Crystals

17 pages, 5074 KiB

Open AccessArticle

Band-like Inhomogeneity in Bulk ZnGeP₂ Crystals, and Composition and Influence on Optical Properties

by Alexey Lysenko, Nikolay N. Yudin, Margarita Khimich, Mikhail Zinovev, Elena Slyunko, Sergey Podzyvalov, Vladimir Kuznetsov, Andrey Kalsin, Maxim Kulesh, Houssain Baalbaki and Alexey Olshukov

Crystals 2025, 15(4), 382; https://doi.org/10.3390/cryst15040382 - 21 Apr 2025

Abstract

The influence of intrinsic impurities on the formation of band-like inhomogeneities in ZGP single crystals containing two highly volatile elements has been analyzed. It has been shown that the formation of growth bands occurs due to the accumulation of binary phosphides at the [...] Read more.

The influence of intrinsic impurities on the formation of band-like inhomogeneities in ZGP single crystals containing two highly volatile elements has been analyzed. It has been shown that the formation of growth bands occurs due to the accumulation of binary phosphides at the crystallization front and is accompanied by the formation of pores in the near-wall region of the ingot. A connection between near-wall pore formation and the presence of growth bands in ZGP has been established. X-ray spectrometry revealed differences in the chemical compositions of “light” and “dark” growth striations, with significant deviations from stoichiometry in these regions. The dark bands exhibited a higher phosphorus content compared to the light bands and showed an increased germanium content in the light bands. Differences in the orientation of crystallographic axes were observed between the light and dark regions. It has been shown that samples containing inclusions of band-like inhomogeneity significantly distort the profile of the radiation passing through and generated in the crystal and lead to pronounced astigmatism. However, in contrast to the extremely negative influence of banded inhomogeneity on the optical properties of single crystals, the influence of growth striations on the radiation resistance of crystals is minimal. Full article

(This article belongs to the Section Inorganic Crystalline Materials)

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10 pages, 4063 KiB

Open AccessArticle

Enhancement of Optoelectronic Properties of Multicrystalline Silicon Using Al-NPs and SiN_x Layer

by Mohamed Ben Rabha, Ameny El Haj, Achref Mannai, Karim Choubani, Mohammed A. Almeshaal and Wissem Dimassi

Crystals 2025, 15(4), 381; https://doi.org/10.3390/cryst15040381 - 21 Apr 2025

Abstract

In this study, we investigated and compared the influence of alumina nanoparticles (Al-NPs) and silicon nitride (SiN_x) layers individually deposited on multi-crystalline silicon (mc-Si) on mc-Si’s structural, optical, and optoelectronic characteristics to improve surface quality. Alumina nanoparticle-covered multi-crystalline silicon, immersion in [...] Read more.

In this study, we investigated and compared the influence of alumina nanoparticles (Al-NPs) and silicon nitride (SiN_x) layers individually deposited on multi-crystalline silicon (mc-Si) on mc-Si’s structural, optical, and optoelectronic characteristics to improve surface quality. Alumina nanoparticle-covered multi-crystalline silicon, immersion in HF/H₂O₂/HNO₃, and porous silicon (PS) covered with a silicon nitride structure are key components in achieving high electronic quality in multi-crystalline silicon. Surface reflectivity decreased from 27% to a minimum value of 2% for alumina nanoparticles/PS and a minimum value of 5% for silicon nitride/PS at a wavelength of 930 nm. Meanwhile, the minority carrier diffusion length increased from 2 µm to 300 µm for porous silicon combined with silicon nitride and to 100 µm for alumina nanoparticles/porous silicon. Two-dimensional current mapping further demonstrated a considerable enhancement in the generated current, rising from 2.8 nA for untreated mc-Si to 34 nA for Al-NPs/PS and 66 nA for PS/SiN_x. These results confirm that the surface passivation of mc-Si using Al-NPs or PS combined with SiN_x is a promising and efficient method to improve the electrical quality of mc-Si wafers, contributing to the development of high-performance mc-Si-based solar cells. Full article

(This article belongs to the Special Issue Crystalline Materials for Energy Conversion Applications in Solar Cells)

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15 pages, 4448 KiB

Open AccessArticle

Crystal Form Diversity of 2-(4-(Diphenylamino)benzylidene) Malononitrile

by Haorui Gu and Qingwen Lin

Crystals 2025, 15(4), 380; https://doi.org/10.3390/cryst15040380 - 21 Apr 2025

Abstract

In the present work, we report the synthesis and characterization of 2-(4-(diphenylamino)benzylidene) malononitrile (DPAM) via a piperidine-catalyzed Knoevenagel condensation reaction. Two distinct crystal forms (A-1 and A-2) of this product were obtained by controlling the crystallization conditions, exhibiting orthorhombic and monoclinic [...] Read more.

In the present work, we report the synthesis and characterization of 2-(4-(diphenylamino)benzylidene) malononitrile (DPAM) via a piperidine-catalyzed Knoevenagel condensation reaction. Two distinct crystal forms (A-1 and A-2) of this product were obtained by controlling the crystallization conditions, exhibiting orthorhombic and monoclinic crystal systems, respectively. Single-crystal X-ray diffraction revealed that both forms exhibited highly twisted benzene rings, which suppressed exciplex or excimer formation, enhancing luminescence. Crystal A-1, with a higher density, showed stronger hydrogen bonding and more rigid molecular packing, while A-2, with a lower density, exhibited weaker π–π interactions. Both crystals demonstrated high thermal stability. Notably, the A-2 crystal displayed a mechanochromic behavior: grinding or applying pressure induced a structural transformation into A-1, accompanied by a fluorescence shift from red to yellow. This transformation was attributed to increased steric hindrance and changes in molecular packing. This study highlights the relationship between crystal structure and optoelectronic properties, offering insights into the design of organic crystalline materials for applications in pressure sensing, anti-counterfeiting, and information encryption. Full article

(This article belongs to the Section Crystal Engineering)

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17 pages, 11739 KiB

Open AccessArticle

Study on Microstructure and Properties of Friction-Assisted Electrodeposition Cu-SiC Deposited Layer

by Kang Qi, Kun Li, Youliang Yu, Qinpeng Sun, Xiaotong Yao and Long Jiang

Crystals 2025, 15(4), 379; https://doi.org/10.3390/cryst15040379 - 21 Apr 2025

Abstract

Based on the friction phenomenon, this study proposes a new method for localized electrodeposition preparation and prepares Cu-SiC composite deposited layers on copper substrates. The morphology of the deposited layer was observed using optical microscopy; the physical phase of the deposited layer was [...] Read more.

