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Crystals, Volume 13, Issue 11 (November 2023) – 79 articles

Cover Story (view full-size image): The synthesis and characterization of three new iron-based coordination polymers are presented in this journal. Coordination polymers are compounds containing organic linkers and inorganic nodes—both as repeating units that form one-, two- or three-dimensional structures. In this case, the Fe(II) atom acts as a node, and tris(triazolylmethyl)benzene as the linker, to form a one-dimensional structure. Among other things, the structures differ in their counter-anions or coordinated anions. Interestingly, the linker has one dangling, noncoordinated triazolyl ring, thus only utilizes two of its three potentially coordinating groups. This calls for further efforts to also bring the third ring to coordinate with a metal atom. View this paper
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12 pages, 4210 KiB  
Article
Photochromism, UV-Vis, Vibrational and Fluorescence Spectroscopy of Differently Colored Hackmanite
Crystals 2023, 13(11), 1607; https://doi.org/10.3390/cryst13111607 - 20 Nov 2023
Viewed by 708
Abstract
Because of the rich fluorescent color and unique photochromic properties, hackmanite has attracted many mineralogists. In this paper, the basic gemmological characteristics and photochromic and fluorescence mechanisms of four different colors of hackmanite are further investigated through the study of their structural, compositional, [...] Read more.
Because of the rich fluorescent color and unique photochromic properties, hackmanite has attracted many mineralogists. In this paper, the basic gemmological characteristics and photochromic and fluorescence mechanisms of four different colors of hackmanite are further investigated through the study of their structural, compositional, and spectroscopic features. The results show the change in the color of hackmanite in photochromism is caused by the joint action of the F-center and the oxygen hole centers. The change in the UV-Vis spectra may be caused by the superposition of two peaks. Under 365 nm UV excitation, the peak of fluorescence spectra of 662 nm is related to the 2g2u transition of S2, the blue emission at 441 nm is caused by the 3P0.11S0 transition of s2 ions (Pb2+, Tl+, Sn2+ Sb2+), and at 541 nm is caused by the Mn2+ center. The results are helpful in deepening the understanding of photochromism, fluorescence mechanism, and its structure, expanding the application of hackmanite. Full article
(This article belongs to the Section Mineralogical Crystallography and Biomineralization)
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13 pages, 4784 KiB  
Article
New Organic Crystalline Material Close to Nodal-Line Materials: α′-STF2IBr2
Crystals 2023, 13(11), 1606; https://doi.org/10.3390/cryst13111606 - 20 Nov 2023
Viewed by 679
Abstract
Recently, topological materials (TMs) have attracted attention from various scientists. Their electronic properties are governed by relativistic particles called Dirac fermions which, in some cases, possess no masses and move in solids with the speed of light. In addition to the unique particles, [...] Read more.
Recently, topological materials (TMs) have attracted attention from various scientists. Their electronic properties are governed by relativistic particles called Dirac fermions which, in some cases, possess no masses and move in solids with the speed of light. In addition to the unique particles, such materials exhibit unprecedented electronic properties because of the quantum effects (interference between wavefunctions). Examples include nodal-line materials (NLMs), where metallic or even superconducting properties may appear only at the surface of the single crystals of insulators. Thus far, whether they be organic or inorganic compounds, TMs have hardly been discovered except for the zero-gap conductors (ZGCs), because there is no guideline on how to develop such unusual materials. In this work, we prepared a new organic charge–transfer complex, α′-STF2IBr2 (STF = bis(ethylenedithio)diselenadithiafulvalene), which measured the electrical and magnetic properties and calculated the band structure and intermolecular interactions. A close comparison with those of α-STF2I3, being established as a ZGC at p > 12–15 kbar, revealed that α′-STF2IBr2 is also closely related to it, but belongs to a different type of TMs, namely NLMs. This finding will accelerate the successive findings of NLMs to elucidate the mechanism of their unique electronic properties. Full article
(This article belongs to the Special Issue Charge-Transfer Complexes (CTCs) and Related Interactions)
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12 pages, 5986 KiB  
Article
Spectroscopy and Trace-Element Characteristics of Emeralds from Kamakanga, Zambia
Crystals 2023, 13(11), 1605; https://doi.org/10.3390/cryst13111605 - 20 Nov 2023
Viewed by 718
Abstract
Currently, Zambia is the second largest source of emeralds, after Colombia. In this study, emerald samples from the Zambian Kamakanga deposit were examined by UV-Vis-NIR, Miro-FTIR, Diamond ViewTM, and LA-ICP-MS. Representative UV-Vis-NIR spectra showed a distinct Fe3+ absorption peak, and [...] Read more.
Currently, Zambia is the second largest source of emeralds, after Colombia. In this study, emerald samples from the Zambian Kamakanga deposit were examined by UV-Vis-NIR, Miro-FTIR, Diamond ViewTM, and LA-ICP-MS. Representative UV-Vis-NIR spectra showed a distinct Fe3+ absorption peak, and the Fe-related absorption band was much stronger than that of the Cr-related absorption band. The infrared spectra showed that the absorption of type II H2O was much stronger than that of type I H2O. The results of LA-ICP-MS indicated that darker green, green, lighter green, and bluish-green emeralds had a clear separation of Cr/V (Cr/V > 15 for darker green, 10 < Cr/V < 15 for green, and Cr/V < 10 for lighter green and bluish green). In color zoning emerald, the contents of Cr, Sc, V, and Fe gradually increased with the intensity of the green color, while the opposite occurred for Cs. Cr is the main chromogenic element in Kamakanga emeralds. Additionally, Zambian Kamakanga emeralds contain high contents of total alkali metals (avg. 17,592 ppmw), Cs (avg. 1331 ppmw), Fe (avg. 8556 ppmw), Li (avg. 485 ppmw), Li + Cs (avg. 1816 ppmw), and Ga/Fe < 0.0025. Therefore, combined Fe versus Ga, Li versus Cs binary diagrams and K, Rb, and the Li + Cs ternary plot can distinguish Zambian emeralds from other important emerald origins. Full article
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16 pages, 9074 KiB  
Article
Preliminary Parametric Investigations into Macro-Laser Polishing of Laser-Directed Energy Deposition of SS 304L Bulk Structures
Crystals 2023, 13(11), 1604; https://doi.org/10.3390/cryst13111604 - 20 Nov 2023
Viewed by 668
Abstract
The higher surface roughness of laser-directed energy deposition (LDED)-built components necessitates advanced and sustainable surface quality enhancement techniques like laser polishing. In the present work, a parametric study involving experimental investigation and numerical analysis is conducted to determine the effect of macro-laser polishing [...] Read more.
