that the composite coating with 20 wt% B4C has a relatively low mass gain rate of −0.082% after 24 h at 1173 K. It depends on the in situ formation of the amorphous borosilicate phase layer that can effectively protect the carbon anode from oxidation, which depends on the content of B4C. The amorphous borosilicate glass forms from the reaction between the SiO2 and the B2O3, from the oxidation of B4C during exposure. More B4C promotes the formation and volatilization of B2O3, which improves the viscosity and stability of the borosilicate glass by changing the glass network coupled with Na+ and Al3+ from Albite. It is a feasible strategy for designing durable coatings with appropriate B4C addition for high-temperature applications.

Crystals doi: 10.3390/cryst16050293

Authors: Chenhao Wen Fengwei Yuan Haowei Fu Yanqiang Lu Rong Yi Jian Guo

Laser assistance offers a promising pathway for high-efficiency and low-damage ultraprecision grinding for difficult-to-machine hard-brittle semiconductors. This study employs atomistic simulation to investigate the surface removal and subsurface damage mechanisms of C-, M-, and A-plane AlN workpieces during single-grit laser-assisted nanogrinding (LAG). The results indicate that LAG reduces material pileup, thereby decreasing the grit–workpiece contact area and grinding resistance. By leveraging laser-induced thermal effects to enhance atomic plastic flow, LAG evidently achieves a higher material removal rate than conventional grinding (CG). Grinding the C-plane along a <11–20> orientation yields the lowest surface roughness, although this improvement is not useful for the M- and A-planes. Tangential force increases linearly with grinding depth in both methods, but LAG exhibits a lower rate of increase. LAG consistently produces lower grinding forces and friction coefficients and results in lower dislocation densities in C- and A-plane AlN workpieces at nearly all grinding depths. The C-plane exhibits the thinnest damage layer, followed by the M-plane, with the A-plane the thickest. Increasing the laser power density lowers the grinding force and enhances the removal efficiency. Optimal power density minimizes subsurface damage and improves surface quality; however, excessive power density exacerbates damage. This work provides valuable insights for developing high-efficiency, low-damage LAG techniques for hard-brittle semiconductors.

Crystals doi: 10.3390/cryst16050291

Authors: Lutfi Arda Ersin Ozugurlu Ilke Tascioglu

Mg-doped ZnO (Zn1−xMgxO, x = 0.00–0.05) thin films were successfully grown on glass substrates with a c-axis orientation at 600 °C using the sol–gel dip-coating technique. The structural features, defect-related photoluminescence, and optical constants of the films were systematically investigated as a function of Mg concentration. X-ray diffraction (XRD) patterns confirmed a single-phase hexagonal wurtzite structure with a preferential (002) orientation for all compositions, indicating the successful substitution of Mg2+ ions into the ZnO lattice. The crystallite size (D002) was found to vary between 28.49 and 41.18 nm, while microstrain and stress exhibited non-monotonic behavior depending on Mg content. This behavior reveals a transition from compressive to tensile stress due to lattice distortion and defect formation. Photoluminescence (PL) spectra showed a dominant near-band-edge (NBE) ultraviolet emission, along with broad visible emissions extending from violet to red. Optical constants were accurately extracted using a double-facet-coated substrate (DFCS) model, combined with nonlinear curve fitting using the Nelder–Mead optimization algorithm. The films showed a strong absorption edge at about 370 nm and exceptional optical transparency (≈60–80%) in the visible spectrum. The systematic blue shift in the extinction coefficient with increasing Mg content confirms bandgap engineering in Zn1−xMgxO thin films. The refractive index dispersion was successfully modeled using the Cauchy relation, demonstrating composition-dependent tunable optical properties. Depending on the Mg content, the optical bandgap values ranged from approximately 3.265 to 3.315 eV. The band-edge states and optical constants are strongly affected by the combined effects of defect development, Mg-induced lattice distortion, and changes in optical dispersion. These results indicate that sol–gel-derived Mg-doped ZnO thin films with composition-dependent stress states, defect states, and tunable optical properties are promising candidates for UV photodetectors, optical coatings, and transparent optoelectronic devices.

Crystals doi: 10.3390/cryst16050290

Authors: Giovanni Bella Francesco Nicolò Giuseppe Bruno Amine Assel Antonio Santoro

Two zinc(II)-trimesate metal–organic frameworks were synthesized under hydrothermal conditions and structurally characterized by single-crystal X-ray diffraction. Although both compounds originate from the same Zn(II)-benzene-1,3,5-tricarboxylate (BTC) chemical system, they crystallize in different space groups and exhibit distinct coordination environments and secondary building units (SBUs). One framework adopts a cubic structure and is built from a binuclear Zn paddlewheel type SBU, characterized by a short Zn–Zn internuclear distance and four μ2-bridging carboxylate groups. In contrast, the second framework crystallizes in a tetragonal lattice and features mixed Zn(II) coordination environments, with the coexistence of tetrahedral and octahedral metal centers assembled into a fundamentally different SBU. The comparison between these two structures highlights the coordination flexibility of Zn(II) and the sensitivity of Zn–BTC frameworks to crystallization conditions, such as solvent composition. These results underline the importance of detailed crystallographic analysis in revealing SBU diversity and provide insight into how variations in local coordination chemistry can lead to distinct framework architectures from identical chemical building blocks.

Crystals doi: 10.3390/cryst16050289

Authors: Gerda Rogl Peter Rogl

Besides filled skutterudites with a high figure of merit, unfilled skutterudites also play an important role as thermoelectric materials; furthermore, they are easier to produce and do not need expensive rare earths as fillers. In the present review, thermoelectric properties (at 300 K and at the highest measured temperature) of more than 600 compositions from more than 230 publications between 1957 and 2025 were collected and evaluated. In various figures, the dependence of the peak ZT on the electrical resistivity, Seebeck coefficient, the power factor and the thermal conductivity is displayed for (i) binary CoSb3, for (ii) CoSb3 substituted at the Co-site, for (iii) substitution at the Sb-site or at both sites as well as for (iv) unfilled skutterudites without Co or Sb or Co and Sb. In most cases, the peak ZT equals the ZT at the highest measured temperature. Thermoelectric data are listed (i) to comply with the periodic chart and publishing year as well as (ii) in the form of a graphical overview of all discussed skutterudites. In this respect, this review will support the search for the ideal TE material for practical use.

Crystals doi: 10.3390/cryst16050288

Authors: Yu Sun Yihang Qin Wenhao Chen Wenhui Zhao Haoran Sun

Oxide perovskites with simultaneously large band gaps and high-static dielectric constants are of considerable interest for advanced microelectronics, dielectric devices, and energy storage applications, yet their discovery remains challenging because electronic insulation, lattice polarizability, and thermodynamic accessibility are strongly coupled and often mutually competitive. Here, we develop a physics-guided multitask learning framework for the joint prediction of the band gap and static dielectric response in chemically constrained single-perovskite oxide ABO3 compounds. To ensure data fidelity and physical comparability, the learning space is strictly restricted to simple oxide ABO3 perovskites from the Materials Project, while mixed-fidelity band gaps, heterogeneous dielectric definitions, and chemically inconsistent samples are excluded. The model integrates role-aware A-/B-site descriptors, perovskite-specific geometric and structural features, multitask prediction of Eg, εtotal, εelectronic, and εionic, explicit physical consistency constraints, auxiliary candidate classification, ranking learning, and reliability-aware screening with uncertainty and out-of-distribution control. Under B-site-grouped cross-validation, the framework achieves 97.4% accuracy, Recall of 96.5%, and an F1 score of 96.1%, while maintaining robust transferability on the independent JARVIS validation set. The results show that high-gap/high-k candidates occupy a chemically non-random subspace governed by B-site-centered electronic–lattice coupling, and that physically consistent multitask learning substantially improves both predictive coherence and candidate enrichment. More broadly, this study establishes a data-consistent, physics-constrained, and transferable paradigm for the intelligent discovery of functional oxide dielectrics.

Crystals doi: 10.3390/cryst16050287

Authors: Anxing Wang Hao Li Qing Zhang Yu Zhang Yuhang Wu Deshui Yu Xing Fang Guojun Yuan

Achieving stable dispersion and sustained antibacterial activity of natural bioactive compounds in bio-based packaging remains challenging. In this study, chitosan (CS) films incorporating a β-cyclodextrin–curcumin inclusion complex (Cur/β-CD) were developed to improve film properties and the refrigerated preservation of sea bass. The CS/Cur/β-CD films were prepared by one-step solution casting without intermediate isolation or purification. The inclusion conditions were optimized, and the resulting films were evaluated in terms of tensile strength (TS), elongation at break (EAB), and water vapor permeability (WVP). Among the tested formulations, the film prepared at a Cur:β-CD ratio of 1:1, 40 °C, and 1 h (1:1 40 °C 1 h) showed the best overall performance in TS, EAB, and WVP. It was therefore selected for subsequent structural characterization, antibacterial evaluation, and preservation testing. The 1:1 40 °C 1 h film exhibited a 156% increase in tensile strength and a 28.5% decrease in water vapor permeability compared with the neat CS film. The composite film exhibited measurable diffusion-based antibacterial activity against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus). During the 8 d refrigerated storage period, the film suppressed total viable counts (TVC), slowed the increase in pH, and retarded total volatile basic nitrogen (TVB-N) accumulation, thereby maintaining acceptable microbiological quality throughout the observation period. Compared with the unwrapped, PE, and CS-film control groups, the treated samples showed better preservation performance over the tested storage period. Overall, the incorporation of Cur/β-CD provides a simple strategy for improving the mechanical strength, moisture barrier properties, antibacterial activity, and preservation performance of CS films during refrigerated storage, highlighting their potential for active packaging of chilled aquatic products.

Crystals doi: 10.3390/cryst16050286

Authors: Dina U. Abdullina Sergey V. Dmitriev Ilya S. Sugonyako Arseny M. Kazakov Elena A. Korznikova

This study investigates the phenomenon of supratransmission in three-dimensional crystals with a B2 (CsCl) structure, employing classical molecular dynamics with β-Fermi–Pasta–Ulam–Tsingou potentials up to fourth-nearest neighbors. We analyze energy transfer from a harmonically driven surface into the crystal bulk across various frequency regimes relative to the phonon spectrum. While low-amplitude excitation results in energy transmission only within the phononic bands, high-amplitude driving triggers supratransmission in the phononic gap and above the optical band. Our results demonstrate that in these nonlinear regimes, energy is transported not by linear phonon waves but by discrete breathers (DBs) emitted quasi-periodically from the surface. A key finding is the distinct sublattice selectivity of these excitations: gap DBs propagate primarily along the heavy atom sublattice, whereas above-spectrum DBs travel along the light atom sublattice. We quantify the velocities and oscillation periods of these localized modes, revealing their critical role in bypassing linear spectral restrictions. These findings provide new insights into nonlinear energy transport in binary alloys and suggest potential applications for controlling heat flow and signal processing in crystals.

