Crystals

22 pages, 5253 KiB

Open AccessArticle

On the Deactivation Analysis of IM-5 Zeolite in Pseudocumene Methylation with Methanol

by Shumin Hao, Yongrui Wang, Enhui Xing and Xuhong Mu

Crystals 2025, 15(7), 598; https://doi.org/10.3390/cryst15070598 (registering DOI) - 25 Jun 2025

In the methylation of pseudocumene with methanol over IM-5 zeolite, the yield of durene can be enhanced. However, poorer stability of the catalytic activity was observed, especially at a higher methanol/pseudocumene ratio. In this paper, conventional characterization methods (XRD, XRF, TGA, SEM, physical [...] Read more.

In the methylation of pseudocumene with methanol over IM-5 zeolite, the yield of durene can be enhanced. However, poorer stability of the catalytic activity was observed, especially at a higher methanol/pseudocumene ratio. In this paper, conventional characterization methods (XRD, XRF, TGA, SEM, physical adsorption, OH-IR, NH₃-TPD, and Py-IR) were used to characterize fresh and deactivated IM-5 zeolite and ZSM-5. FT-IR, XPS, TG-MS, GC-MS, FT-ICR MS, and NMR were employed to characterize deactivated IM-5 zeolite. It was found that the deactivation of IM-5 zeolite was mainly due to the severe coverage of acidic sites and pore channels by carbon deposits. The carbon deposits within the internal surface had a higher abundance, mainly in the form of linear unsaturated chain-like structures with a high degree of unsaturation. The carbon deposits on the external surface were mainly polycyclic aromatic hydrocarbons with alkyl side chains and a high degree of saturation, accompanied by unreacted methanol. Moreover, graphitized carbon existed on both the internal and external surfaces, which made the conventional coke-burning regeneration method unable to restore the activity of the post-reaction IM-5 zeolite. This work had certain reference significance for modulating the acidity and pore channels of zeolite catalysts, thus improving the activity and stability of the catalysts and extending their service life. Full article

(This article belongs to the Section Inorganic Crystalline Materials)

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14 pages, 3510 KiB

Open AccessArticle

Broadband Near-Infrared Reflective Film from Stacked Opposite-Handed Chiral Liquid Crystals with Pitch Gradients

by Hyeon Seong Hwang, Jongsu Lee, Byungsoo Kang, Minhye Kim, Doyo Kim and Se-Um Kim

Crystals 2025, 15(7), 597; https://doi.org/10.3390/cryst15070597 (registering DOI) - 25 Jun 2025

Abstract

Broadband near-infrared (NIR) reflective films are widely used in architecture and the automotive and aerospace industries for energy saving and thermal regulation. For large-area and flexible applications, it is essential to develop cost-effective, solution-processable, and long-term-stable NIR-reflective films. Here, we present a polymer-stabilized [...] Read more.

Broadband near-infrared (NIR) reflective films are widely used in architecture and the automotive and aerospace industries for energy saving and thermal regulation. For large-area and flexible applications, it is essential to develop cost-effective, solution-processable, and long-term-stable NIR-reflective films. Here, we present a polymer-stabilized chiral liquid crystal (CLC) film that achieves broadband NIR reflection by stacking opposite-handed CLC layers with pitch gradients. We experimentally established optimal formulations of materials for both right-handed and left-handed CLCs. The resulting film exhibits high-degree broadband reflection (~95%) in the 1000–1800 nm wavelength range, while maintaining visible transmittance (~80%) in the 450–850 nm range. The concept proposed here will be widely applicable for scalable and practical NIR-filtering applications in smart glasses, sensors, and optoelectronic devices. Full article

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

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18 pages, 1324 KiB

Open AccessArticle

Enhancing Fatigue Life Prediction Accuracy: A Parametric Study of Stress Ratios and Hole Position Using SMART Crack Growth Technology

by Yahya Ali Fageehi and Abdulnaser M. Alshoaibi

Crystals 2025, 15(7), 596; https://doi.org/10.3390/cryst15070596 - 24 Jun 2025

Abstract

This study presents a unique and comprehensive application of ANSYS Mechanical R19.2’s SMART crack growth feature, leveraging its capabilities to conduct an unprecedented parametric investigation into fatigue crack propagation behavior under a wide range of positive and negative stress ratios, and to provide [...] Read more.