The higher surface roughness of laser-directed energy deposition (LDED)-built components necessitates advanced and sustainable surface quality enhancement techniques like laser polishing. In the present work, a parametric study involving experimental investigation and numerical analysis is conducted to determine the effect of macro-laser polishing on LDED-built SS 304L structures. A thermophysical model is developed to simulate the effect of laser power and scan speed on the melt pool depth of the LDED-built samples. The simulated melt pool depth is compared with experimental results and is found to be in good agreement. Further, the correlation between the melt pool depth and surface behaviour is studied based on shallow surface melting and shallow over-melting mechanisms. A maximum reduction in surface roughness from 21.3 µm to 9 µm (~57%) is achieved with laser polishing, and process parameters’ effect on the surface roughness is investigated. Scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS) mapping, and X-ray diffraction (XRD) are used to further characterize the laser-polished surface. SEM-EDS analysis shows that the segregation is more evident in laser-polished samples, while the XRD results indicate the absence of phase change during the process. This study paves the way to a greater understanding of the effect of macro-laser polishing on LDED-built SS 304L structures. Full article
(This article belongs to the Special Issue Additive Manufacturing of Metallic Alloys)
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13 pages, 24029 KiB  
Article
Highly Porous Layered Double Hydroxide and Mixed Metal Oxide by Sacrificial Bio-Template, Egg White Foam
Crystals 2023, 13(11), 1603; https://doi.org/10.3390/cryst13111603 - 20 Nov 2023
Viewed by 581
Abstract
Highly porous layered double hydroxide (LDH) and its calcined mixed metal oxide (MMO) were obtained by utilizing egg white (EW) as a biogenic porous template. The LDH was prepared through coprecipitation under the existence of a beaten EW meringue, and the corresponding MMO [...] Read more.
Highly porous layered double hydroxide (LDH) and its calcined mixed metal oxide (MMO) were obtained by utilizing egg white (EW) as a biogenic porous template. The LDH was prepared through coprecipitation under the existence of a beaten EW meringue, and the corresponding MMO was obtained by calcining LDH at 500 °C. According to X-ray diffraction, the crystal structure of LDH and MMO was well-developed with or without EW. In contrast, the crystallinity analyses and microscopic investigations clearly showed differences in the particle orientation in the presence of EW; the protein arrangement in the EW foam induced the ordered orientation of LDH platelets along proteins, resulting in well-developed inter-particle pores. As a result, the distinctive particle arrangement in EW-templated samples compared with non-templated ones showed dramatically enhanced specific surface area and porosity. The nitrogen adsorption–desorption isotherm exhibited that the high specific surface area was attributed to the homogeneous nanopores in EW-templated LDH and MMO, which originated from the sacrificial role of the EW. Full article
(This article belongs to the Special Issue Porous Materials and Their Adsorption Properties)
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13 pages, 3541 KiB  
Article
Type-II GaSe/MoS2 van der Waals Heterojunction for High-Performance Flexible Photodetector
Crystals 2023, 13(11), 1602; https://doi.org/10.3390/cryst13111602 - 20 Nov 2023
Viewed by 662
Abstract
In recent years, two-dimensional (2D) type-II van der Waals (vdW) heterojunctions have emerged as promising candidates for high-performance photodetectors. However, direct experimental evidence confirming the enhancement of photoelectric properties by the heterojunction’s type and structure remains scarce. In this work, we present flexible [...] Read more.
In recent years, two-dimensional (2D) type-II van der Waals (vdW) heterojunctions have emerged as promising candidates for high-performance photodetectors. However, direct experimental evidence confirming the enhancement of photoelectric properties by the heterojunction’s type and structure remains scarce. In this work, we present flexible photodetectors based on individual GaSe and MoS2, as well as a vertically stacked type-II GaSe/MoS2 vdW heterojunction on polyethylene terephthalate (PET) substrate. These devices demonstrate outstanding responsivities and rapid response speeds, ensuring stable and repeatable light detection. It is notable that the GaSe/MoS2 heterojunction photodetector exhibits the highest on-off ratio and fastest response speed, attributed to the formation of type-II band alignment. Furthermore, the GaSe/MoS2 heterojunction photodetector maintains robust stability even in a bent state, highlighting remarkable flexibility. This work exemplifies the type-II vdW heterojunctions in enhancing photoelectric properties through direct in-situ experimentation, laying the groundwork for practical applications of 2D flexible photodetectors. Full article
(This article belongs to the Special Issue Emerging Low-Dimensional Materials II)
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12 pages, 4478 KiB  
Article
Morphological, Structural, and Optical Features of Thermally Annealed Slag Powders Generated from the Iron and Steel Industry: A Source of Disordered Iron Oxide Composites
Crystals 2023, 13(11), 1601; https://doi.org/10.3390/cryst13111601 - 20 Nov 2023
Viewed by 775
Abstract
Steel slag waste produced by the steel industry accumulates in open areas or is disposed of in landfills, causing harm to the environment and human health. Valorizing steel slag through comprehensive data analysis is imperative and could add value to the product with [...] Read more.
Steel slag waste produced by the steel industry accumulates in open areas or is disposed of in landfills, causing harm to the environment and human health. Valorizing steel slag through comprehensive data analysis is imperative and could add value to the product with respect to energy conversion and storage applications. This study investigated the morphological, structural, and optical characteristics of a thermally annealed steel slag composite generated from iron and steel factories. Scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), Raman spectroscopy, and UV–visible spectrophotometry were subsequently used to evaluate the impact of thermal treatment on the morphology, structure, elemental composition, and optical properties. It was found that the pre-treated slag composites contained a variety of irregular grain sizes and microscale fragments, primarily composed of C (18.55%), O (50.85%), and Fe (29.41%), with lower amounts of Mg (0.31%), Si (0.44%), and Ca (0.44%), indicating the natural formation of a disordered iron composite. Thermal treatment at different temperatures (300 °C, 600 °C, and 900 °C) increased the grain density and clustering, resulting in denser two-dimensional microstructures at 900 °C. Additionally, XRD and Raman analyses of both untreated and thermally treated slag composites revealed the presence of a disordered iron oxide composite, including (Fe3O4), hematite (α-Fe2O3), and maghemite (γ-Fe2O3) phases. A significant increase in optical absorbance was also observed after annealing at 600 °C, highlighting the successful optimization of the elemental composition of the slag composite. A band gap energy of approximately 2.2 eV was obtained from this optimization at 600 °C. The optical conductivity of the composite reached 2.1 × 106 S−1 at 600 °C, which indicates an enhancement in charge transfer among the optimized chemical elements in the waste composite. These findings suggest an optimization method for novel composites derived from steel slag waste, indicating its potential as a low-cost material for energy storage systems (batteries, supercapacitors, and fuel cells) and optoelectronic devices. Full article
(This article belongs to the Section Materials for Energy Applications)
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15 pages, 11294 KiB  
Article
Electrochemical Characterization Method of Laves Phase in 9Cr Martensitic Heat-Resistant Steel and Creep Life Prediction
Crystals 2023, 13(11), 1600; https://doi.org/10.3390/cryst13111600 - 20 Nov 2023
Viewed by 601
Abstract
The Laves phase formed during the long-term creep of 9% Cr heat-resistant steels plays an important role in their high-temperature mechanical properties. Detecting and quantifying the Laves phase is one of the main problems in predicting the creep residual life. This study detects [...] Read more.
