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Volume 15
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Crystals, Volume 15, Issue 5 (May 2025) – 53 articles

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16 pages, 886 KiB  
Article
Microstructure Evolution and the Influence on Residual Stress in Metal Additive Manufacturing with Analytics
by Wei Huang, Hamid Garmestani and Steven Y. Liang
Crystals 2025, 15(5), 435; https://doi.org/10.3390/cryst15050435 (registering DOI) - 2 May 2025
Abstract
Additive Manufacturing (AM) has become a revolutionary technology in manufacturing, attracting considerable attention in industrial applications recently. It allows for intricate fabrication, reduces material waste, offers design flexibility, and has economic implications. Nonetheless, the residual stresses generated during the AM process and their [...] Read more.
Additive Manufacturing (AM) has become a revolutionary technology in manufacturing, attracting considerable attention in industrial applications recently. It allows for intricate fabrication, reduces material waste, offers design flexibility, and has economic implications. Nonetheless, the residual stresses generated during the AM process and their effects on microstructural evolution and material properties continue to pose significant challenges hindering its advancement. This paper investigates the evolution of microstructures, focusing on texture and grain size as influenced by processing parameters. It examines how these factors affect the performance of multi-phase materials, specifically in terms of elastic modulus, Poisson’s ratio, and yield strength, leading to variations in residual stress through analytical simulation. The authors developed a thermal model that considers heat transfer boundaries and the geometry of the molten pool. They simulated grain size by considering the heating and cooling processes, including thermal stress, the Johnson-Mehl-Avrami-Kolmogorov (JMAK) model, and grain refinement. The texture was simulated using the Columnar-to-Equiaxed Transition (CET) model, thermal dynamics, and Bunge calculations. The self-consistency model determines the properties based on the established texture distribution. Finally, both microstructure-affected and non-affected residual stresses were modeled and compared. Two gaps between microstructure-affected residual stress and non-affected analytical models appear at the depths of 0.02 mm and 0.078 mm. The results indicate that controlling process parameters and optimizing microstructures can effectively reduce residual stresses, significantly enhancing the overall performance of AM components. Hence, this work provides a more accurate analytical residual stress model and lays the foundation for better control of residual stress in the AM industry. Full article
(This article belongs to the Special Issue Recent Advances in Additive Manufacturing of Metallic Materials: Characterization, Properties, and Modeling)
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18 pages, 12953 KiB  
Article
Microstructural Investigation and High-Temperature Oxidation Performance of K417G Alloy Prepared by Wide-Gap Brazing
by Zhun Cheng, Xin Lai, Jing He, Xiaoqiang Li, Jiafeng Fan and Fuqiang Lai
Crystals 2025, 15(5), 434; https://doi.org/10.3390/cryst15050434 (registering DOI) - 2 May 2025
Abstract
K417G superalloy is widely applied in gas turbine components such as blades, vanes, and nozzles. In this work, the oxidation behavior and mechanism of K417G alloy prepared by wide-gap brazing were investigated in air at 800, 900, 1000, and 1100 °C. Microstructures of [...] Read more.
K417G superalloy is widely applied in gas turbine components such as blades, vanes, and nozzles. In this work, the oxidation behavior and mechanism of K417G alloy prepared by wide-gap brazing were investigated in air at 800, 900, 1000, and 1100 °C. Microstructures of the bonded joints differ in the wide-gap braze region (WGBR) and base metal (BM). The surface and cross-sectional morphology, composition, and structure of specimens were analyzed by XRD, SEM, and EDS after oxidation tests. The experimental data demonstrate that the WGBR‌ (wide-gap brazed region) exhibits markedly superior oxidation resistance compared to the BM‌ (base material) under elevated-temperature conditions exceeding 1000 °C. This performance disparity is quantitatively validated by oxidation kinetics analysis, where the weight gain curve of the WGBR demonstrates parabolic oxidation kinetics, as evidenced by its significantly lower parabolic rate constant relative to the BM. The oxide layers of the BM and WGBR are similar after oxidation at high temperatures of 800–900 °C, and they consist of an outermost layer of NiO, a middle mixed layer of Cr2O3, and an innermost layer of dendritic Al2O3. However, when the temperature is between 1000 and 1100 °C, the NiO on the surface of the BM falls off due to thermal expansion coefficient mismatch in coarse-grained regions, resulting in oxidation mainly divided into outer layer Cr2O3 and inner layer Al2O3 and TiO2. Under high-temperature oxidation conditions (1000–1100 °C), a structural transition occurs in the oxide scale of the BM‌, with the underlying mechanism attributable to grain-coarsening-induced oxide scale destabilization‌. Specifically, the coarse-grained structure of the BM (characteristic grain size exceeding 50 μm) is exhibited. Therefore, the WGBR demonstrates outstanding oxidation resistance, as evidenced by the formation of a continuous Al2O3 scale with parabolic rate constants of about 1.38 × 10−3 mg2·cm−4·min−1 at 1100 °C. Full article
(This article belongs to the Special Issue Microstructure and Mechanical Behaviour of Structural Materials: 2nd Edition)
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9 pages, 804 KiB  
Article
Inelastic Electron Tunneling Spectroscopy of Aryl Alkane Molecular Junction Devices with Graphene Electrodes
by Hyunwook Song
Crystals 2025, 15(5), 433; https://doi.org/10.3390/cryst15050433 (registering DOI) - 1 May 2025
Abstract
We present a comprehensive vibrational spectroscopic analysis of vertical molecular junction devices constructed using single-layer graphene electrodes separated by an aryl alkane monolayer. In this work, inelastic electron tunneling spectroscopy (IETS) is employed to probe molecular vibrations within the junction, providing an in [...] Read more.
We present a comprehensive vibrational spectroscopic analysis of vertical molecular junction devices constructed using single-layer graphene electrodes separated by an aryl alkane monolayer. In this work, inelastic electron tunneling spectroscopy (IETS) is employed to probe molecular vibrations within the junction, providing an in situ fingerprint of the molecules. Graphene has emerged as a promising electrode material for molecular electronics due to its atomically thin, mechanically robust nature and ability to form stable contacts. However, prior to this study, the vibrational spectra of molecules in graphene-based molecular junctions had not been fully explored. Here, we demonstrate that vertically stacked graphene electrodes can be used to form stable and reproducible molecular junctions that yield well-resolved IETS signatures. The observed IETS spectra exhibit distinct peaks corresponding to the vibrational modes of the sandwiched aryl alkane molecules, and all major features are assigned through density functional theory calculations of molecular vibrational modes. Furthermore, by analyzing the broadening of IETS peaks with temperature and AC modulation amplitude, we extract intrinsic vibrational linewidths, confirming that the spectral features originate from the molecular junction itself rather than extrinsic noise or instrumental artifacts. These findings conclusively verify the presence of the molecular layer between graphene electrodes as the charge transport pathway and highlight the potential of graphene–molecule–graphene junctions for fundamental studies in molecular electronics. Full article
(This article belongs to the Special Issue Advances in Multifunctional Materials and Structures)
27 pages, 11438 KiB  
Review
Advances in Activation of Persulfate by Novel Carbon-Based Materials: Degradation of Emerging Contaminants, Mechanisms, and Perspectives
by Lianghui Guo, Dong Liu, Runyao Han, Aoxiang Yin, Guifan Gong, Shi Li, Ruixuan Chen, Jianyu Yang, Zimeng Liu and Keke Zhi
Crystals 2025, 15(5), 432; https://doi.org/10.3390/cryst15050432 (registering DOI) - 1 May 2025
Abstract
Global industrialization has intensified the emission of emerging contaminants (ECs), posing a serious threat to the environment and human health. Persulfate-based advanced oxidation processes (PS-AOPs) have become a research hotspot due to their efficient degradation capability and environmentally friendly features; carbon-based materials are [...] Read more.
