Crystals doi: 10.3390/cryst14040317
Authors: Sarah Johanna Hirsch Nadja Berndt Thomas Grund Thomas Lampke
Solid state sintering of cast aluminum powders by resistance heating sintering (RHS), also known as spark plasma sintering or field-assisted sintering technique, creates a very fine microstructure in the bulk material. This leads to high performance material properties with an improved strength and ductility compared to conventional production routes of the same alloys. In this study, the mechanical behavior of an RHS-sintered age-hardenable A357 (AlSi7Mg0.6) cast alloy and a SiCp/A357 aluminum matrix composite (AMC) was investigated. Aiming for high strength and good wear behavior in tribological applications, the AMC was reinforced with a high particle content (35 vol.%) of a coarse particle fraction (d50 = 21 µm). Afterwards, separated and combined effects of particle reinforcement and heat treatment were studied under compressive load both at room temperature and at 350 °C. At room temperature compression, the strengthening effect of precipitation hardening was about twice as high as that for the particle reinforcement, despite the high particle content. At elevated temperatures, the compressive deformation behavior was characterized by simultaneously occurring temperature-activated recovery, recrystallisation and precipitation processes. The occurrence and interaction of these processes was significantly affected by the initial material condition. Moreover, a rearrangement of the SiC reinforcement particles was detected after hot deformation. This rearrangement lead to a homogenized dispersion of the reinforcement phase without considerable particle fragmentation, which offers the potential for secondary thermo-mechanical processing of highly reinforced AMCs.
]]>Crystals doi: 10.3390/cryst14040315
Authors: Ion Mitelea Daniel Mutașcu Ion-Dragoș Uțu Corneliu Marius Crăciunescu Ilare Bordeașu
Fe-Mn-Cr-Ni alloys like Citomangan, delivered in the form of powders, tubular wires, and coated electrodes, are intended for welding deposition operations to create wear-resistant layers. Their main characteristic is their high capacity for surface mechanical work-hardening under high shock loads, along with high toughness and wear resistance. In order to increase the resistance to cavitation erosion, hardfacing of Duplex stainless steel X2CrNiMoN22-5-3 with Citomangan alloy was performed using a new welding technique, namely one that uses a universal TIG source adapted for manual welding with a coated electrode in pulsed current. Cavitation tests were conducted in accordance with the requirements of ASTM G32—2016 standard. Comparing the characteristic cavitation erosion parameters of the manganese austenitic layer, deposited by this new welding technique, with those of the reference steel, highlights an 8–11 times increase in its resistance to cavitation erosion. Metallographic investigations by optical microscopy and scanning electron microscopy (SEM), as well as hardness measurements, were carried out to understand the cavitation phenomena.
]]>Crystals doi: 10.3390/cryst14040316
Authors: Zhiguo Zhang Baowen Zhang Xing Li Shenghu Ding
Cracks and crack-like defects in engineering structures have greatly reduced the structural strength. An interface crack with one contact area in a combined tension–shear field of decagonal quasicrystal bi-material is investigated. Based on the deformation compatibility equation and displacement potential function, the complex representation of stress and displacement is given. Using the mixed boundary conditions, the closed-form expressions for the stresses and the displacement jumps in the phonon field and phason field on the material interface are obtained. The results show that the stress intensity factor at the crack tip is zero for the phason field. The variation in the stress intensity factor and the length of the contact zone in the phonon field is given, and the result is consistent with the properties of the crystal. The design of safe engineering structures and the formulation of reasonable quality acceptance standards may benefit from the theoretical research carried out here.
]]>Crystals doi: 10.3390/cryst14040313
Authors: Jiahui Chen Zhihui Li Yanlei Kang Zhong Li
To aid cocrystal screening, a deep forest-based cocrystal prediction model was developed in this study using data from the Cambridge Structural Database (CSD). The positive samples in the experiment came from the CSD. The negative samples were partly from the failure records in other papers, and some were randomly generated according to specific rules, resulting in a total of 8576 pairs. Compared with the models of traditional machine learning methods and simple deep neural networks models, the deep forest model has better performance and faster training speed. The accuracy is about 95% on the test set. Febuxostat cocrystal screening was also tested to verify the validity of the model. Our model correctly predicted the formation of cocrystal. It shows that our model is practically useful in practice.
]]>Crystals doi: 10.3390/cryst14040314
Authors: Andrés Serna-Gutiérrez Nicolás A. Cordero
The rise of straintronics—the possibility of fine-tuning the electronic properties of nanosystems by applying strain to them—has enhanced the interest in characterizing the mechanical properties of these systems when they are subjected to tensile (or compressive), shear and torsion strains. Four parameters are customarily used to describe the mechanical behavior of a macroscopic solid within the elastic regime: Young’s and shear moduli, the torsion constant and Poisson’s ratio. There are some relations among these quantities valid for elastic continuous isotropic systems that are being used for 2D nanocrystals without taking into account the non-continuous anisotropic nature of these systems. We present in this work computational results on the mechanical properties of six small quasi-square (aspect ratio between 0.9 and 1.1) graphene nanocrystals using the PM7 semiempirical method. We use the results obtained to test the validity of two relations derived for macroscopic homogeneous isotropic systems and sometimes applied to 2D systems. We show they are not suitable for these nanostructures and pinpoint the origin of some discrepancies in the elastic properties and effective thicknesses reported in the literature. In an attempt to recover one of these formulas, we introduce an effective torsional thickness for graphene analogous to the effective bending thickness found in the literature. Our results could be useful for fitting interatomic potentials in molecular mechanics or molecular dynamics models for finite carbon nanostructures, especially near their edges and for twisted systems.
]]>Crystals doi: 10.3390/cryst14040312
Authors: Sagar M. Mane Aviraj M. Teli Sonali A. Beknalkar Deepak R. Patil Jae Cheol Shin Jaewoong Lee
The distinct physicochemical characteristics of metal-free graphitic carbon nitride (g-C3N4) are gaining interest in various fields, including energy storage and conversion. However, the electrochemical performance of this material is constrained, owing to its minimal surface area. Incorporating a surfactant is one of the ways to resolve the issue of surface area and therefore improve the electrochemical performance of g-C3N4. This research delves into a method aimed at improving the supercapacitive capabilities of 2D g-C3N4 sheets through the implementation of a cationic surfactant, cetyltrimethylammonium bromide (CTAB). Electrochemical studies reveal that the CTAB-assisted g-C3N4 sheets exhibit remarkable improvements in specific capacitance, cyclic stability, and comparative rate capability in relation to pristine g-C3N4. The specific capacitance of g-C3N4 with CTAB exceeds about 28%, which gives 162. 8 F g−1. This value is 117.7 F g−1 for electrode material without CTAB at 0.5 mA cm−2. This improved electrochemical performance can be credited to the heightened surface area, improved electronic conductivity, and optimized charge transfer kinetics facilitated by the CTAB surfactant. We aim to emphasize the enhancement of the overall performance of g-C3N4-based supercapacitors for advanced energy storage systems.
]]>Crystals doi: 10.3390/cryst14040311
Authors: Jialin Zhong Li Luo Jiebin Peng Yingyi Huang Quanquan Shi Jiajun Lu Haobin Zhang Feiwan Xie Fugen Wu Xin Zhang Degang Zhao
The concept of “rainbow trapping” has generated considerable interest in wave propagation and energy harvesting, offering new possibilities for diverse and efficient acoustic wave operations. In this work, we investigate a dual-channel topological rainbow trapping device implemented within an underwater two-dimensional phononic crystal based on synthetic dimension. The topological edge states with different frequencies are separated and trapped at different spatial locations. Acoustic waves propagate simultaneously along two boundaries due to the degeneracy of the edge states. In particular, the propagation of a dual-channel topological rainbow is also realized by using a bend design. This work contributes to the advancement of multi-channel devices in synthetic space and provides a reference for the design of highly efficient underwater acoustic devices.
]]>Crystals doi: 10.3390/cryst14040310
Authors: Rouzbeh Aghaei Hakkak Thomas M. Klapötke Thomas Schleid
Two novel energetic anti-perovskite compounds with the chemical formula (N2H5)3X[B12H12] · H2O, where X− is either [NO3]− or [ClO4]−, were successfully synthesized. Both dodecahydro-closo-dodecaborates crystallize orthorhombically in the space group Cmc21, exhibiting relatively similar lattice parameters ((N2H5)3[NO3][B12H12] · H2O: a = 915.94(5), b = 1817.45(9), c = 952.67(5) pm, (N2H5)3[ClO4][B12H12] · H2O: a = 1040.51(6), b = 1757.68(9), c = 942.34(5) pm both for Z = 4). Their synthesis involved a two-step process: first, Cs2[B12H12] passed through a cation exchange column to yield the acidic form of the dodecahydro-closo-dodecaborate, (H3O)2[B12H12]. This aqueous solution was subsequently neutralized with hydrazinium hydroxide and mixed with the corresponding water-dissolved hydrazinium salt (nitrate or perchlorate). Characterization of the obtained crystals was performed by single-crystal X-ray diffraction and Raman spectroscopy as well as thermal analyses (TG-DTA and DSC). The crystal structure determinations revealed that both compounds adopt a hexagonal anti-perovskite structure, distorted by the presence of water molecules. These compounds containing oxidizing oxoanions demonstrate a remarkable ability to release large amounts of energy (almost 2100 J/g) upon thermal decomposition.
]]>Crystals doi: 10.3390/cryst14040309
Authors: Young Soon Kim Md. Abu Hanif Hyeonjin Song Sungeun Kim Yonu Cho Seung-Kon Ryu Hong Gun Kim
The study explored the graphitization of wood through two distinct methods: a high-temperature approach at 2400 °C and a low-temperature technique at 1400 °C using a catalyst. The graphitization properties were assessed by conducting thermal experiments at various temperatures (1100 °C, 1400 °C, 1800 °C, 2000 °C, and 2400 °C), both with and without a catalyst. The development of graphite lattices was quantitatively analyzed using an array of techniques: X-ray diffractometer (XRD), Raman spectroscopy, high-resolution transmission electron microscopy (HR-TEM), and Fourier transform infrared spectroscopy (FTIR). The XRD analysis highlighted temperature-dependent changes in lattice parameters (d002, La, and Lc), while Raman spectroscopy tracked alterations in the D to G peak ratio (D/G) with temperature. An increase in temperature is correlated with a rise in the number of graphene layers and the degree of graphitization. Notably, the process of graphite lattice formation varied across the experimental temperature spectrum. The use of a catalyst resulted in a reduced d002 spacing, signifying an enhanced degree of graphitization. Moreover, the catalyst promoted a consistent and smooth graphitization process throughout the heating stages. In contrast, graphitization without a catalyst occurred at higher temperatures, specifically between 1800 °C and 2000 °C, with the d002 value stabilizing around 0.338 nm. The catalyst proved instrumental in transforming the initial structure into well-ordered graphite at lower temperatures. This investigation underscores the potential and benefits of employing a catalyst to generate high-quality graphite from wood at reduced temperatures, paving the way for sustainable and economically viable applications of this material.
]]>Crystals doi: 10.3390/cryst14040308
Authors: Zhiyuan Yang Kunxiang Ge Wen Cai Shenqiang Liu Shitao Zhang Zhengyang Pan Jianing Zhang Yuantao Zhao Wenge Li Yanbo Liu
For the purpose of improving the wear properties of Ni composite coatings, diamond particles were co-electrodeposited into Ni–diamond composite coatings. The effect of diamond particle concentration in the electrolyte on the surface morphology, microstructure, and wear properties of Ni–diamond composite coatings was investigated. The electrodeposition behaviors of the composite coatings were simulated by COMSOL5.6. The results showed that the content of diamond particles in the coating was elevated by increasing the particle concentration in the electrolyte. The formation of [200] fiber texture was blocked and concurrently brought about crystallite refinement of the Ni deposits by the embedded particles. The COMSOL simulation findings indicated that embedded particles influenced the microstructure of the Ni deposits through processes such as heterogeneous nucleation, rearrangement, and concentration of local current density. The synergistic effect of the tailored microstructure and embedded particles substantially enhanced the wear resistance of the coating. By increasing the particle concentration in the electrolyte, the wear resistance of the coating was gradually enhanced, and the coating electrodeposited at 16 g/L possessed the lowest friction coefficient and the smallest profile of wear scratch owning to the strengthened synergistic effect.
]]>Crystals doi: 10.3390/cryst14040307
Authors: Qianyi Li Feng Liu Yixin Li Jian Yao Jingyu Yang Liming Tan Zi Wang Lan Huang Yong Liu
A study of the hot salt corrosion behavior of three nickel-based single-crystal superalloys at 900 °C was conducted. We discovered that the corrosion layer on each alloy was distinctly enriched with Mo, Ni, S, and O, primarily comprising sulfides and oxides. Notably, variations in oxygen distribution across the alloys revealed that the elemental composition plays a pivotal role in their corrosion resistance. These insights not only advance our understanding of the mechanisms driving thermal corrosion in nickel-based single-crystal superalloys but also lay the groundwork for designing alloys with enhanced durability tailored to high-temperature applications. This research marks a significant step toward the optimal design and utilization of superalloys in sectors demanding exceptional material stability under thermal stress.
]]>Crystals doi: 10.3390/cryst14040306
Authors: Hicham Helal Mohammadi Ahrouch Abdelaziz Rabehi Dario Zappa Elisabetta Comini
Solid oxide fuel cells (SOFCs) have emerged as promising candidates for efficient and environmentally friendly energy conversion technologies. Their high energy conversion efficiency and fuel flexibility make them particularly attractive for various applications, ranging from stationary power generation to portable electronic devices. Recently, research has focused on utilizing nanostructured materials to enhance the performance of SOFCs. This comprehensive review summarizes the latest advancements in the design, fabrication, and characterization of nanostructured materials integrated in SOFC. The review begins by elucidating the fundamental principles underlying SOFC operation, emphasizing the critical role of electrode materials, electrolytes, and interfacial interactions in overall cell performance, and the importance of nanostructured materials in addressing key challenges. It provides an in-depth analysis of various types of nanostructures, highlighting their roles in improving the electrochemical performance, stability, and durability of SOFCs. Furthermore, this review delves into the fabrication techniques that enable precise control over nanostructure morphology, composition, and architecture. The influence of nanoscale effects on ionic and electronic transport within the electrolyte and electrodes is thoroughly explored, shedding light on the mechanisms behind enhanced performance. By providing a comprehensive overview of the current state of research on nanostructured materials for SOFCs, this review aims to guide researchers, engineers, and policymakers toward the development of high-performance, cost-effective, and sustainable energy conversion systems.