The Laves phase formed during the long-term creep of 9% Cr heat-resistant steels plays an important role in their high-temperature mechanical properties. Detecting and quantifying the Laves phase is one of the main problems in predicting the creep residual life. This study detects and quantifies the Laves phase in various 9% Cr heat-resistant steel samples by anodic polarization. Both T92/P92 samples after creep and 9Cr ferritic martensitic samples after thermal ageing precipitate Laves phase particles, and the content of the Laves phase increases with the service time. Comparing the results obtained by the electrochemical method with those obtained by the traditional SEM observation method, it can be found that there is a similar two-stage linear relationship between the two results in all materials, which is related to the diameter change of Laves phase particles during service. According to the correlation between the Laves phase content and creep time, an extrapolation method for the prediction of the residual creep life is proposed. The results show that the creep life of P92 can be predicted by using the dissolved charge density of the Laves phase with high prediction accuracy. This method has the potential to evaluate the service states of materials and predict the long-term creep life in the industrial field. Full article
(This article belongs to the Special Issue Modern Technologies in the Manufacturing of Metal Matrix Composites)
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12 pages, 36981 KiB  
Article
Observation of Micro-Scale Domain Structure Evolution under Electric Bias in Relaxor-Based PIN-PMN-PT Single Crystals
Crystals 2023, 13(11), 1599; https://doi.org/10.3390/cryst13111599 - 19 Nov 2023
Viewed by 787
Abstract
Relaxor ferroelectrics play a vital role as functional components in electromechanical devices. The observation of micro-scale domain structure evolution under electric bias in relaxor ferroelectrics has posed challenges due to their complex domain morphology characterized by small-sized domains. The present study aims to [...] Read more.
Relaxor ferroelectrics play a vital role as functional components in electromechanical devices. The observation of micro-scale domain structure evolution under electric bias in relaxor ferroelectrics has posed challenges due to their complex domain morphology characterized by small-sized domains. The present study aims to investigate the dielectric diffusion–relaxation characteristics, domain structure, and domain switching evolution under electric bias in high-performance single crystals of Pb(In1/2Nb1/2)O3-Pb(Mg1/3Nb2/3)O3-33PbTiO3. The findings reveal the presence of strip-like domain patterns that interlock irregular small-sized nanodomains in PIN-PMN-33PT single crystals. Furthermore, the sample undergoes three distinct stages under electric bias, including the nucleation of new domains, the gradual forward expansion of domains, and the lateral expansion of domains. These observations provide valuable insights for understanding and exploring domain engineering techniques in relaxor ferroelectrics. Full article
(This article belongs to the Special Issue Piezoelectric Ceramics and Devices)
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18 pages, 5830 KiB  
Article
Supramolecular Structure, Hirshfeld Surface Analysis, Morphological Study and DFT Calculations of the Triphenyltetrazolium Cobalt Thiocyanate Complex
Crystals 2023, 13(11), 1598; https://doi.org/10.3390/cryst13111598 - 19 Nov 2023
Viewed by 722
Abstract
Polymorphism is a prevalent occurrence in pharmaceutical solids and demands thorough investigation during product development. This paper delves into the crystal growth and structure of a newly synthesized polymorph (TPT)2[CoII(NCS)4], (1), where TPT is triphenyl tetrazolium. The [...] Read more.
Polymorphism is a prevalent occurrence in pharmaceutical solids and demands thorough investigation during product development. This paper delves into the crystal growth and structure of a newly synthesized polymorph (TPT)2[CoII(NCS)4], (1), where TPT is triphenyl tetrazolium. The study combines experimental and theoretical approaches to elucidate the 3D framework of the crystal structure, characterized by hydrogen-bonded interactions between (TPT)+ cations and [Co(NCS)4]2− anions. Hirshfeld surface analysis, along with associated two-dimensional fingerprints, is employed to comprehensively investigate and quantify intermolecular interactions within the structure. The enrichment ratio is calculated for non-covalent contacts, providing insight into their propensity to influence crystal packing interactions. Void analysis is conducted to predict the mechanical behavior of the compound. Utilizing Bravais-Friedel, Donnay-Harker (BFDH), and growth morphology (GM) techniques, the external morphology of (TPT)2[CoII(NCS)4] is predicted. Experimental observations align well with BFDH predictions, with slight deviations from the GM model. Quantum computational calculations of the synthesized compounds is performed in the ground state using the DFT/UB3LYP level of theory. These calculations assess the molecule’s stability and chemical reactivity, including the computation of the HOMO-LUMO energy difference and other chemical descriptors. The study provides a comprehensive exploration of the newly synthesized polymorph, shedding light on its crystal structure, intermolecular interactions, mechanical behavior, and external morphology, supported by both experimental and computational analyses. Full article
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13 pages, 8647 KiB  
Article
Effects of In and Ga on Spreading Performance of Ag10CuZnSn Brazing Filler Metal and Mechanical Properties of the Brazed Joints
Crystals 2023, 13(11), 1597; https://doi.org/10.3390/cryst13111597 - 19 Nov 2023
Viewed by 579
Abstract
Ag-based brazing filler metals are preferred in many industries, but the high price of Ag restricts their wider application. Therefore, developing novel low-Ag brazing filler metals has aroused extensive interest. In this study, the effects of the In and Ga elements on the [...] Read more.
Ag-based brazing filler metals are preferred in many industries, but the high price of Ag restricts their wider application. Therefore, developing novel low-Ag brazing filler metals has aroused extensive interest. In this study, the effects of the In and Ga elements on the melting behavior and spreading property of Ag10CuZnSn filler metal and the microstructure and strength of the brazed joints were investigated. The results show that both In and Ga can significantly decrease the solidus and liquidus temperatures of the filler metal. The In element can dissolve into the liquid filler metal and the Ga element can decrease the surface tension of the melted filler metal, which, in turn, improves the spreading area. The In element prefers to dissolve into the Ag-rich phase, and the Ga element prefers to dissolve into the Cu-rich phase; both improve the strength of the filler metal through solid-solution strengthening. The shear strength of the 304 stainless-steel brazed joint reached a peak value of 396 MPa when the Ag10CuZnSn-1.5In-2Ga (wt%) filler metal was used. However, the excessive addition of In and Ga forms brittle intermetallic compounds (IMCs) in the brazing seam, which decreases the strength of the brazed joint. Full article
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10 pages, 7630 KiB  
Article
Energy Transfer in the CaSO4Dy Thermoluminescent Dosimeter from the Excited State of the SO42 Anionic Complex to the Impurities
Crystals 2023, 13(11), 1596; https://doi.org/10.3390/cryst13111596 - 17 Nov 2023
Viewed by 543
Abstract
The creation of a combined radiative state at 2.95–3.1 eV in the phosphor CaSO4Dy 3+ has been investigated using vacuum ultraviolet and thermoactivation spectroscopy methods. It is shown that the combined radiative electronic state [...] Read more.