Crystals doi: 10.3390/cryst16050285

Authors: So Yeon Lee Hyo Been Jin Hyun Ho Park

Agmatinase (SpeB) catalyzes the hydrolysis of agmatine to produce putrescine, a key step in bacterial polyamine biosynthesis. Here, we report the crystal structure of SpeB from Klebsiella pneumoniae (kpSpeB) and characterize its oligomeric and active-site architecture. SEC–MALS analysis demonstrates that kpSpeB forms a canonical hexamer in solution. Structural comparison reveals high similarity to Escherichia coli SpeB and other members of the arginase superfamily, including proclavaminic acid amidino hydrolase (PAH) and guanidine hydrolase (GdmH). Despite strong conservation of residues coordinating the binuclear Mn2+ center, subtle differences in metal positioning and cavity geometry were observed. Surface analysis indicates variations in active-site cavity volume among homologues, with partial occlusion in GdmH due to a bulky tryptophan residue. These findings suggest that minor adjustments in metal coordination and cavity architecture may fine-tune substrate selectivity while preserving the conserved catalytic framework of the arginase superfamily.

Crystals doi: 10.3390/cryst16050284

Authors: Shuo Ran Yingxin Liu

Nephrite is a significant jade resource, and systematic investigation of its deposits contributes to regional metallogenic synthesis and exploration targeting. The recently discovered white nephrite deposit in the Dikou area, Fujian Province, remains inadequately characterized. This study presents a comprehensive mineralogical investigation employing polarizing microscopy, scanning electron microscopy, electron probe microanalysis, X-ray powder diffraction and laser Raman spectroscopy to elucidate the mineralogical and petrochemical characteristics of Dikou nephrite and constrain its genesis. The results demonstrate that tremolite constitutes the predominant mineral phase, accompanied by abundant diopside and quartz, with minor dolomite, prehnite, and apatite. Based on subtle compositional variations, tremolite can be categorized into two generations: early metasomatic Tr-I and late-stage Tr-II. All tremolite samples exhibit Fe-depleted, Mg-enriched composition with Mg# > 0.99. The mineral assemblage and textural relationships record multiple episodes of hydrothermal metasomatism. Integrated with the regional geological constraints, the deposit formation is genetically linked to the Neoproterozoic–Early Paleozoic ocean–continent transition of the South China Plate and is classified as D-type nephrite. The Dikou nephrite exhibits the mineral assemblage typical of dolomite-related deposits, displaying a distinctive felt-like fibrous texture that yields a homogeneous structure and superior aesthetic quality. Its Fe-depleted composition imparts a notably lighter coloration relative to D-type nephrite from other deposits. This study advances understanding of Dikou nephrite genesis, highlights the diversity of metallogenic environments in Fujian Province, and provides a theoretical framework for exploration of analogous deposits.

Crystals doi: 10.3390/cryst16050283

Authors: Žana Mickevičienė Aldona Balčiūnaitė Dijana Šimkūnaitė Jūratė Vaičiūnienė Loreta Tamašauskaitė-Tamašiūnaitė Eugenijus Norkus

We report a straightforward and scalable strategy for the fabrication of three-dimensional Ni-rich bimetallic NiCu foam coatings on Ti substrates ((NiCu)foam/Ti) via dynamic hydrogen bubble templating (DHBT) electrodeposition, followed by modification with an ultralow amount of Pt to construct an efficient ternary Ni–Cu–Pt catalytic system. The resulting foams exhibit highly porous dendritic architectures with interconnected channels, enabling a high density of electrochemically active sites and uniform metal distribution throughout the framework. Structural and compositional analyses (SEM–EDX) reveal a Ni-dominant composition (28.09–34.61 mg cm−2), with significantly lower Cu content (2.47–4.16 mg cm−2) and ultralow Pt loading (9.63–19.04 μg cm−2), maximizing catalytic efficiency while minimizing noble metal usage. Electrochemical studies in alkaline media demonstrate that the NiCu foam possesses intrinsic borohydride electrooxidation activity, which is substantially enhanced upon Pt incorporation, delivering a threefold increase in activity compared to the unmodified foam and outperforming bulk Pt. This improvement is attributed to the synergistic interplay within the Ni-rich ternary system, where trace Pt acts as a highly effective promoter. When implemented as anodes in NaBH4–H2O2 fuel cells, Pt(NiCu)foam/Ti achieves peak power densities of 239 and 301.6 mW cm−2 at 25 °C and 55 °C, respectively. Overall, this study presents a cost-effective and scalable route to high-performance electrocatalysts for alkaline direct borohydride fuel cells, significantly reducing reliance on noble metals while maintaining superior activity.

Crystals doi: 10.3390/cryst16050282

Authors: Wen Feng Ting Sun Tianyu Zhao Junjie Zhou Zhengyu Han

This study presented an application of thermomechanical processing consisting of cold rolling and subsequent annealing in SP2215 heat-resistant steel to investigate the effects of thermomechanical processing parameters on the evolution of grain boundary character distribution (GBCD) and to elucidate the relationship between GBCD and creep properties. The experimental results show that the optimal process, characterized by 10% cold rolling reduction followed by annealing at 1100 °C for 10 min, was determined to significantly increase the fraction of low-Σ coincidence site lattice (CSL) boundaries up to 74.27%, and effectively disrupt the connectivity of the random boundary network, as corroborated by the highest average twin-related domain (TRD) size of 42.58 μm and average number of grains per TRD of 7.28. Such a modified GBCD leads to a notable enhancement in creep performance, resulting from the induction of a high fraction of low-Σ CSL boundaries and the disruption of the random boundary network, which effectively inhibits intergranular crack initiation and propagation during creep deformation.

Crystals doi: 10.3390/cryst16050281

Authors: Junya Sugiyama Ko Yoneda Masayuki Koikawa

Two metallacyclic tetranuclear Fe(III) complexes, [{Fe2(μ-O)(μ-RCOO)2(tpon)}2](BPh4)4 [R = Me (1), Ph (2)], where the flexible ditopic ligand tpon (N,N,N′,N′-tetrakis(2-pyridylmethyl)octane-1,8-diamine) links two μ-oxo-bis(μ-carboxylato) triple-bridged dinuclear units, have been prepared. Single-crystal X-ray diffraction establishes that both complexes adopt a 26-membered macrocyclic framework featuring an internal cavity capable of guest inclusion. Notably, incorporation of a monoatomic μ-oxo bridge enforces an outward orientation of the ligand alkyl chains, thereby suppressing the “zipper effect” observed in the previously reported Mn(II) analogue and facilitating the encapsulation of an acetone molecule. UV–vis absorption and diffuse-reflectance spectra confirm that the tetranuclear scaffold remains intact in both the solid state and in solution. These results demonstrate that modulating local coordination directionality via μ-oxo bridging is an effective strategy for controlling the global conformation and host–guest properties of large metallasupramolecular architectures.

Crystals doi: 10.3390/cryst16050280

Authors: Shiyu Sun Peifeng Fan Zhenzhen Ren Weihua Wang

Building upon our previous research in which we derived two formulations of the governing equations expressed in terms of ρ,B,v and the perturbation displacement ξ, we extend our analysis to investigate the dispersion relation of linear magnetohydrodynamic (MHD) waves in a one-dimensional flux-sheet magneto-lattice. The convergence of the dispersion relations is examined by increasing the truncation order of the reciprocal lattice vectors from 3 to 10, for the central equations expressed in terms of ρ,B,v, and for modulation amplitudes of Bm=0.01, 0.02, 0.1, 0.2, 0.3 and 0.4. The dispersion relations obtained at different truncation orders exhibit rapid convergence for small modulation amplitudes Bm, with only minor discrepancies emerging as Bm increases, indicating overall satisfactory convergence of the plane wave expansion (PWE) method within the investigated parameter range. A comparative analysis with the previously studied sinusoidal magneto-lattice reveals that, while the overall dispersion structure remains qualitatively similar, the flux-sheet magneto-lattice yields wider bandgaps at equivalent modulation amplitudes. This is shown to result from the distinct Fourier spectra of the two periodic structures, which differ in both the magnitude and the harmonic content of their reciprocal lattice components.

Crystals doi: 10.3390/cryst16050279

Authors: Leonid Kustov Vadim Vergun Valery Zakharov Leonid Aslanov

Application of porous coordination polymers (PCPs), which include metal–organic frameworks (MOFs) and covalent organic frameworks (COFs) in sensors for detection of toxicant pollutants in water is discussed. Particular attention is given to electrochemical and photoluminescent sensors because PCPs/MOFs demonstrate good selectivity towards adsorption of molecules in combination with outstanding luminescent properties and electroconductivity in composite materials. The use of PCPs/MOFs as pre-concentrators of the compounds to be analyzed is also outlined. The review covers the results described in the literature over the past 5 years in such diverse fields as the determination of metal ions and anions, drugs, mycotoxins, pesticides, explosives, bacteria, etc. Thus, the review demonstrates the proliferation of MOF applications and the universal nature of sensors based on them.

Crystals doi: 10.3390/cryst16040278

Authors: Xiaoming Shi Zheng Wang Tianhao Gao Guoping Cao Zhuhong Liu Houbing Huang Xingqiao Ma Sanqiang Shi

We propose a reaction–diffusion phase-field model to simulate the microstructure evolution of voids in systems with low vacancy concentration under irradiation. In this model, void growth and shrinkage are governed by reactions between vacancies/interstitials and the void surface, while an order parameter is introduced to describe void morphology. By avoiding the sharp increase in vacancy concentration near the void interface, the model enables the simulation of void evolution in low vacancy concentration matrices over enlarged time scales. When combined with classical nucleation theory, the approach enables quantitative, accurate three-dimensional simulations of slow void evolution processes, achieving comparability with rate theory models. Numerical results demonstrate that the model accurately captures the evolution of voids under dilution conditions. At the same time, its inherent scalability makes it broadly applicable to other material systems characterized by low solute concentrations.

Crystals doi: 10.3390/cryst16040277

Authors: Shigekazu Hidaka Chikara Watanabe Hisato Yasumatsu

Lanthanum silicate oxyapatite (LSO) is a promising oxide ion conductor for low-temperature-operating electrochemical devices owing to its high ionic conductivity along the c-axis. However, the fabrication of thin films with controlled crystallographic orientation remains challenging. In this study, polymer-assisted deposition (PAD), a solution-based technique offering precise microstructural and compositional control, was employed to fabricate c-axis-oriented LSO thin films. The fabrication of undoped LSO and the effects of Al and Mg incorporation on its microstructure, orientation, and ionic conductivity were systematically investigated. Undoped LSO thin films crystallised with a preferential c-axis orientation in the annealing temperature range of 800 and 1100 °C, and scanning transmission electron microscopy observations revealed a highly crystalline, void-free microstructure. Upon annealing at 1200 °C, the undoped LSO exhibited columnar grains with anisotropic in-plane grain growth, whereas Al- or Mg-doped LSO suppressed anisotropic in-plane grain growth and retained an out-of-plane c-axis orientation. The undoped LSO showed higher in-plane ionic conductivity than the doped thin films, consistent with their distinct crystallographic orientations. These results demonstrate that PAD provides a viable pathway for tailoring the microstructure and the composition of LSO thin films, thereby facilitating their applications in solid oxide electrochemical devices.

