Crystals

17 pages, 2103 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 (registering DOI) - 5 Jul 2025

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)

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 (registering DOI) - 5 Jul 2025

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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13 pages, 11057 KiB

Open AccessArticle

Microstructure, Hardness and Tribological Characteristics of High-Entropy Coating Obtained by Detonation Spraying

by Zhuldyz Sagdoldina, Laila Sulyubayeva, Dastan Buitkenov and Yedilzhan Kambarov

Crystals 2025, 15(7), 625; https://doi.org/10.3390/cryst15070625 (registering DOI) - 4 Jul 2025

Abstract

In this study, powders based on a high-entropy AlCoCrFeNi alloy obtained by mechanical alloying were successfully applied to a 316L stainless steel substrate by detonation spraying under various conditions. Their microstructural features, phase composition, hardness, and wear resistance were studied. A comparative analysis [...] Read more.

In this study, powders based on a high-entropy AlCoCrFeNi alloy obtained by mechanical alloying were successfully applied to a 316L stainless steel substrate by detonation spraying under various conditions. Their microstructural features, phase composition, hardness, and wear resistance were studied. A comparative analysis between the initial powder and the coatings was performed, including phase transformation modeling using Thermo-Calc under non-equilibrium conditions. The results showed that the phase composition of the powder and coatings includes body-centered cubic lattice (BCC), its ordered modification (B2), and face-centered cubic lattice FCC phases, which is consistent with the predictions of the Scheil solidification model, describing the process of non-equilibrium solidification, assuming no diffusion in the solid phase and complete mixing in the liquid phase. Rapid solidification and high-speed impact deformation of the powder led to significant grain refinement in the detonation spraying coating, which ultimately improved the mechanical properties at the micro level. The data obtained demonstrate the high efficiency of the AlCoCrFeNi coating applied by detonation spraying and confirm its potential for use in conditions of increased wear and mechanical stress. AlCoCrFeNi coatings may be promising for use as structural materials in the future. Full article

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

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16 pages, 4823 KiB

Open AccessArticle

Magnetic Behavior of Co²⁺-Doped NiFe₂O₄ Nanoparticles with Single-Phase Spinel Structure

by Fatemeh Vahedrouz, Mehdi Alizadeh, Abbas Bahrami and Farnaz Heidari Laybidi

Crystals 2025, 15(7), 624; https://doi.org/10.3390/cryst15070624 (registering DOI) - 4 Jul 2025

Abstract

This study reports the synthesis and characterization of Co_xNi_1−xFe₂O₄ (x = 0, 0.2, 0.4, 0.6, 0.8, 1) nanoparticles using a co-precipitation method. In this approach, metal ions are precipitated in the presence of a stabilizing agent, [...] Read more.

This study reports the synthesis and characterization of Co_xNi_1−xFe₂O₄ (x = 0, 0.2, 0.4, 0.6, 0.8, 1) nanoparticles using a co-precipitation method. In this approach, metal ions are precipitated in the presence of a stabilizing agent, which is a common and effective method for nanoparticle preparation. The microstructure and magnetic properties were studied after calcination at 600 °C and heat treatment at 1000 °C. X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy confirmed the formation of a single-phase spinel structure. The average crystallite size, calculated using the (311) diffraction peak and the Scherrer equation, ranged from 13 to 19 nm. Scanning electron microscopy (SEM) showed that the nanoparticles had a spherical morphology. Thermogravimetric and differential thermal analysis (TG-DTA) revealed a three-step weight loss process. Magnetic measurements, including remanent magnetization, saturation magnetization, and coercivity, were performed using a vibrating sample magnetometer (VSM) at room temperature. The replacement of Ni²⁺ with Co²⁺ enhanced the magnetic properties, resulting in increased magnetic moment and anisotropy. These effects are attributed to changes in cation distribution, exchange interactions, surface effects, and magnetocrystalline anisotropy. Overall, Co²⁺ doping improved the magnetic behavior of nickel ferrite, indicating its potential for application in memory devices and magnetic recording media. Full article

(This article belongs to the Special Issue Polycrystalline Materials—from Microstructure Characterization to Applications)

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9 pages, 1701 KiB

Open AccessArticle

Effects of [Zn_0.5Si_0.5]³⁺ Substitution on Microwave Dielectric Properties of ZnAl_2-x(Zn_0.5Si_0.5)_xO₄ Ceramics

by Xuekai Lan, Bairui Chen, Huatao Tang, Changzhi Yin, Bin Tian and Wen Lei

Crystals 2025, 15(7), 623; https://doi.org/10.3390/cryst15070623 (registering DOI) - 4 Jul 2025

Abstract

Microwave dielectric ceramics are indispensable in modern communication technologies, playing a pivotal role in components such as filters, oscillators, and antennas. Among these materials, ZnAl₂O₄ ceramics have garnered attention for their excellent quality factor (Q × f) and [...] Read more.

