Crystals

21 pages, 12151 KB

Open AccessArticle

Silver-Based Nanoparticles as Antibacterial Materials

by Adriana-Gabriela Schiopu, Mihai Oproescu, Sorin Georgian Moga, Ecaterina Magdalena Modan, Denis Aurelian Negrea, Daniela Istrate, Georgian Vasile Bîrsan and Marian Catalin Ducu

Crystals 2026, 16(2), 124; https://doi.org/10.3390/cryst16020124 (registering DOI) - 8 Feb 2026

Abstract

This study investigates the elaboration, structural characteristics, and antibacterial performance of silver-based nanoparticles obtained via a hydrolytic chemical route, with and without assistance from ultrasound and microwave irradiation. Two silver nitrate precursor concentrations (1 M and 2 M) were employed to evaluate the [...] Read more.

This study investigates the elaboration, structural characteristics, and antibacterial performance of silver-based nanoparticles obtained via a hydrolytic chemical route, with and without assistance from ultrasound and microwave irradiation. Two silver nitrate precursor concentrations (1 M and 2 M) were employed to evaluate the influence of synthesis conditions on phase composition, morphology, and antimicrobial efficiency. The obtained powders were characterized by ATR-FTIR, X-ray diffraction (XRD), and scanning electron microscopy (SEM). XRD analysis revealed that drying at 120 °C led to oxide-rich systems dominated by Ag₂O, with minor contributions from metallic Ag and carbonate species, while calcination at 550 °C resulted in complete phase transformation into highly crystalline metallic silver. SEM observations demonstrated that precursor concentration and synthesis assistance strongly affect particle size, aggregation degree, and surface morphology. Ultrasound- and microwave-assisted synthesis promoted finer crystallite sizes and more homogeneous particle distributions compared to non-assisted routes. The antibacterial activity was evaluated against Escherichia coli (Gram-negative) and Clostridium perfringens (Gram-positive, anaerobic, spore-forming). Oxide-rich samples, particularly Ox.Ag/2 M, exhibited rapid and complete bacterial inactivation within 30 min, while metallic silver samples showed time-dependent antibacterial behavior, achieving full inhibition after 4 h. The results demonstrate that antibacterial efficiency is governed by a synergistic interplay between silver oxidation state, nanoscale morphology, and surface reactivity. These findings highlight the potential of tailored silver-based nanomaterials as effective antibacterial materials for biomedical, food safety, and environmental applications. Full article

(This article belongs to the Special Issue Emerging Nanostructured Powders: Synthesis and Applications)

15 pages, 3323 KB

Open AccessArticle

The Role of Carbon Content in the Microstructural Evolution and Electrochemical Corrosion Performance of Steel Blades Processed by Clay-Coated Quenching: A Comparative Study

by Wei Wu, Lijuan Diao, Huairu Ma, Wenming Tian and Lizhong Wu

Crystals 2026, 16(2), 123; https://doi.org/10.3390/cryst16020123 (registering DOI) - 7 Feb 2026

Abstract

Coating a sword’s surface with clay before quenching in water not only produces distinctive patterns but also modifies its hardness and corrosion resistance. This study investigated two steel swords with differing carbon contents (L01 containing 0.69% C and L02 containing 0.98% C) subjected [...] Read more.

Coating a sword’s surface with clay before quenching in water not only produces distinctive patterns but also modifies its hardness and corrosion resistance. This study investigated two steel swords with differing carbon contents (L01 containing 0.69% C and L02 containing 0.98% C) subjected to the clay-coated quenching process to assess its impact on the blades’ microstructure, hardness, and corrosion characteristics. Samples from each sword underwent analysis through metallography, microhardness tests, electrochemical tests, and scanning electron microscopy. The investigation revealed that L02 comprising martensite, pearlite, retained austenite and carbides, exhibited a greater diversity of microconstituents than L01 containing martensite and pearlite. In addition, the hardness range of L02 (425~1050 HV) showed a broader hardness spectrum than that of L01 (HV 550~846), further illustrating that L02 possessed a higher degree of microstructural gradation and better balance of hardness and toughness. However, the electrochemical tests showed that each test area of L01 exhibited consistently lower corrosion rates than their counterparts on L02. The i_corr values for L01 ranged from 5.12 to 8.29 μA·cm⁻², while L02 had i_corr values between 21.17 and 25.23 μA·cm⁻². Importantly, the calculated R_p values across the different zones of L01 (ranging from 2338 to 4129 Ω·cm²) exceeded those of the corresponding zones of L02 (ranging from 502 to 816 Ω·cm²). The electrochemical impedance spectroscopy (EIS) data revealed that the R_ct values for L01 (ranging from 2016 to 2837 Ω·cm²) were also greater than the corresponding values for L02 (range: 424~571 Ω·cm²). The data indicated that L02 exhibited inferior corrosion resistance compared to L01, attributable to its higher carbon content. This increased carbon content facilitated the development of a more heterogeneous and diversified microstructure during clay quenching, resulting in a greater electrochemical potential difference and subsequently accelerating corrosion. These insights delineate a distinct microstructure–corrosion relationship in gradient steel blades processed by clay-coated quenching and offer practical guidance for selecting carbon content to enhance both mechanical properties and corrosion resistance in traditionally crafted blades. Full article

