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Crystals
Volume 10
Issue 4
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Crystals, Volume 10, Issue 4 (April 2020) – 102 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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13 pages, 4130 KiB  
Article
Influence of Combined Action of Steel Fiber and MgO on Chloride Diffusion Resistance of Concrete
by Feifei Jiang, Min Deng, Liwu Mo and Wenqing Wu
Crystals 2020, 10(4), 338; https://doi.org/10.3390/cryst10040338 - 24 Apr 2020
Cited by 2 | Viewed by 1992
Abstract
To improve the chloride diffusion resistance and durability of concrete, a new kind of steel fiber reinforced MgO concrete (SFRMC) was made by adding steel fiber and MgO to concrete simultaneously. With steel fiber for load bearing and expansion limiting, MgO as the [...] Read more.
To improve the chloride diffusion resistance and durability of concrete, a new kind of steel fiber reinforced MgO concrete (SFRMC) was made by adding steel fiber and MgO to concrete simultaneously. With steel fiber for load bearing and expansion limiting, MgO as the expander, SFRMC has both the advantages of fiber reinforced concrete and expansion concrete. The influence of steel fiber and MgO on the strength and chloride diffusion resistance of concrete was evaluated by splitting tensile test and chloride diffusion test. Mercury intrusion porosimeter (MIP) and scanning electron microscopy (SEM) were used to study the microstructure of SFRMC. The results showed that the combined action of steel fiber and MgO reduced the porosity of concrete and the chloride diffusion coefficient (CDC), which could not be achieved by steel fiber and MgO separately. In the free state, the expansion energy produced by the hydration of MgO made the concrete expand outwards. However, under the constraint of steel fiber, the expansion energy was used to tension the fiber, resulting in self-stress. In this way, compared to reference concrete RC, the tensile strength of SFRMC-1, SFRMC-2, and SFRMC-3 increased by 3.1%, 61.3%, and 64.5%, CDC decreased by 8.8%, 36.7%, and 33.1%, and the porosity decreased by 6.2%, 18.4%, and 20.6%, respectively. In addition, the SEM observations demonstrated that the interfacial transition zone (ITZ) between fiber and matrix was denser in SFRMC, which contributed to reduce the diffusion of chloride ions in the concrete. Full article
(This article belongs to the Special Issue Cement-Based Composites: Advancements in Development and Characterization)
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14 pages, 2763 KiB  
Article
Analytical Modeling of Residual Stress in Laser Powder Bed Fusion Considering Part’s Boundary Condition
by Elham Mirkoohi, Hong-Chuong Tran, Yu-Lung Lo, You-Cheng Chang, Hung-Yu Lin and Steven Y. Liang
Crystals 2020, 10(4), 337; https://doi.org/10.3390/cryst10040337 - 24 Apr 2020
Cited by 22 | Viewed by 3433
Abstract
Rapid and accurate prediction of residual stress in metal additive manufacturing processes is of great importance to guarantee the quality of the fabricated part to be used in a mission-critical application in the aerospace, automotive, and medical industries. Experimentations and numerical modeling of [...] Read more.
Rapid and accurate prediction of residual stress in metal additive manufacturing processes is of great importance to guarantee the quality of the fabricated part to be used in a mission-critical application in the aerospace, automotive, and medical industries. Experimentations and numerical modeling of residual stress however are valuable but expensive and time-consuming. Thus, a fully coupled thermomechanical analytical model is proposed to predict residual stress of the additively manufactured parts rapidly and accurately. A moving point heat source approach is used to predict the temperature field by considering the effects of scan strategies, heat loss at part’s boundaries, and energy needed for solid-state phase transformation. Due to the high-temperature gradient in this process, the part experiences a high amount of thermal stress which may exceed the yield strength of the material. The thermal stress is obtained using Green’s function of stresses due to the point body load. The Johnson–Cook flow stress model is used to predict the yield surface of the part under repeated heating and cooling. As a result of the cyclic heating and cooling and the fact that the material is yielded, the residual stress build-up is precited using incremental plasticity and kinematic hardening behavior of the metal according to the property of volume invariance in plastic deformation in coupling with the equilibrium and compatibility conditions. Experimental measurement of residual stress was conducted using X-ray diffraction on the fabricated IN718 built via laser powder bed fusion to validate the proposed model. Full article
(This article belongs to the Special Issue Additive Manufacturing (AM) of Metallic Alloys)
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14 pages, 2659 KiB  
Article
Microstructure, Texture, and Strength Development during High-Pressure Torsion of CrMnFeCoNi High-Entropy Alloy
by Werner Skrotzki, Aurimas Pukenas, Eva Odor, Bertalan Joni, Tamas Ungar, Bernhard Völker, Anton Hohenwarter, Reinhard Pippan and Easo P. George
Crystals 2020, 10(4), 336; https://doi.org/10.3390/cryst10040336 - 24 Apr 2020
Cited by 40 | Viewed by 3593
Abstract
The equiatomic face-centered cubic high-entropy alloy CrMnFeCoNi was severely deformed at room and liquid nitrogen temperature by high-pressure torsion up to shear strains of about 170. Its microstructure was analyzed by X-ray line profile analysis and transmission electron microscopy and its texture by [...] Read more.
The equiatomic face-centered cubic high-entropy alloy CrMnFeCoNi was severely deformed at room and liquid nitrogen temperature by high-pressure torsion up to shear strains of about 170. Its microstructure was analyzed by X-ray line profile analysis and transmission electron microscopy and its texture by X-ray microdiffraction. Microhardness measurements, after severe plastic deformation, were done at room temperature. It is shown that at a shear strain of about 20, a steady state grain size of 24 nm, and a dislocation density of the order of 1016 m−2 is reached. The dislocations are mainly screw-type with low dipole character. Mechanical twinning at room temperature is replaced by a martensitic phase transformation at 77 K. The texture developed at room temperature is typical for sheared face-centered cubic nanocrystalline metals, but it is extremely weak and becomes almost random after high-pressure torsion at 77 K. The strength of the nanocrystalline material produced by high-pressure torsion at 77 K is lower than that produced at room temperature. The results are discussed in terms of different mechanisms of deformation, including dislocation generation and propagation, twinning, grain boundary sliding, and phase transformation. Full article
(This article belongs to the Special Issue Crystal Plasticity)
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16 pages, 5337 KiB  
Article
Synergetic Effect of Calcium Doping on Catalytic Activity of Manganese Ferrite: DFT Study and Oxidation of Hydrocarbon
by Zahoor Iqbal, Saima Sadiq, Muhammad Sadiq, Muhammad Ali, Khalid Saeed, Najeeb Ur Rehman, Mohammad Ilyas, Saif Ullah, Saeed Ullah Jan, Iftikhar Ahmad and Mian Hussain Shah
Crystals 2020, 10(4), 335; https://doi.org/10.3390/cryst10040335 - 23 Apr 2020
Cited by 3 | Viewed by 2990
Abstract
Manganese ferrite (MnFe2O4) and calcium-doped manganese ferrite (Ca-MnFe2O4) were synthesized, characterized, and tested for oxidation of hydrocarbons (CH) in a self-designed gas blow rotating (GBR) reactor. The uniformly sized and thermally stable MnFe2O [...] Read more.