]]>Crystals doi: 10.3390/cryst14040305
Authors: Amlan Kar Sribalaji Mathiyalagan Sergey Malopheyev Rustam Kaibyshev Satyam Suwas Satish V. Kailas
In industrial applications, welding of dissimilar metals such as aluminum (Al) and titanium (Ti) is a prerequisite for the development of hybrid components with improved mechanical and corrosion properties. However, dissimilar welding of the Al/Ti system is highly challenging due to differences in the physical and thermal properties of the two materials. In the present investigation, an attempt has been made to fabricate a dissimilar friction stir weld (FSW) of commercially pure Al and Ti and to elucidate the mechanism associated with superior joint formation. The process parameters, such as tool rotation speed, traverse speed and tool offset position have been optimized using Taguchi’s optimization technique. A detailed investigation of the weld with optimum process parameters has been carried out to reveal the mechanism of joint formation. The superior mechanical properties (24% higher ultimate tensile strength and 10% higher ductility than that of base Al) of the weld are attributed to the fabrication of a defect-free joint, formation of intercalated particles and an Al/Ti interlocking interface, homogeneous distribution of fine second-phase (Ti and/or intermetallics) particles in the weld nugget, reduction in the evolution of brittle Al3Ti intermetallic compounds (IMCs) and recrystallization and grain refinement of Al in the weld nugget. The potentio-dynamic polarization test indicated that the optimized Al/Ti weld has ~47% higher corrosion resistance than Al; it had a very mild corrosion attack due to the homogeneous dispersion of fine particles. The method and mechanism could have an immense influence on any dissimilar weld and metal matrix composites, improving their mechanical properties and corrosion resistance.
]]>Crystals doi: 10.3390/cryst14040304
Authors: Fugang Qi Shaoqin Peng Jiachang Bi Shunda Zhang Guanhua Su Peiyi Li Jiahui Zhang Tengteng Zhang Weisong Zhou Ruyi Zhang Yanwei Cao
Barium titanate (BaTiO3) is a promising material for silicon-integrated photonics due to its large electro-optical coefficients, low loss, high refractive index, and fast response speed. Several deposition methods have been employed to synthesize BaTiO3 films. Magnetron sputtering is one of these methods, which offers specific advantages for growing large-scale films. However, there is a scarcity of studies investigating the effect of sputtering target density on the quality of BaTiO3 films. Therefore, this study aims to uncover the effect of sputtering targets on the crystal and electronic structures of epitaxial BaTiO3 thin films. Two BaTiO3 ceramic targets were sintered at different densities by altering the sintering temperatures. The crystal structure and chemical composition of the targets were then characterized using X-ray diffraction, Raman spectroscopy, and scanning electron microscopy with energy-dispersive X-ray spectroscopy. Subsequently, BaTiO3 epitaxial films were grown by magnetron sputtering using these two targets. The crystal and electronic structures of the BaTiO3 films were analyzed using high-resolution X-ray diffraction, X-ray photoemission spectroscopy, atomic force microscopy, and spectroscopic ellipsometry. Notably, the BaTiO3 films grown with high-density targets show superior quality but contain oxygen vacancies, whereas those films synthesized with low-density targets display high surface roughness. These findings provide insights into the effect of sputtering target density on the crystal and electronic structures of epitaxial BaTiO3 thin films.
]]>Crystals doi: 10.3390/cryst14040303
Authors: Koen Faes Rafael Nunes Florian Probst Robin Ceuppens Wim De Waele
The use of additive manufacturing for metallic materials presents a wide range of possibilities for industrial applications. The technology offers several advantages, including weight optimisation and the ability to create complex geometries. However, because of the inherent characteristics of the manufacturing process, the dimensions of the produced objects are frequently constrained. In some cases, it may be necessary to join two additively manufactured parts together or to join such parts with an existing, conventionally manufactured structure. Evaluating welding processes for joining additively manufactured workpieces is a crucial step in this development. In this work, the welding of additively manufactured powder bed fusion 316L stainless steel components is discussed. The welding processes considered are manual TIG, manual and robotic MIG/MAG and laser welding. All optimised welds were of good quality and did not show any weld imperfections. All welds fulfil the requirements of standard ISO 15614-1 for the tensile and bend test results and for the hardness values. It can be concluded that the investigated processes are feasible for welding additively manufactured parts.
]]>Crystals doi: 10.3390/cryst14040302
Authors: Itheereddi Neelakanta Reddy Bhargav Akkinepally Moorthy Dhanasekar Jaesool Shim Cheolho Bai
This study employs a simple and cost-effective technique to enhance the photoelectrochemical (PEC) water-splitting performance of melamine cyanaurate microrods (M), SnO2 nanostructures (S), and melamine cyanaurate microrods decorated with SnO2 quantum dots (MS) by optimizing NaOH and Na2SO3 electrolytes. Notably, the MS electrode demonstrates a remarkable improvement in PEC efficiency in Na2SO3 solution associated with NaOH solution. Specifically, the induced currents of the MS anode in the Na2SO3 electrolyte are approximately 6.28 mAcm−2 more than those observed in the NaOH electrolyte solution. It is revealed that SO32− anions effectively consume the holes, leading to improved separation of the generated charge pairs. This effective charge separation mechanism significantly contributes to the enhanced PEC performance observed in Na2SO3 electrolytes. The findings of this study suggest a capable approach for improving the PEC activity of the materials through the careful optimization of the supported electrolytes.
]]>Crystals doi: 10.3390/cryst14040301
Authors: Ileana Dragutan Fu Ding Yaguang Sun Valerian Dragutan
This Special Issue of Crystals “Multifunctional Coordination Polymers: Synthesis, Structure, Properties and Applications” [...]
]]>Crystals doi: 10.3390/cryst14040300
Authors: Layla Brini Hanen Douiri Marwa Abid Alessandra Toncelli Montasir Qasymeh Ramzi Maalej Mohamed Abdelhedi
In this work, we investigated the potential of Eu3+/Dy3+-codoped Y2Sn2O7 fluorescent nanophosphors to visualize latent fingermarks. We prepared these nanophosphors with various doping concentrations by the conventional coprecipitation reaction. The crystal structure, morphology, luminescence properties, and energy transfer mechanisms were studied. The crystalline phase was characterized by X-ray diffraction and crystal structure refinement using the Rietveld method. XRD measurements showed that the samples crystallized in the pure single pyrochlore phase with few more peaks originated from secondary phases and impurities generated during phosphor production, and that Eu3+ ions occupied D3d symmetry sites. The average crystallite size after mechanical grinding was less than 100 nm for all compositions. The optical characterization showed that, when excited under 532 nm, the Eu3+/Dy3+-codoped Y2Sn2O7 samples’ main intense emission peaks were located at 580–707 nm, corresponding to the 5D0→7Fj (j = l, 2, 3, and 4) transitions of europium. In fact, the 5D0→7F2 hypersensitive transition is strongly dependent on the local environment and was quite weak in Eu3+:Y2Sn2O7 at low Eu3+ doping levels. We found that the presence of Dy3+ as a codopant permitted enhancing the emission from this transition. The calculated PL CIE coordinates for the synthesized nanophosphors were very close to those of the reddish-orange region and only slightly dependent on the doping level. Various surfaces, including difficult ones (wood and ceramic), were successfully tested for latent fingerprint development with the prepared Eu3+/Dy3+-codoped Y2Sn2O7 fluorescent nanophosphor powder. Thanks to the high contrast obtained, fingerprint ridge patterns at all three levels were highlighted: core (level 1) islands, bifurcation, and enclosure (level 2), and even sweat pores (level 3).
]]>Crystals doi: 10.3390/cryst14040299
Authors: Vadla Veenachary Eskilla Venkata Ramana Simhachalam Narendra Babu Venkata Sreenivas Puli Sujoy Saha Gopalan Srinivasan G. Prasad N. V. Prasad
In the present work, we have synthesized rare-earth ion modified Bi4−xRExTi2Fe0.7Co0.3O12−δ (RE = Dy, Sm, La) multiferroic compounds by the conventional solid-state route. Analysis of X-ray diffraction by Rietveld refinement confirmed the formation of a polycrystalline orthorhombic phase. The morphological features revealed a non-uniform, randomly oriented, plate-like grain structure. The peaks evident in the Raman spectra closely corresponded to those of orthorhombic Aurivillius phases. Dielectric studies and impedance measurements were carried out. Asymmetric complex impedance spectra suggested the relaxation of charge carriers belonging to the non-Debye type and controlled by a thermally activated process. Temperature-dependent AC conductivity data showed a change of slope in the vicinity of the phase transition temperature of both magnetic and electrical coupling natures. Based on the universal law and its exponent nature, one can suppose that the conduction process is governed by a small polaron hopping mechanism but significant distortion of TiO6 octahedral. The doping of the A-sites with rare-earth element ions and changes in the concentrations of Fe and Co ions located on the B-sites manifested themselves in saturated magnetic hysteresis loops, indicating competitive interactions between ferroelectric and canted antiferromagnetic spins. The magnetic order in the samples is attributed to pair-wise interactions between adjacent Fe3+–O–Fe3+, Co2+/3+–O–Co3+/2+, and Co2+/3+–O–Fe3+ ions or Dzyaloshinskii–Moriya interactions among magnetic ions in the adjacent sub-lattices. As a result, enhanced magnetoelectric coefficients of 42.4 mV/cm-Oe, 30.3 mV/cm-Oe, and 21.6 mV/cm-Oe for Bi4−xDyxTi2Fe0.7Co0.3O12−δ (DBTFC), Bi4−xLaxTi2Fe0.7Co0.3O12−δ (LBTFC), and Bi4−xSmxTi2Fe0.7Co0.3O12−δ (SBTFC), respectively, have been obtained at lower magnetic fields (<3 kOe). The strong coupling of the Aurivillius compounds observed in this study is beneficial to future multiferroic applications.
]]>Crystals doi: 10.3390/cryst14040298
Authors: Yan Huo Diyuan Guan Lingyan Dong
In this paper, a MANet-based image detection approach is designed to inspect crystal defects during the cooling crystallization process, like that involving β-form L-glutamic acid (LGA), utilizing an online imaging device. The steps in the presented strategy encompass crystal image preprocessing, crystal image segmentation, and crystal classification. Firstly, the guided image filter is introduced to preprocess the collected crystallization images for offline training and online detection. Then, by using an image augmentation strategy to enlarge the number of crystal image samples for training, the MANet-based network is improved for crystal image segmentation. Accordingly, by defining some features, needle-like crystals can be categorized into four types with an efficient classifier for the detection of normal and defective crystals. The experimental results for the batch crystallization of β-form LGA are provided to illustrate the validity of the presented detection methodology.
]]>Crystals doi: 10.3390/cryst14040296
Authors: Juliana G. Maier Tim Fuggerer Daisuke Urushihara Alexander Martin Neamul H. Khansur Ken-ichi Kakimoto Kyle G. Webber
This study investigates the development of freestanding thick films (FSFs) of lead-free (Ba,Ca)(Zr,Ti)O3 and the role of grain growth on the electromechanical response. During deposition, room temperature powder aerosol deposition rapidly produces thick films with a nano-grain structure that limits the electromechanical properties. In this study, the films are removed from the substrate using a sacrificial buffering layer to avoid thermal treatment and allow for an initial as-processed state. Following this, FSFs were thermally treated at various annealing temperatures from 800 °C to 1400 °C to induce grain growth, which was characterized with scanning and transmission electron microscopy. X-ray diffraction revealed an increase in the crystallite size consistent with an increase in grain size and a decrease in internal residual stress. The temperature-dependent dielectric behavior and the large-field ferroelectric response were also characterized, revealing significant differences of the FSFs from the bulk properties.
]]>Crystals doi: 10.3390/cryst14040297
Authors: Serhan Karaman Genc Nilhan Urkmez Taskin
Advanced processing techniques are required to produce functionally graded metal matrix composites due to the metallurgical conditions required during production. In this study, we developed a novel approach for this task by using a combination of two different methods to produce functionally graded 7075 Al/SiCp (5–20 wt.%) composites. The first process was direct semisolid stirring, which was used to prevent particle agglomeration, brittle reaction products, floating or settling of the reinforcements, and poor wettability. The second process was sequential squeeze casting, which enabled liquid diffusion between the two composite layers that were used to produce a functionally graded aluminum matrix composite. Thus, a method was developed to eliminate the problems encountered in the production of particle-reinforced metal matrix composite materials using liquid stirring methods and to produce composite materials with the desired functionally graded structure. The resulting functionally graded material was subjected to spectrometer analyses, density measurements, and metallographic examinations to determine the characteristics of its layers and interfacial zones, as well as to assess the formation of the graded structure. The results indicate the potential of using this new combined manufacturing method, which is efficient and controllable, to produce functionally graded metal matrix composites.
]]>Crystals doi: 10.3390/cryst14040295
Authors: Rashid Dallaev Tomáš Spusta Mohammad M. Allaham Zdenek Spotz Dinara Sobola
This manuscript presents a comprehensive exploration of the band gap structure of (CoCrFeNiMn)3O4 powders through a series of experimental investigations. The combined use of optical techniques and X-ray photoelectron spectroscopy in this study leads to a comprehensive characterization of the band gap structure in (CoCrFeNiMn)3O4 powders. The findings contribute to the understanding of this material’s electronic properties and pave the way for potential applications in electronic and optical devices.
]]>Crystals doi: 10.3390/cryst14040294
Authors: Seong-Min So Srinivasulu Grandhi Eui-Pyo Kwon Min-Suk Oh
Alloy coatings protect steel from corrosion in various applications. We investigated the effects of Si addition on the microstructure, electrochemical behavior, and corrosion resistance of steel sheets coated with a hot-dip Zn–Mg–Al–Si alloy using a batch-type galvanization process. Microstructural analysis revealed that the Zn–Al–Mg alloy coating layer contained a significant amount of Fe that diffused from the substrate, leading to delamination due to the formation of brittle Fe–Zn intermetallic compounds. However, the introduction of Si resulted in the formation of a stable Fe2Al3Si inhibition layer at the substrate–coating interface; this layer prevented interdiffusion of Fe as well as enhanced the coating adhesion. Additionally, the formation of acicular Mg2Si phases on the coating surface improved the surface roughness. As the Si content increased, the corrosion resistance of the coating improved. Specifically, the Zn–Al–Mg coating layer with 0.5 wt.% Si exhibited excellent anti-corrosion performance, without red rust formation on its surface even after 2600 h, during a salt spray test.