The creation of a combined radiative state at 2.95–3.1 eV in the phosphor CaSO4Dy 3+ has been investigated using vacuum ultraviolet and thermoactivation spectroscopy methods. It is shown that the combined radiative electronic state is formed from the radiative electronic states of the impurity electronic trapping centers Dy 2+ SO4 and the intrinsic electronic radiative states SO43SO4 during the excitation of the anion complex SO42, as a result of charge transfer from the excited anion complex O 2Dy 3+ to the impurities and the neighboring anion complex O2 SO42. In the CaSO4Dy phosphor, the combined radiative electronic state and impurity emission of Dy 3+, 2.16 eV and 2.56 eV are excited by photons with energies of 3.95–4.0 eV and 4.5–4.6 eV. Energy transfer from the matrix to the Dy 3+ impurities is revealed upon thermal exposure as a result of the ionization of the electronic capture centers of Dy2+ and SO43. Full article
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8 pages, 3003 KiB  
Communication
Self-Assembled La0.67Sr0.33MnO3:CeO2 Vertically Aligned Nanocomposite Thin Films on Flexible Mica
Crystals 2023, 13(11), 1595; https://doi.org/10.3390/cryst13111595 - 17 Nov 2023
Viewed by 637
Abstract
Vertically aligned nanocomposite (VAN) thin film has attracted tremendous research interests owing to its multifunctionality, enhanced physical properties and multi-field coupling. However, VAN has rarely been demonstrated in flexible form, which hinders its further application in flexible devices. In this work, La0.67 [...] Read more.
Vertically aligned nanocomposite (VAN) thin film has attracted tremendous research interests owing to its multifunctionality, enhanced physical properties and multi-field coupling. However, VAN has rarely been demonstrated in flexible form, which hinders its further application in flexible devices. In this work, La0.67Sr0.33MnO3-CeO2 (LC) VAN film has been deposited on flexible mica with or without a buffer layer. The LC nanocomposite films show high quality following textured growth and form a typical, vertically aligned nanostructure. Magnetic, transport and magnetoresistance properties have been explored for flexible nanocomposite thin films. Furthermore, flexible LC films maintain their properties after numerous mechanical bending tests, presenting promising future applications in flexible electronics and spintronics. Full article
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10 pages, 3707 KiB  
Article
A Fibrous Perovskite Nanomaterial with Exsolved Ni-Cu Metal Nanoparticles as an Effective Composite Catalyst for External Steam Reforming of Liquid Alcohols
Crystals 2023, 13(11), 1594; https://doi.org/10.3390/cryst13111594 - 17 Nov 2023
Viewed by 624
Abstract
The conversion of hydrogen to power via combined external reforming of liquid alcohol and solid oxide fuel cell (SOFC) technology is an effective approach to address future energy challenges. In this study, an La0.8Ba0.1Mn0.8Ni0.1Cu0.1 [...] Read more.
The conversion of hydrogen to power via combined external reforming of liquid alcohol and solid oxide fuel cell (SOFC) technology is an effective approach to address future energy challenges. In this study, an La0.8Ba0.1Mn0.8Ni0.1Cu0.1O3 (LBMNCu) perovskite nanofiber with high porosity was synthesized with a modified electrostatic spinning method, which acted as an efficient catalyst for steam reforming of liquid alcohols (methanol and ethanol). After reduction, fine metallic Ni-Cu was uniformly distributed throughout the perovskite nanofiber surface. The obtained composite displayed a methanol conversion above 99.9% at 450 °C and an ethanol conversion above 99% at 600 °C, which was highly superior to the common Ni-Cu/Al2O3 catalyst. The catalytic performance of our assembled catalysts also remained stable in methanol and ethanol atmospheres for 50 h and no coking was detected. Furthermore, when the reformed gas was fed into a Y0.08Zr0.92O2 (YSZ)-based SOFC system, the open circuit voltage remained around 1.1 V at 700 °C for 50 h accordingly, without coking, and the voltage remained virtually unchanged at 0.7 V for 50 h at 700 °C and 400 mA cm−2 during galvanostatic discharge mode, indicating that using LBMNCu nanofiber as a catalyst for hydrogen production and utilization is an efficient strategy. The interaction of the in situ exsolved metallic nanoparticles and nanofibrous perovskite could also be a promising approach for designing a highly active catalyst for H2 generation. Full article
(This article belongs to the Special Issue Advances of Solid Oxide Fuel Cells)
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18 pages, 5825 KiB  
Review
Research Progress on Metal–Organic Framework-Based Electrode Materials for Supercapacitors
Crystals 2023, 13(11), 1593; https://doi.org/10.3390/cryst13111593 - 17 Nov 2023
Cited by 1 | Viewed by 958
Abstract
Supercapacitors play an important role in power systems since they are a key part of electrochemical energy storage devices. To assemble high-performance supercapacitors, it is crucial to discover and innovate high-capacitive electrode materials. Recently, metal–organic frameworks (MOFs) and their derivatives have received wide [...] Read more.
Supercapacitors play an important role in power systems since they are a key part of electrochemical energy storage devices. To assemble high-performance supercapacitors, it is crucial to discover and innovate high-capacitive electrode materials. Recently, metal–organic frameworks (MOFs) and their derivatives have received wide concerns as electrode materials for supercapacitors, not only because of their high pore volume and large surface area for ions and electrons insertion and transportation, but also due to the intrinsic metal active sites that possibly offer extra faradaic pseudocapacitance. Additionally, the abundant species of MOFs with various morphologies also feature advantages in enriching the structural diversity of electrodes. In this paper, we first report the latest research progress and demonstrate the feasibility of pure MOFs for directly constructing supercapacitor electrodes. Furthermore, different MOF derivatives, including porous carbons, transition metal oxides, metal hydroxides and MOF composites for supercapacitors, are summarized, and their electrochemical performances with corresponding energy storage mechanisms are presented in detail. Finally, the perspectives for MOF-based materials applied in supercapacitors are discussed, aiming to provide a guideline for further research based on these promising materials. Full article
(This article belongs to the Special Issue Supercapacitor and Related Materials)
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23 pages, 9437 KiB  
Article
Additive Manufacturing and Mechanical Properties of Auxetic and Non-Auxetic Ti24Nb4Zr8Sn Biomedical Stents: A Combined Experimental and Computational Modelling Approach
Crystals 2023, 13(11), 1592; https://doi.org/10.3390/cryst13111592 - 17 Nov 2023
Viewed by 589
Abstract
The effect of plaque deposition (atherosclerosis) on blood flow behaviour is investigated via computational fluid dynamics and structural mechanics simulations. To mitigate the narrowing of coronary artery atherosclerosis (stenosis), the computational modelling of auxetic and non-auxetic stents was performed in this study to [...] Read more.