Crystals doi: 10.3390/cryst16040276

Authors: Alexandre Brailovski Ali Beydoun André Guerra Alejandro D. Rey Phillip Servio

Ice adhesion on exposed structures remains a major operational challenge, motivating the search for passive, material-based anti-icing strategies. Molecular dynamics offers a controlled way to investigate ice–surface interactions beyond the limits of experimental setups. In this work, we develop a simulation framework to model the impact of solid hexagonal ice droplets on metallic substrates. Ice impacts are simulated across a range of velocities (10–120 m/s), temperatures (120–250 K), and face-centred cubic surface materials (gold, copper, silver, aluminum, and nickel). Using LAMMPS, mW water force-field, EAM/Alloy metal potentials, and Lennard-Jones water–surface interactions, we quantify phase evolution through angular order parameter and quasi-liquid layer measurements, complemented by the CHILL+ algorithm in OVITO. By isolating all external factors, we show that melting increases with velocity and temperature and correlates with substrate properties: metals with high thermal diffusivity and low Young’s modulus tend to decrease post-collision ice melting. The ratio of the former to the latter, a derived index of merit Υ, significantly correlates with melting percentage and identifies silver as the most effective anti-ice material examined. Statistical analyses strongly suggest that these surface properties influence interfacial melting, supporting the use of this modelling framework for screening and designing anti-icing materials.

Crystals doi: 10.3390/cryst16040275

Authors: Veronika Balejová Martin Suláni Alena Michalcová Jan Blažek Dalibor Vojtěch

Composite materials with Ti or Ti alloy reinforcement in a Zn matrix are new, promising materials with potential applications in implantology. Infiltrating zinc into the porous titanium reinforcement of a designed implant could improve its osseointegration. In this field, it is important to avoid the formation of brittle intermetallics; therefore, understanding their growth is fundamental. This work focuses on characterizing the Ti-Zn intermetallic phases at the interface of the TiAlV/Zn and Ti/Zn composites. Samples were prepared by immersing the Ti-6Al-4V or Ti bulk material in zinc melt at various temperatures. After various dwell times, the samples (pieces of Ti-6Al-4V or Ti in the molten zinc) were removed from the furnace and cooled in air. The sequence of evolution of intermetallic phases was observed to be dependent on dwell time at selected temperatures. The influences of surface treatment methods on the boundary structure were also tested.

Crystals doi: 10.3390/cryst16040274

Authors: Abdullah Hasan Karabacak Aykut Çanakçı Sedat Alperen Tunç Taylan Başkan Ahmet Hakan Yılmaz

Functionally graded AA2024/B4C metal matrix composites were fabricated via mechanical alloying and hot pressing to investigate structure–property–radiation shielding relationships. Single-layer, two-layer, and three-layer architectures with varying B4C contents were systematically produced. Microstructural homogeneity and phase constitution were examined using SEM/EDS and XRD, while thermal stability was evaluated by thermogravimetric analysis. Density and porosity measurements were conducted to assess the influence of reinforcement distribution and functional grading on densification behavior. Gamma radiation shielding performance was experimentally evaluated using a 152Eu source and an HPGe detector over a wide photon energy range. Key shielding parameters, including linear and mass attenuation coefficients, half-value layer, tenth-value layer, mean free path, and radiation protection efficiency, were determined. The results reveal that functional grading significantly enhances radiation attenuation compared to monolithic composites. The three-layer AA2024/B4C composite exhibited the highest attenuation coefficients and the lowest HVL, TVL, and MFP values at all investigated energies, achieving nearly 100% improvement in shielding efficiency relative to unreinforced AA2024. These findings demonstrate that controlled B4C distribution and layered composite architecture provide a synergistic improvement in thermal stability, physical integrity, and radiation shielding performance, positioning functionally graded AA2024/B4C composites as efficient lightweight materials for advanced radiation shielding applications. These results indicate that the developed functionally graded AA2024/B4C composites are promising candidates for advanced radiation shielding applications in nuclear facilities, aerospace structures, and medical radiation protection systems, where lightweight and high-performance materials are critically required.

Crystals doi: 10.3390/cryst16040273

Authors: Peng Wang Xin Chen Yongzhen Zhang

Accurate prediction of corrosion-fatigue crack growth rate in aluminum alloys is critical for the safety assessment of aerospace structures. Conventional empirical fracture-mechanic models often struggle to capture multiphysics coupling effects, whereas purely data-driven machine-learning models may lack physical interpretability and generalize poorly beyond the training distribution. To address this challenge, this study proposes a physics-guided knowledge-based XGBoost (KBXGB) model. Based on a comprehensive dataset comprising 2786 experimental records, Permutation Feature Importance was utilized to identify 11 key features, including the stress intensity factor range, stress ratio, frequency, and environmental parameters. The KBXGB framework learns the residual between physics-based empirical models (e.g., the Paris and Walker laws) and measured experimental data, recasting the complex nonlinear mapping into a correction of the systematic deviations of the physical models, thereby achieving deep integration of domain knowledge and data-driven learning. Test results demonstrate that the KBXGB model achieves a coefficient of determination (R2) of 0.9545 and a reduced Mean Relative Error (MRE) of 1.61% on the test set, outperforming standard XGBoost and traditional regression models. Crucially, in independent extrapolation validation, the standard XGBoost model failed (R2 = 0.2858) with non-physical staircase artifacts, whereas the KBXGB model maintained high predictive fidelity (R2 = 0.8646) and successfully reproduced physical crack growth trends. The proposed approach effectively mitigates the “black-box” limitations of machine learning in sparse data regions, offering a high-precision and physically robust tool for corrosion fatigue-life prediction under complex service conditions.

Crystals doi: 10.3390/cryst16040272

Authors: Patricia Alejandra Guerrero-Alquicira Martín Zermeño-Ruiz Carlos Angulo Luis Miguel Anaya-Esparza Pedro Isaac Muñoz-Reaño Aurora Petra Cruz-Condemarín Gabriela Hinojosa-Ventura Carlos Arnulfo Velázquez-Carriles Jorge Manuel Silva-Jara Ernesto Rodríguez-Lafitte

This study explored the eco-friendly synthesis of AgNPs using Prosopis laevigata seed mucilage and assessed their antimicrobial, antibiofilm, and biocompatibility effects against foodborne pathogens. The AgNPs were mostly spherical, with sizes ranging from 2.5 to 56 nm (average: 14.69 nm), as confirmed by XRD and DLS analysis. They showed consistent antimicrobial activity, with MICs at 0.5 mg/mL and MBCs at 1.0 mg/mL across all tested strains, and inhibited bacterial growth by over 75% at 0.5–5 mg/mL, similar to or better than gentamicin. The antibiofilm performance was notable, with inhibitions of 76–84% against E. coli (1–10 mg/mL), 96–98% against S. aureus (0.5–10 mg/mL), 76–82% against Salmonella Typhimurium (0.5–10 mg/mL), and 70–84% against P. aeruginosa (1–10 mg/mL), surpassing gentamicin against E. coli and P. aeruginosa. Cell viability remained 100% at 0.25 mg/mL, and no significant changes in immunological parameters were observed, suggesting good biocompatibility at therapeutic doses. This research shows, for the first time, that P. laevigata mucilage is an effective bioreducing agent for green synthesis of AgNPs with antimicrobial and antibiofilm activity against both Gram-negative and Gram-positive foodborne pathogens. Its superior ability to inhibit biofilms compared to traditional antibiotics, along with its safety profile at therapeutic levels, makes these nanoparticles promising for food safety applications, antimicrobial coatings, and topical treatments. Overall, the findings support the use of native plant resources in green nanotechnology to address global challenges of antimicrobial resistance.

Crystals doi: 10.3390/cryst16040271

Authors: Xiaofan Zheng Lei Zhang Longquan Song Nianshun Zhao Xiaole Ge

To improve the surface properties of 40Cr steel, Ni45/Y2O3 laser-cladded coatings (L-CCs) were fabricated on the surface of 40Cr steel. The effects of Y2O3 addition (0.5%, 1.0%, and 1.5%) on the microstructure, microhardness, residual stress, wear resistance, and corrosion resistance of the L-CCs were systematically investigated. The results indicate that Y2O3 has a significant effect on enhancing the corrosion resistance and suppressing the residual stress of the L-CCs, whereas its contribution to the improvement of microhardness and wear resistance is relatively limited. Compared with the single Ni45 L-CC, the L-CC containing 1.0% Y2O3 exhibited a 45.9% reduction in corrosion current density and a 79.3% reduction in residual stress. At a Y2O3 addition of 0.5%, the microhardness increased by 4.0%, while the average friction coefficient and wear mass loss decreased by 4.8% and 2.6%, respectively, relative to the single Ni45 L-CC. Excessive Y2O3 addition reduces the fluidity of materials in the molten pool and deteriorates the microstructural uniformity, thereby weakening or even impairing the surface properties of the L-CCs.

Crystals doi: 10.3390/cryst16040270

Authors: Peng Chen Zhizhong Chen

Following the remarkable success of the first edition, we are honored to present the second edition of the Special Issue titled “Recent Advances in III-Nitride Semiconductors and Correlated Wide Bandgap Semiconductors” [...]

Crystals doi: 10.3390/cryst16040269

Authors: Eugenia Pechkova Fabio Massimo Speranza Paola Ghisellini Cristina Rando Katia Barbaro Ginevra Ciurli Stefano Ottoboni Roberto Eggenhöffner

This study quantifies how confinement changes the orientational phase space of proteins by comparing hanging-drop (HD) with Langmuir–Blodgett (LB) conditions within a unified probabilistic framework grounded in structural data from the Protein Data Bank (PDB). For each protein, principal moments of inertia are computed from atomic coordinates, trace-normalized, and used to define a geometry-based benchmark for the probability of occupying a predefined productive-orientation set. In parallel, a Hamiltonian-weighted probability is obtained within a classical statistical–mechanical treatment by reconstructing the orientational distribution over the polar–azimuthal domain under a fixed global confinement protocol. The analysis is carried out on a ten-protein panel spanning diverse sizes and anisotropies, and the HD→LB contrast is characterized through probability gains, distributional distances, and an energy-basin decomposition that distinguishes basin depth from basin measure. Under identical parameterization, LB globally produces higher productive-orientation probabilities than HD across all proteins, establishing a uniform direction of the confinement effect while preserving protein-dependent magnitudes. The inertia-based benchmark exhibits broader dispersion in LB/HD amplification, whereas the Hamiltonian construction yields a more regular cross-protein gain, consistent with LB acting as a global reweighting of orientational phase space rather than a protein-specific re-tuning. By integrating PDB-derived structural descriptors with a statistical–mechanical operator, the framework provides a transparent bridge between molecular geometry and confinement-driven ordering and offers a compact basis for comparing crystallization-relevant confinement protocols across structurally heterogeneous proteins.

Crystals doi: 10.3390/cryst16040268

Authors: Yang Luo Ke Tao Lei Cao Guocheng Wang Gang Li

The precipitation of nanoscale HfO2 plays a critical role in the high-temperature creep properties of Fe-Cr-Al electrical heating alloys. However, the atomic-scale initial nucleation and growth mechanisms remain unclear, hindering the precise design of precipitates based on Hf microalloying. In this study, classical molecular dynamics simulations implemented in LAMMPS were employed to investigate the formation and evolution of Hf-O clusters at 1773 K, 1873 K, and 2000 K. The Fe-Cr-Al-Hf-O system was described by hybrid potential functions, whose reliability was verified by lattice-parameter calculations in good agreement with literature values. The simulation results demonstrate that Hf atoms and O atoms attract each other, forming stable Hf-O clusters. At higher temperatures, the diffusion capabilities of Hf and O atoms are enhanced, the number of Hf-O bonds grows, and the size of the largest cluster expands, indicating that elevated temperatures promote cluster growth. The calculated diffusion activation energy of Hf and O atoms indicates that increasing temperature promotes O atom diffusion more significantly. Analysis of the cluster radius of pair gyration and average atomic energy reveals that Hf-O clusters formed at 1873 K exhibit more compact and stable structural characteristics. Radial distribution function analysis further revealed that the atomic arrangement of neighboring atoms in Hf-O clusters closely resembles the relaxed HfO2 crystal structure at the same temperature, indicating that Hf-O clusters serve as critical nucleation cores promoting the precipitation of HfO2 crystals. This study elucidates the dynamic formation mechanism and structural evolution of Hf-O clusters in Fe-Cr-Al alloys at the atomic scale, providing valuable guidance for the optimized design of precise control over HfO2 nanoprecipitates.

