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Crystals, Volume 10, Issue 3 (March 2020) – 94 articles

Cover Story (view full-size image): Curcumin and its derivatives demethoxycurcumin (DMC) and bis(demethoxy)curcumin (BDMC) are natural ingredients of the plant rhizome of Curcuma longa L. Together they are known as curcuminoids. Despite their strong similarity in molecular structure, their pharmacological activity and therapeutic effects can differ, which requires isolation of curcumin in pure state. In the article, crystallization-based separation of curcumin from extract-similar curcuminoid mixtures is studied. Based on solubility and supersolubility data of pure curcumin and curcumin in the initial mixture, seeded cooling crystallization procedures were derived using different solvents/solvent systems. As a result, crystalline curcumin of up to 99.4% purity, free of BDMC and depleted DMC content, was provided in a simple single crystallization step. Opportunities to further enhance total curcumin recovery by optimizing the [...] Read more.
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9 pages, 2336 KiB  
Article
The Investigation for Coating Method of Titanium Dioxide Layer in Perovskite Solar Cells
by Pao-Hsun Huang, Chien-Wu Huang, Chih-Chieh Kang, Chia-Hsun Hsu, Shui-Yang Lien, Na-Fu Wang and Chien-Jung Huang
Crystals 2020, 10(3), 236; https://doi.org/10.3390/cryst10030236 - 24 Mar 2020
Cited by 7 | Viewed by 4102
Abstract
The effect of conventional Perovskite solar cells (PSCs) by using different concentration and spin-coating speeds of titanium dioxide (TiO2) as an electron transport layer (ETL) was studied. The influence of TiO2 based on device structure: fluorine-doped tin oxide substrate/TiO2 [...] Read more.
The effect of conventional Perovskite solar cells (PSCs) by using different concentration and spin-coating speeds of titanium dioxide (TiO2) as an electron transport layer (ETL) was studied. The influence of TiO2 based on device structure: fluorine-doped tin oxide substrate/TiO2/Perovskite (CH3NH3PbI3)/2,2′,7,7′-Tetrakis[N,N-di(4-methoxyp phenyl)amino]-9,9′-spirobifluorene/silver, is also studied. The spin-coating speed is varied in a range from 1000 to 3000 rpm to get optimal performance of device. The optimized power conversion efficiency (PCE) of PSCs with original concentration (OC) and double concentration (DC) TiO2 is 8.74 and 9.93%, respectively. The reason is attributed to excellent absorption in shorter wavelength, compact characteristic, and suitable thickness of TiO2, leading to perfect short-circuit current density (Jsc), lower series resistance (Rs), and higher fill factor (FF) of 0.75. Besides, recombination of electron and hole is also decreased due to the compact feature, leading to higher open-circuit voltage (VOC) of 0.91 V. Full article
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13 pages, 2520 KiB  
Article
Exploring the Chelating Potential of an Easily Synthesized Schiff Base for Copper Sensing
by Jesús Sanmartín-Matalobos, Ana García-Deibe, Morteza Zarepour-Jevinani, Manuel Aboal-Somoza, Pilar Bermejo-Barrera and Matilde Fondo
Crystals 2020, 10(3), 235; https://doi.org/10.3390/cryst10030235 - 24 Mar 2020
Cited by 10 | Viewed by 2619
Abstract
The present study deals with the investigation of Cu2+, Ni2+ and Pd2+ chelating potential of the Schiff base, (E)-N-(2-((2-hydroxybenzylidene)amino)benzyl)-4-methylbenzenesulfonamide (H2SB). Crystal structures of Ni(HSB)2, Pd(HSB)2 and Cu(HSB)2 have been [...] Read more.
The present study deals with the investigation of Cu2+, Ni2+ and Pd2+ chelating potential of the Schiff base, (E)-N-(2-((2-hydroxybenzylidene)amino)benzyl)-4-methylbenzenesulfonamide (H2SB). Crystal structures of Ni(HSB)2, Pd(HSB)2 and Cu(HSB)2 have been elucidated from single crystal X-ray diffraction data. NMR spectroscopy showed the presence of two conformers of Pd(HSB)2 in solution, both with an E configuration of the ligand. The determination of binding constants by fluorescence quenching showed that affinity of H2SB to Cu2+ in solution is higher than for Ni2+ and Pd2+. Since there is a high demand for selective, sensitive, rapid and simple methods to detect copper in aqueous samples (both as Cu2+ ions and as CuO NPs), we have explored H2SB as an optical chemosensor. H2SB interacts with increasing concentrations of Cu2+ ions, giving rise to a linear increase in the absorbance of a band centered at about 392 nm. H2SB displays a high selectivity toward Cu2+, even in the presence of the most common metal ions in water (Ca2+, Mg2+, Na+, K+, Al3+ and Fe3+), and some heavy transition metal ions such as the soft acids Pd2+ and Cd2+. H2SB also interacts with increasing concentrations of CuO NPs, which gives rise to a linear decrease in its fluorescence intensity (λem = 500 nm, λex = 390 nm). Quenching has occurred as a result of the formation of a non-fluorescent ground-state surface complex H2SB–CuO NPs. The limits of detection and quantification of CuO NPs were 9.8 mg/L and 32.6 mg/L, respectively. The presence of TiO2, Ag and Au NPs does not interfere with the determination of CuO NPs. Full article
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14 pages, 2276 KiB  
Article
First Principles Study on the Thermodynamic and Elastic Mechanical Stability of Mg2X (X = Si,Ge) Intermetallics with (anti) Vacancy Point Defects
by Yuhong Zhao, Jinzhong Tian, Guoning Bai, Leting Zhang and Hua Hou
Crystals 2020, 10(3), 234; https://doi.org/10.3390/cryst10030234 - 23 Mar 2020
Cited by 12 | Viewed by 3157
Abstract
In this paper, based on the density functional theory, through thermodynamic and mechanical stability criteria, the crystal cell model of intermetallic compounds with vacancy and anti-site point defects is constructed and the lattice constant, formation heat, binding energy, elastic constant, and elastic modulus [...] Read more.