(This article belongs to the Special Issue Corrosion Phenomena in Metals)

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13 pages, 2934 KB

Open AccessArticle

High-Resolution X-Ray Imaging Using Cs₃Cu₂Br_1.25I_3.75 Scintillator Arrays Grown by In Situ Solution Processing

by Xinlin Li, Zhenxin Yan, Baoyu Zhou, Junhua Hu, Ziyu Zhao and Tao Lin

Crystals 2026, 16(2), 122; https://doi.org/10.3390/cryst16020122 (registering DOI) - 7 Feb 2026

Abstract

Low-dimensional lead-free metal halide perovskites have demonstrated excellent performance in indirect X-ray detectors; however, the imaging resolution remains limited due to the lack of effective scintillation waveguiding. In this work, array-structured scintillation screens were fabricated using anodic aluminum oxide (AAO) templates via a [...] Read more.

Low-dimensional lead-free metal halide perovskites have demonstrated excellent performance in indirect X-ray detectors; however, the imaging resolution remains limited due to the lack of effective scintillation waveguiding. In this work, array-structured scintillation screens were fabricated using anodic aluminum oxide (AAO) templates via a spatial confinement–assisted in situ growth strategy. The resulting directional optical confinement effect significantly enhances the scintillation performance of the screen. The fabricated Cs₃Cu₂Br_1.25I_3.75-AAO scintillator arrays achieve a spatial resolution of 14.10 lp/mm and a minimum detectable dose rate of 243 nGy/s under X-ray irradiation. In addition, the scintillator arrays exhibit excellent radiation stability, providing a reliable and cost-effective solution for high-resolution array-based X-ray imaging. Full article

(This article belongs to the Special Issue Advances in Scintillators: Luminescence Properties and Applications)

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31 pages, 12617 KB

Open AccessArticle

Laser Power and Scan Speed Effects on Density, Surface Quality, and Mechanical Properties of PBF-LB/M Ti-6Al-4V

by Alexandru Paraschiv, Adrian Bibis, Romica Constantin Stoica, Sebastian-Gabriel Bucaciuc, Claudiu Visan and Florina Branzoi

Crystals 2026, 16(2), 121; https://doi.org/10.3390/cryst16020121 - 6 Feb 2026

Abstract

This study investigates how laser power–scan speed combinations influence densification, surface quality, and mechanical performance of Ti-6Al-4V parts fabricated by Powder Bed Fusion–Laser Beam/Metal (PBF-LB/M) on a DMG MORI LASERTEC 30 SLM (2nd generation) system. A parametric matrix was explored by varying laser [...] Read more.

This study investigates how laser power–scan speed combinations influence densification, surface quality, and mechanical performance of Ti-6Al-4V parts fabricated by Powder Bed Fusion–Laser Beam/Metal (PBF-LB/M) on a DMG MORI LASERTEC 30 SLM (2nd generation) system. A parametric matrix was explored by varying laser power (150–400 W) and scan speed (0.9–1.4 m·s⁻¹) at constant layer thickness and hatch spacing, deliberately omitting contour exposure to isolate core scan effects. A stable processing window was identified (250–300 W; 0.9–1.0 m·s⁻¹) corresponding to ~50–60 J·mm⁻³ volumetric energy density (VED) achieved at 99.5% with residual porosity of 0.1–0.3%. In this regime, as-built roughness measured Ra = 4–6 µm on top surfaces and Ra = 15–17 µm on side surfaces. Mechanical testing in the as-built showed ultimate tensile strength (UTS) = 1150–1180 MPa and offset yield strength (YS_0.2) = 955–994 MPa, with elongation up to 6.7%. Hardness increased from 220 HV to 360 HV as densification improved. Notably, similar VED values derived from distinct power–speed combinations resulted in divergent outcomes, confirming that VED alone does not uniquely predict quality. Comparative benchmarks from the literature data highlight the performance achieved. The resulting process–property map provides a practical reference for parameter optimization, reproducibility evaluation, and transferability across platforms. Full article

(This article belongs to the Section Inorganic Crystalline Materials)

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18 pages, 4011 KB

Open AccessArticle

Thermodynamic Assessment of Reactions in the Sodium-Oxide Fluxed Aluminothermic Reduction of Manganese Ore with Si, Cr, and Cu Collector Metals

by Theresa Coetsee and Frederik De Bruin

Crystals 2026, 16(2), 120; https://doi.org/10.3390/cryst16020120 - 6 Feb 2026

Abstract

This study investigates the reaction thermodynamics of the sodium oxide-fluxed aluminothermic reduction of pyrolusite-based manganese ore under self-propagating high-temperature synthesis (SHS) conditions, using Si, Cr, and Cu as collector metals. The experimental results are compared with thermochemical equilibrium calculations using FactSage 7.3 thermochemistry [...] Read more.

