Crystals

21 pages, 4054 KiB

Open AccessArticle

Benzo[c]cinnolinium Trifluoromethanesulfonate Architectures Induced by Organotin(IV) Complexes

by Hélène Cattey and Laurent Plasseraud

Crystals 2025, 15(7), 655; https://doi.org/10.3390/cryst15070655 - 17 Jul 2025

Four novel crystalline architectures based on benzo[c]cinnolininium trifluoromethanesulonate salts, [C₁₂H₉N₂]⁺[CF₃SO₃]⁻, have been isolated as single-crystals, and their structures have been determined by X-ray diffraction analysis. The formation [...] Read more.

Four novel crystalline architectures based on benzo[c]cinnolininium trifluoromethanesulonate salts, [C₁₂H₉N₂]⁺[CF₃SO₃]⁻, have been isolated as single-crystals, and their structures have been determined by X-ray diffraction analysis. The formation of the new salts results from reactions involving the dimeric hydroxo di-n-butylstannane trifluoromethanesulfonato complex [n-Bu₂Sn(OH)(H₂O)(CF₃SO₃)]₂ (1) and benzo[c]cinnoline (C₁₂H₈N₂, BCC). Organic salts I, II, III, and IV were crystallized through slow evaporation at room temperature from a mixture of toluene/dichloromethane. The cystallographic structures of I, II, and IV exhibit the presence of monoprotonated benzo[c]cinnolinium cations in interactions with a free benzo[c]cinnoline molecule through N–H···N hydrogen bonding, while for salt III, the monoprotonated cation directly interacts with the CF₃SO₃⁻ anion via an N–H···O interaction. For all four salts, aromatic π-π interactions involving rings of various components (free benzo[c]cinnoline molecule, benzo[c]cinnolinium cation, toluene molecule), combined with weak C–H···O and C–H···F interactions implying the trifluoromethanesulfonate anion, promote the solid-state self-assembly of supramolecular stacks. In parallel to the formation of benzo[c]cinnolinium based-salts, organotin(IV) 1 was converted into a distannoxane compound, ²_∞{[n-Bu₂(μ-OH)SnOSn(μ-η²-O₃SCF₃)n-Bu₂]₂[n-Bu₂(η¹-O₃SCF₃)SnOSn(μ-OH)n-Bu₂]₂} (3), which was also isolated as a single crystal and whose crystallographic structure was previously established by us. Full article

(This article belongs to the Section Macromolecular Crystals)

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20 pages, 967 KiB

Open AccessArticle

A Comprehensive Investigation of the Two-Phonon Characteristics of Heat Conduction in Superlattices

by Pranay Chakraborty, Milad Nasiri, Haoran Cui, Theodore Maranets and Yan Wang

Crystals 2025, 15(7), 654; https://doi.org/10.3390/cryst15070654 - 17 Jul 2025

Abstract

The Anderson localization of phonons in disordered superlattices has been proposed as a route to suppress thermal conductivity beyond the limits imposed by conventional scattering mechanisms. A commonly used signature of phonon localization is the emergence of the nonmonotonic dependence of thermal conductivity [...] Read more.

The Anderson localization of phonons in disordered superlattices has been proposed as a route to suppress thermal conductivity beyond the limits imposed by conventional scattering mechanisms. A commonly used signature of phonon localization is the emergence of the nonmonotonic dependence of thermal conductivity

κ

on system length L, i.e., a

κ

-L maximum. However, such behavior has rarely been observed. In this work, we conduct extensive non-equilibrium molecular dynamics (NEMD) simulations, using the LAMMPS package, on both periodic superlattices (SLs) and aperiodic random multilayers (RMLs) constructed from Si/Ge and Lennard-Jones materials. By systematically varying acoustic contrast, interatomic bond strength, and average layer thickness, we examine the interplay between coherent and incoherent phonon transport in these systems. Our two-phonon model decomposition reveals that coherent phonons alone consistently exhibit a strong nonmonotonic

κ

-L. This localization signature is often masked by the diffusive, monotonically increasing contribution from incoherent phonons. We further extract the ballistic-limit mean free paths for both phonon types, and demonstrate that incoherent transport often dominates, thereby concealing localization effects. Our findings highlight the importance of decoupling coherent and incoherent phonon contributions in both simulations and experiments. This work provides new insights and design principles for achieving phonon Anderson localization in superlattice structures. Full article

(This article belongs to the Section Crystal Engineering)

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17 pages, 410 KiB

Open AccessArticle

Theoretical Analysis of the Factors Determining the Crystal Size Distribution (CSD) During Crystallization in Solution: Rates of Crystal Growth

by Christo N. Nanev

Crystals 2025, 15(7), 653; https://doi.org/10.3390/cryst15070653 - 17 Jul 2025

Abstract

Crystalline products with a narrow and uniform distribution of crystals by size (CSD), characterized by a desired average size, are necessary in many practices. Therefore, extensive, but mostly experimental, research is devoted to the problem of obtaining such CSDs. Alternatively, this manuscript presents [...] Read more.

Crystalline products with a narrow and uniform distribution of crystals by size (CSD), characterized by a desired average size, are necessary in many practices. Therefore, extensive, but mostly experimental, research is devoted to the problem of obtaining such CSDs. Alternatively, this manuscript presents a theoretical approach for calculating CSD resulting from crystallization in unstirred solutions. First, classical equations for the rates of diffusion-controlled and kinetically controlled growth of crystals are used to discuss the size-dependent growth of the nucleated crystals and the initial CSD (which arises from the non-simultaneous nucleation of crystals). Then, applying the law of conservation of matter, it is proved that the CSD continues to expand during the growth stage. Furthermore, it is substantiated that, due to their uneven spatial distribution, crystals of the same size can grow at different rates. This depends on whether the crystals are outside the diffusion fields of other crystals or are clustered together in “nests”. Moreover, by calculating the growth rates of crystals in “nests”, an explanation is given for the observation that closely spaced crystals are smaller in size than the separately growing crystals. Finally, the CSD established during the Ostwald ripening is discussed quantitatively, step-by-step. Full article

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15 pages, 5721 KiB

Open AccessArticle

Temperature-Dependent Martensitic Transformation in Cold-Rolled AISI 304 Stainless Steel

by Jaka Burja, Jernej Lindič, Barbara Šetina Batič and Aleš Nagode

Crystals 2025, 15(7), 652; https://doi.org/10.3390/cryst15070652 - 16 Jul 2025

Abstract

This study investigates the influence of plastic deformation and temperature on the formation of mechanically induced martensite and the associated changes in hardness in AISI 304 austenitic stainless steel. Cold rolling was performed at three temperatures (20 °C, 0 °C, and −196 °C) [...] Read more.