Manganese ferrite (MnFe2O4) and calcium-doped manganese ferrite (Ca-MnFe2O4) were synthesized, characterized, and tested for oxidation of hydrocarbons (CH) in a self-designed gas blow rotating (GBR) reactor. The uniformly sized and thermally stable MnFe2O4 nanoparticles (molar ratio, 1/284.5) showed a reasonable catalytic activity (productivity: 366.17 mmolg−1h−1) with 60% selectivity at 80 °C, which was further enhanced by calcium doping (productivity: 379.38 mmolg−1h−1). The suspicious behavior of Ca-MnFe2O4 was disclosed experimentally and theoretically as well. Full article
(This article belongs to the Section Inorganic Crystalline Materials)
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14 pages, 4204 KiB  
Article
Crystal Structure and Supramolecular Architecture of Inorganic Ligand-Coordinated Salen-Type Schiff Base Complex: Insights into Halogen Bond from Theoretical Analysis and 3D Energy Framework Calculations
by Qiong Wu, Jian-Chang Xiao, Cun Zhou, Jin-Rong Sun, Mei-Fen Huang, Xindi Xu, Tianyu Li and Hui Tian
Crystals 2020, 10(4), 334; https://doi.org/10.3390/cryst10040334 - 23 Apr 2020
Cited by 22 | Viewed by 3747
Abstract
To identify the effects of halogen bonding in the architecture of Schiff base complex supramolecular networks, we introduced halogenated Schiff-base 3-Br-5-Cl-salen as ligand and isolated a new salen-type manganese(III) complex [MnIII(Cl)(H2O)(3-Br-5-Cl-salen)] (1) where 3-Br-5-Cl-salen = [...] Read more.
To identify the effects of halogen bonding in the architecture of Schiff base complex supramolecular networks, we introduced halogenated Schiff-base 3-Br-5-Cl-salen as ligand and isolated a new salen-type manganese(III) complex [MnIII(Cl)(H2O)(3-Br-5-Cl-salen)] (1) where 3-Br-5-Cl-salen = N,N’-bis(3-bromo-5-chlorosalicylidene)-1,2-diamine. The complex was investigated in the solid-state for halogen bonds (XBs) by single crystal X-ray structure analysis. Meanwhile, theoretical calculations were carried out to rationalize the formation mechanism of different types of XBs in the complex. The analysis result of electronic structure of the halogen bonds indicated that the chlorine atom coordinated to the Mn(III) center possesses the most negative potential and acts as anionic XB acceptor (electron donor) to the adjacent substituted halogens on the ligand, meanwhile the intermolecular Mn-Cl···X-C halogen bonding plays a significant role in directing the packing arrangement of adjacent molecules and linking the 2D layers into a 3D network. In order to verify the above results and acquire detailed information, the title complex was further analyzed by using the Hirshfeld surface analyses. Full article
(This article belongs to the Special Issue Advanced Research in Halogen Bonding)
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11 pages, 2719 KiB  
Article
Effects of Various Inhibitors on the Nucleation of Calcium Oxalate in Synthetic Urine
by Yu-Chao Hsu, Yi-Hsuan Lin and Lie-Ding Shiau
Crystals 2020, 10(4), 333; https://doi.org/10.3390/cryst10040333 - 23 Apr 2020
Cited by 11 | Viewed by 4650
Abstract
A new synthetic urine was adopted in this work to study the nucleation kinetics of calcium oxalate using a batch crystallizer for various supersaturations at 37 °C. In the studied new synthetic urine, three additional components (urea, uric acid and creatinine) within the [...] Read more.
A new synthetic urine was adopted in this work to study the nucleation kinetics of calcium oxalate using a batch crystallizer for various supersaturations at 37 °C. In the studied new synthetic urine, three additional components (urea, uric acid and creatinine) within the normal physiological ranges were added to the commonly-used synthetic urine to simulate human urine more closely. The interfacial energy for the nucleation of calcium oxalate was determined based on classical nucleation theory using the turbidity induction time measurements. The effects of various inhibitors, including magnesium, citrate, hydroxycitrate, chondroitin sulfate, and phytate, on the nucleation of calcium oxalate were investigated in detail. Scanning electron microscopy was used to examine the influences of these inhibitors on the preferential nucleation of the different hydrates of calcium oxalate crystals. Full article
(This article belongs to the Special Issue Crystal Nucleation and Growth Kinetics)
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14 pages, 5911 KiB  
Article
Regulating Mechanical Properties of Al/SiC by Utilizing Different Ball Milling Speeds
by Saud M. Almotairy, Nabeel H. Alharthi and Hany S. Abdo
Crystals 2020, 10(4), 332; https://doi.org/10.3390/cryst10040332 - 23 Apr 2020
Cited by 9 | Viewed by 3439
Abstract
Advanced materials with high strength are in great demand for structural applications, such as in aerospace. It has been proved that fabrication strategy plays a vital role in producing composites to satisfy these needs. This study explores new strategies for flake powder metallurgy, [...] Read more.
Advanced materials with high strength are in great demand for structural applications, such as in aerospace. It has been proved that fabrication strategy plays a vital role in producing composites to satisfy these needs. This study explores new strategies for flake powder metallurgy, with the aim of designing an effective strategy to achieve the highest possible mechanical strength for a metal matrix nanocomposite without changing the reinforcement fraction. Different strategies were used to regulate the mechanical properties for similar composites based on shift speed ball milling. Ultra-ductile composites on one hand, and ultra-strong composites on the other hand, were fabricated using similar composites. The results demonstrate that shifting the ball milling speed can be used to manipulate the mechanical properties of the composite to achieve the desired properties for any specific application. Full article
(This article belongs to the Section Crystalline Materials)
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11 pages, 26567 KiB  
Article
Fabrication of CoFe2O4 Nanowire Using a Double-Pass Porous Alumina Template with a Large Range of Pore Diameters
by Wei Chen, Hui Zheng, Dongping Hu, Qiong Wu, Peng Zheng, Liang Zheng and Yang Zhang
Crystals 2020, 10(4), 331; https://doi.org/10.3390/cryst10040331 - 23 Apr 2020
Cited by 3 | Viewed by 3148
Abstract
In this work, CoFe2O4 nanowire was fabricated by using a self-designed double-pass porous alumina template. The double-pass porous alumina template was prepared by a two-step oxidation method using a mixed acid (phosphoric acid and oxalic acid) electrolyte and polymethyl methacrylate [...] Read more.