The effect of plaque deposition (atherosclerosis) on blood flow behaviour is investigated via computational fluid dynamics and structural mechanics simulations. To mitigate the narrowing of coronary artery atherosclerosis (stenosis), the computational modelling of auxetic and non-auxetic stents was performed in this study to minimise or even avoid these deposition agents in the future. Computational modelling was performed in unrestricted (open) conditions and restricted (in an artery) conditions. Finally, stent designs were produced by additive manufacturing, and mechanical testing of the stents was undertaken. Auxetic stent 1 and auxetic stent 2 exhibit very little foreshortening and radial recoil in unrestricted deployment conditions compared to non-auxetic stent 3. However, stent 2 shows structural instability (strut failure) during unrestricted deployment conditions. For the restricted deployment condition, stent 1 shows a higher radial recoil compared to stent 3. In the tensile test simulations, short elongation for stent 1 due to strut failure is demonstrated, whereas no structural instability is noticed for stent 2 and stent 3 until 0.5 (mm/mm) strain. The as-built samples show a significant thickening of the struts of the stents resulting in short elongations during tensile testing compared to the simulations (stent 2 and stent 3). A modelling framework for the stent deployment system that enables the selection of appropriate stent designs before in vivo testing is required. This leads to the acceleration of the development process and a reduction in time, resulting in less material wastage. The modelling framework shall be useful for doctors designing patient-specific stents. Full article
(This article belongs to the Special Issue New Materials and Concepts for Additive Manufacturing with Metals II)
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12 pages, 4945 KiB  
Article
Influence of Active Afterheater in the Crystal Growth of Gallium Oxide via Edge-Defined Film-Fed Growing Method
Crystals 2023, 13(11), 1591; https://doi.org/10.3390/cryst13111591 - 17 Nov 2023
Viewed by 749
Abstract
In this study, we explored the effect of an active afterheater on the growth of gallium oxide single crystals using the EFG method. We analyzed the temperature distribution of the crystal under the growing process through multiphysics simulations of the models with and [...] Read more.
In this study, we explored the effect of an active afterheater on the growth of gallium oxide single crystals using the EFG method. We analyzed the temperature distribution of the crystal under the growing process through multiphysics simulations of the models with and without an active afterheater and investigated the morphology of crystals by applying each model to real experimental growths. The afterheater is a component in the growing furnace that activates radiant heat transfer, and its performance depends on its location, size, material, and shape. The simulation results showed that the afterheater applied in this study was found to be effective in obtaining good temperature distribution in the reactor. Through experimental crystal growth corresponding to the simulation approaches, it was confirmed that an appropriate afterheater reduces thermal stress at the growth front and provides a thermal annealing effect on the post-grown crystals during the growing process to improve crystal quality. Full article
(This article belongs to the Special Issue β-Ga2O3: Growth (Bulk, Thin Film, Epitaxy) and Physical Properties)
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9 pages, 4468 KiB  
Article
Fabrication of SiC-on-Insulator (SiCOI) Layers by Chemical Vapor Deposition of 3C-SiC on Si-in-Insulator Substrates at Low Deposition Temperatures of 1120 °C
Crystals 2023, 13(11), 1590; https://doi.org/10.3390/cryst13111590 - 17 Nov 2023
Viewed by 704
Abstract
Compared to bulk silicon carbide (SiC) wafers, SiC-on-insulator (SiCOI) substrates enable new device designs of electronic switches as well as novel photonic applications. One application is a micro-resonator for the usage in a Kerr frequency comb. For SiCOI substrates, a deposition temperature below [...] Read more.
Compared to bulk silicon carbide (SiC) wafers, SiC-on-insulator (SiCOI) substrates enable new device designs of electronic switches as well as novel photonic applications. One application is a micro-resonator for the usage in a Kerr frequency comb. For SiCOI substrates, a deposition temperature below 1200 °C is advisable due to stability reasons of the buried oxide layer during chemical vapor deposition (CVD) process conditions. To create 3C-SiC-on-insulator layers, a cold-wall CVD reactor was utilized, with propane and silane as the sources for carbon and silicon, respectively. To improve the cracking of the carbon source gas at low temperatures, the inner setup of the utilized cold-wall CVD reactor was changed to a non-water-cooled system. The change of the inner reactor setup was investigated numerically, and the grown epitaxial layers were characterized by Raman, EDX, SEM-imaging and XRD spectroscopy. We demonstrate successful deposition of 3C-SiC epitaxial layer substrates at temperatures below 1200 °C without delamination on SOI. Full article
(This article belongs to the Special Issue Epitaxial Growth of Semiconductor Materials and Devices)
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18 pages, 7573 KiB  
Article
Effect of Nickel Addition on Solidification Microstructure and Tensile Properties of Cast 7075 Aluminum Alloy
Crystals 2023, 13(11), 1589; https://doi.org/10.3390/cryst13111589 - 17 Nov 2023
Viewed by 664
Abstract
In order to explore the casting technology of a high–strength aluminum alloy, the effects of nickel on the solidified microstructure and tensile properties of a 7075 aluminum alloy were studied. 7075 aluminum alloys without nickel and with 0.6% and 1.2% nickel were prepared [...] Read more.
In order to explore the casting technology of a high–strength aluminum alloy, the effects of nickel on the solidified microstructure and tensile properties of a 7075 aluminum alloy were studied. 7075 aluminum alloys without nickel and with 0.6% and 1.2% nickel were prepared by a casting method. The results showed that the increase of Ni content in the 7075 alloys increased the liquidus temperatures, primary α (Al) grains were refined significantly, and the divorced eutectic structure was gradually formed among α (Al) grains with the preformation of the Al3Ni phase. In comparison, the 7075 alloy with 0.6% nickel content had less intergranular shrinkage porosity, and its elongation and ultimate tensile strength was enhanced 45% and 105% higher than those of the as-cast 7075 aluminum alloy, respectively. When the Ni content was increased to 1.2%, the eutectic phases of the alloy became much coarser compared to the other two alloys, and the mechanical properties obviously reduced too. Full article
(This article belongs to the Special Issue Micro-Structure and Mechanical Properties of Alloys)
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18 pages, 5329 KiB  
Article
Growth, Structure, Spectroscopy, and Laser Operation of a “Mixed” Yb:(Y,Lu)3Al5O12 Garnet Crystal
Crystals 2023, 13(11), 1588; https://doi.org/10.3390/cryst13111588 - 15 Nov 2023
Viewed by 689
Abstract
A single crystal of ytterbium-doped “mixed” yttrium–lutetium aluminum garnet with a stoichiometric composition of (Y0.601Lu0.233Yb0.166)3Al5O12 was grown by the Czochralski method and its structure, vibronic, spectroscopic, and laser properties were studied. The [...] Read more.