This study investigates the influence of plastic deformation and temperature on the formation of mechanically induced martensite and the associated changes in hardness in AISI 304 austenitic stainless steel. Cold rolling was performed at three temperatures (20 °C, 0 °C, and −196 °C) and various degrees of deformation (10–70%). Microstructural changes, including the formation of ε and α′ martensite, were characterized using X-ray diffraction (XRD) and electron backscatter diffraction (EBSD). The results confirm that martensitic transformation proceeds via the γ → ε → α′ sequence, with transformation rates and martensite fractions increasing at lower temperatures and higher strains. The stacking fault energy of 25.9 mJ/m² favors this transformation pathway. Transformation rates of α′ martensite fractions significantly increased at lower temperatures and higher strains, 91.8% α′ martensite was observed at just 30% deformation at −196 °C. Hardness measurements revealed a strong correlation with martensite content: strain hardening dominated at lower deformations, while martensite formation became the primary hardening mechanism at higher deformations, especially at cryogenic temperatures. The highest hardness (551 HV) was observed in samples deformed to 70% at −196 °C. The findings provide insights into optimizing the mechanical properties of AISI 304 stainless steel through controlled deformation and temperature conditions. Full article

(This article belongs to the Special Issue Crystallization of High Performance Metallic Materials (2nd Edition))

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16 pages, 6052 KiB

Open AccessArticle

Crystal Form Investigation and Morphology Control of Salbutamol Sulfate via Spherulitic Growth

by Xinyue Qiu, Hongcheng Li, Yanni Du, Xuan Chen, Shichao Du, Yan Wang and Fumin Xue

Crystals 2025, 15(7), 651; https://doi.org/10.3390/cryst15070651 - 16 Jul 2025

Abstract

Salbutamol sulfate is a selective β2-receptor agonist used to treat asthma and chronic obstructive pulmonary disease. The crystals of salbutamol sulfate usually appear as needles with a relatively large aspect ratio, showing poor powder properties. In this study, spherical particles of salbutamol sulfate [...] Read more.

Salbutamol sulfate is a selective β2-receptor agonist used to treat asthma and chronic obstructive pulmonary disease. The crystals of salbutamol sulfate usually appear as needles with a relatively large aspect ratio, showing poor powder properties. In this study, spherical particles of salbutamol sulfate were obtained via antisolvent crystallization. Four different antisolvents, including ethanol, n-propanol, n-butanol, and sec-butanol, were selected, and their effects on crystal form and morphology were compared. Notably, a new solvate of salbutamol sulfate with sec-butanol has been obtained. The novel crystal form was characterized by single-crystal X-ray diffraction, revealing a 1:1 stoichiometric ratio between solvent and salbutamol sulfate in the crystal lattice. In addition, the effects of crystallization temperature, solute concentration, ratio of antisolvent to solvent, feeding rate, and stirring rate on the morphology of spherical particles were investigated in different antisolvents. We have found that crystals grown from the n-butanol–water system at optimal conditions (25 °C, antisolvent/solvent ratio of 9:1, and drug concentration of 0.2 g·mL⁻¹) could be developed into compact and uniform spherulites. The morphological evolution process was also monitored, and the results indicated a spherulitic growth pattern, in which sheaves of plate-like crystals gradually branched into a fully developed spherulite. This work paves a feasible way to develop new crystal forms and prepare spherical particles of pharmaceuticals. Full article

(This article belongs to the Special Issue Crystallization and Purification)

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19 pages, 2559 KiB

Open AccessArticle

Development of Patient-Specific Lattice Structured Femoral Stems Based on Finite Element Analysis and Machine Learning

by Rashwan Alkentar, Sándor Manó, Dávid Huri and Tamás Mankovits

Crystals 2025, 15(7), 650; https://doi.org/10.3390/cryst15070650 - 15 Jul 2025

Viewed by 115

Abstract

Hip implant optimization is increasingly receiving attention due to the development of manufacturing technology and artificial intelligence interaction in the current research. This study investigates the development of hip implant stem design with the application of lattice structures, and the utilization of the [...] Read more.

Hip implant optimization is increasingly receiving attention due to the development of manufacturing technology and artificial intelligence interaction in the current research. This study investigates the development of hip implant stem design with the application of lattice structures, and the utilization of the MATLAB regression learner app in finding the best predictive regression model to calculate the mechanical behavior of the implant’s stem based on some of the design parameters. Many cases of latticed hip implants (using 3D lattice infill type) were designed in the ANSYS software, and then 3D printed to undergo simulations and lab experiments. A surrogate model of the implant was used in the finite element analysis (FEA) instead of the geometrically latticed model to save computation time. The model was then generalized and used to calculate the mechanical behavior of new variables of hip implant stem and a database was generated for surgeon so they can choose the lattice parameters for desirable mechanical behavior. This study shows that neural networks algorithms showed the highest accuracy with predicting the mechanical behavior reaching a percentage above 90%. Patients’ weight and shell thickness were proven to be the most affecting factors on the implant’s mechanical behavior. Full article

(This article belongs to the Special Issue Celebrating the 10th Anniversary of International Crystallography)

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31 pages, 40778 KiB

Open AccessArticle

Crystal Organisation of Muscle Attachment Sites of Bivalved Marine Organisms: A Juxtaposition Between Brachiopod and Bivalved Mollusc Shells

by Sebastian Hoerl, Erika Griesshaber, Daniel Weller, Shahrouz Amini, Verena Häussermann, Maria A. Bitner, Klaus Achterhold, Franz Pfeiffer and Wolfgang W. Schmahl

Crystals 2025, 15(7), 649; https://doi.org/10.3390/cryst15070649 - 15 Jul 2025

Viewed by 51

Abstract

The movement of valves of bivalved invertebrates is enabled through the action of muscles and the interplay between the muscles and the hinge ligament. The muscles that move the valves attach to their internal surface. To promote the structural integrity at the mechanically [...] Read more.

The movement of valves of bivalved invertebrates is enabled through the action of muscles and the interplay between the muscles and the hinge ligament. The muscles that move the valves attach to their internal surface. To promote the structural integrity at the mechanically mismatched interfaces, a specific crystal microstructure and texture are present at the muscle attachment sites. These are different from the crystal microstructure and texture of the rest of the valves. We present here for modern two- and three-layered brachiopod shells (Magellania venosa, Liothyrella neozelanica and Gryphus vitreus) the mode of crystal organisation at sites of adductor and diductor muscle attachments (i) relative to the microstructure and texture that forms the other sections of the valves and (ii) relative to crystal organisation of muscle attachment sites of bivalved invertebrates of other phyla, namely, species of the class Bivalvia. We discuss similarities/differences in Ca-carbonate phase, microstructure and texture between rhynchonellate brachiopods and bivalves, and discuss whether the Ca-carbonate crystal organisation of muscle attachment sites is convergent for bivalved marine organisms. We show significant differences in muscle attachment site architecture and highlight the different structural solutions developed by nature for shells of marine organisms that serve the same purpose. Full article

(This article belongs to the Section Mineralogical Crystallography and Biomineralization)

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17 pages, 2783 KiB

Open AccessArticle

Hydrostatic-Pressure Modulation of Band Structure and Elastic Anisotropy in Wurtzite BN, AlN, GaN and InN: A First-Principles DFT Study

by Ilyass Ez-zejjari, Haddou El Ghazi, Walid Belaid, Redouane En-nadir, Hassan Abboudi and Ahmed Sali

Crystals 2025, 15(7), 648; https://doi.org/10.3390/cryst15070648 - 15 Jul 2025

Viewed by 128

Abstract

III-Nitride semiconductors (BN, AlN, GaN, and InN) exhibit exceptional electronic and mechanical properties that render them indispensable for high-performance optoelectronic, power, and high-frequency device applications. This study implements first-principles Density Functional Theory (DFT) calculations to elucidate the influence of hydrostatic pressure on the [...] Read more.