Microwave dielectric ceramics are indispensable in modern communication technologies, playing a pivotal role in components such as filters, oscillators, and antennas. Among these materials, ZnAl₂O₄ ceramics have garnered attention for their excellent quality factor (Q × f) and low dielectric constant (ε_r). However, their high sintering temperature (~1650 °C) limits practical applications. This study investigates ZnAl_2-x(Zn_0.5Si_0.5)_xO₄ (ZAZS) (x = 0.1–0.9) ceramics, where [Zn_0.5Si_0.5]³⁺ substitutes Al³⁺, to reduce sintering temperature while maintaining high-performance microwave dielectric properties. ZAZS ceramics were synthesized via the solid-state reaction method and characterized for their structural, morphological, and dielectric properties. X-ray diffraction analysis confirmed the formation of a single-phase solid solution up to x = 0.8, with minor secondary phases appearing at x = 0.9. The substitution increased lattice parameters and enhanced material densification, as observed through SEM and relative density calculations. Microwave dielectric measurements showed that ZAZS ceramics achieved a maximum Q × f of 20,200 GHz and a τ_f value reduced to −62 ppm/°C at x = 0.8, while ε_r decreased from 7.90 to 6.98. Bond-valence calculations reveal that the reduction of the average Al/Zn/Si–O bond valence weakens octahedral rigidity, systematically tuning τ_f toward zero. These results demonstrate that ZAZS ceramics, with a reduced sintering temperature of 1400 °C, exhibit excellent potential for application in low-loss microwave devices. Full article

(This article belongs to the Section Polycrystalline Ceramics)

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9 pages, 2068 KiB

Open AccessArticle

Effects of Ge-Doping on Thermoelectric Performance of Polycrystalline Cubic Sn_0.5Ag_0.25Bi_0.25Se_0.50Te_0.50

by Haoyu Zhao, Junliang Zhu, Zhonghe Zhu, Lin Bo, Wenying Wang, Xingshuo Liu, Changcun Li and Degang Zhao

Crystals 2025, 15(7), 622; https://doi.org/10.3390/cryst15070622 - 4 Jul 2025

Abstract

Cubic phase SnSe-based materials have great potential in the field of thermoelectricity due to their reduced carrier scattering, increased band degeneracy, and ultra-low lattice thermal conductivity. Nevertheless, systematic studies on the influence of element doping on the thermoelectric properties of cubic SnSe-based materials [...] Read more.

Cubic phase SnSe-based materials have great potential in the field of thermoelectricity due to their reduced carrier scattering, increased band degeneracy, and ultra-low lattice thermal conductivity. Nevertheless, systematic studies on the influence of element doping on the thermoelectric properties of cubic SnSe-based materials are still relatively scarce. To enrich the research in this field, this work investigates the effects of Ge doping on the phase composition, electrical and thermal transport properties of cubic Sn_0.50Ag_0.25Bi_0.25Se_0.50Te_0.50 thermoelectric materials. X-ray diffraction (XRD) analysis confirmed that the Ge-doped samples exhibited a single cubic phase structure, while scanning electron microscopy (SEM) and energy-dispersive spectroscopy (EDS) revealed a uniform distribution of elements within the samples. The results indicate that increasing the Ge doping content substantially enhances their electrical conductivity, albeit at the expense of elevated thermal conductivity. By optimizing the content of Ge-doping, the thermoelectric figure of merit (ZT) reached 0.74 at 750 K. Notably, while moderate Ge doping enhances electrical transport properties, excessive doping leads to a significant rise in thermal conductivity, ultimately constraining further thermoelectric performance gains. Full article

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12 pages, 3225 KiB

Open AccessArticle

Multiple Slater Determinants and Strong Spin-Fluctuations as Key Ingredients of the Electronic Structure of Electron- and Hole-Doped Pb_10−xCu_x(PO₄)₆O

by Dimitar Pashov, Swagata Acharya, Stephan Lany, Daniel S. Dessau and Mark van Schilfgaarde

Crystals 2025, 15(7), 621; https://doi.org/10.3390/cryst15070621 - 2 Jul 2025

Abstract

LK-99, with chemical formula Pb_10−xCu_x(PO₄)₆O, was recently reported to be a room-temperature superconductor. While this claim has met with little support in a flurry of ensuing work, a variety of calculations (mostly based on [...] Read more.