In this paper, based on the density functional theory, through thermodynamic and mechanical stability criteria, the crystal cell model of intermetallic compounds with vacancy and anti-site point defects is constructed and the lattice constant, formation heat, binding energy, elastic constant, and elastic modulus of Mg2X (X = Si, Ge) intermetallics with or without point defects are calculated. The results show that the difference in the atomic radius leads to the instability and distortion of crystal cells with point defects; Mg2X are easier to form vacancy defects than anti-site defects on the X (X = Si, Ge) lattice site, and form anti-site defects on the Mg lattice site. Generally, the point defect is more likely to appear at the Mg position than at the Si or Ge position. Among the four kinds of point defects, the anti-site defect x M g is the easiest to form. The structure of intermetallics without defects is more stable than that with defects, and the structure of the intermetallics with point defects at the Mg position is more stable than that at the Si/Ge position. The anti-site and vacancy defects will reduce the material’s resistance to volume deformation shear strain, and positive elastic deformation, and increase the mechanical instability of the elastic deformation of the material. Compared with the anti-site point defect, the void point defect can lead to the mechanical instability of the transverse deformation of the material and improve the plasticity of the material. The research in this paper is helpful for the analysis of the mechanical stability of the elastic deformation of Mg2X (X = Si, Ge) intermetallics under the service condition that it is easy to produce vacancy and anti-site defects. Full article
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12 pages, 10996 KiB  
Article
Microrelief of Rounded Diamond Crystals as an Indicator of the Redox Conditions of Their Resorption in a Kimberlite Melt
by Alexander F. Khokhryakov, Denis V. Nechaev and Alexander G. Sokol
Crystals 2020, 10(3), 233; https://doi.org/10.3390/cryst10030233 - 23 Mar 2020
Cited by 6 | Viewed by 3939
Abstract
We conducted a detailed study of the morphology of diamond crystals partially dissolved in a water-bearing kimberlite melt at pressure of 6.3 GPa, temperature of 1400 °C, and two oxygen fugacities (fO2) corresponding to the Re-ReO2 buffer and near the [...] Read more.
We conducted a detailed study of the morphology of diamond crystals partially dissolved in a water-bearing kimberlite melt at pressure of 6.3 GPa, temperature of 1400 °C, and two oxygen fugacities (fO2) corresponding to the Re-ReO2 buffer and near the magnetite–hematite (MH) buffer. The triangular etch pits on the {111} faces, which formed during experimental diamond dissolution, were found to completely correspond to negative trigons on natural diamond crystals in the shape and sidewalls inclination angle. Furthermore, two experimental fO2 values were associated with two relief types of the rounded tetrahexahedroid surfaces typical of natural rounded diamonds. Therefore, the surface microrelief on rounded natural diamond crystals was concluded to be an indicator of the redox conditions of natural diamond resorption. Full article
(This article belongs to the Special Issue Diamond Crystals Volume II)
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12 pages, 12639 KiB  
Article
The Effect of Lath Martensite Microstructures on the Strength of Medium-Carbon Low-Alloy Steel
by Chen Sun, Paixian Fu, Hongwei Liu, Hanghang Liu, Ningyu Du and Yanfei Cao
Crystals 2020, 10(3), 232; https://doi.org/10.3390/cryst10030232 - 23 Mar 2020
Cited by 36 | Viewed by 4151
Abstract
Different austenitizing temperatures were used to obtain medium-carbon low-alloy (MCLA) martensitic steels with different lath martensite microstructures. The hierarchical microstructures of lath martensite were investigated by optical microscopy (OM), electron backscattering diffraction (EBSD), and transmission electron microscopy (TEM). The results show that with [...] Read more.
Different austenitizing temperatures were used to obtain medium-carbon low-alloy (MCLA) martensitic steels with different lath martensite microstructures. The hierarchical microstructures of lath martensite were investigated by optical microscopy (OM), electron backscattering diffraction (EBSD), and transmission electron microscopy (TEM). The results show that with increasing the austenitizing temperature, the prior austenite grain size and block size increased, while the lath width decreased. Further, the yield strength and tensile strength increased due to the enhancement of the grain boundary strengthening. The fitting results reveal that only the relationship between lath width and strength followed the Hall–Petch formula of. Hence, we propose that lath width acts as the effective grain size (EGS) of strength in MCLA steel. In addition, the carbon content had a significant effect on the EGS of martensitic strength. In steels with lower carbon content, block size acted as the EGS, while, in steels with higher carbon content, the EGS changed to lath width. The effect of the Cottrell atmosphere around boundaries may be responsible for this change. Full article
(This article belongs to the Special Issue Microstructural and Mechanical Characterization of Alloys)
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10 pages, 3693 KiB  
Article
Environmentally Friendly and Cost-Effective Synthesis of Carbonaceous Particles for Preparing Hollow SnO2 Nanospheres and their Bifunctional Li-Storage and Gas-Sensing Properties
by Yingyi Ding, Ping Zhou, Tianli Han and Jinyun Liu
Crystals 2020, 10(3), 231; https://doi.org/10.3390/cryst10030231 - 23 Mar 2020
Cited by 4 | Viewed by 2044
Abstract
The templated preparation of hollow nanomaterials has received broad attention. However, many templates are expansive, environmentally-harmful, along with involving a complicated preparation process. Herein, we present a cost-effective, environmentally friendly and simple approach for making carbonaceous particles which have been demonstrated as efficient [...] Read more.
The templated preparation of hollow nanomaterials has received broad attention. However, many templates are expansive, environmentally-harmful, along with involving a complicated preparation process. Herein, we present a cost-effective, environmentally friendly and simple approach for making carbonaceous particles which have been demonstrated as efficient templates for preparing hollow nanospheres. Natural biomass, such as wheat or corn, is used as the source only, and thus other chemicals are not needed. The carbonaceous particles possess abundant hydroxyl and carboxyl groups, enabling them to efficiently adsorb metal ions in solution. The prepared SnO2 hollow spheres were used in a lithium-ion (Li-ion) battery anode, and as the sensing layer of a gas sensor, respectively. After charge–discharge for 200 times at a rate of 1 C, the anodes exhibit a stable capacity of 500 mAh g−1, and a Coulombic efficiency as high as 99%. In addition, the gas sensor based on the SnO2 hollow spheres shows a high sensing performance towards ethanol gas. It is expected that the presented natural biomass-derived particles and their green preparation method will find more applications for broad research fields, including energy-storage and sensors. Full article
(This article belongs to the Section Crystalline Materials)
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12 pages, 4677 KiB  
Article
Halogen Bonding Provides Heterooctameric Supramolecular Aggregation of Diaryliodonium Thiocyanate
by Natalia S. Soldatova, Vitalii V. Suslonov, Troyana Yu. Kissler, Daniil M. Ivanov, Alexander S. Novikov, Mekhman S. Yusubov, Pavel S. Postnikov and Vadim Yu. Kukushkin
Crystals 2020, 10(3), 230; https://doi.org/10.3390/cryst10030230 - 22 Mar 2020
Cited by 29 | Viewed by 3342
Abstract
The crystal structure of the newly synthesized 4-methoxyphenyl(phenyl)iodonium thiocyanate, [PhI(4-C6H4OMe)](SCN), represents the first example of 16-membered cyclic heterooctamer formed by halogen bonding between the iodonium cation and SCN. Results of density functional theory (DFT) calculations followed by [...] Read more.