Crystals doi: 10.3390/cryst16040267

Authors: Shushan Hu Gang Huang

While macroscopic stress significantly impacts the performance of metallic components, the underlying atom–electron coupling mechanisms governed by distinct crystal symmetries remain insufficiently understood. To address this gap, this work systematically investigates the structural and electronic evolution of representative metallic materials under applied stress. Experimentally, X-ray diffraction (XRD) revealed complex macroscopic residual stress distributions in cold rolled titanium alloy and silicon steel. Motivated by these engineering observations, first-principles density functional theory (DFT) calculations were conducted to uncover the underlying physical mechanisms. Specifically, the responses of face-centered cubic (FCC) aluminum and copper, body-centered cubic (BCC) iron, and hexagonal close-packed (HCP) titanium crystals were investigated under tension and compression using the RPBE functional. Stress-dependent elastic properties, density of states (DOS), band structures, and phonon spectra were calculated. Results show that tension softens all metals (Al becomes mechanically unstable), whereas compression stiffens their lattices. Electronically, tensile loading sharpens DOS peaks near the Fermi level and shifts conduction bands closer to it, whereas compression smooths DOS peaks and shifts bands away. Phonon analysis indicates Cu and Ti remain dynamically stable, while Al and Fe exhibit phonon mode softening under high tension. These stress-induced changes highlight crucial atom–electron coupling mechanisms, providing a theoretical basis for tailoring metallic performance via stress engineering.

Crystals doi: 10.3390/cryst16040266

Authors: Anna Maria Mazurek Monika Franczak-Rogowska Łukasz Szeleszczuk

Understanding pressure-induced isosymmetric phase transitions in molecular crystals requires consideration of both structural and thermodynamic factors, particularly in hydrogen-bonded systems. In this work, periodic density functional theory (DFT) calculations were employed to investigate the pressure-dependent behavior of L-serine and to elucidate the origin of its experimentally observed phase transition between Phase I and Phase IV. Geometry optimizations performed at ambient pressure and 8.8 GPa reproduce the compression of the crystal lattice and the pressure-driven stabilization of Phase IV. However, no spontaneous reorientation of the hydroxyl groups is observed, indicating that the transition is not accessible within a purely static framework. To further explore the stability of the system, a series of modified crystal structures with different hydroxyl group orientations was generated and analyzed, revealing a complex energy landscape at ambient conditions that becomes significantly simplified under compression. Phonon calculations within the quasi-harmonic approximation demonstrate that the experimentally observed Phase I structure is not stabilized by enthalpy but by vibrational entropy, whose contribution increases with temperature. These results show that the phase transition in L-serine is governed by an interplay between lattice energy, hydrogen-bond rearrangement, and vibrational effects, and highlight that an accurate description of polymorphic stability in such systems requires inclusion of both static and dynamic contributions.

Crystals doi: 10.3390/cryst16040265

Authors: Yumeng Jiang Zhenwei Zhang Zhongyi An Xinyu Pan Xinmin Shi Ruonan Wang Jiajian Li Chengzhi Chen Zhiqiang Cao Yong Xu Jiaqi Wei Xueying Zhang Yi Peng

X-ray techniques provide powerful, non-destructive tools for structural characterization in semiconductor manufacturing and advanced packaging. Their strong penetration capability and sensitivity to multiple contrast mechanisms enable the investigation of lattice structure, strain, defects, interfaces, and elemental distribution across a wide range of length scales. As semiconductor devices evolve toward three-dimensional architectures and heterogeneous integration, there is an increasing demand for characterization approaches capable of probing complex, buried, and multi-scale structures in a consistent manner. In this review, we present a systematic overview of X-ray characterization techniques for advanced semiconductor systems, including diffraction-based methods, small-angle scattering, computed tomography, X-ray fluorescence, and spectroscopic approaches. These techniques are discussed in terms of the type of structural, morphological, and compositional information they provide, their applicable length scales, and their strengths and limitations in addressing key challenges such as thin films, high-aspect-ratio structures, buried interfaces, and full wafers. Particular attention is given to the complementary nature of different X-ray modalities and their roles in addressing practical metrology problems. The limitations associated with resolution, model dependence, and data interpretation are also outlined. Finally, emerging opportunities in laboratory X-ray sources, synchrotron-based methods, and integrated characterization strategies are briefly discussed. This review aims to provide a unified perspective for understanding and integrating X-ray techniques, offering insights into their roles in addressing the growing complexity of next-generation semiconductor devices.

Crystals doi: 10.3390/cryst16040264

Authors: Tengbo Chen Yuxi Yu Haoran Gao Ronggui Zhang Zhong Luo Shuyuan Zhao

Bi-doped rare-earth iron garnet (Bi:RIG) single crystals are the core of optical isolators, and demand for them is surging due to the development of artificial intelligence (AI) technology. In this work, bismuth-doped terbium iron garnet (Bi:TbIG) single crystals with a composition of Bi0.86Tb2.14Fe5O12 and a size of 37 mm were successfully grown by the top-seeded solution growth (TSSG) method using a lead-containing flux system. These crystals exhibited a regular rhombic dodecahedron morphology enclosed by the {110} plane, and a growth rate of 0.018 mm/h perpendicular to the {110} planes. Systematic characterizations revealed that the crystals exhibited good compositional homogeneity, with no obvious Fe, Tb and Bi segregation from center to edge. Rocking curve tests presented a full width at half maximum of 172 arcsec. X-ray photoelectron spectroscopy (XPS) results demonstrated that Fe exists exclusively in the +3 valence state without detectable Fe2+, whereas Tb is present in the +4 valence state. In addition, O was lattice O2−, without obvious defects. Magneto-optical tests indicated that the uncoated TSSG-grown Bi:TbIG crystals had 71% transmittance in the 1200~1600 nm waveband, and a Faraday rotation coefficient of 0.132°/μm at 1310 nm. The 11 × 11 mm samples exhibited an extinction ratio stably above 40 dB. The 349 μm thick samples meet the application requirements of miniaturized optical isolators. This study verifies the feasibility of TSSG for growing Bi:TbIG single crystals, offering a new technical route for Bi:TbIG growth with potential value for practical application.

Crystals doi: 10.3390/cryst16040263

Authors: Shadrach Stitz William A. Howard Kraig A. Wheeler Natarajan Ganesan David G. Churchill

Well-defined, small-molecule, platinum-centered coordination compounds are of continued interest in both basic and applied research, particularly in medicinal chemistry and pharmaceuticals (i.e., cisplatin). Organoplatinum(IV) complexes have been reported to exhibit substantial in vitro cytotoxicity across a range of cancer cell lines. Compared with coordinatively unsaturated platinum(II) species, electronically and coordinatively saturated platinum(IV) complexes are generally more inert, reducing undesirable side reactions in plasma and cellular environments and potentially improving their safety profiles as chemotherapeutic agents. In addition, the presence of organic ligands can enhance lipophilicity, facilitating passive diffusion across cell membranes. Here, we report the synthesis, structural characterization, and in vitro anticancer activity of a series of organoplatinum(IV) complexes of the general formula Pt(CH3)2I2{n,n′-dimethyl-2,2′-bipyridine} (n,n′ = 4,4′; 5,5′; 6,6′). The 5,5′- and 6,6′-dimethyl isomers were characterized by single-crystal X-ray diffraction. All three dimethyl-substituted complexes, along with the parent compound, Pt(CH3)2I2{2,2′-bipyridine}, were evaluated for cytotoxic activity against a panel of 60 human cancer cell lines. Whereas Pt(CH3)2I2{2,2′-bipyridine} and the 4,4′- and 5,5′-dimethyl derivatives displayed limited cytotoxicity, the 6,6′-dimethyl isomer exhibited notable activity, particularly against the colon cancer cell line HCT-116 (LC50 = 8.17 μM) and the ovarian cancer cell line OVCAR-3 (LC50 = 7.34 μM). The enhanced cytotoxicity of the 6,6′-dimethyl derivative is attributed, at least in part, to the relatively facile dissociation of the 6,6′-dimethyl-2,2′-bipyridine ligand from the platinum(IV) center, suggesting that sterically induced ligand lability plays an important role in modulating biological activity in this particular compound, giving new structural activity impetus for potential drug molecules.

Crystals doi: 10.3390/cryst16040262

Authors: Diandian Zhang Nirosh M. Eldose Dinesh Baral Hryhorii Stanchu Mourad Benamara Wei Du Gregory J. Salamo Shui-Qing Yu

SiSn alloys have attracted growing interest for group-IV bandgap engineering, although their epitaxial growth remains challenging due to the extremely low equilibrium solubility of Sn in Si. In this work, fully strained (pseudomorphic) SiSn epitaxial layers were grown on Si (001) substrates by means of molecular beam epitaxy. A systematic investigation reveals a strong inverse correlation between growth temperature and Sn incorporation efficiency. Despite a constant Sn flux, the incorporated Sn composition decreases from 5.5% to 3.2% as the growth temperature increases, indicating a pronounced temperature dependence of Sn incorporation. Reflection high-energy electron diffraction indicates a gradual transition of the growth from two-dimensional to three-dimensional with increasing film thickness. Structural characterization by means of X-ray diffraction, atomic force microscopy, and transmission electron microscopy confirms the pseudomorphic growth and smooth surface morphology and reveals twins and stacking faults near the surface region. These results establish a quantitative reference for SiSn growth kinetics and provide guidance for future studies of SiSn and SiGeSn alloys in silicon-compatible electronic and optoelectronic applications.

Crystals doi: 10.3390/cryst16040260

Authors: Syrine Sassi Karim Choubani Hafedh Dhiflaoui Wissem Zayani Amir Ben Rhouma Mohammed A. Almeshaal Mohamed Ben Rabha Lotfi Khezami Ahmed Ben Cheikh Larbi Bernabé Mari Soucase Anouar Hajjaji

Successive ionic layer adsorption reaction (SILAR) was used to deposit Cu2O nanosheets on anodized TiO2 nanotubes at different deposition cycles (4, 8, 15, and 20). Compared to the bare TiO2 nanotubes, these coatings were investigated for their tribological behavior (friction, wear and energy loss), scanning and transmission electron microscopy (SEM, TEM), X-ray Diffraction (XRD) was used to characterize Cu2O/TiO2 coatings to study the effect of number of cycles on the morphological and structural properties of the samples; these characteristics engage in determining the wear mechanisms. The assessment of the coating’s adhesion was determined by the obtained critical loads from the scratch test; the 15 cycles Cu2O/TiO2 exhibited higher critical loads, which corresponds to improved adhesion. This sample also showed a low wear volume of 7.5 × 106 µm3 compared to other samples but higher energy loss due to the low shear strength of copper oxide. The friction coefficient, however, decreased from 0.7 for bare TiO2 nanotubes to 0.48 for 20 cycles Cu2O/TiO2 coatings at higher loads, which proves the wear resistance enhancement. Since these coatings will be manufactured for orthopedic and dental implant applications, the corrosion resistance was tested, and the 15 cycles Cu2O-NPs/TiO2-NTs where these coatings exhibited the most favorable combination of a low corrosion current density (1.9 × 10−4 A/cm2) and a noble corrosion potential (−0.3 V/SCE); furthermore, there was a polarization resistance of 2.4 × 104 Ω·cm2 and a protection efficiency of 96.7%, indicating significantly enhanced corrosion resistance as opposed to the other samples.