Global industrialization has intensified the emission of emerging contaminants (ECs), posing a serious threat to the environment and human health. Persulfate-based advanced oxidation processes (PS-AOPs) have become a research hotspot due to their efficient degradation capability and environmentally friendly features; carbon-based materials are ideal catalysts for activating persulfate (PS) due to their tunable electronic structure, abundant active sites, and low cost. This study summarizes the application of carbon-based materials (graphene, single-atom catalysts (SACs), etc.) in PS-AOPs, and provides insights into the degradation mechanisms of radicals (e.g., sulfate radical (SO4−·), hydroxyl radical (·OH)) and non-radicals (e.g., 1O2(singlet oxygen), electron transfer). The removal efficacy of carbon-based catalysts for antibiotics, phenols, and dyes was compared, and the key degradation pathways were elucidated. In addition, the activation of PS can be accelerated, and catalytic efficiency can be improved by synergizing with ancillary technologies (e.g., light, electricity). Despite the great potential of carbon-based catalysts, their large-scale application is limited by the complexity of the catalyst preparation process and the lack of selectivity for complex water qualities. Future studies can accelerate the practical application of PS-AOPs in wastewater treatment through the precise design of SACs and the construction of multi-mechanism synergistic activation systems. Full article
(This article belongs to the Special Issue Synthesis and Catalytic Performance of Transition Metal Catalysts)
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16 pages, 17834 KiB  
Article
Study on Thermal Deformation Behavior and Thermal Processing Map of a New Al-Li Alloy
by Daoqi Chen, Xinyang Han, Yinggan Zhang, Yan Liu and Junfeng Chen
Crystals 2025, 15(5), 431; https://doi.org/10.3390/cryst15050431 (registering DOI) - 30 Apr 2025
Viewed by 44
Abstract
As a representative third-generation Al-Li alloy, 2A97 alloy has attracted significant attention for applications in aeronautics and astronautics, but its poor hot workability and complex thermal deformation behavior, which make for difficult optimization, significantly limit its widespread industrial utilization. In this study, the [...] Read more.
As a representative third-generation Al-Li alloy, 2A97 alloy has attracted significant attention for applications in aeronautics and astronautics, but its poor hot workability and complex thermal deformation behavior, which make for difficult optimization, significantly limit its widespread industrial utilization. In this study, the thermal deformation behavior of 2A97 Al-Li alloy was systematically investigated via thermal compression tests conducted over a temperature range of 260–460 °C and strain rates ranging from 0.001 s−1 to 1 s−1. The effects of deformation parameters on the alloy’s microstructural evolution were examined using electron backscatter diffraction (EBSD) and transmission electron microscopy (TEM). Based on the dynamic materials model, a constitutive equation was established by analyzing the stress–strain data under various thermal deformation conditions. Furthermore, a thermal processing map was compiled to analyze the effects of the temperature and strain rate on the power dissipation efficiency and flow instability factor. The thermal deformation mechanisms were identified through combined analysis of the thermal processing map and microstructural features. Results indicate that the fraction of low-angle grain boundaries increases with a rising lnZ value (Zener–Hollomon parameter) during the thermal compression process. Dynamic recrystallization is the main deformation mechanism of 2A97 Al-Li alloy in the stable region, whereas the alloy exhibits flow localization in the unstable region. According to the thermal processing map, the optimal hot working windows for the 2A97 Al-Li alloy were determined to be (1) 360–460 °C at strain rates of 0.05 s−1–1 s−1, and (2) 340–420 °C at strain rates of 0.001 s−1–0.005 s−1. These conditions offer favorable combinations of microstructure and deformation stability, providing critical guidance for the thermo-mechanical processing of 2A97 alloy. Full article
(This article belongs to the Special Issue Microstructure and Properties of Metals and Alloys)
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23 pages, 9170 KiB  
Article
Tremolite-Asbestos Presence in Roman Archaeological Site of Micia, Romania
by Rodica-Mariana Ion, Marius Gheorghe Barbu, Valentin Ioan Gurgu, Sofia Slamnoiu-Teodorescu, Anca Irina Gheboianu, Gabriel Vasilievici, Lorena Iancu, Ramona Marina Grigorescu and Elvira Alexandrescu
Crystals 2025, 15(5), 430; https://doi.org/10.3390/cryst15050430 - 30 Apr 2025
Viewed by 58
Abstract
This paper reports the first evidence of the presence of the mineral tremolite asbestos in Roman building materials from the Micia archaeological site (Romania), thus contributing to the understanding of the implications of ancient building materials. The Micia archaeological site includes both a [...] Read more.
This paper reports the first evidence of the presence of the mineral tremolite asbestos in Roman building materials from the Micia archaeological site (Romania), thus contributing to the understanding of the implications of ancient building materials. The Micia archaeological site includes both a fort and a civilian Roman military settlement that was inhabited by both civilians and soldiers from various Roman troops. Over time, since the late 2nd century AD, the settlement has undergone significant reconstruction, especially after some fires. Tremolite asbestos is a non-flammable mineral that, due to its fibrous properties, was used in the past in building materials, although it poses health risks when inhaled. To highlight it, several advanced and highly sensitive scientific techniques are used in this work to discover the presence of tremolite asbestos and to examine its structure, composition, and morphology inside the investigated samples. Tremolite asbestos is typically white to gray or greenish in color, characterized by thin, needle-like fibers that can easily become airborne and inhaled. It is a crystalline mineral that usually forms long, straight, sharp fibers. Under high magnification in optical microscopy or in scanning electron microscope images, correlated with other performant analytical techniques (XRD, WDXRF, FTIR, Raman, BET, TGA), tremolite asbestos appears as elongated, slender fibers—often bundled or intertwined—with smooth or slightly striated surfaces. Full article
(This article belongs to the Section Mineralogical Crystallography and Biomineralization)
21 pages, 13463 KiB  
Article
Anisotropy in the Creep–Fatigue Behaviors of a Directionally Solidified Ni-Based Superalloy: Damage Mechanisms and Life Assessment
by Anping Long, Xiaoshan Liu, Lei Xiao, Gaoxiang Zhang, Jiangying Xiong, Ganjiang Feng, Jianzheng Guo and Rutie Liu
Crystals 2025, 15(5), 429; https://doi.org/10.3390/cryst15050429 - 30 Apr 2025
Viewed by 47
Abstract
Aero-engine turbine vanes made from directionally solidified nickel-based superalloys often fail with crack formation from the external wall of cooling channels. Therefore, this study simulates the compressive load on the external wall of the vane and conducts a sequence of creep–fatigue evaluations at [...] Read more.