III-Nitride semiconductors (BN, AlN, GaN, and InN) exhibit exceptional electronic and mechanical properties that render them indispensable for high-performance optoelectronic, power, and high-frequency device applications. This study implements first-principles Density Functional Theory (DFT) calculations to elucidate the influence of hydrostatic pressure on the electronic, elastic, and mechanical properties of these materials in the wurtzite crystallographic configuration. Our computational analysis demonstrates that the bandgap energy exhibits a positive pressure coefficient for GaN, AlN, and InN, while BN manifests a negative pressure coefficient consistent with its indirect-bandgap characteristics. The elastic constants and derived mechanical properties reveal material-specific responses to applied pressure, with BN maintaining superior stiffness across the pressure range investigated, while InN exhibits the highest ductility among the studied compounds. GaN and AlN demonstrate intermediate mechanical robustness, positioning them as optimal candidates for pressure-sensitive applications. Furthermore, the observed nonlinear trends in elastic moduli under pressure reveal anisotropic mechanical responses during compression, a phenomenon critical for the rational design of strain-engineered devices. The computational results provide quantitative insights into the pressure-dependent behavior of III-N semiconductors, facilitating their strategic implementation and optimization for high-performance applications in extreme environmental conditions, including high-power electronics, deep-space exploration systems, and high-pressure optoelectronic devices. Full article

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

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16 pages, 3287 KiB

Open AccessArticle

Interference Effect Between a Parabolic Notch and a Screw Dislocation in Piezoelectric Quasicrystals

by Yuanyuan Gao, Guanting Liu, Chengyan Wang and Junjie Fan

Crystals 2025, 15(7), 647; https://doi.org/10.3390/cryst15070647 - 15 Jul 2025

Viewed by 49

Abstract

This study investigates the coupling mechanism between a parabolic notch and dislocations in one-dimensional (1D) hexagonal piezoelectric quasicrystals (PQCs) based on the theory of complex variable functions. By applying perturbation techniques and the Cauchy integral, analytical solutions for complex potentials are derived, yielding [...] Read more.

This study investigates the coupling mechanism between a parabolic notch and dislocations in one-dimensional (1D) hexagonal piezoelectric quasicrystals (PQCs) based on the theory of complex variable functions. By applying perturbation techniques and the Cauchy integral, analytical solutions for complex potentials are derived, yielding closed-form expressions for the phonon–phason stress field and electric displacement field. Numerical examples reveal several key findings: significant stress concentration occurs at the notch root, accompanied by suppression of electric displacement; interference patterns between dislocation cores and notch-induced stress singularities are identified; the J-integral quantifies distance-dependent forces, size effects, and angular force distributions reflecting notch symmetry; and the energy-driven dislocation slip toward free surfaces leads to the formation of dislocation-free zones. These results provide new insights into electromechanical fracture mechanisms in quasicrystals. Full article

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18 pages, 5060 KiB

Open AccessArticle

Research on Fatigue Strength Evaluation Method of Welded Joints in Steel Box Girders with Open Longitudinal Ribs

by Bo Shen, Ming Liu, Yan Wang and Hanqing Zhuge

Crystals 2025, 15(7), 646; https://doi.org/10.3390/cryst15070646 - 15 Jul 2025

Viewed by 101

Abstract

Based on the engineering background of a new type of segmental-assembled steel temporary beam buttress, the fatigue strength evaluation method of the steel box girders with open longitudinal ribs was taken as the research objective. The fatigue stress calculation analysis and the full-scale [...] Read more.

Based on the engineering background of a new type of segmental-assembled steel temporary beam buttress, the fatigue strength evaluation method of the steel box girders with open longitudinal ribs was taken as the research objective. The fatigue stress calculation analysis and the full-scale fatigue loading test for the steel box girder local component were carried out. The accuracy of the finite-element model was verified by comparing it with the test results, and the rationality of the fatigue strength evaluation methods for welded joints was deeply explored. The results indicate that the maximum nominal stress occurs at the weld toe between the transverse diaphragm and the top plate at the edge of the loading area, which is the fatigue-vulnerable location for the steel box girder local components. The initial static-load stresses at each measuring point were in good agreement with the finite-element calculation results. However, the static-load stress at the measuring point in the fatigue-vulnerable position shows a certain decrease with the increase in the number of cyclic loads, while the stress at other measuring points remains basically unchanged. According to the finite-element model, the fatigue strengths obtained by the nominal stress method and the hot-spot stress method are 72.1 MPa and 93.8 MPa, respectively. It is reasonable to use the nominal stress S-N curve with a fatigue life of 2 million cycles at 70 MPa and the hot-spot stress S-N curve with a fatigue life of 2 million cycles at 90 MPa (FAT90) to evaluate the fatigue of the welded joints in steel box girders with open longitudinal ribs. According to the equivalent structural stress method, the fatigue strength corresponding to 2 million cycles is 94.1 MPa, which is slightly lower than the result corresponding to the main S-N curve but within the range of the standard deviation curve. The research results of this article can provide important guidance for the anti-fatigue design of welded joints in steel box girders with open longitudinal ribs. Full article

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

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33 pages, 19356 KiB

Open AccessArticle

Hoffman–Lauritzen Analysis of Crystallization of Hydrolyzed Poly(Butylene Succinate-Co-Adipate)

by Anna Svarcova and Petr Svoboda

Crystals 2025, 15(7), 645; https://doi.org/10.3390/cryst15070645 - 14 Jul 2025

Viewed by 170

Abstract

This study systematically investigates the impact of hydrolytic degradation on the crystallization kinetics and morphology of poly(butylene succinate-co-adipate) (PBSA). Gel Permeation Chromatography (GPC) confirmed extensive chain scission, significantly reducing the polymer’s weight-average molecular weight (M_w from ~103,000 to ~16,000 g/mol) and broadening [...] Read more.

This study systematically investigates the impact of hydrolytic degradation on the crystallization kinetics and morphology of poly(butylene succinate-co-adipate) (PBSA). Gel Permeation Chromatography (GPC) confirmed extensive chain scission, significantly reducing the polymer’s weight-average molecular weight (M_w from ~103,000 to ~16,000 g/mol) and broadening its polydispersity index (PDI from ~2 to 7 after 64 days). Differential scanning calorimetry (DSC) analysis revealed that hydrolytic degradation dramatically accelerated crystallization rates, reducing crystallization time roughly 10-fold (e.g., from ~3000 s to ~300 s), and crystallinity increased from 34% to 63%. Multiple melting peaks suggested the presence of lamellae with varying thicknesses, consistent with the Gibbs–Thomson equation. Isothermal crystallization kinetics were evaluated using the Avrami equation (with n ≈ 3), reciprocal half-time of crystallization, and a novel inflection point slope method, all confirming accelerated crystallization; for instance, the slope increased from 0.00517 to 0.05203. Polarized optical microscopy (POM) revealed evolving spherulite morphologies, including hexagonal and flower-like dendritic spherulites with diamond-shape ends, while wide-angle X-ray diffraction (WAXD) showed a crystallization range shift to higher temperatures (e.g., from 72–61 °C to 82–71 °C) and a 14% increase in crystallite diameter, aligning with increased melting point and lamellar thickness and overall increased crystallinity. Full article

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17 pages, 4663 KiB

Open AccessArticle

Low-Cycle Fatigue Behavior of Nuclear-Grade Austenitic Stainless Steel Fabricated by Additive Manufacturing

by Jianhui Shi, Huiqiang Liu, Zhengping Liu, Runzhong Wang, Huanchun Wu, Haitao Dong, Xinming Meng and Min Yu

Crystals 2025, 15(7), 644; https://doi.org/10.3390/cryst15070644 - 13 Jul 2025

Viewed by 199

Abstract

The application of additive manufacturing technology in the field of nuclear power is becoming increasingly promising. The low-cycle fatigue behavior of Z2CN19-10 controlled-nitrogen-content stainless steel (SS) was investigated by fatigue equipment, scanning electron microscopy (SEM), electron backscatter diffraction (EBSD), and transmission electron microscopy [...] Read more.