]]>Crystals doi: 10.3390/cryst14040293
Authors: Shuai Meng Aocheng Li Kun Li Yanjie Song Zhenxing Qin Rui Zhang Yufei Zhang Weijie Ren Wen Yang
Near-infrared laser radiation based on Nd3+-doped yttrium ortho-aluminate (Nd:YAlO3, Nd:YAP) has garnered significant interest regarding solid-state lasers. Nevertheless, the crystal microstructures and electronic characteristics of Nd:YAP are still unclear, and the unique physical properties underlying its enormous applications require clarification. In this study, we conducted first-principles calculations at the atomic level to explore the electronic properties and mechanical characteristics of both pure YAP and Nd3+-doped YAP. The results suggest that the substitution of the Y3+ ion site with the Nd3+ impurity ion induces slight structural distortion in the YAP crystal lattice. An impurity band emerges between the original conduction band and the valence band, attributed to the 4f orbital of the Nd3+ ion, exerting a substantial influence on the narrowing of the band gap. Through an analysis of the mechanical characteristics of both pure YAP and Nd:YAP, we conclude that the incorporation of Nd3+ atoms leads to a reduction in the mechanical properties of YAP to a certain extent. Our study can serve as a foundational data source for investigations into material performance, especially for the application of Nd:YAP in solid-state laser systems.
]]>Crystals doi: 10.3390/cryst14040292
Authors: Zun Liang Xin Zhang Yashen Wang Songtai Lv Dmitri V. Alexandrov Hongtao Liang Yang Yang
Using the non-equilibrium molecular dynamics (NEMD) simulations and the time-dependent Ginzburg–Landau (TDGL) theory for solidification kinetics, we study the crystal-melt interface (CMI) kinetic coefficients for both the soft-sphere (SS) BCC-melt and the FCC-melt interfaces, modeled with the inverse-power repulsive potential (n=8). The collective dynamics of the interfacial liquids at four equilibrium CMIs are calculated and employed to eliminate the discrepancy between the predictions of the kinetic coefficient using the NEMD simulations and the TDGL solidification theory. The speedup of the two modes of the interfacial liquid collective dynamics (at wavenumbers equal to the principal and the secondary reciprocal lattice vector of the grown crystal) at the equilibrium FCC CMI is observed. The calculated local collective dynamics of the SS BCC CMIs are compared with the previously reported data for the BCC Fe CMIs, validating a hypothesis proposed recently that the density relaxation times of the interfacial liquids at the CMIs are anisotropic and material dependent. With the insights provided by the improved application of the TDGL solidification theory, an attempt has been made to interpret the variation physics of the crystal-structure dependence of the solidification kinetic coefficient.
]]>Crystals doi: 10.3390/cryst14030291
Authors: Aya Jezzini Yujin Chen Anne Davidson Gilles Wallez Tayssir Hamieh Joumana Toufaily
Catalysts enriched in Zinc ferrite (ZFO) were synthesized using coprecipitation and hydrothermal methods. Mixtures of crystalline nanoparticles (ZFO and α-Fe2O3, several allotropic varieties of FeO) were characterized by various techniques such as X-ray diffraction (XRD), transmission electron microscopy (TEM, SEM), N2 sorption, UV-visible spectrophotometry (UV-Vis) and X-ray photoelectron spectroscopy (XPS). After detailed characterizations, the catalytic performance of the solids (1 g/L) in the degradation of amoxicillin (AMX) (10 mg/L) as an antibiotic pollutant in water was evaluated. In addition, we used air as the oxygen source and adjusted the pH to 5.0. Consequently, the catalysts obtained via the hydrothermal method HT-ZFO had a high activity (100% of AMX removal in less than 100 min when an LED (75 W) light was used) compared to a similar mixture of oxides with graphene HT-ZFO-GO (a longer time of 150 min) that was necessary for the complete degradation of AMX. Impregnation with an aqueous solution containing 80 mg of GO obtained using Hummer’s method, reduced into RGO by an ultrasound treatment, enhances the initial reaction rate but is associated with a prolonged time for complete AMX removal (10 ppm in water) that we attribute to its spontaneous corrosion.
]]>Crystals doi: 10.3390/cryst14030290
Authors: Byungil Kang Youngki Lee Jongmin Kim Taekyu Ha Youngjig Kim
Trace elements such as boron (B) and zirconium (Zr) can increase creep resistance in nickel-based superalloys. This study investigates the change of microstructures on the grain boundary (GB) in phase-controlled nickel-based superalloys through the addition of trace elements. The basis alloy without B and Zr has distributed micrometer-sized (Nb, Ti)C and Cr23C6 carbides at the GBs. Zr is detected alongside Nb and Ti within certain (Nb, Ti)C carbides and its addition increases the fraction of (Nb, Ti)C or (Nb, Ti, Zr)C carbides. B affects the formation of precipitates constructed by nanometer-sized precipitates, which are Cr23C6 carbides, Cr23(C, B)6 boro-carbides, and Cr-rich borides, surrounded by γ’ phases. This film structure, which includes nanometer-sized precipitates surrounded by γ’ phases, forms more continuously with the addition of B and Zr. It is constructed with precipitates of (Nb, Ti)C carbides and Cr23(C, B)6 boro-carbides surrounded by γ’ phases. Numerous nanometer-sized precipitates (i.e., (Nb, Ti)C and Cr23(C, B)6) are distributed alternately within the film structure. The effect of the addition of B and Zr is such that nucleation sites of each precipitate are formed simultaneously and alternately along the GBs. The experimental results were discussed by correlating them with the predicted fraction of stable phases depending on the temperatures of these alloys, using the JMatPro program.
]]>Crystals doi: 10.3390/cryst14030289
Authors: Ki Hyun Nam
Proteins can form crystals spontaneously without crystallization experiments. These crystals can be used to determine three-dimensional structures. However, when X-ray diffraction is poor, crystal optimization is required to obtain a high-resolution crystal structure. Endo-1,4-β-xylanase from the fungus Hypocrea virens (HviGH11) spontaneously formed microcrystals after affinity purification and concentration; however, most HviGH11 microcrystals showed poor diffraction in the synchrotron X-ray and X-ray free-electron laser, so a complete three-dimensional structure could not be obtained. This study presents a method to improve the crystal quality of spontaneously grown HviGH11 microcrystals. The crystallization screening results revealed that temperature, pH, and salt were not crucial factors in increasing the solubility or preventing the spontaneous crystal growth of HviGH11. Conversely, the addition of polyethylene glycols (PEGs) as a precipitant facilitated the growth of larger HviGH11 crystals. The improved large HviGH11 crystal showed a diffraction of up to 1.95 Å when exposed to synchrotron X-rays, providing a complete three-dimensional structural dataset. Based on the nucleation rate equation, it was suggested that PEG increases the viscosity of the protein solution rather than promoting nucleation. This increase in viscosity reduced nucleation and facilitated the growth of larger HviGH11 crystals. These results provide valuable insights for future experiments aimed at increasing the size of spontaneously grown crystals.
]]>Crystals doi: 10.3390/cryst14030288
Authors: Ashiwini Balodhi Min Gyu Kim
We report the growth of single crystals and X-ray diffraction characterization of the quasi-one-dimensional spin chain compound, Li2CuO2. The single crystals were grown using the high-temperature solution growth technique. The resulting blade-shaped crystals exhibit a shiny black color, with dimensions reaching several millimeters along the crystallographic b-axis. The as-grown crystals were characterized using powder X-ray diffraction and Laue back reflection. The I-centered orthorhombic, Immm, structure was confirmed. Crystal structure parameters were determined to be a = 3.6744 Å, b = 2.8600 Å, and c = 9.4257 Å from Rietveld analysis. Our work helps to remove obstacles to the synthesis and study of a model cuprate system, Li2CuO2, facilitating the use of experimental probes that require sizable crystals.
]]>Crystals doi: 10.3390/cryst14030287
Authors: Loïc Malet Stéphane Godet
Explaining the crystallography of iron alloys martensite with a {225}γ habit plane remains a challenging task within the phenomenological theory of martensite crystallography. The purpose of this study is to re-examine the martensite formed in a Fe-8Cr-1.1C alloy using EBSD, which has a better angular resolution than the conventional transmission electron diffraction techniques previously used. The results show that the single morphological plates, which hold a near {225}γ habit plane, are bivariant composites made up of two twin-related variants. It is shown that a {113}γ plane is systematically parallel to one of the three common 112α planes between the two twin-related crystals. This observation suggests that the lattice invariant strain of transformation occurs through a dislocation glide on the {113}γ ⟨110⟩γ system, rather than through twinning as is commonly accepted. Based on this assumption, the predictions of Bowles and Mackenzie’s original theory are in good agreement with the crystallographic features of {225}γ martensite. Unexpectedly, it is the high shear solution of the theory that gives the most accurate experimental predictions.
]]>Crystals doi: 10.3390/cryst14030286
Authors: Tayeb Benkouider Yazid Derouiche Lahcene Souli Frédéric Dubois Ana Barrera Zohra Bouberka Ulrich Maschke
The study investigated the effect of the molecular weight of three difunctional poly(propylene glycol) diacrylates on the temperature-dependent ionic conductivity of these monomers and their blends with an eutectic nematic liquid crystal mixture (E7). The results revealed two distinct regions. At low temperatures, ionic conduction can be described by the Vogel–Tamman–Fulcher (VTF) equation, while at high temperatures, the conductivity data follow the prediction of the Arrhenius model. The Arrhenius and VTF parameters and their corresponding activation energies were determined using the least squares method. In addition, a conductivity analysis based on an ionic hopping model is proposed. Estimates of ion concentrations and diffusion constants were calculated. It was found that both the ionic concentration and the diffusion constant decrease with the increase in the molecular weight of the monomers. The static dielectric permittivity decreases in the following order: TPGDA, PPGDA540, and PPGDA900. This can be explained by the higher dipole moment of TPGDA, which is caused by an enhanced volume density of carbonyl groups.
]]>Crystals doi: 10.3390/cryst14030285
Authors: Jeffery Logan Betts Bradley J. Sampson Kyle Lindsey Frank M. Brinkley Matthew W. Priddy
Metal-based additive manufacturing (MBAM) has enabled rapid prototyping and one-off production, but the cost of equipment has limited widespread adoption. Recent developments in hybrid filaments and processes have created more accessible methods for MBAM, leveraging common fused filament fabrication (FFF) printers and Ultrafuse 316L metal filament. This technique has shown promise but suffered from large pore formations along parallel print paths. To reduce the formation of process-dependent pores, a design of experiments (DOE) was conducted to investigate the effects of varying extrusion parameters such as layer height, line width, and extrusion multiplier for tensile samples produced on a Creality Ender 3 V2 and MakerBot Method X. Characterization techniques included tensile testing, microhardness, density measurements, and optical microscopy; findings were compared to samples produced via laser-powder bed fusion (L-PBF) and from 316L plate. The Method X produced components with approximately 1% porosity and the Ender 4% porosity. Mechanical properties for both FFF printers were comparable to previous research, with an increase in tensile strength for the Method X. Despite the increased porosity in the Ender samples, only a 7% reduction in strength from the average yield in Method X samples (153.6 MPa) was observed. It was found that a combination of increased layer height and extrusion rate led to improved mechanical properties in parts printed on the Ender, while the default Makerbot settings resulted in the best overall performance for Ultrafuse 316L samples.
]]>Crystals doi: 10.3390/cryst14030284
Authors: Chenzhe Xu Yue Qiu Xiaoting Yang Zifei Gao Zheng Wang Cai Liu Yanran Sun Juanjuan Ma Lin Liu
In this study, a Pt@Co-Al LDH hybrid structure was fabricated by assembling the metal precursor PtCl62− with the exfoliated LDH nanosheets followed by in situ reduction by NaBH4. The morphology, composition and microstructure of the hybrid were characterized by FESEM, HRTEM, XRD, XPS and BET techniques. Pt nanoparticles (NPs) with an average particle size of 3.1 nm were successfully and uniformly loaded on the surface of LDH nanosheets. The catalytic activity of the Pt@Co-Al LDH hybrid was tested for the reduction of 4-nitrophenol, which is one of the most frequent pollutants in wastewater effluent from the pharmaceutical and textile industries. The hybrid displays superior catalytic activity and stability in the reduction of 4-NP under environmental conditions with NaBH4 as a reducing agent. The hybrid can be recovered in a simple way and still shows high catalytic activity after five reuses.
]]>Crystals doi: 10.3390/cryst14030283
Authors: Bibhu P. Sahu Mohsen T. Andani Arkajit Ghosh Jian Wang Amit Misra
The crystallography of the eutectic Al-Si microstructure in both unmodified and Sr (0.2 wt.%)-modified hypereutectic Al-20 wt.% Si alloys, processed via arc-melting and laser surface remelting, has been comprehensively characterized using transmission electron microscopy and electron diffraction. Although, under as-cast conditions, specific orientations between different planes of Al and Si, satisfying defined orientation relationships (ORs), have been investigated within the flake morphology, the rapid solidification induced by laser surface remelting results in a notable transformation from a flake morphology to nanocrystalline Si fibers dispersed in an Al matrix. Consequently, this transformation results in a mis-orientation of the interface between the eutectic Al and Si phases, preventing the formation of orientation relationships, thus promoting the formation of faceted interfaces exhibiting substantial lattice disregistry.
]]>Crystals doi: 10.3390/cryst14030282
Authors: Weiqiang Pang Victor Abrukov Darya Anufrieva Dongping Chen
There was an error in the original publication [...]