Aero-engine turbine vanes made from directionally solidified nickel-based superalloys often fail with crack formation from the external wall of cooling channels. Therefore, this study simulates the compressive load on the external wall of the vane and conducts a sequence of creep–fatigue evaluations at 980 °C to investigate the creep–fatigue damage mechanisms of a directionally solidified superalloy and to assess its life. It is found that at low strain ranges, creep damage is dominant, with creep cavities forming inside the specimen and fatigue sources mostly distributed in the specimen interior. As the strain range increases, the damage mechanism transitions from creep-dominated to creep–fatigue coupled damage, with cracks nucleating preferentially on the surface and exhibiting a characteristic of multiple fatigue sources. In the longitudinal (L) specimen, dislocations in multiple orientations of the {111}<110> slip system are activated simultaneously, interacting within the γ channels to form dislocation networks, and dislocations shear through the γ′ phase via antiphase boundary (APB) pairs. In the transverse (T) specimen, stacking intrinsic stacking faults (SISFs) accumulate within the limited {111}<112> slip systems, subsequently forming a dislocation slip band. The modified creep–fatigue life prediction model, incorporating strain energy dissipation and stress relaxation mechanisms, demonstrates an accurate fatigue life prediction under creep–fatigue coupling, with a prediction accuracy within an error band of 1.86 times. Full article
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17 pages, 20014 KiB  
Article
Molecular Dynamics Study of Nanoscratching Behavior of Water-Film-Covered GaN (0001) Surface Using Spherical Diamond Abrasive
by Jiaqin Yin, Shuaicheng Feng, Yang Liu and Jian Guo
Crystals 2025, 15(5), 428; https://doi.org/10.3390/cryst15050428 - 30 Apr 2025
Viewed by 37
Abstract
Molecular dynamics (MD) simulation of nanoscratching with a spherical diamond abrasive was performed to investigate the role of water molecular film on the surface nanotribological characteristics and subsurface lattice damage of GaN (0001) at the atomic level. The simulation results indicate that the [...] Read more.
Molecular dynamics (MD) simulation of nanoscratching with a spherical diamond abrasive was performed to investigate the role of water molecular film on the surface nanotribological characteristics and subsurface lattice damage of GaN (0001) at the atomic level. The simulation results indicate that the tangential and normal forces exhibited no significant variation trend with the increase in water film thickness. Inducing a water film can alleviate the material pile-up during scratching, and the GaN surface obtained the lowest friction coefficient and wear volume when the water film thickness reached 3 nm, primarily due to the enhanced lubrication and the heat absorption by the water film in this case. Water-film-covered GaN exhibited a thinner subsurface damage layer than the bare GaN, and the damage layer thickness decreased with the increase in water film thickness for various scratching depths of 1 to 4 nm. For each scratching depth, there was an optimal water film thickness causing the minimum number of amorphization atoms. Nevertheless, the water film failed to inhibit the formation and propagation of dislocations in the scratching process, and water-film-covered GaN exhibited more dislocations than the bare one. This research has the potential to expand the comprehension of water-mediated nanotribology and the ultra-precision machining procedures of GaN. Full article
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19 pages, 9508 KiB  
Article
Preparation, Microstructure, and Properties of Solar Energy-Absorbing and -Storing Integrated Forsterite-Based Ceramics
by Xiaohong Xu, Yuntian Li, Tiantian Cheng, Jianfeng Wu, Yaqiang Shen, Saixi Qiu and Jiaqi Yu
Crystals 2025, 15(5), 427; https://doi.org/10.3390/cryst15050427 - 30 Apr 2025
Viewed by 45
Abstract
Solar energy-absorbing and -storing integrated ceramics are a new type of material that absorbs sunlight and stores it as heat energy, with properties such as high absorptivity, high thermal storage density, and high temperature stability. In this study, forsterite ceramics were prepared from [...] Read more.
Solar energy-absorbing and -storing integrated ceramics are a new type of material that absorbs sunlight and stores it as heat energy, with properties such as high absorptivity, high thermal storage density, and high temperature stability. In this study, forsterite ceramics were prepared from fused magnesia, quartz, α-Al2O3, and Sm2O3, and concurrently, two additives of Fe2O3 and CuO were doped to improve the absorptivity, and the effects of the composite additives on the performance of forsterite ceramics were investigated. The results showed that the optimal Fe2O3/CuO content ratio was 8:2, at which time the apparent porosity, bulk density, and thermal storage density of the sample were 0.21%, 3.08 g/cm3, and 1516.71 kJ/kg (1000 °C), respectively. After 30 thermal shock cycles, the precipitation of samarium silicate in the samples resulted in a tighter grain bonding, increased the bending strength by 70.6%, and exhibited excellent thermal shock resistance. The solar absorptivity reached 93.80% in the 0.3–2.5 μm wavelength range. Fe2O3 doping replaced part of the positions of Al3+ in MgAl2O4 to form MgFe0.6Al1.4O4 phase. This replacement caused lattice distortion, which triggered electronic transition and augmented the intrinsic absorption capacity, thereby enhancing the sample’s absorptivity. CuO’s low reflectivity across the spectrum further reduced sample reflectivity. Full article
(This article belongs to the Section Polycrystalline Ceramics)
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16 pages, 13986 KiB  
Article
Orientation-Dependent Nanomechanical Behavior of Pentaerythritol Tetranitrate as Probed by Multiple Nanoindentation Tip Geometries
by Morgan C. Chamberlain, Alexandra C. Burch, Milovan Zečević, Virginia W. Manner, Marc J. Cawkwell and David F. Bahr
Crystals 2025, 15(5), 426; https://doi.org/10.3390/cryst15050426 - 30 Apr 2025
Viewed by 64
Abstract
Nanoindentation can be leveraged to aid in the high fidelity modeling of dislocation mediated plasticity in pentaerythritol tetranitrate (PETN), an anisotropic energetic molecular crystal. Moreover, nanoindentation tip parameters such as tip geometry, size, and degree of acuity can be utilized to target anisotropic [...] Read more.
Nanoindentation can be leveraged to aid in the high fidelity modeling of dislocation mediated plasticity in pentaerythritol tetranitrate (PETN), an anisotropic energetic molecular crystal. Moreover, nanoindentation tip parameters such as tip geometry, size, and degree of acuity can be utilized to target anisotropic behavior. In this work, nanoindentation was conducted across a range of orientations on the (110) face of PETN to characterize resultant yield behavior, mechanical property measurements, and resultant slip behavior and fracture initiation. Three different indentation tips were utilized: a 3-sided pyramidal Berkovich tip, a 4-sided high aspect ratio Knoop tip, and a 90° conical tip. Ultimately, indenter tip radius was documented to impact yield behavior, whereas tip geometry affected larger scale processes such as slip, and tip acuity was the dominating factor that led to fracture. The axisymmetric conical tip, serving as a baseline, showed the least amount of variation in mechanical property measurements but also the largest distribution of maximum shear stress at which initial yielding occurred. Its high degree of acuity, however, was more prone to induce fracture at higher loads. The Knoop tip was shown to be suitable for average measurements, but also for elucidation of certain anisotropic features. A distinctly higher perceived hardness at 45° was measured with the Knoop tip, indicating less dislocation motion in that direction also observed in this work via scanning probe microscopy. Lastly, the commonly used Berkovich tip was a good compromise whereby it provided a representative volume element describing the average behavior of the material. These results can be utilized to target desired anisotropic behavior in a wider range of molecular crystals, as well as to inform theoretical considerations for dislocation mediated plasticity in PETN. Full article
(This article belongs to the Special Issue Microstructure and Characterization of Crystalline Materials)
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17 pages, 8251 KiB  
Article
The Electrochemical Characteristics and Corrosion Resistance of a Low-Melting-Point Al49Sn21Zn16Pb14 Alloy in NaCl Solution
by Xiaofei Yao, Weihua Wang, Xiaoling Qi, Yunkun Lv, Wei Yang, Yufei Ma and Jian Chen
Crystals 2025, 15(5), 425; https://doi.org/10.3390/cryst15050425 - 30 Apr 2025
Viewed by 50
Abstract
In this study, we prepared an innovative corrosion-resistant and low-melting-point Al49Sn21Zn16Pb14 alloy, and its microstructure was characterized. The corrosion resistance of the Al49Sn21Zn16Pb14 alloy in a NaCl solution with different concentrations was tested via electrochemical and immersion methods. In addition, the corrosion morphologies [...] Read more.