The crystal structure of the newly synthesized 4-methoxyphenyl(phenyl)iodonium thiocyanate, [PhI(4-C6H4OMe)](SCN), represents the first example of 16-membered cyclic heterooctamer formed by halogen bonding between the iodonium cation and SCN. Results of density functional theory (DFT) calculations followed by the topological analysis of the electron density distribution within the framework of the quantum theory of atoms in molecules (QTAIM) method at the ωB97XD/DZP-DKH level of theory reveal that energies of attractive intermolecular noncovalent interactions I···S and I···N (responsible for the formation of heterooctameric supramolecular clusters {PhI(4-C6H4OMe)}4·{SCN}4 in the solid state structure of [PhI(4-C6H4OMe)](SCN)) vary from 0.9 to 8.5 kcal/mol. Full article
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11 pages, 6611 KiB  
Article
Study on Transformation Mechanism and Kinetics of α’ Martensite in TC4 Alloy Isothermal Aging Process
by Hui Yu, Wei Li, Songsong Li, Haibei Zou, Tongguang Zhai and Ligang Liu
Crystals 2020, 10(3), 229; https://doi.org/10.3390/cryst10030229 - 22 Mar 2020
Cited by 10 | Viewed by 2634
Abstract
The law of microstructure evolution and transformation mechanism of the α′ martensite decomposition during 400–600 °C were studied by the isothermal dilatometry. The transformation process of α′ martensite was quantitatively characterized based on Johnson–Mehl–Avrami (JMA) model, and the microstructure evolution under different aging [...] Read more.
The law of microstructure evolution and transformation mechanism of the α′ martensite decomposition during 400–600 °C were studied by the isothermal dilatometry. The transformation process of α′ martensite was quantitatively characterized based on Johnson–Mehl–Avrami (JMA) model, and the microstructure evolution under different aging processes was observed and compared on Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM). The results showed that α′ → α + β is the elemental diffusion transformation, the position and shape of the precipitate gradually change with the holding time and temperature. The decomposition rate of α′ martensite was positively correlated with the aging temperature. The whole transformation process was divided into two stages based on the value of the Avrami exponent n, and the corresponding average values of the transformation activation energies Q are 46.1 kJ/mol and 116.8 kJ/mol, respectively. The calculated model had good agreement with the experimental data, and the transformation curve of α′ martensite with time and temperature during the isothermal aging at 400–600 °C was drawn. Full article
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9 pages, 3404 KiB  
Article
Reconfigurable Polarizer Based on Bulk Dirac Semimetal Metasurface
by Yannan Jiang, Jing Zhao and Jiao Wang
Crystals 2020, 10(3), 228; https://doi.org/10.3390/cryst10030228 - 21 Mar 2020
Cited by 7 | Viewed by 2969
Abstract
In this paper, we propose a reflective polarizer in terahertz regime, which utilizes the Bulk-Dirac-Semimetal (BDS) metasurface can be dynamically tuned in broadband. The proposed polarizer is capable of converting the linear polarized wave into the circular polarized or the cross polarized waves [...] Read more.
In this paper, we propose a reflective polarizer in terahertz regime, which utilizes the Bulk-Dirac-Semimetal (BDS) metasurface can be dynamically tuned in broadband. The proposed polarizer is capable of converting the linear polarized wave into the circular polarized or the cross polarized waves by adjusting the Fermi energy (EF) of the BDS. In the frequency range of 0.51 THz and 1.06 THz, the incident linear polarized wave is converted into a circular polarized wave with an axial ratio (AR) less than 3 dB when EF = 30 meV. When EF = 45 meV, the cross-polarization conversion is achieved with the polarization conversion ratio (PCR) greater than 90% in the band of 0.57−1.12 THz. Meanwhile, the conversion efficiencies for both polarization conversions are in excess of 90%. Finally, the physical mechanism is revealed by the decomposition of two orthogonal components and the verification is presented by the interference theory. Full article
(This article belongs to the Special Issue Metamaterials)
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12 pages, 6995 KiB  
Article
Transmission Characteristics of Ultrasonic Longitudinal Wave Signals in Negative Refractive Index Materials
by Yixue Geng, Yunqiang Sun, Peng Yang, Xin Liu and Jianning Han
Crystals 2020, 10(3), 227; https://doi.org/10.3390/cryst10030227 - 21 Mar 2020
Cited by 1 | Viewed by 5284
Abstract
Longitudinal waves have important applications in modern scientific research and production; as a special acoustic wave, longitudinal waves have a sound transmission performance in negative refractive index materials. This paper has designed a new structure for negative refractive index materials by virtue of [...] Read more.
Longitudinal waves have important applications in modern scientific research and production; as a special acoustic wave, longitudinal waves have a sound transmission performance in negative refractive index materials. This paper has designed a new structure for negative refractive index materials by virtue of COMSOL software and conducted related simulation analysis. Experimental results illustrated that the structure designed had good acoustic longitudinal wave transmission performance. Besides, the effect of sound wave focusing could be achieved by a combination of existing test methods. The design proposed could break the limitation of previous structures on acoustic longitudinal wave transmission. This study is expected to have important implications for the development of solid metamaterial structures. Full article
(This article belongs to the Special Issue Metamaterials)
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17 pages, 4135 KiB  
Article
A Comparative Study of Theoretical Methods to Estimate Semiconductor Nanoparticles’ Size
by Fernando Rodríguez-Mas, Juan Carlos Ferrer, José Luis Alonso, David Valiente and Susana Fernández de Ávila
Crystals 2020, 10(3), 226; https://doi.org/10.3390/cryst10030226 - 21 Mar 2020
Cited by 30 | Viewed by 3595
Abstract
In this paper, we compare four different methods to estimate nanoparticle diameters from optical absorption measurements, using transmission electron microscopy (TEM) images as a reference for the nanoparticle size. Three solutions of colloidal nanoparticles coated with thiophenol with different diameters were synthesized by [...] Read more.