In this work, CoFe2O4 nanowire was fabricated by using a self-designed double-pass porous alumina template. The double-pass porous alumina template was prepared by a two-step oxidation method using a mixed acid (phosphoric acid and oxalic acid) electrolyte and polymethyl methacrylate (PMMA) filler. The combustion of aluminum foil at a high voltage has been effectively resolved by using this mixed acid electrolyte. Additionally, the range of pore diameters has been obviously increased to 230–400 nm by using PMMA as the filler, which can prevent contact between the pore and solution when removing the barrier layer. Subsequently, CoFe2O4 ferrite nanowire arrays were successfully fabricated into the double-pass porous alumina template by an electrochemical deposition method, and show an anisotropic feature of magnetic properties. Full article
(This article belongs to the Special Issue Magnetism in Low Dimensional Structures)
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19 pages, 4184 KiB  
Article
Nano-Ridge Engineering of GaSb for the Integration of InAs/GaSb Heterostructures on 300 mm (001) Si
by Marina Baryshnikova, Yves Mols, Yoshiyuki Ishii, Reynald Alcotte, Han Han, Thomas Hantschel, Olivier Richard, Marianna Pantouvaki, Joris Van Campenhout, Dries Van Thourhout, Robert Langer and Bernardette Kunert
Crystals 2020, 10(4), 330; https://doi.org/10.3390/cryst10040330 - 22 Apr 2020
Cited by 28 | Viewed by 4355
Abstract
Nano-ridge engineering (NRE) is a novel heteroepitaxial approach for the monolithic integration of lattice-mismatched III-V devices on Si substrates. It has been successfully applied to GaAs for the realization of nano-ridge (NR) laser diodes and heterojunction bipolar transistors on 300 mm Si wafers. [...] Read more.
Nano-ridge engineering (NRE) is a novel heteroepitaxial approach for the monolithic integration of lattice-mismatched III-V devices on Si substrates. It has been successfully applied to GaAs for the realization of nano-ridge (NR) laser diodes and heterojunction bipolar transistors on 300 mm Si wafers. In this report we extend NRE to GaSb for the integration of narrow bandgap heterostructures on Si. GaSb is deposited by selective area growth in narrow oxide trenches fabricated on 300 mm Si substrates to reduce the defect density by aspect ratio trapping. The GaSb growth is continued and the NR shape on top of the oxide pattern is manipulated via NRE to achieve a broad (001) NR surface. The impact of different seed layers (GaAs and InAs) on the threading dislocation and planar defect densities in the GaSb NRs is investigated as a function of trench width by using transmission electron microscopy (TEM) as well as electron channeling contrast imaging (ECCI), which provides significantly better defect statistics in comparison to TEM only. An InAs/GaSb multi-layer heterostructure is added on top of an optimized NR structure. The high crystal quality and low defect density emphasize the potential of this monolithic integration approach for infrared optoelectronic devices on 300 mm Si substrates. Full article
(This article belongs to the Special Issue MOVPE Growth of Crystalline Film)
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14 pages, 672 KiB  
Article
Calculation of Surface Properties of Cubic and Hexagonal Crystals through Molecular Statics Simulations
by Zihan Tang, Yue Chen and Wei Ye
Crystals 2020, 10(4), 329; https://doi.org/10.3390/cryst10040329 - 22 Apr 2020
Cited by 9 | Viewed by 9045
Abstract
Surface property is an important factor that is widely considered in crystal growth and design. It is also found to play a critical role in changing the constitutive law seen in the classical elasticity theory for nanomaterials. Through molecular static simulations, this work [...] Read more.
Surface property is an important factor that is widely considered in crystal growth and design. It is also found to play a critical role in changing the constitutive law seen in the classical elasticity theory for nanomaterials. Through molecular static simulations, this work presents the calculation of surface properties (surface energy density, surface stress and surface stiffness) of some typical cubic and hexagonal crystals: face-centered-cubic (FCC) pure metals (Cu, Ni, Pd and Ag), body-centered-cubic (BCC) pure metals (Mo and W), diamond Si, zincblende GaAs and GaN, hexagonal-close-packed (HCP) pure metals (Mg, Zr and Ti), and wurzite GaN. Sound agreements of the bulk and surface properties between this work and the literature are found. New results are first reported for the surface stiffness of BCC pure metals, surface stress and surface stiffness of HCP pure metals, Si, GaAs and GaN. Comparative studies of the surface properties are carried out to uncover trends in their behaviors. The results in this work could be helpful to the investigation of material properties and structure performances of crystals. Full article
(This article belongs to the Special Issue Study Properties of Hexagonal Single Crystals and Polycrystals)
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21 pages, 2864 KiB  
Article
Structural Dynamics of An ELM-11 Framework Transformation Accompanied with Double-Step CO2 Gate sorption: An NMR Spin Relaxation Study
by Kazuki Ohazama, Takahiro Ueda, Kazuki Ukai, Manami Ichikawa, Hyuma Masu, Hiroshi Kajiro and Hirofumi Kanoh
Crystals 2020, 10(4), 328; https://doi.org/10.3390/cryst10040328 - 22 Apr 2020
Cited by 2 | Viewed by 3333
Abstract
[Cu(4,4'-bipyridine)2(BF4)2] (ELM-11), an elastic layer-structured MOF (metal-organic framework), is expected to be a sophisticated CO2 reservoir candidate because of its high capacity and recovery efficiency for CO2 sorption. While ELM-11 shows a unique double-step gate [...] Read more.
[Cu(4,4'-bipyridine)2(BF4)2] (ELM-11), an elastic layer-structured MOF (metal-organic framework), is expected to be a sophisticated CO2 reservoir candidate because of its high capacity and recovery efficiency for CO2 sorption. While ELM-11 shows a unique double-step gate sorption for CO2 gas, the dynamics of the structural transition have not yet been clarified. In this study, the dynamics of the 4,4'-bipyridine linkers and the BF4- anions were studied by determining 1H spin-lattice relaxation times (T1). The ELM-11 structural transition accompanying CO2 sorption was also examined through the CO2 uptake dependence of the 1H spin–spin relaxation time (T2), in addition to T1. In its closed form, the temperature dependence of the 1H T1 of ELM-11 was analyzed by considering the contributions of both paramagnetic and dipolar relaxations, which revealed the isotropic reorientation of BF4- and the torsional flipping of the 4,4'-bipyridine moieties. The resultant activation energy of 32 kJ mol-1 for the isotropic BF4− reorientation is suggestive of strong (B-F...Cu2+) interactions between Cu(II) and the F atoms in BF4−. Furthermore, the CO2 uptake dependence of T1 was found to be dominated by competition between the increase in the longitudinal relaxation time of the electron spins and the decrease in the spin density in the unit cell. Full article
(This article belongs to the Special Issue Crystallography of Structural Phase Transformations)
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11 pages, 2475 KiB  
Article
Optical and Thermoelectric Properties of Surface-Oxidation Sensitive Layered Zirconium Dichalcogenides ZrS2−xSex (x = 0, 1, 2) Crystals Grown by Chemical Vapor Transport
by Thalita Maysha Herninda and Ching-Hwa Ho
Crystals 2020, 10(4), 327; https://doi.org/10.3390/cryst10040327 - 22 Apr 2020
Cited by 18 | Viewed by 3567
Abstract
In this work, structure, optical, and thermoelectric properties of layered ZrS2−xSex single crystals with selenium composition of x = 0, 1, and 2 were examined. Single crystals of zirconium dichalcogenides layer compounds were grown by chemical vapor transport method using [...] Read more.