A single crystal of ytterbium-doped “mixed” yttrium–lutetium aluminum garnet with a stoichiometric composition of (Y0.601Lu0.233Yb0.166)3Al5O12 was grown by the Czochralski method and its structure, vibronic, spectroscopic, and laser properties were studied. The stimulated-emission cross-section for Yb3+ ions was maximized to 2.53 × 10−20 cm2 at 1031 nm. The emission bandwidth was ~8 nm, and the reabsorption-free luminescence lifetime of the 2F5/2 state was 1.063 ms. Pumped at 941 nm, the Yb laser generated a maximum output power of 1.04 W at 1.03 and 1.05 μm with a high slope efficiency of 76.4% and a laser threshold of 76 mW. A continuous wavelength tuning over a range of 51.6 nm (1026.4–1078.0 nm) was also achieved. Power scaling was achieved using a 969 nm diode-pumped microchip cavity. A maximum output power of ~9 W was obtained at 1.05 μm with a slope efficiency of 76% and an almost circular laser beam profile. Full article
(This article belongs to the Special Issue Rare Earths-Doped Materials (3rd Edition))
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11 pages, 3959 KiB  
Communication
Construction of Energetic Complexes Based on LLM-105 and Transition Metal Cations (Ni, Co, Mn, and Cu)
Crystals 2023, 13(11), 1587; https://doi.org/10.3390/cryst13111587 - 15 Nov 2023
Viewed by 684
Abstract
Energetic complexes represent a crucial research direction for the design and synthesis of novel energetic materials. In this work, 2,6-diamino-3,5-dinitropyrazine-1-oxide (LLM-105), a significant explosive compound with exceptional comprehensive properties, was selected as the ligand for coordinating with various metal ions. Four novel energetic [...] Read more.
Energetic complexes represent a crucial research direction for the design and synthesis of novel energetic materials. In this work, 2,6-diamino-3,5-dinitropyrazine-1-oxide (LLM-105), a significant explosive compound with exceptional comprehensive properties, was selected as the ligand for coordinating with various metal ions. Four novel energetic complexes, Ni(C4H3N6O5)2·DMF (1), Co(C4H3N6O5)2·2DMF (2), Mn(C4H3N6O5)3·3/2DMF (3), and Cu3(C4H2N6O5)3·3DMF (4) were successfully synthesized, and their crystal structures were identified by a single-crystal X-ray diffraction technique. The structural analyses illustrated that LLM-105 can form either a mononuclear metal complex after the deprotonation of one amino group or a trinuclear metal complex after the deprotonation of two amino groups. Compound 1 exhibits a planar quadrilateral geometry, while both compounds 2 and 3 display distorted octahedral configurations. Compound 4 has three metal centers and exhibits two coordination configurations of distorted tetragonal pyramid geometry and planar quadrilateral geometry. The detonation performances of compounds 14 were also theoretically calculated, revealing their favorable explosive properties. These findings emphasize the diverse coordination modes of LLM-105 and the structural variability and adjustability of its complexes, offering valuable insights for regulating both the structure and performance of the LLM-105 complex as well as researching its deprotonation. Full article
(This article belongs to the Special Issue Coordination Complexes: Synthesis, Characterization and Application)
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11 pages, 2175 KiB  
Article
The Effects of Chlorine Doping on the Thermoelectric Properties of Bi2O2Se
Crystals 2023, 13(11), 1586; https://doi.org/10.3390/cryst13111586 - 15 Nov 2023
Viewed by 643
Abstract
In this study, we investigate the effects of chlorine doping on the structural, electronic, and thermoelectric properties of Bi2O2Se by employing density functional theory combined with semiclassical Boltzmann transport theory. It is shown that chlorine doping has significant effects [...] Read more.
In this study, we investigate the effects of chlorine doping on the structural, electronic, and thermoelectric properties of Bi2O2Se by employing density functional theory combined with semiclassical Boltzmann transport theory. It is shown that chlorine doping has significant effects on the electronic structure and thermoelectric properties of Bi2O2Se. As chlorine is incorporated into the selenium sites in Bi2O2Se, additional electrons are acquired, thereby inducing metallic properties in chlorine-doped Bi2O2Se. Meanwhile, Cl doping leads to an increase in the electrical conductivity of Bi2O2Se at room temperature by 25 times (from 358.59 S/cm to 9390 S/cm), and the power factor is enhanced by a factor of 2.12 (from 4.04 mW/mK2 to 12.59 mW/mK2). This study demonstrates that chlorine doping is an effective method to modify the physical properties of Bi2O2Se. Full article
(This article belongs to the Special Issue Density Functional Theory (DFT) and Beyond for Crystalline Materials)
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14 pages, 4522 KiB  
Article
Thermoluminescent and Dosimetric Properties of Zirconium Dioxide Ceramics Irradiated with High Doses of Pulsed Electron Beam
Crystals 2023, 13(11), 1585; https://doi.org/10.3390/cryst13111585 - 14 Nov 2023
Cited by 1 | Viewed by 604
Abstract
Thermoluminescent (TL) properties of monoclinic zirconium dioxide ceramics were studied in order to assess the possibility of their use for measuring high doses (on the order of kGy) of pulsed electron beams (130 keV). Two types of samples were used: those synthesized by [...] Read more.
