Crystals

18 pages, 22094 KB

Open AccessArticle

The Influence of the Chemical Composition of Steel on the Limitation of Austenite Grain Growth in the High-Temperature, Low-Pressure Carburizing Process

by Leszek Klimek and Konrad Dybowski

Crystals 2026, 16(7), 432; https://doi.org/10.3390/cryst16070432 (registering DOI) - 2 Jul 2026

Abstract

High-temperature low-pressure carburizing significantly reduces the time required to produce carburized layers. However, its application promotes austenite grain growth and, consequently, the formation of coarse acicular martensite. In this study, the possibility of limiting this phenomenon in AMS 6265 and 18CrNiMo7-6 steels using [...] Read more.

High-temperature low-pressure carburizing significantly reduces the time required to produce carburized layers. However, its application promotes austenite grain growth and, consequently, the formation of coarse acicular martensite. In this study, the possibility of limiting this phenomenon in AMS 6265 and 18CrNiMo7-6 steels using the PreNitLPC^® technology was evaluated. The process was carried out at 1050 °C, with pre-nitriding applied during charge heating. In both steels, comparable carbon concentration profiles and carburized layers with an effective case depth of approximately 1.0 mm were obtained. The introduction of nitrogen into the surface layer resulted in a local reduction in austenite grain growth compared with the core. The average grain size in the surface layer was approximately 14.5 µm for AMS 6265 steel and 12.5 µm for 18CrNiMo7-6 steel, whereas in the core it increased to approximately 25.1 µm and 24.1 µm, respectively. At the same time, AMS 6265 steel exhibited a higher fraction of retained austenite, approximately 20%, compared with approximately 15% for 18CrNiMo7-6 steel. This resulted in a lower near-surface hardness of AMS 6265 steel, approximately 750 HV0.1, compared with approximately 800 HV0.1 for 18CrNiMo7-6 steel, corresponding to a hardness difference of about 50 HV0.1. TEM/NBD/EDS investigations showed that nanoscale AlN precipitates formed in both steels and acted as the main factor inhibiting austenite grain-boundary migration. The results confirm that the PreNitLPC^® technology enables high-temperature low-pressure carburizing without detrimental grain growth in the surface layer. Full article

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

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13 pages, 10987 KB

Open AccessArticle

LTCC Ceramic Integration of an Ultra-Wideband High-Pass Filter Chip with Notch Suppression

by Chengchao Lv, Xianglu Shan, Xinjiang Luo, Kaixin Song, Xiaopei Deng, Xuan Xie and Changwei Luo

Crystals 2026, 16(7), 431; https://doi.org/10.3390/cryst16070431 - 1 Jul 2026

Abstract

This paper presents a miniaturized ultra-wideband high-pass filter integrated with a notch function based on low-temperature co-fired ceramic (LTCC). The design motivation is to realize continuous wideband high-pass transmission while rejecting a narrow in-band interference/leakage component in compact RF front-end modules. The proposed [...] Read more.

This paper presents a miniaturized ultra-wideband high-pass filter integrated with a notch function based on low-temperature co-fired ceramic (LTCC). The design motivation is to realize continuous wideband high-pass transmission while rejecting a narrow in-band interference/leakage component in compact RF front-end modules. The proposed design employs a cascaded structure of a seventh-order quasi-elliptic HPF and a three-section

λ / 4

stub notch filter in a single multilayer LTCC chip. Multiple transmission zeros (TZs) are introduced to improve the lower-stopband selectivity, while the three-section coupled-line NF produces a tunable localized rejection band. The LTCC implementation further integrates multilayer capacitors, three-dimensional helical inductors, shielded strip-line coupling stubs, a grounding compensation capacitor, and an isolation wall to balance compactness, impedance matching, and parasitic suppression. The fabricated chip achieves an ultra-wide bandwidth of 2.35 octaves, a notch 20 dB FBW of 8.5%, an insertion loss below 2 dB, a 60 dB roll-off rate of 154.1 dB/GHz within the lower stopband, and a voltage standing wave ratio (VSWR) less than 2. Experimental results validate that the proposed compact chip meets communication requirements and is suitable for 5G base stations, radar systems, and other applications. The chip dimensions are 4.5 mm × 3.2 mm × 2.5 mm. Full article

(This article belongs to the Special Issue Advanced Functional Ceramics for Energy, Dielectric and Electromagnetic Applications)

8 pages, 6180 KB

Open AccessCommunication

Combined Effects of Cooling Rate and Pre-Tempering on Microstructure and Properties of H13 Steel

by Mingwei Ren, Huili Sun, Zheng Zhu, Kewei Gao and Yunbo Chen

Crystals 2026, 16(7), 430; https://doi.org/10.3390/cryst16070430 - 1 Jul 2026

Abstract

The effect of quenching rate combined with pre-tempering treatments on the mechanical properties of H13 steel was systematically investigated in this study. Tensile testing, electron backscatter diffraction (EBSD), scanning electron microscopy (SEM), and X-ray diffraction analysis (XRD) were employed to study the structure–property [...] Read more.