LK-99, with chemical formula Pb_10−xCu_x(PO₄)₆O, was recently reported to be a room-temperature superconductor. While this claim has met with little support in a flurry of ensuing work, a variety of calculations (mostly based on density-functional theory) have demonstrated that the system possesses some unusual characteristics in the electronic structure, in particular flat bands. We have established previously that within DFT, the system is insulating with many characteristics resembling the classic cuprates, provided the structure is not constrained to the P3(143) symmetry nominally assigned to it. Here we describe the basic electronic structure of LK-99 within self-consistent many-body perturbative approach, quasiparticle self-consistent GW (QSGW) approximation and their diagrammatic extensions. QSGW predicts that pristine LK-99 is indeed a Mott/charge transfer insulator, with a bandgap gap in excess of 3 eV, whether or not constrained to the P3(143) symmetry. When Pb₉Cu(PO₄)₆O is hole-doped, the valence bands modify only slightly, and a hole pocket appears. However, two solutions emerge: a high-moment solution with the Cu local moment aligned parallel to neighbors, and a low-moment solution with Cu aligned antiparallel to its environment. In the electron-doped case the conduction band structure changes significantly: states of mostly Pb character merge with the formerly dispersionless Cu d state, and high-spin and low spin solutions once again appear. Thus we conclude that with suitable doping, the ground state of the system is not adequately described by a band picture, and that strong correlations are likely. Irrespective of whether this system class hosts superconductivity or not, the transition of Pb₁₀(PO₄)₆O from being a band insulator to Pb₉Cu(PO₄)₆O, a Mott insulator, and multi-determinantal nature of doped Mott physics make this an extremely interesting case-study for strongly correlated many-body physics. Full article

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18 pages, 15258 KiB

Open AccessArticle

Nanoindentation-Induced Deformation Mechanisms in Sintered Silver: A Multiscale Study Combining Experimental and Molecular Dynamics Simulations

by Yiping Sun, Xinyue Wang, Haixue Chen and Pan Liu

Crystals 2025, 15(7), 620; https://doi.org/10.3390/cryst15070620 - 2 Jul 2025

Abstract

Sintered silver, widely used in WBG electronic device packaging for its excellent electrothermal properties and high-temperature stability, faces challenges in macroscopic mechanical behavior and reliability due to porosity, especially for pressureless sintered silver. However, the intrinsic pores inside sintered material introduce uncertainties during [...] Read more.

Sintered silver, widely used in WBG electronic device packaging for its excellent electrothermal properties and high-temperature stability, faces challenges in macroscopic mechanical behavior and reliability due to porosity, especially for pressureless sintered silver. However, the intrinsic pores inside sintered material introduce uncertainties during nanoindentation tests for mechanical characterization. This study investigated the impact of pore distribution on the dislocation behavior of pressureless sintered silver during nanoindentation. Firstly, pressureless sintered silver models with 8–33% porosity were prepared and characterized through scanning electron microscope (SEM) for porosity, electron backscatter diffraction (EBSD) for the geometrically necessary dislocation (GND) density distribution, and transmission electron microscopy (TEM) for the crystal structure and microscopic strain. The EBSD results indicated that nanoindentation caused localized plastic deformation in sintered silver, closely related to its porous structure. The TEM results revealed that sintered silver undergoes dislocation slip during nanoindentation, leading to complex dislocation network formation, while the strain decreased with distance from the indentation. To further investigate the relationship of pore distribution and dislocation behavior during nanoindentation, molecular dynamics (MD) simulations were carried out. The MD results revealed that the dislocation distribution was consistent with the EBSD and TEM results. During loading, with the increased porosity from 10% to 23.7%, the total dislocation length was reduced by 63%, while it led to a 38% increase in total dislocation length with the average pore size decreased from 3.84 nm to 2.88 nm under similar porosity conditions. This study improves the understanding of the deformation mechanisms of porous sintered silver under nanoindentation and provides insight into the mechanical characterization of porous materials. Full article

(This article belongs to the Section Crystal Engineering)