Thermoluminescent (TL) properties of monoclinic zirconium dioxide ceramics were studied in order to assess the possibility of their use for measuring high doses (on the order of kGy) of pulsed electron beams (130 keV). Two types of samples were used: those synthesized by sintering in an electric furnace at T = 700–1700 °C and those synthesized in a flow of high-energy electrons (1.4 MeV) with a high power density. Analysis of the X-ray diffraction patterns using the Scherrer method revealed that annealing of ceramics of the first type at T > 1000 °C leads to a significant increase in the size of crystallites, which correlates with a significant increase in the intensity of the TL peak at 390 K. Type 2 ceramics synthesized by the electron beam method have the maximum TL response. Using the peak shape analysis method, the kinetic parameters of TL (activation energy, frequency factor, and kinetic order) were calculated. This study marks the first instance of establishing the patterns of influence of synthesis conditions and crystallite size on their values. The presence of an intense isolated TL peak, the sublinear nature of most dose dependencies, and negligible fading indicate the promise of the ceramics synthesized in this work for measuring high doses (several to tens of kGy). Full article
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16 pages, 3473 KiB  
Article
Influence of the Process Parameters on the Synthesis of Urea Phosphate and the Properties of the Obtained Product
Crystals 2023, 13(11), 1584; https://doi.org/10.3390/cryst13111584 - 14 Nov 2023
Viewed by 935
Abstract
The ever-increasing food demand associated with the growing human population poses similar challenges to both farmers and fertilizer producers. In view of climate change and the increasing area of infertile land, it is very important to use correctly balanced and highly effective fertilizers [...] Read more.
The ever-increasing food demand associated with the growing human population poses similar challenges to both farmers and fertilizer producers. In view of climate change and the increasing area of infertile land, it is very important to use correctly balanced and highly effective fertilizers in agriculture. Water-soluble fertilizers are becoming more and more popular. It is convenient to use them together with irrigation water because this reduces the negative effects of droughts and accelerates the assimilation of nutrients needed by plants. The aim of this work was to synthesize urea phosphate (UP) (water-soluble complex nitrogen–phosphorus fertilizers NPF) through the reaction of phosphoric acid and urea. The most important moment of the work is that the synthesis was carried out using a purified wet-process phosphoric acid (PWPA) and urea by varying the stoichiometric ratio and the duration time of crystallization. Based on the results of the experiment, it was found that, in the presence of excess acid, the concentration of phosphorus pentoxide (P2O5) is too high, the concentration of amide nitrogen (Namide) is too low, and vice versa. The best ratio of P2O5 and Namide was determined when both reactants were used in a ratio of 1.0:1.0. Crystallization was carried out at 20 °C with different reaction times: 30, 60, 90 and 120 min. Analysis of the chemical composition of the synthesized urea phosphate and determination of the main components, i.e., Namide and P2O5 concentrations, were performed using standard fertilizer analysis methods. Using the optical emission spectroscopy, the concentrations of chemical elements (sulphur, aluminium, iron, calcium, magnesium, silicon, etc.) were also determined in the synthesized product. During the experiment, not only the chemical composition of the product, but also the resulting crystals of the product, and their size and shape—properties that are highly dependent on the duration of crystallization—were analysed. The thermal stability of UP crystals was investigated using simultaneous thermal analysis; the crystallinity of UP was determined using X-ray diffraction analysis; the identification of groups of chemical elements was carried out using Fourier Transform Infrared spectroscopy analysis; the shape and size of crystals were investigated using scan electron microscopy and optical microscope techniques. Full article
(This article belongs to the Section Inorganic Crystalline Materials)
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20 pages, 5203 KiB  
Article
X-ray Diffraction, Spectroscopy, Optical Properties, NPA, NBO, FMO, and Hirshfeld Surface Analyses of Two Newly Synthesized Piperidinium Ionic Liquids
Crystals 2023, 13(11), 1583; https://doi.org/10.3390/cryst13111583 - 14 Nov 2023
Viewed by 645
Abstract
The present study elaborates on the synthesis, crystal structure, and computational studies of two new ionic liquids. In the crystal structure, [C5H12N][C21H14ClN2O2S] (4a), the anions form chains along the [...] Read more.
The present study elaborates on the synthesis, crystal structure, and computational studies of two new ionic liquids. In the crystal structure, [C5H12N][C21H14ClN2O2S] (4a), the anions form chains along the a-axis direction through C—H···π(ring) interactions. These are connected into layers that run approximately parallel to the ac plane by a variety of hydrogen bonds. In the compound structure, [C5H12N][C18H15N2O2S] (4b), the two ions are primarily associated by an N—H···N hydrogen bond. In the crystal structure, layers parallel to the bc plane are formed by pairs of C—H···O and N—H···S hydrogen bonds and by C—H···π(ring) interactions. A theoretical study reveals that 4a has lower energy than 4b and is more stable. The NBO and DOS studies further confine the liquids’ structural reactivity and electronic properties. The quantum theory of atoms in a molecule (QTAIM) analysis reveals the important non-covalent interactions among the fragments and charge transfer. The global reactivity descriptors indicate their molecular reactivity relationship with the presence of functional groups. The remarkable polarizability (αo) and hyperpolarizability (βo) values indicate their optical and nonlinear optical (NLO) properties. Furthermore, the analysis performed by CrystalExplorer shows the intermolecular interactions and reactive sites between cations and anions in ionic liquids. The 2D fingerprint plots and Hirshfeld surfaces indicate the major interactions of crystals with neighboring elements in crystal packing. For both compounds, the H···H interactions are significantly higher than the other element interactions. Full article
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13 pages, 28107 KiB  
Article
Solidification Segregation Behavior and Homogenization Process of a Difficult-to-Deform Superalloy Used at 850 °C
Crystals 2023, 13(11), 1582; https://doi.org/10.3390/cryst13111582 - 14 Nov 2023
Viewed by 647
Abstract
Solidification segregation behavior and homogenization heat treatment processes of a difficult-to-deform superalloy for use at 850 °C were studied. Additionally, the effect of carbon content on homogenization, the thermal treatment process, and pore growth behavior within the alloy were discussed. Our results revealed [...] Read more.
Solidification segregation behavior and homogenization heat treatment processes of a difficult-to-deform superalloy for use at 850 °C were studied. Additionally, the effect of carbon content on homogenization, the thermal treatment process, and pore growth behavior within the alloy were discussed. Our results revealed that Al, Ti, and Nb elements are distributed in the interdendritic space, while W and Mo elements are distributed in the dendrite. There is a significant quantity of γ-γ′ eutectic and MC carbide precipitates in the interdendritic space. Notably, for the alloy containing 0.1 wt% C, a homogenization heat treatment at 1200 °C for 48 h can effectively eliminate the segregation and undesirable phases. As carbon content increased, the γ-γ′ eutectic phases diminished, and the homogenization time decreased accordingly. In this context, pores are smaller and more dispersed, which may enhance alloy forging properties. Full article
(This article belongs to the Special Issue Ni (Co)-Based Superalloys)
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10 pages, 3118 KiB  
Article
Unraveling the Effect of Compositional Ratios on the Kesterite Thin-Film Solar Cells Using Machine Learning Techniques
Crystals 2023, 13(11), 1581; https://doi.org/10.3390/cryst13111581 - 12 Nov 2023
Cited by 1 | Viewed by 938
Abstract
In the Kesterite family, the Cu2ZnSn(S,Se)4 (CZTSSe) thin-film solar cells (TFSCs) have demonstrated the highest device efficiency with non-stoichiometric cation composition ratios. These composition ratios have a strong influence on the structural, optical, and electrical properties of the CZTSSe absorber [...] Read more.