The effect of quenching rate combined with pre-tempering treatments on the mechanical properties of H13 steel was systematically investigated in this study. Tensile testing, electron backscatter diffraction (EBSD), scanning electron microscopy (SEM), and X-ray diffraction analysis (XRD) were employed to study the structure–property relationships associated with different heat treatment conditions. The results showed that the specimen subjected to pre-tempering at 680 °C exhibited optimal strength performance, and fractographic analysis revealed that the specimen exhibited characteristic ductile fracture features. Further analysis revealed that increasing the quenching cooling rate effectively refined the grain size of the matrix, thereby significantly enhancing the strength of the sample. Tensile tests demonstrated optimal comprehensive mechanical performance with a yield strength of ~1050.4 MPa and elongation after fracture of ~17.1% for the oil-quenched specimen subjected to 680 °C pre-tempering treatment. The findings provide valuable experimental evidence and theoretical guidance for optimizing the heat treatment process of H13 steel and improving its failure resistance. Full article

(This article belongs to the Special Issue Microstructure and Properties of Steel Materials)

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26 pages, 50393 KB

Open AccessArticle

Discrete Phase Selection Driven by Evaporation-Induced Off-Stoichiometry in Melt-Grown CsPbBr₃

by Jack E. Elia, Albert These, Christian Schulbert, Amir Pourjafar, Jiyun Zhang, Elshaimaa Darwish, Ievgen Levchuk, Gebhard J. Matt, Andres Osvet, George Sarau, Silke Christiansen, Yuriy Zorenko, Christoph J. Brabec and Miroslaw Batentschuk

Crystals 2026, 16(7), 429; https://doi.org/10.3390/cryst16070429 - 30 Jun 2026

Abstract

We show that halide evaporation during melt growth of

{CsPbBr}_{3}

on polycrystalline FTO under partially open conditions drives discrete phase selection between the line compounds of the CsBr–PbBr₂ system, producing a sharp

{CsPbBr}_{3} / {CsPb}_{2} {Br}_{5}

bilayer instead [...] Read more.

We show that halide evaporation during melt growth of

{CsPbBr}_{3}

on polycrystalline FTO under partially open conditions drives discrete phase selection between the line compounds of the CsBr–PbBr₂ system, producing a sharp

{CsPbBr}_{3} / {CsPb}_{2} {Br}_{5}

bilayer instead of compositional grading. In situ optical imaging shows that solidification begins with nucleation and lateral growth of a planar

{CsPbBr}_{3}

single crystal while the melt layer is still thick enough to average over the FTO relief. As the crystal thickens, the residual melt then becomes inhomogeneous and unstable, producing a buried porous layer of faceted

{CsPb}_{2} {Br}_{5}

grains with a characteristic in-plane spacing of 1–10

μ m

). This morphology is consistent with a faceted Mullins–Sekerka-type instability under a non-conservative evaporative boundary condition. Beneath the single-crystal cap, the first-formed faceted islands are large and become progressively smaller as the advancing front approaches the FTO pyramids, while elevated ambient halide partial pressure suppresses the instability, consistent with diffusion–capillarity selection under decreasing residual melt thickness and steepening local gradients, modified by evaporative flux. Oxygen associated with microvoids or the oxide substrate enables a secondary reaction–diffusion pathway forming Pb–Br–O crystallites without altering the primary length scale. These results identify evaporation as an active control parameter coupling phase equilibria and interfacial stability in volatile halide melts. In the buried, porous bilayer morphology observed here, the secondary phases and porosity reduce the active

{CsPbBr}_{3}

volume and are expected to degrade scintillation through increased trapping, nonradiative recombination, and light scattering. Full article

(This article belongs to the Special Issue Bridging the Embryonic Period for Disruptive Innovation in Crystal Growth)

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18 pages, 4899 KB

Open AccessArticle

High-Temperature Degradation and Microstructural Evolution of 310S Stainless Steel in Carburizing Furnace Service

by Bobby Pranajaya and Chung-Chun Wu

Crystals 2026, 16(7), 428; https://doi.org/10.3390/cryst16070428 - 30 Jun 2026

Abstract

This study investigates the degradation and failure mechanisms of AISI 310S stainless steel conveyor belt wires operating under cyclic conditions up to 900 °C in a continuous carburizing furnace. Microstructural evolution and mechanical responses after service exposure were evaluated using optical microscopy, scanning [...] Read more.