This study presents a unique and comprehensive application of ANSYS Mechanical R19.2’s SMART crack growth feature, leveraging its capabilities to conduct an unprecedented parametric investigation into fatigue crack propagation behavior under a wide range of positive and negative stress ratios, and to provide detailed insights into the influence of hole positioning on crack trajectory. By uniquely employing an unstructured mesh method that significantly reduces computational overhead and automates mesh updates, this research overcomes traditional fracture simulation limitations. The investigation breaks new ground by comprehensively examining an unprecedented range of both positive (R = 0.1 to 0.5) and negative (R = −0.1 to −0.5) stress ratios, revealing previously unexplored relationships in fracture mechanics. Through rigorous and extensive numerical simulations on two distinct specimen configurations, i.e., a notched plate with a strategically positioned hole under fatigue loading and a cracked rectangular plate with dual holes under static loading, this work establishes groundbreaking correlations between stress parameters and fatigue behavior. The research reveals a novel inverse relationship between the equivalent stress intensity factor and stress ratio, alongside a previously uncharacterized inverse correlation between stress ratio and von Mises stress. Notably, a direct, accelerating relationship between stress ratio and fatigue life is demonstrated, where higher R-values non-linearly increase fatigue resistance by mitigating stress concentration, challenging conventional linear approximations. This investigation makes a substantial contribution to fracture mechanics by elucidating the fundamental role of hole positioning in controlling crack propagation paths. The research uniquely demonstrates that depending on precise hole location, cracks will either deviate toward the hole or maintain their original trajectory, a phenomenon attributed to the asymmetric stress distribution at the crack tip induced by the hole’s presence. These novel findings, validated against existing literature, represent a significant advancement in predictive modeling for fatigue life assessment, offering critical new insights for engineering design and maintenance strategies in high-stakes industries. Full article

(This article belongs to the Special Issue Fatigue and Fracture of Crystalline Metal Structures)

22 pages, 4820 KiB

Open AccessArticle

Microstructure and Properties of Corrosion-Resistant Steel Produced by CASTRIP

by Kai Lei, Long Chen, Hengchang Lu, Xintong Lian, Qingxiao Feng, Hualong Li and Han Dong

Crystals 2025, 15(7), 595; https://doi.org/10.3390/cryst15070595 - 24 Jun 2025

Abstract

The CASTRIP process is an innovative method for producing flat rolled low-carbon and low-alloy steel at very thin thicknesses. By casting steel close to its final dimensions, enormous savings in time and energy can be realized. In this paper, an ultra-high-strength low-alloy corrosion-resistant [...] Read more.

The CASTRIP process is an innovative method for producing flat rolled low-carbon and low-alloy steel at very thin thicknesses. By casting steel close to its final dimensions, enormous savings in time and energy can be realized. In this paper, an ultra-high-strength low-alloy corrosion-resistant steel was produced through the CASTRIP process. Microstructure and properties were investigated by means of optical microscopy (OM), scanning electron microscopy (SEM), transmission electron microscopy (TEM), laser confocal microscopy (LSCM), electron backscattered diffraction (EBSD), and tensile testing. The results show that the microstructure is mainly composed of polygonal ferrite, bainite ferrite, and acicular ferrite. The bainite ferrite forms parallel lath bundles nucleating at austenite grain boundaries, propagating perpendicularly into the parent grains. The acicular ferrite exhibits a cross-interlocked morphology preferentially nucleating at oxide/sulfide inclusions. Microstructural characterization confirms that the phase transformation of acicular ferrite and bainite ferrite introduces high-density dislocations, identified as the primary strengthening mechanism. Under the CASTRIP process, corrosion-resistant elements such as Cu, P, Sb, and Nb are completely dissolved in the matrix without grain boundary segregation, thereby contributing to solid solution strengthening. Full article

(This article belongs to the Special Issue Phase Transformation and Microstructure Evolution of Alloys)

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14 pages, 3788 KiB

Open AccessArticle

Identification of Streptococcus pneumoniae Sortase A Inhibitors and the Interactive Mechanism

by Guizhen Wang, Jiahui Lu, Jingyao Wen, Yifan Duan, Hanbing Zhou, Xinli Peng and Zhandong Li

Crystals 2025, 15(7), 594; https://doi.org/10.3390/cryst15070594 - 24 Jun 2025

Abstract

Streptococcus pneumoniae (S. pneumoniae) Sortase A (SrtA) anchors virulence proteins to the surface of the cell wall by recognizing and cleaving the LPXTG motif. These toxins help bacteria adhere to and colonize host cells, promote biofilm formation, and trigger host inflammatory [...] Read more.