This study investigates the reaction thermodynamics of the sodium oxide-fluxed aluminothermic reduction of pyrolusite-based manganese ore under self-propagating high-temperature synthesis (SHS) conditions, using Si, Cr, and Cu as collector metals. The experimental results are compared with thermochemical equilibrium calculations using FactSage 7.3 thermochemistry software. Experimental mixtures were prepared with controlled additions of aluminium, sodium silicate, calcium oxide, and collector metals and heated to the ignition temperature in a muffle furnace preheated to 1350 °C. The resulting alloys and slags were analysed for bulk composition. Collector metals significantly influence alloy carbon saturation and manganese recovery. The individual reaction’s Gibbs free energy values and the gas–slag–metal equilibrium were calculated. Discrepancies between the experimental and equilibrium-predicted results highlight the kinetic factors of SHS processes, particularly with respect to aluminium uptake and manganese volatilisation. The main difference is the alloy’s aluminium uptake. The difference between the calculated and experimental aluminium levels is, in part, due to the higher partial oxygen pressure predicted in the gas–slag–metal equilibrium calculations, compared with that of the likely Al–Al₂O₃ governing reaction equilibrium. Short-circuiting of aluminium to the alloy is also a possible contributing factor. The findings provide insights into optimising feed formulations and process parameters for improved manganese recovery. Full article

(This article belongs to the Special Issue Exploring New Materials for the Transition to Sustainable Energy)

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11 pages, 1247 KB

Open AccessArticle

Mechanical and Surface Characterization of Stainless-Steel Nitride Thin Films Deposited at Different Substrate Temperatures

by Faisal Alresheedi

Crystals 2026, 16(2), 119; https://doi.org/10.3390/cryst16020119 - 6 Feb 2026

Abstract

Stainless-steel nitride thin films were deposited onto silicon substrates at different temperatures ranging from 150 to 600 °C using reactive magnetron sputtering. The influence of substrate temperature on nitrogen incorporation, surface roughness, microstructure, and mechanical properties was systematically investigated. X-ray photoelectron spectroscopy (XPS) [...] Read more.

Stainless-steel nitride thin films were deposited onto silicon substrates at different temperatures ranging from 150 to 600 °C using reactive magnetron sputtering. The influence of substrate temperature on nitrogen incorporation, surface roughness, microstructure, and mechanical properties was systematically investigated. X-ray photoelectron spectroscopy (XPS) analysis showed that the nitrogen content increased with substrate temperature, reaching a maximum value of 34 wt.% at 350 °C, while at higher substrate temperatures (450–600 °C), the nitrogen content decreased. X-ray diffraction analysis revealed that the coating structure strongly depends on the substrate temperature. At temperatures above 450 °C, the films comprise a multiphase structure consisting of CrN, bcc-Fe, and Ni. In contrast, films deposited below 450 °C are dominated by the S-phase, corresponding to a nitrogen-supersaturated fcc structure. Scanning electron microscopy (SEM) analyses confirmed microstructural evolution with substrate temperature, showing fine, compact grains at lower temperatures and coarser structures at higher temperatures. Surface roughness measured by a profilometer exhibited a minimum at 350 °C. The mechanical performance of the films was evaluated using micro-Knoop hardness measurements, together with the calculated elastic strain indicator (H/E) and resistance to the plastic deformation parameter (H³/E²). The results showed that hardness and these mechanical indicators reached their maximum values at a substrate temperature of 350 °C. These findings provide valuable insight into the deposition–structure–property relationships of stainless-steel nitride thin films for wear-resistant and protective coating applications. Full article

(This article belongs to the Special Issue Advanced Surface Engineering Materials: Characterization and Properties (2nd Edition))

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15 pages, 493 KB

Open AccessArticle

Lattice Anharmonicity and Grüneisen Parameter Estimation Using X-Ray Diffraction

by Sheetal Jain, Aditya Chugh and Young-June Kim

Crystals 2026, 16(2), 118; https://doi.org/10.3390/cryst16020118 - 6 Feb 2026

Abstract

Powder X-ray diffraction measurements were carried out on various samples to characterize their thermal expansion over a wide temperature range (93–1373 K). Using an effective interatomic potential model, we present a method to empirically estimate the Grüneisen parameter, as well as cubic and [...] Read more.