The application of additive manufacturing technology in the field of nuclear power is becoming increasingly promising. The low-cycle fatigue behavior of Z2CN19-10 controlled-nitrogen-content stainless steel (SS) was investigated by fatigue equipment, scanning electron microscopy (SEM), electron backscatter diffraction (EBSD), and transmission electron microscopy (TEM), including additive manufactured (AM) and forged materials. The results showed that the microstructure of the AM material exhibited anisotropy for the X, Y, and Z directions. The tensile and impact properties of the X, Y, and Z directions in AM material were similar. The fatigue life (N_f) of X- and Y-direction specimens was better than that of Z-direction specimens. The tensile, impact, and fatigue properties of all AM materials were lower than those of the forged specimens. The Z direction specimens of AM material showed the best plastic strain by the highest transition fatigue life (N_T) during the fatigue strain amplitude at 0.3% to 0.6%. The forged specimens showed the best fatigue properties under the plastic strain amplitude control mode. Fatigue fracture surfaces of AM and forged materials exhibited multi- and single-fatigue crack initiation sites, respectively. This could be attributed to the presence of incompletely melted particles and manufacturing defects inside the AM specimens. The dislocation morphology of AM and forged fatigue specimens was observed to study the low-cycle fatigue behaviors in depth. Full article

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13 pages, 3867 KiB

Open AccessArticle

Effect of Hot Isostatic Pressing on Mechanical Properties of K417G Nickel-Based Superalloy

by Fan Wang, Yuandong Wei, Yi Zhou, Wenqi Guo, Zexu Yang, Jinghui Jia, Shusuo Li and Haigen Zhao

Crystals 2025, 15(7), 643; https://doi.org/10.3390/cryst15070643 - 11 Jul 2025

Viewed by 131

Abstract

The cast nickel-based superalloy K417G exhibits excellent high-temperature strength, but non-equilibrium solidification during casting can cause defects such as irreparable interdendritic microporosity, which significantly degrades its fatigue and creep properties. This study uses hot isostatic pressing (HIP) to eliminate internal flaws such as [...] Read more.

The cast nickel-based superalloy K417G exhibits excellent high-temperature strength, but non-equilibrium solidification during casting can cause defects such as irreparable interdendritic microporosity, which significantly degrades its fatigue and creep properties. This study uses hot isostatic pressing (HIP) to eliminate internal flaws such as porosity in the K417G alloy, aiming to improve its mechanical properties. We investigated the microstructure and mechanical properties of K417G under two thermal conditions: solution heat treatment (SHT) and hot isostatic pressing (HIP). The results indicate that HIP significantly reduces microporosity. Compared to SHT, HIP improves the mechanical performance of K417G. The creep fracture mechanism shifts from intergranular brittle fracture (SHT) to ductile fracture (HIP). Consequently, HIP increases the alloy′s creep life approximately threefold and raises its fatigue limit by about 20 MPa. This improvement is attributed to pore density reduction, which decreases stress concentration zones and homogenizes the microstructure, thereby impeding fatigue crack nucleation and extending the crack incubation period. Full article

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

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5 pages, 175 KiB

Open AccessEditorial

Characterization and Modelling of the Deformation and Failure of Engineering Metallic Materials

by Hui Wang, Lihong Su, Ebad Bagherpour and Qiang Xing

Crystals 2025, 15(7), 642; https://doi.org/10.3390/cryst15070642 - 11 Jul 2025

Viewed by 151

Abstract

Metallic materials are at the heart of modern industry and infrastructure, valued for their outstanding strength, ductility, and other excellent mechanical properties [...] Full article

(This article belongs to the Special Issue Characterization and Modelling of the Deformation and Failure of Engineering Metallic Materials)

14 pages, 1843 KiB

Open AccessArticle

Investigations into Microstructure and Mechanical Properties of As-Cast Mg-Zn-xNd Alloys for Biomedical Applications

by Faruk Mert

Crystals 2025, 15(7), 641; https://doi.org/10.3390/cryst15070641 - 11 Jul 2025

Viewed by 117

Abstract

Magnesium-based biomaterials have emerged as highly promising candidates in the realm of biomedical engineering due to certain unique properties. However, their widespread application has been limited by a number of challenges, such as insufficient mechanical strength and rapid degradation rates. This study sought [...] Read more.

Magnesium-based biomaterials have emerged as highly promising candidates in the realm of biomedical engineering due to certain unique properties. However, their widespread application has been limited by a number of challenges, such as insufficient mechanical strength and rapid degradation rates. This study sought to advance the development of high-performance magnesium alloys by examining the microstructural evolution and associated strengthening mechanisms of Mg-Zn alloys modified with varying Nd contents. Comprehensive characterization techniques—including optical microscopy, XRD, and SEM/EDS—were employed to explain the influence of Nd additions on the microstructures. Mechanical performance was assessed through hardness testing, the RFDA method for elastic modulus, and tensile testing. The microstructural analysis of the as-cast Mg-Zn-Nd alloys revealed a complex phase composition comprising dendritic α-Mg, Mg₄₁Nd₅, and a Mg₃Nd binary phase enriched with rare earth elements. Notably, increasing the Nd content from 0.5% to 5% by weight resulted in a significant enhancement of hardness, reaching 59 HV compared to 42 HV in the base alloy. The tensile strength increased significantly from 62.9 MPa in the Mg-2.5Zn-0.5Nd alloy to 186.8 MPa in the Mg-2.5Zn-5Nd alloy. The elastic modulus values across all investigated alloys remained consistently comparable, which is expected as the elastic modulus is primarily determined by atomic bonding and is not significantly affected by alloying additions. These findings underscore the potential of Nd-alloyed Mg-Zn systems as viable, mechanically robust alternatives for next-generation biodegradable orthopedic implants. Full article

(This article belongs to the Special Issue Corrosion and Mechanical Performance of Magnesium Alloys)

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17 pages, 4195 KiB

Open AccessArticle

Rapid Synthesis of Highly Crystalline ZnO Nanostructures: Comparative Evaluation of Two Alternative Routes

by Emely V. Ruiz-Duarte, Juan P. Molina-Jiménez, Duber A. Avila, Cesar O. Torres and Sindi D. Horta-Piñeres

Crystals 2025, 15(7), 640; https://doi.org/10.3390/cryst15070640 - 11 Jul 2025

Viewed by 145

Abstract

Zinc oxide (ZnO) is a wide bandgap semiconductor of great scientific and technological interest due to its high exciton binding energy and outstanding structural and optical properties, making it an ideal material for applications in optoelectronics, sensors, and photocatalysis. This study presents the [...] Read more.