This study investigates the degradation and failure mechanisms of AISI 310S stainless steel conveyor belt wires operating under cyclic conditions up to 900 °C in a continuous carburizing furnace. Microstructural evolution and mechanical responses after service exposure were evaluated using optical microscopy, scanning electron microscopy (SEM) equipped with energy-dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), and Vickers microhardness testing. Results indicate that initial exposure led to σ-phase nucleation and the formation of a protective Cr₂O₃-SiO₂ oxide scale. However, prolonged service led to scale degradation driven by Na-containing residues from pre-cleaning agents, which reacted to form Na₂SiO₃ and NaAlSiO₄ phases. This degradation accelerated the growth of non-protective iron oxides (Fe₂O₃, Fe₃O₄). Simultaneously, the σ-phase decomposed into massive, continuous M₂₃C₆ and M₇C₃ carbide networks along grain boundaries, inducing severe chromium sensitization. Consequently, the matrix embrittled significantly, with Vickers hardness increasing from 150 HV to 290–340 HV. Fracture analysis confirmed that brittle intergranular cracking initiated at these carbide networks, oxide inclusions, and matrix pores. Ultimately, the synergistic effects of oxide scale degradation, extensive carbide precipitation, and grain boundary depletion caused the premature catastrophic failure of the conveyor mesh under cyclic operational stress. Full article

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

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Graphical abstract

41 pages, 14088 KB

Open AccessArticle

Thickness- and Binder-Chemistry-Dependent Structural, Mechanical, and Tribological Performance of HVOF-Sprayed WC-Co and WC-Co-Cr Coatings on High-Speed Steel

by Cevher Kursat Macit, Bünyamin Aksakal, Merve Ayık, Turan Gürgenç and Naim Aslan

Crystals 2026, 16(7), 427; https://doi.org/10.3390/cryst16070427 - 30 Jun 2026

Abstract

High-velocity oxy-fuel (HVOF) spraying was used to deposit WC-Co and WC-Co-Cr coatings on high-speed steel in order to determine how binder chemistry and coating thickness jointly control load support, friction, and dry sliding wear resistance. Nominal 50 and 100 µm coatings were compared [...] Read more.

High-velocity oxy-fuel (HVOF) spraying was used to deposit WC-Co and WC-Co-Cr coatings on high-speed steel in order to determine how binder chemistry and coating thickness jointly control load support, friction, and dry sliding wear resistance. Nominal 50 and 100 µm coatings were compared within the same substrate framework by XRD, FT-IR, SEM/EDX, cross-sectional image analysis, Vickers hardness testing, dry sliding wear testing, and post-wear SEM/EDX. The coatings retained WC as the dominant crystalline phase, while weak overlapping features were associated with binder-rich regions and limited decarburization products. Cross-sectional observations confirmed continuous coating build-up close to the nominal thicknesses and low apparent dark-feature/porosity fractions. All WC-based coatings increased the effective hardness and reduced mass loss relative to uncoated HSS. Among the tested conditions, WC-Co-Cr-100 provided the highest effective hardness and the lowest mass loss after 1000 m sliding, whereas WC-Co-100 produced the lowest mean coefficient of friction. The results show that low friction and high wear resistance are not governed by identical mechanisms: WC-Co favours interfacial shear reduction, while the thicker Cr-containing coating provides superior resistance to material removal through improved carbide retention, binder stability, and coating-scale load support. Full article

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

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Graphical abstract

1 pages, 129 KB

Open AccessRetraction

RETRACTED: Alam et al. Enhanced Electrodes for Supercapacitor Applications Prepared by Hydrothermal-Assisted Nano Sheet-Shaped MgCo₂O₄@ZnS. Crystals 2022, 12, 822

by Mir Waqas Alam, Hassan S. Al Qahtani, Hind Albalawi, Muhammad Aamir, Muhammad Bilal, Tanveer Ahmad Mir, Basma Souayeh and Noushi Zaidi

Crystals 2026, 16(7), 426; https://doi.org/10.3390/cryst16070426 - 30 Jun 2026

Abstract

The journal retracts the article titled “Enhanced Electrodes for Supercapacitor Applications Prepared by Hydrothermal-Assisted Nano Sheet-Shaped MgCo₂O₄@ZnS” [...] Full article

19 pages, 6499 KB

Open AccessArticle

Nonlinear Lattice Dynamics and Discrete Breathers in B2 Crystals: A Comparative Study of CsCl, LiPb, and NiTi

by Dina U. Abdullina, Arseny M. Kazakov, Alexander S. Semenov and Sergey V. Dmitriev

Crystals 2026, 16(7), 425; https://doi.org/10.3390/cryst16070425 - 30 Jun 2026

Abstract

Discrete breathers (DBs) are nonlinear vibrational excitations localized on small groups of atoms in perfect crystal lattices. While theoretically proven, a systematic understanding of DB formation in binary crystals with the B2 structure remains limited. We employ molecular dynamics simulations using the LAMMPS [...] Read more.