Based on the friction phenomenon, this study proposes a new method for localized electrodeposition preparation and prepares Cu-SiC composite deposited layers on copper substrates. The morphology of the deposited layer was observed using optical microscopy; the physical phase of the deposited layer was analyzed by X-ray diffraction; and the microstructure and size of the deposited layer were examined using scanning electron microscopy. The wear resistance of the deposited layer was evaluated through friction and wear experiments. The study found that the friction speed significantly influenced the morphology and size of the deposited layer. At a friction speed of 40 mm/s, the width of the deposited layer increased by 68.7%. Under the friction effect, the wear resistance of the deposited layer was improved. The coefficient of friction and wear width were reduced by 25.6% and 21.2%, respectively. The electrodeposited layer microstructure indicates that increasing the friction speed helps refine the microstructure. This has a significant impact on improving the performance of the electrodeposited layer. Full article

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

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10 pages, 2649 KiB

Open AccessArticle

Ammonia Content in Natural Taranakite: An Experimental Study of Thermal Stability

by Michael Casale, Yuri Galliano, Cristina Carbone and Anna Maria Cardinale

Crystals 2025, 15(4), 378; https://doi.org/10.3390/cryst15040378 - 20 Apr 2025

Abstract

Taranakite is a mineral consisting of a hydrated layered aluminum phosphate, with the formula K₃Al₅(PO₃OH)₆(PO₄)₂·18H₂O; its structure belongs to the R-3C group. If the mineral grows in an environment [...] Read more.

Taranakite is a mineral consisting of a hydrated layered aluminum phosphate, with the formula K₃Al₅(PO₃OH)₆(PO₄)₂·18H₂O; its structure belongs to the R-3C group. If the mineral grows in an environment rich in bat and bird guano, the high nitrogen guano content induces the intercalation of NH₄⁺ into the structure, replacing the potassium ion. The thermal decomposition of guano-derived taranakite releases water and ammonia. The aim of this work is to confirm the presence of ammonium in the guano-derived taranakite. Thermogravimetric analysis (TGA) was performed on taranakite collected in Pollera Cave (Liguria), and the gases evolved during its decomposition were analyzed by Fourier-transform infrared (FT-IR) spectroscopy. All the samples were characterized before and after thermal analysis by means of powder X-ray diffractometry (PXRD) and scanning electron microscopy (SEM). The release of crystallization water occurs at a temperature below 200 °C; further ammonia can be detected above 200 °C. Full article

(This article belongs to the Special Issue Layered Materials and Their Applications)

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25 pages, 11941 KiB

Open AccessArticle

Optimization of Spray Parameters and Corrosion Properties of Plasma-Sprayed Cr₂O₃ Coatings Using Response Surface Methodology

by Minghui Liu, Zhiwen Tan, Yuantao Zhao, Haoran Wang, Shitao Zhang, Rong Ma, Tao Jiang, Zhen Ma, Ning Zhong and Wenge Li

Crystals 2025, 15(4), 377; https://doi.org/10.3390/cryst15040377 - 19 Apr 2025

Viewed by 49

Abstract

In this study, the experimental design of response surface methodology was used to explore the interaction between spraying parameters to obtain an optimized process to reduce the porosity of the coating, and to prepare an excellent chromium oxide coating. The order of the [...] Read more.

In this study, the experimental design of response surface methodology was used to explore the interaction between spraying parameters to obtain an optimized process to reduce the porosity of the coating, and to prepare an excellent chromium oxide coating. The order of the single parameter affecting porosity is as follows: power > main gas > spraying distance > carrier gas flow. This study found that the spraying process with the lowest porosity of the chromium oxide coating is as follows: power of 625 W, stand-off distance of 105 mm, primary gas of 42.5 lpm, carrier gas flow of 5 lpm, and feed powder delivery rate of 35 g/min. The EDS results show that the Cr and O elements in the coating with the lowest porosity are uniformly distributed, while for the coating with the highest porosity, the elements are unevenly distributed to a certain extent, which is caused by the unevenness of the structure caused by the structure defects. The corrosion current density of chromium oxide coating VI (low porosity) is 4.34 × 10⁻⁶ A, whereas that of chromium oxide coating IV (high porosity) is 1.862 × 10⁻⁵ A. On the coating with the highest porosity, the corrosion activity is dominant, while the minimum porosity of coating is the smallest. Full article

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

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19 pages, 10107 KiB

Open AccessArticle

Understanding the Deformation and Fracture Behavior of β−HMX Crystal and Its Polymer−Bonded Explosives with Void Defects on the Atomic Scale

by Longjie Huang, Yan Li, Yuanjing Wang, Rui Liu, Pengwan Chen and Yu Xia

Crystals 2025, 15(4), 376; https://doi.org/10.3390/cryst15040376 - 18 Apr 2025

Viewed by 111

Abstract

The effect of the void defect on β−HMX−based polymer−bonded explosives (PBXs) for a comprehensive understanding of the deformation and fracture process is lacking. In this paper, the atomic scale model of the β−HMX crystal and its PBX is built using LAMMPS software to [...] Read more.

The effect of the void defect on β−HMX−based polymer−bonded explosives (PBXs) for a comprehensive understanding of the deformation and fracture process is lacking. In this paper, the atomic scale model of the β−HMX crystal and its PBX is built using LAMMPS software to investigate the mechanical response under dynamic tensile conditions. The void defect considers both regular and stochastic distributions. The simulation concerns the deformation and fracture process with respect to the void size, void number, void spacing, and the stochastic characteristics. The tensile stress–strain relationship is obtained, and the fracture morphology is simulated well. The crack propagation is discussed in detail. Further, the fracture mode is compared between the single crystal and PBX. In addition, the characteristic defect parameter combines both the damage area and the void spacing, and it is used to predict the crack occurrence and propagation for the single crystal. However, for PBX, the interface between the crystal and binder determines the fracture process instead of the characteristic defect parameter. Full article

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11 pages, 4078 KiB

Open AccessArticle

Solvent Engineering for Layer Formation Control with Cost-Effective Hole Transport Layer in High-Efficiency Perovskite Solar Cell

by Jinyoung Kim, Gyu Min Kim and Se Young Oh

Crystals 2025, 15(4), 375; https://doi.org/10.3390/cryst15040375 - 18 Apr 2025

Viewed by 73

Abstract

Among hole transport materials (HTMs), 2,2′,7,7′-Tetrakis(N,N-di-p-methoxyphenylamino)-9,9′-spirobifluorene (spiro-OMeTAD) is the most frequently adopted, due to its suitable energy band level in conventional-type perovskite solar cells (PSCs). However, the high price of spiro-OMeTAD is an obstacle faced in its research and [...] Read more.