Zinc oxide (ZnO) is a wide bandgap semiconductor of great scientific and technological interest due to its high exciton binding energy and outstanding structural and optical properties, making it an ideal material for applications in optoelectronics, sensors, and photocatalysis. This study presents the rapid synthesis of highly crystalline ZnO nanostructures using two alternative routes: (1) direct thermal decomposition of zinc acetate and (2) a physical-green route assisted by Mangifera indica extract. Both routes were subjected to identical calcination thermal conditions (400 °C for 2 h), allowing for an objective comparison of their effects on structural, vibrational, morphological, and optical characteristics. X-ray diffraction analyses confirmed the formation of a pure hexagonal wurtzite phase in both samples, highlighting a higher crystallinity index (91.6%) and a larger crystallite size (35 nm) in the sample synthesized using the physical-green route. Raman and FTIR spectra supported these findings, revealing greater structural order. Electron microscopy showed significant morphological differences, and UV-Vis analysis showed a red shift in the absorption peak, associated with a decrease in the optical bandgap (from 3.34 eV to 2.97 eV). These results demonstrate that the physical-green route promotes significant improvements in the structural and functional properties of ZnO, without requiring changes in processing temperature or the use of additional chemicals. Full article

(This article belongs to the Special Issue Synthesis and Characterization of Oxide Nanoparticles)

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20 pages, 6807 KiB

Open AccessArticle

Enhancing Electrochemical Kinetics and Stability of Biodegradable Mg-Y-Zn Alloys with LPSO Phases via Strategic Micro-Alloying with Ca, Sr, Mn, and Zr

by Lisha Wang, Huiping Wang, Chenchen Zhang, Wei Sun, Yue Wang, Lijuan Wang and Xiaoyan Kang

Crystals 2025, 15(7), 639; https://doi.org/10.3390/cryst15070639 - 11 Jul 2025

Viewed by 195

Abstract

This study systematically investigated the effects of biologically relevant microalloying elements—calcium (Ca), strontium (Sr), manganese (Mn), and zirconium (Zr)—on the electrochemical behavior of Mg-Y-Zn alloys containing long-period stacking ordered (LPSO) phases. The alloys were prepared by casting and characterized using X-ray diffraction (XRD), [...] Read more.

This study systematically investigated the effects of biologically relevant microalloying elements—calcium (Ca), strontium (Sr), manganese (Mn), and zirconium (Zr)—on the electrochemical behavior of Mg-Y-Zn alloys containing long-period stacking ordered (LPSO) phases. The alloys were prepared by casting and characterized using X-ray diffraction (XRD), optical microscopy (OM), and scanning electron microscopy with energy-dispersive spectroscopy (SEM/EDS). Electrochemical properties were assessed through potentiodynamic polarization in Hank’s solution, and corrosion rates were determined by hydrogen evolution and weight loss methods. Microalloying significantly enhanced the corrosion resistance of the base Mg-Y-Zn alloy, with corrosion rates decreasing from 2.67 mm/year (unalloyed) to 1.65 mm/year (Ca), 1.36 mm/year (Sr), 1.18 mm/year (Zr), and 1.02 mm/year (Mn). Ca and Sr additions introduced Mg₂Ca and Mg₁₇Sr₂, while Mn and Zr refined the existing LPSO structure without new phases. Sr refined the LPSO phase and formed a uniformly distributed Mg₁₇Sr₂ network, promoting uniform corrosion and suppressing deep localized attacks. Ca-induced Mg₂Ca acted as a temporary sacrificial phase, with corrosion eventually propagating along LPSO interfaces. The Mn-containing alloy exhibited the lowest corrosion rate; this is attributed to the suppression of both anodic and cathodic reaction kinetics and the formation of a stable protective surface film. Zr improved general corrosion resistance but increased susceptibility to localized attacks due to dislocation-rich zones. These findings elucidate the corrosion mechanisms in LPSO-containing Mg alloys and offer an effective strategy to enhance the electrochemical stability of biodegradable Mg-based implants. Full article

(This article belongs to the Special Issue Advances in High-Performance Alloys)

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17 pages, 5651 KiB

Open AccessArticle

Experimental Investigation on Fatigue Crack Propagation in Surface-Hardened Layer of High-Speed Train Axles

by Chun Gao, Zhengwei Yu, Yuanyuan Zhang, Tao Fan, Bo Zhang, Huajian Song and Hang Su

Crystals 2025, 15(7), 638; https://doi.org/10.3390/cryst15070638 - 11 Jul 2025

Viewed by 207

Abstract

This study examines fatigue crack growth behavior in induction-hardened S38C axle steel with a gradient microstructure. High-frequency three-point bending fatigue tests were conducted to evaluate crack growth rates (da/dN) across three depth-defined regions: a hardened layer, a heterogeneous transition [...] Read more.

This study examines fatigue crack growth behavior in induction-hardened S38C axle steel with a gradient microstructure. High-frequency three-point bending fatigue tests were conducted to evaluate crack growth rates (da/dN) across three depth-defined regions: a hardened layer, a heterogeneous transition zone, and a normalized core. Depth-resolved da/dN–ΔK relationships were established, and Paris Law parameters were extracted. The surface-hardened layer exhibited the lowest crack growth rates and flattest Paris slope, while the transition zone showed notable scatter due to microstructural heterogeneity and residual stress effects. These findings provide experimental insight into the fatigue performance of gradient-structured axle steels and offer guidance for fatigue life prediction and inspection planning. Full article

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

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19 pages, 2624 KiB

Open AccessArticle

The Modeling of Electromagnetic Behavior in the High-Frequency Range of Al₂O₃ and TiO₂ Thermoplastic Composites in Support of Developing New Substrates for Flexible Electronics

by Radu F. Damian, Cristina Pachiu, Alexandra Mocanu, Alexandru Trandabat and Romeo Cristian Ciobanu

Crystals 2025, 15(7), 637; https://doi.org/10.3390/cryst15070637 - 10 Jul 2025

Viewed by 174

Abstract

The paper describes the simulation of energy absorption in polymer micro-composites that include dielectric inserts (commercial Al₂O₃ and TiO₂ particles, with three particle sizes of 1, 5 and 25 µm, respectively). The investigated frequency spectrum, mainly from 0.001 to [...] Read more.

The paper describes the simulation of energy absorption in polymer micro-composites that include dielectric inserts (commercial Al₂O₃ and TiO₂ particles, with three particle sizes of 1, 5 and 25 µm, respectively). The investigated frequency spectrum, mainly from 0.001 to 100 GHz, is designed for various uses as substrates in electronic technologies. The electromagnetic simulation software chosen was CST Studio Suite, which evaluates the power loss at different frequencies, playing a crucial role in creating the ideal structure of these substrates. The effective limits of the electromagnetic simulation are specified. It is shown that a considerable increase in absorption occurs, by a factor of 12 to 120, depending on the dielectric material used for the inserts and the mass ratio applied in the insertion technique. Dielectrics with high permittivity provide higher absorption, but also create a nonuniform field distribution within the material, resulting in a high peak-to-average absorption ratio. In scenarios where this behavior is intolerable, the technology must be carefully tuned to improve the consistency of the insertions in the substrate material. The final outcomes of the simulations indicated that for creating new substrates for flexible electronics, polyethylene composites with TiO₂ insertions are suggested, particularly at lower concentrations of up to 7% and with a larger radius, such as 25 μm, which could offer significant economic advantages considering that the current concept advises the use of costly particles ranging from nanoscale particles to those 1 μm in size and a composition exceeding 10%. Full article

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

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18 pages, 5941 KiB

Open AccessArticle

Non-Calcined Metal Tartrate Pore Formers for Lowering Sintering Temperature of Solid Oxide Fuel Cells

by Mehdi Choolaei, Mohsen Fallah Vostakola and Bahman Amini Horri

Crystals 2025, 15(7), 636; https://doi.org/10.3390/cryst15070636 - 10 Jul 2025

Viewed by 155

Abstract

This paper investigates the application of non-calcined metal tartrate as a novel alternative pore former to prepare functional ceramic composites to fabricate solid oxide fuel cells (SOFCs). Compared to carbonaceous pore formers, non-calcined pore formers offer high compatibility with various ceramic composites, providing [...] Read more.