Streptococcus pneumoniae (S. pneumoniae) Sortase A (SrtA) anchors virulence proteins to the surface of the cell wall by recognizing and cleaving the LPXTG motif. These toxins help bacteria adhere to and colonize host cells, promote biofilm formation, and trigger host inflammatory responses. Therefore, SrtA is an ideal target for the development of new preparations for S. pneumoniae. In this study, we found that phloretin (pht) and phlorizin (phz) exhibited excellent affinities for SrtA based on virtual screening experiments. We analyzed the interactive mechanism between pht, phz, and alnusone (aln, a reported S. pneumoniae SrtA inhibitor) and SrtA based on molecular dynamics simulation experiments. The results showed that these inhibitors bound to the active pocket of SrtA, and the root mean square deviation (RMSD) and distance analyses showed that these compounds and SrtA maintained stable configuration and binding during the assay. The binding free energy analysis showed that both electrostatic forces (ele), van der Waals forces (vdw), and hydrogen bonds (Hbonds) promoted the binding between pht, phz, and SrtA; however, for the binding of aln and SrtA, the vdw force was much stronger than ele, and Hbonds were not found. The binding free energy decomposition showed that HIS141, ILE143, and PHE119 contributed more energy to promote pht and SrtA binding; ARG215, ASP188, and LEU210 contributed more energy to promote phz and SrtA binding; and HIS141, ASP209, and ARG215 contributed more energy to promote aln and SrtA binding. Finally, the transpeptidase activity of SrtA decreased significantly when treated with different concentrations of pht, phz, or aln, which inhibited S. pneumoniae biofilm formation and adhesion to A549 cells without affecting normal bacterial growth. These results suggest that pht, phtz, and aln are potential materials for the development of novel inhibitors against S. pneumoniae infection. Full article

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13 pages, 1650 KiB

Open AccessArticle

Mechanical and Tribological Properties of SPS-Sintered Y-TZP: The Effect of Sintering Temperature

by Dávid Medveď, Jana Andrejovská and Viktor Puchý

Crystals 2025, 15(7), 593; https://doi.org/10.3390/cryst15070593 - 23 Jun 2025

Abstract

This work systematically investigates the influence of two spark plasma sintering (SPS) temperatures (1400 °C and 1600 °C) on the mechanical and tribological properties of two yttria-stabilized zirconia ceramics: 3 mol.% Y₂O₃ (3Y-TZP) and 1.5 mol.% Y₂O₃ [...] Read more.

This work systematically investigates the influence of two spark plasma sintering (SPS) temperatures (1400 °C and 1600 °C) on the mechanical and tribological properties of two yttria-stabilized zirconia ceramics: 3 mol.% Y₂O₃ (3Y-TZP) and 1.5 mol.% Y₂O₃ (1.5Y-TZP). The ceramics’ microhardness, nanohardness, Young’s modulus, fracture toughness, and tribological performance were evaluated. The results show that 3Y-TZP maintains high hardness (Vickers hardness HV ~1300; nanohardness ~17.1 GPa) and stable fracture toughness (~4.2 MPa·m½), nearly independently of sintering temperature. In contrast, 1.5Y-TZP exhibits a critical trade-off: sintering at 1400 °C yields exceptional fracture toughness (~6.2 MPa·m½), but increasing the temperature to 1600 °C causes a sharp drop to ~4.5 MPa·m½. Tribologically, the highest wear resistance under a 5 N load was observed for the 3Y-TZP sample sintered at 1600 °C. These findings suggest that for low-yttria compositions, higher SPS temperatures can trigger detrimental microstructural changes that degrade toughness. The results provide crucial insights for tailoring SPS parameters and Y-TZP compositions for specific high-performance applications, balancing the competing requirements of hardness and fracture toughness. Full article

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13 pages, 3126 KiB

Open AccessArticle

Development of Young’s Modulus of Illite/Smectite—CaCO₃ Composites After Various Firing Temperatures

by Štefan Csáki, Tibor Kovács, Martin Keppert, Vojtěch Pommer, František Lukáč, Michal Knapek, Peter Minárik and Anton Trník

Crystals 2025, 15(7), 592; https://doi.org/10.3390/cryst15070592 - 23 Jun 2025

Abstract

Illitic clays are one of the most important materials used in the ceramic industry. Carbonates support the densification and the sintering of ceramics. Five mixtures of illitic clay with calcite were prepared aiming for the crystallization of anorthite ceramics. The stoichiometric ratio of [...] Read more.

Illitic clays are one of the most important materials used in the ceramic industry. Carbonates support the densification and the sintering of ceramics. Five mixtures of illitic clay with calcite were prepared aiming for the crystallization of anorthite ceramics. The stoichiometric ratio of anorthite crystallization was determined at 21.6 wt.% of calcite content. To reveal the effect of calcite on the crystallization processes, two more mixtures were prepared below the stoichiometric composition (17.6 wt.% and 19.6 wt.%) and two more mixtures above the ideal composition (23.6 wt.% and 25.6 wt.%). X-ray diffraction revealed that gehlenite and Ca-feldspar were formed, which are the intermediate phases in anorthite crystallization. However, due to the low purity of illitic clay and the low firing temperature, no anorthite formation was observed. The influence of calcite content on Young’s modulus was negligible. However, a clear effect on the open porosity was revealed. Full article

(This article belongs to the Special Issue Ceramics: Processes, Microstructures, and Properties)

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13 pages, 4115 KiB

Open AccessArticle

Modeling of Cr²⁺-Doped Saturable-Absorber Q-Switched Tm:CaF₂ Lasers

by Mofan Yang, Ziyi Wu and Jinhe Yuan

Crystals 2025, 15(7), 591; https://doi.org/10.3390/cryst15070591 - 23 Jun 2025

Abstract

We present a model of a Cr²⁺-doped saturable absorber (SA), which is employed in passively Q-switched (PQS) Tm:CaF₂ lasers. The overall round-trip loss, the time evolution of the intracavity photon density, and the effective population inversion density can all be [...] Read more.