Among hole transport materials (HTMs), 2,2′,7,7′-Tetrakis(N,N-di-p-methoxyphenylamino)-9,9′-spirobifluorene (spiro-OMeTAD) is the most frequently adopted, due to its suitable energy band level in conventional-type perovskite solar cells (PSCs). However, the high price of spiro-OMeTAD is an obstacle faced in its research and commercialization. In our previous work, we introduced a low-cost HTM, (E,E,E,E)-4,4′,4″,4‴-[Benzene-1,2,4,5-tetrayltetrakis(ethene-2,1-diyl)]tetrakis[N,N-bis(4-methoxyphenyl)aniline] (α2); however, it was immiscible in the conventional solvent chlorobenzene, leading to the adoption of dichloromethane (DCM) as an alternative. Nevertheless, its high vapor pressure led to poor reproducibility, limiting its practical applicability. To address this issue, we investigated alternative solvents to DCM to facilitate the application of α2 to dichloride alkane materials, from 1,2-dichloroethane (DCE) to 1,4-dichlorobutane. In these materials, DCE exhibits the most superior properties in terms of layer formation control, due to its vapor pressure in spin-coating. Accordingly, a PSC containing α2-DCE HTL showed high performance, with 1.15V of open-circuit voltage and a 22.7% power conversion efficiency. Full article

(This article belongs to the Special Issue Advances in Materials for Energy Conversion and Storage)

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39 pages, 2266 KiB

Open AccessReview

Design and Processing of Metamaterials

by Andrei Teodor Matei, Anita Ioana Vișan and Gianina Florentina Popescu-Pelin

Crystals 2025, 15(4), 374; https://doi.org/10.3390/cryst15040374 - 18 Apr 2025

Viewed by 96

Abstract

Metamaterials represent artificially structured materials that exhibit unusual properties, such as a negative refractive index, negative permeability and permittivity, negative cloaking by Poisson ratios and optical effects, etc., which are inaccessible in natural materials. According to recent developments, novel devices and tools based [...] Read more.

Metamaterials represent artificially structured materials that exhibit unusual properties, such as a negative refractive index, negative permeability and permittivity, negative cloaking by Poisson ratios and optical effects, etc., which are inaccessible in natural materials. According to recent developments, novel devices and tools based on metamaterials are attracting great interest as they offer improved performance, functionality, sensitivity, biocompatibility, complex structures, and design freedom. Leveraging numerical design approaches, such as finite element analysis and finite difference time domain methods, researchers have tailored metamaterials to meet specific requirements in various areas through a range of manufacturing techniques. These materials can be broadly classified into optical, mechanical, thermal, electromagnetic, and acoustic categories based on their properties and intended use. The choice of fabrication method depends heavily on the specific application, the desired scale, and the complexity of the metamaterial design. These manufacturing methods can be broadly divided into top-down and bottom-up approaches, while each of them has advantages and limitations and offers valuable pathways for the development of the final product. This review offers a basic overview of metamaterials, covering their fundamental principles, fabrication and characterization techniques, and current design methodologies. It also explores their diverse applications, including specific case studies in medicine, while addressing existing limitations and challenges. Finally, this review highlights future perspectives, emphasizing the need for continued innovation in fabrication and characterization to unlock the full potential of metamaterials. Full article

(This article belongs to the Special Issue Metamaterials and Their Devices, Second Edition)

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18 pages, 7231 KiB

Open AccessArticle

Electron Beam Welding of Dissimilar Ti6Al4V and Al6082-T6 Alloys Using Magnetron-Sputtered Cu Interlayers

by Georgi Kotlarski, Darina Kaisheva, Maria Ormanova, Milka Atanasova, Angel Anchev, Vladimir Dunchev, Borislav Stoyanov and Stefan Valkov

Crystals 2025, 15(4), 373; https://doi.org/10.3390/cryst15040373 - 18 Apr 2025

Viewed by 159

Abstract

In the present work, the influence of a magnetron-sputtered copper interlayer on the process of electron beam welding of Ti6Al4V and Al6082-T6 plates was investigated. A sample without a filler was also prepared as a control. The microstructure, microhardness, and tensile properties of [...] Read more.

In the present work, the influence of a magnetron-sputtered copper interlayer on the process of electron beam welding of Ti6Al4V and Al6082-T6 plates was investigated. A sample without a filler was also prepared as a control. The microstructure, microhardness, and tensile properties of both samples were determined. Applying a copper interlayer resulted in the formation of an additional CuAl₂ intermetallic compound in the form of a eutectic structure along the boundary of the aluminum crystal grains. A noticeable shift in the preferred crystallographic orientation of the aluminum phase from the denser {111} family of crystallographic planes in the case of the sample prepared without a filler towards less-dense ones such as {110}, {100}, and {311} in the case of applying a copper filler was observed. This was most probably caused by the lower free surface energy of the crystals oriented towards the {111} family of crystal planes, which favored the chemical bonding between the aluminum solid solution and the CuAl₂ intermetallics. As a result of applying the copper interlayer, a noticeable increase in the microhardness of the weld seam was observed from 78 ± 2 HV0.05 to 136 ± 3 HV0.05. Applying a copper interlayer also led to an improved energy absorption capacity of the weld seam, as suggested by the increase in the UTS/YS ratio from 1.03 to 1.44. This could be explained by the smooth transition between the highly dissimilar Ti6Al4V and Al6082-T6 alloys. The UTS of the sample with the copper filler reached 208 MPa, which was about 60% of that of the base Al6082-T6 alloy. Full article

(This article belongs to the Special Issue Advanced Welding and Additive Manufacturing)

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13 pages, 5682 KiB

Open AccessArticle

Temperature-Dependent Optical Absorption and DLTS Study of As-Grown and Electron-Irradiated GaSe Crystals

by Ruslan A. Redkin, Nikolay I. Onishchenko, Alexey V. Kosobutsky, Valentin N. Brudnyi, Xinyang Su and Sergey Yu. Sarkisov

Crystals 2025, 15(4), 372; https://doi.org/10.3390/cryst15040372 - 18 Apr 2025

Viewed by 135

Abstract

Optical absorption spectra of 9 MeV electron-irradiated GaSe crystals measured at temperatures in the range from 9.5 to 300 K were analyzed. The absorption spectra with features caused by Ga vacancies in two charge states and direct interband transitions were fitted by a [...] Read more.

Optical absorption spectra of 9 MeV electron-irradiated GaSe crystals measured at temperatures in the range from 9.5 to 300 K were analyzed. The absorption spectra with features caused by Ga vacancies in two charge states and direct interband transitions were fitted by a model equation. Temperature dependencies of the defect concentrations and optical transition energies, as well as of the GaSe band gap, were determined. Current- and capacitance-voltage characteristics and DLTS spectra were measured for as-grown and electron-irradiated GaSe slabs with Sc (barrier) and Pt (ohmic) contacts. An experimental Sc/GaSe Schottky barrier height of 1.12 eV was determined in close agreement with a theoretical estimate. The activation energy and the hole capture cross-section deduced from the DLTS data are 0.23 (0.66) eV and 1.5 × 10⁻¹⁹ (2.3 × 10⁻¹⁵) cm⁻² for the supposed

V_{Ga}^{- 1}

(

V_{Ga}^{- 2}

) defect. For the electron-irradiated GaSe crystals, the found activation energies are close to the values inferred from the optical measurements. Full article

(This article belongs to the Section Inorganic Crystalline Materials)

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18 pages, 7058 KiB

Open AccessArticle

Molecular Structure and GPR35 Receptor Docking of 1,3-Phenylene Bis-Oxalamide Derivatives

by Juan Saulo González-González, José Martín Santiago-Quintana, José Luis Madrigal-Angulo, Lina Barragán-Mendoza, Nancy E. Magaña-Vergara, Efrén V. García-Báez, Itzia Irene Padilla-Martínez and Francisco Javier Martínez-Martínez

Crystals 2025, 15(4), 371; https://doi.org/10.3390/cryst15040371 - 17 Apr 2025

Viewed by 112

Abstract

A series of three 1,3-phenylene bis-oxamides 3a–c, structurally related to the GPR35 receptor-agonist drug lodoxamide, has been synthesized by reacting the 1,3-phenylene bis-oxalamates 2a and 2b with amines. The obtained compounds were characterized by ¹H and ¹³C NMR, [...] Read more.