In this study, we prepared an innovative corrosion-resistant and low-melting-point Al49Sn21Zn16Pb14 alloy, and its microstructure was characterized. The corrosion resistance of the Al49Sn21Zn16Pb14 alloy in a NaCl solution with different concentrations was tested via electrochemical and immersion methods. In addition, the corrosion morphologies and products were analyzed via scanning electron microscopy (SEM), energy dispersive spectrometry (EDS), and X-ray diffraction (XRD), and the effects of the NaCl solution’s concentration on the corrosion resistance of the Al49Sn21Zn16Pb14 alloy were studied. The results showed that the melting point of the Al49Sn21Zn16Pb14 alloy was only 356.8 °C, and the melting temperature range was 356.8–377.6 °C. The microstructure of the Al49Sn21Zn16Pb14 alloy was dendritic, eutectic, and peritectic, and it had a face-centered cube (FCC) composition in the solid solution phase. The dendrite structure comprised an Al-rich solid solution primarily in the interdendrites and a Zn-rich solid solution mostly in the dendrites; the eutectic structure mainly consisted of Sn- and Pb-rich solid solutions; and the peritectic structure mainly comprised Zn- and Sn-rich solid solutions. In NaCl solutions of different concentrations, the Al49Sn21Zn16Pb14 alloy is generally corrosive; the corrosion rate of the Al49Sn21Zn16Pb14 alloy in 3.5% NaCl solution was 1.97 × 10−2 mm/a; and the corrosion surface was loose or cracking. The corrosion products attached to the corrosion surface of the alloys mainly comprised Al and Zn oxides, while Sn and Pb corroded to form Sn and Pb oxides, which dissolved or fell off to form microholes or pores on the corrosion surface of the Al49Sn21Zn16Pb14 alloy. With an increase in the NaCl solution’s concentration, the degree of corrosion products that fell off or dissolved increased, and thus, the Al49Sn21Zn16Pb14 alloy’s corrosion rate increased. In 10.5% and 14% NaCl solutions, the amount of Al oxides in the corrosion products increased, and the locally dense corrosion product that formed on the corrosion surface of the Al49Sn21Zn16Pb14 alloy cracked and could not protect the matrix. The locally dense corrosion products on the surface of the Al49Sn21Zn16Pb14 alloy in NaCl solutions therefore could not improve the corrosion resistance. Full article
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18 pages, 29402 KiB  
Article
Relationship Between Structure and Functional Properties of Ultrafine-Grained Fe-Mn-Si Alloys for Temporary Implants
by Olga Rybalchenko, Natalia Martynenko, Natalia Anisimova, Georgy Rybalchenko, Natalia Tabachkova, Elena Lukyanova, Igor Shchetinin, Diana Temralieva, Alexey Tokar, Petr Straumal, Pavel Dolzhenko, Andrey Belyakov, Mikhail Kiselevskiy and Sergey Dobatkin
Crystals 2025, 15(5), 424; https://doi.org/10.3390/cryst15050424 - 30 Apr 2025
Viewed by 54
Abstract
This paper presents a study of microstructure formation in bioresorbable Fe-Mn-Si alloys for temporary implants under high-pressure torsion (HPT) at room temperature and at 300 °C. The effect of silicon on the mechanism of microstructure formation under HPT and, as a consequence, on [...] Read more.
This paper presents a study of microstructure formation in bioresorbable Fe-Mn-Si alloys for temporary implants under high-pressure torsion (HPT) at room temperature and at 300 °C. The effect of silicon on the mechanism of microstructure formation under HPT and, as a consequence, on the mechanical, corrosion and biological properties of the alloys is studied. It is established that Si promotes martensitic transformation. HPT leads to an increase in the microhardness values of the studied alloys from ~1560 MPa in the initial state to ~5500 MPa (160–560 HV) due to structure refinement and phase transformation. An increase in the electrochemical corrosion rate of Fe-Mn-Si alloys to ~0.5 mm/year is established due to grain refinement to nanosize and the formation of strain-induced martensite. In vitro cytotoxicity and induced hemolysis studies showed that Fe-Mn, Fe-Mn-3.7Si, and Fe-Mn-5Si alloys after annealing and HPT can be characterized as biocompatible. Full article
(This article belongs to the Special Issue Crystal Plasticity (4th Edition))
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12 pages, 1608 KiB  
Article
Sm3+-Doped Bismuth(III) Oxosilicate (Bi4Si3O12:Sm3+): A Study of Crystal Structure and Mulliken Charges
by Yan Zhang, Xuefeng Xiao, Yan Huang, Jiashun Si, Shuaijie Liang, Qingyan Xu, Huan Zhang, Lingling Ma, Cui Yang, Tianyong Ma, Xuefeng Zhang, Jiayue Xu, Tian Tian and Hui Shen
Crystals 2025, 15(5), 423; https://doi.org/10.3390/cryst15050423 - 30 Apr 2025
Viewed by 49
Abstract
In this paper, using the Materials Studio software (version 2020) and based on first-principles and density functional theory, the effects of Sm3+ doping at different ratios (1/12, 1/6, and 1/3) on the crystal structure and Mulliken charge distribution of bismuth silicate (Bi [...] Read more.
In this paper, using the Materials Studio software (version 2020) and based on first-principles and density functional theory, the effects of Sm3+ doping at different ratios (1/12, 1/6, and 1/3) on the crystal structure and Mulliken charge distribution of bismuth silicate (Bi4Si3O12, BSO) were analyzed. The examination of the crystal framework and Mulliken charge allocation reveals that increasing levels of Sm3+ doping have the potential to warp the lattice’s symmetry and result in a decrease in electrical conductivity. With the rise in the concentration of Sm3+ doping, the Sm-O bond length shows a pattern of a rise at first and then a fall, demonstrating that electrons are shared, and reaches its minimum length with a doping proportion of 1/12. At the same time, when the doping concentration of Sm3+ rises, the Bi-O bond length becomes longer; it reaches its shortest length when the doping concentration is 1/12. This finding suggests that when a small quantity of Sm3+ is doped, especially when the doping concentration is 1/12, the covalent nature of the bonds between Sm-O and Bi-O atoms within the BSO crystal is strengthened. Full article
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19 pages, 18440 KiB  
Article
Rotating Bending Fatigue Behavior of AlSi10Mg Fabricated by Powder Bed Fusion-Laser Beam: Effect of Layer Thickness
by Lu Liu, Shengnan Wang and Yifan Ma
Crystals 2025, 15(5), 422; https://doi.org/10.3390/cryst15050422 - 30 Apr 2025
Viewed by 160
Abstract
A single batch of AlSi10Mg powder was used to fabricate two groups of round bars via horizontal printing, employing an identical strategy except for one parameter in the process of powder bed fusion-laser beam. The parameter is layer thickness, set at 50 and [...] Read more.
A single batch of AlSi10Mg powder was used to fabricate two groups of round bars via horizontal printing, employing an identical strategy except for one parameter in the process of powder bed fusion-laser beam. The parameter is layer thickness, set at 50 and 80 μm for Group-1 and Group-2, respectively, resulting in laser energy densities of 29.95 and 18.72 J/mm3. Both materials exhibit similar microstructures; Group-1 has fewer and smaller defects than Group-2, leading to higher strength and ductility. Fatigue performance of low-cycle and long-life up to 108 cycles under rotating bending was assessed, and the fracture surfaces were carefully examined under scanning electron microscopy. The S-N data converge to a single slope followed by a horizontal asymptote, indicating the occurrence of very-high-cycle fatigue (VHCF) in both cases. Group-1 shows higher fatigue strength in the range of 104 to 108 cycles, and a greater failure probability in VHCF regime than Group-2. This is attributed to the larger defect size in Group-2, where the smaller control volume in rotating bending greatly increases the likelihood of encountering large defects compared to Group-1. At the defect edge, the microstructure shows distinct resistance to crack propagation under high and low loads. Full article
(This article belongs to the Special Issue Fatigue and Fracture of Crystalline Metal Structures)
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24 pages, 3834 KiB  
Article
Energy and Resource Efficient Continuous Cooling Crystallization with Modular Lab-Scale Equipment
by Norbert Kockmann, Mira Schmalenberg, Benedikt Strakeljahn and Kerstin Wohlgemuth
Crystals 2025, 15(5), 421; https://doi.org/10.3390/cryst15050421 - 29 Apr 2025
Viewed by 132
Abstract
Small-scale modular apparatuses in continuously operated plants are promising for current and future production processes in fine and specialty chemistry. Different lab-scale crystallizers have been developed and characterized as part of the ENPRO-TeiA project—separation processes with efficient and intelligent apparatuses. Two research groups [...] Read more.