This paper investigates the application of non-calcined metal tartrate as a novel alternative pore former to prepare functional ceramic composites to fabricate solid oxide fuel cells (SOFCs). Compared to carbonaceous pore formers, non-calcined pore formers offer high compatibility with various ceramic composites, providing better control over porosity and pore size distribution, which allows for enhanced gas diffusion, reactant transport and gaseous product release within the fuel cells’ functional layers. In this work, nanocrystalline gadolinium-doped ceria (GDC) and Ni-Gd-Ce-tartrate anode powders were prepared using a single-step co-precipitation synthesis method, based on the carboxylate route, utilising ammonium tartrate as a low-cost, environmentally friendly precipitant. The non-calcined Ni-Gd-Ce-tartrate was used to fabricate dense GDC electrolyte pellets (5–20 μm thick) integrated with a thin film of Ni-GDC anode with controlled porosity at 1300 °C. The dilatometry analysis showed the shrinkage anisotropy factor for the anode substrates prepared using 20 wt. The percentages of Ni-Gd-Ce-tartrate were 30 wt.% and 40 wt.%, with values of 0.98 and 1.01, respectively, showing a significant improvement in microstructural properties and pore size compared to those fabricated using a carbonaceous pore former. The results showed that the non-calcined pore formers can also lower the sintering temperature for GDC to below 1300 °C, saving energy and reducing thermal stresses on the materials. They can also help maintain optimal material properties during sintering, minimising the risk of unwanted chemical reactions or contamination. This flexibility enables the versatile designing and manufacturing of ceramic fuel cells with tailored compositions at a lower cost for large-scale applications. Full article

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

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13 pages, 2811 KiB

Open AccessArticle

A Silicon Complex of 1,4,7,10-Tetraazacyclododecane (Cyclen) with Unusual Coordination Geometry

by Uwe Böhme, Marcus Herbig and Betty Günther

Crystals 2025, 15(7), 635; https://doi.org/10.3390/cryst15070635 - 10 Jul 2025

Viewed by 130

Abstract

[1,4,7,10-Tetraazacyclododecano-κ⁴N^1,4,7,10(3-)]silicon(IV) chloride was synthesized from 1,4,7,10-tetraazacyclododecane (cyclen), n-butyl lithium, and silicon tetrachloride. The crystal structure analysis reveals that this cationic compound is a dimer in the solid state with pentacoordinate silicon atoms. The compound was characterized by melting [...] Read more.

[1,4,7,10-Tetraazacyclododecano-κ⁴N^1,4,7,10(3-)]silicon(IV) chloride was synthesized from 1,4,7,10-tetraazacyclododecane (cyclen), n-butyl lithium, and silicon tetrachloride. The crystal structure analysis reveals that this cationic compound is a dimer in the solid state with pentacoordinate silicon atoms. The compound was characterized by melting point, IR, and NMR spectroscopy. The quantum chemical analysis shows that this compound might be an interesting precursor to generate a mononuclear silicon (IV) complex with unusual reactivity due to nearly planar tetracoordinate coordination geometry at the silicon atom. Full article

(This article belongs to the Section Macromolecular Crystals)

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9 pages, 2121 KiB

Open AccessArticle

Using Second-Harmonic Generation Microscopy Images of Bee Honey Crystals to Detect Fructose Adulteration

by Manuel H. De la Torre-I, J. M. Flores-Moreno, C. Frausto-Reyes and Rafael Casillas-Peñuelas

Crystals 2025, 15(7), 634; https://doi.org/10.3390/cryst15070634 - 10 Jul 2025

Viewed by 189

Abstract

Second-harmonic generation microscopy is applied to mesquite honey samples with different fructose adulteration concentrations. As a proof of principle, mesquite honey is selected for this test, as it has a monofloral and spreadable-like-butter consistency, besides its economic relevance in the central region of [...] Read more.

Second-harmonic generation microscopy is applied to mesquite honey samples with different fructose adulteration concentrations. As a proof of principle, mesquite honey is selected for this test, as it has a monofloral and spreadable-like-butter consistency, besides its economic relevance in the central region of Mexico. Second-harmonic generation microscopy is an optical method that images microstructures, such as sugar crystals in bee honey, without the interference of the liquid phase. Each recorded image is spectrally registered using the photomultiplier detector of the microscope, resulting in several gray-level histograms that are numerically analyzed using signal and image processing techniques. Several samples are prepared, adulterated, and analyzed for this purpose. The inspection requires only a microscopic amount of honey, making it a suitable technique for rare and exotic honey samples that are harvested in limited quantities. The analysis of the experimental results reveals that the second-harmonic generation microscopy signal is sensitive to liquid fructose adulteration in honey, with its signal decreasing as the amount of added fructose increases. Full article

(This article belongs to the Section Industrial Crystallization)

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16 pages, 1918 KiB

Open AccessArticle

Optimization of In_xGa_1−xN P-I-N Solar Cells: Achieving 21% Efficiency Through SCAPS-1D Modeling

by Hassan Abboudi, Walid Belaid, Redouane En-nadir, Ilyass Ez-zejjari, Mohammed Zouini, Ahmed Sali and Haddou El Ghazi

Crystals 2025, 15(7), 633; https://doi.org/10.3390/cryst15070633 - 9 Jul 2025

Viewed by 224

Abstract

This study provides an in-depth numerical simulation to optimize the structure of InGaN-based p-i-n single homojunction solar cells using SCAPS-1D software. The cell comprised a p-type

{I n}_{0.6} {G a}_{0.4} N

layer, an intrinsic i-type [...] Read more.

This study provides an in-depth numerical simulation to optimize the structure of InGaN-based p-i-n single homojunction solar cells using SCAPS-1D software. The cell comprised a p-type

{I n}_{0.6} {G a}_{0.4} N

layer, an intrinsic i-type

{I n}_{0.52} {G a}_{0.48} N

layer, and an n-type

{I n}_{0.48} {G a}_{0.52} N

layer. A systematic parametric optimization methodology was employed, involving a sequential investigation of doping concentrations, layer thicknesses, and indium composition to identify the optimal device configuration. Initial optimization of doping levels established optimal concentrations of

N_{d} = 1 \times 10^{16} {c m}^{- 3}

for the p-layer and

N_{a} = 8 \times 10^{17} {c m}^{- 3}

for the n-layer. Subsequently, structural parameters were optimized through systematic variation of layer thicknesses while maintaining optimal doping concentrations. The comprehensive optimization culminated in the identification of an optimal device architecture featuring a p-type layer thickness of 0.2 μm, an intrinsic layer thickness of 0.4 μm, an n-type layer thickness of 0.06 μm, and an indium composition of x = 0.59 in the intrinsic layer. This fully optimized configuration achieved a maximum conversion efficiency (η) of 21.40%, a short-circuit current density (

J_{s c}

) of 28.2 mA/cm², and an open-circuit voltage (

V_{o c}

) of 0.874 V. The systematic optimization approach demonstrates the critical importance of simultaneous parameter optimization in achieving superior photovoltaic performance, with the final device configuration representing a 30.01% efficiency improvement compared to the baseline structure. These findings provide critical insights for improving the design and performance of InGaN-based solar cells, serving as a valuable reference for future experimental research. Full article

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

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15 pages, 1120 KiB

Open AccessArticle

Effects of Preheating on the Mechanical Properties of Dental Composites

by Maher S. Hajjaj, Lama F. Alhowirini, Raneem S. Alghamdi, Yasser M. Merdad, Hanan K. Filemban, Marwa Bawazir, Khawlah A. Alothman, Najla Al Turkestani and Saeed J. Alzahrani

Crystals 2025, 15(7), 632; https://doi.org/10.3390/cryst15070632 - 9 Jul 2025

Viewed by 228

Abstract

The aim of this study was to evaluate the mechanical properties (flexural strength (FS), flexural modulus (FM), Vickers microhardness (VMN), and shear bond strength (SBS)) of preheated composites. Two preheated composites (Z350XT and Proclinic) and one self-adhesive resin cement (RelyX™ U200) were used [...] Read more.

