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Crystals, Volume 10, Issue 5 (May 2020) – 83 articles

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Cover Story (view full-size image) Although gold nanoclusters represent the link species between atoms and nanoparticles and are the [...] Read more.
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Open AccessArticle
Dual Photonic–Phononic Crystal Slot Nanobeam with Gradient Cavity for Liquid Sensing
Crystals 2020, 10(5), 421; https://doi.org/10.3390/cryst10050421 - 25 May 2020
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Abstract
A dual photonic–phononic crystal slot nanobeam with a gradient cavity for liquid sensing is proposed and analyzed using the finite-element method. Based on the photonic and phononic crystals with mode bandgaps, both optical and acoustic waves can be confined within the slot and [...] Read more.
A dual photonic–phononic crystal slot nanobeam with a gradient cavity for liquid sensing is proposed and analyzed using the finite-element method. Based on the photonic and phononic crystals with mode bandgaps, both optical and acoustic waves can be confined within the slot and holes to enhance interactions between sound/light and analyte solution. The incorporation of a gradient cavity can further concentrate energy in the cavity and reduce energy loss by avoiding abrupt changes in lattices. The newly designed sensor is aimed at determining both the refractive index and sound velocity of the analyte solution by utilizing optical and acoustic waves. The effect of the cavity gradient on the optical sensing performance of the nanobeam is thoroughly examined. By optimizing the design of the gradient cavity, the photonic–phononic sensor has significant sensing performances on the test of glucose solutions. The currently proposed device provides both optical and acoustic detections. The analyte can be cross-examined, which consequently will reduce the sample sensing uncertainty and increase the sensing precision. Full article
(This article belongs to the Special Issue Sonic and Photonic Crystals)
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Open AccessArticle
Degradation-Induced Actuation in Oxidation-Responsive Liquid Crystal Elastomers
Crystals 2020, 10(5), 420; https://doi.org/10.3390/cryst10050420 - 25 May 2020
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Abstract
Stimuli-responsive materials that exhibit a mechanical response to specific biological conditions are of considerable interest for responsive, implantable medical devices. Herein, we report the synthesis, processing and characterization of oxidation-responsive liquid crystal elastomers that demonstrate programmable shape changes in response to reactive oxygen [...] Read more.
Stimuli-responsive materials that exhibit a mechanical response to specific biological conditions are of considerable interest for responsive, implantable medical devices. Herein, we report the synthesis, processing and characterization of oxidation-responsive liquid crystal elastomers that demonstrate programmable shape changes in response to reactive oxygen species. Direct ink writing (DIW) is used to fabricate Liquid Crystal Elastomers (LCEs) with programmed molecular orientation and anisotropic mechanical properties. LCE structures were immersed in different media (oxidative, basic and saline) at body temperature to measure in vitro degradation. Oxidation-sensitive hydrophobic thioether linkages transition to hydrophilic sulfoxide and sulfone groups. The introduction of these polar moieties brings about anisotropic swelling of the polymer network in an aqueous environment, inducing complex shape changes. 3D-printed uniaxial strips exhibit 8% contraction along the nematic director and 16% orthogonal expansion in oxidative media, while printed LCEs azimuthally deform into cones 19 times their original thickness. Ultimately, these LCEs degrade completely. In contrast, LCEs subjected to basic and saline solutions showed no apparent response. These oxidation-responsive LCEs with programmable shape changes may enable a wide range of applications in target specific drug delivery systems and other diagnostic and therapeutic tools. Full article
(This article belongs to the Special Issue Early Career Stars of the Decade)
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Open AccessArticle
Synthesis, Structural Characterization and Hirshfeld Surface Analysis of a 2D Coordination Polymer, [Co(4-dpds)(bdc)(H2O)2] 4-dpds
Crystals 2020, 10(5), 419; https://doi.org/10.3390/cryst10050419 - 24 May 2020
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Abstract
A two-dimensional (2D) coordination polymer, [Co(4-dpds)(bdc)(H2O)2]·4-dpds (1) (4-dpds = 4,4′-dipyridyldusulfide and bdc2− = dianion of benzenedicarboxylic acid), has been synthesized and structurally determined by single-crystal X-ray diffractometer. In 1, the bdc2− and 4-dpds both [...] Read more.