A series of three 1,3-phenylene bis-oxamides 3a–c, structurally related to the GPR35 receptor-agonist drug lodoxamide, has been synthesized by reacting the 1,3-phenylene bis-oxalamates 2a and 2b with amines. The obtained compounds were characterized by ¹H and ¹³C NMR, and IR spectroscopy, they showed characteristic signals for the aromatic, N―H, and C=O groups. Molecular structure was determined using single-crystal X-ray diffraction. The supramolecular architecture is driven by N―H···O=C, N―H···N, C—H···π, and O=C···O=C interactions depicting a supramolecular helix (3a) and tapes (3b–c). Intermolecular interactions were studied using Hirshfeld surface analysis, where N―H∙∙∙X (X = N, O) hydrogen bonding represents 30.2% to the surface of 3a and 17.8–18.8% to the surface of 3b–c. The most energetic interactions involve the amide N—H∙∙∙O hydrogen bonding, contributing in the −113.9 to −97.0 kJ mol⁻¹ range to the crystal energy, being more dispersive than electrostatic in nature. The molecular docking study was performed to evaluate the binding ability of 3a–c compounds to the GPR35 receptor, showing a favorable binding in a similar way to lodoxamide. Full article

(This article belongs to the Section Biomolecular Crystals)

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14 pages, 10839 KiB

Open AccessArticle

Microstructural Stability and Creep Behavior of a Re/Ru Single-Crystal Nickel-Based Alloy

by Ning Tian

Crystals 2025, 15(4), 370; https://doi.org/10.3390/cryst15040370 - 17 Apr 2025

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Abstract

By testing the creep properties of a Re/Ru-containing single-crystal alloy specimen and examining the microstructural evolution of the allow at different stages of creep using scanning electron microscopy (SEM) and transmission electron microscopy (TEM), the deformation and damage mechanisms of the alloy under [...] Read more.

By testing the creep properties of a Re/Ru-containing single-crystal alloy specimen and examining the microstructural evolution of the allow at different stages of creep using scanning electron microscopy (SEM) and transmission electron microscopy (TEM), the deformation and damage mechanisms of the alloy under ultra-high temperature conditions were investigated. It was observed that a dislocation network forms before the rafting of the γ′ phase. As creep progresses, this network becomes increasingly dense and complete. Moreover, the dislocation network undergoes a transformation from the <110>-type to the <100>-type configuration, with a hybrid <110>-<100>-type network representing an intermediate state during the transition. Stacking faults were also identified within the γ′ phase, suggesting that the stacking fault energy of this alloy is lower compared to that of other alloys. During creep, dislocations that penetrate the γ′ phase can undergo cross slip from the {111} plane to the {100} plane under applied stress, resulting in the formation of Kear–Wilsdorf (K–W) immobile dislocation locks. These locks hinder further dislocation movement within the γ′ phase. It is concluded that the damage mechanism of the alloy at the later stage of creep under 120 MPa/1160 °C involves initial crack formation at the interface of the twisted raft-like γ/γ′ two-phase structure. As creep continues, the crack propagates in a direction perpendicular to the applied stress axis. Full article

(This article belongs to the Special Issue Microstructure and Mechanical Properties of Alloys and Composites)

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8 pages, 2239 KiB

Open AccessCommunication

Quantitative Analysis of Shear Texture Evolution in Accumulative Roll Bonded AA 1060 Aluminum Alloy

by Peng Du, Chao Li, Lei Liu, Bao Chen, Mingyu Li, Zhijie Wang and Sha Liu

Crystals 2025, 15(4), 369; https://doi.org/10.3390/cryst15040369 - 17 Apr 2025

Viewed by 69

Abstract

AA 1060 aluminum alloy underwent roll bonding with reductions of 25% and 35%, followed by accumulative roll bonding (ARB) for up to seven cycles at ambient temperature. The evolution of surface layer texture throughout the ARB process was analyzed using X-ray diffraction. Initially, [...] Read more.

AA 1060 aluminum alloy underwent roll bonding with reductions of 25% and 35%, followed by accumulative roll bonding (ARB) for up to seven cycles at ambient temperature. The evolution of surface layer texture throughout the ARB process was analyzed using X-ray diffraction. Initially, the cube texture at the surface progressively transitioned to the r-cube texture throughout ARB, and the r-cube orientation intensity increases from 0 to 9.2 as the true strain accumulates. The shear texture evolution at the surface layer was quantified through mathematical formulations of texture volume fractions and accumulated true strain. The rate (dM_i/dε) of cube texture reduction and r-cube texture formation are initially 15% and 20%, respectively, and they decrease rapidly with increasing cumulative true strain and then slow down to 0.6% and 0.8%. The quantitative analysis of the texture evolution used the JMAK equation, which is rarely applied in ARB studies. Full article

(This article belongs to the Special Issue Microstructure and Deformation of Advanced Alloys)

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11 pages, 2888 KiB

Open AccessArticle

In Situ Observation of Microwave Sintering-Induced Directional Pores in Lithium Cobalt Oxide for Vertical Microchannel Electrodes

by Liangyuan Wang, Yu Xiao, Yilin Lu and Xiao Wang

Crystals 2025, 15(4), 368; https://doi.org/10.3390/cryst15040368 - 17 Apr 2025

Viewed by 84

Abstract

As an efficient energy storage solution, lithium-ion batteries (LIBs) play a crucial role in the electric vehicle sector, driving innovation and development in the automotive industry. One common strategy to enhance energy density is to manufacture thicker electrodes. However, the pore distribution in [...] Read more.