Discrete breathers (DBs) are nonlinear vibrational excitations localized on small groups of atoms in perfect crystal lattices. While theoretically proven, a systematic understanding of DB formation in binary crystals with the B2 structure remains limited. We employ molecular dynamics simulations using the LAMMPS package to investigate the nonlinear dynamics of three representative B2 crystals: ionic CsCl, and intermetallic LiPb and NiTi. We calculate the amplitude-frequency dependencies of delocalized nonlinear vibrational modes (DNVMs) and analyze DB existence conditions based on phonon spectrum features and anharmonicity type. Our analysis reveals that a significant atomic mass difference creates a phonon band gap, enabling gap DBs in CsCl and LiPb, whereas NiTi, with similar atomic masses, exhibits no gap. A simplified model assuming identical bond stiffnesses accurately predicts frequency ratios in CsCl and LiPb but fails for NiTi due to strong bond stiffness asymmetry. We demonstrate the successful excitation of long-lived gap DBs in LiPb by initializing atomic displacements based on the G1 DNVM pattern on heavy Pb atoms. These gap DBs remain stable for over 20 ps with negligible energy dissipation. In contrast, DBs with frequencies above the phonon spectrum (excited on light Li atoms) exhibit shorter lifetimes (~2 ps). The study establishes that both atomic mass ratio and interatomic bond stiffness asymmetry are critical parameters governing nonlinear dynamics in B2 crystals. The predicted long-lived gap DBs in LiPb provide a target for future experimental detection via inelastic neutron or X-ray scattering, offering new insights into energy localization and transport in biatomic alloys. Full article

(This article belongs to the Section Inorganic Crystalline Materials)

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20 pages, 1115 KB

Open AccessArticle

Dynamic Recrystallization Behavior and Prediction Model of an Ultra-High-Strength Nickel-Based Corrosion-Resistant Alloy During Hot Deformation

by Dadi Zhou, Gang Meng, Pujie Gou, Wei Jiang and Tengzhong Zhang

Crystals 2026, 16(7), 424; https://doi.org/10.3390/cryst16070424 - 29 Jun 2026

Abstract

A recently developed high-strength nickel-based corrosion-resistant alloy has attracted increasing interest for drilling and production operations in unconventional oil and gas fields. Owing to its high resistance to media containing H₂S, CO₂ and chloride ions, together with its ultra-high strength [...] Read more.

A recently developed high-strength nickel-based corrosion-resistant alloy has attracted increasing interest for drilling and production operations in unconventional oil and gas fields. Owing to its high resistance to media containing H₂S, CO₂ and chloride ions, together with its ultra-high strength and favorable strength–toughness balance, this alloy is suitable for demanding service conditions. During hot working, dynamic recrystallization (DRX) governs deformation softening, grain refinement and the subsequent microstructural state, and thus has a direct influence on final properties. In this work, isothermal compression experiments were conducted on this ultra-high-strength nickel-based corrosion-resistant alloy using a Gleeble thermal simulator at 1000–1150 °C and strain rates of 0.01–10 s⁻¹. Electron backscatter diffraction (EBSD) was used to quantify grain size, grain-boundary misorientation, kernel average misorientation (KAM) and the DRX volume fraction. The results indicate that higher deformation temperature generally accelerates DRX, lowers the KAM value and increases the recrystallized-grain fraction. Under a constant deformation temperature, the DRX volume fraction changes non-monotonically with strain rate, showing an initial increase followed by a decrease. Based on the EBSD-derived DRX fractions, linear and quadratic single-parameter models using the Zener–Hollomon parameter were examined first, but neither provided satisfactory fitting accuracy. A two-variable empirical model was therefore formulated for a fixed true strain of ε = 0.92 by considering deformation temperature and strain rate separately. The predicted values agree well with the experimental data, giving R² = 0.91278 and an average relative error of 8.53%. The proposed model captures the main variation tendency of the DRX volume fraction within the studied processing window and provides a useful basis for microstructure control and hot-working parameter design for ultra-high-strength nickel-based corrosion-resistant alloys. Full article

(This article belongs to the Special Issue Investigation of Microstructural and Properties of Steels and Alloys)

14 pages, 1209 KB

Open AccessArticle

Influence of Supersaturation Level on the Efficacy of Crystallization Inhibitors

by Jaume Dietrich, Bernat Isern, Felix Grases and Antonia Costa-Bauza

Crystals 2026, 16(7), 423; https://doi.org/10.3390/cryst16070423 - 29 Jun 2026

Abstract

This in vitro study examined the influence of supersaturation level on the efficacy of different inhibitors in preventing the crystallization of calcium oxalate, uric acid, and cystine. Kinetic–turbidimetric assays were used to determine the induction time of crystallization (t_i) in the [...] Read more.