In this paper, we compare four different methods to estimate nanoparticle diameters from optical absorption measurements, using transmission electron microscopy (TEM) images as a reference for the nanoparticle size. Three solutions of colloidal nanoparticles coated with thiophenol with different diameters were synthesized by thiolate decomposition. The nanoparticle sizes were controlled by the addition of a certain volume of a 1% sulphur solution in toluene. TEM measurements showed that the average diameter for each type of these nanoparticles was 2.8 nm, 3.2 nm, and 4.0 nm. The methods studied for the calculation of the nanoparticles diameter were: The Brus model, the hyperbolic band model (HBM), the Henglein model, and the Yu equation. We evaluated the importance of a good knowledge of the nanoparticle bandgap energy, and the nature of electronic transitions in the semiconductor. We studied the effects that small variations in the electron and hole effective mass values produced in the Brus equation and in the HBM model for CdS, PbS, and ZnS nanoparticles. Finally, a comparison was performed between the data provided by these models and the experimental results obtained with TEM images. In conclusion, we observed that the best approximation to the experimental results with TEM images was the Brus equation. However, when the bandgap energy was close to the bulk bandgap energy, the theoretical models did not adjust correctly to the size measured from the TEM images. Full article
(This article belongs to the Special Issue Synthesis, Structure, and Properties of Inorganic Nanotubes)
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28 pages, 9959 KiB  
Article
Synthesis, Spectroscopic, and Antimicrobial Study of Binary and Ternary Ruthenium(III) Complexes of Ofloxacin Drug and Amino Acids as Secondary Ligands
by Ahmed M. Naglah, Mohamed A. Al-Omar, Abdulrahman A. Almehizia, Ahmad J. Obaidullah, Mashooq A. Bhat, Nasser S. Al-Shakliah, Kaouther Belgacem, Badriah M. Majrashi, Moamen S. Refat and Abdel Majid A. Adam
Crystals 2020, 10(3), 225; https://doi.org/10.3390/cryst10030225 - 20 Mar 2020
Cited by 7 | Viewed by 2911
Abstract
This article aimed to synthesis, spectroscopic, physicochemical characterizations, and catalytic studies on some ofloxacin (OFL) complexes with ruthenium(III) [Ru(III)] metal ions. The Ru(III)-OFL complex, [Ru(OFL)2(Cl)2]Cl and two mixed-ligand complexes, [Ru(OFL)(AA)(H2O)2]Cl2 derived from OFL as [...] Read more.
This article aimed to synthesis, spectroscopic, physicochemical characterizations, and catalytic studies on some ofloxacin (OFL) complexes with ruthenium(III) [Ru(III)] metal ions. The Ru(III)-OFL complex, [Ru(OFL)2(Cl)2]Cl and two mixed-ligand complexes, [Ru(OFL)(AA)(H2O)2]Cl2 derived from OFL as the primary ligand and amino acids [AA; either glycine (Gly) or alanine (Ala)] as the secondary ligands, were synthesized and characterized using microanalytical, spectroscopic, and physical techniques including element composition, molar conductivity, infrared, electronic spectra, thermal, X-ray powder diffraction (XRD), Energy dispersive X-ray spectroscopy (EDX), Scanning electron microscopy (SEM), and Transmittance electron microscopy (TEM) analyses. The element analysis data describe the formation of 1:2 [Ru(III):OFL] and 1:1:1 [Ru(III):OFL:AA] complexes. The octahedral geometry of the complexes was confirmed by their magnetic moment and diffused reflectance. Fourier Transform Infrared spectroscopic (FTIR) measurements suggested that the ligands chelated with Ru(III) ions through the nitrogen atoms of the piperazine ring. In vitro antibacterial efficiency of the OFL compounds was evaluated by paper disc diffusion method. Significant antimicrobial activities were observed for some compounds of the series. Full article
(This article belongs to the Section Biomolecular Crystals)
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24 pages, 7289 KiB  
Article
Raman Spectra of Diphenylalanine Microtubes: Polarisation and Temperature Effects
by Alexander Krylov, Svetlana Krylova, Svitlana Kopyl, Aleksandr Krylov, Ferid Salehli, Pavel Zelenovskiy, Alexander Vtyurin and Andrei Kholkin
Crystals 2020, 10(3), 224; https://doi.org/10.3390/cryst10030224 - 20 Mar 2020
Cited by 14 | Viewed by 3849
Abstract
Diphenylalanine microtubes have remarkable physical properties that allow one to use them in electronics. In this work, we measured polarised temperature-dependent Raman spectra in self-assembled diphenylalanine microtubes grown from the solution. We observed the anomalous temperature behaviour of the Raman lines. Their temperature [...] Read more.
Diphenylalanine microtubes have remarkable physical properties that allow one to use them in electronics. In this work, we measured polarised temperature-dependent Raman spectra in self-assembled diphenylalanine microtubes grown from the solution. We observed the anomalous temperature behaviour of the Raman lines. Their temperature changes were minimal, which required a significant improvement in the resolution and stability of Raman measurements. The anomalies in the behaviour of the spectra at about 178 K, 235 K, 255 K, 278 K, 296 K, 398 K and 412 K were observed. The structural phase transition at 398 K is irreversible. This transition is associated with the release of water molecules from nanochannels. The irreversible phase transition has a temperature range of about 10 K. Full article
(This article belongs to the Special Issue Raman Spectroscopy of Crystals)
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12 pages, 2139 KiB  
Article
Thermal and Photophysical Studies of Binary Mixtures of Liquid Crystal with Different Geometrical Mesogens
by Omaima A. Alhaddad, Hoda A. Ahmed, Mohamed Hagar, Gamal R. Saad, Khulood A. Abu Al-Ola and Magdi M. Naoum
Crystals 2020, 10(3), 223; https://doi.org/10.3390/cryst10030223 - 20 Mar 2020
Cited by 17 | Viewed by 2826
Abstract
Three binary systems were prepared by mixing of two different mesogenic derivatives, homologues, the first is azo/ester, namely 4-alkoxyphenylazo-4′-phenyl-4″-alkoxybenzoates (IIn+m) and the second is Schiff base/ester, namely 4-(arylideneamino)phenyl-4″-alkoxy benzoates (In+m). The two corresponding analogues from both series in the [...] Read more.
Three binary systems were prepared by mixing of two different mesogenic derivatives, homologues, the first is azo/ester, namely 4-alkoxyphenylazo-4′-phenyl-4″-alkoxybenzoates (IIn+m) and the second is Schiff base/ester, namely 4-(arylideneamino)phenyl-4″-alkoxy benzoates (In+m). The two corresponding analogues from both series in the binary mixtures investigated are of the same terminal alkoxy chain length. Mesomorphic properties were investigated by differential scanning calorimetry (DSC) and phases identified by polarized optical microscope (POM). Photophysical studies were investigated by UV spectroscopy connected to a hot stage. Results were discussed based on constructed binary phase diagrams. All mixtures were found to exhibit eutectic compositions, with linear or slightly linear nematic and smectic A stability/composition dependences. Geometrical parameters were predicted applying density functional theory (DFT) calculations. Twist angle (θ), aspect ratio, dipole moment and the polarizability of the individual compounds were discussed and correlated with the experimental results to illustrate the enhanced the mesophase stability and the mesophase range of the mixture at the eutectic composition compared with those of their individual components. Full article
(This article belongs to the Section Liquid Crystals)
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7 pages, 2702 KiB  
Article
Terbium-Tetracarboxylate Framework as a Luminescent Probe for the Selective Detection of Nitrofurazone
by Qipeng Li, Yanqiong Shen, Junsong Zhao, Zejun Zhang and Jinjie Qian
Crystals 2020, 10(3), 222; https://doi.org/10.3390/cryst10030222 - 20 Mar 2020
Cited by 1 | Viewed by 1954
Abstract
A novel terbium-tetracarboxylate framework with the 5,5’-(diazene-1,2-iyl)diisophthalic acid (H4abtc) ligand, formulated as [Tb(Habtc)(DMSO)(H2O)2]n (ZTU-5), has been synthesized and structurally characterized. ZTU-5 features a 2D-layered structure constructed by the binuclear terbium secondary building units (SBUs) [...] Read more.