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10 pages, 1898 KiB

Open AccessArticle

Crystal Structure of 4′-Phenyl-1′,4′-Dihydro-2,2′:6′,2″-Terpyridine: An Intermediate from the Synthesis of Phenylterpyridine

by Alexander Sedykh, Maksim Zhernakov, Mariia Becker, Dirk G. Kurth and Klaus Müller-Buschbaum

Crystals 2025, 15(7), 619; https://doi.org/10.3390/cryst15070619 - 1 Jul 2025

Abstract

The intermediate compound 4′-phenyl-1′,4′-dihydro-2,2′:6′,2″-terpyridine (pdhtpy) was isolated for the first time during the synthesis of 4′-phenyl-2,2′:6′,2″-terpyridine (ptpy) and characterised by single-crystal X-ray diffraction. Pdhtpy crystallises in the triclinic crystal system with space group P

\bar{1}

with the following [...] Read more.

The intermediate compound 4′-phenyl-1′,4′-dihydro-2,2′:6′,2″-terpyridine (pdhtpy) was isolated for the first time during the synthesis of 4′-phenyl-2,2′:6′,2″-terpyridine (ptpy) and characterised by single-crystal X-ray diffraction. Pdhtpy crystallises in the triclinic crystal system with space group P

\bar{1}

with the following unit cell parameters at 100 K: a = 6.1325(4) Å; b = 8.2667(5) Å; c = 16.052(2) Å; α = 86.829(2)°; β = 82.507(2)°; γ = 84.603(2)°; V = 802.49(9) Å³. The absence of stabilising electron-withdrawing groups renders pdhtpy prone to oxidative conditions. Pdhtpy was obtained as a mixture with ptpy, confirmed by Rietveld refinement of the powder X-ray diffraction pattern. Notably, pdhtpy is the first solid-state 1,4-dihydropyridine lacking electron-withdrawing groups at both positions 3 and 5, distinguishing it from Hantzsch esters and related compounds. Full article

(This article belongs to the Section Organic Crystalline Materials)

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25 pages, 6245 KiB

Open AccessReview

Effect of Interstitial Oxygen on the Microstructure and Mechanical Properties of Titanium Alloys: A Review

by Yaojia Ren, Jiajun Xu, Yingkang Wei, Yingying Liu, Jilei Zhu and Shifeng Liu

Crystals 2025, 15(7), 618; https://doi.org/10.3390/cryst15070618 - 30 Jun 2025

Abstract

Titanium alloys are of significant value in aerospace, biomedical, and marine engineering applications due to their excellent specific strength and favorable biocompatibility. As a crucial interstitial solute, oxygen significantly influences the mechanical properties of titanium alloys. However, excessive oxygen content can lead to [...] Read more.

Titanium alloys are of significant value in aerospace, biomedical, and marine engineering applications due to their excellent specific strength and favorable biocompatibility. As a crucial interstitial solute, oxygen significantly influences the mechanical properties of titanium alloys. However, excessive oxygen content can lead to severe embrittlement and a significant reduction in ductility. This paper systematically reviews the mechanisms of microstructural evolution induced by oxygen in conventionally manufactured titanium alloys and their impact on mechanical properties, highlighting that conventional processes require complex post-treatments (PT) to achieve a balance between strength and plasticity. This assessment further explores the regulatory mechanisms of oxygen on the microstructure and mechanical properties of laser additive manufactured (LAM) titanium alloys, elucidating the fundamental phenomena regarding the oxygen–microstructure–property relationship. Finally, based on the current research progress, this paper provides an outlook on the future development directions and key research priorities in this field. This review offers valuable insights into the role of oxygen in titanium alloys and the development of high-performance titanium alloys. Full article

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

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14 pages, 6081 KiB

Open AccessArticle

Investigation on Tensile Behavior of Solid Solution-Strengthened Ni-Co-Cr-Based Superalloy During Long-Term Aging

by Wanqi Hou, Xianjun Guan, Jiaqi Wang, Jinrong Wu, Lanzhang Zhou and Zheng Jia

Crystals 2025, 15(7), 617; https://doi.org/10.3390/cryst15070617 - 30 Jun 2025

Abstract

This study investigated how long-term aging (750 °C and 950 °C) affects the microstructure and room-temperature tensile properties of the Ni-Co-Cr superalloy GH3617. Characterization (SEM, EDS, EBSD) showed that initial aging (750 °C, 500 h) formed discontinuous M₂₃C₆ carbides, pinning [...] Read more.