We present a model of a Cr²⁺-doped saturable absorber (SA), which is employed in passively Q-switched (PQS) Tm:CaF₂ lasers. The overall round-trip loss, the time evolution of the intracavity photon density, and the effective population inversion density can all be obtained through numerical solutions. Under the mode-matching condition, this model can be used to easily determine the PQS laser’s main output parameters, including the average output power, repetition frequency, peak power, pulse energy, and pulse width. This concept is also applicable to a range of thulium-doped solid-state lasers (SSLs) operating on the transition from the ³F₄ level to the ³H₆ level, which are Q-switched by a Cr²⁺-doped SA. This model is helpful for the design and optimization of this kind of laser. Full article

(This article belongs to the Special Issue Research Progress of Laser Crystals)

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20 pages, 3209 KiB

Open AccessArticle

Experimental Evaluation of GAGG:Ce Crystalline Scintillator Properties Under X-Ray Radiation

by Anastasios Dimitrakopoulos, Christos Michail, Ioannis Valais, George Fountos, Ioannis Kandarakis and Nektarios Kalyvas

Crystals 2025, 15(7), 590; https://doi.org/10.3390/cryst15070590 - 23 Jun 2025

Abstract

The scope of this study was to evaluate the response of Ce-doped gadolinium aluminum gallium garnet (GAGG:Ce) crystalline scintillator under medical X-ray irradiation for medical imaging applications. A 10 × 10 × 10 mm³ crystal was irradiated at X-ray tube voltages ranging [...] Read more.

The scope of this study was to evaluate the response of Ce-doped gadolinium aluminum gallium garnet (GAGG:Ce) crystalline scintillator under medical X-ray irradiation for medical imaging applications. A 10 × 10 × 10 mm³ crystal was irradiated at X-ray tube voltages ranging from 50 kVp to 150 kVp. The crystal’s compatibility with several commercially available optical photon detectors was evaluated using the spectral matching factor (SMF) along with the absolute efficiency (AE) and the effective efficiency (EE). In addition, the energy-absorption efficiency (EAE), the quantum-detection efficiency (QDE) as well as the zero-frequency detective quantum detection efficiency DQE(0) were determined. The crystal demonstrated satisfactory AE values as high as 26.3 E.U. (where 1 E.U. = 1 μW∙m⁻²/(mR∙s⁻¹)) at 150 kVp, similar, or in some cases, even superior to other cerium-doped scintillator materials. It also exhibits adequate DQE(0) performance ranging from 0.99 to 0.95 across all the examined X-ray tube voltages. Moreover, it showed high spectral compatibility with commonly used photoreceptors in modern day such as complementary metal–oxide–semiconductors (CMOS) and charge-coupled-devices (CCD) with SMF values of 0.95 for CCD with broadband anti-reflection coating and 0.99 for hybrid CMOS blue. The aforementioned properties of this scintillator material were indicative of its superior efficiency in the examined medical energy range, compared to other commonly used scintillators. Full article

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

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12 pages, 1611 KiB

Open AccessArticle

Influence of Deposition Time on Properties of Se-Doped CdTe Thin Films for Solar Cells

by Ibrahim M. Beker, Francis B. Dejene, Lehlohonolo F. Koao, Jacobus J. Terblans and Habtamu F. Etefa

Crystals 2025, 15(7), 589; https://doi.org/10.3390/cryst15070589 - 22 Jun 2025

Abstract

Se-doped CdTe thin films were grown employing a simple two-electrode electrochemical deposition method using glass/tin-doped indium oxide (glass/ITO). Cadmium acetate dihydrate [Cd (CH₃CO₂)₂. 2H₂O], selenium dioxide (SeO₂), and tellurium dioxide (TeO₂) [...] Read more.