A novel terbium-tetracarboxylate framework with the 5,5’-(diazene-1,2-iyl)diisophthalic acid (H4abtc) ligand, formulated as [Tb(Habtc)(DMSO)(H2O)2]n (ZTU-5), has been synthesized and structurally characterized. ZTU-5 features a 2D-layered structure constructed by the binuclear terbium secondary building units (SBUs) and abtc4– ligand, which can be further expanded into a 3D-supramolecular framework by the hydrogen bond interactions. In addition, the magnetic and fluorescence properties of ZTU-5 are investigated and ZTU-5 exhibits highly selective and sensitive detection of nitrofurazone (NZF). Full article
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25 pages, 10771 KiB  
Article
Modeling the Local Deformation and Transformation Behavior of Cast X8CrMnNi16-6-6 TRIP Steel and 10% Mg-PSZ Composite Using a Continuum Mechanics-Based Crystal Plasticity Model
by Faisal Qayyum, Sergey Guk, Matthias Schmidtchen, Rudolf Kawalla and Ulrich Prahl
Crystals 2020, 10(3), 221; https://doi.org/10.3390/cryst10030221 - 20 Mar 2020
Cited by 22 | Viewed by 4642
Abstract
A Transformation-Induced Plasticity (TRIP) steel matrix reinforced with magnesium-partially stabilized zirconia (Mg-PSZ) particles depicts a superior energy absorbing capacity during deformation. In this research, the TRIP/TWIP material model already developed in the framework of the Düsseldorf Advanced Material Simulation Kit (DAMASK) is tuned [...] Read more.
A Transformation-Induced Plasticity (TRIP) steel matrix reinforced with magnesium-partially stabilized zirconia (Mg-PSZ) particles depicts a superior energy absorbing capacity during deformation. In this research, the TRIP/TWIP material model already developed in the framework of the Düsseldorf Advanced Material Simulation Kit (DAMASK) is tuned for X8CrMnNi16-6-6 TRIP steel and 10% Mg-PSZ composite. A new method is explained to more accurately tune this material model by comparing the stress/strain, transformation, twinning, and dislocation glide obtained from simulations with respective experimental acoustic emission measurements. The optimized model with slight modification is assigned to the steel matrix in 10% Mg-PSZ composite material. In the simulation model, zirconia particles are assigned elastic properties with a perfect ceramic/matrix interface. Local deformation, transformation, and the twinning behavior of the steel matrix due to quasi-static tensile load were analyzed. The comparison of the simulation results with acoustic emission data shows good correlation and helps correlate acoustic events with physical attributes. The tuned material models are used to run full phase simulations using 2D Electron Backscatter Diffraction (EBSD) data from steel and 10% Mg-PSZ zirconia composites. Form these simulations, dislocation glide, martensitic transformation, stress evolution, and dislocation pinning in different stages of deformation are qualitatively discussed for the steel matrix and ceramic inclusions. Full article
(This article belongs to the Special Issue Crystal Plasticity)
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10 pages, 1895 KiB  
Article
Comparison of Material Properties of SCC Concrete with Steel Fibres Related to Ingress of Chlorides
by Petr Lehner, Petr Konečný and Tomasz Ponikiewski
Crystals 2020, 10(3), 220; https://doi.org/10.3390/cryst10030220 - 20 Mar 2020
Cited by 26 | Viewed by 3087
Abstract
The paper focuses on the evaluation of chloride ion diffusion coefficient of self-compacting concrete with steel fibre reinforcement. The reference concrete from Ordinary Portland Cement (OPC) and Self-Compacting Concrete (SCC) with several values of added steel fibres—0%, 1% and 2% of weight—were cast [...] Read more.
The paper focuses on the evaluation of chloride ion diffusion coefficient of self-compacting concrete with steel fibre reinforcement. The reference concrete from Ordinary Portland Cement (OPC) and Self-Compacting Concrete (SCC) with several values of added steel fibres—0%, 1% and 2% of weight—were cast in order to investigate the effect of fibres. The three procedures of diffusion coefficient calculation are presented—rapid chloride penetration test, accelerated penetration tests with chloride as well as the surface measurement of electrical resistivity using Wenner probe. The resulting diffusion coefficients obtained by all methods are compared and evaluated regarding the basic mechanical properties of concrete mixtures. Full article
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9 pages, 2105 KiB  
Article
Simple Synthesis of NdFeO3 Nanoparticles By the Co-Precipitation Method Based on a Study of Thermal Behaviors of Fe (III) and Nd (III) Hydroxides
by Tien A. Nguyen, V. Pham, Thanh L. Pham, Linh T. Tr. Nguyen, I. Ya. Mittova, V. O. Mittova, Lan N. Vo, Bich Tram T. Nguyen, Vuong X. Bui and E. L. Viryutina
Crystals 2020, 10(3), 219; https://doi.org/10.3390/cryst10030219 - 20 Mar 2020
Cited by 39 | Viewed by 4736
Abstract
In this study, a nanostructured NdFeO3 material was synthesized via a simple process of the hydrolysis of Nd (III) and Fe (III) cations in hot water with 5% NaOH as a precipitating agent. According to the results of the thermal behaviors of [...] Read more.
In this study, a nanostructured NdFeO3 material was synthesized via a simple process of the hydrolysis of Nd (III) and Fe (III) cations in hot water with 5% NaOH as a precipitating agent. According to the results of the thermal behaviors of each hydroxide, either containing Fe (III) or Nd (III), the perovskite type of neodymium orthoferrite NdFeO3 was simply synthesized by annealing a mixture of Fe (III) and Nd (III) hydroxides at 750 °C. The nanostructured NdFeO3 was obtained in spherical granules with diameters of around 30 nm. The magnetic properties of the material were a coercive force (Hc) of 136.76 Oe, a remanent magnetization (Mr) of 0.68 emu·g–1, and a saturation magnetization (Ms) of 0.79 emu·g–1. Full article
(This article belongs to the Special Issue Magnetism in Low Dimensional Structures)
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11 pages, 7981 KiB  
Article
Pulsed Electrodeposition for Copper Nanowires
by Duc-Thinh Vuong, Ha-My Hoang, Nguyen-Hung Tran and Hyun-Chul Kim
Crystals 2020, 10(3), 218; https://doi.org/10.3390/cryst10030218 - 20 Mar 2020
Cited by 5 | Viewed by 3383
Abstract
Copper nanowires (Cu NWs) are a promising alternative to indium tin oxide (ITO), for use as transparent conductors that exhibit comparable performance at a lower cost. Furthermore, Cu NWs are flexible, a property not possessed by ITO. However, the Cu NW-based transparent electrode [...] Read more.