A two-dimensional (2D) coordination polymer, [Co(4-dpds)(bdc)(H2O)2]·4-dpds (1) (4-dpds = 4,4′-dipyridyldusulfide and bdc2− = dianion of benzenedicarboxylic acid), has been synthesized and structurally determined by single-crystal X-ray diffractometer. In 1, the bdc2− and 4-dpds both act as bridging ligands connecting the Co(II) ions to form a 2D wrinkled-like layered coordination polymer. Two wrinkled-like layered coordination polymers are mutually penetrated to generate a doubly interpenetrated framework, and then extended to its 3D architecture via the supramolecular forces between doubly interpenetrated 2D frameworks and free 4-dpds ligands by intermolecular O–H⋅⋅⋅N hydrogen bonding interaction. Crystal packing arrangements were characterized by fingerprint plots, which were derived from the Hirshfeld Surfaces analysis, and showed that intermolecular hydrogen bonding interactions are the most important interactions on the construction of the crystal 1. Full article
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Open AccessArticle
Switchable Lens Design for Multi-View 2D/3D Switching Display with Wide-Viewing Window
Crystals 2020, 10(5), 418; https://doi.org/10.3390/cryst10050418 - 24 May 2020
Viewed by 271
Abstract
We improved the three-dimensional (3D) crosstalk level of multi-view 3D displays using a lens array with small f-number, thereby facilitating a wide 3D viewing window. In particular, we designed a polarization-dependent-switching liquid crystal (LC)-based gradient refractive index (GRIN) lens array that could [...] Read more.
We improved the three-dimensional (3D) crosstalk level of multi-view 3D displays using a lens array with small f-number, thereby facilitating a wide 3D viewing window. In particular, we designed a polarization-dependent-switching liquid crystal (LC)-based gradient refractive index (GRIN) lens array that could be switched between 2D and 3D viewing modes. For the GRIN lens with a small f-number (1.08), we studied the effect of the interfacial curvature between the plano-concave isotropic polymer layer and the plano-convex birefringent LC layer on the aberration properties. We examined the conventional spherical, quadratic polynomial aspherical, and a high-order (fourth-order) polynomial aspherical curvature. For the high-order polynomial aspherical curvature, the achievable transverse spherical aberration (TSA = 10.2 µm) was considerably lower than that with the spherical (TSA = 100.3 µm) and quadratic polynomial aspherical (TSA = 30.4 µm) curvatures. Consequently, the angular luminance distributions for each view were sharper for the high-order polynomial interfacial curvature. We designed multi-view (43-view) 3D displays using the arrays of switchable LC lenses with different curvatures, and the average adjacent crosstalk levels within the entire viewing window (50°) were 68.5%, 73.3%, and 60.0% for the spherical, quadratic polynomial aspherical, and high-order polynomial aspherical curvatures, respectively. Full article
(This article belongs to the Special Issue Organic Optoelectronic Materials)
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Open AccessArticle
Exploring SiC Planar IGBTs towards Enhanced Conductivity Modulation Comparable to SiC Trench IGBTs
Crystals 2020, 10(5), 417; https://doi.org/10.3390/cryst10050417 - 23 May 2020
Viewed by 239
Abstract
The state-of-the-art silicon insulated-gate bipolar transistor (IGBT) features a trench gate, since it enhances the conductivity modulation. The SiC trench IGBT, however, faces the critical challenge of a high electric field in the gate oxide, which is a crucial threat to the device’s [...] Read more.