Se-doped CdTe thin films were grown employing a simple two-electrode electrochemical deposition method using glass/tin-doped indium oxide (glass/ITO). Cadmium acetate dihydrate [Cd (CH₃CO₂)₂. 2H₂O], selenium dioxide (SeO₂), and tellurium dioxide (TeO₂) were used as precursors. Instruments including X-ray diffraction for structural investigation, UV-Vis spectrophotometry for optical properties, and scanning probe microscopy for morphological properties were employed to investigate the physico-chemical characteristics of the resulting Se-doped CdTe thin-film. The films are polycrystalline with a cubic phase, according to X-ray diffraction (XRD) data. More ions are deposited on the substrate, which makes the material more crystalline and intensifies the characteristic peaks that are seen. It is observed from the acquired optical characterization that the film’s bandgap is greatly influenced by the deposition time. The bandgap dropped from 1.92 to 1.62 as the deposition period increased from 25 to 45 min, making the film more transparent and absorbing less light at shorter deposition durations. Images from scanning electron microscopy (SEM) show that the surface morphology is homogenous with closely packed grains and that the grain forms become less noticeable as the deposition time increases. This work is novel in that it investigates the influence of the deposition time on the structural, optical, and morphological properties of Se-doped CdTe thin films deposited using a cost-effective, simplified two-electrode electrochemical method—a fabrication route that remains largely unexplored for this material system. Full article

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

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21 pages, 1108 KiB

Open AccessArticle

Three-Phase-Lag Effect on Rayleigh Waves in a Generalized Thermoelastic Diffusion Medium with Modified Couple Stress

by Emad K. Jaradat, Sayed M. Abo-Dahab, Rajneesh Kumar and Eslam S. Elidy

Crystals 2025, 15(7), 588; https://doi.org/10.3390/cryst15070588 - 22 Jun 2025

Abstract

This study examines the behavior of Rayleigh waves propagating through a homogeneous, isotropic material, analyzed using a three-phase-lag thermoelastic diffusion framework enhanced by modified couple stress theory. The mathematical model integrates coupled thermoelastic and diffusive effects, incorporating phase-lags associated with (1) temperature gradients, [...] Read more.

This study examines the behavior of Rayleigh waves propagating through a homogeneous, isotropic material, analyzed using a three-phase-lag thermoelastic diffusion framework enhanced by modified couple stress theory. The mathematical model integrates coupled thermoelastic and diffusive effects, incorporating phase-lags associated with (1) temperature gradients, (2) heat flux, and (3) thermal displacement gradients. By solving the derived governing equations analytically subject to stress-free, thermally insulated, and impermeable boundary conditions, we obtain the characteristic secular equation for Rayleigh wave propagation. Numerical simulations conducted on a copper medium evaluate how the secular equation’s determinant, wave velocity, and attenuation coefficient vary with angular frequency. The analysis focuses particularly on the influence of phase-lag parameters, including thermal and diffusion gradients and relaxation times. Results demonstrated that increasing the displacement gradient phase-lag elevated the secular determinant but reduced wave velocity and attenuation, while temperature gradient phase-lags exhibited the opposite trend. The study highlights the sensitivity of Rayleigh wave propagation to thermo-diffusive coupling and microstructural effects, offering insights applicable to seismic wave analysis, geophysical exploration, and material processing. Comparisons with prior theories underscore the model’s advancement in capturing size-dependent and memory-dependent phenomena. Full article

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15 pages, 2784 KiB

Open AccessArticle

The Effect of Spark Current Tuning on the Formation of Cu Nanoparticles Synthesized by Spark Ablation in Nitrogen Atmosphere

by Maria Assunta Signore, Antonio Della Torre, Antonio Serra, Daniela Manno, Rosaria Rinaldi, Marco Mazzeo, Luca Nunzio Francioso and Luciano Velardi

Crystals 2025, 15(7), 587; https://doi.org/10.3390/cryst15070587 - 21 Jun 2025

Abstract

The demand for a “green” approach to the synthesis of nanomaterials is becoming increasingly pressing. In response to this need, we present, for the first time, the use of spark ablation as an environmentally friendly deposition technique to obtain nanoparticles of copper nitride, [...] Read more.

The demand for a “green” approach to the synthesis of nanomaterials is becoming increasingly pressing. In response to this need, we present, for the first time, the use of spark ablation as an environmentally friendly deposition technique to obtain nanoparticles of copper nitride, a material that is gaining increasing attention in the field of photovoltaic advanced technologies. This method involves the ablation of pure copper electrodes in nitrogen atmosphere while a spark current is tuned. The overall result is the co-presence of nitride and oxide nanoparticle agglomerates with different sizes according to the spark current, as confirmed by X-ray diffraction, Raman spectroscopy, X-ray photoelectron spectroscopy and energy-dispersive spectroscopy techniques. Scanning probe microscopy and scanning electron microscopy show an increase in the number and size of nanoparticle agglomerates with an increasing current, while the nanoparticle size is always about sub-10 nm. The findings of this work promote spark ablation as a simple, versatile, cost-effective, environmentally friendly deposition method to obtain nitride-based nanoparticles. Furthermore, it is compatible with many types of materials and substrates, increasing the possible combinations of metals/semiconductors and carrier gas types to obtain completely innovative materials with unique compositions and properties. Full article

(This article belongs to the Section Inorganic Crystalline Materials)