In this work, structure, optical, and thermoelectric properties of layered ZrS2−xSex single crystals with selenium composition of x = 0, 1, and 2 were examined. Single crystals of zirconium dichalcogenides layer compounds were grown by chemical vapor transport method using I2 as the transport agent. X-ray diffraction (XRD) and high-resolution transmission electron microscope (HRTEM) results indicated that ZrS2−xSex (x = 0, 1, and 2) were crystalized in hexagonal CdI2 structure with one-layer trigonal (1T) stacking type. X-ray photoelectron and energy dispersive X-ray measurements revealed oxidation sensitive behavior of the chalcogenides series. Transmittance and optical absorption showed an indirect optical gap of about 1.78 eV, 1.32 eV, and 1.12 eV for the ZrS2−xSex with x = 0, 1, and 2, respectively. From the result of thermoelectric experiment, ZrSe2 owns the highest figure-of merit (ZT) of ~0.085 among the surface-oxidized ZrS2−xSex series layer crystals at 300 K. The ZT values of the ZrS2−xSex (x = 0, 1, and 2) series also reveal increase with the increase of Se content owing to the increase of carrier concentration and mobility in the highly Se-incorporated zirconium dichalcogenides with surface states. Full article
(This article belongs to the Special Issue A 10 Years Journey: Chemical, Physical, and Biological Properties and Applications of Crystals)
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16 pages, 9097 KiB  
Article
Effect of Strain on Transformation Diagrams of 100Cr6 Steel
by Rostislav Kawulok, Ivo Schindler, Jaroslav Sojka, Petr Kawulok, Petr Opěla, Lukáš Pindor, Eduard Grycz, Stanislav Rusz and Vojtěch Ševčák
Crystals 2020, 10(4), 326; https://doi.org/10.3390/cryst10040326 - 21 Apr 2020
Cited by 9 | Viewed by 3714
Abstract
Based on dilatometric tests, the effect of various values of previous deformation on the kinetics of austenite transformations during the cooling of 100Cr6 steel has been studied. Dilatometric tests have been performed with the use of the optical dilatometric module of the plastometer [...] Read more.
Based on dilatometric tests, the effect of various values of previous deformation on the kinetics of austenite transformations during the cooling of 100Cr6 steel has been studied. Dilatometric tests have been performed with the use of the optical dilatometric module of the plastometer Gleeble 3800. The obtained results were compared to metallographic analyses and hardness measurements HV30. Uniaxial compression deformations were chosen as follows: 0, 0.35, and 1; note that these are true (logarithmic) deformations. The highly important finding was the absence of bainite. In addition, it has been verified that with the increasing amount of deformation, there is a further shift in the pearlitic region to higher cooling rates. The previous deformation also affected the temperature martensite start, which decreased due to deformation. The deformation value of 1 also shifted the critical cooling rate required for martensite formation from the 12 °C/s to 25 °C/s. Full article
(This article belongs to the Special Issue Crystal Plasticity)
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9 pages, 1693 KiB  
Article
ZnO@TiO2 Core/Shell Nanowire Arrays with Different Thickness of TiO2 Shell for Dye-Sensitized Solar Cells
by Liqing Liu, Hui Wang, Dehao Wang, Yongtao Li, Xuemin He, Hongguang Zhang and Jianping Shen
Crystals 2020, 10(4), 325; https://doi.org/10.3390/cryst10040325 - 21 Apr 2020
Cited by 11 | Viewed by 3096
Abstract
The ZnO@TiO2 core/shell nanowire arrays with different thicknesses of the TiO2 shell were synthesized, through depositing TiO2 on the ZnO nanowire arrays using the pulsed laser deposition process. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) images show that [...] Read more.
The ZnO@TiO2 core/shell nanowire arrays with different thicknesses of the TiO2 shell were synthesized, through depositing TiO2 on the ZnO nanowire arrays using the pulsed laser deposition process. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) images show that these core/shell nanowires were homogeneously coated with TiO2 nanoparticles with high crystallinity, appearing to be a rather rough surface compared to pure ZnO nanowires. The efficiency of ZnO@TiO2 core/shell structure-based dye-sensitized solar cells (DSSCs) was improved compared with pure ZnO nanowires. This is mainly attributed to the enlarged internal surface area of the core/shell structures, which increases dye adsorption on the anode to improve the light harvest. In addition, the energy barrier which formed at the interface between ZnO and TiO2 promoted the charge separation and suppressed the carrier recombination. Furthermore, the efficiency of DSSCs was further improved by increasing the thickness of the TiO2 shell. This work shows an efficient method to achieve high power conversion efficiency in core/shell nanowire-based DSSCs. Full article
(This article belongs to the Special Issue Zinc Oxide Nanomaterials and Based Devices)
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13 pages, 3976 KiB  
Article
Experimental Sensing and DFT Mechanism of Zn(II) Complex for Highly Sensitive and Selective Detection of Acetone
by Mohd. Muddassir, Mohammad Usman, Abdullah Alarifi, Mohd. Afzal, Khulud Abdullah Alshali, Abeer Beagan, Abhinav Kumar, Naaser A. Y. Abduhd and Musheer Ahmad
Crystals 2020, 10(4), 324; https://doi.org/10.3390/cryst10040324 - 20 Apr 2020
Cited by 2 | Viewed by 2520
Abstract
In the present work, a new Zn(II) perchlorate complex with 2,2’–bipyridyl of formulation {[Zn(bipy)2(H2O)](ClO4)2} (1) was obtained and well analyzed. This chemosensor was evaluated as a selective sensor for acetone among the several [...] Read more.