The state-of-the-art silicon insulated-gate bipolar transistor (IGBT) features a trench gate, since it enhances the conductivity modulation. The SiC trench IGBT, however, faces the critical challenge of a high electric field in the gate oxide, which is a crucial threat to the device’s reliability. In this work, we explore the possibility of using a SiC planar IGBT structure to approach high performance to the level of a SiC trench IGBT, without suffering the high gate oxide field. The proposed SiC planar IGBT features buried p-layers directly under the p-bodies, and thus can be formed using the same mask set. The region between the buried p-layer and the p-body is heavily doped with n-type dopants so that the conductivity modulation is improved. Comprehensive TCAD simulations have been carried out to verify this concept, and the simulation results show the new SiC planar IGBT exhibits a high performance comparable to the trench IGBT, and also exhibits a low gate oxide field. Full article
(This article belongs to the Special Issue Development and Investigation of SiC and SiC-based devices)
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Open AccessArticle
Hot Deformation Behavior and Microstructure Characterization of an Al-Cu-Li-Mg-Ag Alloy
Crystals 2020, 10(5), 416; https://doi.org/10.3390/cryst10050416 - 22 May 2020
Viewed by 234
Abstract
The flow behavior of an Al-Cu-Li-Mg-Ag alloy was studied by thermal simulation tests at deformation temperatures between 350 °C and 470 °C and strain rates between 0.01–10 s−1. The microstructures of the deformed materials were characterized by electron backscattered diffraction. Constitutive [...] Read more.
The flow behavior of an Al-Cu-Li-Mg-Ag alloy was studied by thermal simulation tests at deformation temperatures between 350 °C and 470 °C and strain rates between 0.01–10 s−1. The microstructures of the deformed materials were characterized by electron backscattered diffraction. Constitutive equations were developed after considering compensation for strains. The processing maps were established and the optimum processing window was identified. The experimental data and predicted values of flow stresses were in a good agreement with each other. The influence of deformation temperature and strain rates on the microstructure were discussed. The relationship between the recrystallization mechanism and the Zener–Hollomon parameter was investigated as well. Full article
(This article belongs to the Special Issue Microstructural and Mechanical Characterization of Alloys)
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Open AccessArticle
Narrow/Broad-Band Absorption Based on Water-Hybrid Metamaterial
Crystals 2020, 10(5), 415; https://doi.org/10.3390/cryst10050415 - 22 May 2020
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Abstract
In this work, the possibility of a switchable metamaterial absorber is proposed to control absorption bandwidth in the WiMAX/LTE (worldwide interoperability for microwave access/long term evolution) band, by taking advantage of the low cost and myriad structural configurations afforded by water-based metamaterials. By [...] Read more.
In this work, the possibility of a switchable metamaterial absorber is proposed to control absorption bandwidth in the WiMAX/LTE (worldwide interoperability for microwave access/long term evolution) band, by taking advantage of the low cost and myriad structural configurations afforded by water-based metamaterials. By exploiting truncated cone-type resonators, the fractional bandwidth of 27.6% of absorption spectrum can be adjusted flexibly to be 7.4% of the narrow-band absorption depending on the volume of injected water, in both simulation and experiment at room temperature. In particular, this control method can be applied stably for different temperature of injected water. We describe a dynamic mechanism for broadband MA, as well as a principle for controlling the absorption characteristics utilizing a combination of magnetic resonance and perfect impedance matching. These results are a stepping-stone towards the realization of smart electronics integrated with multi-functional metamaterials in military, biomedical, communication and other fields. Full article
(This article belongs to the Special Issue Metamaterials)
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Open AccessArticle
Synthesis of a Metal Oxide by Forming Solvate Eutectic Mixtures and Study of Their Synthetic Performance under Hyper- and Hypo-Eutectic Conditions
Crystals 2020, 10(5), 414; https://doi.org/10.3390/cryst10050414 - 21 May 2020
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Abstract
The synthesis of YBa2Cu3O7−x (YBCO or 123) superconductor was carried out under hyper- and hypo-eutectic conditions with different ammonium compounds, i.e., ammonium nitrate, formate, acetate, carbonate, bicarbonate, and tetramethylammonium nitrate. The aim was to find more affordable synthetic [...] Read more.