This in vitro study examined the influence of supersaturation level on the efficacy of different inhibitors in preventing the crystallization of calcium oxalate, uric acid, and cystine. Kinetic–turbidimetric assays were used to determine the induction time of crystallization (t_i) in the absence and presence of different inhibitors. For calcium oxalate, the inhibitory effects of citrate, hydroxycitrate, tartronate, and phytate decreased significantly as the Ca²⁺ concentration increased from 220 mg/L to 240 mg/L. The polyhydroxycarboxylic compounds (citrate, hydroxycitrate, tartronate) can form complexes with calcium ions, decreasing overall supersaturation. Even though phytate also forms complexes with calcium, its urinary concentration is much lower than that of calcium, so the decrease in supersaturation can be considered negligible. For uric acid, theobromine and two of its metabolites (3-methylxanthine and 7-methylxanthine) inhibited the formation of these crystals. For each compound, the efficacy of inhibition decreased as the supersaturation of uric acid increased. For cystine, the inhibitory effect of N-acetylcysteine was lower at pH 4.5 and 5.0 than at pH 6.0. These studies of the crystallization of calcium oxalate, uric acid, and cystine showed that the efficacy of crystallization inhibitors decreased as the level of supersaturation increased. The results demonstrate that, in patients prone to kidney stone formation, the effectiveness of crystallization inhibitors can be improved by reducing the supersaturation of the specific stone-forming compound. Full article

(This article belongs to the Special Issue Bridging the Embryonic Period for Disruptive Innovation in Crystal Growth)

21 pages, 9190 KB

Open AccessArticle

Improved Langevin Surrogate-Assisted Process-Parameter Optimization for Candidate Recipe Generation in Czochralski Silicon Single Crystal Growth

by Yin Wan, Yanlong Ma, Chi Zhang, Ding Liu and Junchao Ren

Crystals 2026, 16(7), 422; https://doi.org/10.3390/cryst16070422 - 29 Jun 2026

Abstract

To support offline process-parameter screening for Czochralski (CZ) silicon single crystal growth, this paper proposes a surrogate-assisted optimization framework based on an improved Langevin evolutionary algorithm. First, a multi-variable constrained optimization model is established, with the LSA-Transformer-predicted solid–liquid interface deformation used as the [...] Read more.

To support offline process-parameter screening for Czochralski (CZ) silicon single crystal growth, this paper proposes a surrogate-assisted optimization framework based on an improved Langevin evolutionary algorithm. First, a multi-variable constrained optimization model is established, with the LSA-Transformer-predicted solid–liquid interface deformation used as the objective evaluation and with process-smoothness and physical-feasibility constraints considered. Six key process parameters–heater power, pulling rate, argon flow rate, crystal rotation speed, crucible rotation speed, and magnetic field strength–are selected as decision variables. Second, building on the classical Langevin algorithm, an adaptive inertia weight mechanism, a diversity promoter (DP) operator, and a local escaping operator (LEO) are introduced to improve global exploration and local optima escape in complex search spaces. Verification on 23 classical benchmark functions indicates that the ILEE algorithm shows competitive overall performance and achieves better or comparable results on many functions when compared with particle swarm optimization (PSO), grey wolf optimization (GWO), the original Langevin evolutionary algorithm (LEE), and other baseline algorithms. The proposed framework is then used for offline candidate recipe generation during the crystal equal-diameter growth stage (200 mm, 400 mm, 600 mm, 800 mm, and 1000 mm). The optimized candidate parameter combinations yield lower surrogate-predicted interface deformation under the given LSA-Transformer model and physical constraints. Because these values are not independent CFD or experimental measurements, the results should be interpreted as process-parameter guidance for future physical validation. This work provides a feasible surrogate-assisted offline screening framework for CZ silicon single crystal growth. Full article

(This article belongs to the Section Inorganic Crystalline Materials)

24 pages, 5164 KB

Open AccessArticle

Effect of Graphene on Protective Properties of High-Entropy Alloy Coatings for 17-4PH Stainless Steel Industrial Robotic End-Effector Grippers

by Keqing Wang, Kaiming Xu and Hao Tian

Crystals 2026, 16(7), 421; https://doi.org/10.3390/cryst16070421 - 29 Jun 2026

Abstract

Graphene-reinforced CrCoNiFeMo high-entropy alloy composite coatings were fabricated on 17-4PH stainless steel by laser cladding for the surface protection of industrial robotic end-effector grippers. The effects of graphene content on microstructure, hardness, wear behavior and corrosion resistance were investigated. Graphene-derived carbon suppressed Laves [...] Read more.

Graphene-reinforced CrCoNiFeMo high-entropy alloy composite coatings were fabricated on 17-4PH stainless steel by laser cladding for the surface protection of industrial robotic end-effector grippers. The effects of graphene content on microstructure, hardness, wear behavior and corrosion resistance were investigated. Graphene-derived carbon suppressed Laves and σ phases and promoted the in situ formation of M23C6, M7C3 and Co2C carbides, transforming the coating into a carbide-reinforced FCC/BCC composite structure. The average hardness increased from 462 HV0.2 to 676 HV0.2 with increasing graphene content. The 0.4 wt.% graphene coating showed the best wear resistance, with the lowest friction coefficient of 0.42 and minimum wear scar width and depth of 546 μm and 5.72 μm, which was attributed to carbide strengthening and the possible formation of a carbonaceous lubricating tribo-layer. The 0.2 wt.% graphene coating exhibited the best corrosion resistance, with the lowest corrosion current density of 5.81 μA/cm² and the highest impedance response. Excessive graphene caused carbon-rich agglomeration, excessive carbide precipitation and weakened passivation. This work provides a feasible surface strengthening strategy for 17-4PH stainless steel robotic gripper components. Full article