Copper nanowires (Cu NWs) are a promising alternative to indium tin oxide (ITO), for use as transparent conductors that exhibit comparable performance at a lower cost. Furthermore, Cu NWs are flexible, a property not possessed by ITO. However, the Cu NW-based transparent electrode has a reddish color and tends to deteriorate in ambient conditions due to the oxidation of Cu. In this paper, we propose a pulsed-current (PC) plating method to deposit nickel onto the Cu NWs in order to reduce oxidation over a 30-day period, and to minimize the sheet resistance. Additionally, the effects of the pulse current, duty cycle, and pulse frequency on the performance of the Cu–Ni (copper–nickel) NW films have also been investigated. As a result, the reddish color of the electrode was eliminated, as oxidation was completely suppressed, and the sheet resistance was reduced from 35 Ω/sq to 27 Ω/sq. However, the transmittance decreased slightly from 86% to 76% at a wavelength of 550 nm. The Cu–Ni NW electrodes also exhibited excellent long-term cycling stability after 6000 bending cycles. Our fabricated Cu–Ni electrodes were successfully applied in flexible polymer-dispersed liquid crystal smart windows. Full article
(This article belongs to the Special Issue Organic Optoelectronic Materials)
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12 pages, 667 KiB  
Review
Involvement of Deep Eutectic Solvents in Extraction by Molecularly Imprinted Polymers—A Minireview
by Michal Jablonský, Veronika Majová, Jozef Šima, Katarína Hroboňová and Anna Lomenová
Crystals 2020, 10(3), 217; https://doi.org/10.3390/cryst10030217 - 19 Mar 2020
Cited by 12 | Viewed by 4347
Abstract
Substantial research activity has been focused on new modes of extraction and refining processes during the last decades. In this field, coverage of the recovery of bioactive compounds and the role of green solvents such as deep eutectic solvents (DESs) also gradually increases. [...] Read more.
Substantial research activity has been focused on new modes of extraction and refining processes during the last decades. In this field, coverage of the recovery of bioactive compounds and the role of green solvents such as deep eutectic solvents (DESs) also gradually increases. A specific field of DESs involvement is represented by molecularly imprinted polymers (MIPs). The current state and prospects of implementing DESs in MIPs chemistry are, based on the accumulated experimental data so far, evaluated and discussed in this minireview. Full article
(This article belongs to the Special Issue Eutectic Solvents)
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7 pages, 1762 KiB  
Article
Microstructure and Mechanical Properties of Platinum Fiber Fabricated by Unidirectional Solidification
by Yuui Yokota, Takayuki Nihei, Masao Yoshino, Akihiro Yamaji, Satoshi Toyoda, Hiroki Sato, Yuji Ohashi, Shunsuke Kurosawa, Kei Kamada and Akira Yoshikawa
Crystals 2020, 10(3), 216; https://doi.org/10.3390/cryst10030216 - 19 Mar 2020
Cited by 3 | Viewed by 2842
Abstract
The microstructure and mechanical properties of platinum (Pt) fibers fabricated by unidirectional solidification using the alloy-micro-pulling-down (A-μ-PD) method were investigated using a Universal Testing Machine and Electron Backscattered Diffraction (EBSD). The Pt fiber fabricated at a growth rate of 10 mm/min was composed [...] Read more.
The microstructure and mechanical properties of platinum (Pt) fibers fabricated by unidirectional solidification using the alloy-micro-pulling-down (A-μ-PD) method were investigated using a Universal Testing Machine and Electron Backscattered Diffraction (EBSD). The Pt fiber fabricated at a growth rate of 10 mm/min was composed of relatively large grains with <100> crystal orientation along the growth direction. The crystal orientation was consistent with the easy axis of the crystal growth on the face-centered-cubic (f.c.c.) structure. On the other hand, the adjacent grains of the Pt fiber fabricated at 50 mm/min were randomly oriented owing to a faster growth rate. In tensile tests, the Pt fibers fabricated by the A-μ-PD method indicated extremely different stress–strain curves compared to the commercial Pt wire. The maximum tensile stress of the Pt fiber reached ~100 MPa, and the Pt fiber ruptured after 58% nominal strain. Full article
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27 pages, 1413 KiB  
Review
Towards an Optimal Sample Delivery Method for Serial Crystallography at XFEL
by Robert KY Cheng
Crystals 2020, 10(3), 215; https://doi.org/10.3390/cryst10030215 - 19 Mar 2020
Cited by 39 | Viewed by 6255
Abstract
The advent of the X-ray free electron laser (XFEL) in the last decade created the discipline of serial crystallography but also the challenge of how crystal samples are delivered to X-ray. Early sample delivery methods demonstrated the proof-of-concept for serial crystallography and XFEL [...] Read more.
The advent of the X-ray free electron laser (XFEL) in the last decade created the discipline of serial crystallography but also the challenge of how crystal samples are delivered to X-ray. Early sample delivery methods demonstrated the proof-of-concept for serial crystallography and XFEL but were beset with challenges of high sample consumption, jet clogging and low data collection efficiency. The potential of XFEL and serial crystallography as the next frontier of structural solution by X-ray for small and weakly diffracting crystals and provision of ultra-fast time-resolved structural data spawned a huge amount of scientific interest and innovation. To utilize the full potential of XFEL and broaden its applicability to a larger variety of biological samples, researchers are challenged to develop better sample delivery methods. Thus, sample delivery is one of the key areas of research and development in the serial crystallography scientific community. Sample delivery currently falls into three main systems: jet-based methods, fixed-target chips, and drop-on-demand. Huge strides have since been made in reducing sample consumption and improving data collection efficiency, thus enabling the use of XFEL for many biological systems to provide high-resolution, radiation damage-free structural data as well as time-resolved dynamics studies. This review summarizes the current main strategies in sample delivery and their respective pros and cons, as well as some future direction. Full article
(This article belongs to the Special Issue Macromolecular Serial Crystallography)
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12 pages, 4463 KiB  
Article
Controlled Synthesis of Magnetic Iron Oxide Nanoparticles: Magnetite or Maghemite?
by Sebastian P. Schwaminger, Christopher Syhr and Sonja Berensmeier
Crystals 2020, 10(3), 214; https://doi.org/10.3390/cryst10030214 - 19 Mar 2020
Cited by 71 | Viewed by 8293
Abstract
Today, magnetic nanoparticles are present in multiple medical and industrial applications. We take a closer look at the synthesis of magnetic iron oxide nanoparticles through the co-precipitation of iron salts in an alkaline environment. The variation of the synthesis parameters (ion concentration, temperature, [...] Read more.