Small-scale modular apparatuses in continuously operated plants are promising for current and future production processes in fine and specialty chemistry. Different lab-scale crystallizers have been developed and characterized as part of the ENPRO-TeiA project—separation processes with efficient and intelligent apparatuses. Two research groups at TU Dortmund University have investigated four miniaturized crystallization apparatuses for cooling crystallization and characterized them for scaling up to pilot scale with industrial partners. The use in an industrial environment was successfully demonstrated for two types of crystallizers: the stirred tank cascade as well as a draft tube baffle crystallizer. The ENPRO-TeiA project was thus able to prototypically demonstrate the manufacturer-independent investigation and scaling of modular systems for the crystallization step, which is an essential cornerstone for the process development acceleration for sustainable production in the pharmaceutical and chemical industries. Full article
(This article belongs to the Special Issue Crystallisation Advances)
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10 pages, 2934 KiB  
Article
Ion Substitution Behavior and Chromatographic Study of “Ya’an Green” Seal Stone
by Yicong Sun, Yigeng Wang, Zixuan Wang, Zheng Zhang, Mingming Xie, Zhuchun Peng, Bin Meng, Siqi Yang and Endong Zu
Crystals 2025, 15(5), 420; https://doi.org/10.3390/cryst15050420 - 29 Apr 2025
Viewed by 99
Abstract
In recent years, domestic research on the ion substitution behavior and chromaticity of the mineral composition of “Ya’an Green” remains insufficient, while there is almost no relevant research on “Ya’an Green” abroad. In this study, X-ray powder diffraction (XRD), electron probe microanalysis (EPMA), [...] Read more.
In recent years, domestic research on the ion substitution behavior and chromaticity of the mineral composition of “Ya’an Green” remains insufficient, while there is almost no relevant research on “Ya’an Green” abroad. In this study, X-ray powder diffraction (XRD), electron probe microanalysis (EPMA), infrared spectroscopy (IR), ultraviolet–visible spectroscopy (UV-Vis), and colorimetry were employed. The results indicate that the green and yellow matrices of “Ya’an Green” are primarily composed of muscovite, with rutile also present in the yellow matrix. In contrast, the white–green samples are mainly composed of quartz, with muscovite as a secondary mineral. Additionally, it was observed that the (004) crystal plane of muscovite exhibits a peak shift to lower 2θ angles, attributed to the substitution of Al3+ by ions with larger radii, such as Ba2+, Cr3+, and Fe2+, leading to an increase in unit cell parameters and a consequent shift in the peak to lower wavenumbers. The main elements of “Ya’an Green” are Al, Si, and K, with minor elements including Na, Fe, and Cr. Furthermore, Mg2+, Ca2+, Ti4+, Cr3+, and Fe2+ in the samples can substitute for Al3+ through isomorphic substitution. The infrared spectrum of muscovite in the ‘Ya’an Green’ sample shows three typical absorption peaks, 422 cm−1 and 513 cm−1 caused by Si-O bending vibration, 697 cm−1 and 837 cm−1 caused by Si-O-Al vibration, 948 cm−1 caused by O-H bending vibration, and 3647 cm−1 caused by O-H stretching vibration. The peak at 837 cm−1 exhibits varying degrees of shift due to the substitution of Al3+ by ions with larger radii. The ultraviolet–visible spectra display two broad absorption bands at 422 nm and 615 nm, which are caused by Cr3+ transition, indicating that Cr is the chromogenic element responsible for the green color. A correlation was observed between the Cr3+ content and the hue angle h in “Ya’an Green” samples: the higher the Cr3+ content, the closer the hue angle is to 136°, resulting in a darker green color, while lower Cr3+ content leads to a deviation from the dark green hue. This study establishes for the first time the correlation between the mineral composition of ‘Ya’an Green’ and its chromatic parameters and explores the linear relationship between its color and the number of color-causing elements and elemental substitution, which provide data support and theoretical models for the study of the color of seal stones. Full article
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14 pages, 3355 KiB  
Article
Evolution of Microstructure, Tensile Mechanical and Corrosion Properties of a Novel Designed TRIP-Aided Economical 19Cr Duplex Stainless Steel After Aging Treatment
by Xi Shi, Shan Liu, Shuaiwei Chen, Qingxuan Ran, Bo Liang and Xiaoliang Yan
Crystals 2025, 15(5), 419; https://doi.org/10.3390/cryst15050419 - 29 Apr 2025
Viewed by 65
Abstract
In this experiment, a novel designed Mn-N-bearing, nearly Ni-free, TRIP-aided economical 19Cr (Fe-18.9Cr-10.1Mn-0.3Ni-0.26N-0.03C) duplex stainless steel (DSS) was prepared, and it exhibited a good combination of strength and toughness after suitable solution treatment, showing good application potential. The deformation mechanisms of ferrite and [...] Read more.
In this experiment, a novel designed Mn-N-bearing, nearly Ni-free, TRIP-aided economical 19Cr (Fe-18.9Cr-10.1Mn-0.3Ni-0.26N-0.03C) duplex stainless steel (DSS) was prepared, and it exhibited a good combination of strength and toughness after suitable solution treatment, showing good application potential. The deformation mechanisms of ferrite and austenite are different during tensile deformation at room temperature: the ferrite phase was deformed by a dislocation slip mechanism and formed a cell structure due to its higher stacking fault energy; the lower stacking fault energy of austenite resulted in a strain-induced martensite phase transformation mechanism. With an increase in aging time from 1 h to 7 h at 750 ℃ in air, the σ phase precipitates in the ferrite triple grain boundary junction, which leads to an increase in ultimate tensile strength, acts as an obstacle to the dislocation motion and decreases the ductility, deteriorating the pitting corrosion resistance in 3.5 wt.% NaCl solution at the same time. The σ phase precipitation behavior does not alter the deformation mechanism of the phases of the solution-treated TRIP-aided economical DSS. Full article
(This article belongs to the Special Issue Microstructure and Properties of Steels and Other Structural Alloys, Second Edition)
24 pages, 3643 KiB  
Article
Geometrical Similarities Between Metallic Real and Computationally Simulated Grain Structures (Equiaxed Polygonal Grains)
by Adán Ramírez-López, Juan Alberto Alcántara-Cárdenas, Ángel de Jesús Morales-Ramírez and Juliana Guadalupe Rosado-Carrasco
Crystals 2025, 15(5), 418; https://doi.org/10.3390/cryst15050418 - 29 Apr 2025
Viewed by 86
Abstract
Metallic materials are formed with grain structures which are naturally formed during solidification or modified after any manufacturing process, such as rolling, cutting, machining, welding, etc. Grains with different sizes and geometrical morphologies have a strong influence on the micro- and macro properties [...] Read more.