In the present work, a new Zn(II) perchlorate complex with 2,2’–bipyridyl of formulation {[Zn(bipy)2(H2O)](ClO4)2} (1) was obtained and well analyzed. This chemosensor was evaluated as a selective sensor for acetone among the several different organic solvents(CH3OH, EtOH, i–PrOH, i–BuOH, CHCl3, CH2Cl2, CCl4, C6H6, C7H8, C8H10, C2H3N, C3H7NO, C4H8O2, C3H6O3) in a fluorescence turn–off response in accordance with theoretical calculations. Sensing experiments were performed at ambient temperature which shows the acetone molecule distinctly reduces transfer of energy barrier to complex 1 and hence, produces remarkable luminescent quenching. Also, the weak intermolecular hydrogen–bonding interactions thanks to the presence of various hydrogen bonding donors and acceptors, exist between ligand molecules, which were broken during fluorescence, resulting in quenching. The stoichiometry ratio and association constant were evaluated using Benesi–Hildebrand relation giving 1:1 stoichiometry between complex 1 and acetone. Additionally, DFT results can also explicate the significant response on complex 1 upon addition of acetone. This work is vital in a new loom for the detection of acetone and other ketones. Full article
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15 pages, 7684 KiB  
Review
Photoaligning and Photopatterning: New LC Technology
by Vladimir Chigrinov, Jiatong Sun and Xiaoqian Wang
Crystals 2020, 10(4), 323; https://doi.org/10.3390/cryst10040323 - 20 Apr 2020
Cited by 39 | Viewed by 5181
Abstract
We demonstrate a physical model of photoalignment and photopatterning based on rotational diffusion in solid azo-dye nanolayers. We also highlight the new applications of photoalignment and photopatterning in display and photonics such as: (i) liquid crystal (LC) E-paper devices, including optically rewritable LC [...] Read more.
We demonstrate a physical model of photoalignment and photopatterning based on rotational diffusion in solid azo-dye nanolayers. We also highlight the new applications of photoalignment and photopatterning in display and photonics such as: (i) liquid crystal (LC) E-paper devices, including optically rewritable LC E-paper on flexible substrates as 3D E-paper, as well as optically rewritable technology for photonics devices; (ii) photonics LC devices, such as LC Switches, polarization controllers and polarization rotators, variable optical attenuators, LC filled photonic crystal fiber, switchable diffraction grating; (iii) patterned micro-polarizer array using photo-alignment technology for image sensor; (iv) electrically tunable liquid crystal q-plates; (v) electrically switchable liquid crystal Fresnel lens; (vi) liquid crystal optical elements with integrated Pancharatnam-Berry phases. We are sure, that in the field of (LC), the main point is no longer display research, but new photonic applications of LC are emerging in telecommunication, fiber optical communication systems, sensors, switchable lenses, LC light converters and other LC photonics devices. Full article
(This article belongs to the Special Issue Micro and Nano Patterned Substrates for Liquid Crystal Alignment (Volume II))
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16 pages, 3678 KiB  
Article
Synthesis, Characterization and Catalytic Evaluation of Chromium Oxide Deposited on Titania–Silica Mesoporous Nanocomposite for the Ethane Dehydrogenation with CO2
by Abdulrhman S. Al-Awadi, Ahmed Mohamed El-Toni, Saeed M. Al-Zahrani, Ahmed E. Abasaeed and Aslam Khan
Crystals 2020, 10(4), 322; https://doi.org/10.3390/cryst10040322 - 20 Apr 2020
Cited by 3 | Viewed by 2958
Abstract
Ti modification of mesoporous silica support has been reported as an effective way to enhance Cr–Ti–Si interactions that, in turn, impact the catalytic dehydrogenation of ethane with CO2. However, such modification necessitates a repeated, time-consuming and tedious process. In this work, [...] Read more.
Ti modification of mesoporous silica support has been reported as an effective way to enhance Cr–Ti–Si interactions that, in turn, impact the catalytic dehydrogenation of ethane with CO2. However, such modification necessitates a repeated, time-consuming and tedious process. In this work, a simple, fast and facile approach has been utilized to synthesize chromium-oxide-loaded titania–silica mesoporous nanocomposites. A series of Cr(y)/Ti(x)–Si mesoporous nanocomposite catalysts with varying Ti and Cr contents were prepared and tested in the dehydrogenation of ethane with carbon dioxide. The as-synthesized catalysts were characterized by XRD, TEM, SEM, BET, UV–Vis–DR, XPS and H2–TPR techniques. The effect of titanium content, as well as chromium loading on the performance of the prepared Cr(y)/Ti(x)–Si catalysts, was investigated. It was found that 2.2 and 8 wt % are the optimum titanium and chromium contents in the synthesized catalysts for obtaining the highest catalytic activity. The superior catalytic performance of the Cr(8)/Ti(2.2)–Si catalyst can be attributed to a higher dispersion of the Cr species, as well as a higher content of the redox Cr species on the surface of the Cr/Ti–Si catalyst. The results showed that the Cr(8)/Ti(2.2)–Si catalyst efficiently dehydrogenated C2H6 in the presence of CO2 giving a 52.3% ethane conversion and 48.0% ethylene yield at 700 °C reaction temperature. Full article
(This article belongs to the Section Hybrid and Composite Crystalline Materials)
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47 pages, 1656 KiB  
Review
Structural, Optical and Dynamic Properties of Thin Smectic Films
by Izabela Śliwa and A. V. Zakharov
Crystals 2020, 10(4), 321; https://doi.org/10.3390/cryst10040321 - 20 Apr 2020
Cited by 3 | Viewed by 1961
Abstract
The problem of predicting structural and dynamic behavior associated with thin smectic films, both deposited on a solid surface or stretched over an opening, when the temperature is slowly increased above the bulk transition temperature towards either the nematic or isotropic phases, remains [...] Read more.
The problem of predicting structural and dynamic behavior associated with thin smectic films, both deposited on a solid surface or stretched over an opening, when the temperature is slowly increased above the bulk transition temperature towards either the nematic or isotropic phases, remains an interesting one in the physics of condensed matter. A useful route in studies of structural and optical properties of thin smectic films is provided by a combination of statistical–mechanical theories, hydrodynamics of liquid crystal phases, and optical and calorimetric techniques. We believe that this review shows some useful routes not only for the further examining of the validity of a theoretical description of thin smectic films, both deposited on a solid surface or stretched over an opening, but also for analyzing their structural, optical, and dynamic properties. Full article
(This article belongs to the Special Issue Structural and Optical Properties of Smectic Films)
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11 pages, 3544 KiB  
Article
Laser Cladding of Al0.5CoCrCuFeNiSi High Entropy Alloy Coating without and with Yttria Addition on H13 Steel
by Jingda Liu, Yuxin Guan, Xuechen Xia, Pai Peng, Qifeng Ding and Xiaotao Liu
Crystals 2020, 10(4), 320; https://doi.org/10.3390/cryst10040320 - 20 Apr 2020
Cited by 10 | Viewed by 2671
Abstract
Al0.5CoCrCuFeNiSi high entropy alloy coating without and with a 1 wt.% Y2O3 addition was fabricated by laser cladding technique on H13 substrate. The results showed that the laser cladding coatings without and with Y2O3 addition [...] Read more.