Crystals doi: 10.3390/cryst16040261

Authors: Luchuan Shi Kai Huang Haoyu Zheng Xiaoming Chen Yuling Dai Yi Peng Jianfa Zhao Xiancheng Wang Changqing Jin

Recently, CuBa2Ca3Cu4O10+δ (Cu1234) has garnered significant interest owing to its distinctive triple-high superconducting properties (118K high Tc, combined with high Jc and high Hirr at liquid nitrogen temperature at ambient pressure) and potential for practical applications. The Cu1234 is initially synthesized at high pressures and is stable at a room temperature range but tends to decompose upon heating above 300 °C at ambient. In this study, we investigate the thermal stability of Cu1234 through annealing at various temperatures and oxygen pressures. It is found that Cu1234 starts to decompose at approximately 350 °C, 550 °C, and 600 °C when annealed at 1 bar, 100 bar, and 150 bar oxygen pressure, respectively. Prior to decomposition, however, the superconducting properties remain largely unchanged. The decrease in oxygen occupancy within the BaO layer of the BaCuO3−δ charge reservoir block is proposed to be the primary cause of the structural instability of Cu1234, while higher oxygen pressures retard oxygen loss from this block. Our result suggests that the decomposition temperature of Cu1234 will further increase with higher oxygen pressure, e.g., possibly to 800 °C at 260 bar if a linear extrapolation is adopted. This study offers important insights for fabricating Cu1234 tapes via the powder-in-tube method.

Crystals doi: 10.3390/cryst16040259

Authors: Roxana Angela Tucaliuc Sergiu Shova Violeta Mangalagiu Ionel I. Mangalagiu

We report here a thorough study concerning the acylation reaction products of 8-hydroxyquinoline with 2-chloroacyl chloride, with new insights and clarifications in respect to the obtained products brought by NMR and X-ray studies. According to the reaction conditions we employed, three compounds could be obtained: 1-(2-chloro-2-oxoethyl)pyridin-1-ium chloride 10, 8-hydroxyquinoline hydrochloride 11, and the acylated product 8-(2-chloroacetoxy)quinolin-1-ium chloride 12. A certain influence of the catalyst and the used solvent was observed, and feasible explanations for product formations were furnished. The structure of the compounds was proved by using 1H- and 13C-NMR spectra as well as single-crystal X-ray diffraction studies for compounds 12 and 11. According to X-ray crystallography, compounds 11 and 12 have a planar structure and exhibit an ionic crystal structure crystallized as a hydrochloride salt of the corresponding organic base. The crystal structures of both compounds are stabilized by intermolecular hydrogen bonds and π-π stacking interactions. In the crystals of compounds 11 and 12, the structural components are interconnected by a system of intermolecular hydrogen bonding, and a similar one-dimensional array is formed via hydrogen bonding and π-π stacking. The further assembling of the structure for 12 and 11 occurs with the formation of a three-dimensional supramolecular network.

Crystals doi: 10.3390/cryst16040258

Authors: Fernando Gazola Iago Zapelini José Assaf

The global demand for biodiesel production is steadily increasing. Conventional homogeneous basic catalysts, while widely used in the industry, face significant drawbacks, such as the requirement for high-quality feedstock, excessive waste generation, and multiple purification steps. In this study, an acidic silane (IM-CPTMS-BS-H2SO4) containing imidazolium and sulfonic groups was synthesized. Heterogeneous catalysts were then prepared by anchoring varying proportions of the silane onto SBA-15 mesoporous solids. These materials were characterized by FTIR, 13C and 29Si NMR, TGA, XRD, CHNS and acidity measurements. The catalysts were evaluated in the transesterification of methyl acetate with ethanol, with increasing catalytic conversions with the amount of grafted IM-CPTMS-BS-H2SO4. Furthermore, increasing the catalyst loading (from 2% to 5% wt.) and the reaction temperature (from 50 °C to 65 °C) led to higher methyl acetate conversion rates.

Crystals doi: 10.3390/cryst16040257

Authors: Shaohua Wang Hua Yuan Xi Liu Rongqiao Wang Gaoxiang Chen Dianyin Hu

The service environment of the turbine blade–disk dovetail joint structure in aero-engines is complex. Uncertainties in material properties and geometry, as well as the failure correlations among multiple locations or components, make reliability assessment challenging. First, a probabilistic life modeling method based on linear heteroscedastic regression is proposed, and the Manson–Coffin probabilistic life models of DD6 and FGH96 alloys at 650 °C are established. Then, the Copula function is introduced to characterize the failure dependence structure, and the effectiveness of the method is verified through numerical examples. Fatigue-critical locations of the dovetail are identified, and a Kriging surrogate model is established to obtain the probabilistic stress distribution at the critical locations. Subsequently, the Copula method is employed to conduct reliability analysis of dovetail structures. The results show that the reliability of multiple dovetails considering correlation lies between that of a single dovetail and that under the assumption of complete independence. Moreover, the life of the entire disk dovetail structure is significantly influenced by the number of dovetails and the required reliability level. Finally, the study is extended to the blade–disk dovetail multi-component system. The results indicate that when correlation is considered, the reliability of both components decreases, and the overall structural life is dominated by the dovetail component with the lower life. The analytical method proposed in this paper provides theoretical support and engineering reference for the reliability design and life assessment of aero-engine rotor structures.

Crystals doi: 10.3390/cryst16040256

Authors: Ali Khalfallah Reza Beygi

Welding and joining of metallic materials are foundational technologies for modern manufacturing in sectors such as aerospace, automotive, marine, and civil infrastructure, where complex assemblies and highly loaded structural components must be produced reliably and at scale [...]

Crystals doi: 10.3390/cryst16040255

Authors: Haythem Nafati Yousra Litaiem Idoumou Bouya Ahmed Karim Choubani Barbara Ballarin Mohammed A. Almeshaal Mohamed Ben Rabha Wissem Dimassi

In the pursuit of sustainable and flexible electronics, polymer-based conductive films offer a promising solution due to their biodegradability, mechanical flexibility, and cost-effective fabrication. This study presents the development of a highly conductive and flexible nanocomposite material based on polyaniline-grafted chitosan (PANI-g-Chs) and Vinavil (Vi, a vinyl glue specifically designed for enhancing the sealability of textiles and paper), serving as a matrix for applications in flexible electronics. The PANI-g-Chs nanocomposite was synthesized via in situ oxidative polymerization, where chitosan nanoparticles (Chs) served as a stabilizing template to prevent PANI aggregation, reducing the particle size from 1700 nm (pristine PANI) to 180 nm (PANI-g-Chs). The resulting composite exhibited exceptional electrical conductivity (77.79 S/m at 25 wt% PANI-g-Chs). Hall effect measurements showed that the carrier mobility increased up to 1162.7 cm2/V·s and the carrier density rose to 6.5.1017 cm−3, confirming efficient charge transport and network formation. Mechanical analysis revealed a 300% increase in the storage modulus for PANI-g-Chs, and thermal studies confirmed stability up to 300 °C. Optical characterization showed a reduced bandgap (3.6 eV) and extended π-conjugation, which are critical for optoelectronic applications. Application tests demonstrated stable conductivity under mechanical deformation, highlighting the material’s potential for use in flexible electronics, sensors, and sustainable conductive coatings. This work offers a viable alternative to conventional conductive polymers.

Crystals doi: 10.3390/cryst16040254

Authors: Hafedh Dhiflaoui Karim Choubani Jabeur Ghozlani Syrine Sassi Wissem Zayani Mohamed Aziz Hajjaji Lotfi Khezami Mohamed Salah Mounir Gaidi Mohamed Ben Rabha Mohammed A. Almeshaal Anouar Hajjaji

TiO2 nanotubes were synthesized using the anodization method on Ti foils and decorated with PbS nanoparticles by the SILAR method at different cycle numbers (10, 15, 20, 25, and 30). These samples were characterized using SEM, TEM, XRD, and microhardness tests. Morphologically, the PbS nanoparticles were evenly dispersed on TiO2 nanotubes in the shape of small spheres. With an increase in the number of cycles, the size and shape of the nanoparticles increased. This also affected the structure and crystallinity of the PbS NPs, as the crystallite size of PbS increased. The in-depth analysis of the tribological characteristics of the coatings conducted using the scratch test allowed us to evaluate the adhesion of the coatings, a crucial aspect in determining their effectiveness and durability. Furthermore, we found that the wear resistance of the coatings increased with the number of PbS cycles up to 15 cycles. However, for the samples with higher size distribution and crystallite size, such as those with more than 15 cycles, the microhardness continued to decrease. This indicates that the addition of PbS can improve the durability of TiO2 coatings, making them a potential candidate for advanced surface coatings in demanding engineering applications. Electrochemical measurements were conducted to assess the corrosion resistance of the samples. The electrochemical impedance spectra (EIS) results revealed that the PbS/TiO2 coatings with 15 deposition cycles exhibited the most effective corrosion resistance, with a dense and uniform distribution of PbS nanoparticles forming a compact barrier that effectively protects against corrosion. The charge transfer resistance (Rct) and the absorption capacitance (Qab) values were higher for the 15-cycle sample (4.49 Ω·cm2 and 0.9 Fsn−1cm−2, respectively).

Crystals doi: 10.3390/cryst16040253

Authors: Vanda Tomková Miroslav Tomáš Stanislav Németh Matúš Horváth Vladimír Kundracík Emil Evin Ján Slota Anna Guzanová Iveta Filipovská

One promising innovative joining process for non-oriented electrical sheets is based on an electro-insulating layer combined with a self-bonding varnish. The aim of this study was to investigate the adhesion of the self-bonding varnish as evaluated by a lap-shear test. During the experiments, non-oriented electrical steels with low to high silicon content were analyzed and tested. The Si content, the bond thickness, and the surface roughness Ra, as well as the selected steel production parameters—such as the radiation tube furnace temperature (RTF), the grain growth temperature (i.e., heating temperature (HF)), the peak metal temperature (PMT), and the annealing atmosphere (dry or humid, controlled by dew point)—were considered as the variables. The results showed that the lap-shear strength was independent of the surface roughness within the investigated range. In contrast, the bond thickness exhibited a weak positive effect on the lap-shear strength, while the Si content showed condition-dependent behavior. The RTF and the HF resulted in a relatively stable mechanical performance, whereas the PMT and the humid annealing atmosphere were identified as critical factors influencing adhesion.