]]>Crystals doi: 10.3390/cryst14030281
Authors: Emily E. Stumbo Emarald K. Hodge Matthew Williams Diana A. Thornton Colin D. McMillen Jared A. Pienkos
The N-oxide functional group has been exploited for synthetic strategies and drug design, and it has been utilized in imaging agents. Herein, we present rare examples of neutral heteroleptic cyclometallated Ir(III) compounds that contain an uncoordinated N-oxide functional group. These species, along with others described within, were verified by NMR, EA, HRMS, and single-crystal X-ray analysis. N-oxide-containing Ir(III) species were prepared selectively in high yields > 66% from chloro-bridged Ir(III) dimers with Acipimox, a picolinate-type ligand containing the N-oxide functional group. Non-N-oxide analogs were synthesized in a similar fashion (yields > 77%). Electrochemical comparison (cyclic voltammetry) indicates that the presence of an N-oxide functional group anodically shifts the reduction potential, suggesting that the N-oxide is acting as an electron-withdrawing group in these species. Crystallographic studies were pursued to examine the coordination behavior of these N-oxides compared to their non-oxidized congeners. The Ir(III) complexes with Acipimox indeed leave the N-oxide uncoordinated and exposed on the complexes. The uncoordinated N-oxide group is influential in directing the packing structures of these complexes directly through C-H···O and O···π interactions at the N-oxide. The crystallographic characterization of cationic Ir(III) compounds with uncoordinated nitrogen atoms is also presented. The C-H···N interactions between these complexes form a variety of dimers, finite chains, and continuous chains. Future work will focus on functionalizing the cationic Ir(III) species into their corresponding N-oxide derivatives and rigorously characterizing how the N-oxide functional group impacts the optical properties of transition metal compounds in both cationic and neutral complexes.
]]>Crystals doi: 10.3390/cryst14030280
Authors: Yang He Xing Su Kuo Hai
The surface of molybdenum disulfide (MoS2) underwent oxygen plasma treatment to enhance its machinability and mitigate the tearing effects commonly associated with mechanical forces on 2D materials. This treatment led to the oxidation of the atoms on the top 1–3 layers of MoS2, resulting in the formation of MoO3 on the surface. During mechanical scanning probe lithography (m-SPL), only the surface oxide layer was uniformly removed, with material accumulation occurring predominantly on one side of the machined area. The resolution of the machining process was significantly enhanced via dynamic lithography while maintaining atomic-level smoothness in the machined area. Importantly, these techniques only removed the surface oxide layer, preserving the integrity of the underlying MoS2 surface, which was pivotal in avoiding damage to the original material structure. This study provided valuable insights and practical guidance for the nanofabrication of transition metal dichalcogenides (TMDCs) nanodevices, demonstrating a method to finely tune the machining of these materials.
]]>Crystals doi: 10.3390/cryst14030279
Authors: Yang Wu Hao Lan Xiaoming Sun Zihao Hu Yonghui Sun Huifeng Zhang Chuanbing Huang Weigang Zhang
HfO2 has become a promising thermal barrier coating material due to its similarity in structure and chemical properties with ZrO2 and its higher phase structure transition temperature. However, the fracture toughness of HfO2 is not ideal, greatly limiting its application. In this report, we find a special sandwich structure of ceramics, comprising a cubic (C) phase /monoclinic (M) phase/cubic (C) phase. The microstructural evolution and mechanical properties of these ceramics were investigated under annealing at 1500 °C. The results indicate that, with an increase in annealing duration, there was a gradual augmentation in the proportion of the monoclinic (M) phase and the fracture toughness increased from 2.18 MPa·m0.5 to 2.83 MPa·m0.5 after 48 h of annealing, which is higher than many potential TBC materials. The residual compressive stress present in the M phases during the progression of crack propagation served to facilitate the bridging and deflection of cracks. As such, this process led to the alleviation of stress concentration at the crack tip, ultimately enhancing the toughening effect.
]]>Crystals doi: 10.3390/cryst14030278
Authors: Yasukazu Kobayashi Koharu Yamamoto Ryo Shoji
Zinc-included intermetallic compound catalysts of RhZn, PtZn, and PdZn with a molar ration of Zn/metal = 1/1, which are generally prepared using a hydrogen reduction approach, are known to show excellent catalytic performance in some selective hydrogenations of organic compounds. In this study, in order to reduce the incorporated mounts of the expensive noble metals, we attempted to prepare zinc-rich intermetallic compounds via a CaH2-assisted molten salt synthesis method with a stronger reduction capacity than the common hydrogen reduction method. X-ray diffraction results indicated the formation of RhZn13 and Pt3Zn10 in the samples prepared by the reduction of ZnO-supported metal precursors. In a hydrogenation reaction of p-nitrophenol to p-aminophenol, the ZnO-supported RhZn13 and Pt3Zn10 catalysts showed a higher selectivity than the RhZn/ZnO and PtZn/ZnO catalysts with the almost similar conversions. Thus, it was demonstrated that the zinc-rich intermetallic compounds of RhZn13 and Pt3Zn10 could be superior selective hydrogenation catalysts compared to the conventional intermetallic compound catalysts of RhZn and PtZn.
]]>Crystals doi: 10.3390/cryst14030277
Authors: Mattia Lopresti Marco Milanesio Luca Palin
In the original publication [...]
]]>Crystals doi: 10.3390/cryst14030276
Authors: Ki Hyun Nam
Temperature directly influences the function and structure of proteins. Crystal structures determined at room temperature offer more biologically relevant structural information regarding flexibility, rigidity, and thermal motion than those determined by conventional cryocrystallography. Crystal structures can be determined at room temperature using conventional macromolecular crystallography (MX) or serial crystallography (SX) techniques. Among these, MX may theoretically be affected by radiation damage or X-ray heating, potentially resulting in differences between the room temperature structures determined by MX and SX, but this has not been fully elucidated. In this study, the room temperature structure of xylanase GH11 from Thermoanaerobacterium saccharolyticum was determined by MX (RT-TsaGH11-MX). The RT-TsaGH11-MX exhibited both the open and closed conformations of the substrate-binding cleft within the β-sandwich fold. The RT-TsaGH11-MX showed distinct structural changes and molecular flexibility when compared with the RT-TsaGH11 determined via serial synchrotron crystallography. The notable molecular conformation and flexibility of the RT-TsaGH11-MX may be induced by radiation damage and X-ray heating. These findings will broaden our understanding of the potential limitations of room temperature structures determined by MX.
]]>Crystals doi: 10.3390/cryst14030275
Authors: Sangmoon Yoon
Recent advancements in electron detectors and computing power have revolutionized the rapid recording of millions of 2D diffraction patterns across a grid of probe positions, known as four-dimensional scanning transmission electron microscopy (4D-STEM). These datasets serve as the foundation for innovative STEM imaging techniques like integrated center of mass (iCOM) and symmetry STEM (S-STEM). This paper delves into the application of 4D-STEM datasets for diffraction analysis. We therefore use the term scanning electron diffraction (SED) instead of 4D-STEM in this review. We comprehensively explore groundbreaking diffraction methods based on SED, structured into two main segments: (i) utilizing an atomic-scale electron probe and (ii) employing a nanoscale electron probe. Achieving an atomic-scale electron probe necessitates a significant convergence angle (α > 30 mrad), leading to interference between direct and diffracted beams, distinguishing it from its nanoscale counterpart. Additionally, integrating machine learning approaches with SED experiments holds promise in various directions, as discussed in this review. Our aim is to equip materials scientists with valuable insights for characterizing atomic structures using cutting-edge SED techniques.
]]>Crystals doi: 10.3390/cryst14030274
Authors: Jianxian Wen Xiaoyun Song Yanfeng Li Shuwei Liu Yang Yu Wenjun Ye Songxiao Hui
The effect of annealing treatment on the microstructure and texture of a Ti50Ni47Fe3 shape memory alloy tube was studied. The results show that the recrystallization process of a cold-rolled Ti50Ni47Fe3 alloy tube occurs at 600 °C. The microstructure changes from long striped grains to equiaxed recrystallized grains. The main texture of the alloy tube is the fiber texture <111> parallel to RD. With the increase in the annealing temperature, the crystal orientation of the alloy gradually turned to (111)<112>, and a series of secondary textures were distributed along the γ orientation line when the alloy was annealed at a lower temperature (450~600 °C). When the alloy was annealed at 650 °C, the growth of recrystallized grains made the grain orientation change, which led to the weakening of the γ-fiber texture and the formation of recrystallization textures.
]]>Crystals doi: 10.3390/cryst14030273
Authors: Jiansong Zhang Yuzhu Zhang Yue Long Peipei Du Tielei Tian Qianqian Ren
Multi-source ferrous metallurgical dust and sludge are significant components of iron-containing solid waste in the iron and steel industry. It is crucial for the sustainable operation of steel enterprises to recycle iron from ferrous metallurgical dust and sludge (FMDS) for use in steel smelting. However, besides Fe, FMDS also contains valuable elements such as Zn, Pb, K, and Na, among others. While these valuable elements hold high recovery value, they impede the direct reuse of FMDS by iron and steel enterprises. This paper introduces the compositional characteristics of multi-source ferrous metallurgical dust and sludge, analyzes the main recycling technologies associated with FMDS at the present stage of development, and discusses the characteristics of different technologies. In view of this, a new idea of the “cooperative treatment of multi-source ferrous metallurgical dust and sludge—full quantitative recovery of valuable elements” is put forward. This new idea integrates a variety of treatment processes to directly recycle FMDS within the steel plant, enhancing the adequacy of dust and sludge recovery and reducing the risk of environmental pollution. This paper provides a reference for achieving the full quantification and utilization of high-value-added FMDS in steel plants.
]]>Crystals doi: 10.3390/cryst14030272
Authors: Vadym Borysiuk Iakov A. Lyashenko Valentin L. Popov
We report the results of atomistic simulations of friction between two-dimensional titanium carbide Ti2C (MXene) and a silver nanoparticle located on its surface. Numerical experiments were performed within classical molecular dynamics methods using a previously developed scheme for simulations of interactions between MXenes and metal nanoparticles. In the computer experiments performed, both tangential and shear forces were applied to the Ag nanoparticle to initiate its sliding on the surface of the Ti2C MXene. During the simulations, the nanotribological parameters of the studied system, such as the friction force, contact area, friction coefficient, and tangential shear, were computed. It is shown that, for the studied system, the friction coefficient does not depend on the velocity of nanoparticle movement or the contact area. Additionally, the sliding friction of the nanoparticle on the flexible substrate was considered. The latter case is characterized by a larger friction coefficient and contact area due to the formation of wrinkles on the surface of the substrate.
]]>Crystals doi: 10.3390/cryst14030271
Authors: Taehong Park Sunho Lee Dong-Min Kim
As the demand for battery technology with enhanced safety and high energy density increases, solid-state batteries are currently attracting attention as a solution to problems such as fire and explosion risks associated with lithium-ion batteries. In this study, experiments were conducted to synthesize and optimize Li7La3Zr2O12 (LLZO), a solid electrolyte that is a key component of lithium-ion batteries with stability and high energy density. Experimental results showed that sintering at a low temperature of 800 °C for 8 h was the optimal synthesis and sintering time. Additionally, the excess lithium-containing bed powder enabled the production of pure cubic-phase LLZO. Through a sintering process that creates a lithium atmosphere on the bottom surface and facilitates lithium replenishment, an additional tunnel was introduced between the specimen and the alumina powder, allowing the bottom surface of the specimen to be exposed to the lithium atmosphere. By manufacturing a uniform cubic electrolyte, the path to manufacturing all-solid-state batteries was opened. These findings provide a new approach to forming cubic-phase LLZO with much higher ionic conductivity than the tetragonal phase at low sintering temperatures.
]]>Crystals doi: 10.3390/cryst14030270
Authors: Maria Roslova Bernd Büchner Andrey Maljuk
In this review, we summarize recent progress in crystal growth and understanding of the influence of crystal structure on superconductivity in pure and Pb-doped Bi2Sr2CuOy (Bi-2201) materials belonging to the overdoped region of high-temperature cuprate superconductors. The crystal growth of Bi-2201 superconductors faces challenges due to intricate materials chemistry and the lack of knowledge of corresponding phase diagrams. Historically, a crucible-free floating zone method emerged as the most promising growth approach for these materials, resulting in high-quality single crystals. This review outlines the described methods in the literature and the authors’ synthesis endeavors encompassing Pb-doped Bi-2201 crystals, provides a detailed structural characterization of as-grown and post-growth annealed samples, and highlights optimal growth conditions that yield large-size, single-phase, and compositionally homogeneous Bi-2201 single crystals.
]]>Crystals doi: 10.3390/cryst14030269
Authors: Xiangxia Kong Junjun Zhai Ruipeng Ma Fenglian Sun Xuemei Li
Sn58Bi solder is considered a promising lead-free solder that meets the performance requirements, with the advantages of good wettability and low cost. However, the low melting point characteristic of Sn58Bi poses a serious threat to the high-temperature reliability of electronic products. In this study, Sn58Bi solder alloy based on nickel (Ni) functionalization was successfully synthesized, and the effect of a small amount of Ni on creep properties and hardness of Cu/Sn58Bi/Cu micro solder joints at different temperatures (25 °C, 50 °C, 75 °C, 100 °C) was investigated using a nanoindentation method. The results indicate that the nanoindentation depth of micro solder joints exhibits a non-monotonic trend with increasing Ni content at different temperatures, and the slope of the indentation stage curve decreases at 100 °C, showing that the micro solder joints undergo high levels of softening. According to the observation of indentation morphology, Ni doping can reduce the indentation area and accumulation around the indentation, especially at 75 °C and 100 °C. In addition, due to the severe creep phenomenon at 100 °C, the indentation hardness rapidly decreases. The indentation hardness values of micro solder joints of Cu/Sn58Bi/Cu, Cu/Sn58Bi-0.1Ni/Cu, and Cu/Sn58Bi-0.2Ni/Cu at 100 °C are 14.67 ± 2.00 MPa, 21.05 ± 2.00 MPa, and 20.13 ± 2.10 MPa, respectively. Nevertheless, under the same temperature test conditions, the addition of Ni elements can improve the high-temperature creep resistance and hardness of Cu/Sn58Bi/Cu micro solder joints.
]]>Crystals doi: 10.3390/cryst14030268
Authors: Vera M. Kalygina Alexander V. Tsymbalov Petr M. Korusenko Aleksandra V. Koroleva Evgeniy V. Zhizhin
Resistive metal/β-Ga2O3/metal structures with different interelectrode distances and electrode topologies were investigated. The oxide films were deposited by radio-frequency magnetron sputtering of a Ga2O3 (99.999%) target onto an unheated sapphire c-plane substrate (0001) in an Ar/O2 gas mixture. The films are sensitive to ultraviolet radiation with wavelength λ = 254. Structures with interdigital electrode topology have pronounced persistent conductivity. It is shown that the magnitude of responsivity, response time τr, and recovery time τd are determined by the concentration of free holes p involved in recombination processes. For the first time, it is proposed to consider hole trapping both by surface states Nts at the metal/Ga2O3 interface and by traps in the bulk of the film.