Al0.5CoCrCuFeNiSi high entropy alloy coating without and with a 1 wt.% Y2O3 addition was fabricated by laser cladding technique on H13 substrate. The results showed that the laser cladding coatings without and with Y2O3 addition consist of a mixture of body centered cubic (BCC) dendrites and face centered cubic (FCC) interdendrites. With the addition of Y2O3, the peaks of BCC dendrites in the coating shifted to leftwards, which is caused by the distortion of lattice due to the dissolution of Y with larger atomic radius. There exist cracks and porosities in the coating without Y2O3 addition. With Y2O3 addition, the cracks and porosities in the laser cladding coating were inhibited greatly. In addition, the microstructure of the coating with Y2O3 addition was refined due to the improving of the ratio of nucleation. The enhancement of properties, such as hardness, wear resistance and corrosion resistance, of the coating with Y2O3 addition came from the inhibition of cracks and porosities and the refinement of microstructure. Full article
(This article belongs to the Special Issue Development of High Entropy Alloys)
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12 pages, 3869 KiB  
Article
Binary Liquid Crystal Mixtures Based on Schiff Base Derivatives with Oriented Lateral Substituents
by Rua B. Alnoman, Mohamed Hagar, Hoda A. Ahmed, Magdi M. Naoum, Hanefah A. Sobaih, Jawaher S. Almshaly, Mawadh M. Haddad, Rana A. Alhaisoni and Tahani A. Alsobhi
Crystals 2020, 10(4), 319; https://doi.org/10.3390/cryst10040319 - 20 Apr 2020
Cited by 15 | Viewed by 3394
Abstract
Binary mixtures of the laterally substituted Schiff base/ester derivatives, namely 4-((2- or 3-) substituted phenyl imino methyl) phenyl-4”-alkoxy benzoates, Ia–d, were prepared and mesomorphically studied by differential scanning calorimetry (DSC) and their mesophases identified by polarized optical microscopy (POM). The lateral group (1-naphthyl, [...] Read more.
Binary mixtures of the laterally substituted Schiff base/ester derivatives, namely 4-((2- or 3-) substituted phenyl imino methyl) phenyl-4”-alkoxy benzoates, Ia–d, were prepared and mesomorphically studied by differential scanning calorimetry (DSC) and their mesophases identified by polarized optical microscopy (POM). The lateral group (1-naphthyl, 2-F, 2-Br, 3-F in Ia–d, respectively) is attached to different positions of the phenyl Schiff moiety. The mixtures investigated were made from two differently shaped compounds that differ from each other in the polarity, size, orientation, and relative positions of the lateral group. The results revealed that the binary mixture Ia/Ib (bearing the naphthyl and 2-flouro substituents) exhibited the SmA phase, which covered the whole composition range. For the mixtures Ib/Id (2-F and 2-Br), the isomeric lateral F-group in compound Ib distributed the SmA arrangement of Id. In the Ic/Id mixture bearing two positionally and structurally different substituents, the addition of Ic to Id resulted in solid binary mixtures where its behavior may be attributed to the negligible steric effect of the small electronegative fluorine atom compared to the Br atom. Density functional theory (DFT) theoretical calculations were carried out to estimate the geometrical parameters of individual components and to show the effect of these parameters in the mesophase behavior of the binary system, where the higher dipole moment of Id (6 Debye) may be the reason for its high π–π molecular stacking, which influences its mesophase range and stability. Full article
(This article belongs to the Section Liquid Crystals)
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7 pages, 2115 KiB  
Article
Capacitance Properties in Ba0.3Sr0.7Zr0.18Ti0.82O3 Thin Films on Silicon Substrate for Thin Film Capacitor Applications
by Xiaoyang Chen, Taolan Mo, Binbin Huang, Yun Liu and Ping Yu
Crystals 2020, 10(4), 318; https://doi.org/10.3390/cryst10040318 - 19 Apr 2020
Cited by 5 | Viewed by 2438
Abstract
Crystalline Ba0.3Sr0.7Zr0.18Ti0.82O3 (BSZT) thin film was grown on Pt(111)/Ti/SiO2/Si substrate using radio frequency (RF) magnetron sputtering. Based on our best knowledge, there are few reports in the literature to prepare the perovskite [...] Read more.
Crystalline Ba0.3Sr0.7Zr0.18Ti0.82O3 (BSZT) thin film was grown on Pt(111)/Ti/SiO2/Si substrate using radio frequency (RF) magnetron sputtering. Based on our best knowledge, there are few reports in the literature to prepare the perovskite BSZT thin films, especially using the RF magnetron sputtering method. The microstructure of the thin films was characterized using X-ray diffraction (XRD) and scanning electron microscopy (SEM), and capacitance properties, such as capacitance density, leakage behavior, and the temperature dependence of capacitance were investigated experimentally. The prepared perovskite BSZT film showed a low leakage current density of 7.65 × 10−7 A/cm2 at 60 V, and large breakdown strength of 4 MV/cm. In addition, the prepared BSZT thin film capacitor not only exhibits an almost linear and acceptable change (ΔC/C ~13.6%) of capacitance from room temperature to 180 °C but also a large capacitance density of 1.7 nF/mm2 at 100 kHz, which show great potential for coupling and decoupling applications. Full article
(This article belongs to the Special Issue Synthesis and Characterization of Ferroelectrics)
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7 pages, 2161 KiB  
Communication
Hexnuclear Cadmium(II) Cluster Constructed from Tris(2-methylpyridyl)amine (TPA) and Azides
by Franz A. Mautner, Roland C. Fischer, Bailey R. Williams, Salah S. Massoud and Nahed M. H. Salem
Crystals 2020, 10(4), 317; https://doi.org/10.3390/cryst10040317 - 19 Apr 2020
Cited by 7 | Viewed by 2040
Abstract
A novel rare hexa nuclear cadmium(II)–azide cluster, [Cd6(TPA)4(μ3-1,1,3-N3)4(μ2-1,1-N3)6](ClO4)2·2H2O (1) was isolated and structurally characterized, in which the azide ligands reveal μ-1,1,3- and μ-1,1-N3 bridging modes. Full article
(This article belongs to the Section Inorganic Crystalline Materials)
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16 pages, 3566 KiB  
Article
Solvent Effects on Catechol Crystal Habits and Aspect Ratios: A Combination of Experiments and Molecular Dynamics Simulation Study
by Dan Zhu, Shihao Zhang, Pingping Cui, Chang Wang, Jiayu Dai, Ling Zhou, Yaohui Huang, Baohong Hou, Hongxun Hao, Lina Zhou and Qiuxiang Yin
Crystals 2020, 10(4), 316; https://doi.org/10.3390/cryst10040316 - 18 Apr 2020
Cited by 16 | Viewed by 3989
Abstract
This work could help to better understand the solvent effects on crystal habits and aspect ratio changes at the molecular level, which provide some guidance for solvent selection in industrial crystallization processes. With the catechol crystal habits acquired using both experimental and simulation [...] Read more.