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15 pages, 5614 KiB

Open AccessArticle

Influence of Post-Heat Treatment on the Tensile Strength and Microstructure of Metal Inert Gas Dissimilar Welded Joints

by Van-Thuc Nguyen, Thanh Tan Nguyen, Van Huong Hoang, Tran Ngoc Thien, Duong Thi Kim Yen, Tri Ho Minh, Le Minh Tuan, Anh Tu Nguyen, Hoang Trong Nghia, Pham Quan Anh, Phan Quoc Bao and Van Thanh Tien Nguyen

Crystals 2025, 15(7), 586; https://doi.org/10.3390/cryst15070586 - 20 Jun 2025

Abstract

Taguchi and post-heat treatment methods have been used in this study to optimize the metal inert gas (MIG) welding joints between SUS304 austenite stainless steel and plain carbon SS400 steel using AWS ER 308L filler wire. The dissimilar welding joints’ microstructure and tensile [...] Read more.

Taguchi and post-heat treatment methods have been used in this study to optimize the metal inert gas (MIG) welding joints between SUS304 austenite stainless steel and plain carbon SS400 steel using AWS ER 308L filler wire. The dissimilar welding joints’ microstructure and tensile strength have been examined. The findings show that the fast cooling of the weld joint and the ferrite-forming element of the filler wire cause the dendrites’ δ-ferrite phase to emerge on both the weld bead and the heat-affected zone (HAZ) of the SUS304 side. The stickout parameter has the largest impact on the ultimate tensile strength (UTS), next to the welding speed, welding voltage, and welding current, due to the strong impact of the heat distribution. The optimal welding parameters are a welding current of 105 A, a welding voltage of 14.5 V, a stickout of 12 mm, and a welding speed of 420 mm/min, producing the UTS value of 445.3 MPa, which is close to the predicted value of 469.2 ± 53.6 MPa. Post-heat treatment with an annealing temperature that is lower than 700 °C could improve the optimized weld joints’ strength by up to 5%. The findings may provide a more realistic understanding of the dissimilar welding technology. Full article

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14 pages, 3487 KiB

Open AccessArticle

Additive Manufacturing of Ceramic-Reinforced Inconel 718: Microstructure and Mechanical Characterization

by Yang Qi, Bo Hu, Lei Wang, Yanwei Ma, Mei Yang, Yihang Ma and Pengfei Li

Crystals 2025, 15(7), 585; https://doi.org/10.3390/cryst15070585 - 20 Jun 2025

Abstract

This study investigates the microstructure and mechanical properties of Inconel 718, a nickel-based alloy, reinforced with ceramic phases via additive manufacturing. Two reinforcement strategies were explored: in situ formation of ceramic phases through titanium powder addition, and direct incorporation of Cr₂O [...] Read more.

This study investigates the microstructure and mechanical properties of Inconel 718, a nickel-based alloy, reinforced with ceramic phases via additive manufacturing. Two reinforcement strategies were explored: in situ formation of ceramic phases through titanium powder addition, and direct incorporation of Cr₂O₃ and TiO₂ ceramic particles. Both approaches significantly modified the alloy’s microstructure and elemental distribution. The in situ formation method produced leaf-like Ti-rich precipitates (up to 70.13 wt%), while direct ceramic addition suppressed the preferred orientation of the Laves phase and promoted the formation of NbC precipitates. Microhardness increased by 19.4% with titanium addition, compared to a modest 1.3% improvement with direct ceramic addition. Tensile testing revealed that titanium powder enhanced ultimate tensile strength but reduced elongation, whereas direct ceramic addition led to decreases in both strength and ductility. Wear resistance evaluation showed that direct ceramic addition yielded superior performance, evidenced by the lowest friction coefficient (0.514) and smallest wear volume (16,290,782 μm³). These findings demonstrate the effectiveness of ceramic reinforcement strategies in optimizing the mechanical and tribological behavior of additively manufactured Inconel 718, and offer valuable guidance for the development of wear-resistant components such as those used in hydraulic support systems. Full article

(This article belongs to the Section Polycrystalline Ceramics)

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18 pages, 12852 KiB

Open AccessArticle

Effect of Al-5Ti-2B on the Microstructure and Mechanical Properties of Recycled Al-7Si-0.3Mg-1Fe Alloy

by Weihe Shi, Lin Chen, Bing He, Biwang Lu and Jianbing Yang

Crystals 2025, 15(7), 584; https://doi.org/10.3390/cryst15070584 - 20 Jun 2025

Abstract

This study systematically investigates the influence of grain refinement on the microstructural evolution and mechanical properties of recycled Al-7Si-0.3Mg-1Fe alloy through the addition of varying concentrations (0–1.25 wt.%) of Al-5Ti-2B master alloy. The synergistic effects of Al-5Ti-2B on the α-Al phase, eutectic Si, [...] Read more.