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

24 pages, 28234 KB

Open AccessArticle

Research on V/G Value Prediction Method for Silicon Single-Crystal Growth Based on Multi-Condition Invariant Feature Extraction

by Yin Wan, Chun-Jie Han, Ding Liu, Hao-Nan Lei and Jun-Chao Ren

Crystals 2026, 16(7), 420; https://doi.org/10.3390/cryst16070420 - 29 Jun 2026

Abstract

In the Czochralski process of silicon single-crystal growth, the V/G value at the solid–liquid interface is a key parameter affecting intrinsic crystal defects. However, online V/G detection remains difficult because the temperature gradient G cannot be directly measured, while multi-condition distribution shifts and [...] Read more.

In the Czochralski process of silicon single-crystal growth, the V/G value at the solid–liquid interface is a key parameter affecting intrinsic crystal defects. However, online V/G detection remains difficult because the temperature gradient G cannot be directly measured, while multi-condition distribution shifts and limited labeled data reduce the robustness of data-driven models. To address these issues, this paper proposes DWC-ISBiGNN, an adaptive multi-condition invariant feature extraction method based on the Invariant-Specific Bidirectional Graph Neural Network. The proposed method introduces dynamic sample graph construction with stage-aware global nodes to capture non-stationary process correlations, source-domain credibility weighting to suppress negative transfer, and a semi-supervised training framework combining stage-conditional alignment with teacher–student regression consistency to exploit unlabeled target-domain data. Experiments on industrial data from a 12-inch silicon single-crystal production line show that DWC-ISBiGNN achieves an RMSE of 0.0041, an MAE of 0.00285, and an

R^{2}

of 0.9549. Compared with the original IS-BiGNN, the RMSE is reduced by 32.6%, and

R^{2}

is increased by 5.43 percentage points. The results demonstrate that the proposed method provides an effective soft-sensing approach for V/G prediction under multiple operating conditions. Full article

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

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12 pages, 6773 KB

Open AccessArticle

DFT Study on the Electrocatalytic NO Reduction Performance of Sc Single-Atom Catalysts for Automotive Exhaust NO_x Control

by Changqing Shao, Jingjiang Yang, Xue Lv, Ke Xu and Jiao Liu

Crystals 2026, 16(7), 419; https://doi.org/10.3390/cryst16070419 - 29 Jun 2026

Abstract

Electrocatalytic nitric oxide reduction (NORR) shows great potential for mitigating NO_x emissions from motor vehicles and other internal combustion engine exhausts, enabling the resource utilization of pollutant NO and the synthesis of NH₃ under mild conditions. The overall performance of NORR [...] Read more.

Electrocatalytic nitric oxide reduction (NORR) shows great potential for mitigating NO_x emissions from motor vehicles and other internal combustion engine exhausts, enabling the resource utilization of pollutant NO and the synthesis of NH₃ under mild conditions. The overall performance of NORR largely depends on the development of efficient electrocatalysts. Based on a coordination-engineering strategy, this study constructs a series of Sc-based single-atom catalyst systems coordinated with nonmetal heteroatoms (X = B, C, O, Si, P, S, As, Se, Te), denoted as Sc@XN₃, and systematically investigates their NORR reaction pathways, limiting potentials (U_L, the minimum applied potential required to make all elementary steps downhill in free energy), and selectivity using density functional theory (DFT) calculations. The results indicate that Sc@CN₃, Sc@PN₃, and Sc@SN₃ possess relatively low U_L, with values of −0.17, −0.31, and −0.07 V, respectively, among which Sc@SN₃ is thermodynamically the most favorable. Moreover, Sc@CN₃ and Sc@SN₃ can suppress the hydrogen evolution reaction (HER) and the formation of N₂O/N₂ by-products, thereby affording higher selectivity toward NH₃ formation. Considering the characteristics of NO_x emissions from engine exhaust, these coordination-engineered Sc centers show promising potential for future electrified aftertreatment systems that couple NO_x control with ammonia-based energy utilization in vehicles. This study clarifies at the atomic scale how the coordination environment modulates the electronic structure and catalytic behavior of Sc single-atom centers and provides theoretical guidance for the rational design of high-performance NORR electrocatalysts targeted at automotive exhaust NO_x control. Full article

(This article belongs to the Special Issue Advances in Electrocatalyst Materials)

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33 pages, 5280 KB

Open AccessReview

Research Advances in the Corrosion Behavior and Underlying Mechanisms of Additively Manufactured Titanium Alloys

by Boyan Zhang, Yuman Tang, Baicheng Liu, Teng Liu, Zhisheng Nong and Hongliang Zhang

Crystals 2026, 16(7), 418; https://doi.org/10.3390/cryst16070418 - 26 Jun 2026

Abstract

Titanium alloys are irreplaceable in aerospace, biomedical and marine industries due to their low density, high specific strength and excellent biocompatibility. Conventional manufacturing methods suffer from low material utilization and difficulty in fabricating complex components, while additive manufacturing (AM) realizes near-net-shape forming of [...] Read more.