The synthesis of YBa2Cu3O7−x (YBCO or 123) superconductor was carried out under hyper- and hypo-eutectic conditions with different ammonium compounds, i.e., ammonium nitrate, formate, acetate, carbonate, bicarbonate, and tetramethylammonium nitrate. The aim was to find more affordable synthetic pathways using highly available and cheaper compounds, as well as to study the crystal formation under no-carbon conditions when ammonium nitrate was employed. Best results were obtained when eutectic conditions were achieved, namely by ammonium nitrate and YBaCu nitrates in a 5:1 molar ratio (81% of the superconductor). Ammonium formate, acetate, carbonate, and bicarbonate did not produce eutectic mixes. Temperature analysis of the reaction carried out by ammonium nitrate/YBaCu nitrates indicated the formation of barium carbonate, despite no carbon source being used in this reaction. This phenomenon is further discussed in this work. Consequently, tetramethylammonium nitrate, as a chelator and carbon source, was used, providing >96% of the superconductor. Full article
(This article belongs to the Section Inorganic Crystalline Materials)
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Open AccessArticle
Synthesis, Single Crystal X-Ray Structure, Hirshfeld Surface Analysis, DFT Computations, Docking Studies on Aurora Kinases and an Anticancer Property of 3-(2,3-Dihydrobenzo[b][1,4]dioxin-6-yl)-6-methoxy-4H-chromen-4-one
Crystals 2020, 10(5), 413; https://doi.org/10.3390/cryst10050413 - 20 May 2020
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Abstract
The isoflavone compound 3-(2,3-dihydrobenzo[b][1,4]dioxin-6-yl)-6-methoxy-4H-chromen-4-one (6) was prepared and structurally characterized using NMR, mass spectrum and X-ray crystallography. Compound 6, C18H14O5, was crystallized in the monoclinic space group P21/n with [...] Read more.
The isoflavone compound 3-(2,3-dihydrobenzo[b][1,4]dioxin-6-yl)-6-methoxy-4H-chromen-4-one (6) was prepared and structurally characterized using NMR, mass spectrum and X-ray crystallography. Compound 6, C18H14O5, was crystallized in the monoclinic space group P21/n with the cell parameters; a = 7.1869(4) Å, b = 10.2764(6) Å, c = 19.6771(10) Å, β = 99.442(2)°, V = 1433.57(14) Å3, Z = 4. In the title compound, the chromenone ring system is slightly twisted from planarity and the dihedral angle formed between the plane of the chromenone ring and benzene ring is 47.75°. Several intermolecular hydrogen bonds make the crystal stabilized in the three-dimensional structure, which was confirmed by Hirshfeld surface analysis. Density functional theory (DFT) calculations at the B3LYP/6-311++G(d,p) level were carried out and the calculated geometric parameters were compared with the experimental results. A frontier molecular orbital calculation was performed to reveal that the energy values of highest occupied molecular orbital (HOMO) and lowest un-occupied molecular orbital (LUMO) were −5.8223 eV and −1.8447 eV, and the HOMO–LUMO energy gap was 3.9783 eV. A clonogenic long-term survival assay of compound 6 against HCT116 human colon cancer cells showed an anti-cancer ability, with GI50 value of 24.9 μM. Docking experiments within the active sites of aurora kinase A and B were carried out to explain the anti-cancer property of compound 6. Full article
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Open AccessArticle
(Ti,Cr)C-Based Cermets with Varied Nicr Binder Content via Elemental SHS for Perspective Cutting Tools
Crystals 2020, 10(5), 412; https://doi.org/10.3390/cryst10050412 - 20 May 2020
Viewed by 231
Abstract
The effects of granulation of reactive mixtures Ti-Cr-C and Ti-Cr-C-Ni on the combustion temperature and velocity, as well as phase composition and mechanical properties (crushing ability) of combustion products, were studied. Granulation was associated with a 1.5-fold increase in combustion velocity, caused by [...] Read more.