Powder X-ray diffraction measurements were carried out on various samples to characterize their thermal expansion over a wide temperature range (93–1373 K). Using an effective interatomic potential model, we present a method to empirically estimate the Grüneisen parameter, as well as cubic and quartic anharmonic contributions to the lattice potential. This method is further tested on materials for which thermal expansion data are readily available. For most of the materials surveyed, the Grüneisen parameter values match those reported in the literature, obtained using traditional techniques. Thus, this work presents a novel and convenient Grüneisen parameter estimation method that uses measurements of only one physical property, thermal expansion. Full article

(This article belongs to the Section Inorganic Crystalline Materials)

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12 pages, 2019 KB

Open AccessArticle

Negative Photoconductivity in Ultranarrow-Gap Semiconductors

by Catherine Masie, Alexander Frenkel, Gela Kipshidze, Dmitri Donetski and Gregory Belenky

Crystals 2026, 16(2), 117; https://doi.org/10.3390/cryst16020117 - 5 Feb 2026

Abstract

A decrease in conductivity under illumination, known as negative photoconductivity, has been observed in various semiconductors and is commonly attributed to trapping of excess carriers by deep centers. Here, we demonstrate that negative photoconductivity can instead arise from a rapid increase in carrier [...] Read more.

A decrease in conductivity under illumination, known as negative photoconductivity, has been observed in various semiconductors and is commonly attributed to trapping of excess carriers by deep centers. Here, we demonstrate that negative photoconductivity can instead arise from a rapid increase in carrier scattering in ultranarrow-gap semiconductors with degenerate carrier statistics. This behavior is explained by the combined effects of enhanced optical phonon emission scattering and an increase in effective mass due to band filling. Experimentally, photoconductivity was measured over wide ranges of excitation and temperature in unintentionally doped n-type short-period InAsSb_0.6/InAsSb_0.3 strained-layer superlattices (SLS), relevant for long-wavelength infrared optoelectronic devices. The resistive device impedance, weakly dependent on excess carrier concentration, simplifies broadband impedance matching to low-voltage CMOS driver electronics. At 77 K, 10.6 µm laser excitation led to an initial rise in conductivity, with a decrease observed above 10 W/cm². Full article

(This article belongs to the Special Issue The Cutting Edge of Energy Materials Research Aimed at Practical Application)

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28 pages, 10363 KB

Open AccessArticle

CVD Monolayer MoS₂ Memtransistors for Chaotic Time-Series Prediction via Reservoir Computing

by Vladislav Kurtash, Lina Jaurigue and Jörg Pezoldt

Crystals 2026, 16(2), 116; https://doi.org/10.3390/cryst16020116 - 5 Feb 2026

Abstract

Monolayer MoS

_{2}

memtransistors offer gate-tunable hysteresis for neuromorphic reservoir computing, yet the role of operating window and fading-memory dynamics in CVD devices remains underexplored. We grow CVD monolayer MoS

_{2}

, fabricate back-gated memtransistors, and use a single device as a time-multiplexed [...] Read more.

Monolayer MoS

_{2}

memtransistors offer gate-tunable hysteresis for neuromorphic reservoir computing, yet the role of operating window and fading-memory dynamics in CVD devices remains underexplored. We grow CVD monolayer MoS

_{2}

, fabricate back-gated memtransistors, and use a single device as a time-multiplexed reservoir node for one-step Lorenz-63 prediction. Mobility, ON/OFF, hysteresis, and drift are quantified to identify stable, tunable bias regimes. We used a transistor with field-effect mobility on the order of 10 cm

^{2}

V

^{- 1}

s

^{- 1}

, an ON/OFF ratio above

10^{5}

, and a moderate hysteresis window quantified by

H \approx 2.1 μ

A·V at

V_{DS} = 50

mV and

H \approx 17 μ

A·V at

V_{DS} = 500

mV over

V_{GS} \in [- 10, 30]

V. Performance is bias/memory-limited rather than FET-metric-limited. Sweeping gate-window and reservoir hyperparameters shows an optimum at intermediate hysteresis with moderate drift. Performance improves when the input clock matches the fading-memory time, achieving normalized root mean square error (NRMSE) = 0.09 for one-step Lorenz-63 x-prediction. Device-level statistics (discussed in the main text) show that, despite substantial scattering in electrical parameters, the resulting device-to-device NRMSE variation remains very small under fixed operating conditions. Classical FET metrics are not limiting here; NRMSE improvement instead requires engineering the hysteresis spectrum and gate stack. The demonstration of Lorenz-63 prediction using CVD-grown monolayer MoS

_{2}

memtransistors highlights their potential as a wafer-scalable platform for compact chaotic time-series predictions. Full article

(This article belongs to the Section Inorganic Crystalline Materials)

24 pages, 3591 KB

Open AccessArticle

Synthesis, Antimicrobial and Anti-Inflammatory Activity of a Novel Styrylquinolinium Iodide Bearing a Naphthalene Moiety

by Stoyan Zagorchev, Mina Todorova, Mina Pencheva, Rumyana Bakalska, Tsonko Kolev, Emiliya Cherneva, Mehran Feizi-Dehnayebi, Seyedsobhan Seyedhoseyni, Yulian Tumbarski, Paraskev Nedialkov, Francisco Alonso and Stoyanka Nikolova

Crystals 2026, 16(2), 115; https://doi.org/10.3390/cryst16020115 - 5 Feb 2026

Abstract

The use of styrylium dyes as organic nonlinear optical materials in many photonics domains has been the subject of research for decades. It has been noted that over time, research has also looked into the biological activity of styrylium dyes, namely their antibacterial [...] Read more.