Crystals doi: 10.3390/cryst16040252

Authors: Ilya V. Kornyakov Vladimir N. Bocharov Sergey V. Krivovichev

The new compound Cs2Cu2[V4O12]Br2 was synthesized by the chemical vapor transport reaction method. Structural data obtained by single-crystal X-ray diffraction in the temperature range 100–700 K revealed three successive (with decreasing temperature) structural phase transitions: from the high-temperature aristotype structure I4/mmm (>550 K) to the polymorph P4/mnc (550–340 K), then to P4/m (340–300 K), and finally to the low-temperature phase I4/m (<300 K). The crystal structure of the new compound is based upon the Cu2[V4O12]0 layers, consisting of four-membered rings of corner-sharing vanadate tetrahedra linked by CuO4 squares. Analysis of the structural evolution with increasing temperature shows that the entire sequence of phase transitions is governed by the rotation of the [V4O12]4− rings about the z axis.

Crystals doi: 10.3390/cryst16040251

Authors: Siying Li Yifei Zhao Ailin Tian Dan Li Qicheng Hu

ZnFe2O4 is a promising anode material for lithium-ion batteries (LIBs) due to its high theoretical capacity, but its practical use is limited by poor conductivity and large volume changes during cycling. To address these issues, a ZnFe2O4-reduced graphene oxide (Z-F-rGO) composite was fabricated via solvothermal synthesis and calcination, with Z-F nanoparticles in situ anchored on rGO sheets. Characterizations (XRD, Raman, XPS, SEM, TEM) confirm the formation of highly crystalline spinel Z-F with good interfacial contact with rGO. The Z-F-rGO electrode shows excellent electrochemical performance, maintaining a reversible capacity of 985.4 mA h g−1 after 100 cycles at 0.5 A g−1, significantly higher than the 498.2 mA h g−1 of the Z-F. At 1.0 A g−1, the Z-F-rGO electrode retains 959.4 mA h g−1 after 300 cycles, while the Z-F electrode shows a capacity of 441.3 mA h g−1. CV analysis indicates good reversibility, while EIS and GITT reveal reduced charge-transfer resistance and enhanced Li+ diffusion. This work provides an efficient strategy for scalable Z-F-rGO composites, offering a promising approach for high-performance LIB anodes.

Crystals doi: 10.3390/cryst16040250

Authors: Rutuja U. Amate Pritam J. Morankar Aviraj M. Teli Sonali A. Beknalkar Chan-Wook Jeon

The rational design of electrode materials with tailored composition and architecture is crucial for advancing high-capability electrochemical energy storage systems. This study reports that gadolinium-modified NiFe2O4 nanosheet electrodes were effectively synthesized on nickel foam via a hydrothermal approach followed by thermal treatment. A series of compositions (NiFe, NiFe–Gd1, NiFe–Gd2, and NiFe–Gd3) were prepared to systematically examine the effect of Gd incorporation on structural features and electrochemical properties. X-ray diffraction (XRD) analysis confirmed the formation of the cubic spinel NiFe2O4 phase without detectable secondary phases, indicating that the crystal structure remains intact after Gd introduction. X-ray photoelectron spectroscopy (XPS) further verified the presence of Ni2+, Fe3+, and Gd3+ species within the lattice environment. Morphological analysis using field-emission scanning electron microscopy (FESEM) revealed a nanosheet-based architecture, where the optimized NiFe–Gd2 electrode exhibited a porous and interconnected nanosheet framework with abundant exposed edges. This structural configuration improves electrolyte penetration and facilitates efficient ion transport during charge storage processes. Electrochemical measurements demonstrated that the NiFe–Gd2 electrode delivers an areal capacitance of 5235 mF cm−2 at 10 mA cm−2, along with improved reaction kinetics and low internal resistance. An asymmetric supercapacitor assembled using NiFe–Gd2 as the positive electrode and activated carbon as the negative electrode operated stably within a 0–1.5 V potential window, achieving an energy density of 0.136 mWh cm−2 and a power density of 3.14 mW cm−2, while retaining 86.55% of its initial capacitance after 7000 cycles. These results highlight the potential of rare-earth engineering as a viable strategy for designing advanced spinel ferrite electrodes and pave the way for the development of high-performance, durable, and scalable supercapacitor systems for practical energy storage applications.

Crystals doi: 10.3390/cryst16040249

Authors: Yan Li Xiang Zhang Maoyun Lang Shenwei Chen Peng Hu

Here, we report a comparative scanning tunneling microscopy study of two brominated dibenzo[c,g]carbazole derivatives on Ag(111): 5,9-dibromo-7H-dibenzo[c,g]carbazole (DBC) and 5,9,7-tribromo-7-(4-bromobutyl)-7H-dibenzo[c,g]carbazole (BrBu-DBC). At room temperature (RT), DBC forms ordered paired-row supramolecular assemblies, whereas annealing to 470 K induces the formation of butterfly-like dimers that further organize into periodic arrays, consistent with adatom-mediated N–Ag–N coordination. In contrast, BrBu-DBC shows disordered adsorption at RT but transforms at 490 K into dumbbell-shaped dimers coupled selectively at the terminal side chains, consistent with C–C linkage formation. We demonstrate how subtle functional modification modulates the competition between supramolecular assembly and surface-mediated transformation pathways.

Crystals doi: 10.3390/cryst16040248

Authors: Josip Budimir Sacher Nenad Bolf Manon Rogue

The aim of this work was to explore and test the concept of a novel direct nucleation control method with external dissolution of fine crystals (E-DNC). It was postulated that the heating cycles of the internal DNC method could be transferred from the crystallizer jacket to an electrically heated recirculation tube, thereby using less energy and requiring a shorter time compared to internal DNC. The conceptual model was explored and developed by reviewing previous research on the topic and addressing known drawbacks. Engineering experience and a heuristic approach led to the conclusion that five commonly used controllers would suffice for a straightforward implementation of the method. A simplified simulation was developed to compare the time and energy requirements for the internal and external DNC methods, and it was concluded that external DNC uses 37% less energy and 19% less time compared to internal DNC. The laboratory system was then constructed by modifying the internal DNC apparatus with inexpensive and commonly used components. A linear cooling experiment was performed to establish the baseline for comparison with E-DNC experiments and to set the expected count range. The E-DNC experiments were then conducted with the aim of obtaining larger crystal sizes, and it was shown that the process could be designed in only three experiments. Adjusting the heating rate and count limit led to a significant increase in median crystal size (22.5%) compared to linear cooling.

Crystals doi: 10.3390/cryst16040247

Authors: Ştefan Marincea Delia-Georgeta Dumitraş Frédéric Hatert Cristina Sava Ghineț George Dincă Aurora-Măruța Iancu Martin Depret

Wollastonite-1A from Băița Bihor occurs in distal calcic skarns developed in the contact zone of a mainly granodioritic batholith, of Upper Cretaceous age, with Mesozoic limestones and dolostones. Wollastonite generally occurs in the inner part of metasomatic columns, in monomineralic skarns or associated with grossular and molybdenite-2H as ore mineral. The physical properties (i.e., refraction indices α = 1.616, β = 1.629, and γ = 1.631, 2Vα = 39° and density Dm = 2.922(3) g/cm3) are typical for a term close to the stoichiometry, which is confirmed by the chemical analysis. The chemical structural formula of the analyzed wollastonite-1A is (Ca1.000Mg0.002Mn0.001Fe0.001)(Al0.004Ti0.001Si0.994)O3, which closely approximates the ideal CaSiO3. The Gladstone–Dale compatibility indices account for an excellent agreement between physical and chemical data. The mineral can be satisfactorily refined as triclinic, space group P1¯, with R1 = 0.0678 and cell parameters a = 7.9233(3) Å, b = 7.3203(3) Å, c = 7.0651(3) Å, α = 90.053(3)°, β = 95.208(3)°, γ = 103.384(3)°. Both the IR and Raman spectra principally reveal bands related to vibrations of bridged and non-bridged oxygens pertaining to SiO4 structural tetrahedra. At Băița Bihor, wollastonite-1A is part of the prograde paragenesis, marked by a peak temperature of 550–600 °C.

Crystals doi: 10.3390/cryst16040246

Authors: Okhunjon Sayfidinov Susheng Tan Bakhtiyor Mardonov Makhliyo Sayfidinova Baibhaw Kumar

Steel slags are major by-products of steelmaking, and their variable composition complicates recycling and valorization strategies. This study investigates four representative slag samples obtained from different production pathways at an industrial steel plant in Uzbekistan, using a combined multi-scale characterization approach. Bulk elemental composition was determined using X-ray fluorescence (XRF), while microstructural and phase-level analysis was carried out using scanning electron microscopy with energy-dispersive spectroscopy (SEM–EDS), including both point analysis and automated phase mapping. The XRF results revealed two distinct compositional groups, with one slag dominated by Mn–Si–O chemistry and three slags characterized by high Ca content. SEM–EDS phase mapping further resolved these differences at the microscale, identifying manganese silicate and oxide phases in the Mn-rich slag, Ca–F–O dominant phases in two slags associated with fluorite flux addition, and a more heterogeneous Ca-based system with localized enrichments of Mn, Zn, and Cu in the fourth sample. The combined results demonstrate that slag composition strongly reflects steel grade and fluxing practice. The integration of XRF and SEM–EDS provides a robust framework for linking bulk chemistry with phase distribution, improving slag classification and supporting informed decisions for reuse and environmental management.

Crystals doi: 10.3390/cryst16040245

Authors: Xiaoshan Liu Anping Long Haijie Zhang Dexin Ma Min Song Menghuai Wu Jianzheng Guo

This paper investigates the formation mechanism and key influencing factors of freckle defects that arise during the directional solidification of a novel third-generation nickel-based single crystal superalloy turbine blade. A combined experimental and multi-physics numerical simulation approach was adopted. The results indicate that freckle formation primarily originates from solutal convection, which subsequently triggers a cascade of processes, including the development of convection-induced segregation channels, flow-driven dendrite fragmentation, and the migration and aggregation of dendrite fragments. The severity of freckling is closely dependent on both the casting’s position within the furnace and its local geometric characteristics. Castings located in regions with poorer heating conditions exhibit lower temperature gradients and slower solidification rates, significantly increasing their susceptibility to freckle formation. Similarly, on a given casting, the side subjected to less favorable heating is more prone to freckle initiation. The freckle number varies non-monotonically along the blade height, increasing from 3 to a maximum of 16, with a temporary decrease near the platform and a final reduction near the top. This trend is mainly attributed to thickness-dependent channel segregation, as well as freckle propagation into the interior and coalescence at higher positions. This study provides a crucial theoretical basis for understanding the formation mechanism of freckle defects in nickel-based single crystal superalloys and offers valuable guidance for optimizing blade manufacturing processes, reducing solidification defects, and enhancing blade quality and service performance.