Metallic materials are formed with grain structures which are naturally formed during solidification or modified after any manufacturing process, such as rolling, cutting, machining, welding, etc. Grains with different sizes and geometrical morphologies have a strong influence on the micro- and macro properties of metallic materials. This is the reason why many authors have worked on computer simulations based on numerical methods, applying chaos theory and using graphical techniques for its reproduction. Thus, this manuscript is focused on the comparison between grain structures obtained computationally with grains in real metallic samples. The analyzed structures in this work were polygonal and equiaxed, they resulted from a dynamic evolution in which nucleation and growth procedures were simulated. Then, computational algorithms and standardized procedures were used for characterization. Thus, in order to demonstrate the geometrical similarities and differences in mathematical terms, similarities between sample features were calculated, measuring sizes and populations along different directions which could be used to establish rules and parameters for the appropriate control of nucleation and growth. Furthermore, the influence of the computational methods for simulation and characterization are also described in detail. Full article
(This article belongs to the Section Crystal Engineering)
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16 pages, 9915 KiB  
Article
Role of Oxygen Concentration in Reactive Sputtering of RuO2 Thin Films: Tuning Surface Chemistry for Enhanced Electrocatalytic Performance
by Swapnil Nalawade, Ebenezer Vondee, Mengxin Liu, Ikenna Chris-Okoro, Sheilah Cherono, Dhananjay Kumar and Shyam Aravamudhan
Crystals 2025, 15(5), 417; https://doi.org/10.3390/cryst15050417 - 29 Apr 2025
Viewed by 187
Abstract
Developing active electrocatalysts for water splitting is a great challenge due to slow four-electron transfer oxygen evolution reaction. Here, we report the effect of variable oxygen concentrations in sputtered RuO2 thin films on electrochemical performance. The impact of Ar/O2 ratios on [...] Read more.
Developing active electrocatalysts for water splitting is a great challenge due to slow four-electron transfer oxygen evolution reaction. Here, we report the effect of variable oxygen concentrations in sputtered RuO2 thin films on electrochemical performance. The impact of Ar/O2 ratios on the structural, chemical, and optical properties of sputtered RuO2 films is systematically investigated. The as-deposited amorphous RuO2 showed higher catalytic activity as compared to its annealed crystalline counterparts. The X-ray photoelectron spectroscopy results showed controlled stoichiometry with 20% oxygen. The electrochemical measurements of the RuO2 deposited with a 4:1 Ar:O2 ratio showed superior performance in cyclic voltammetry, linear sweep voltammetry, and Tafel slope. Transformation of as-deposited amorphous RuO2 into polycrystalline films is observed at 400 °C of annealing temperature. Film thickness is increased with increasing O2 concentration during deposition. This study highlights that sputtered RuO2 thin films with varying oxygen concentration during deposition can influence the electrocatalytic activities in water-splitting applications. Full article
(This article belongs to the Special Issue Advanced Materials for Applications in Water Splitting)
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15 pages, 3855 KiB  
Article
Thermocapillary Flow in Fluid Smectic Bubbles in Microgravity
by Eric Minor, Ravin Chowdhury, Cheol S. Park, Joseph E. Maclennan and Noel A. Clark
Crystals 2025, 15(5), 416; https://doi.org/10.3390/cryst15050416 - 29 Apr 2025
Viewed by 147
Abstract
Interfaces between two fluids exhibit an excess free-energy cost per unit area that is manifested as surface tension. This equilibrium property generally depends on temperature, which enables the phenomenon of thermocapillary flow, wherein application of a temperature gradient having a component parallel to [...] Read more.
Interfaces between two fluids exhibit an excess free-energy cost per unit area that is manifested as surface tension. This equilibrium property generally depends on temperature, which enables the phenomenon of thermocapillary flow, wherein application of a temperature gradient having a component parallel to the surface generates a net in-plane effective body force on the fluid and thereby causes flow. Here, we study the thermocapillary flow in fluid smectic liquid crystal films freely suspended in air and stabilized in thickness by the smectic layering. If such films are a single layer (~3 nm) or a few layers thick, they have the largest surface to volume ratio of any fluid preparation, making them particularly interesting in the context of thermocapillary flow, which is two-dimensional (2D) in the film plane. Five-layer thick films in the form of spherical bubbles were subjected to a north–south temperature gradient field along a polar axis, with flow fields mapped using inclusions on the film surface as tracers, where the inclusions were “islands”, small circular stacks of extra layers. These experiments were carried out on the International Space Station to avoid interference from thermal convention of the air. The flow field as a function of latitude on the bubble can be successfully modeled using Navier–Stokes hydrodynamics, modified to include permeative flow out of the background fluid into the islands. Full article
(This article belongs to the Section Liquid Crystals)
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15 pages, 2675 KiB  
Article
Crystal Chemistry and Genetic Implications of Pink Tourmalines from Distinct Pegmatite Provinces
by Floriana Rizzo, Ferdinando Bosi, Gioacchino Tempesta, Federica Iommazzo and Giovanna Agrosì
Crystals 2025, 15(5), 415; https://doi.org/10.3390/cryst15050415 - 28 Apr 2025
Viewed by 115
Abstract
Borosilicate minerals of the tourmaline supergroup are valuable both for collectors and for geological research, as their chemical composition reflects the growth-medium conditions and their evolution. Tourmalines show a wide compositional variability, with pink tourmalines being particularly prized as gemstones. This study examines [...] Read more.
Borosilicate minerals of the tourmaline supergroup are valuable both for collectors and for geological research, as their chemical composition reflects the growth-medium conditions and their evolution. Tourmalines show a wide compositional variability, with pink tourmalines being particularly prized as gemstones. This study examines the crystal chemistry of pink tourmalines from Cruzeiro (Brazil), Nuristan (Afghanistan), and Malkhan (Russia) using Electron Microprobe Analysis, Micro Laser Induced Breakdown Spectroscopy (LIBS), and Single Crystal X-ray Diffraction. The results show that the pink tourmalines are Mn-rich elbaite, with the pink coloration linked to Mn at the Y site, indicating crystallization from Mn-rich pegmatitic fluids. LIBS spectra suggest a Li-rich pegmatite origin. The samples show differences: Cruzeiro exhibits strong chemical zoning, Nuristan has a uniform composition, and Malkhan shows slight zoning with high F content. A comparison with a pink tourmaline from Anjanabonoina (Madagascar) reveals that it is Ca-rich, belonging to the calcic group and crystallizing in an open system influenced by external Ca-rich fluids, contrasting with the closed system of the samples from Cruzeiro and Nuristan. The sample from Malkhan shows an anomalous chemical variation of Ca and requires further investigation. Full article
(This article belongs to the Section Mineralogical Crystallography and Biomineralization)
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10 pages, 6733 KiB  
Article
Delicate Competition Between Different Excitonic Orderings in Ta2NiSe5
by Banhi Chatterjee, Denis Golež and Jernej Mravlje
Crystals 2025, 15(5), 414; https://doi.org/10.3390/cryst15050414 - 28 Apr 2025
Viewed by 125
Abstract
We investigate the energetics of the quasi-one-dimensional layered compound Ta2NiSe5 in the excitonic phase within the six-band model using Hartree–Fock calculations. We calculate energies of states with different kinds of excitonic order and show that they differ by less than [...] Read more.