The effects of granulation of reactive mixtures Ti-Cr-C and Ti-Cr-C-Ni on the combustion temperature and velocity, as well as phase composition and mechanical properties (crushing ability) of combustion products, were studied. Granulation was associated with a 1.5-fold increase in combustion velocity, caused by a nearly 10-fold increase in gas permeability. Secondary reactions between TiC, Cr7C3, and molten Ni led to the formation of (Ti,Cr)C FCC solid solution and Ni2.88Cr1.12 intermetallics. After the combustion of Ti-Cr-C-Ni mixtures, prolonged fluorescence was registered, suggesting the exothermic nature of secondary phase formation reactions. The introduction of the nickel binder decreased the content of Cr in the solid solution (Ti,Cr)C owing to the formation of the Ni2.88Cr1.12 phase. To prevent the Cr depletion from the carbide solid solution, Ni-20%Cr binder was added to the granulated 80%(Ti + C)/20%(3Cr + 2C) mixture. Combustion of granulated mixture yielded brittle porous sinter cake, which was easy to crush and mill, whereas the combustion products from the powdered mixtures were more ductile and harder to crush. Full article
(This article belongs to the Section Hybrid and Composite Crystalline Materials)
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Open AccessArticle
Atomic Force Microscopy Study of Discrete Dislocation Pile-ups at Grain Boundaries in Bi-Crystalline Micro-Pillars
Crystals 2020, 10(5), 411; https://doi.org/10.3390/cryst10050411 - 20 May 2020
Viewed by 246
Abstract
Compression tests at low strains were performed to theoretically analyze the effects of anisotropic elasticity, misorientation, grain boundary (GB) stiffness, interfacial dislocations, free surfaces, and critical force on dislocation pile-ups in micro-sized Face-Centered Cubic (FCC) Nickel (Ni) and α-Brass bi-crystals. The spatial [...] Read more.
Compression tests at low strains were performed to theoretically analyze the effects of anisotropic elasticity, misorientation, grain boundary (GB) stiffness, interfacial dislocations, free surfaces, and critical force on dislocation pile-ups in micro-sized Face-Centered Cubic (FCC) Nickel (Ni) and α -Brass bi-crystals. The spatial variations of slip heights due to localized slip bands terminating at GB were measured by Atomic Force Microscopy (AFM) to determine the Burgers vector distributions in the dislocation pile-ups. These distributions were then simulated by discrete pile-up micromechanical calculations in anisotropic bi-crystals consistent with the experimentally measured material parameters. The computations were based on the image decomposition method considering the effects of interphase GB and free surfaces in multilayered materials. For Ni and α -Brass, it was found that the best predicted step height spatial profiles were obtained considering anisotropic elasticity, free surface effects, a homogeneous external stress and a certain critical force in the material to equilibrate the dislocation pile-ups. Full article
(This article belongs to the Special Issue Crystal Plasticity at Micro- and Nano-scale Dimensions)
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Open AccessArticle
Magnetocaloric Effect, Magnetoresistance of Sc0.28Ti0.72Fe2, and Phase Diagrams of Sc0.28Ti0.72Fe2−xTx Alloys with T = Mn or Co
Crystals 2020, 10(5), 410; https://doi.org/10.3390/cryst10050410 - 20 May 2020
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Abstract
(Sc,Ti)Fe2 Laves phases present a relatively unique case of first-order ferro-ferromagnetic transition originating from an instability of the Fe moment. In addition to large magnetoelastic effects making them potential negative thermal expansion materials, here, we show that Sc0.28Ti0.72Fe [...] Read more.