The use of styrylium dyes as organic nonlinear optical materials in many photonics domains has been the subject of research for decades. It has been noted that over time, research has also looked into the biological activity of styrylium dyes, namely their antibacterial effects, as well as attempts to establish links between structure and property by choosing particular structural pieces. These investigations’ scope is still very limited. Therefore, our main goal was to synthesize a styrylium compound with antimicrobial potential. A novel styrylquinolinium compound (D) was synthesized using Knoevenagel condensation. Spectroscopic techniques, including IR, 1D and 2D NMR (COSY, HSQC, and HMBC), HRMS spectra, and X-ray analysis, were used to confirm its structure. The antimicrobial and anti-inflammatory activity of the compound was assessed. The compound was found to have very good antimicrobial activity against five Gram-positive strains, three Gram-negative strains, and fungi. The most pronounced effect of the compound was against Escherichia coli and Pseudomonas aeruginosa. The compound’s anti-inflammatory activity was evaluated through its ex vivo immunohistochemistry. DFT calculations, such as geometry optimization, Molecular Electrostatic Potential (MEP), HOMO–LUMO, reactivity parameters and molecular docking simulation were applied to investigate the electronic features of the compound and confirm the biological activity. The compound (D) demonstrated a promising antibacterial and immunomodulatory profile. Its ability to induce IL-1β and at the same time moderately reduce NOS3 can be considered as a controlled adaptation of the immune response, especially in cases requiring local immune activation. Docking simulation revealed that (D) binds effectively to the active site of the bacterial protein, supporting the experimental findings of the compound’s antibacterial activity. Full article

(This article belongs to the Special Issue Heterocyclic Compounds in Drug Discovery: Synthesis, X-Ray Crystal Structures, Applications and Computational Approaches)

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18 pages, 1815 KB

Open AccessArticle

Influence of Isopropanol on Kinetics of Hydrogen Evolution Reaction Examined at Nickel Foam Electrodes in Alkaline Solution

by Wiktoria Abramczyk, Bogusław Pierożyński, Tomasz Mikołajczyk and Kazimierz Warmiński

Crystals 2026, 16(2), 114; https://doi.org/10.3390/cryst16020114 - 5 Feb 2026

Abstract

The current work examines the impact of isopropanol (IPA) on the electrochemical characteristics of nickel foam and Pd-modified Ni foam electrodes in a 0.1 M NaOH medium, with respect to the kinetics of the hydrogen evolution reaction (HER) over the temperature range of [...] Read more.

The current work examines the impact of isopropanol (IPA) on the electrochemical characteristics of nickel foam and Pd-modified Ni foam electrodes in a 0.1 M NaOH medium, with respect to the kinetics of the hydrogen evolution reaction (HER) over the temperature range of 20–40 °C. Comparative HER/IPA examinations are presented for a highly catalytic polycrystalline Pt electrode. Electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV), and cathodic Tafel polarization experiments were carried out in this work, where the IPA concentrations ranged from 1.0 × 10⁻⁵ to 1.0 × 10⁻³ M. The introduction of small amounts of isopropyl alcohol into the working electrolyte noticeably facilitated the catalytic efficiency of the hydrogen evolution reaction on the surface of Ni foam electrodes. This is most likely related to the fact that IPA molecules undergo partial electrooxidation to acetone (qualitatively confirmed by GC-MS analysis) during initial CV cycling, which is believed to significantly diminish the surface tension phenomenon during the HER, thus promoting hydrogen bubble separation from the electrode surface. It should also be noted that acetone will continuously be produced at the Pt anode, making it essential to consider further migration of (CH₃)₂CO molecules to the working cell compartment. Most importantly, isopropanol was found not to undergo significant surface electrosorption on the nickel foam-based catalysts, which could otherwise significantly inhibit the hydrogen evolution reaction On the contrary, the presence of IPA in the electrolyte solution seems to have a detrimental effect on the kinetics of both the HER and the UPDH (underpotential deposition of H) processes on the surface of the polycrystalline Pt electrode, which is a superior electrochemical catalyst for HER, but highly susceptible to surface contamination. Full article

(This article belongs to the Special Issue Exploring New Materials for the Transition to Sustainable Energy)

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15 pages, 7847 KB

Open AccessArticle

Microstructures of Fe-16wt%S-2wt%Si in Partial and Complete Melt Regions at High Pressures: Implications for Dynamics in Small Planetary Cores

by Erin Lenhart, Wenjun Yong and Richard A. Secco

Crystals 2026, 16(2), 113; https://doi.org/10.3390/cryst16020113 - 5 Feb 2026

Abstract

Regions of partial melt of Fe-S-Si alloys at high pressures may arise during planetary formation or at the boundary of the inner and outer cores of small terrestrial planetary bodies. Melting experiments were performed on Fe-16wt%S-2wt%Si samples in a multi-anvil apparatus across the [...] Read more.