As an efficient energy storage solution, lithium-ion batteries (LIBs) play a crucial role in the electric vehicle sector, driving innovation and development in the automotive industry. One common strategy to enhance energy density is to manufacture thicker electrodes. However, the pore distribution in thicker electrodes is often suboptimal, with elongated and tortuous pathways impeding charge transport. Optimizing the pore structure in electrodes is essential for fabricating high-performance batteries. In this study, we performed microwave sintering on lithium cobalt oxide materials and observed the three-dimensional evolution of pores during the sintering process using synchrotron radiation computed tomography (SR-CT).We discovered that pore evolution exhibits directional characteristics. Further analysis revealed that the electromagnetic loss of particles is related to the direction of the electric field, which is the reason for the directional behavior of pore evolution. This research could provide a new potential approach for the fabrication of advanced electrode materials by using electric field control during the battery manufacturing process to align pores vertically, thereby improving both the energy density and charge–discharge rate of the battery. Full article

(This article belongs to the Special Issue Electrode Materials in Lithium-Ion Batteries)

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18 pages, 7452 KiB

Open AccessArticle

Anisotropy of Voltage Sensitivity of Bow-Tie Microwave Diodes Containing 2DEG Layer

by Algirdas Sužiedėlis, Steponas Ašmontas, Jonas Gradauskas, Aurimas Čerškus, Andžej Lučun, Maksimas Anbinderis and Ihor Zharchenko

Crystals 2025, 15(4), 367; https://doi.org/10.3390/cryst15040367 - 17 Apr 2025

Viewed by 80

Abstract

Microwave Bow-Tie Diodes operate across a broad frequency range, including THz radiation detection and THz imaging applications. When fabricated using modulation-doped structures, these diodes exhibit enhanced detection properties that are best characterized by voltage sensitivity. The sensitivity is influenced by multiple factors, including [...] Read more.

Microwave Bow-Tie Diodes operate across a broad frequency range, including THz radiation detection and THz imaging applications. When fabricated using modulation-doped structures, these diodes exhibit enhanced detection properties that are best characterized by voltage sensitivity. The sensitivity is influenced by multiple factors, including diode design, semiconductor material quality, and the characteristics of the ohmic contacts. In this study, we examine how the electrical properties of modulation-doped bow-tie diodes are affected by their orientation relative to the crystallographic axes. Extensive investigations on various bow-tie diodes exposed to broadband microwave radiation, both in darkness and under white and infrared light illumination, enabled us to identify the optimal diode designs and illumination conditions for maximizing sensitivity to electromagnetic radiation. Based on our findings, we provide recommendations for diode design and illumination conditions to enhance the diode’s sensitivity to microwave radiation while minimizing illumination-induced effects on electrical properties. Full article

(This article belongs to the Special Issue Growth, Structural Identification, and Characterization of Semiconductor Alloys and Low-Dimensional Heterostructures)

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15 pages, 5809 KiB

Open AccessArticle

A Novel Process Strategy for Efflorescence Control of Ceramsites Sintered from High-Sulfur Kiln Slag

by Peng Lu, Yu Li, Baoqiang Zhao, Yi Huang, Liang Liu and Wenbin Liu

Crystals 2025, 15(4), 366; https://doi.org/10.3390/cryst15040366 - 17 Apr 2025

Viewed by 103

Abstract

The high sulfur content in kiln slag ceramsites leads to pronounced efflorescence, significantly limiting the application of such solid-waste-derived products in construction engineering. In this study, a sintering experiment of 50 kg ceramsites with 60% kiln slag content was conducted at 1150 °C [...] Read more.

The high sulfur content in kiln slag ceramsites leads to pronounced efflorescence, significantly limiting the application of such solid-waste-derived products in construction engineering. In this study, a sintering experiment of 50 kg ceramsites with 60% kiln slag content was conducted at 1150 °C on small-scale ceramsites sintering equipment. The research focused on discussing the mechanisms of efflorescence and putting forward the process strategy to control efflorescence in kiln slag ceramsites. The results revealed that the sulfur content (4.53%) and water absorption rate of ceramsites (8.5%) were the primary causes of efflorescence. During the sintering process, sulfur evolved on the pathway of “pyrite in raw materials→partial oxidation to SO₂ and partial fixation in CaSO₄→decomposition of CaSO₄”. In order to reduce content of sulfur, it was proposed that not only was sulfur in pyrite oxidized enough to be removed in the low-temperature stage but, also, residual CaSO₄ decomposed more to eliminate S in the high-temperature stage. This optimizing sintering process reduced the sulfur content from 2.0% to 0.72%. Furthermore, enhancing its densification contributed to avoiding efflorescence. By controlling its sintering temperature and increasing the formation of Fe₂O₃, the densification of ceramsites was improved by decreasing its water absorption rate from 8.5% to 1.2%, and its efflorescence was thereby enhanced. This provides both a theoretical foundation and technological support for the high-value utilization of high-sulfur solid waste. Full article

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12 pages, 5123 KiB

Open AccessArticle

Enhanced Thermoelectric Properties in Cubic Sn_0.50Ag_0.25Bi_0.25Se_0.50Te_0.50 via MWCNTs Incorporation

by Zhewen Tan, Zhaowei Zeng, Junliang Zhu, Wenying Wang, Lin Bo, Xingshuo Liu, Changcun Li and Degang Zhao

Crystals 2025, 15(4), 365; https://doi.org/10.3390/cryst15040365 - 16 Apr 2025

Viewed by 144

Abstract

Cubic-phase SnSe possesses exceptional crystal structure symmetry while maintaining non-harmonic bond characteristics and ultra-low lattice thermal conductivity, exhibiting superior thermoelectric (TE) application potential compared to its orthorhombic counterpart. Despite recent advancements, systematic investigations on the combined effects of composite engineering strategies in optimizing [...] Read more.

Cubic-phase SnSe possesses exceptional crystal structure symmetry while maintaining non-harmonic bond characteristics and ultra-low lattice thermal conductivity, exhibiting superior thermoelectric (TE) application potential compared to its orthorhombic counterpart. Despite recent advancements, systematic investigations on the combined effects of composite engineering strategies in optimizing TE properties of cubic-phase SnSe-based materials remain scarce. In this study, multi-walled carbon nanotubes (MWCNTs) are incorporated into the cubic-phase Sn_0.50Ag_0.25Bi_0.25Se_0.50Te_0.50 to regulate its TE performance through a combination of ultrasonic dispersion and rapid hot-pressing sintering. The introduced MWCNTs promote the formation of “high-speed channel” for carrier transport and serve as additional phonon-scattering centers, resulting in a synergistic optimization of electrical and thermal transport properties. A maximum ZT value of 0.85 is achieved in the prepared 1.50 wt.% MWCNTs/Sn_0.50Ag_0.25Bi_0.25Se_0.50Te_0.50 sample at 750 K, representing a 21% improvement compared to the pristine Sn_0.50Ag_0.25Bi_0.25Se_0.50Te_0.50 sample. This finding establishes a scalable nano-composite engineering paradigm for enhancing TE performance of cubic-phase SnSe-based materials. Full article

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33 pages, 7495 KiB

Open AccessReview

Advances of Low-Dimensional Organic-Inorganic Hybrid Metal Halide Luminescent Materials: A Review

by Suqin Wang, Hui Zhu, Ming Sheng, Bo Shao, Yu He, Zhuang Liu and Guangtao Zhou

Crystals 2025, 15(4), 364; https://doi.org/10.3390/cryst15040364 - 16 Apr 2025

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Abstract

Low-dimensional organic–inorganic hybrid metal halides (OIMHs) have garnered significant research attention due to their remarkable optical, electrical, and mechanical properties. These materials feature tunable optoelectronic characteristics, high photovoltaic efficiency, exceptional scalability and processability and ease of fabrication. By selecting appropriate organic and inorganic [...] Read more.