Titanium alloys are irreplaceable in aerospace, biomedical and marine industries due to their low density, high specific strength and excellent biocompatibility. Conventional manufacturing methods suffer from low material utilization and difficulty in fabricating complex components, while additive manufacturing (AM) realizes near-net-shape forming of customized structures but introduces unique non-equilibrium microstructures and defects, which significantly alter the corrosion behavior and limit the long-term service reliability of additively manufactured (AMed) titanium alloys. This work systematically analyzes the corrosion behavior of titanium alloys fabricated by four mainstream AM processes: LPBF (laser powder bed fusion)/SLM (selective laser melting), EBM (electron beam melting), DED (directed energy deposition) and WAAM (wire arc additive manufacturing). It quantitatively summarizes the key electrochemical parameters and discusses the regulatory effects of matrix composition, post-treatment and service environment on their corrosion behaviors. The universal corrosion mechanisms—namely, passive film breakdown, micro-galvanic corrosion, and defect-induced localized corrosion—as well as process-specific corrosion mechanisms inherent to AMed titanium alloys are systematically elucidated. This study offers theoretical foundations for optimizing corrosion resistance and ensuring the reliable engineering implementation of AMed titanium alloys. Full article

(This article belongs to the Special Issue Recent Progress in Corrosion Protection of Materials)

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12 pages, 1266 KB

Open AccessArticle

Effect of Deposition Method on Grain Boundary Alignment and Off-State Leakage in Polycrystalline Silicon Channel

by Sung Jun Kim, Jun Hyeong Park, Hoi Yoon Jung, In-Sung Park, Taeho Lee, Wangchul Shin, Youngin Goh, Kyunghwan Lee, Daewon Ha, Young Wook Park and Jinho Ahn

Crystals 2026, 16(7), 417; https://doi.org/10.3390/cryst16070417 - 26 Jun 2026

Abstract

Polycrystalline silicon (poly-Si) is a promising channel material for three-dimensional (3D) stacked memory architecture owing to its process compatibility and excellent manufacturability. However, its practical application is hindered by intrinsic limitations, such as reduced carrier mobility and elevated off-state current (I_off), [...] Read more.

Polycrystalline silicon (poly-Si) is a promising channel material for three-dimensional (3D) stacked memory architecture owing to its process compatibility and excellent manufacturability. However, its practical application is hindered by intrinsic limitations, such as reduced carrier mobility and elevated off-state current (I_off), which originate from localized electric fields and trap states at grain boundaries. In this study, the structural characteristics, including the crystallization behavior and grain morphologies, of silicon films deposited by sputtering and low-pressure chemical vapor deposition (LPCVD) were comparatively investigated. Raman spectroscopy and cross-sectional transmission electron microscopy (TEM) results confirmed that LPCVD poly-Si annealed at 800 °C exhibits over 95% crystallinity and a columnar-like grain structure. Based on this structural superiority, transistor-level electrical characterizations were exclusively conducted on LPCVD-based devices. The results show that the I_off of annealed poly-Si depends on the channel width, with normalized I_off values being lower when the channel is narrower than the average grain size. Further, a larger grain size with a columnar structure in poly-Si can maintain acceptable I_off levels in 3D stacked memory devices incorporating narrow channel widths. Full article

(This article belongs to the Section Inorganic Crystalline Materials)

20 pages, 4963 KB

Open AccessArticle

Enhancing Catalytic Oxidation of Volatile Organic Compounds over Acid-Treated La–Sr–Fe–O Perovskites

by Tanya Petrova, Ralitsa Velinova, Daniela Kovacheva, Ivanka Spassova, Katerina Tumbalova, Simona Delibaltova, Hristo Kolev, Daniela Karashanova, Georgi Ivanov, Anton Naydenov and Nikolay Velinov

Crystals 2026, 16(7), 416; https://doi.org/10.3390/cryst16070416 - 26 Jun 2026

Abstract

This study investigates the effect of dilute organic acid treatment on the structural, textural, electronic, and catalytic properties of layered La–Sr–Fe–O Ruddlesden–Popper (R–P) oxides using XRD, TEM, BET, Mössbauer spectroscopy, XPS, H₂-TPR, C₂H₆-TPR and catalytic testing. XRD [...] Read more.