This study investigated how long-term aging (750 °C and 950 °C) affects the microstructure and room-temperature tensile properties of the Ni-Co-Cr superalloy GH3617. Characterization (SEM, EDS, EBSD) showed that initial aging (750 °C, 500 h) formed discontinuous M₂₃C₆ carbides, pinning grain boundaries and improving strength. Prolonged aging (750 °C, 5000 h) caused M₂₃C₆ to coarsen into brittle chain-like structures (width up to 1.244 μm) and precipitated M₆C carbides, degrading grain boundaries. Aging at 950 °C accelerated this coarsening via LSW kinetics (rate constant: 6.83 × 10⁻² μm³/s), with Mo segregation promoting M₆C formation. Tensile properties resulted from competing γ′ precipitation strengthening (post-aging strength increased up to 23.3%) and grain boundary degradation (elongation dropped from 70.1% to 43.3%). Fracture shifted from purely intergranular (cracks along M₂₃C₆/γ interfaces at 750 °C) to mixed mode (cracks initiated by M₆C fragmentation at 950 °C). These insights support superalloy microstructure optimization and lifetime prediction. Full article

(This article belongs to the Special Issue Crystal Plasticity (4th Edition))

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12 pages, 19537 KiB

Open AccessArticle

Microstructure, Mechanical Properties, Deformation Behavior, and Crystallographic Texture of the Al-Gd-Cr-Ti Quaternary Alloy for Thermal Neutron Absorption

by Sayed M. Amer, Dmitry I. Nikolayev, Tatiana A. Lychagina, Abdelmoneim El-Khouly, Ruslan Yu. Barkov, Alexey S. Prosviryakov, Anastasia V. Mikhaylovskaya, Maria V. Glavatskikh and Andrey V. Pozdniakov

Crystals 2025, 15(7), 616; https://doi.org/10.3390/cryst15070616 - 30 Jun 2025

Abstract

In this work, we report the identification of a novel quaternary intermetallic phase (Al₂₁GdCrTi) formed during the solidification of a novel Al-Gd-Cr-Ti alloy, which has not been previously documented in the literature to the best of our knowledge. The study also [...] Read more.

In this work, we report the identification of a novel quaternary intermetallic phase (Al₂₁GdCrTi) formed during the solidification of a novel Al-Gd-Cr-Ti alloy, which has not been previously documented in the literature to the best of our knowledge. The study also provides a detailed analysis of microstructure evolution, texture behavior, and the mechanical strengthening effect of rolling processes, along with neutron absorption performance. XRD analysis reveals that the intensity of (022), (113) planes of the as-hot-cold-rolled sample is higher than that of the as-cast due to the change in the direction of some grains in these planes during rolling. The results indicate that the studied alloys scatter neutrons about 100 times less than a nearly pure aluminum alloy. The hardness of the as-cast alloy increased from 36 to 53 HV after cold rolling and to 50 HV after hot rolling-cold rolling. Hot-cold-rolled alloy has a yield strength of 160 MPa and an ultimate tensile strength of 181 MPa, while maintaining an elongation of 11.3%. The studied alloys, containing 4.2 wt.% of the alloying elements 3.8Gd, 0.2Cr, and 0.2Ti (Al-3.8Gd-0.2Cr-0.2Ti), exhibited a yield strength 28 MPa higher than those containing 21 wt.% of the alloying elements 5Cu, 6Gd, and 8Bi (Al-5Cu-6Gd-8Bi). The studied alloys form the basis for the development of high-technology Al-Gd alloys for neutron shielding. Full article

(This article belongs to the Special Issue Development of Light Alloys and Their Applications)

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21 pages, 5673 KiB

Open AccessArticle

Functionalized Magnetic Nanomaterial Based on SiO₂/Ca(OH)₂-Coated Clusters Decorated with Silver Nanoparticles for Dental Applications

by Izabell Crăciunescu, George Marian Ispas, Alexandra Ciorîta and Rodica Paula Turcu

Crystals 2025, 15(7), 615; https://doi.org/10.3390/cryst15070615 - 30 Jun 2025

Abstract

In this study, an innovative dental functionalized magnetic nanomaterial was developed by incorporating hydrophilic magnetic clusters as an alternative to conventional isolated magnetic nanoparticles, introducing a novel structural and functional concept in dental applications. The ~100 nm magnetic clusters—composed of densely packed 7 [...] Read more.