Today, magnetic nanoparticles are present in multiple medical and industrial applications. We take a closer look at the synthesis of magnetic iron oxide nanoparticles through the co-precipitation of iron salts in an alkaline environment. The variation of the synthesis parameters (ion concentration, temperature, stirring rate, reaction time and dosing rate) change the structure and diameter of the nanoparticles. Magnetic iron oxide nanoparticles are characterized by X-ray diffraction (XRD), Raman spectroscopy and transmission electron microscopy (TEM). Magnetic nanoparticles ranging from 5 to 16 nm in diameter were synthesized and their chemical structure was identified. Due to the evaluation of Raman spectra, TEM and XRD, the magnetite and maghemite nanoparticles can be observed and the proportion of phases and the particle size can be related to the synthesis conditions. We want to highlight the use of Raman active modes A1g of spinel structured iron oxides to determine the content of magnetite and maghemite in our samples. Magnetite nanoparticles can be derived from highly alkaline conditions even without establishing an inert atmosphere during the synthesis. The correlation between the particle properties and the various parameters of the synthesis was modelled with linear mixture models. The two models can predict the particle size and the oxidation state of the synthesized nanoparticles, respectively. The modeling of synthesis parameters not only helps to improve synthesis conditions for iron oxide nanoparticles but to understand crystallization of nanomaterials. Full article
(This article belongs to the Special Issue Synthesis, Structure, and Properties of Inorganic Nanotubes)
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15 pages, 3337 KiB  
Article
Mixed Oscillation Flow of Binary Fluid with Minus One Capillary Ratio in the Czochralski Crystal Growth Model
by Chunmei Wu, Jinhui Chen and Yourong Li
Crystals 2020, 10(3), 213; https://doi.org/10.3390/cryst10030213 - 19 Mar 2020
Cited by 2 | Viewed by 2106
Abstract
This work presented a series of three-dimensional unsteady numerical simulations on the characteristics of the mixed oscillation flows of binary mixture in a Czochralski crystal growth model. The silicon-germanium melt is investigated and the capillary ratio is minus one. The simulation results showed [...] Read more.
This work presented a series of three-dimensional unsteady numerical simulations on the characteristics of the mixed oscillation flows of binary mixture in a Czochralski crystal growth model. The silicon-germanium melt is investigated and the capillary ratio is minus one. The simulation results showed that, for the special capillary ratio, the thermal and solutocapillary forces are imposed in opposite directions and counteract each other. With the effect of buoyancy, the balance between the capillary forces is disturbed. Mixed with the forced convection driven by rotation, the capillary-buoyancy convection is complex. The basic mixed flow streamlines are presented as various rolling cells. The directions of the rolls are dependent on the combinations of surface and body forces. With the increase of temperature gradient, the basic flow stability is broken, and the oscillations occur. The crucible rotation has an effective influence on the stability enhancement. However, affected by the crystal rotation, the critical condition experiences an increase to a turning point, and then undergoes a sharp reduction to zero. Once the instability is incubated, the surface oscillations are analyzed. For the three-dimensional steady flow, only spatial oscillations are observed circumferentially, and the surface patterns of spokes, rosebud, and pulsating ring are obtained. For the unsteady oscillation flow, the spiral hydrosoultal waves, rotating waves, and superimposition of spirals and spokes are observed, and the oscillation behaviors are also discussed. Full article
(This article belongs to the Section Crystal Engineering)
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19 pages, 8357 KiB  
Review
Mechanisms-Based Transitional Viscoplasticity
by Aleksander Zubelewicz
Crystals 2020, 10(3), 212; https://doi.org/10.3390/cryst10030212 - 18 Mar 2020
Cited by 6 | Viewed by 3027
Abstract
When metal is subjected to extreme strain rates, the conversation of energy to plastic power, the subsequent heat production and the growth of damages may lag behind the rate of loading. The imbalance alters deformation pathways and activates micro-dynamic excitations. The excitations immobilize [...] Read more.
When metal is subjected to extreme strain rates, the conversation of energy to plastic power, the subsequent heat production and the growth of damages may lag behind the rate of loading. The imbalance alters deformation pathways and activates micro-dynamic excitations. The excitations immobilize dislocation, are responsible for the stress upturn and magnify plasticity-induced heating. The main conclusion of this study is that dynamic strengthening, plasticity-induced heating, grain size strengthening and the processes of microstructural relaxation are inseparable phenomena. Here, the phenomena are discussed in semi-independent sections, and then, are assembled into a unified constitutive model. The model is first tested under simple loading conditions and, later, is validated in a numerical analysis of the plate impact problem, where a copper flyer strikes a copper target with a velocity of 308 m/s. It should be stated that the simulations are performed with the use of the deformable discrete element method, which is designed for monitoring translations and rotations of deformable particles. Full article
(This article belongs to the Special Issue Crystal Plasticity)
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18 pages, 3304 KiB  
Article
Pharmaceutical Cocrystal Development of TAK-020 with Enhanced Oral Absorption
by Kouya Kimoto, Mitsuo Yamamoto, Masatoshi Karashima, Miyuki Hohokabe, Junpei Takeda, Katsuhiko Yamamoto and Yukihiro Ikeda
Crystals 2020, 10(3), 211; https://doi.org/10.3390/cryst10030211 - 18 Mar 2020
Cited by 24 | Viewed by 5115
Abstract
The objective of this study was to improve the solubility of poorly water-soluble drugs by pharmaceutical cocrystal engineering techniques and select the best pharmaceutical forms with high solubility and solubilized formulations for progress from the early discovery stage toward the clinical stage. Several [...] Read more.
The objective of this study was to improve the solubility of poorly water-soluble drugs by pharmaceutical cocrystal engineering techniques and select the best pharmaceutical forms with high solubility and solubilized formulations for progress from the early discovery stage toward the clinical stage. Several pharmaceutical cocrystals of TAK-020, a Bruton tyrosine kinase inhibitor, were newly discovered in the screening based on the solid grinding method and the slurry method, considering thermodynamic factors that dominate cocrystal formation. TAK-020/gentisic acid cocrystal (TAK-020/GA CC) was selected based on a physicochemical property of enhanced dissolution rate. TAK-020/GA CC was proven to be a reliable cocrystal formation with a definitive stoichiometric ratio by a variety of analytical techniques—pKa calculation, solid-state nuclear magnetic resonance, and single X-ray structure analysis from the view of regulation. Furthermore, its absorption was remarkable and beyond those achieved in currently existing solubilized formulation techniques, such as nanocrystal, amorphous solid dispersion, and lipid-based formulation, in dog pharmacokinetic studies. TAK-020/GA CC was the best drug form, which might lead to good pharmacological effects with regard to enhanced absorption and development by physicochemical characterization. Through the trials of solid-state optimization from early drug discovery to pharmaceutical drug development, the cocrystals can be an effective option for achieving solubilization applicable in the pharmaceutical industry. Full article
(This article belongs to the Special Issue Pharmaceutical Crystals and Its Application)
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11 pages, 4017 KiB  
Article
Combustion Synthesis of NbB2–Spinel MgAl2O4 Composites from MgO-Added Thermite-Based Reactants with Excess Boron
by Chun-Liang Yeh and Yin-Chien Chen
Crystals 2020, 10(3), 210; https://doi.org/10.3390/cryst10030210 - 18 Mar 2020
Cited by 14 | Viewed by 2484
Abstract
The formation of NbB2–MgAl2O4 composites from the MgO-added thermite-based reaction systems was investigated by self-propagating high-temperature synthesis (SHS). Two thermite mixtures, Nb2O5/B2O3/Al and Nb2O5/Al, were, respectively, [...] Read more.