Low-dimensional organic–inorganic hybrid metal halides (OIMHs) have garnered significant research attention due to their remarkable optical, electrical, and mechanical properties. These materials feature tunable optoelectronic characteristics, high photovoltaic efficiency, exceptional scalability and processability and ease of fabrication. By selecting appropriate organic and inorganic components, it is possible to achieve molecular-level dimensional control of the metal halides. Here, this review provides an in-depth analysis of the structure and synthesis methods of OIMHs materials, explores their optical properties, and summarizes their current applications in areas such as white-light LEDs, X-ray detectors, sensors, and solar cells. Finally, we also discuss the challenges faced by these materials and offer a perspective on their future development, aiming to serve as a reference for advancing research in OIMHs. Full article

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20 pages, 3934 KiB

Open AccessArticle

Microstructure and High-Temperature Compressive Properties of a Core-Shell Structure Dual-MAX-Phases-Reinforced TiAl Matrix Composite

by Shiqiu Liu and Huijun Guo

Crystals 2025, 15(4), 363; https://doi.org/10.3390/cryst15040363 - 16 Apr 2025

Viewed by 119

Abstract

As an advanced high-temperature structural material, TiAl alloy, is often used in the manufacturing of hot-end components of aviation and aerospace engines. However, it is difficult to increase the strength at high temperature, which limits its wider application. Adopting composite material technology is [...] Read more.

As an advanced high-temperature structural material, TiAl alloy, is often used in the manufacturing of hot-end components of aviation and aerospace engines. However, it is difficult to increase the strength at high temperature, which limits its wider application. Adopting composite material technology is one of the effective ways to improve the comprehensive mechanical properties of TiAl alloy. In this work, by adding 3 wt.% SiC micro-particles to Ti-47.5Al-7Nb-0.4W-0.1B (at.%) pre-alloyed powder, a core-shell structure dual-MAX-phase high-temperature strengthened TiAl matrix composite (also known as TiAl-SiC composite) was prepared by combining powder metallurgy and hot forging. The microstructure and high-temperature compressive properties of the prepared TiAl-SiC composites were studied and compared with TiAl alloy prepared by the same process, and the microstructural characteristics of the TiAl-SiC composite and its microstructure evolution during processing were revealed. The results show that the matrix of as-sintered TiAl-SiC composites was mainly composed of γ phase and a small amount of Ti₂AlC particles, while the reinforcement phase was a dual-MAX-phase core-shell structure, which was mainly composed of core Ti₂AlC phase, shell Ti₃SiC₂ phase, and small Ti₂AlC particles distributed in the outer layer. After hot forging, the microstructure of TiAl-SiC composite became more compact, finer, and more uniform; the phase composition was almost not changed, but the content of Ti₂AlC, Ti₃SiC₂, and TiB₂ phases increased significantly; the content of C in each constituent phase decreased obviously, and a granular Si-rich phase was generated in the core of the reinforcement phase. The yield strength of the as-forged TiAl-SiC composite was significantly higher than that of the as-forged TiAl alloy at temperature higher than 859 °C. This is because the core-shell structure dual MAX phases can effectively reduce the softening rate of TiAl alloy in the range of 800–900 °C, thus playing a strengthening role and increasing the service temperature of TiAl alloy. Full article

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

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2 pages, 150 KiB

Open AccessCorrection

Correction: Lindič et al. First-Principle Investigation of Hypothetical NiF₄ Crystal Structures. Crystals 2022, 12, 1640

by Tilen Lindič, Anthony Schulz and Beate Paulus

Crystals 2025, 15(4), 362; https://doi.org/10.3390/cryst15040362 - 16 Apr 2025

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Abstract

Due to an oversight by the journal’s Editorial Office, the Supplementary Materials were not published alongside the original article [...] Full article

(This article belongs to the Special Issue Recent Developments of Inorganic Crystalline Materials)

15 pages, 3958 KiB

Open AccessArticle

The Influence of Structural Design on the Electronic Properties of a Frisch Grid Cadmium Zinc Telluride Detector by a Finite Element Method

by Zhenzhao Zhang, Yu Li, Meng Cao, Weifan He, Zhen Xu, Jian Huang and Linjun Wang

Crystals 2025, 15(4), 361; https://doi.org/10.3390/cryst15040361 - 15 Apr 2025

Viewed by 140

Abstract

Cadmium zinc telluride (CZT) detectors have the advantages of high detection efficiency and good energy resolution, which are widely used in the fields of X-ray detection, environmental monitoring and nuclear radiation detection. The Frisch grid structure is used more often in the preparation [...] Read more.

Cadmium zinc telluride (CZT) detectors have the advantages of high detection efficiency and good energy resolution, which are widely used in the fields of X-ray detection, environmental monitoring and nuclear radiation detection. The Frisch grid structure is used more often in the preparation of detectors because of its good unipolarity and simple structure. In this paper, the effects of changing the gate position, width and relative dielectric constant on the electrical properties of Frisch grid CZT detectors, such as potential, weight potential, electric field distribution and charge collection efficiency, are simulated in detail by the finite element method. From the simulation results, the optimisation of the performance of the Frisch grid detector is mainly based on minimising the distance between the gate and anode within a reasonable interval, increasing the area of the Frisch grid and selecting a material with a high relative permittivity for the fabrication of the Frisch grid. The research work contributes to the development of CZT detectors. Full article

(This article belongs to the Section Inorganic Crystalline Materials)

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19 pages, 7174 KiB

Open AccessArticle

Phase Transformation and Deformation Mechanisms of 304L Stainless Steel Under Tensile and Charpy Impact Testing at Varying Temperatures

by Gang-Ho Lee, Gwangjoo Jang, Byoungkoo Kim, Changyong Choi, Hee-Sang Park, Jong-Bae Jeon, Changwoo Lee, Sanghoon Noh and Byung Jun Kim

Crystals 2025, 15(4), 360; https://doi.org/10.3390/cryst15040360 - 15 Apr 2025

Viewed by 126

Abstract

This study examines the mechanical behavior and deformation mechanisms of hot-forged 304L stainless steel for cryogenic applications such as LNG storage and low-temperature structural systems. Tensile testing revealed a significant strength increase from 618 MPa at room temperature to 1432 MPa at cryogenic [...] Read more.