This study systematically investigates the influence of grain refinement on the microstructural evolution and mechanical properties of recycled Al-7Si-0.3Mg-1Fe alloy through the addition of varying concentrations (0–1.25 wt.%) of Al-5Ti-2B master alloy. The synergistic effects of Al-5Ti-2B on the α-Al phase, eutectic Si, and Fe-rich intermetallics were characterized using metallographic analysis, XRD, SEM-BSE imaging, and EDS. In the unrefined alloy, the microstructure consisted of an α-Al solid solution with coarse plate-like eutectic Si, while Fe primarily formed needle-like β-Al₅FeSi phases that either surrounded or penetrated the eutectic Si. Increasing the Al-5Ti-2B addition refined both the α-Al dendrites and eutectic Si, while the β-Al₅FeSi phase transitioned from coarse to fine needles. The optimal refinement was achieved at a 1% Al-5Ti-2B addition, yielding a tensile strength of 149.4 MPa and elongation of 4.3%. However, excessive addition (1.25%) led to eutectic Si aggregation and β-Al₅FeSi coarsening, resulting in mechanical property deterioration and brittle fracture behavior. These findings provide insights into optimizing grain refinement for enhancing the performance of recycled Al-Si-Mg-Fe alloys. Full article

(This article belongs to the Special Issue Design, Development and Processing of Aluminium Alloys and Their Composite Materials)

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22 pages, 4680 KiB

Open AccessReview

Surface Electric Properties and Their Role in the Bioactivity of Implant Materials: A Comprehensive Review

by Valentina Vadimovna Chebodaeva

Crystals 2025, 15(6), 583; https://doi.org/10.3390/cryst15060583 - 19 Jun 2025

Abstract

The surface electric charge of biomaterials plays a pivotal role in determining their bioactivity and biocompatibility, especially in orthopedic and dental applications. This review analyzes recent progress (2015–2024) in understanding how electric properties, particularly surface charge and zeta potential, modulate cellular adhesion, proliferation, [...] Read more.

The surface electric charge of biomaterials plays a pivotal role in determining their bioactivity and biocompatibility, especially in orthopedic and dental applications. This review analyzes recent progress (2015–2024) in understanding how electric properties, particularly surface charge and zeta potential, modulate cellular adhesion, proliferation, and differentiation. Negatively charged surfaces (−20 to −30 mV) were consistently associated with enhanced osteoblast activity and calcium mineralization, while positively charged surfaces often induced pro-inflammatory responses. We explore theoretical models of the electric double layer (EDL), methods for quantifying surface charge, and strategies for modifying surface potential to enhance biological outcomes. A comparative analysis of materials—hydroxyapatite coatings, PCL scaffolds, titanium surfaces, and piezoceramics—is provided. Finally, we highlight knowledge gaps in mechanistic understanding and emphasize the need for standardized protocols in evaluating the electric properties of biomaterials. Full article

(This article belongs to the Section Inorganic Crystalline Materials)

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12 pages, 3031 KiB

Open AccessArticle

Doping Effects on Magnetic and Electronic Transport Properties in BaZn₂As₂

by Guoqiang Zhao, Gangxu Gu, Shuai Yang, Yi Peng, Xiang Li, Kenji M. Kojima, Chaojing Lin, Xiancheng Wang, Timothy Ziman, Yasutomo J. Uemura, Bo Gu, Gang Su, Sadamichi Maekawa, Yongqing Li and Changqing Jin

Crystals 2025, 15(6), 582; https://doi.org/10.3390/cryst15060582 - 19 Jun 2025

Abstract

Novel diluted magnetic semiconductors derived from BaZn₂As₂ are of considerable importance owing to their elevated Curie temperature of 260 K, the diversity of magnetic states they exhibit, and their prospective applications in multilayer heterojunctions. However, the transition from the intrinsic [...] Read more.

Novel diluted magnetic semiconductors derived from BaZn₂As₂ are of considerable importance owing to their elevated Curie temperature of 260 K, the diversity of magnetic states they exhibit, and their prospective applications in multilayer heterojunctions. However, the transition from the intrinsic semiconductor BaZn₂As₂ (BZA) to its doped compounds has not been extensively explored, especially in relation to the significant intermediate compound Ba(Zn,Mn)₂As₂ (BZMA). This study aims to address this gap by performing susceptibility and magnetization measurements, in addition to electronic transport analyses, on these compounds in their single crystal form. Key findings include the following: (1) carriers can significantly modulate the magnetism, transitioning from a non-magnetic BZA to a weak magnetic BZMA, and subsequently to a hard ferromagnet (Ba,K)(Zn,Mn)₂As₂ with potassium (K) doping to BZMA; (2) two distinct sets of metal-insulator transitions were identified, which can be elucidated by the involvement of carriers and the emergence of various magnetic states, respectively; and (3) BZMA exhibits colossal negative magnetoresistance, and by lanthanum (La) doping, a potential n-type (Ba,La)(Zn,Mn)₂As₂ single crystal was synthesized, demonstrating promising prospects for p-n junction applications. This study enhances our understanding of the magnetic interactions and evolutions among these compounds, particularly in the low-doping regime, thereby providing a comprehensive physical framework that complements previous findings related to the high-doping region. Full article