Regions of partial melt of Fe-S-Si alloys at high pressures may arise during planetary formation or at the boundary of the inner and outer cores of small terrestrial planetary bodies. Melting experiments were performed on Fe-16wt%S-2wt%Si samples in a multi-anvil apparatus across the range 2–13 GPa with quench temperatures in partial and complete melt regions. A phase diagram is constructed from electron microprobe analyses, back-scattered electron imaging, and electrical resistivity measurements. Microstructures arising in post-quench samples include Turing patterns of Fe and FeS in the partial melt, dendritic Fe structures with tertiary arms in the partial and complete melt, and Fe-S-Si miscible regions in the complete melt. These melt structures may arise broadly or locally in small Fe-S planetary cores with consequences for the energetics of the core. Full article

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

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7 pages, 173 KB

Open AccessEditorial

Recent Advances in Graphene and Other Two-Dimensional Materials

by Grazia Giuseppina Politano and John Parthenios

Crystals 2026, 16(2), 112; https://doi.org/10.3390/cryst16020112 - 5 Feb 2026

Abstract

Research on breakthroughs in the synthesis and characterization of graphene [...] Full article

(This article belongs to the Special Issue Recent Advances in Graphene and Other Two-Dimensional Materials)

17 pages, 6852 KB

Open AccessArticle

Liquid Crystal Dimers Based on Seven-Membered Bridged Stilbene Exhibiting Twist-Bend Nematic Phases

by Yoshimichi Shimomura, Bi Sheng, Yuki Arakawa, Riki Iwai and Gen-ichi Konishi

Crystals 2026, 16(2), 111; https://doi.org/10.3390/cryst16020111 - 3 Feb 2026

Abstract

We report the first examples of bent-shaped LC dimers based on a seven-membered bridged stilbene. We synthesized nonylene- and ether-linked cyano-terminated dimers (sC9-tCN and sOC7O-tCN, respectively) and a homologous series of nonylene-linked alkyl-terminated dimers ( [...] Read more.

We report the first examples of bent-shaped LC dimers based on a seven-membered bridged stilbene. We synthesized nonylene- and ether-linked cyano-terminated dimers (sC9-tCN and sOC7O-tCN, respectively) and a homologous series of nonylene-linked alkyl-terminated dimers (sC9-tCn) with alkyl carbon atoms n = 1–6. Polarizing optical microscopy, differential scanning calorimetry, and X-ray diffraction measurement were employed to investigate the phase-transition behavior and LC phase structures. sC9-tCN and sOC7O-tCN only exhibited a nematic (N) phase, whereas sC9-tCn (n = 1–5) formed both the N_TB and N phases. sC9-tC5 additionally formed an unidentified X phase from the N_TB phase and sC9-tC6 exhibited a smectic A phase from the N phase. The weak dispersion force and intermolecular affinity provided by the terminal alkyl chains are likely to be preferable to the large dipole–dipole interactions by the cyano termini for the N_TB phase formation of the present dimers. The isotropic points of sC9-tCn showed an odd–even oscillation with n, whereas the N–N_TB phase transition temperatures were comparable. Remarkably, the N_TB stripe textures of sC9-tCn appeared perpendicular to the rubbing direction, and the N–N_TB phase transitions exhibited their second-order nature. This study revealed the unique N_TB phase properties of the 7-membered bridged stilbene-based LC dimers. Full article

(This article belongs to the Collection Liquid Crystals and Their Applications)

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23 pages, 3705 KB

Open AccessArticle

Three Complexes of Zn(II) with Nicotinamide. A Mono-, a Di-, and a Polynuclear Compound

by Laurențiu Pricop, Augustin M. Mădălan, Ioana Cristina Marinas, Mihaela Ganciarov and Anamaria Hanganu

Crystals 2026, 16(2), 110; https://doi.org/10.3390/cryst16020110 - 3 Feb 2026

Abstract

Three complexes of Zn(II) with the general formulas {[Zn(H₂O)₄(4,4′-BiPy)](NO₃)₂·2NA·H₂O}_n(1), [Zn(NA)₂Br₂]·2NA (2), and [Zn₂(CH₃COO)₄(NA)₂]·2H₂O (3), [...] Read more.