This study examines the mechanical behavior and deformation mechanisms of hot-forged 304L stainless steel for cryogenic applications such as LNG storage and low-temperature structural systems. Tensile testing revealed a significant strength increase from 618 MPa at room temperature to 1432 MPa at cryogenic temperatures, with elongation decreasing from 83.7% to 23.3%. Charpy impact testing showed a 28% reduction in absorbed energy at cryogenic temperatures due to enhanced strain-induced martensitic transformation (SIMT). The observed mechanical responses are attributed to reduced stacking fault energy (SFE) at lower temperatures, which promotes SIMT, deformation twinning, and dislocation interactions, affecting material strength and toughness. SEM and EBSD analysis confirmed extensive martensitic transformation, increased deformation twinning, and reduced remaining austenite, indicating a γ → ε → α’ transformation pathway that governs strain hardening. The high strain rate during Charpy impact testing induced localized adiabatic heating, partially suppressing SIMT and modifying fracture behavior by enhancing localized plasticity. These findings emphasize the interplay between SFE, strain rate, and phase transformation in governing the cryogenic mechanical performance of 304L stainless steel. Full article

(This article belongs to the Special Issue Microstructure and Properties of Steels and Other Structural Alloys, Second Edition)

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12 pages, 6351 KiB

Open AccessArticle

The Effect of Heat Input on the Microstructure and Mechanical Properties of Laser-Backing Welded X80 Steel

by Changjiang Wang, Gang Wei, Xiaosong Shi, Feng Wang, Shimin Zhang, Meimei Yang, Chen Yan and Songyang Li

Crystals 2025, 15(4), 359; https://doi.org/10.3390/cryst15040359 - 14 Apr 2025

Viewed by 187

Abstract

The research and related tests aimed to investigate the effect of different heat inputs on the microstructure and properties of the joint when using laser-backing welding for X80 steel, with the purpose of guiding a reasonable adjustment of heat inputs to obtain a [...] Read more.

The research and related tests aimed to investigate the effect of different heat inputs on the microstructure and properties of the joint when using laser-backing welding for X80 steel, with the purpose of guiding a reasonable adjustment of heat inputs to obtain a sound and high-quality joint, and ultimately laying the foundation for the engineering application of laser-backing welding. The fiber-laser-backing welding is performed on a 22 mm thick X80 steel, before which a groove is prepared and assembled; joints were obtained under different heat inputs (162, 180, 210, 270 J/mm) with orthogonal combinations of laser power and welding speed. The microstructure and properties of the joints were characterized by using an optical microscope, scanning electron microscope, and microhardness tester. According to this investigation, the morphology of the joint is directly affected by the heat input, and insufficient heat input (<180 J/mm) will lead to an unacceptable weld profile. The width of the weld and heat-affected zone gets bigger as the heat input increases. The hardness nephograms of the joints under different heat inputs show that the weld has the highest hardness, followed by the coarse-grain heat-affected zone and the fine-grain heat-affected zone, sequentially. The less heat input, the lower the joint hardness; when the heat input increases to 270 J/mm, the coarse-grain zone near the fusion line shows obvious hardening. In addition, heat input also affects the impact toughness of the weld. The grain size of X80 steel with a lower content of niobium easily becomes coarse under excessive heat input (270 J/mm), resulting in the degradation of the grain-boundary slip ability; hence, the impact toughness of the joint deteriorates. The optimal heat input of 210 J/mm was identified, achieving a grain size of nearly 14 µm and providing a balanced combination of lower strength and higher impact toughness. Full article

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

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16 pages, 6303 KiB

Open AccessArticle

The Effect of Sulfur Concentration on the Crystallization and Electrochemical Behavior of Portland Cement

by Byung-Hyun Shin, Jinyong Park, Jeunghyeuon Cho, Miyoung You, Seongjun Kim, Jung-Woo Ok, Jonggi Hong, Taekyu Lee, Jong-Seung Bae, Pungkeun Song and Jang-Hee Yoon

Crystals 2025, 15(4), 358; https://doi.org/10.3390/cryst15040358 - 13 Apr 2025

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Abstract

Portland cement is a critical material widely used in the construction industry, where its crystallization and microstructure are key factors determining its physical and mechanical properties. This study investigated the effect of sulfur on the crystallization and microstructure of Portland cement. Sulfur acts [...] Read more.

Portland cement is a critical material widely used in the construction industry, where its crystallization and microstructure are key factors determining its physical and mechanical properties. This study investigated the effect of sulfur on the crystallization and microstructure of Portland cement. Sulfur acts as either an additive or an impurity during the cement production process, influencing the crystal size, distribution, and microstructure formation of major hydration products such as C₃S (tricalcium silicate), C₂S (dicalcium silicate), C₃A (tricalcium aluminate), and C₄AF (tetracalcium aluminoferrite). Through quantitative and qualitative evaluation using XRD, SEM, and EPMA analytical techniques, this study examined changes in the hydration characteristics, crystal structure, and microstructure of Portland cement with varying sulfur concentrations. The results revealed that increased sulfur content promotes the crystal growth of C₃A and the formation of ettringite, which alters the density of the structure during the early stages of hydration and affects its long-term strength properties. These findings suggest that controlling the sulfur content plays a significant role in optimizing the performance and durability of Portland cement. This study highlights the potential for developing high-performance cement by regulating sulfur levels during the production process, contributing to advancements in construction materials. Full article

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10 pages, 1391 KiB

Open AccessArticle

Luminescence and Scintillation Properties of YAl₃(BO₃)₄ Single Crystal for Thermal Neutron Detection

by Yutaka Fujimoto, Masanori Koshimizu, Hiroki Kawamoto, Kenichi Watanabe, Akio Miyamoto and Keisuke Asai

Crystals 2025, 15(4), 357; https://doi.org/10.3390/cryst15040357 - 12 Apr 2025

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Abstract

A single crystal of YAl₃(BO₃)₄ was grown using the top-seeded solution growth method. The vacuum ultraviolet (VUV) excitation spectrum, monitored at the emission wavelength of 312 and 372 nm, showed a narrow excitation band at around 162 nm, [...] Read more.

A single crystal of YAl₃(BO₃)₄ was grown using the top-seeded solution growth method. The vacuum ultraviolet (VUV) excitation spectrum, monitored at the emission wavelength of 312 and 372 nm, showed a narrow excitation band at around 162 nm, which is located near the absorption edge of the YAl₃(BO₃)₄ host. Upon VUV excitation at 162 nm, the characteristic self-trapped exciton (STE) emission bands were observed at 312 and 372 nm. The X-ray excited scintillation spectrum shows a broad emission band peaking at 310 nm with a weak shoulder band at around 375 nm, which is consistent with photoluminescence, and can thus be assigned to the STE emission. The scintillation light yield under irradiation at a ²⁵²Cf-thermal neutron reached 2700 photons/thermal neutron. Full article

(This article belongs to the Section Inorganic Crystalline Materials)

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12 pages, 9674 KiB

Open AccessArticle

The Thermal Modulation of the Bending Wave Bandgap and Waveguide of Phononic Crystal Plates

by Zhiqiao Wang, Xiaoyang Zhang and Guohao Chen

Crystals 2025, 15(4), 356; https://doi.org/10.3390/cryst15040356 - 12 Apr 2025

Viewed by 194

Abstract

Based on the finite element method, the modulation of the bending wave bandgap and bending waveguide of locally resonant phononic crystal (PnC) plates via a thermal environment is investigated. First, the finite element model of the PnC subjected to a thermal field is [...] Read more.