This work could help to better understand the solvent effects on crystal habits and aspect ratio changes at the molecular level, which provide some guidance for solvent selection in industrial crystallization processes. With the catechol crystal habits acquired using both experimental and simulation methods in isopropanol, methyl acetate and ethyl acetate, solvent effects on crystal morphology were explored based on the modified attachment energy model. Firstly, morphologically dominant crystal faces were obtained with the predicted crystal habit in vacuum. Then, modified attachment energies were calculated by the molecular dynamics simulation to modify the crystal shapes in a real solvent environment, and the simulation results were in agreement with the experimental ones. Meanwhile, the surface properties such as roughness and the diffusion coefficient were introduced to analyze the solvent adsorption behaviors and the radial distribution function curves were generated to distinguish diverse types of interactions like hydrogen bonds and van der Waals forces. Results show that the catechol crystal habits were affected by the combination of the attachment energy, surface structures and molecular interaction types. Moreover, the changing aspect ratios of catechol crystals are closely related to the existence of hydrogen bonds which contribute to growth inhibition on specific faces. Full article
(This article belongs to the Special Issue Advances in Industrial Crystallization)
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14 pages, 4436 KiB  
Article
Toward Programmed Complex Stress-Induced Mechanical Deformations of Liquid Crystal Elastomers
by Devesh Mistry and Helen F. Gleeson
Crystals 2020, 10(4), 315; https://doi.org/10.3390/cryst10040315 - 18 Apr 2020
Cited by 3 | Viewed by 2935
Abstract
We prepare a liquid crystal elastomer (LCE) with a spatially patterned liquid crystal director field from an all-acrylate LCE. Mechanical deformations of this material lead to a complex and spatially varying deformation with localised body rotations, shears and extensions. Together, these dictate the [...] Read more.
We prepare a liquid crystal elastomer (LCE) with a spatially patterned liquid crystal director field from an all-acrylate LCE. Mechanical deformations of this material lead to a complex and spatially varying deformation with localised body rotations, shears and extensions. Together, these dictate the evolved shape of the deformed film. Using polarising microscopy, we map the local rotation of the liquid crystal director in Eulerian and Lagrangian frames and use these to determine rules for programming complex, stress-induced mechanical shape deformations of LCEs. Moreover, by applying a recently developed empirical model for the mechanical behaviour of our LCE, we predict the non-uniform stress distributions in our material. These results show the promise of empirical approaches to modelling the anisotropic and nonlinear mechanical responses of LCEs which will be important as the community moves toward realising real-world, LCE-based devices. Full article
(This article belongs to the Special Issue Early Career Stars of the Decade)
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12 pages, 5599 KiB  
Article
Topological Defect Arrays in Nematic Liquid Crystals Assisted by Polymeric Pillar Arrays: Effect of the Geometry of Pillars
by MinSu Kim and Francesca Serra
Crystals 2020, 10(4), 314; https://doi.org/10.3390/cryst10040314 - 18 Apr 2020
Cited by 13 | Viewed by 4159
Abstract
Topological defects that spontaneously occur in condensed matter and structured fluids such as liquid crystals are useful for their elastic and optical properties, but often the applicability of defect arrays to optics and photonic devices relies on the regularity and tunability of the [...] Read more.
Topological defects that spontaneously occur in condensed matter and structured fluids such as liquid crystals are useful for their elastic and optical properties, but often the applicability of defect arrays to optics and photonic devices relies on the regularity and tunability of the system. In our recent work [Adv. Opt. Mater. 8, 1900991 (2020)], we showed the formation of regular, reconfigurable, and scalable patterns by exploiting the elastic response of a defect array in liquid crystals in the presence of a polymeric pillar array. In this work, we experimentally investigate the role of size and shape of the pillars on the defect array. We find that the pillar size and geometry provide additional means to regulate the response time, the threshold voltage for the defects’ formation, and the spatial arrangement of the defects. Full article
(This article belongs to the Special Issue Early Career Stars of the Decade)
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12 pages, 4209 KiB  
Article
Physical Characteristics of Cilostazol–Hydroxybenzoic Acid Cocrystals Prepared Using a Spray Drying Method
by Maho Urano, Megumi Kitahara, Kae Kishi, Eiichi Goto, Tatsuaki Tagami, Toshiro Fukami and Tetsuya Ozeki
Crystals 2020, 10(4), 313; https://doi.org/10.3390/cryst10040313 - 17 Apr 2020
Cited by 11 | Viewed by 3060
Abstract
The cocrystal formation of pharmaceuticals can improve the various physical properties of drugs, such as solubility, without the need for chemical modification of the drug substances. In the present study, we prepared cocrystals of cilostazol and additive coformers (derivatives of hydroxybenzoic acid) using [...] Read more.
The cocrystal formation of pharmaceuticals can improve the various physical properties of drugs, such as solubility, without the need for chemical modification of the drug substances. In the present study, we prepared cocrystals of cilostazol and additive coformers (derivatives of hydroxybenzoic acid) using a spray drying method. Based on the preparation of the cocrystals of cilostazol and the coformers as reported previously, the characteristics of the cilostazol cocrystals prepared using solvent evaporation, slurry, and spray drying methods were compared. The physical characterization revealed that the spray drying method successfully produced cilostazol–4-hydroxybenzoic acid and cilostazol–2,4-dihydroxybenzoic acid cocrystals, whereas samples of cocrystals of cilostazol and 2,5-dihydroxybenzoic acid produced via the spray drying process appeared to contain coformer polymorphs. The dissolution of cilostazol was improved using the spray-dried cocrystal samples composed of coformers compared to samples prepared using cilostazol alone or a physical mixture. The present results provide useful information regarding the manufacture of cilostazol cocrystals and pharmaceutical cocrystals via spray drying in large-batch production. Full article
(This article belongs to the Special Issue Pharmaceutical Crystals and Its Application)
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12 pages, 3672 KiB  
Article
Study on the Softening Behavior of Cu–Cr–In Alloy during Annealing
by Yunqing Zhu, Linsheng Tang, Weibin Xie, Huiming Chen, Hang Wang and Bin Yang
Crystals 2020, 10(4), 312; https://doi.org/10.3390/cryst10040312 - 17 Apr 2020
Cited by 3 | Viewed by 2055
Abstract
The softening behavior of a cold-drawn Cu–Cr–In alloy was investigated during annealing between 450 °C and 700 °C. The properties and microstructure evolution of the alloy were characterized using a microhardness tester, electron back-scatter diffraction, and transmission electron microscopy. Elemental In addition was [...] Read more.