Three complexes of Zn(II) with the general formulas {[Zn(H₂O)₄(4,4′-BiPy)](NO₃)₂·2NA·H₂O}_n(1), [Zn(NA)₂Br₂]·2NA (2), and [Zn₂(CH₃COO)₄(NA)₂]·2H₂O (3), where 4,4′-BiPy = 4,4′-bipyridine and NA = nicotinamide, have been synthesized and characterized by means of single-crystal X-ray diffraction (complexes 1 and 2), elemental analysis, FT-IR, fluorescence, ¹H and ¹³C NMR spectroscopy (complexes (2) and (3)), and thermogravimetric analysis. A previously reported complex, [Zn(NA)₂(H₂O)₄](NO₃)₂·2H₂O, was used as a precursor for the synthesis of coordination compounds (1) and (2). X-ray data show that (1) is a 1D polynuclear compound, whereas complex (2) is mononuclear. The Zn(II) ions adopt a slightly distorted octahedral geometry in the polymer and a slightly distorted tetrahedral geometry in the monomer. The antimicrobial activity of complexes (2) and (3) was also evaluated, and complex (3) exhibited superior antimicrobial properties, particularly against the C. albicans strain. Full article

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

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19 pages, 5911 KB

Open AccessArticle

Influence of Acid-Modification on Physical and Photocatalytic Properties of TiO₂ Powders Prepared by Sol–Gel Method

by Bingwu Jiang, Mamatrishat Mamat, Yiliyasi Baikeli and Yilin Jiang

Crystals 2026, 16(2), 109; https://doi.org/10.3390/cryst16020109 - 31 Jan 2026

Abstract

In this work, TiO₂ powders modified with different acids (hydrochloric, nitric and sulfuric) were prepared using the sol–gel method. The XRD spectra demonstrated that the proportion of TiO₂ anatase phase was significantly increased after modification with different acids. SEM confirmed that [...] Read more.

In this work, TiO₂ powders modified with different acids (hydrochloric, nitric and sulfuric) were prepared using the sol–gel method. The XRD spectra demonstrated that the proportion of TiO₂ anatase phase was significantly increased after modification with different acids. SEM confirmed that the grain size was significantly refined, a porous structure was formed, and the agglomeration of the powders was improved. XPS confirmed that the different acids broke the Ti-O bond of the original TiO₂, and the new bond formation inhibited the transformation of the rutile phase during the annealing process. The results of photocatalytic activity tests confirmed that the degradation efficiencies were significantly improved for the all samples after modified by the acids, where the 5% H₂SO₄-TiO₂ shows the best degradation efficiency of 79.5% for tetracycline (TC) antibiotic under 500 W mercury lamp irradiation within 28 min, compare to the hydrochloric, nitric acids. Full article

(This article belongs to the Section Inorganic Crystalline Materials)

14 pages, 665 KB

Open AccessArticle

From the Variational Principle to the Legendre Transform: A Revisit of the Wulff Construction and Its Computational Realization

by Hao Wu and Zhong-Can Ou-Yang

Crystals 2026, 16(2), 108; https://doi.org/10.3390/cryst16020108 - 31 Jan 2026

Abstract

The equilibrium shape of a crystal is a fundamental problem in materials science and condensed matter physics. The Wulff construction, a cornerstone of crystal morphology prediction, is traditionally presented and utilized as a powerful geometric algorithm to derive equilibrium shapes from anisotropic surface [...] Read more.

The equilibrium shape of a crystal is a fundamental problem in materials science and condensed matter physics. The Wulff construction, a cornerstone of crystal morphology prediction, is traditionally presented and utilized as a powerful geometric algorithm to derive equilibrium shapes from anisotropic surface energy

γ (n)

. While its application across materials science is vast, the profound mathematical physics underpinning it, specifically its intrinsic identity as a manifestation of the Legendre transform, is often relegated to a passing remark. This work recenters the focus on this fundamental duality. We present a comprehensive, step-by-step derivation of the Wulff shape from the variational principle of surface energy minimization under a constant volume, employing the language of support functions and differential geometry. We then rigorously demonstrate that the equilibrium shape, defined by the support function

h (n)

, and the surface energy density

γ (n)

are conjugate variables linked by a Legendre transformation; the Wulff shape

W

is precisely the zero-sublevel set of the dual function

γ^{*} (x) = {sup}_{n} [x \cdot n - γ (n)]

. This perspective elevates the Wulff construction from a mere graphical tool to a canonical example of convex duality in thermodynamic systems, connecting it to deeper principles in convex analysis and statistical mechanics. To bridge theory and computation, we provide a robust computational algorithm implemented in pseudocode capable of generating Wulff shapes for two-dimensional (2D) crystals with arbitrary N-fold symmetry. Finally, we discuss the relevance and extensions of the classical theory in contemporary research, including non-equilibrium growth, nanoscale effects, and machine learning approaches. Full article

(This article belongs to the Section Inorganic Crystalline Materials)

34 pages, 5227 KB

Open AccessArticle

Histological and Microstructural Evaluation of Strontium Apatite-Reinforced Mineral Trioxide Aggregate Composites in Experimental Rat Tibial Bone Defects

by Faruk Öztekin, Cevher Kürşat Macit, Turan Gürgenç, Zeynep Toprak, Serkan Dündar, Merve Ayık, Bünyamin Aksakal and İbrahim Hanifi Özercan

Crystals 2026, 16(2), 107; https://doi.org/10.3390/cryst16020107 - 31 Jan 2026

Abstract

Mineral trioxide aggregate (MTA) is a calcium silicate-based endodontic biomaterial widely used for its biocompatibility, sealing ability, and osteoconductive potential; however, further enhancement of its bone regenerative capacity without compromising structural stability remains of interest. Strontium apatite (SrAp), a bioactive calcium phosphate phase [...] Read more.