]]>Crystals doi: 10.3390/cryst14030267
Authors: Tim Freund Sumbal Jamshaid Milad Monavvar Peter Wellmann
Current research efforts in the field of the semiconducting chalcogenide perovskites are directed towards the fabrication of thin films and subsequently determine their performance in the photovoltaic application. These efforts are motivated by the outstanding properties of this class of materials in terms of stability, high absorption coefficient near the band edge and no significant health concerns compared to their halide counterparts. The approach followed here is to use stacked precursor layers and is adopted from other chalcogenide photovoltaic materials like the kesterites and chalcopyrites. The successful synthesis of BaZrS3 from stacked layers of BaS and Zr and annealing at high temperatures (~1100 °C) with the addition of elemental sulfur is demonstrated. However, the film shows the presence of secondary phases and a flawed surface. As an alternative to this, BaS3 could be used as precursor due to its low melting point of 554 °C. Previously, the fabrication of BaS3 films was demonstrated, but in order to utilize them in the fabrication of BaZrS3 thin films, their microstructure and processing are further improved in this work by reducing the synthesis temperature to 300 °C, resulting in a smoother surface. This work lays the groundwork for future research in the fabrication of chalcogenide perovskites utilizing stacked layers and BaS3.
]]>Crystals doi: 10.3390/cryst14030266
Authors: Saima Hafeez Jianguo Yu Fahim Aziz Umrani Wang Yun Muhammad Ishfaq
Multifunctional integrated meta-devices are the demand of modern communication systems and are given a lot of attention nowadays. Most of the research has focused on either cross-polarization conversion (CPC) or linear-to-circular (LP–CP) conversion. However, simultaneously realizing multiple bands with good conversion efficiency remains crucial. This paper proposes a multiband and multifunctional dual reflective polarization converter surface capable of converting a linearly polarized (LP) wave into a circularly polarized (CP) wave, in frequency bands of 12.29–12.63 GHz, 16.08–24.16 GHz, 27.82–32.21 GHz, 33.75–38.74 GHz, and 39.70–39.79 GHz, with 3 dB axial ratio bandwidths of 2.7%, 40.15%, 14.6%, 13.76%, and 0.2%, respectively. Moreover, the converter is capable of achieving CPC with a polarization conversion ratio (PCR) that exceeds 95%, within the frequency ranges of 13.10–14.72 GHz, 25.43–26.00, 32.46–32.56 GHz, and 39.14–39.59 GHz. In addition, to identify the fundamental cause of the CPC and LP–CP conversion, a comprehensive theoretical investigation is provided. Furthermore, the surface current distribution patterns at different frequencies are investigated to analyze the conversion phenomena. A sample prototype consisting of 20 × 20 unit cells was fabricated and measured, verifying our design and the simulated results. The proposed structure has potential applications in satellite communications, radar, stealth technologies, and reflector antennas.
]]>Crystals doi: 10.3390/cryst14030265
Authors: Yuhan Wang Qing He Zhi Xie
Primary dendrite information is one of the most important metrics to measure the quality of continuous cast slabs. The contrast of low magnification images is very low under the influence of illumination and sampling devices, so the traditional dendrite detection method has the problem of missed detections. We propose an automatic dendrite detection method based on an improved Hough transform, which effectively improves the accuracy and efficiency of primary dendrite detection. By using the local grayscale features of the image, a genetic algorithm-based local contrast enhancement algorithm is proposed. Compared with the traditional contrast enhancement algorithm, it can retain all the information of the dendrites. Combined with the image binarization method based on Hessian matrix, we can obtain more detailed information about the dendrites. According to the continuity and solidification characteristics of dendrites, the Hough transform is improved to extract dendrite information, which effectively reduces the computational cost of the Hough transform. The experimental results show that the method of this paper has versatility, and the error is four pixels compared with the manual method, which can provide a reliable basis for the subsequent judgement of the quality of cast billets.
]]>Crystals doi: 10.3390/cryst14030264
Authors: Maarten R. van Delft Sergio Pezzini Markus König Paul Tinnemans Nigel E. Hussey Steffen Wiedmann
In the original publication [...]
]]>Crystals doi: 10.3390/cryst14030263
Authors: Jáchym Lis Jakub Skočdopole Petr Jaroš Jiří Čapek Karel Trojan Martin Dráb Monika Kučeráková Stanislav Vratislav Ladislav Kalvoda
Investigation of high-entropy alloys in form of bulk samples as well as thin films is currently one of the fastest growing areas in the study of metal alloys. In this paper, a bulk sample of FeNiCoCuCr high-entropy alloy ingot with equimolar composition is prepared by the laboratory arc melting method under an argon atmosphere and used as a source target for deposition of thin films on Si (111) single-crystalline substrates using a novel ionized jet deposition method. The morphology, chemical composition, and real crystalline structure of the target and the prepared layers were characterized by scanning electron microscopy, atomic force microscopy, energy-dispersive X-ray spectroscopy, and X-ray and neutron diffraction methods. Transfer coefficients characterizing the mass transport between the target and the grown film were calculated for each of the constituting metallic elements as the ratio of the atomic concentration found in the prepared film divided by its concentration in the deposition target. The dependence of the obtained transfer coefficients on the IJD acceleration voltage is discussed with respect to the main physical and geometric parameters of the deposition process, and their correlations with the cohesive energy of the elements forming the HEA are proposed.
]]>Crystals doi: 10.3390/cryst14030262
Authors: Christopher Hale Zhigang Xu Svitlana Fialkova Jessica Rawles Jagannathan Sankar
Magnesium-based alloys show significant promise for widespread applications owing to their lightweight nature and improved mechanical properties achieved through grain refinement via hot rolling. This investigation focuses on Mg-xAl-yCa-zMn (AXM alloys), pre-heated to temperatures of 350, 400, and 450 °C and processed via both single-pass differential speed rolling (DSR) and conventional rolling (CR). The key findings reveal the interplay between processing temperature, strain rate during single-pass rolling, and an innovative approach for incorporating varying amounts of Ca, influencing grain size, quantity of dynamic recrystallization (DRX) grains, and overall mechanical properties, including strength and ductility. A noteworthy observation is the positive correlation between an increase in the total reduction during hot rolling and a higher fraction of DRXed grains. This leads to a significant reduction in average grain size, diminishing from 60.3 ± 54.3 μm to 19.5 ± 14.2 μm at 40%, nearly a third the size of T4 grains (the initial homogenized microstructure of the AXM alloys). The resultant material strength experiences a doubling from an average of 125 ± 10.2 MPa (T4) to 260 ± 25.8 MPa (DSR rolled at 40%) for the AXM alloys with potential improvement in the ductility depending on rolling speed conditions. This study also aims to analyze the combination of rolling temperature, rolling speed, thickness reduction, speed difference and Ca content implemented across a wide range of temperatures and strain rates to provide a holistic approach to the processing parameters affecting the microstructure and mechanical properties of AXM alloys. Furthermore, this study provides a deeper understanding of DRX mechanisms, including continuous DRX (CDRX), discontinuous DRX (DDRX), and twinning induced DRX (TDRX), while each of these mechanisms plays a distinct role in the overall enhancement of formability and performance of magnesium alloys.
]]>Crystals doi: 10.3390/cryst14030261
Authors: Vediyappan Thirumal Palanisamy Rajkumar Jin-Ho Kim Bathula Babu Kisoo Yoo
A heightened interest in developing MXene (Ti3C2Tx) for energy storage is evident in binder-free MXene ink being directly applied to current collector Ni-foam. Moreover, 2D titanium carbide MXene, with a few layers of nanostructure, has been prepared for symmetric supercapacitor device applications. As-prepared MXene nanosheets exist in two forms: dried powder and ink, achieved through wet-chemical etching and dimethyl sulfoxide delamination from the MAX (Ti3AlC2) phase. This comparative study of electrode devices involves (i) MX-dry powder with binder/additive electrodes and (ii) binder-free MXene inks with directly applied MX-conductive inks. The surface morphological images of pure MX-powder/ink display few layers, and material analysis reveals the good crystalline nature of delaminated MXene (Ti3C2Tx) inks. The electrochemical symmetric supercapacitor device performances of pure MXene powder and binder-free directly applied/coated MXene (Ti3C2Tx) ink, in terms of cyclic voltammetry (CV) and impedance spectroscopy (EIS), exhibit galvanostatic charge–discharge (GCD) curves that show high specific capacitance (Csp) at 105.75 F/g at a current density of 1 A/g. A comparison of active material electrodes demonstrated excellent cycle stability. Hence, in this work, we confirmed the superior capacitive behavior of binder-free MXene ink (MX-I) compared to conductive additives with polymeric binders included in MXene electrodes.
]]>Crystals doi: 10.3390/cryst14030260
Authors: Iñigo Santos-Pereda Virginia Madina Elena Rodriguez Jean-Baptiste Jorcin Esther Acha
In the present work, we studied whether the exposure of synthetic seawater with anaerobic sulphate-reducing bacteria (SRB) on some steel samples generates a bacterial biofilm in their surfaces. Bare steel belonging to a mooring chain as well as two coating systems applied on the steel surface were studied: polyurethane (PU) and thermally sprayed aluminium (TSA) with and without an epoxy-based sealant. After 30 days of immersion in SRB-inoculated synthetic seawater, a bacterial count was attained, and the samples were observed using scanning electron microscopy (SEM) and locally analysed using X-ray scattered energy spectroscopy (EDS). A biofilm developed on every tested surface (continuous or in the form of pustules), with evidence of metabolic activity of the SRB. Finally, a mechanism of degradation for TSA in the presence of SRB is proposed for environments with a high concentration of bacteria.
]]>Crystals doi: 10.3390/cryst14030259
Authors: Guillaume Bastien Cécile Mézière Patrick Batail Denis Gindre
We present a novel approach to second harmonic microscopy combining variable temperature and photon counting. This innovative method aims to generate Second Harmonic Generation (SHG) images by scanning the same area multiple times with short pixel dwell times and low excitation intensities, as illustrated by imaging the full extent of a single crystalline rod of (1,4-bis((4′-(iodoethynyl)phenyl) ethynyl) bicyclo[2.2.2]octane (BCO). Remarkably, this new technique records the change in SHG intensity that occurs along with the crystalline phase transition at 108 K, thereby showing great promise in exploring the intricate instabilities of rotator dynamics concealed within the phase diagrams of molecular machines. Notably, our findings reveal a sustained decrease in non-linear optical intensity as the temperature drops to 95 K, followed by a sharp increase in SHG intensity at approximately 108 K, in synchronicity with the phase transition reported earlier that involves an intricate set of concerted changes in rotor dynamics.
]]>Crystals doi: 10.3390/cryst14030258
Authors: Yanjie Huang Kanghua Chang Jie Yao Xueyong Guo Chen Shen Shi Yan
To enhance both the mechanical properties of hydroxyl-terminated polybutadiene (HTPB) binder and the combustion efficiency of aluminized propellants, 2,2,3,3,4,4,5,5-octafluoro-1,6-hexanediol (OFHD) was employed as a chain extender to impart mechanical regulation to the HTPB binder. Mechanical testing showed that the mechanical properties of fluoride-modified HTPB polyurethane (FPU) were significantly improved: the peak tensile strength of the optimized samples reached 1.99 MPa, and the elongation at break attained 486%. The structural characterization of the FPUs was conducted using Fourier transform infrared (FTIR) spectroscopy. Thermogravimetry-mass spectrometer (TG-MS) analysis revealed that the initial thermal decomposition temperature of the FPU shifted from 170 °C to 162 °C, accompanied by the release of fluorine-containing fragments during decomposition. Analysis of the combustion residue indicated that the addition of OFHD can reduce the agglomeration of aluminum (Al) powder in aluminized propellants. Dynamic pressure characteristics results showed an augmented pressurization rate under argon and oxygen atmospheres, increased by 18.67% and 37.29%, respectively. Heat release tests indicated that the aluminized propellants with the addition of OFHD had a higher combustion heat, being increased by 6.57%. The binder system is expected to be applied in aluminized propellants to improve the mechanical properties and combustion efficiency of Al powder.
]]>Crystals doi: 10.3390/cryst14030257
Authors: Justyna Baranowska Łukasz Szeleszczuk
Novel antiepileptic drugs have been developed at an unparalleled rate during the past 15 years. Gabapentin (GBP), which was approved for the treatment of refractory localization-related epilepsies in the U.K. and Europe in 1993, was one of the first drugs to come out of this era. Since then, GBP has become well-known across the world, not only for its antiepileptic qualities but also for its effectiveness in the treatment of chronic pain disorders, particularly neuropathic pain. In this review, the crystal structures of GBP and GBP-related compounds have been analyzed and compared. Particular attention has been paid to the polymorphism of GBP and its hydrates, their thermodynamic stability, and conformational differences. In addition, the puckering parameters for the cyclohexane ring of a total of 118 molecules of GBP found in the analyzed crystal structures have been calculated and analyzed. The results of recent high-pressure crystallization studies and quantum chemical calculations indicate that the entire landscape of GBP has not been revealed yet.
]]>Crystals doi: 10.3390/cryst14030256
Authors: Michael J. Campbell Daniel A. Decato Chun Li Matthew J. Weaver Nicholas R. Natale
In pursuit of unsymmetrical precursors for the novel series of anthracenyl-isoxazole amide (AIM) antitumor agents, a series of substituted anthracenes were subjected to bromination and re-aromatization in our study, during which we solved four single crystal X-ray diffractometry (Sc-xrd) structures which we report herein. The C-9 nitrile oxide, after its reaction with bromine, was isolated, but when subjected to re-aromatization, it returned to the starting 10-bromo nitrile oxide 1, which did provide an accurate crystal structure, with R = 0.018. The 10-halogenated 3-(9’-anthryl)-isoxazole esters were subjected to bromination and re-aromatization. Surprisingly, the yields obtained in the presence of the isoxazole were reasonably good (62–68% isolated yields), and the major diastereomers allowed for the characterization using Sc-xrd. The penta bromo product 2 showed a trans, trans, cis relationship for the four bromines on the A-ring of the anthracene, and we observed that for the unit cell, the atropisomers displayed a 1:1 ratio at the chiral axis between the isoxazole and anthrancene rings. Similarly, the 10-chloro 3 indicated a ratio of 1:1 at the chiral axis in the crystal structure. A base-induced re-aromatization afforded 3,10-dihalogenated analogues selectively in very good yields (X = Cl, 89%; X = Br 92%), of which the dibromo 4 was characterized using Sc-xrd. The improved yields of the unique diastereomeric bromination products suggested the consideration of a novel electrophilic aromatic substitution mechanism driven by the stereo-electronic environment, imposed by the isoxazole ester substituent. The promise of the application of this chemistry in the future development of AIM antitumor agents is suggested.