In the Kesterite family, the Cu2ZnSn(S,Se)4 (CZTSSe) thin-film solar cells (TFSCs) have demonstrated the highest device efficiency with non-stoichiometric cation composition ratios. These composition ratios have a strong influence on the structural, optical, and electrical properties of the CZTSSe absorber layer. So, in this work, a machine learning (ML) approach is employed to evaluate effect composition ratio on the device parameters of CZTSSe TFSCs. In particular, the bi-metallic ratios like Cu/Sn, Zn/Sn, Cu/Zn, and overall Cu/(Zn+Sn) cation composition ratio are investigated. To achieve this, different machine learning algorithms, such as decision trees (DTs) and classification and regression trees (CARTs), are used. In addition, the output performance parameters of CZTSSe TFSCs are predicted by both continuous and categorical approaches. Artificial neural networks (ANN) and XGBoost (XGB) algorithms are employed for the continuous approach. On the other hand, support vector machine and k-nearest neighbor’s algorithms are also used for the categorical approach. Through the analysis, it is observed that the DT and CART algorithms provided a critical composition range well suited for the fabrication of highly efficient CZTSSe TFSCs, while the XGB and ANN showed better prediction accuracy among the tested algorithms. The present work offers valuable guidance towards the integration of the ML approach with experimental studies in the field of TFSCs. Full article
(This article belongs to the Special Issue Progress and Prospects of Perovskite Films)
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17 pages, 12209 KiB  
Article
Gemological, Spectral and Chemical Features of Canary Yellow Chrysoberyl
Crystals 2023, 13(11), 1580; https://doi.org/10.3390/cryst13111580 - 11 Nov 2023
Viewed by 776
Abstract
In this study, seventeen faceted gem-quality chrysoberyls exhibiting an attractive canary yellow color were investigated using a variety of gemological, spectral, and chemical methods. Microscopic observation revealed the presence of distinct growth lines and inclusions, including CO2 fluids, carbon, and crystals of [...] Read more.
In this study, seventeen faceted gem-quality chrysoberyls exhibiting an attractive canary yellow color were investigated using a variety of gemological, spectral, and chemical methods. Microscopic observation revealed the presence of distinct growth lines and inclusions, including CO2 fluids, carbon, and crystals of mineral such as calcite, quartz, sillimanite, and mica, identified by the Raman spectrum. The FTIR spectra showed the characteristic peaks of 2405 and 2160 cm−1 and a 3223 cm−1 peak in all samples, which can be accompanied by the 3112 cm−1 shoulder, 3301, and 3412 and 3432 cm−1 peaks. The UV-Vis spectra showed an Fe-related peak at 440 nm, along with the 650–660 nm band and the absorption band in the blue zone of visible light. Chemical analyses via EDXRF showed a composition poor in V and Cr and rich in Fe. The spectral and chemical results could help explain the origin of the canary yellow color, which originates from the abundant amount of Fe with very little influence from Cr and V. Full article
(This article belongs to the Section Mineralogical Crystallography and Biomineralization)
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15 pages, 6945 KiB  
Article
Biosynthesis Effect of Egg White on Formation and Characteristics of NiO/NiCo2O4 Nanocomposites
Crystals 2023, 13(11), 1579; https://doi.org/10.3390/cryst13111579 - 09 Nov 2023
Viewed by 638
Abstract
For the successful production of NiO/NiCo2O4 nanocomposites, the environmentally friendly method of egg white supplementation has been used. Several analytical techniques were employed to characterize the morphology, purity, and crystal structure of the as-prepared nanocomposites. These techniques included transmission electron [...] Read more.
For the successful production of NiO/NiCo2O4 nanocomposites, the environmentally friendly method of egg white supplementation has been used. Several analytical techniques were employed to characterize the morphology, purity, and crystal structure of the as-prepared nanocomposites. These techniques included transmission electron microscopy (TEM), Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and X-ray diffraction (XRD). The physical adsorption and magnetic properties of the investigated composite were determined using the Brunauer–Emmett–Teller (BET) method and a vibrating-sample magnetometer (VSM), respectively. The results have shown that the as-prepared composite particles had diameters of about 10–25 nm, with uniform distribution. The XRD analysis showed that the as-synthesized composites consisted entirely of cubic structures of both NiO and spinel NiCo2O4 nanoparticles, with a space group of Fd3m. The FTIR analysis showed characteristic vibration modes related to metal oxides, confirming the formation of composites containing NiO and NiCo2O4 crystallites. The investigated composites’ saturation magnetization (MS) and coercivity (HC) were easily controllable because of the ingredients’ ferromagnetic (NiCo2O4) and antiferromagnetic (NiO) characteristics. The excellent combination of the NiO/NiCo2O4 nanocomposites’ properties is anticipated to make this system suitable for a wide range of applications. Full article
(This article belongs to the Special Issue Crystalline Magnetic Compounds)
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8 pages, 2227 KiB  
Article
Innovative Method for the Mass Preparation of α″-Fe16N2 Powders via Gas Atomization
Crystals 2023, 13(11), 1578; https://doi.org/10.3390/cryst13111578 - 09 Nov 2023
Viewed by 704
Abstract
The iron nitride materials, especially α″-Fe16N2, are considered one of the most promising candidates for future rare-earth-free magnets. However, the mass production of α″-Fe16N2 powders as a raw material for permanent magnets is still challenging. In [...] Read more.
The iron nitride materials, especially α″-Fe16N2, are considered one of the most promising candidates for future rare-earth-free magnets. However, the mass production of α″-Fe16N2 powders as a raw material for permanent magnets is still challenging. In this work, starting from iron lumps as a raw material, we have managed to prepare the α″-Fe16N2 powders via the gas atomization method, followed by subsequent nitriding in an ammonia–hydrogen gas mixture stream. The particle size was controlled by changing the gas atomization preparation conditions. X-ray diffractograms (XRD) analyses show that the prepared powders are composed of α″-Fe16N2 and α-Fe phases. The α″-Fe16N2 volume ratio increases with decreasing powder size and increasing nitriding time, reaching a maximum of 57% α″-Fe16N2 phase in powders with size below 32 ± 3 μm after 96 h nitridation. The saturation magnetization reaches the value of 237 emu/g and a reasonable coercivity value of 884 Oe. Compared to the saturation magnetization values of α-Fe powders, the α″-Fe16N2 powders prepared through our proposed approach show an increase of up to 10% in saturation and demonstrate the possibility of mass production of α″-Fe16N2 powders as precursors of permanent magnets without rare earths. Full article
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