(Sc,Ti)Fe2 Laves phases present a relatively unique case of first-order ferro-ferromagnetic transition originating from an instability of the Fe moment. In addition to large magnetoelastic effects making them potential negative thermal expansion materials, here, we show that Sc0.28Ti0.72Fe2 and related alloys also present sizable magnetocaloric and magnetoresistance effects. Both effects are found substantially larger at the ferro-ferromagnetic transition (Tt1) than near the Curie temperature TC, yet they remain limited in comparison to other classes of giant magnetocaloric materials. We suggest a strategy to improve these properties by bringing the transition at Tt1 close to TC, and test its possible realization by Co or Mn for Fe substitutions. The structural and magnetic phase diagrams of Sc0.28Ti0.72Fe2−xTx alloys with T = Mn or Co are explored. Substitutions for Fe by adjacent Mn or Co elements give rise to a breakdown of the long-range ferromagnetic order, as well as a swift disappearance of finite moment magnetism. Full article
(This article belongs to the Special Issue Magnetocalorics)
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Open AccessArticle
Carbothermal Reduction Nitridation of Fly Ash, Diatomite and Raw Illite: Formation of Nitride Powders with Different Morphology and Photoluminescence Properties
Crystals 2020, 10(5), 409; https://doi.org/10.3390/cryst10050409 - 20 May 2020
Viewed by 256
Abstract
Rare-earth-doped SiAlON and Si3N4 materials from aluminosilicate starting materials have been reported to show superior photoluminescence (PL) properties. Three different starting materials, including pulverized coal furnace fly ash, diatomite and raw illite, were used for synthesis of nitride materials. The [...] Read more.
Rare-earth-doped SiAlON and Si3N4 materials from aluminosilicate starting materials have been reported to show superior photoluminescence (PL) properties. Three different starting materials, including pulverized coal furnace fly ash, diatomite and raw illite, were used for synthesis of nitride materials. The phase and morphology evolution of these products were carefully monitored at the low temperature range of 1350 °C to 1450 °C by X-ray diffraction (XRD), scanning electronic microscopy (SEM) and Fourier-transform infrared spectroscopy (FT-IR). The PL properties of Eu-doped nitride products were also comparatively characterized. The results show that the type of starting material affects the phase composition and the photoluminescence properties of products. The existence of aluminum and alkali metals could effectively promote nitridation reactions. Aluminum in the starting materials led to the formation of different aluminum-rich nitride phases. Thus, β-SiAlON could be achieved at a much lower temperature (1350 °C) using raw illite or fly ash containing the proper amount of aluminum. Additionally, excess aluminum led to the formation of corundum and 15R-SiAlON. The products from pulverized coal furnace fly ash had more prismatic particles, and the products from diatomite had more fibrous particles. With the progress of the nitridation process, the fibers were increased, becoming longer and straighter, and the prismatic particles were more obvious. The presence of aluminum in the starting materials led to a blue shift in the photoluminescence spectrum. Full article
(This article belongs to the Section Crystalline Minerals and Biominerals)
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Open AccessArticle
Reduced Sintering Temperatures of Li+ Conductive Li1.3Al0.3Ti1.7(PO4)3 Ceramics
Crystals 2020, 10(5), 408; https://doi.org/10.3390/cryst10050408 - 20 May 2020
Viewed by 340
Abstract
All-solid-state batteries (ASSB) are considered promising candidates for future energy storage and advanced electric mobility. When compared to conventional Li-ion batteries, the substitution of Li-ion conductive, flammable liquids by a solid electrolyte and the application of Li-metal anodes substantially increase safety and energy [...] Read more.