In this study, an innovative dental functionalized magnetic nanomaterial was developed by incorporating hydrophilic magnetic clusters as an alternative to conventional isolated magnetic nanoparticles, introducing a novel structural and functional concept in dental applications. The ~100 nm magnetic clusters—composed of densely packed 7 nm Fe₃O₄ nanoparticles—were sequentially coated with a silica (SiO₂) layer (3–5 nm) to improve chemical and mechanical stability, followed by an outer calcium hydroxide [Ca(OH)₂] layer to enhance bioactivity and optical integration. This bilayer architecture enables magnetic field-assisted positioning and improved dispersion within dental resin matrices. Silver nanoparticles were incorporated to enhance antimicrobial activity and reduce biofilm formation. The synthesis process was environmentally friendly and scalable. Comprehensive physicochemical characterization confirmed the material’s functional performance. Saturation magnetization decreased progressively with surface functionalization, from 62 to 14 emu/g, while the zeta potential became increasingly negative (from −2.42 to −22.5 mV), supporting its ability to promote apatite nucleation. The thermal conductivity (0.527 W/m·K) closely matched that of human dentin (0.44 W/m·K), and the colorimetric analysis showed improved brightness (ΔL = 5.3) and good color compatibility (ΔE = 11.76). These results indicate that the functionalized magnetic nanomaterial meets essential criteria for restorative use and holds strong potential for future clinical applications. Full article

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

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14 pages, 2423 KiB

Open AccessArticle

Properties of Cast Iron Produced with a Limited Share of Pig Iron in the Charge

by Krzysztof Janerka and Jan Jezierski

Crystals 2025, 15(7), 614; https://doi.org/10.3390/cryst15070614 - 30 Jun 2025

Abstract

The article presents issues related to the melting of cast iron with a limited or zero share of pig iron in the charge. The results of melts conducted in electric induction furnaces are presented. The elimination of pig iron and its replacement with [...] Read more.

The article presents issues related to the melting of cast iron with a limited or zero share of pig iron in the charge. The results of melts conducted in electric induction furnaces are presented. The elimination of pig iron and its replacement with steel or return scrap is highly significant in the context of sustainable production and product life cycle assessment (LCA). The paper presents the results of research carried out during melts conducted under both laboratory and industrial conditions. The chemical composition of the cast iron, its physicochemical properties obtained from the analysis of the cooling curve and its derivative, as well as the structure, were analyzed. It was found that cast iron produced using high-quality steel scrap contains fewer sulfur and phosphorus impurities. However, it was also observed that such cast iron exhibits reduced nucleation ability, which can be improved by applying an inoculation process. Full article

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18 pages, 3863 KiB

Open AccessArticle

The Temperature Sensitivity of the Piezoelectric Thickness Shear Mode of α-GeO₂ Single Crystals

by Philippe Papet and Pascale Armand

Crystals 2025, 15(7), 613; https://doi.org/10.3390/cryst15070613 - 30 Jun 2025

Abstract

This paper focuses on identifying temperature-compensated Y-cuts (using a Cartesian coordinate system) in a piezoelectric α-GeO₂ single crystal, which is isostructural–quartz α-SiO₂. The study aims to minimize the frequency drift of the thickness shear mode by analyzing the resonant frequency’s [...] Read more.

This paper focuses on identifying temperature-compensated Y-cuts (using a Cartesian coordinate system) in a piezoelectric α-GeO₂ single crystal, which is isostructural–quartz α-SiO₂. The study aims to minimize the frequency drift of the thickness shear mode by analyzing the resonant frequency’s first- and second-order temperature coefficients T_f⁽¹⁾ and T_f⁽²⁾. To obtain these, the first-order, T_Cij⁽¹⁾, and second-order, T_Cij⁽²⁾, temperature coefficients of the elastic constant, C_ij, previously obtained from room temperature up to 900 °C, were calculated. Upon heating, the thermal behavior of the elastic constants indicated that some, such as C₁₁ and C₃₃, are stable over a range of temperatures, while others, such as C₄₄ and C₆₆, increase with the temperature. This paper also explores a family of singly and doubly rotated Y-cuts of α-GeO₂, revealing cuts with a potential application for temperature compensation and/or linear dependence over the temperature range. The results are compared with those of the well-known piezoelectric isomorph material α-SiO₂. The findings highlight that α-GeO₂ is a promising material for piezoelectric devices in high-temperature environments, outperforming α-SiO₂ (α-quartz), which is limited by a solid–solid phase transition at 573 °C. Full article