]]>Crystals doi: 10.3390/cryst14030255
Authors: Akiko Hori Reo Ichisugi Daiki Azegami Naoki Toyama Hidetaka Yuge
Two molecular structures of a complex C26H16Cl2N2Pd (1) with a benzene hemisolvate (1•0.5C6H6) and a complex C34H20Cl2N2Pd (2) revealed similar conformations: one side of the arylethynyl group is flat to the bipyridine plane while the other side of the arylethynyl group is highly twisted to the plane because rhomb-like dimer fragments are formed between respective two complexes through CH⋯π interactions. The Hirshfeld surface analysis indicates that the most important contributions for the crystal packing of 1 are from H⋯H (33.6%), C⋯H/H⋯C (28.3%), Cl⋯H/H⋯Cl (17.8%), and C⋯C (10.6%) interactions and those of 2 are from H⋯H (36.5%), C⋯H/H⋯C (26.0%), Cl⋯H/H⋯Cl (15.7%), and C⋯C (12.3%) interactions, indicating the remarkable CH⋯π and electron distribution of molecules by Cl ions. The benzene solvate molecule of 1•0.5C6H6 performs to fill the internal space instead of the naphthyl group. Detailed crystallographic and DFT studies were performed to understand the molecular structures and the corresponding supramolecular associations.
]]>Crystals doi: 10.3390/cryst14030254
Authors: Sara Calistri Alessandro Gessi Giuseppe Marghella Stefania Bruni Alberto Ubaldini
Ag2MoO4 crystals were prepared by a precipitation method by mixing parent solutions of silver nitrate and sodium molybdate. The effects of experimental parameters such as temperature, concentration, and pH were studied. The samples were found to be crystalline, pure, and monophasic in all cases, except in the case of very low pH. The precipitation leads to the formation of the cubic phase β and no secondary phase is present within the limits of detection of XRD and Raman spectroscopy. However, in some cases, at high temperature and high pH, silver oxide nanoparticles form on the surfaces of the crystals, which create a fluorescence background in the Raman spectra, which is otherwise absent. Analyses with the electron microscope have highlighted that the most common crystalline shape is octahedral, which is the most prevalent at low temperatures and pH around 7, but others are also possible, in particular at high temperatures. No growth occurs after precipitation, so crystals with different appearances form at the same time.
]]>Crystals doi: 10.3390/cryst14030253
Authors: Bohan Guo Guohao Yu Li Zhang Jiaan Zhou Zheming Wang Runxian Xing An Yang Yu Li Bosen Liu Xiaohong Zeng Zhongkai Du Xuguang Deng Zhongming Zeng Baoshun Zhang
This article presents the utilization of the chemical–mechanical polishing (CMP) method to fabricate high-performance N-polar GaN/AlGaN metal–insulator–semiconductor high-electron-mobility transistors (MIS-HEMTs) through layer transfer technology. The nucleation and buffer layers were removed via CMP to attain a pristine N-polar GaN surface with elevated smoothness, featuring a low root-mean-square (RMS) roughness of 0.216 nm. Oxygen, carbon, and chlorine impurity elements content were low after the CMP process, as detected via X-ray photoelectron spectroscopy (XPS). The electrical properties of N-polar HEMTs fabricated via CMP exhibited a sheet resistance (Rsh) of 244.7 Ω/sq, a mobility of 1230 cm2/V·s, and an ns of 2.24 × 1013 cm−2. Compared with a counter device fabricated via inductively coupled plasma (ICP) dry etching, the CMP devices showed an improved output current of 756.1 mA/mm, reduced on-resistance of 6.51 Ω·mm, and a significantly reduced subthreshold slope mainly attributed to the improved surface conditions. Meanwhile, owing to the MIS configuration, the reverse gate leakage current could be reduced to as low as 15 μA/mm. These results highlight the feasibility of the CMP-involved epitaxial layer transfer (ELT) technique to deliver superior N-polar GaN MIS-HEMTs for power electronic applications.
]]>Crystals doi: 10.3390/cryst14030252
Authors: Mohamed Khitouni Joan-Josep Suñol
This Special Issue entitled “Magnetic, Dielectric, Electrical, Optical and Thermal Properties of Crystalline Materials” is devoted to a general overview of the subject of crystalline materials and may extend to the nanocrystalline field [...]
]]>Crystals doi: 10.3390/cryst14030251
Authors: Bernardo A. Nogueira Chiara Castiglioni
One of the biggest challenges in the field of material science lies in understanding the structure and behavior of crystalline materials and nanostructures [...]
]]>Crystals doi: 10.3390/cryst14030250
Authors: Gheorghe Bădărău Mihai Popa George Stoian Ana-Maria Roman Radu-Ioachim Comăneci Bogdan Pricop Nicanor Cimpoeșu Leandru-Gheorghe Bujoreanu
The paper analyzes the occurrence of evenly spaced cracks on the surface of lamellar specimens of Fe-28Mn-6Si-5Cr (mass %) shape-memory alloy (SMA), during cold rolling. The specimens were hot rolled and normalized and developed cold rolling cracks with an approximate spacing of about 1.3 mm and a depth that increased with the thickness-reduction degree. At normalized specimens, X-ray diffraction patterns revealed the presence of multiple crystallographic variants of brittle α′ body-bcc martensite, which could be the cause of cold-rolling cracking. Both normalized and cold-rolled specimens were analyzed using scanning electron microscopy SEM. SEM micrographs revealed the presence of several crystallographic variants of α′-body-centered cubic (bcc) and ε hexagonal close-packed (hcp) martensite plates within a γ-face-centered cubic (fcc) austenite matrix in a normalized state. High-resolution SEM, recorded after 25% thickness reduction by cold-rolling, emphasized the ductile character of the cracks by means of an array of multiple dimples. After additional 33% cold-rolling thickness reduction, the surface of crack walls became acicular, thus revealing the fragile character of failure. It has been argued that the specimens cracked in the neutral point but preserved their integrity owing to the ductile character of γ-fcc austenite matrix.
]]>Crystals doi: 10.3390/cryst14030249
Authors: Ana Mouquinho Maria Teresa Barros João Sotomayor
This study delved into the correlation between the chain length of PEG polymerizable oligomers and the electro-optical properties exhibited by the resultant PDLC films. A range of di(meth)acrylate oligomers derived from polyethylene glycol with varying molecular weights (Mn = 1000, 2000, 4000, and 6000 g mol−1) was synthesized for incorporation as the polymer matrix in PDLC devices. Comprehensive analyses employing 1H-NMR, 13C-NMR, and MALDI-TOF mass spectroscopy were conducted to validate the structure and purity of the synthesized products. The investigation revealed a significant influence of pre-polymer molecular chain length on the thermal properties of the polymer, including amorphousness and crystallinity, which in turn impact the permanent memory effect. Specifically, it was observed that amorphous PEG polymers serve as an ideal matrix for fostering the permanent memory effect in PDLCs. Among the polymerizable PEG oligomers examined, those with a molecular weight of 1000 g/mol yielded polymer chains existing in an amorphous state, exhibiting a glass transition temperature lower than room temperature (−50 °C). This characteristic imparts flexibility and mobility to the polymer matrix chains, facilitating a 37% permanent memory effect. Conversely, longer polymer chains lead to the formation of crystal aggregates, resulting in semi-crystalline polymer matrices. This reduces the malleability of the polymer chains, thereby nullifying the permanent memory effect in the corresponding PDLC devices.
]]>Crystals doi: 10.3390/cryst14030248
Authors: Renny Maria Losus Simran Chaudhary Liliana Dobrzańska
A series of new Ag(I) complexes with 2,6-bis[(imidazol-2-yl)thiomethyl]naphthalene (L) and a range of counterions (X−) such as PF6− (1, 2), SbF6− (3), and CF3SO3− (4) was prepared. As shown by SCXRD studies, all of these are 1D coordination polymers with a waved chain motive and general formula {[AgL]X}n. Two methanol solvates containing PF6− (1) and SbF6− (3) counterions are isostructural. The triflate counterion leads to the formation of a topologically equivalent structural motive, with a different conformation of the ligand in the 1D chain and a different crystal packing as a result of the presence of another set of intermolecular interactions. The presence of water in 2 leads to a significant change in the conformation of the ligand. The naphthalene rings show a different orientation towards the imidazole rings, which is energetically less favorable but is stabilized by an extended net of intermolecular interactions with the counterion, which leads to an efficient crystal packing.
]]>Crystals doi: 10.3390/cryst14030247
Authors: Yin-Pai Lin Elina Neilande Hanna Bandarenka Siarhei Zavatski Inta Isakoviča Sergei Piskunov Dmitry Bocharov Eugene A. Kotomin
Excited state calculations are performed to predict the electronic structure and optical absorption characteristics of Cu-doped anatase TiO2 nanofilms, focusing on their (101) and (001) surface terminations. Using model structures that successfully represent the equilibrium positions of deposited Cu atoms on the TiO2 surface, a comprehensive analysis of the absorption spectra for each considered model is made. The proposed modeling reveals phenomena when photogenerated electrons from TiO2 tend to accumulate in the vicinity of the deposited Cu atoms exposed to photon energies surpassing the band gap of TiO2 (approximately 3.2 eV). The crucial transition states that are essential for the creation of potential photocatalytic materials are identified through detailed calculations of the excited states. These insights hold substantial promise for the strategic design of advanced photocatalytic materials. The obtained results provide a base for subsequent analyses, facilitating the determination of heightened surface reactivity, photostimulated water splitting, and antibacterial properties.
]]>Crystals doi: 10.3390/cryst14030246
Authors: Stavroula Maritsa Stavros Deligiannis Petros E. Tsakiridis Anna D. Zervaki
The Laser Beam Welding (LBW) of aluminum alloys has attracted significant interest from industrial sectors, including the shipbuilding, automotive and aeronautics industries, as it expects to contribute to significant cost reduction associated with the production of high-quality welds. To comprehend the behavior of welded structures in regard to their damage tolerance, the application of fracture mechanics serves as the instrumental tool. However, the methods employed overlook the changes in the microstructure within the Heat-Affected Zone (HAZ), which leads to the degradation of the mechanical properties of the material. The purpose of this study is to simulate microhardness evolution in the HAZ of AA2198-T351 LBW. The material represents the latest generation of Al-Cu-Li alloys, which exhibit improved mechanical properties, enhanced damage tolerance behavior, lower density and better corrosion and fatigue crack growth resistance than conventional Al-Cu alloys. In this work, the microhardness profile of LBW AA2198 was measured, and subsequently, through isothermal heat treatments on samples, the microhardness values of the HAZ were replicated. The conditions of the heat treatments (T, t) were selected in line with the thermal cycles that each area of the HAZ experienced during welding. ThermoCalc and DICTRA were employed in order to identify the strengthening precipitates and their evolution (dissolution and coarsening) during the weld thermal cycle. The microstructure of the heat-treated samples was studied employing LOM and TEM, and the strengthening precipitates and their characteristics (volume fraction and size) were defined and correlated to the calculations and the experimental conditions employed during welding. The main conclusion of this study is that it is feasible to imitate the microstructure evolution within the HAZ through the implementation of isothermal heat treatments. This implies that it is possible to fabricate samples for fatigue crack growth tests, enabling the experimental examination of the damage tolerance behavior in welded structures.
]]>Crystals doi: 10.3390/cryst14030245
Authors: Aarón Calvo-Villoslada Paloma Fernández Belén Sotillo
Joule heating of niobium (Nb) metal wires by running a high electric current density through them has been used to grow Nb2O5 nanowires. The formation of a micrometric oxide layer on the Nb wires has also been observed. The size and density of the nanowires are related to the current values applied, as well as the thickness of the oxide layer formed. Characterization of both nanowires and oxide layer has been performed using X-ray diffraction, scanning electron microscopy, energy dispersive X-ray microanalysis, and micro-Raman spectroscopy. It has been observed that this method allows the growth of Nb2O5 nanowires in times as short as tens of seconds.
]]>Crystals doi: 10.3390/cryst14030244
Authors: Yindong Fang Chu Yu Nikolai Kropotin Martin Seyring Katharina Freiberg Matthias Kolbe Stephanie Lippmann Peter K. Galenko
The solidification of Inconel 718 alloy (IN718) from undercooled liquid is studied. The solidification kinetics is evaluated in melted and undercooled droplets processed using the electromagnetic levitation (EML) technique by the temperature–time profiles and solid/liquid (S/L) interface movement during recalescence. The kinetics is monitored in real time by special pyrometrical measurements and high-speed digital camera. It is shown that the growth velocity of γ-phase (the primary phase in IN718), the final crystalline microstructure (dendritic and grained), and the mechanical properties (microhardness) are strongly dependent on the initial undercooling ΔT at which the samples started to solidify with the originating γ-phase. Particularly, with the increase in undercooling, the secondary dendrite arm spacing decreases from 28 μm to 5 μm. At small and intermediate ranges of undercooling, the solidified droplets have a dendritic crystalline microstructure. At higher undercooling values reached in the experiment, ΔT>160 K (namely, for samples solidified with ΔT=170 K and ΔT=263 K), fine crystalline grains are observed instead of the dendritic structure of solidified drops. Such change in the crystalline morphology is qualitatively consistent with the behavior of crystal growth kinetics which exhibits the change from the power law to linear law at ΔT≈160 K in the velocity–undercooling relationship (measured by the advancement of the recalescence front in solidifying droplets). Study of the local mechanical properties shows that the microhardness increases with the increase in the γ″-phase within interdendritic spacing. The obtained data are the basis for testing the theoretical and computational of multicomponent alloy samples.
]]>Crystals doi: 10.3390/cryst14030243
Authors: I. Yucel Akkutlu Emre Arslan Faisal Irshad Khan
Methane hydrate formation is analytically studied in the presence of the water memory effect using the classical nucleation theory. The memory effect is introduced as a change in nucleation site from a three-dimensional heterogenous nucleation on a solid surface with cap-shaped hydrate clusters (3D-HEN) to a two-dimensional nucleation on the solid hydrate residue surface with monolayer disk-shaped hydrate clusters (2D-NOH). The analysis on the stationary nucleation of methane hydrate under isobaric conditions shows that the memory effect caused an average decrease of 4.4 K in metastable zone width, or subcooling. This decrease can be erased at higher dissociation temperatures (ΔT > 17.2 K) due to a decrease in the concentration of 2D-NOH nucleation sites. Moreover, the probability of hydrate formation is estimated for the purpose of quantifying risk associated with methane hydrate formation in the presence of the memory effect.