The aim of this study was to evaluate the mechanical properties (flexural strength (FS), flexural modulus (FM), Vickers microhardness (VMN), and shear bond strength (SBS)) of preheated composites. Two preheated composites (Z350XT and Proclinic) and one self-adhesive resin cement (RelyX™ U200) were used to fabricate specimens. All the specimens were subjected to thermocycling before their mechanical properties were evaluated. One-way ANOVA was used for statistical analysis, followed by Tukey’s post hoc test. The chi-square test was used to evaluate the failure modes after SBS test. Results: RelyX™ U200 had a significantly higher FS (106.22 ± 14.23 MPa) than Proclinic (85.76 ± 12.75 MPa) and Z350 (71.47 ± 22.98 MPa). Z350 (118.10 ± 11.3 GPa) and RelyX™ U200 (110.88 ± 13.44 GPa) had significantly higher FMs than Proclinic (83.72 ± 9.3 GPa). A significantly higher VHN was seen with Z350 (136.84 ± 11.52 VHN) compared to Proclinic (115.25 ± 17.15 VHN) and RelyX™ U200 (100.83 ± 12.69 VHN). Z350 had a higher SBS (20.75 ± 5.6 MPa) than RelyX™ U200 (15.4 ± 3.46 MPa), while Proclinic was the weakest among all the groups (6.76 ± 1.44 MPa). In the failure mode analysis, the mixed failure mode was predominantly seen in all groups. In conclusion, not all preheated composites behave the same and it is the clinician’s responsibility to select the appropriate material for every clinical situation. Full article

(This article belongs to the Special Issue Structural and Characterization of Composite Materials)

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14 pages, 1991 KiB

Open AccessArticle

Chemical Manipulation of the Collective Superspin Dynamics in Heat-Generating Superparamagnetic Fluids: An AC-Susceptibility Study

by Cristian E. Botez and Alex D. Price

Crystals 2025, 15(7), 631; https://doi.org/10.3390/cryst15070631 - 9 Jul 2025

Viewed by 132

Abstract

We use Co doping to alter the magnetic relaxation dynamics in superparamagnetic nanofluids made of 18 nm average diameter Fe₃O₄ nanoparticles immersed in Isopar M. Ac-susceptibility data recorded at different frequencies and temperatures, χ″vs. T|_f, reveals a major [...] Read more.

We use Co doping to alter the magnetic relaxation dynamics in superparamagnetic nanofluids made of 18 nm average diameter Fe₃O₄ nanoparticles immersed in Isopar M. Ac-susceptibility data recorded at different frequencies and temperatures, χ″vs. T|_f, reveals a major (~100 K) increase in the superspin blocking temperature of the Co_0.2Fe_2.8O₄-based fluid (CFO) compared to its Fe₃O₄ counterpart (FO). We ascribe this behavior to the strengthening of the interparticle magnetic dipole interactions upon Co doping, as demonstrated by the relative χ″-peak temperature variation per frequency decade

Φ = \frac{∆ T}{T \cdot ∆ l o g (f)}

, which decreases from Φ~0.15 in FO to Φ~0.025 in CFO. In addition, χ″vs. T|_f datasets from the CFO fluid reveal two magnetic events at temperatures T_p1 = 240 K and T_p2 = 275 K, both above the fluid’s freezing point (T_F = 197 K). We demonstrate that the physical rotation of the nanoparticles within the fluid, the Brown mechanism, is entirely responsible for the collective superspin relaxation observed at T_p1, whereas the Néel mechanism, the superspin flip across an energy barrier within the particle, is dominant at T_p2. We confirm this finding through fits of models that describe the temperature dependence of the relaxation time via the two mechanisms:

τ_{B} (T) = \frac{3 η_{0} V_{H}}{k_{B} T} \exp [\frac{E^{'}}{k_{B} (T - {T_{0}}^{'})}]

and

τ_{N} (T) = τ_{0} \exp [\frac{E_{B}}{k_{B} (T - T_{0})}]

. The best fits yield

γ_{0} = \frac{3 η_{0} V_{H}}{k_{B}}

= 1.5 × 10⁻⁸ s·K, E′/k_B = 7 03 K, and T₀′ = 201 K for the Brown relaxation, and E_B/k_B = 2818 K and T₀ = 143 K for the Néel relaxation. Full article

(This article belongs to the Special Issue Innovations in Magnetic Composites: Synthesis to Application)

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11 pages, 7411 KiB

Open AccessArticle

The Effects of Thermo-Mechanical Treatments on Microstructure and High-Temperature Mechanical Properties of a Nickel-Based Superalloy

by Zihan Kang, Yaxing Ma and Qian Lei

Crystals 2025, 15(7), 630; https://doi.org/10.3390/cryst15070630 - 9 Jul 2025

Viewed by 166

Abstract

The effects of thermo-mechanical treatment and different annealing temperatures on the microstructure and mechanical properties of a nickel-based superalloy were investigated by metallographic microscope, scanning electron microscope, and mechanical properties measurements. The results demonstrated that the tensile strength and elongation of the hot-rolled [...] Read more.

The effects of thermo-mechanical treatment and different annealing temperatures on the microstructure and mechanical properties of a nickel-based superalloy were investigated by metallographic microscope, scanning electron microscope, and mechanical properties measurements. The results demonstrated that the tensile strength and elongation of the hot-rolled samples were higher than those of the annealed ones. The ultimate engineering stress and engineering strain of the studied samples solid solution treated at 1175 °C for 4 h were 709 ± 19.8 MPa and 87.2 ± 1.4%, and the product of strength times elongation (PSE) was 61.8 GPa·%. These findings indicated that the thermo-mechanical treatment was an effective method to improve both the strength and the ductility of the nickel-based superalloy. Full article

(This article belongs to the Special Issue Emerging Topics of High-Performance Alloys (2nd Edition))

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15 pages, 4738 KiB

Open AccessArticle

Mechanical Performance of Ceria-Coated 3D-Printed Black Zirconia Cellular Structures After Solar Thermochemical CO/H₂ Fuel Production Cycles

by Fernando A. Costa Oliveira, Manuel Sardinha, Joaquim M. Justino Netto, Miguel Farinha, Marco Leite, M. Alexandra Barreiros, Stéphane Abanades and Jorge Cruz Fernandes

Crystals 2025, 15(7), 629; https://doi.org/10.3390/cryst15070629 - 8 Jul 2025

Viewed by 238

Abstract

Solar fuels production requires developing redox active materials with porous structures able to withstand thermochemical cycles with enhanced thermal stability under concentrated solar irradiation conditions. The mechanical performance of 3D-printed, macroporous black zirconia gyroid structures, coated with redox-active ceria, was assessed for their [...] Read more.