We investigate the energetics of the quasi-one-dimensional layered compound Ta2NiSe5 in the excitonic phase within the six-band model using Hartree–Fock calculations. We calculate energies of states with different kinds of excitonic order and show that they differ by less than meV and depend sensitively on precise values of interchain hopping matrix elements. Full article
(This article belongs to the Special Issue State of Art of Excitonic Insulators and Topological Materials)
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35 pages, 18223 KiB  
Article
Impact of Inter-Modular Connections on Progressive Compressive Behavior of Prefabricated Column-Supported Volumetric Modular Steel Frames
by Kejia Yang, Kashan Khan, Yukun Yang, Lu Jiang and Zhihua Chen
Crystals 2025, 15(5), 413; https://doi.org/10.3390/cryst15050413 - 28 Apr 2025
Viewed by 113
Abstract
This study investigates the progressive compressive behavior of modular interior frames with rotary-type module-to-module inter-modular (M2M) connections under sequential column failure. A novel two-stage testing protocol was applied, compressing the left upper column to failure, followed by the right, to simulate realistic loading [...] Read more.
This study investigates the progressive compressive behavior of modular interior frames with rotary-type module-to-module inter-modular (M2M) connections under sequential column failure. A novel two-stage testing protocol was applied, compressing the left upper column to failure, followed by the right, to simulate realistic loading progression in prefabricated column-supported volumetric modular steel structures. Detailed refined finite-element models (FEMs) were developed and validated against experimental results, accurately capturing local and global responses with an average prediction error of 2–10% for strength and stiffness. An extensive parametric study involving varying frame configurations evaluated the influence of frame member geometric properties, connection details, and column/beam gap interaction on progressive collapse behavior. The results demonstrated that upper columns govern failure through elastic–plastic buckling near M2M joints while other members/connections remain elastic/unyielded. Increasing column cross section and thickness significantly enhanced strength and stiffness, while longer columns and prior damage reduced capacity, particularly during right-column loading. Conventional steel design codes overestimated column strength, with mean Pu,FEM/Pu,code ratios below unity and high scatter (Coefficient of variation ~0.25–0.27), highlighting the inadequacy of isolated member-based design equations for modular assemblies. The findings emphasize the need for frame-based stability approaches that account for M2M joint semi-rigidity, sway sensitivity, and sequential failure effects to ensure the reliable design of modular steel frames under progressive compressive loads. Full article
(This article belongs to the Special Issue Advances in High Performance Metal Materials: Preparation, Properties, and Applications)
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20 pages, 2259 KiB  
Article
Temperature-Controlled Defective Phononic Crystals with Shape Memory Alloys for Tunable Ultrasonic Sensors
by Soo-Ho Jo
Crystals 2025, 15(5), 412; https://doi.org/10.3390/cryst15050412 - 28 Apr 2025
Viewed by 156
Abstract
Phononic crystals (PnCs) have garnered significant interest owing to their ability to manipulate wave propagation, particularly through phononic band gaps and defect modes. However, conventional defective PnCs are limited by their fixed defect-band frequencies, which restricts their adaptability to dynamic environments. This study [...] Read more.
Phononic crystals (PnCs) have garnered significant interest owing to their ability to manipulate wave propagation, particularly through phononic band gaps and defect modes. However, conventional defective PnCs are limited by their fixed defect-band frequencies, which restricts their adaptability to dynamic environments. This study introduces a novel approach for temperature-controlled tunability of defective PnCs by integrating shape memory alloys (SMAs) into defect regions. The reversible phase transformations of SMAs, driven by temperature variations, induce significant changes in their mechanical properties, enabling real-time adjustment of defect-band frequencies. An analytical model is developed to predict the relationship between the temperature-modulated material properties and defect-band shifts, which is validated through numerical simulations. The results demonstrate that defect-band frequencies can be dynamically controlled within a specified range, thereby enhancing the operational bandwidth of the ultrasonic sensors. Additionally, sensing-performance analysis confirms that while defect-band frequencies shift with temperature, the output voltage of the sensors remains stable, ensuring reliable sensitivity across varying conditions. This study represents a significant advancement in tunable PnC technology, paving the way for next-generation ultrasonic sensors with enhanced adaptability and reliability in complex environments. Full article
(This article belongs to the Special Issue Research and Applications of Acoustic Metamaterials)
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15 pages, 20924 KiB  
Article
The Effect of Nb Addition on the Microstructural Evolution and Mechanical Properties of 50W–Ni–Fe Alloy
by Tianhao Wu, Wensheng Liu, Yunzhu Ma, Youteng Duan, Yifan Han, Ziqi Meng and Qingshan Cai
Crystals 2025, 15(5), 411; https://doi.org/10.3390/cryst15050411 - 28 Apr 2025
Viewed by 124
Abstract
Optimizing the design of low-tungsten-content alloys represents an effective approach to address the insufficient strength and toughness of conventional tungsten alloys. This study focuses on the design and fabrication of low-tungsten-content alloys, specifically investigating the effects of Nb addition on the low-temperature sintering [...] Read more.
Optimizing the design of low-tungsten-content alloys represents an effective approach to address the insufficient strength and toughness of conventional tungsten alloys. This study focuses on the design and fabrication of low-tungsten-content alloys, specifically investigating the effects of Nb addition on the low-temperature sintering microstructure and mechanical properties of 50W–Ni–Fe alloy. The results demonstrate that Nb significantly lowers the liquid phase formation temperature, shifting the densification mechanism from solid phase sintering to liquid phase sintering. Nb primarily dissolves in the γ-(Ni,Fe) matrix phase and forms nanoscale γ″-Ni3Nb precipitates. These γ″-Ni3Nb precipitates maintain coherent interfaces with the γ-(Ni,Fe) matrix phase, exhibiting excellent interfacial bonding, which markedly enhances the hardness and modulus of the matrix phase. Through the strengthening effects of solid solution strengthening and precipitation strengthening, the tensile strength of the alloy increases to 1259 MPa while maintaining a total elongation of 23.1%. The fracture mode of the 50W-Ni-Fe-Nb alloy transitions to a mixed mechanism involving cleavage fracture of W and ductile rupture of the matrix phase. Full article
(This article belongs to the Special Issue Design, Microstructure and Mechanical Properties of Cu-Based Alloys)
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17 pages, 2692 KiB  
Article
A First-Principles Study of Sn Dimer Adsorbed on MgO Surface
by Piotr Matczak
Crystals 2025, 15(5), 410; https://doi.org/10.3390/cryst15050410 - 28 Apr 2025
Viewed by 149
Abstract
A detailed characterization of metal clusters bound at the surface of crystalline metal oxide supports is crucial for identifying their structure–property relationships relevant to practical applications. Theoretical investigations based on first-principles calculations have proven to be helpful in characterizing supported metal clusters. In [...] Read more.
A detailed characterization of metal clusters bound at the surface of crystalline metal oxide supports is crucial for identifying their structure–property relationships relevant to practical applications. Theoretical investigations based on first-principles calculations have proven to be helpful in characterizing supported metal clusters. In this work, the adsorption of an Sn dimer on the regular and defective (100) surfaces of MgO crystal was studied by means of density functional theory (DFT) calculations. The investigated defects included Fs0, Fs+, and Fs2+ oxygen vacancies on MgO(100). From the results of the calculations, it is clear that the adsorption of Sn2 at the Fs0 and Fs+ centers is stronger than that occurring on the defect-free MgO(100) surface. While the triplet spin multiplicity of a free Sn dimer tends to be preserved upon its adsorption at the Fs2+ center, spin quenching is favored for the dimer adsorbed at the regular O2− and defective Fs0 and Fs+ centers. The topological analysis of the electron density for the adsorbed dimer was carried out within the quantum theory of atoms in molecules (QTAIM). The calculated values of QTAIM parameters for the Sn-Sn bond of the adsorbed dimer do not differ radically from the corresponding values for the dimer in the gas phase. Full article
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11 pages, 1890 KiB  
Article
First-Principles Study on the Migration and Release Properties of Xe on the Surface of Uranium Mononitride
by Tianhao Rui, Yulin Lan, Zhuangzhuang Ma, Linyuan Lu, Yunhao Wang, Yang Yu, Mingxuan Deng, Tianxing Lan, Zhekang Zhao, Junjie Wang, Congyi Li and Haibin Zhang
Crystals 2025, 15(5), 409; https://doi.org/10.3390/cryst15050409 - 27 Apr 2025
Viewed by 148
Abstract
The fission gas uranium mononitride (UN) causes swelling and affects the properties of fission fuel. Since surface behavior is closely related to the release of gases, it is crucial to study the properties of Xe on the UN surface. Density functional theory was [...] Read more.