Crystals doi: 10.3390/cryst16040244

Authors: Shanquan Deng Junwei Zhu Xingsen Zhang Meihua Bian Yuyin He

With the rapid transition of power transmission systems toward higher capacity, longer distance, and improved efficiency, aluminum alloys from the 6xxx (Al–Mg–Si) and 8xxx (Al–Fe) series have become key structural materials for overhead conductors and power cables due to their low density, cost effectiveness, and favorable strength–conductivity balance. Compared with traditional steel-reinforced conductors, optimized aluminum alloy conductors can reduce structural weight by approximately 30–40% and installation cost by about 20–30%, while maintaining comparable current-carrying capacity. This review systematically focuses on modification methods and research progress of aluminum alloy cores for electric wires and cables. The strengthening characteristics of 6xxx alloys (heat-treatment responsiveness and precipitation strengthening) and the creep-resistance stability of 8xxx alloys are comparatively analyzed. Four core performance requirements—high electrical conductivity, mechanical strength, creep resistance, and corrosion resistance—are summarized as evaluation criteria for conductor applications. Particular emphasis is placed on three major modification strategies: (1) microalloying (e.g., Zr, Sc, rare earth elements) for precipitation and dispersoid stabilization; (2) thermomechanical process optimization for grain refinement and strength–conductivity balance; (3) composite reinforcement for high-temperature and ultra-high-strength applications. Quantitative literature data indicate that microalloying and process optimization typically achieve 15–40% strength improvement with conductivity variation within 3–5% IACS, while composite strategies may provide 30–80% strength enhancement but often at the expense of 5–20% conductivity reduction. The distinct applicability of 6xxx and 8xxx alloys under different service conditions is clarified, providing guidance for conductor material selection. Finally, future research directions—including precise composition–process integration, advanced thermomechanical control, and scalable modification technologies—are proposed to support high-performance, cost-effective, and large-scale deployment of aluminum alloy conductors.

Crystals doi: 10.3390/cryst16040243

Authors: Xianhui Gong Yongli Liu Bin Shen Ruguo Dong Yingwei Liu Jiaqi Yuan Yue Lu

To investigate the structural characteristics of Irn clusters (n = 9–30) and their interaction with NH3, the CALYPSO structure-prediction method was employed to identify the lowest-energy configurations. The Lennard–Jones potential was then used to compute the binding energy and average binding energy, thereby evaluating size-dependent stability. The results show that Irn clusters evolve from relatively open motifs to compact three-dimensional frameworks as n increases. Meanwhile, the average binding energy increases overall and exhibits several locally stable size regions, indicating a pronounced size effect. Based on slab and cluster models, NH3 adsorption was further examined on the Ir13 cluster as a representative system due to its high structural stability as a “magic-number” cluster. The calculated adsorption energies demonstrate that the Ir13 cluster exhibits substantially stronger adsorption than the bulk Ir surface, with low-coordinated Ir atoms playing a key role in strengthening the interaction and enhancing adsorption activity. Adsorption-configuration analysis indicates that NH3 preferentially binds to active surface sites via the N lone pair. These findings clarify the relationship between structural stability and adsorption performance of Ir clusters and provide theoretical support for Ir-based materials in NH3 catalytic conversion and high-sensitivity gas detection, and offer insights relevant to improving NH3 monitoring in underground coal mine environments.

Crystals doi: 10.3390/cryst16040242

Authors: Haoran Cui Theodore Maranets Yan Wang Yifei Jin Lei Cao

Polymers are widely used in applications ranging from flexible electronics and thermal interface materials to structural composites and textile fabrics. Their inherently low κ, strongly governed by molecular structure and morphology, makes polymers a challenging yet scientifically rich class of materials for thermal transport studies. Over the past two decades, modeling and simulation have played a central role in elucidating heat transport mechanisms in polymers and in guiding the rational design of polymer systems with enhanced or tunable thermal properties. This review provides a comprehensive overview of the theoretical frameworks and computational approaches used to model thermal transport in polymers. We discuss atomistic methods including density functional theory, molecular dynamics, and first-principles Boltzmann transport equation approaches, as well as emerging data-driven and machine learning-based techniques. Special attention is devoted to the effects of chain conformation, crystallinity, orientation, interchain coupling, interfaces, and nanocomposite architectures. Current challenges and future research directions are highlighted, with particular emphasis on multiscale modeling, method integration, and predictive materials design.

Crystals doi: 10.3390/cryst16040241

Authors: Faiz M. Kakar Parichehr Pourattar Christian Pritzel Torsten Kowald Manuela S. Killian

Gypsum (CaSO4·2H2O) crystallization is highly sensitive to the supersaturation pathway, which governs the balance between nucleation and crystal growth and ultimately controls growth morphology. In this study, gypsum was synthesized via two contrasting routes—diffusion-controlled crystallization and rapid precipitation—using identical reactant systems to enable a direct comparison of distinct kinetic regimes. A polycarboxylate-based superplasticizer was incorporated to investigate pathway-dependent additive effects. Time-resolved observations reveal that rapid precipitation is characterized by high nucleation density under steep supersaturation, whereas diffusion-controlled crystallization proceeds under gradually increasing supersaturation with restricted nucleation and sustained anisotropic growth. Powder X-ray diffraction confirms the formation of phase-pure gypsum under all conditions. Scanning electron microscopy shows that the presence of the superplasticizer reduces crystal number density and modifies crystal habit in both pathways, although the extent and manifestation of these effects depend strongly on the governing kinetic regime. Under diffusion-controlled conditions, the increasing superplasticizer dosage promotes the transition from elongated to more tabular morphologies, while rapid precipitation results in dense, intergrown aggregates under high supersaturation. Overall, the results demonstrate that the effectiveness of the superplasticizer is not intrinsic but depends on the crystallization pathway. These findings provide new insight into how supersaturation profiles mediate the interplay between additive interactions and growth processes, enabling improved control over gypsum crystal morphology.

Crystals doi: 10.3390/cryst16040240

Authors: Mohammad H. AlRefeai Fahad Alkhudhairy

The study aimed to evaluate the effect of chlorhexidine (CHX), chlorin p6-mediated photodynamic therapy (PDT), magnesium oxide nanoparticles (MgONPs), and Clp6-functionalized MgONPs on smear layer removal and shear bond strength of a two-step etch-and-rinse adhesive to caries-affected dentin. Seventy-five human permanent molars with occlusal carious lesions and ICDAS scores of four and five were included. Twenty-five samples were used to prepare dentin discs 2 mm in thickness. The remaining samples, along with 25 discs, were arbitrarily allocated into five disinfectant groups, with n = 15 per group (10 teeth and 5 discs). Group I: Control, Group II: 2% CHX, Group III: Clp6-mediated PDT, Group IV: MgONPs, and Group V: Clp6-functionalized MgONPs. SL removal assessment, nanoparticle characterization, and EDX were performed using SEM. Fifty CAD were etched, followed by fifth-generation adhesive application and composite build-up. SBS and failure modes were evaluated with a universal testing machine and stereomicroscope, respectively. Group 4 (MgONPs) specimens displayed the maximum cleaning of SL (1.11 ± 0.13) and the highest SBS (10.32 ± 0.18 MPa). However, minimum SL removal (2.87 ± 0.94) and bond strength (7.42 ± 0.25 MPa) were exhibited by Group 1 (No disinfectant) samples. MgONPs possess the potential to be used as a cavity disinfectant, as they efficiently remove SL from CAD and augment the bond integrity outcomes.

Crystals doi: 10.3390/cryst16040239

Authors: Shirong Zhang Zhijie Wang Zhaoqiang Li Xin Yuan Yiqing Guo Yingjie Sun Xiangming Li Yongkun Li Rongfeng Zhou

Conventional casting of 5N5 high-purity aluminum often results in coarse grains, microstructural inhomogeneity, and a low equiaxed grain area fraction. Vacuum casting in a graphite mold was integrated with multidirectional mechanical vibration to refine and homogenize the solidification microstructure. A three-factor, three-level Box–Behnken design combined with response surface methodology was employed to optimize pouring temperature (A), mold temperature (B), and vibration frequency (C), with the average grain size (Y1) minimized and the average shape factor (Y2) and equiaxed grain area fraction (Y3) maximized. Analysis of variance indicated statistically significant quadratic models with a non-significant lack of fit. The predicted optimum (A ≈ 714 °C, B ≈ 363 °C, C ≈ 37 Hz) was validated experimentally, producing a refined and highly equiaxed structure (Y1 ≈ 0.85 ± 0.02 mm, Y2 ≈ 0.84 ± 0.04, Y3 ≈ 88.6 ± 2.11%), consistent with model predictions. Multidirectional vibration strengthens melt convection and interfacial shear, which is considered to promote grain multiplication and increase the number of effective nuclei, thereby accelerating the columnar-to-equiaxed transition and improving microstructural uniformity.

Crystals doi: 10.3390/cryst16040237

Authors: Peng Tang Mingyi Zheng Kang Wang Xingzhi Pang

Aluminium, as the most abundant metallic element in the Earth’s crust, holds a pivotal position in modern industry due to its exceptional combination of a low density, high specific strength, excellent workability, superior corrosion resistance, and remarkable recyclability [...]

Crystals doi: 10.3390/cryst16040238

Authors: Boyu Ning Xuefei Chen Go Inoue Ling Yu Heba Elsubeihi Morihiro Takamatsu Lin Fan Yasushi Shimada

Soaking bovine tooth blocks in demineralization solution is a widely used method to simulate caries-like demineralization for further experimental studies. The objective of this study was to evaluate the degree and depth of mineral loss in bovine enamel and dentin blocks under various controlled conditions and to investigate the relationships between these factors and mineral loss, providing guidance for researchers to achieve targeted demineralization outcomes. A total of 54 enamel blocks and 54 dentin blocks were divided into 18 groups according to the exposed area and solution volume and then immersed in demineralization solution. Micro-CT scans were performed before immersion, as well as after 1, 2, 3, 7, and 10 days of immersion. The results were analyzed using data analysis software and subsequently summarized into graphical representations. The analysis revealed that soaking time and solution volume showed positive correlations with mineral loss, whereas the exposed area was negatively correlated with mineral loss. Mean mineral loss increased significantly with immersion time in all groups (e.g., from 6314 to 25,670 vol%·μm in the dentin 3 × 3 mm2, 50 mL group, p < 0.05). After 7 days, specimens immersed in larger solution volumes showed significantly greater mineral loss than those immersed in smaller volumes (p < 0.05). In addition, larger exposed areas resulted in greater mineral loss after 3 days of immersion. Mean mineral loss followed a power function relationship with time when the solution volume was sufficiently high relative to the exposed surface area. In contrast, when the solution volume was limited, a logarithmic relationship between time and mineral loss was observed. Given its superior stability, the mean mineral loss appears to be a more reliable indicator for assessing tooth demineralization. Based on our results, more controlled and reproducible demineralization conditions can be achieved, which may contribute to improving the reliability of in vitro caries models and facilitating the evaluation of preventive and therapeutic strategies.

Crystals doi: 10.3390/cryst16040236

Authors: Quanwei Wang Zonggui Li Yanuo Cui Jiashuo Zhang Huilin Li Wei Li

This study aims to systematically investigate the influence of substituent effects on the strength of Lewis acid–base interactions in frustrated Lewis pairs (FLPs). Specifically, -C6F5 groups of the classical Lewis acid B(C6F5)3 are sequentially replaced with -C6Cl5, -C6Br5, and -C6I5 groups, and the Lewis acids are paired with the Lewis base 1,3-disubstituted imidazol-2-ylidene (ItBu) to form FLPs. Further energy decomposition analysis (sobEDA), orbital analysis, and molecular fragment density difference (MFDD) analysis reveal the nature of the substituent effect on the interaction energy (∆Eint) of the FLPs. The research findings indicate that the ∆Eint of B(C6F5)3-ItBu, B(C6F5)x(C6Y5)3−x-ItBu (x = 0, 1, 2; Y = Cl, Br, I) originates mainly from the interaction between the outermost halogen atom of the Lewis acid and the central carbon (C) atom of the Lewis base, rather than from the interaction between the central atoms boron (B) and carbon (C). This mechanism ultimately leads to a ∆Eint for B(C6F5)2(C6Y5)-ItBu (Y = Cl, Br, I) that is comparable to that of B(C6F5)3-ItBu. This indicates that modified B(C6F5)2(C6Y5) (Y = Cl, Br, I) exhibits greater potential for the construction of novel FLPs.