]]>Crystals doi: 10.3390/cryst14030242
Authors: Peifeng Xiong Man Xiao Zhonghua Yao Hanxing Liu Hua Hao
Lead-free ceramics with excellent energy storage performance are important for high-power energy storage devices. In this study, 0.9BaTiO3-0.1Bi(Mg2/3Nb1/3)O3 (BT-BMN) ceramics with x wt% ZnO-Bi2O3-SiO2 (ZBS) (x = 2, 4, 6, 8, 10) glass additives were fabricated using the solid-state reaction method. X-ray diffraction (XRD) analysis revealed that the ZBS glass-added ceramics exhibited a perovskite structure, with the maximum relative density achieved at x = 6. The average grain size reduced obviously as the glass additive wt% increased. Also, the dielectric constant decreased and the breakdown strength increased with increases in the glass additives. The optimal energy storage density of 1.39 J/cm3 with an energy storage efficiency of 78.3% was obtained at x = 6 due to high maximum polarization and enhanced breakdown strength. The results demonstrate that this material is a potential candidate for high-pulse-power energy storage devices.
]]>Crystals doi: 10.3390/cryst14030241
Authors: Bohae Lee Han-Youl Ryu
We investigated the effect of cross-sectional shape and size on the light-extraction efficiency (LEE) of GaN-based blue nanorod light-emitting diode (LED) structures using numerical simulations based on finite-difference time-domain methods. For accurate determination, the LEE and far-field pattern (FFP) were evaluated by averaging them over emission spectra, polarization, and source positions inside the nanorod. The LEE decreased as rod size increased, owing to the nanorods’ increased ratio of cross-sectional area to sidewall area. We compared circular, square, triangular, and hexagonal cross-sectional shapes in this study. To date, nanorod LEDs with circular cross sections have been mainly demonstrated experimentally. However, circular shapes were found to show the lowest LEE, which is attributed to the coupling with whispering-gallery modes. For the total emission of the nanorod, the triangular cross section exhibited the highest LEE. When the angular dependence of the LEE was calculated using the FFP simulation results, the triangular and hexagonal shapes showed relatively high LEEs for direction emission. The simulation results presented in this study are expected to be useful in designing high-efficiency nanorod LED structures with optimum nanorod shape and dimensions.
]]>Crystals doi: 10.3390/cryst14030240
Authors: Shahab Ranjbar Bahadori Ryan Hart Aditi Mulgaonkar Yunfeng Wang Samuel Fuentes Yi Hong Ye Cao Jiechao Jiang Xiankai Sun Yaowu Hao
We report a simple synthesis process for a wide variety of ultrasmall nanocrystals. Simply immersing a dialysis bag containing an aqueous solution of a metal salt mixed with citric acid in a NaOH solution reservoir for 10 min, nanocrystals measuring only a few nanometers in size are formed inside the dialysis bag. We demonstrated the synthesis of ultrasmall nanocrystals of Co, Ni, Cu, Ag, Au, Pd, Cu2O, FeO, and CeO2, and found that the gradual change in pH caused by the diffusion of OH− ions through the dialysis membrane played an essential role in the formation of these nanocrystals. This method can be readily adapted for almost all transition metal elements, providing researchers in the fields of catalysis and nanomedicine an easy access to a wide range of ultrasmall metal and oxide nanocrystals.
]]>Crystals doi: 10.3390/cryst14030239
Authors: Shuo Li Hai Yang
Based on two-dimensional green phosphorene, we designed two molecular electronic devices with zigzag (Type 1) and whisker-like (Type 2) configurations. By combining density functional theory (DFT) and non-equilibrium Green’s function (NEGF), we investigated the electronic properties of Types 1 and 2. Type 1 exhibits an interesting negative differential resistance (NDR), while the current characteristics of Type 2 show linear growth in the current–voltage curve. We studied the electronic transport properties of Type 1 under uniaxial strain modulation and find that strained devices also exhibit a NDR effect, and the peak-to-valley ratio of device could be controlled by varying the strain intensity. These results show that the transport properties of green phosphorene with different edge configuration are different, and the zigzag edge have adjustable negative differential resistance properties.
]]>Crystals doi: 10.3390/cryst14030238
Authors: Carmen González-Enguita Rosario García-Giménez
The variety of types that appear in kidney stones makes it necessary to describe them to try to understand their formation. The crystalline phases recognized in stones are classified according to their chemical composition. For this reason, a study using X-ray microdiffraction, Raman spectroscopy, SEM/EDX analysis, and cathodoluminescence (CL) is recommended, to identify their composition. In the present study, this was carried out on kidney stones collected from surgeries in hospitals from Spain. The samples were collected in two representative urban centers: one from a large city, Madrid; the other with a mostly rural population, in order to contrast the possible compositions of the kidney stones. In large cities, struvite appears more frequently, although calcium oxalates are very common in both areas. An attempt was made to provide a guide to the most frequent phases, accompanied by four analysis methods that make their identification possible.
]]>Crystals doi: 10.3390/cryst14030236
Authors: Mohammed Es-Souni
Waste heat is inherent to industrial activities, IT services (e.g., data centers and microprocessors), human mobility, and many other common processes. The power lost each year in this way has been estimated in the 1000 TWh in the EU which, owing to skyrocketing energy prices and not least the urgent need for decarbonizing the economy, has engendered tremendous research efforts among scientists and engineers to recover/recycle this waste energy. Beyond established thermal engineering solutions for waste heat, advances in multifunctional materials open new paradigms for waste heat harvesting. Two smart material types are of particular focus and interest at present; these are thermoelectric and pyroelectric materials, which can both transform heat to electrical power, though via different effects. The present paper summarizes our research work on a new class of pyroelectric materials, namely <111> oriented (1 − x)(Pb(Mg1/3Nb2/3)O3–xPbTiO3 (PMN-PT) and x-Pb(In1/2 Nb1/2)O3-y-Pb(Mg1/3 Nb2/3)O3-(1 − x − y)-PbTiO3 (PIN-PMN-PT) single crystals that exhibit some of the highest pyroelectric properties ever measured. First, a figure of merit for pyroelectric energy harvesting is derived, followed by a detailed assessment of the properties of the said crystals and how they depend on structure, poling, thickness, and temperature. The properties are further contrasted with those of conventional pyroelectric crystals. It is concluded that the PMN-PT-base single crystals are best suited for harvesting devices with a working temperature range from 40 to 100 °C, which encompasses waste heat generated by data centers and some chemical and industrial processes, affording the highest figure of merit among pyroelectric materials.
]]>Crystals doi: 10.3390/cryst14030237
Authors: Wenyi Hu Qichi Le Qiyu Liao Tong Wang
The effects of ultrasonic treatment on grain refinement and hydrogen removal in three kinds of magnesium alloys—Mg-3Ca, Mg-6Zn-1Ca, and AZ80 alloys—were investigated in this study. After ultrasonic treatment, the grains of the magnesium alloys were refined to varying degrees. The degassing effect was characterized by measuring the densities and hydrogen content of ingots. The results indicated that the application of ultrasonic treatment in these magnesium alloys was able to remove hydrogen and obviously refine the microstructure. In this experiment, both the measurement of the density of the ingots and the solid-state hydrogen measurement reflected the degree of degassing. The highest degassing efficiencies were 53.8%, 67.5%, and 34.9% for the Mg-3Ca, Mg-6Zn-1Ca, and AZ80 alloys, respectively. The lowest hydrogen content of the AZ80 alloy reached 8.2 cm3/100 g, and the corresponding tensile strengths were 174 Mpa, 79 Mpa, and 6.2%, which represented increases of 41.5%, 38.6%, and 87.9%, respectively. The cavitation effect and acoustic streaming effect with an appropriate ultrasonic treatment duration resulted in grain refinement, degassing, and the uniform dispersion of second phases. This can significantly improve mechanical properties and provide a basis for industrial production.
]]>Crystals doi: 10.3390/cryst14030234
Authors: Cengceng Dong Chunlei Ruan
The population balance equations (PBEs) serve as the primary governing equations for simulating the crystallization process. Two-dimensional (2D) PBEs pertain to crystals that exhibit anisotropic growth, which is characterized by changes in two internal coordinates. Because PBEs are the hyperbolic equations, it becomes imperative to establish a high-resolution scheme to reduce numerical diffusion and numerical dispersion, thereby ensuring accurate crystal size distribution. This paper uses Euler’s first-order explicit (EE) method–Peridynamic Differential Operator (PDDO) to solve 2D PBE, namely, the EE method for discretizing the time derivative and the PDDO for discretizing the internal crystal-size derivative. Five examples, including size-independent growth with smooth and non-smooth distributions, size-dependent growth, nucleation, and size-independent/dependent growth for batch crystallization are considered. The results show that the EE–PDDO method is more accurate than the HR method and that it is as good as the fifth-order Weighted Essential Non-Oscillatory (WENO) method in solving 2D PBE. This study extends the EE–PDDO method to the simulation of 2D PBE, and the advantages of the EE-PDDO method in dealing with discontinuous and sharp front problems are demonstrated.
]]>Crystals doi: 10.3390/cryst14030235
Authors: Dengxiaojiang Zhao Zhenpei Chen Borui Li Shi Feng Nengneng Luo
AgNbO3 (AN) lead-free antiferroelectric material has attracted great attention in recent years. However, little focus has been directed toward a single crystal that can provide more basic information. In this study, we successfully grew high-quality AN single crystals, using a flux method, with dimensions of 5 × 5 × 3 mm3. A systematic investigation into the crystal structure, domain structure, and electrical properties of a [001]-oriented AN single crystal was conducted. X-ray diffraction and domain structure analysis revealed an orthorhombic phase structure at room temperature. Stripe-like 90° domains aligning parallel to the [110] direction with a thickness of approximately 10–20 μm were observed using a polarized light microscope. The temperature dependence of dielectric permittivity showed M1-M2, M2-M3, and M3-O phase transitions along with increasing temperature, but the phase transition temperatures were slightly higher than those of ceramic. The AN single crystal also exhibited double polarization-electric field (P-E) hysteresis loops, which enabled good recoverable energy-storage density and efficiency comparable to ceramic. Additionally, double P-E loops were kept stable at various temperatures and frequencies, demonstrating robust stability and confirming typical antiferroelectric characteristics. Our work provides valuable insights into understanding the fundamental antiferroelectric properties of AN-based materials.
]]>Crystals doi: 10.3390/cryst14030233
Authors: Nikolay Velinov Tanya Petrova Daniela Karashanova Genoveva Atanasova Daniela Kovacheva
Nanocrystalline materials with the composition of (Cu0.5Ni0.5)yFe3−yO4 and a spinel structure were synthesized by the auto-combustion sol–gel method. The materials were characterized by powder X-ray diffraction, Mössbauer spectroscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, and N2 physisorption. A decrease in the unit cell parameter and increase in the crystallite size with a decrease in the copper and nickel content in ferrites were evidenced. Mössbauer analysis determined that iron ions are in the 3+ states in all compositions. Transmission electron microscopy showed that synthesized ferrite materials consisted of nanoparticles with narrow size distributions. The catalytic properties of synthesized ferrites were studied in the reaction of ethyl acetate oxidation and methanol decomposition. The conversion of ethyl acetate and CO2 selectivity increased with temperature, and this effect was most pronounced for (Cu0.5Ni0.5)0.5Fe2.5O4, for which the main part of the particles possessed sizes below 10 nm, and the mean diameter was calculated to be 4.3 nm. The catalytic activity in the reaction of methanol decomposition was the highest for (Cu0.5Ni0.5)0.25Fe2.75O4, and it decreased with the increase in Cu and Ni content in the samples. The analysis of the samples after the catalytic test indicated significant reduction transformations within the catalysts. Under the reaction medium, the spinel phase decomposed through the formation of Hägg carbide.
]]>Crystals doi: 10.3390/cryst14030232
Authors: Qiangqiang Chen Jian Shang E Xue
In this paper, the tribological behavior of Cu-SiO2 composite against 1045 steel was studied. Based on the characterization of worn surface, worn subsurface and wear debris in morphology and composition, the friction layer effects on the tribological behavior of coupled materials and the wear mechanism were discussed. Abrasive wear and adhesive wear are the dominant mechanisms at the 0.56 m/s–1.12 m/s condition. Delamination wear and oxidation wear are the dominant wear mechanisms at the 1.68 m/s–2.24 m/s condition. Plastic and thermal deformation cause the evolution in morphology and structure of the tribolayer of Cu-SiO2. There is a certain correlation between the friction coefficient and the variation in friction temperature during sliding wear of Cu-SiO2 and 1045 steels. The addition of SiO2 induces the accumulation of frictional heat at the friction interface, which leads to an increase in the average temperature of the contact surface and transfer.
]]>Crystals doi: 10.3390/cryst14030231
Authors: Frederik Van Acker Bo-Han Lin Chun-Ta Wang Kristiaan Neyts Jeroen Beeckman
Nematic chiral liquid crystals (CLCs) are characterized by a helical arrangement of nematic LC molecules. A layer of CLC typically exhibits an optical reflection band due to Bragg reflection in the helical structure. When several layers of CLC are spin-coated and polymerized on top of each other without a barrier layer in between, defect modes can form in their reflection spectrum. By comparing experimental results and simulations, we investigate the origin of the defect modes, thereby revealing details on the behavior of the materials at the interfaces during deposition. Simulations show that these defect modes can originate from the migration of chiral dopant leading to a layer with a smaller pitch or from a discontinuity in the director orientation at the interface between two layers.