Solar fuels production requires developing redox active materials with porous structures able to withstand thermochemical cycles with enhanced thermal stability under concentrated solar irradiation conditions. The mechanical performance of 3D-printed, macroporous black zirconia gyroid structures, coated with redox-active ceria, was assessed for their suitability in solar thermochemical cycles for CO₂ and H₂O splitting. Experiments were conducted using a 1.5 kW solar furnace to supply the high-temperature concentrated heat to a windowed reaction chamber to carry out thermal redox cycling under realistic on-sun conditions. The ceria coating on ceramic structures improved the thermal stability and redox efficiency while minimizing the quantity of the redox material involved. Crushing strength measurements showed that samples not directly exposed to the concentrated solar flux retained their mechanical performance after thermal cycling (~10 MPa), while those near the concentrated solar beam focus exhibited significant degradation due to thermal stresses and the formation of Ce_xZr_1−xO₂ solid solutions (~1.5 MPa). A Weibull modulus of 8.5 was estimated, marking the first report of such a parameter for fused filament fabrication (FFF)-manufactured black zirconia with gyroid architecture. Failure occurred via a damage accumulation mechanism at both micro- and macro-scales. These findings support the viability of ceria-coated cellular ceramics for scalable solar fuel production and highlight the need for optimized reactor designs. Full article

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

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18 pages, 5983 KiB

Open AccessArticle

Fixed Particle Size Ratio Pure Copper Metal Powder Molding Fine Simulation Analysis

by Yuanbo Zhao, Mengyao Weng, Wenchao Wang, Wenzhe Wang, Hui Qi and Chongming Li

Crystals 2025, 15(7), 628; https://doi.org/10.3390/cryst15070628 - 5 Jul 2025

Viewed by 224

Abstract

In this paper, a discrete element method (DEM) coupled with a finite element method (FEM) was used to elucidate the impact of packing structures and size ratios on the cold die compaction behavior of pure copper powders. HCP structure, SC structure, and three [...] Read more.

In this paper, a discrete element method (DEM) coupled with a finite element method (FEM) was used to elucidate the impact of packing structures and size ratios on the cold die compaction behavior of pure copper powders. HCP structure, SC structure, and three random packing structures with different particle size ratios (1:2, 1:3, and 1:4) were generated by the DEM, and then simulated by the FEM to analyze the average relative density, von Mises stress, and force chain structures of the compact. The results show that for HCP and SC structures with a regular stacking structure, the average relative densities of the compact were higher than those of random packing structures, which were 0.9823, 0.9693, 0.9456, 0.9502, and 0.9507, respectively. Compared with their initial packing density, it could be improved by up to 21.13%. For the bigger particle in HCP and SC structures, the stress concentration was located between the adjacent layers, while in the small particles, it was located between contacted particles. During the initial compaction phase, smaller particles tend to occupy the voids between larger particles. As the pressure increases, larger particles deform plastically in a notable way to create a stabilizing force chain. This action reduces the axial stress gradient and improves radial symmetry. The transition from a contact-dominated to a body-stress-dominated state is further demonstrated by stress distribution maps and contact force vector analysis, highlighting the interaction between particle rearrangement and plasticity. Full article

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

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17 pages, 2576 KiB

Open AccessArticle

Discovery and Structural Characterization of a Novel Polymorph (Form III) of Alclometasone Dipropionate

by Gianfranco Lopopolo, M. Giovanna E. Papadopoulos, Corrado Cuocci, Giuseppe F. Mangiatordi, Antonio Lopalco, Emanuele Attolino and Rosanna Rizzi

Crystals 2025, 15(7), 627; https://doi.org/10.3390/cryst15070627 - 5 Jul 2025

Viewed by 188

Abstract

This study reports the discovery and structural characterization of a novel polymorph, designated as Form III, of Alclometasone dipropionate, a corticosteroid commonly used in the treatment of inflammatory dermatoses. Form III was obtained by modifying the crystallization conditions reported in prior art and [...] Read more.

This study reports the discovery and structural characterization of a novel polymorph, designated as Form III, of Alclometasone dipropionate, a corticosteroid commonly used in the treatment of inflammatory dermatoses. Form III was obtained by modifying the crystallization conditions reported in prior art and was thoroughly characterized using Powder X-ray Diffraction (PXRD), Fourier Transform Infrared (FT-IR) spectroscopy, melting-point determination, Differential Scanning Calorimetry (DSC), Thermogravimetric Analysis (TGA), including its first derivative (DTG), optical microscopy, and Scanning Electron Microscopy (SEM). In parallel, pure Form II, previously observed only in mixtures with Form I, was successfully isolated and characterized using the same analytical techniques. Both forms were compared in terms of structural, thermal, and morphological properties. PXRD analysis revealed that Form III crystallizes in a triclinic system; FT-IR spectroscopy revealed unique vibrational signatures, and microscopy showed rod-like crystal morphology. The discovery of Form III expands the current understanding of the solid-state landscape of Alclometasone dipropionate and opens opportunities for the identification of new industrial purification methods for the compound. Full article

(This article belongs to the Special Issue Celebrating the 10th Anniversary of International Crystallography)

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24 pages, 7448 KiB

Open AccessArticle

A Novel Approach to Quantitatively Account on Deposition Efficiency by Direct Energy Deposition: Case of Hardfacing-Coated AISI 304 SS

by Gabriele Grima, Kamal Sleem, Alberto Santoni, Gianni Virgili, Vincenzo Foti, Marcello Cabibbo and Eleonora Santecchia

Crystals 2025, 15(7), 626; https://doi.org/10.3390/cryst15070626 - 5 Jul 2025

Viewed by 265

Abstract

Nickel-based coatings have been demonstrated to effectively enhance the surface performance of stainless-steel components. The present study investigates the deposition efficiency and quality of Colmonoy 227-F nickel alloy coatings on AISI 304 stainless steel using direct energy deposition (DED). The work focuses on [...] Read more.

Nickel-based coatings have been demonstrated to effectively enhance the surface performance of stainless-steel components. The present study investigates the deposition efficiency and quality of Colmonoy 227-F nickel alloy coatings on AISI 304 stainless steel using direct energy deposition (DED). The work focuses on the relationships between process parameters, microstructural features, and mechanical properties. A total of sixteen process parameter combinations were studied, varying laser power and scanning speed to establish optimal deposition conditions and to evaluate coating morphology, surface topology, dilution behavior, and mechanical performance. The surface geometry was analyzed using three-dimensional digital confocal microscopy. New material distribution (MD) indices were developed to quantify spatial uniformity and integrity of single coating scan tracks (CSTs) across the XY, XZ, and YZ planes. The optimal process was identified around 900 W laser power, balancing deposition efficiency and structural integrity. Scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) reveal a gradual compositional transition between coating and substrate. The results of the microhardness test demonstrate a consistent gradient in mechanical properties, extending from the coating to the substrate. Coatings were found to achieve a hardness level of up to 600 HK. These findings establish a new benchmark for evaluating DED high-performance coatings and offer a scalable methodology for optimizing additive manufacturing processes in surface engineering applications. Full article

(This article belongs to the Special Issue Recent Advances in Microstructure and Properties of Metals and Alloys)

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