All-solid-state batteries (ASSB) are considered promising candidates for future energy storage and advanced electric mobility. When compared to conventional Li-ion batteries, the substitution of Li-ion conductive, flammable liquids by a solid electrolyte and the application of Li-metal anodes substantially increase safety and energy density. The solid electrolyte Li1.3Al0.3Ti1.7(PO4)3 (LATP) provides high Li-ion conductivity of about 10−3 S/cm and is considered a highly promising candidate for both the solid electrolyte-separator and the ionically conductive part of the all-solid state composite cathode, consisting of the cathode material, the solid electrolyte, and an electron conductor. Co-sintering of the composite cathode is a sophisticated challenge, because temperatures above 1000 °C are typically required to achieve the maximum ionic conductivity of LATP but provoke reactions with the cathode material, inhibiting proper electrochemical functioning in the ASSB. In the present study, the application of sintering aids with different melting points and their impact on the sinterability and the conductivity of LATP were investigated by means of optical dilatometry and impedance spectroscopy. The microstructure of the samples was analyzed by SEM. The results indicate that the sintering temperature can be reduced below 800 °C while maintaining high ionic conductivity of up to 3.6 × 10−4 S/cm. These insights can be considered a crucial step forward towards enable LATP-based composite cathodes for future ASSB. Full article
(This article belongs to the Special Issue Conducting Ceramics)
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Open AccessArticle
Role of Potassium Substitution in the Magnetic Properties and Magnetocaloric Effect in La0.8−xKxBa0.05Sr0.15MnO3 (0 ≤ x ≤ 0.20)
Crystals 2020, 10(5), 407; https://doi.org/10.3390/cryst10050407 - 19 May 2020
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Abstract
The magnetic and magnetocaloric effects of potassium-substituted La0.8−xKxBa0.05Sr0.15MnO3 (0 ≤ x ≤ 0.20) manganite were explored. The samples in polycrystalline form were synthesized by the sol–gel method, with a final sintering temperature of [...] Read more.
The magnetic and magnetocaloric effects of potassium-substituted La0.8−xKxBa0.05Sr0.15MnO3 (0 ≤ x ≤ 0.20) manganite were explored. The samples in polycrystalline form were synthesized by the sol–gel method, with a final sintering temperature of 1100 °C. Powder X-ray diffraction (XRD) patterns refined by Rietveld refinement show that all samples crystallized in rhombohedral structure with R-3c space group. The unit cell volume of the samples decreases with increasing potassium concentration. In addition, small changes in average bond length and bond angle are also observed in the samples. Scanning electron microscope (SEM) images reveal that the largest average grain size was observed for x = 0.10. Field-cooled (FC) magnetization measurements show that the Curie temperature ( T C ) of the samples increases from 320 K for x = 0 to 360 K for x = 0.2. The largest magnetocaloric (MCE) effect, which is represented by maximum magnetic entropy change (− Δ S M ,   M A X ), reaches its greatest value for the x = 0.10 sample. The monotonous increase in T C suggests that TC is mainly governed by the ferromagnetic coupling between Mn ions induced by the changes on average bond length and bond angle. The obtained − Δ S M ,   M A X value suggests that MCE property is more sensitive to Zener theory of double exchange, which is strongly related to the Mn3+/Mn4+ ratio of the samples. Full article
(This article belongs to the Special Issue Magnetocalorics)
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Open AccessArticle
Experimental and Theoretical Studies of Carboxylic Polymers with Low Molecular Weight as Inhibitors for Calcium Carbonate Scale
Crystals 2020, 10(5), 406; https://doi.org/10.3390/cryst10050406 - 19 May 2020
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Abstract
Poly acrylic acid (PAA) and polyepoxysuccinic acid (PESA) were investigated as scale inhibitors. The static experiments certified that PAA was superior to PESA for the inhibition of calcium carbonate in the low molecular weight range. The X-ray diffraction patterns suggest that the effect [...] Read more.