]]>Crystals doi: 10.3390/cryst14030229
Authors: Huanhuan Li Jinyuan Ma Guang Li Wenzhu Zhang Xianheng Bao Yu Shi
The 2205 duplex stainless steel (DSS) produced by selective laser melting (SLM) exhibits high strength (1078.8 MPa) but poor plasticity (15.2%) owing to the high cooling rate during SLM, which inhibits the formation of austenite and creates a nearly entirely ferritic microstructure. The dual-phase nature can be restored through solution annealing, which enables well-matched strength and plasticity, but which has not been extensively studied. We investigate the effects of 5 min, 30 min, and 120 min of solution annealing at 1000 °C on the dual-phase ratio, grain size, texture strength, inclusions, grain boundary characteristics, and mechanical properties of SLM-manufactured 2205 DSS. After 30 min of solution annealing, the elongation increased to 32.2% owing to the restoration of the dual-phase structure, the reduction in dislocation density, the weakening of texture, and the decrease in grain size. Increasing solution annealing time also corresponded to a decrease in the ultimate tensile strength (from 831.7 to 787.5 MPa) and yield strength (from 610.3 to 507.8 MPa) due to grain coarsening and the gradual transformation of ferrite to austenite. Furthermore, the mechanism of the transformation from ferrite to austenite was proposed, and it was observed that the transformation of MnSiO3 to MnCrO4 provided nucleation sites for austenite.
]]>Crystals doi: 10.3390/cryst14030230
Authors: Petr Král Jiří Dvořák Marie Kvapilová Andrej G. Kadomtsev Václav Sklenička
This work investigates the creep behavior of severely deformed commercial aluminum. The commercial aluminum was processed by helical rolling (HR) and equal-channel angular pressing (ECAP) at room temperature. During these processes, the equivalent strain up to about 4 was imposed into the as-received material. The creep testing at 200 °C revealed that HR and ECAP significantly increased the time to fracture compared to the as-received material. The stress dependences showed that the value of stress exponent n decreased with the value of the imposed strain. The stress-change tests showed that as-received and severely deformed states exhibited different recovery rates after unloading. The microstructure analysis showed that creep behavior was influenced by the microstructure formed during severe plastic deformation. The relationships between creep behavior and microstructure in the investigated states are discussed.
]]>Crystals doi: 10.3390/cryst14030228
Authors: Hong Zhong Jason Lonergan John S. McCloy Scott P. Beckman
Technetium-99 is a highly radioactive isotope with a long half-life that is common in nuclear waste. It volatizes at a low temperature, which poses a significant challenge to the clean-up and containment processes. Due to difficulties in purifying technetium compounds, their thermophysical properties have not been measured or calculated. Here, first principle methods are used along with the quasi quasi-harmonic harmonic approximation to compute the Debye temperature, volumetric thermal expansion coefficient, bulk modulus, and heat capacity of rutile TcO2 for temperatures ranging from 0 to 1500 K and applied pressures ranging from 0 to 255 GPa. The computed atomic structures agree well with the results from diffraction measurements. The computed thermophysical properties are in the neighborhood of other rutile metal oxides and, in particular, are within approximately 10–13% of rutile ReO2, which is frequently used as a substitute for TcO2 in experimental studies.
]]>Crystals doi: 10.3390/cryst14030227
Authors: Rositsa Nikolova Vladislav Kostov-Kytin Nadia Petrova Krasimir Kossev Rositsa Titorenkova Gergana Velyanova
Urea complexes of magnesium sulfate have been intensively studied due to their application in many areas of life, including agricultural chemistry, pharmacy, medicine, etc. The aim of this study is to add new knowledge about the trends and consistencies in the preparation procedures of MgSO4·nOC(NH2)2·mH2O phases. A set of analytical methods was used to characterize their structure, thermal and spectroscopic properties. The conditions for obtaining the three complexes in pure form were specified and the crystal structures of MgSO4·OC(NH2)2·2H2O and MgSO4·OC(NH2)2·3H2O were determined. The spectroscopic data of the considered compounds were analysed with respect to their structural and chemical properties. Thermal analyses showed that both the melting point and the urea decomposition temperature depend on the OC(NH2)2: H2O ratio in the octahedral environment of the magnesium ion in the studied structures.
]]>Crystals doi: 10.3390/cryst14030226
Authors: Zhihua Chen Longxi Chen Xiangjia Meng Yufu Ning Yang Xun
In this study, one-dimensional grating coupler on single-crystal lithium niobate thin film (lithium niobate on insulator, LNOI) that also served as a polarization splitter was designed. The coupler could separate both orthogonal polarization states into two opposite directions while coupled light from a standard single-mode fiber to a waveguide on LNOI at the same time. Using segmented and apodized designing, the peak coupling efficiencies (CEs) around telecommunication wavelength 1550 nm for fundamental TE and TM modes of −2.82 dB and −2.83 dB, respectively, were achieved. The CEs could be optimized to −1.97 dB and −1.8 dB when a metal layer was added below the silicon dioxide layer.
]]>Crystals doi: 10.3390/cryst14030225
Authors: Mengyang Yu Qiuxia Feng Zhipeng Liu Peng Zhang Xuefeng Zhu Shenglong Mu
Research has been conducted on solid oxide fuel cells (SOFCs) for their fuel flexibility, modularity, high efficiency, and power density. However, the high working temperature leads to the deterioration of materials and increased operating costs. Considering the high protonic conductivity and low activation energy, the proton conducting SOFC, i.e., the protonic ceramic fuel cell (PCFC), working at a low temperature, has been wildly investigated. The PCFC is a promising state-of-the-art electrochemical energy conversion system for ecological energy; it is characterized by near zero carbon emissions and high efficiency, and it is environment-friendly. The PCFC can be applied for the direct conversion of various renewable fuels into electricity at intermediate temperatures (400–650 °C). The construction of the PCFC directly affect its properties; therefore, manufacturing technology is the crucial factor that determines the performance. As a thinner electrolyte layer will lead to a lower polarization resistance, a uniformly constructed and crack-free layer which can perfectly bond to electrodes with a large effective area is challenging to achieve. In this work, different fabrication methods are investigated, and their effect on the overall performance of PCFCs is evaluated. This article reviews the recent preparation methods of PCFCs, including common methods, 3D printing methods, and other advanced methods, with summarized respective features, and their testing and characterization results.
]]>Crystals doi: 10.3390/cryst14030224
Authors: Rusiri Rathnasekara Grant M. Mayberry Parameswar Hari
In this work, we described the variations in the defect energy levels of four different ZnO morphologies, namely nanoribbons, nanorods, nanoparticles, and nanoshuttles. All the ZnO morphologies were grown on a seeded 4% Boron-doped p-type silicon (p-Si) wafer by using two different synthesis techniques, which are chemical bath deposition and microwave-assisted methods. The defect energy levels were analyzed by using the Deep-Level Transient Spectroscopy (DLTS) characterization method. The DLTS measurements were performed in the 123 K to 423 K temperature range. From the DLTS spectra, we found the presence of different trap-related defects in the synthesized ZnO nanostructures. We labeled all the traps related to the four different ZnO nanostructures as P1, P2, P3, P4, and P5. We discussed the presence of defects by measuring the activation energy (Ea) and capture cross-section (α). The lowest number of defect energy levels was exhibited by the ZnO nanorods at 0.27 eV, 0.18 eV, and 0.75 eV. Both the ZnO nanoribbons and nanoparticles show four traps, which have energies of 0.31 eV, 0.23 eV, 0.87 eV, and 0.44 eV and 0.27 eV, 0.22 eV, 0.88 eV, and 0.51 eV, respectively. From the DLTS spectrum of the nanoshuttles, we observe five traps with different activation energies of 0.13 eV, 0.28 eV, 0.25 eV, 0.94 eV, and 0.50 eV. The DLTS analysis revealed that the origin of the nanostructure defect energy levels can be attributed to Zinc vacancies (Vzn), Oxygen vacancies (Vo), Zinc interstitials (Zni), Oxygen interstitials (Oi), and Zinc antisites (Zno). Based on our analysis, the ZnO nanorods showed the lowest number of defect energy levels compared to the other ZnO morphologies.
]]>Crystals doi: 10.3390/cryst14030223
Authors: Gabriella Dravecz Laura Kocsor László Péter László Temleitner Dávid Gál Krisztián Lengyel
Structural changes of Er- or Yb-ion doped LiNbO3 (LN) nanocrystals were studied in relation to the high-energy ball milling process. The evolution of the size of the particles and the formation of different phases were followed by dynamic light scattering and X-ray diffraction measurements, while the electronic transitions of rare-earth (RE) ions were investigated by absorption spectroscopy in the infrared spectral range. During the milling process, RE ions left the crystal lattice and an RE2O3 phase appeared to an increasing extent next to the LN. The change in the absorption spectra and the phases formed during the grinding process were found to be very similar for both investigated RE ions and were independent of their original concentration in the starting crystal samples. The extent of the RE loss was found to be 90% after 100 min of wet grinding.
]]>Crystals doi: 10.3390/cryst14030222
Authors: Sarah Fleck Sahar Vahabzadeh
Brushite cements (BrCs) are calcium phosphate-based materials that are being widely used in hard tissue engineering applications due to their osteoconductivity, injectability, and bioresorbability. Therefore, the goal was to evaluate the effects of Mg concentration on the phase composition, setting time, and strength of BrC. Mg, which plays a vital role in bodily functions and bone health, was added to BrC at concentrations of 0.25, 0.50, 1.00, 1.50, 2.00, and 2.50 wt.%. The results showed that Mg stabilizes the TCP structure and increases the TCP content in final BrC. The initial and final setting times of BrCs increase with higher concentrations of Mg. Although 0.25 wt.% Mg did not change the setting of BrCs significantly, a higher concentration of 1.00 wt.% increased the initial setting time from 4.87 ± 0.38 min to 15.14 ± 0.88 min. Cements with Mg concentrations of 1.5 wt.% and above did not set after 4 h. Mg addition up to 0.5 wt.% did not change the compressive strength; however, higher concentrations decreased it significantly and 2.5 Mg-BrC had the lowest strength of 0.45 ± 0.09 MPs. Together, our results show that Mg can be added up to 1.00 wt.% without any adverse effect on the physical and mechanical properties of BrC.
]]>Crystals doi: 10.3390/cryst14030221
Authors: Vladimir L. Solozhenko Samir F. Matar
The superdense hexagonal boron pnictides BX (X = As, Sb, Bi), whose structures are formed by distorted tetrahedra and characterized by a quartz-derived (qtz) topology, have been predicted from first principles as potential high-pressure phases. From full geometry structure relaxation and ground state energy calculations based on quantum density functional theory (DFT), qtz BX was found to be mechanically (elastic constants) and dynamically (phonons) stable. From the energy–volume equations of state, at high but experimentally accessible pressures, qtz boron pnictides were found to be more energetically favorable than corresponding cubic zinc–blende phases with diamond-like (dia) topology. According to the electronic band structures, the zinc–blende BX have larger band gaps than the qtz phases, which can be attributed to the higher covalence of the latter. A metallic behavior is only observed for qtz BBi, which is related to the dynamic instability as it follows from the phonon band structure.
]]>Crystals doi: 10.3390/cryst14030220
Authors: Anna Guzanová Dagmar Draganovská Janette Brezinová Miroslav Tomáš Nikita Veligotskyi Štefan Kender
This paper deals with joining dissimilar materials using thermal drilling technology as well as the combination of thermal drilling and adhesive bonding. The base materials for the experimental work were deep-drawn low-carbon steel DC04, HSLA steel TL 1550-220 + Z, and structural aluminum alloy EN AW-6082 T6 (AlSi1MgMn). The geometry of the formed joints was tested metallographically as the load-bearing shear capacity under the tensile shear test of single-lapped joints and the resistance of the joints against corrosion-induced disbonding in a climate chamber. The energy dissipated by the joints up to fracture was calculated from the load–displacement curves. The hybrid joints were compared with the bonded joints with the same overlap area in terms of the load-bearing capacity and energy dissipated at joint failure. The hybrid joints formed by thermal drilling and adhesive bonding with a rubber-based adhesive confirmed the synergistic effect—the adhesive provides the high load-bearing capacity of the joint, and the bushing formed by thermal drilling increases the dissipated energy of the joint at failure. The exposure of the joints in the climatic chamber did not cause a relevant reduction in the characteristics of the joints.
]]>Crystals doi: 10.3390/cryst14030219
Authors: Wang Wei Yangguang Li Ningning Tian Tian Xie Dengpan Nie Hongyan Li Hongdong Quan Xiuguo Yang Luqian Ye Xiaohe Li Kangli Li Ye Gao
The crystal habit of pentaerythritol (PE) crystals is usually rod-shaped, which may lead to low bulk density and bad flowability compared with low aspect ratio crystals. In this study, dipentaerythritol (DPE), methylcellulose (MC), and hydroxypropyl methylcellulose (HPMC) were selected as additives to modify the morphology of PE crystals. In the presence of DPE, the bulk density of PE crystals was improved, and the aspect ratio was decreased. The modified attachment energy (AE) model was conducted to analyze changes in PE crystal habits in the presence of DPE, which characterizes the intensity of the interaction between DPE molecules and PE crystal faces. Spherical pentaerythritol crystals can be successfully prepared by adding MC and HPMC solution, and the formation mechanism can be divided into five steps.
]]>Crystals doi: 10.3390/cryst14030218
Authors: Lenka Oroszová Dávid Csík Gabriela Baranová Gábor Bortel Róbert Džunda László Temleitner Mária Hagarová Ben Breitung Karel Saksl
In the realm of advanced anode materials for lithium-ion batteries, this study explores the electrochemical performance of a high-entropy oxide (HEO) with a unique spinel structure. The equiatomic composition of CrMnFeCoCu was synthesized and subjected to a comprehensive materials characterization process, including X-ray diffraction and microscopy techniques. The multicomponent alloy exhibited a multiphase structure, comprising two face-centered cubic (FCC) phases and an oxide phase. Upon oxidation, the material transformed into a spinel oxide with a minor presence of CuO. The resulting high-entropy oxide demonstrated excellent electrochemical behavior when utilized as an anode material. Cyclic voltammetry revealed distinctive reduction peaks attributed to cation reduction and solid electrolyte interphase (SEI) layer formation, while subsequent cycles showcased high reversibility. Electrochemical impedance spectroscopy indicated a decrease in charge transfer resistance during cycling, emphasizing the remarkable electrochemical performance. Galvanostatic charge/discharge tests displayed characteristic voltage profiles, with an initial irreversible capacity attributed to SEI layer formation. The HEO exhibited promising rate capability, surpassing commercial graphite at higher current densities. The battery achieved 80% (275 mAh g−1) of its initial stable capacity at a current density of 500 mA g−1 by the 312th cycle. Post-mortem analysis revealed structural amorphization during cycling, contributing to the observed electrochemical behavior. This research highlights the potential of HEOs as advanced anode materials for lithium-ion batteries, combining unique structural features with favorable electrochemical properties.
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