(This article belongs to the Section Crystal Engineering)

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15 pages, 2316 KiB

Open AccessArticle

Enhancement of Ethylene-Butene Terpolymer Performance via Carbon Nanotube-Induced Nanodispersion of Montmorillonite Layers

by Li Zhang, Jianming Liu, Duanjiao Li, Wenxing Sun, Zhi Li, Yongchao Liang, Qiang Fu, Nian Tang, Bo Zhang, Fei Huang, Xuelian Fan, Yuansi Wei, Pengxiang Bai and Yuqi Wang

Crystals 2025, 15(7), 612; https://doi.org/10.3390/cryst15070612 - 30 Jun 2025

Abstract

In this study, the enhancement mechanism of the nano-dispersion of stearic acid-modified montmorillonite (SMMT) induced by carbon nanotubes (CNTs) in ethylene-butene terpolymer (EBT) was comprehensively investigated, and the regulation effect of composite fillers on EBT properties was revealed. Scanning electron microscopy (SEM) confirmed [...] Read more.

In this study, the enhancement mechanism of the nano-dispersion of stearic acid-modified montmorillonite (SMMT) induced by carbon nanotubes (CNTs) in ethylene-butene terpolymer (EBT) was comprehensively investigated, and the regulation effect of composite fillers on EBT properties was revealed. Scanning electron microscopy (SEM) confirmed that SMMT achieved homogeneous nanoscale dispersion after CNT addition, and the size of aggregates was greatly reduced. Four-cycle strain-scanning analysis revealed a 200% increase in rubber–filler (R-F) interaction strength due to CNT incorporation. At the optimal CNT/SMMT ratio of 1:5, the EBT composites exhibited a 40.4% increase in Young’s modulus, 71.4% enhancement in tensile strength, and maintained 250% elongation at break, effectively addressing the strength–toughness trade-off of traditional rigid fillers. Thermogravimetric analysis (TGA) showed near 20 °C elevation in EBT composites’ maximum decomposition temperature, while water contact angle measurements indicated a hydrophobicity increase to 117.5° and water absorption rate below 0.2%. The quantitative improvement in thermal oxidation stability and hydrophobic barrier performance was achieved simultaneously. Full article

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17 pages, 4438 KiB

Open AccessArticle

Y₅F₃[AsO₃]₄ and Y₅Cl₃[AsO₃]₄: Two Non-Isostructural Yttrium Halide Oxoarsenates(III) and Their Potential as Hosts for Luminescent Eu³⁺- and Tb³⁺-Doping

by Ralf J. C. Locke, Martina Mikuta, Florian Ledderboge, Frank C. Zimmer, Henning A. Höppe and Thomas Schleid

Crystals 2025, 15(7), 611; https://doi.org/10.3390/cryst15070611 - 30 Jun 2025

Abstract

Y₅F₃[AsO₃]₄ crystallizes needle-shaped in the tetragonal space group P4/ncc with the lattice parameters a = 1143.80(8) pm, c = 1078.41(7) pm and c/a = 0.9428 for Z = 4. The yttrium-fluoride substructure [...] Read more.

Y₅F₃[AsO₃]₄ crystallizes needle-shaped in the tetragonal space group P4/ncc with the lattice parameters a = 1143.80(8) pm, c = 1078.41(7) pm and c/a = 0.9428 for Z = 4. The yttrium-fluoride substructure linked via secondary contacts forms a three-dimensional network

\begin{matrix} 3 \\ \infty \end{matrix}

{[Y₅F₃]¹²⁺} and the remaining part consists of ψ¹-tetrahedral [AsO₃]³⁻ units, which leave lone-pair channels along [001]. In contrast, platelet-shaped Y₅Cl₃[AsO₃]₄ crystals adopt the monoclinic space group C2/c with the lattice parameters a = 1860.56(9) pm, b = 536.27(3) pm, c = 1639.04(8) pm and β = 105.739(3)° for Z = 4. Condensation of [(Y1,2)O₈]¹³⁻ polyhedra via four common edges each leads to fluorite-like