The softening behavior of a cold-drawn Cu–Cr–In alloy was investigated during annealing between 450 °C and 700 °C. The properties and microstructure evolution of the alloy were characterized using a microhardness tester, electron back-scatter diffraction, and transmission electron microscopy. Elemental In addition was found to hinder the dislocation movement and delay the recovery and recrystallization of the Cu–Cr–In alloy. The experimental data were analyzed using the Johnson–Mehlv–Avramiv–Kolmogorov model. The activation energy of recrystallization of the 60% cold-drawn Cu0.54Cr0.17In alloy was 188.29 ± 18.44 kJ/mol, and the recrystallization mechanism of the alloy was attributed mainly to Cu self-diffusion. Full article
(This article belongs to the Special Issue Advance in Alloy Materials)
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10 pages, 3371 KiB  
Article
Effect of Strains and V-Shaped Pit Structures on the Performance of GaN-Based Light-Emitting Diodes
by Shuo-Wei Chen, Chia-Jui Chang and Tien-Chang Lu
Crystals 2020, 10(4), 311; https://doi.org/10.3390/cryst10040311 - 17 Apr 2020
Cited by 6 | Viewed by 4350
Abstract
Strains and V-shaped pits are essential factors for determining the efficiency of GaN-based light-emitting diodes (LEDs). In this study, we systematically analyzed GaN LED structures on patterned sapphire substrates (PSSs) with two types of growth temperature employed for prestrained layers and three different [...] Read more.
Strains and V-shaped pits are essential factors for determining the efficiency of GaN-based light-emitting diodes (LEDs). In this study, we systematically analyzed GaN LED structures on patterned sapphire substrates (PSSs) with two types of growth temperature employed for prestrained layers and three different thickness of n-type GaN layers by using cathodoluminescence (CL), microphotoluminescence (PL), and depth-resolved confocal Raman spectroscopy. The results indicated that V-pits formation situation can be analyzed using CL. From the emission peak intensity ratio of prestrained layers and multiple quantum wells (MQWs) in the CL spectrum, information regarding strain relaxation between prestrained layers and MQWs was determined. Furthermore, micro-PL and depth-resolved confocal Raman spectroscopy were employed to validate the results obtained from CL measurements. The growth conditions of prestrained layers played a dominant role in the determination of LED performance. The benefit of the thick layer of n-GaN was the strain reduction, which was counteracted by an increase in light absorption in thick n-type doped layers. Consequently, the most satisfactory LED performance was observed in a structure with relatively lower growth temperature of prestrained layers that exhibited larger V-pits, leading to higher strain relaxation and thinner n-type GaN layers, which prevent light absorption caused by n-type GaN layers. Full article
(This article belongs to the Special Issue GaN-Based Optoelectronic Materials and Light Emitting Devices)
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22 pages, 4545 KiB  
Article
Modeling the Maximum Magnetic Entropy Change of Doped Manganite Using a Grid Search-Based Extreme Learning Machine and Hybrid Gravitational Search-Based Support Vector Regression
by Sami M. Ibn Shamsah and Taoreed O. Owolabi
Crystals 2020, 10(4), 310; https://doi.org/10.3390/cryst10040310 - 16 Apr 2020
Cited by 24 | Viewed by 3025
Abstract
The thermal response of a magnetic solid to an applied magnetic field constitutes magnetocaloric effect. The maximum magnetic entropy change (MMEC) is one of the quantitative parameters characterizing this effect, while the magnetic solids exhibiting magnetocaloric effect have great potential in magnetic refrigeration [...] Read more.
The thermal response of a magnetic solid to an applied magnetic field constitutes magnetocaloric effect. The maximum magnetic entropy change (MMEC) is one of the quantitative parameters characterizing this effect, while the magnetic solids exhibiting magnetocaloric effect have great potential in magnetic refrigeration technology as they offer a green solution to the known pollutant-based refrigerants. In order to determine the MMEC of doped manganite and the influence of dopants on the magnetocaloric effect of doped manganite compounds, this work developed a grid search (GS)-based extreme learning machine (ELM) and hybrid gravitational search algorithm (GSA)-based support vector regression (SVR) for estimating the MMEC of doped manganite compounds using ionic radii and crystal lattice parameters as descriptors. Based on the root-mean-square error (RMSE), the developed GSA-SVR-radii model performs better than the existing genetic algorithm (GA)-SVR-ionic model in the literature by 27.09%, while the developed GSA-SVR-crystal model performs better than the existing GA-SVR-lattice model in the literature by 38.34%. Similarly, the developed ELM-GS-crystal model performs better than the existing GA-SVR-ionic model with a performance enhancement of 14.39% and 20.65% using the mean absolute error (MAE) and RMSE, respectively, as performance measuring parameters. The developed models also perform better than the existing models using correlation coefficient as the performance measuring parameter when validated with experimentally measured MMEC. The superior performance of the present models coupled with easy accessibility of the descriptors definitely will facilitate the synthesis of doped manganite compounds with a high magnetocaloric effect without experimental stress. Full article
(This article belongs to the Special Issue Intermetallic Compound)
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16 pages, 2364 KiB  
Article
Gypsum Crystallization during Reverse Osmosis Desalination of Water with High Sulfate Content in Presence of a Novel Fluorescent-Tagged Polyacrylate
by Maxim Oshchepkov, Vladimir Golovesov, Anastasia Ryabova, Anatoly Redchuk, Sergey Tkachenko, Alexei Pervov and Konstantin Popov
Crystals 2020, 10(4), 309; https://doi.org/10.3390/cryst10040309 - 16 Apr 2020
Cited by 18 | Viewed by 3936
Abstract
Gypsum scaling in reverse osmosis (RO) desalination process is studied in presence of a novel fluorescent 1,8-naphthalimide-tagged polyacrylate (PAA-F1) by fluorescent microscopy, scanning electron microscopy (SEM), dynamic light scattering (DLS) and a particle counter technique. A comparison of PAA-F1 with a previously reported [...] Read more.
Gypsum scaling in reverse osmosis (RO) desalination process is studied in presence of a novel fluorescent 1,8-naphthalimide-tagged polyacrylate (PAA-F1) by fluorescent microscopy, scanning electron microscopy (SEM), dynamic light scattering (DLS) and a particle counter technique. A comparison of PAA-F1 with a previously reported fluorescent bisphosphonate HEDP-F revealed a better PAA-F1 efficacy, and a similar behavior of polyacrylate and bisphosphonate inhibitors under the same RO experimental conditions. Despite expectations, PAA-F1 does not interact with gypsum. For both reagents, it is found that scaling takes place in the bulk retentate phase via heterogeneous nucleation step. The background “nanodust” plays a key role as a gypsum nucleation center. Contrary to popular belief, an antiscalant interacts with “nanodust” particles, isolating them from calcium and sulfate ions sorption. Therefore, the number of gypsum nucleation centers is reduced, and in turn, the overall scaling rate is diminished. It is also shown that, the scale formation scenario changes from the bulk medium, in the beginning, to the sediment crystals growth on the membrane surface, at the end of the desalination process. It is demonstrated that the fluorescent-tagged antiscalants may become very powerful tools in membrane scaling inhibition studies. Full article
(This article belongs to the Special Issue Advances in Industrial Crystallization)
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