Based on the finite element method, the modulation of the bending wave bandgap and bending waveguide of locally resonant phononic crystal (PnC) plates via a thermal environment is investigated. First, the finite element model of the PnC subjected to a thermal field is introduced; then, the modulation behavior of the bending wave bandgap of the PnC under thermal flux is illustrated; finally, the tunable waveguide of the bending waveguide of the PnC supercell is proposed to be realized by setting up a local heat source. The results show that the injected heat flux causes the PnC unit cell band structure to move toward the low-frequency region while the relative bandgap width increases. The linear defect state of the PnC supercell structure is realized by introducing a local heat source, and a new band is added to the bending wave bandgap of the original supercell. The transmission loss of the bending wave is significantly higher than that of the bending wave bandgap of the supercell in the frequency interval of the linear defect of the supercell, and the frequency response vibrational modes of the supercell structure validate the feasibility of the thermally controlled bending waveguide. This method provides a flexible and efficient control strategy for the frequency tuning of the bending wave bandgap and waveguide. Full article

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20 pages, 4096 KiB

Open AccessArticle

Process Design for Continuous Crystallization of l-Tryptophan in Water–Alcohol Solvent Mixtures

by Lukas Hohmann, Robert Antpusat (née Hampel) and Norbert Kockmann

Crystals 2025, 15(4), 355; https://doi.org/10.3390/cryst15040355 - 12 Apr 2025

Viewed by 267

Abstract

The study of solid–liquid equilibria in small molecules such as l-tryptophan (l-Trp), which possesses an α-amino group, an α-carboxylic acid group, and an indole compound, presents significant challenges. This research introduces several findings aimed at enhancing process efficiency and sustainability [...] Read more.

The study of solid–liquid equilibria in small molecules such as l-tryptophan (l-Trp), which possesses an α-amino group, an α-carboxylic acid group, and an indole compound, presents significant challenges. This research introduces several findings aimed at enhancing process efficiency and sustainability in downstream processing of l-Trp from fermentative origin via crystallization. Transitioning from batch to continuous processes allows for improved scalability and resource management. Furthermore, solubility measurements combined with thermodynamic data from the literature will provide deeper insights into molecular interactions and allow for systematic and data-driven process design. Lab-scale crystallization experiments in both batch and continuous operation allow for the assessment of the process feasibility and solvent impacts on the process and product. The focus is on process development that emphasizes material savings through strategic solvent selection and co-solvent choices. Full article

(This article belongs to the Special Issue Crystallisation Advances)

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13 pages, 11060 KiB

Open AccessArticle

Influence of Sheet Thickness and Process Parameters on the Microstructure and Mechanical Properties of Brazed Welding Used for Cold-Formed Steel Beams

by Iosif Hulka, Viorel Ungureanu, Silviu Saraolu, Alin Popescu and Alexandru Pascu

Crystals 2025, 15(4), 354; https://doi.org/10.3390/cryst15040354 - 12 Apr 2025

Viewed by 204

Abstract

Metal inert gas (MIG) brazing was used to join galvanized thin sheets with thicknesses in the range of 0.8 to 2 mm in a lap joint configuration using CuAl₈ wire as filler. The process was used to manufacture built-up cold-formed steel beams [...] Read more.

Metal inert gas (MIG) brazing was used to join galvanized thin sheets with thicknesses in the range of 0.8 to 2 mm in a lap joint configuration using CuAl₈ wire as filler. The process was used to manufacture built-up cold-formed steel beams composed of corrugated steel webs and flanges made from thin-walled cold-formed steel lipped channel profiles. The effect of heat input and sheet thickness on joint properties, such as macro- and microstructure, wettability, and mechanical characteristics such as microhardness and tensile strength were investigated. The bead geometry was assessed by studying the wettability of the filler material. The microstructure was investigated by digital and scanning electron microscopy, and the composition in the heat-affected zone (HAZ), interface, and bead was determined by energy dispersive spectroscopy. Formation of Fe–Al intermetallics was observed in the bead at the bead–base material interface. Some pores were noticed that formed due to the evaporation of the zinc coating. The bead shape and mechanical properties were found to be the best when 1.2 and 2 mm sheets were brazed using a heat input of 121.4 J/mm. This suggests that not only the heat input but also the thickness of the sheet metal play a crucial role in the production of MIG brazed joints. Full article

(This article belongs to the Special Issue Welding and Joining of Metallic Materials: Microstructure and Mechanical Properties, 2nd Edition)

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18 pages, 11211 KiB

Open AccessArticle

Synthesis of MXene Composites Using Thiourea as a Nitrogen–Sulfur Precursor

by Junming Zhang, Yefeng Feng, Junhao Peng, Kaidan Wu, Zuyong Feng, Miao He, Kunhua Wen and Deping Xiong

Crystals 2025, 15(4), 353; https://doi.org/10.3390/cryst15040353 - 11 Apr 2025

Viewed by 199

Abstract

In potassium ion electrode materials, MXenes have garnered significant attention in the energy storage field due to their high conductivity and complex surface chemistry. In this work, thiourea was used as a nitrogen–sulfur composite precursor, and a self-assembly method was employed to synthesize [...] Read more.

In potassium ion electrode materials, MXenes have garnered significant attention in the energy storage field due to their high conductivity and complex surface chemistry. In this work, thiourea was used as a nitrogen–sulfur composite precursor, and a self-assembly method was employed to synthesize a material, named nitrogen–sulfur– MXene (NS-MXene). During the reaction, thiourea molecules attach to the surface and interlayers of MXene, increasing the interlayer spacing. Upon heating, thiourea molecules decompose into nitrogen (N) and sulfur (S), which then combine with the MXene material. The N and S provide additional capacity for potassium ion storage, while the increased interlayer spacing also facilitates the intercalation and deintercalation of K⁺. Use of NS-MXene as anode material for potassium-ion batteries results in a high-rate performance (final capacity of 205.2 mAhg⁻¹ at 0.1 Ag⁻¹), long-term cycling stability (128.5 mAhg⁻¹ at 0.5 Ag⁻¹), and a good specific capacity (141 mAhg⁻¹ at 0.1 Ag⁻¹). This groundbreaking discovery opens the door to investigating MXene-based energy storage materials with superior performance and creates a new standard for MXene derivatives. Full article

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

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