The formation of NbB2–MgAl2O4 composites from the MgO-added thermite-based reaction systems was investigated by self-propagating high-temperature synthesis (SHS). Two thermite mixtures, Nb2O5/B2O3/Al and Nb2O5/Al, were, respectively, adopted in Reactions (1) and (2). The XRD analysis confirmed the combination of Al2O3 with MgO to form MgAl2O4 during the SHS process and that excess boron of 30 atom.% was required to yield NbB2–MgAl2O4 composites with negligible NbB and Nb3B4. The microstructure of the composite reveals that rod-shaped MgAl2O4 crystals are closely interlocked and granular NbB2 are embedded in or scattered over MgAl2O4. With the addition of MgAl2O4, the fracture toughness (KIC) of 4.37–4.82 MPa m1/2 was obtained for the composites. The activation energies Ea = 219.5 ± 16 and 167.9 ± 13 kJ/mol for Reactions (1) and (2) were determined from combustion wave kinetics. Full article
(This article belongs to the Section Inorganic Crystalline Materials)
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9 pages, 1932 KiB  
Article
Determination and Data Correlation of Solubility of Sofosbuvir Polymorphs in Ethyl Acetate + Toluene and Methyl tert-Butyl Ether Binary Solvents at the Temperature Range from 268.15 to 308.15 K
by Wei-Jie Ji, En-Fu Wang and Ming-Hui Qi
Crystals 2020, 10(3), 209; https://doi.org/10.3390/cryst10030209 - 17 Mar 2020
Cited by 1 | Viewed by 3077
Abstract
A gravimetric method was used to experimentally determine the (solid + liquid) equilibrium of sofosbuvir of crystalline forms A and B in both ethyl acetate + toluene and methyl tert-butyl ether (MTBE) + toluene binary solvents systems at atmosphere pressure. Experiments were [...] Read more.
A gravimetric method was used to experimentally determine the (solid + liquid) equilibrium of sofosbuvir of crystalline forms A and B in both ethyl acetate + toluene and methyl tert-butyl ether (MTBE) + toluene binary solvents systems at atmosphere pressure. Experiments were carried out at a temperature range of 268.15−308.15 K. Results show that the solubility of sofosbuvir increases with temperature, and the solubility of form B was higher than that of form A. The modified Apelblat model, the CNIBS/Redlich–Kister model, and the combined version of Jouyban–Acree model were employed to correlate the measured solubility data, respectively. Furthermore, an examination of the solid-state stability of the two polymorphs was conducted, finding that form A and form B exhibit good solid-state stability under high temperature, high humidity, and strong light exposure conditions. Full article
(This article belongs to the Special Issue Polymorphism in Crystal)
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53 pages, 5428 KiB  
Review
Luminescence Spectroscopy and Origin of Luminescence Centers in Bi-Doped Materials
by Aleksei Krasnikov, Eva Mihokova, Martin Nikl, Svetlana Zazubovich and Yaroslav Zhydachevskyy
Crystals 2020, 10(3), 208; https://doi.org/10.3390/cryst10030208 - 17 Mar 2020
Cited by 54 | Viewed by 5479
Abstract
Bi-doped compounds recently became the subject of an extensive research due to their possible applications as scintillator and phosphor materials. The oxides co-doped with Bi3+ and trivalent rare-earth ions were proposed as prospective phosphors for white light-emitting diodes and quantum cutting down-converting [...] Read more.
Bi-doped compounds recently became the subject of an extensive research due to their possible applications as scintillator and phosphor materials. The oxides co-doped with Bi3+ and trivalent rare-earth ions were proposed as prospective phosphors for white light-emitting diodes and quantum cutting down-converting materials applicable for enhancement of silicon solar cells. Luminescence characteristics of different Bi3+-doped materials were found to be strongly different and ascribed to electronic transitions from the excited levels of a Bi3+ ion to its ground state, charge-transfer transitions, Bi3+ dimers or clusters, radiative decay of Bi3+-related localized or trapped excitons, etc. In this review, we compare the characteristics of the Bi3+-related luminescence in various compounds; discuss the possible origin of the corresponding luminescence centers as well as the processes resulting in their luminescence; consider the phenomenological models proposed to describe the excited-state dynamics of the Bi3+-related centers and determine the structure and parameters of their relaxed excited states; address an influence of different interactions (e.g., spin-orbit, electron-phonon, hyperfine) as well as the Bi3+ ion charge and volume compensating defects on the luminescence characteristics. The Bi-related luminescence arising from lower charge states (namely, Bi2+, Bi+, Bi0) is also reviewed. Full article
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11 pages, 3435 KiB  
Article
Microstructure and Properties of Bulk Ultrafine-Grained Cu1.5Cr0.1Si Alloy through ECAP by Route C and Aging Treatment
by Tingbiao Guo, Xiaoyang Tai, Shiru Wei, Junjie Wang, Zhi Jia and Yutian Ding
Crystals 2020, 10(3), 207; https://doi.org/10.3390/cryst10030207 - 16 Mar 2020
Cited by 2 | Viewed by 2152
Abstract
The evolutions of the microstructure and its effect on the mechanical and electrical conductivity properties of Cu1.5Cr0.1Si alloy after equal channel angle pressing (ECAP)-C path deformation and aging treatment have been investigated using scanning electron microscopy (SEM), x-ray diffraction (XRD), and electron back-scattered [...] Read more.
The evolutions of the microstructure and its effect on the mechanical and electrical conductivity properties of Cu1.5Cr0.1Si alloy after equal channel angle pressing (ECAP)-C path deformation and aging treatment have been investigated using scanning electron microscopy (SEM), x-ray diffraction (XRD), and electron back-scattered diffraction (EBSD). It was found that after the ECAP-C deformation at room temperature, with an extension of aging time, the strong (111) macro orientation formed in the Cu1.5Cr0.1Si alloy. The ultrafine crystals formed by ECAP and the rich chromium phase precipitated along grain boundaries during the aging process greatly improved the material strength. After aging at 350 °C for 4 h, the tensile strength, elongation, and conductivity reached 528 MPa, 15.27%, and 78.9% IACS, respectively. The fracture mode of the alloy was ductile fracture. The steady-oriented {111} <110> texture was beneficial to improving the conductivity of the material. Full article
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