\begin{matrix} 2 \\ \infty \end{matrix}

{[(Y1,2)O

\begin{matrix} e \\ 8 / 2 \end{matrix}

]⁵⁻} layers spreading out parallel to the (100) plane. Their three-dimensional linkage occurs via the (Y3)³⁺ cations with their Cl⁻ ligands on the one hand and the As³⁺ cations with their lone-pairs of electrons on the other, which also form within [AsO₃]³⁻ anions lone-pair channels along [010]. Both colorless compounds can be obtained by solid-state reactions from corresponding mixtures of the binaries (Y₂O₃, As₂O₃ and YX₃ with X = F and Cl) at elevated temperatures of 825 °C, most advantageously under halide-flux assistance (CsBr for Y₅F₃[AsO₃]₄ and ZnCl₂ for Y₅Cl₃[AsO₃]₄). By replacing a few percent of YX₃ with EuX₃ or TbX₃, Eu³⁺- or Tb³⁺-doped samples are accessible, which show red or green luminescence upon excitation with ultraviolet radiation. Full article

(This article belongs to the Special Issue Synthesis and Crystal Structure of Rare-Earth Metal Compounds)

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18 pages, 9619 KiB

Open AccessArticle

Fractional Vortex Dynamics in Two-Band Superconductors with Linear Normal Strips

by Ariday S. Mosquera-Polo, Edwan A. Aríza-Echeverri, Cristhian Aguirre, Luis F. Muñoz-Martínez and Julián Faúndez

Crystals 2025, 15(7), 610; https://doi.org/10.3390/cryst15070610 - 30 Jun 2025

Abstract

We investigate the impact of normal linear strips—both perpendicular and parallel to the direction of vortex motion—on the dynamics of fractional vortices in a two-band superconducting slab. In the absence of pinning, composite vortices dominate throughout the sample, while non-composite (dissociated) vortices appear [...] Read more.

We investigate the impact of normal linear strips—both perpendicular and parallel to the direction of vortex motion—on the dynamics of fractional vortices in a two-band superconducting slab. In the absence of pinning, composite vortices dominate throughout the sample, while non-composite (dissociated) vortices appear only near the vortex entry edge, with energy dissipation primarily governed by the motion of composite structures. To modulate vortex behavior, we introduce linear regions of locally suppressed superconductivity, oriented either perpendicular or parallel to the vortex trajectory. A single perpendicular strip confines fractional vortices to the injection region, whereas two perpendicular strips stabilize composite vortices in the central domain and induce fractional vortex states near the boundaries. In contrast, parallel strips promote the dissociation of vortices across the entire sample, significantly altering the spatial configuration and dynamics of the vortex matter. Furthermore, the interband correlation coefficient serves as a direct indicator of the degree of spatial overlap between vortices in the two condensates. These findings highlight the critical role of pinning geometry in shaping vortex dynamics and energy dissipation, offering new strategies for controlling flux behavior in multiband superconductors for technological applications. Full article

(This article belongs to the Special Issue Superconductivity and Condensed Matter Physics)

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16 pages, 8434 KiB

Open AccessArticle

Micro-Alloying with Samarium to Enhance the Thermal Conductivity and Mechanical Properties of Al-5Ni Cast Alloys

by Yi Huang, Kang Wang, Zhisheng Zhu, Wenxue Cheng and Wenfang Li

Crystals 2025, 15(7), 609; https://doi.org/10.3390/cryst15070609 - 30 Jun 2025

Abstract

The research focuses on how the samarium (Sm) addition amount affects the microstructural development, mechanical characteristics, and thermal conductivity of Al-5wt%Ni alloys. Microstructural characterization revealed that minor Sm additions concurrently refined α-Al grains and eutectic structures (α-Al + Al₃Ni), attributed to [...] Read more.

The research focuses on how the samarium (Sm) addition amount affects the microstructural development, mechanical characteristics, and thermal conductivity of Al-5wt%Ni alloys. Microstructural characterization revealed that minor Sm additions concurrently refined α-Al grains and eutectic structures (α-Al + Al₃Ni), attributed to the reduced initial nucleation temperature of α-Al and an adsorption inhibition effect on Al₃Ni phase formation. The experimental findings revealed that the integration of Sm improved the yield strength, maximum tensile strength, and heat conduction. The enhancements were chiefly driven by three processes: the refinement of grains, the improvement of the eutectic structure’s morphology, and diminishing the dissolvability of Fe/Si impurities within the α-Al matrix. The combined improvement of mechanical and thermal characteristics via regulated Sm addition offers a hopeful approach for the microstructural design of Al-Ni alloys. This study provides a crucial basis for the production of Al-Ni alloys that possess high thermal conductivity and satisfactory mechanical properties. Full article

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

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