The fission gas uranium mononitride (UN) causes swelling and affects the properties of fission fuel. Since surface behavior is closely related to the release of gases, it is crucial to study the properties of Xe on the UN surface. Density functional theory was used to study the properties of Xe gas on the UN(001) surface and subsurface layers. Different bulk and surface models of UN were established, and the formation energies of bulk and surface defects, as well as the incorporation energy of surface Xe, were calculated. Differential charge density maps were generated, and the analysis revealed that the migration of Xe atoms on the surface predominantly occurs through a vacancy mechanism. Furthermore, Xe atoms located in the subsurface and interstitial positions are less likely to escape from the surface due to the influence of surrounding atoms. Finally, the Climbing Image Nudged Elastic Band method was employed to calculate migration pathways and the associated migration energies. The modelling results indicated that surface Xe atoms’ migration exhibits a vacancy-assisted mechanism, while surface and subsurface U-vacancies on the UN surface may promote the diffusion of fission gas atoms. Full article
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22 pages, 1675 KiB  
Review
Plasma Spraying of W Coatings for Nuclear Fusion Applications: Advancements and Challenges
by Ekaterina Pakhomova, Alessandra Palombi and Alessandra Varone
Crystals 2025, 15(5), 408; https://doi.org/10.3390/cryst15050408 - 26 Apr 2025
Viewed by 234
Abstract
The selection of a suitable plasma-facing material (PFM) that must protect the divertor, cooling systems, and structural components is an important challenge in the design of advanced fusion reactors and requires careful consideration. Material degradation due to melting and evaporation may lead to [...] Read more.
The selection of a suitable plasma-facing material (PFM) that must protect the divertor, cooling systems, and structural components is an important challenge in the design of advanced fusion reactors and requires careful consideration. Material degradation due to melting and evaporation may lead to plasma contamination, which must be strictly avoided. Among the candidate materials, tungsten (W) is the most promising because of its thermo-mechanical and physical properties, which allow it to endure repeated exposure to extremely harsh conditions within the reactor. The plasma spraying (PS) technique is gaining increasing interest for the deposition of tungsten (W) coatings to protect heat sink materials, due to its relatively low cost, high deposition rates, and capability to coat complex-shaped surfaces and fix damaged coatings in situ. This review aims to provide a systematic assessment of tungsten (W) coatings produced by PS techniques, evaluating their suitability as PFMs. It discusses W-based materials, plasma spraying technologies, the role of the interface in joining W coating and metallic substrates such as copper alloys and steels, and the main issues related to coating surface erosion under steady-state and transient heat loads associated with advanced fusion reactor operation modes and off-normal events. Quantitative data available in the literature, such as porosity, oxygen content, thermal conductivity of the coatings, residual stresses accumulated in the coating–substrate interface, surface temperature, and material loss following heat load events, were summarized and compared to bulk W ones. The results demonstrate that, following optimization of the fabrication process, PS-W coatings exhibit excellent performance. In addition, previously mentioned advantages of PS technology make PS-W coatings an attractive alternative for PFM fabrication. Full article
(This article belongs to the Special Issue Advanced Surface Engineering Materials: Characterization and Properties (2nd Edition))
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13 pages, 7509 KiB  
Article
Study on AC Loss of REBCO Tape Encapsulated with Magnetic Materials
by Wei Chen, Rong Jin, Yang Bai, Fei Chi, Jiaqing Xu, Xinsheng Yang and Yunpeng Zhu
Crystals 2025, 15(5), 407; https://doi.org/10.3390/cryst15050407 - 26 Apr 2025
Viewed by 202
Abstract
REBCO coated conductors have a multi-layer structure, and the outer encapsulation layer is generally made of non-magnetic copper material. This paper proposes a new structure of REBCO tape, which replaces the copper layer with magnetic material to explore its transport loss and magnetization [...] Read more.
REBCO coated conductors have a multi-layer structure, and the outer encapsulation layer is generally made of non-magnetic copper material. This paper proposes a new structure of REBCO tape, which replaces the copper layer with magnetic material to explore its transport loss and magnetization loss. The results indicate that copper-encapsulated REBCO tapes have lower transport losses at low currents, while tapes encapsulated with strong magnetic nickel alloy materials have the highest transport losses. At high transport currents, the transport losses of REBCO tapes encapsulated with different materials are almost equal. At low fields, the magnetization loss of the tape encapsulated with strong magnetic nickel alloy is lower, while the magnetization loss of the tape encapsulated with copper is the highest, due to the magnetic shielding effect of the magnetic material. Under high-field conditions, the difference in magnetization loss between magnetic material-encapsulated tapes and copper-encapsulated tapes decreases. Full article
(This article belongs to the Special Issue Superconductors and Magnetic Materials)
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19 pages, 6524 KiB  
Article
Hydrogen-Bonded Ladder Motifs in Naphthalene Dicarboxamides: Influence of Linear vs. Angular Amide Orientation
by Abdulrahman Mohabbat, István Boldog, Takin Haj Hassani Sohi, Nils Reistel, Philipp Seiffert and Christoph Janiak
Crystals 2025, 15(5), 406; https://doi.org/10.3390/cryst15050406 - 26 Apr 2025
Viewed by 197
Abstract
The crystal structures of naphthalene dicarboxamides, namely 1,4-naphthalene dicarboxamide (1,4-NDA), 2,6-naphthalene dicarboxamide (2,6-NDA), and 2,7-naphthalene dicarboxamide (2,7-NDA), are presented for the first time, along with an analysis of their supramolecular organization. The compounds, obtained in single-crystalline form via solvothermal crystallization from methanol, are [...] Read more.
The crystal structures of naphthalene dicarboxamides, namely 1,4-naphthalene dicarboxamide (1,4-NDA), 2,6-naphthalene dicarboxamide (2,6-NDA), and 2,7-naphthalene dicarboxamide (2,7-NDA), are presented for the first time, along with an analysis of their supramolecular organization. The compounds, obtained in single-crystalline form via solvothermal crystallization from methanol, are stable in air to near 350 °C and have melting points above 300 °C. In their densely packed structures (ρ = 1.43–1.47 cm3g−1) the combination of C11 (4) chains and R22(8) rings generates one-dimensional hydrogen-bonded ladders, with an additional R42(8) pattern. The amide groups and the naphthalene rings form dihedral angles between 22° and 40°. Neighboring H-bond ladders run parallel in 1,4-NDA and 2,6-NDA and are connected by means of the naphthalenedyil cores so that two-dimensional (2D) H-bonded sheets are obtained. Except for a weak intra-sheet π–π stacking in 1,4-NDA, there are no π–π stacking and C–H⋯π interactions. The R22(8) rings act as four-connected nodes, leading to the formation of two-dimensional H-bonded planar sheets with sql topology for the nearly linear dicarboxamides 1,4-NDA and 2,6-NDA and cds topology for the angular 2,7-NDA. Hirshfeld surface analysis and NCI plots provide additional insight into the H-bonding interactions. Full article
(This article belongs to the Section Crystal Engineering)
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