(This article belongs to the Section Inorganic Crystalline Materials)

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12 pages, 3008 KiB

Open AccessArticle

Structural, Thermophysical, and Radiation Shielding Properties of Lead–Bismuth Eutectic (LBE) Synthesized by Induction Melting

by Radu Cristian Gavrea, Emanoil Surducan, Răzvan Hirian, Mioara Zagrai and Vasile Rednic

Crystals 2025, 15(6), 581; https://doi.org/10.3390/cryst15060581 - 19 Jun 2025

Abstract

Lead–bismuth eutectic alloy (LBE, Pb_44.5Bi_55.5) has emerged as a promising candidate for use in advanced nuclear and solar energy systems due to its favorable thermophysical characteristics and radiation shielding capabilities. The aim of this research is to assess the [...] Read more.

Lead–bismuth eutectic alloy (LBE, Pb_44.5Bi_55.5) has emerged as a promising candidate for use in advanced nuclear and solar energy systems due to its favorable thermophysical characteristics and radiation shielding capabilities. The aim of this research is to assess the applicability of the induction melting technique to synthesize LBE. This paper presents a comprehensive evaluation of the structural, thermophysical, and radiation shielding properties of the obtained LBE sample. Various techniques were employed to investigate the solid-to-liquid eutectic transformation, phase composition, morphology, and homogeneity of the obtained material. Experimental and theoretical determinations on density, void, molar volume, thermal conductivity, heat capacity, thermal diffusivity, and electrical conductivity were performed. Radiation shielding performance over photon energies ranging from 0.015 to 15 MeV was simulated using the Phy-X/PSD program. The results revealed the eutectic structure comprising Pb₇Bi₃ and Bi phases with near-ideal stoichiometry and a melting point of 127.6 °C. The alloy demonstrated a small void that corresponds to a high degree of sample compaction, high specific heat capacity, moderate thermal conductivity, low thermal diffusivity, and effective radiation shielding. These findings confirm that LBE obtained by the induction melting technique possesses the necessary structural stability and functional properties for integration into nuclear reactor and solar thermal technologies. Full article

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

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16 pages, 3258 KiB

Open AccessArticle

Breaking the Efficiency–Quality Tradeoff via Temperature–Velocity Co-Optimization: Multiscale Calculations and Experimental Study of Epitaxial Growth of Iridium on MgO(100)

by Yang Wang, Junhao Chen, Shilin Yang and Jiaqi Zhu

Crystals 2025, 15(6), 580; https://doi.org/10.3390/cryst15060580 - 19 Jun 2025

Abstract

The precise control of thermal–kinetic parameters governs epitaxial perfection in functional oxide heterostructures. Herein, using Iridium/MgO(100) as a model system, the traditional “low-speed/high-temperature” paradigm is revolutionized through the combination of ab initio calculations, multiscale simulations, and subsequent deposition experiments. First-principles modeling reveals the [...] Read more.

The precise control of thermal–kinetic parameters governs epitaxial perfection in functional oxide heterostructures. Herein, using Iridium/MgO(100) as a model system, the traditional “low-speed/high-temperature” paradigm is revolutionized through the combination of ab initio calculations, multiscale simulations, and subsequent deposition experiments. First-principles modeling reveals the mechanisms of Volmer–Weber (VW, island growth mode) nucleation at low coverage and Stranski–Krastanov (SK, layer-plus-island growth) transitions driven by interface metallization, stress release, and energy reduction, which facilitates coherent monolayer formation by lowering the energy barrier by ~34%. Molecular dynamics simulations demonstrate that the strategic co-optimization of substrate temperature (T_sub) and deposition rate (V_dep) induces an abrupt cliff-like drop in mosaic spread. Experimental validations confirm that this T-V synergy achieves unprecedented interfacial coherence, whereby AFM roughness reaches 0.34 nm (RMS) and the XRC-FWHM of 0.13° approaches single-crystal benchmarks. Notably, our novel “accelerated heteroepitaxy” protocol reduces growth time without compromising quality, addressing the efficiency–quality paradox in industrial-scale diamond substrate fabrication. These findings establish universal thermal–kinetic design principles applicable to refractory metal/oxide heterostructures for next-generation quantum sensors and high-power electronic devices. Full article

(This article belongs to the Special Issue Crystallization Process and Simulation Calculation, Third Edition)

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