Crystals doi: 10.3390/cryst16040235

Authors: Chong Chen Tian-Tian Sun Xin-Ya Zhou Mei-Feng Chen Qian-Feng Zhang

Treatment of palladium precursor Pd(PPh3)Cl2 with equivalent arylfluorodithiophosphato ligand [PPh4][(4-EtO-C6H4)FPS2] in chloroform at reflux resulted in a mononuclear palladium(I)–sulfur complex cis-[Pd(PPh3)2{κ2-S,S′-(4-EtO-C6H4)FPS2}]. This complex was characterized by UV-Vis and IR spectroscopic analysis, thermogravimetric analysis, and XPS analysis, and its molecular structure has been established by single-crystal X-ray diffraction. SBA-15, as a mesoporous material, was selected as a mesoporous silica substrate to further form a homogeneous catalyst, Pd@SBA-15, which has been characterized by IR spectroscopy, electron microscope and N2 adsorption–desorption test. In addition, the catalytic activity of Pd@SBA-15 for the Suzuki–Miyaura cross-coupling reaction was also investigated.

Crystals doi: 10.3390/cryst16040234

Authors: Alexandru Turza Marieta Muresan-Pop Maria O. Miclaus Gheorghe Borodi

Synthetic derivatives of testosterone known as 17α-alkylated anabolic–androgenic steroids have been developed to retain anabolic effects while enabling oral administration. Here, we present newly identified hydrated solid forms of three agents: oxandrolone hemihydrate (C19H30O3·0.5H2O), fluoxymesterone hydrate (C20H29FO3·H2O), and methandienone hemihydrate (C20H28O2·0.5H2O). Their crystal structures were determined using single-crystal X-ray diffraction, supplemented by powder X-ray diffraction and thermal analyses. Computational methods were employed to investigate molecular interactions and crystal packing. Lattice energy evaluations revealed that the hydrated forms are energetically less stable than their anhydrous counterparts, with significantly less negative values (e.g., −113.4 kJ/mol for oxandrolone hemihydrate vs. −164.4 kJ/mol for the anhydrous form). Energy decomposition analysis indicates that while water molecules participate mostly in electrostatic-driven hydrogen bonding, they disrupt the dispersive packing efficiency found in the anhydrous phases. Specifically, intermolecular interaction energies show that host–host hydrogen bonds (up to −62.2 kJ/mol in oxandrolone) dominate over weaker host–water couplings (−8.9 to −34.9 kJ/mol). The newly reported crystal structures contribute to the expanding catalog of solid-state forms for 17α-alkylated steroids and provide important details regarding their metastable nature and the dehydration-driven phase transformations observed under climatic stress conditions.

Crystals doi: 10.3390/cryst16040233

Authors: İrem Köklü Dağdeviren Umut Dağdeviren Turan Korkmaz

Resin-matrix ceramics are among the increasingly preferred dental biomaterials in restorative dentistry. However, these materials are continuously exposed to staining from beverages in the oral environment, and continue to present limitations in terms of long-term aesthetic performance. This study was designed to evaluate the effects of different surface finishing procedures and immersion in commonly consumed beverages on the color change (ΔE00) of four different resin-matrix ceramics (Cerasmart, Lava Ultimate, Shofu Block HC, and Vita Enamic). A total of 256 specimens were randomly assigned to mechanical polishing or glazing, then immersed in coffee, red wine, cola, or distilled water for 14 days. Data were analyzed using three-way repeated-measures analysis of variance (ANOVA), with Tukey and Bonferroni post hoc tests (α = 0.05). Surface finishing procedure, material type, beverage type and immersion time significantly affected ΔE00 values (p < 0.05). The highest ΔE00 values were observed at 14 days in the red wine-immersed glaze groups of Shofu Block HC (ΔE00 = 7.44 ± 0.45) and Lava Ultimate (ΔE00 = 7.24 ± 0.83). These findings suggest that surface finishing procedures and material selection play a critical role in preserving the aesthetic performance of resin-matrix ceramic restorations, and mechanical polishing may be considered a clinically favorable approach for computer-aided design and computer-aided manufacturing (CAD/CAM) restorations.

Crystals doi: 10.3390/cryst16040232

Authors: Rongrong Ye Rong Yang Lina Hu Zan Li Ziping Luo Xiaoyi Chen

Responsive photonic crystals, as a class of intelligent photonic materials that can generate optical signals in response to external stimuli including temperature, pH, humidity, electric fields, magnetic fields, and specific molecules, exhibit great application potential in sensing and detection, drug delivery, environmental monitoring, and other fields. This is attributed to their unique tunable photonic band gaps and visual sensing characteristics. In this paper, we systematically review the main preparation methods, including the sol–gel method, photolithography, electrochemical deposition, self-assembly, and 3D printing, and compare the advantages and limitations of each method in terms of key performance indicators, cost, applicable material systems, and scalability for large-scale production. The design strategies of photonic crystals based on different response mechanisms are discussed in detail, revealing the structure–activity relationship between external stimuli and the modulation of photonic band gaps. Meanwhile, the typical applications of responsive photonic crystals in the sensing field are comprehensively summarized, with an emphasis on the latest advances in biomedical sensing, environmental monitoring, and intelligent detection. Finally, in view of the current challenges facing responsive photonic crystals, future development directions are prospected, which provides a reference for promoting the translation of responsive photonic crystals from laboratory research to industrial applications.

Crystals doi: 10.3390/cryst16040231

Authors: Ghadah M. Al-Senani Salhah D. Al-Qahtani Lamia M. Alotaibi Wajd H. Alsahli Lujain K. Alanazi Abeer M. Alshalwi Noura A. Alhamidi Ghaday T. Alsubaie

Hybrid material-derived adsorbents have demonstrated exceptional efficacy in a variety of fields, including environmental cleanup and manufacturing operations. In this study, zinc oxide nanoparticles modified with carbon (ZnO-C) as hybrid adsorbent materials were synthesized using both expired zinc chloride and corncob extract. Hybrid ZnO-C adsorbents were employed for the removal of heavy metals, Co(II), and Ni(II) ions, from wastewater via adsorption. Transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and energy dispersive spectroscopy (EDS) were among the methods used to fully characterize the structural and morphological properties. To maximize the adsorption process for every metal ion, kinetic and equilibrium studies were carried out. Results revealed that the ZnO-C material formed crystalline, spherical granules with nanoparticle sizes ranging from 25 nm, embedded within a carbon matrix. Additionally, these spherical zinc oxide particles tended to aggregate into clusters. FTIR analysis indicated that the surface of ZnO-C was rich in hydroxyl (OH) groups and zinc oxide, which play a crucial role in the adsorption mechanism. The capacity of ZnO/CC-NPs to adsorb cobalt and nickel ions from aqueous solutions was investigated, examining the influences of initial ion concentration, pH levels, contact duration, and temperature. The findings highlight the high efficiency of ZnO/CC-NPs as an adsorbent, promoting the reuse of waste materials and supporting environmental sustainability efforts.

Crystals doi: 10.3390/cryst16040230

Authors: Agnieszka Syntfeld-Każuch Tomasz Szczęśniak Abdellah Bachiri Kamil Brylew Vitalii I. Gorbenko Tetiana Zorenko Yurii Syrotych Oleg Sidletskiy Yuriy Zorenko

In this work, we present a study of newly developed two-layered composite scintillators based on epitaxial structures of garnet compounds for the simultaneous registration of different components of mixed radiation fluxes, and we evaluate their α/β/γ discrimination performance. The composite scintillators under study were doubly layered structures composed of TbAG:Ce or TbAG:Ce,Mg single-crystalline film grown onto Czochralski-grown GAGG:Ce single-crystal substrates using the liquid-phase epitaxy (LPE) method. The spectrometry measurements were performed with four different radioactive sources: 137Cs (emitting 661.6-keV γ rays), 241Am (5.5-MeV α particles and 59.5-keV γ rays), 90Sr (β particles with energies up to 2 MeV), and 14C (β particles with energies up to 156 keV). The pulse-height spectra (PHS) were recorded with a shaping time of 10 μs in an amplifier due to the presence of long scintillation components in the tested samples. Scintillation time profiles were measured under excitation of 661.6-keV γ rays, 5.5-MeV α particles, and β particles from 90Sr/90Y and 14C. Both types of TbAG:Ce film/GAGG:Ce substrate and TbAG:Ce,Mg film/GAGG:Ce substrate composites show good ability for the simultaneous registration of the mentioned components in the mixed radiation field with very reasonable Figure-of-Merit values: FoM(τ) greater than 0.2 and FoM(PSD) greater than 1.0.

Crystals doi: 10.3390/cryst16040229

Authors: Nduduzo Lungisani Khumalo Ntombenhle Mchunu Samson Masulubanye Mohomane Vetrimurugan Elumalai Tshwafo Elias Motaung

Cadmium contamination of water resources represents a serious environmental and public health challenge, with conventional treatment methods often proving inadequate for industrial-level remediation. In this study, we present a novel, sustainable composite material, functionalized cellulose nanocrystal polyvinyl alcohol zinc oxide ferric chloride (CNC-PVA-ZnOFe) beads for the efficient removal of cadmium from contaminated water. The material integrates adsorption, coagulation, and flocculation mechanisms within a single hybrid platform, with coagulation–flocculation serving as the dominant mechanism given the material’s macroporous structure and limited surface area (1.2–3.3 m2/g). Functionalized cellulose nanocrystals provide supporting adsorptive sites for metal binding, while a PVA matrix incorporating ZnOFe improves structural integrity, mechanical stability, and coagulation performance. Characterization confirmed successful functionalization, enhanced thermal stability, and a macroporous structure (12–52 nm pores) conducive to floc entrapment, though with limited surface area (1.2–3.3 m2/g) for conventional adsorption. Under optimized conditions (pH 7–10, initial Cd2+ concentration of 100 mg/L, coagulant dose of 0.1 g, and sedimentation time of 60 min), the functionalized CNC-PVA-ZnOFe beads achieved a cadmium removal efficiency of 78%, achieving significantly higher cadmium removal efficiency than traditional coagulants, such as aluminum sulfate (69%). The beads also demonstrated good reusability, retaining 85% removal efficiency after five regeneration cycles. This work presents a scalable, eco-friendly material for cadmium removal under controlled laboratory conditions using synthetic solutions. However, further evaluation in real wastewater matrices containing competing ions and organic matter is necessary to establish practical applicability for water treatment applications. The study highlights the combined potential of multifunctional hybrid materials while acknowledging the need for validation under environmentally relevant conditions. While the results indicate successful integration of multiple removal mechanisms, direct validation of synergistic interactions through techniques such as zeta potential and XPS analysis remains an important direction for future research.