This study investigates the effect of dilute organic acid treatment on the structural, textural, electronic, and catalytic properties of layered La–Sr–Fe–O Ruddlesden–Popper (R–P) oxides using XRD, TEM, BET, Mössbauer spectroscopy, XPS, H₂-TPR, C₂H₆-TPR and catalytic testing. XRD and TEM confirm that the overall layered Ruddlesden–Popper structure is preserved after acid treatment and during catalysis, with minor changes in phase composition, including a decrease in the n = 1 phase and a relative increase in the n = 2 phase. BET analysis shows increased specific surface area and pore volume, forming a more accessible mesoporous structure that is retained under reaction conditions. Mössbauer spectroscopy and XPS reveal an increased Fe⁴⁺ fraction and formation of hydroxylated and carbonated surface species stabilizing active Fe sites. During catalysis, a dynamic Fe³⁺/Fe⁴⁺ redox cycle occurs, along with surface restructuring and involvement of non-lattice oxygen, while the bulk electronic structure remains largely unchanged. Catalytic tests show improved activity, with a 40–60 °C reduction in operating temperature for all acid-treated samples, independent of acid type. This enhancement is mainly attributed to surface-related modifications, including removal of surface Sr-containing species, improved surface accessibility, and enhanced mass transport, while the overall R–P structural remains preserved. Full article

16 pages, 4627 KB

Open AccessArticle

Synthesis and Application of Liquid Crystalline Racemates as Dopants in Antiferroelectric Mixtures

by Magdalena Urbańska, Monika Zając and Olimpia Kaczorowska

Crystals 2026, 16(7), 415; https://doi.org/10.3390/cryst16070415 - 26 Jun 2026

Abstract

Four liquid crystalline racemates, with oligomethylene spacer lengths of three and five and terminal alkyl chain carbon numbers of six and seven (acronyms 3PhPhC6, 5PhPhC6, 3PhPhC7, and 5PhPhC7), were synthesized. Racemates were characterized by their mesomorphic and thermodynamic properties. Identification of the liquid [...] Read more.

Four liquid crystalline racemates, with oligomethylene spacer lengths of three and five and terminal alkyl chain carbon numbers of six and seven (acronyms 3PhPhC6, 5PhPhC6, 3PhPhC7, and 5PhPhC7), were synthesized. Racemates were characterized by their mesomorphic and thermodynamic properties. Identification of the liquid crystalline phases was performed using polarizing optical microscopy (POM), and the temperatures and enthalpies of phase transitions were determined by differential scanning calorimetry (DSC). Two selected racemates were used as dopants in antiferroelectric mixtures with investigated properties, and the effects of their addition on the mesomorphic properties of these mixtures were examined. The helical pitch of the doped mixtures was also measured using UV-Vis spectrophotometry. Racemates containing six carbon atoms in the alkyl chain (C6) exhibit the following phase sequence of Cr-SmC_A-SmC-SmA-Iso, while racemates with seven carbon atoms (C7) exhibit the following phase sequence of Cr-SmC-SmA-Iso. Racemate-doped mixtures exhibit a very wide range of the antiferroelectric phase and slightly higher clearing points than the base mixtures. The helical pitch of the racemate-doped mixtures is longer than that of the base mixtures. Racemates containing seven carbon atoms in the alkyl chain have the potential to be used in the ferroelectric mixtures due to the absence of an anticlinic phase. Full article

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

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13 pages, 886 KB

Open AccessArticle

Multicaloric Coupling Strategies in Ferroic Materials: Sequential vs. Simultaneous Activation for Solid-State Heat Pumping

by Claudia Masselli, Sabrina Gargiulo, Vincenzo Orabona, Lucrezia Verneau, Luca Cirillo and Adriana Greco

Crystals 2026, 16(7), 414; https://doi.org/10.3390/cryst16070414 - 26 Jun 2026

Abstract

Solid-state heat pumps based on caloric effects are emerging as a promising alternative to conventional vapor. compression systems owing to their use of solid refrigerants with zero global warming potential. However, single-effect caloric technologies are intrinsically limited by the temperature-dependent nature of the [...] Read more.

Solid-state heat pumps based on caloric effects are emerging as a promising alternative to conventional vapor. compression systems owing to their use of solid refrigerants with zero global warming potential. However, single-effect caloric technologies are intrinsically limited by the temperature-dependent nature of the caloric response, which typically exhibits a peak adiabatic temperature change within a narrow temperature range. In this context, multicaloric approaches offer a promising pathway to enhance thermal performance by combining multiple external fields. This work focuses on the comparison between simultaneous and sequential (cascade) multicaloric operation, with particular attention to the interaction between field application and the temperature-dependent caloric behavior of the material. A finite element model is developed to investigate a multicaloric solid-state heat pump operating in the air conditioning temperature range. A representative material is considered: Mn_0.6Ni_0.6Fe_0.4Co_0.4Si_0.95Ga_0.05, characterized by distinct magnetocaloric and barocaloric responses occurring at different temperature ranges. The analysis explores different field application strategies, including both simultaneous and sequential configurations. The preliminary results suggest that simultaneous multicaloric operation enables a more effective exploitation of the caloric response by aligning the field activation with temperature regions closer to the corresponding peaks. In this framework, cascade strategies appear to offer additional flexibility in tuning system performance under realistic operating conditions. The proposed approach provides a new perspective for the design of multicaloric heat pumps, highlighting the potential role of thermodynamic matching between field activation and material response. Ongoing work is focused on further quantifying these effects and identifying optimal operating conditions. Full article

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

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