Mineral trioxide aggregate (MTA) is a calcium silicate-based endodontic biomaterial widely used for its biocompatibility, sealing ability, and osteoconductive potential; however, further enhancement of its bone regenerative capacity without compromising structural stability remains of interest. Strontium apatite (SrAp), a bioactive calcium phosphate phase structurally analogous to bone mineral, may promote osteogenic activity and bone regeneration. In this study, standardized cylindrical defects (2.5 mm diameter, 4 mm depth) were created in the right tibial metaphysis of systemically healthy rats and allocated to four groups: empty defect (control), pure MTA, 25SrAp–MTA, and 50SrAp–MTA. SrAp nanoparticles were synthesized hydrothermally and incorporated into the MTA matrix at predefined weight fractions. Materials were characterized using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDX). After 8 weeks, tibial specimens were harvested and processed for H&E histology; fibrous tissue formation, new bone formation, and osteoblastic cell presence were semi-quantitatively scored. XRD and FT-IR confirmed that SrAp incorporation preserved the fundamental Ca-silicate phase architecture and hydration chemistry of MTA, indicating chemical and crystallographic stability. SEM–EDX demonstrated progressive microstructural densification with increasing SrAp content, with reduced intergranular porosity and homogeneous SrAp distribution. Histologically, both SrAp–MTA groups exhibited significantly higher new bone formation and osteoblastic activity than untreated controls (p < 0.05), while fibrotic tissue formation did not differ significantly among groups. Although SrAp–MTA composites did not show statistically significant superiority over pure MTA after multiple-comparison adjustment, they demonstrated consistent osteogenic trends relative to empty defects. Overall, SrAp reinforcement yields a chemically compatible and structurally stable MTA-based composite that supports an enhanced osteogenic response in vivo without increasing fibrosis, suggesting potential utility in endodontic surgery and bone defect repair; longer-term and quantitative analyses are warranted to optimize SrAp content and confirm long-term performance. Full article

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

21 pages, 17608 KB

Open AccessArticle

The Influence of Key Process Parameters in CMT Arc Welding Repair of ZL114A Aluminum Alloy

by Faming Shen, Xin Ding, Tongge Shao, Zenghui Cai, Qihao Chen, Xiangyu Duan, Bolun Dong and Sanbao Lin

Crystals 2026, 16(2), 106; https://doi.org/10.3390/cryst16020106 - 31 Jan 2026

Abstract

This study employed cold metal transfer (CMT) welding technology to repair defects in ZL114A aluminum alloy, investigating the influence of key repair welding parameters (preheating temperature, overlap amount, wire feed speed, welding speed) and ultimately obtaining defect-free repaired joints with relatively high tensile [...] Read more.

This study employed cold metal transfer (CMT) welding technology to repair defects in ZL114A aluminum alloy, investigating the influence of key repair welding parameters (preheating temperature, overlap amount, wire feed speed, welding speed) and ultimately obtaining defect-free repaired joints with relatively high tensile strength. Using a single-layer, single-pass bead-on-plate method, the effects of wire feed speed and welding speed on the spreading behavior of ZL114A melt on the substrate surface were studied. Through a two-pass, single-layer welding method, the influence of inter-pass overlap amount on the morphology of overlap welds was investigated. The effects of preheating temperature on the morphology, microstructure, and mechanical properties of the repaired specimens were examined by repair welding experiments on spherical crown grooves. The results indicate that to achieve favorable spreading of ZL114A droplets on the base material surface, the welding speed should be greater than 5 mm/s, and the wire feed speed should be within 7–9 m/min. When the overlap amounts are 65%, 70%, 75%, and 80%, the overlap welds are relatively flat, and lack-of-fusion defects are less likely to occur between the two weld passes. As the preheating temperature increases, the porosity defect rate in the repair weld decreases significantly, and the average grain size in the repair zone shows an increasing trend. The average grain size at the center of the repair weld is larger than that in the fusion zone. When the preheating temperature is 350 °C, no obvious porosity defects are observed in the repair weld. The proportion of high-angle grain boundaries increases significantly, and the maximum Kernel Average Misorientation (KAM) value also increases. The room-temperature tensile strength and Vickers hardness of the repaired specimens are superior to those of the original base material, with the tensile strength increasing by approximately 6 MPa and the Vickers hardness increasing by approximately 4 HV. Full article

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

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