Poly acrylic acid (PAA) and polyepoxysuccinic acid (PESA) were investigated as scale inhibitors. The static experiments certified that PAA was superior to PESA for the inhibition of calcium carbonate in the low molecular weight range. The X-ray diffraction patterns suggest that the effect of PAA on the calcite (1 0 4) and (1 1 0) crystal plane was more obvious. Scanning electron microscopy was used to study the surface morphology of the depositions, which indicated that the addition of scale inhibitors could disturb the normal growth of CaCO3 scale. The transmittance ratio of ferric oxide demonstrated that PAA had a better dispersion performance than PESA. The molecular dynamics simulation and quantum calculation were selected to theoretically explore the mechanism and structure of scale inhibitors, indicating that the interaction of PAA with (1 0 4) and (1 1 0) calcite crystal surfaces was stronger than PESA. In addition, the results indicated that the PAA with negative charge more easily adsorbed free Ca2+ in the aqueous phase. Based on these observations, PAA exhibited better scale inhibition and dispersion effects than PESA in the case of low molecular weight. Full article
(This article belongs to the Special Issue Carbonates Volume II)
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Open AccessReview
Unseeded Crystal Growth of (100)-Oriented Grain-Boundary-Free Si Thin-Film by a Single Scan of the CW-Laser Lateral Crystallization of a-Si on Insulator
Crystals 2020, 10(5), 405; https://doi.org/10.3390/cryst10050405 - 17 May 2020
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Abstract
Laser crystallization of a-Si film on insulating substrate is a promising technology to fabricate three-dimensional integrations (3D ICs), flat panel displays (FPDs), or flexible electronics, because the crystallization can be performed on room temperature substrate to avoid damage to the underlying devices or [...] Read more.
Laser crystallization of a-Si film on insulating substrate is a promising technology to fabricate three-dimensional integrations (3D ICs), flat panel displays (FPDs), or flexible electronics, because the crystallization can be performed on room temperature substrate to avoid damage to the underlying devices or supporting plane. Orientation-controlled grain-boundary-free films are required to improve the uniformity in electrical characteristics of field-effect-transistors (FETs)fabricated in those films. This paper describes the recently found simple method to obtain {100}-oriented grain-boundary-free Si thin-films stably, by using a single scan of continuous-wave (CW)-laser lateral crystallization of a-Si with a highly top-flat line beam with 532 nm wavelength at room temperature in air. It was difficult to control crystal orientations in the grain-boundary-free film crystallized by the artificial modulation of solid-liquid interface, and any other trial to obtain preferential surface orientation with multiple irradiations resulted in grain boundaries. The self-organized growth of the {100}-oriented grain-boundary-free films were realized by satisfying the following conditions: (1) highly uniform top-flat line beam, (2) SiO2 cap, (3) low laser power density in the vicinity of the lateral growth threshold, and (4) single scan crystallization. Higher scan velocity makes the process window wide for the {100}-oriented grain-boundary-free film. This crystallization is very simple, because it is performed by a single unseeded scan with a line beam at room temperature substrate in air. Full article
(This article belongs to the Special Issue Growth and Evaluation of Crystalline Silicon (Volume II))
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Open AccessReview
Quarter of a Century after: A Glimpse at the Conformation and Mechanism of Candida antarctica Lipase B
Crystals 2020, 10(5), 404; https://doi.org/10.3390/cryst10050404 - 16 May 2020
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Abstract
Lipase B from Candida antarctica (CAL-B) belongs to the family of α/β-hydrolases, and is one from the most extensively used biocatalysts in the kinetic resolution of amines and alcohols in a racemic state, in the desymmetrization of diacetates or diols, and in the [...] Read more.
Lipase B from Candida antarctica (CAL-B) belongs to the family of α/β-hydrolases, and is one from the most extensively used biocatalysts in the kinetic resolution of amines and alcohols in a racemic state, in the desymmetrization of diacetates or diols, and in the stereoselective synthesis of chiral intermediate compounds for obtaining the various pharmaceuticals and agents which protect plants. There are also many cases of promiscuous reactions catalyzed by CAL-B. The number of very important results appeared recently in the literature in the years 2015–2019, regarding the crystal structure and conformation of CAL-B molecule. Before 2015, there was a long period of a complete lack of information concerning this enzyme’s structure. The earlier reports about CAL-B structure were dated between 1994–1995, and did not provide enough conclusions about the mechanism of the enzyme. The recently solved structures give a hint of the enzyme mechanism in three dimensions. Full article
(This article belongs to the Section Biomolecular Crystals)
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Open AccessArticle
Mathematical Modeling and Analysis of Tribological Properties of AA6063 Aluminum Alloy Reinforced with Fly Ash by Using Response Surface Methodology
Crystals 2020, 10(5), 403; https://doi.org/10.3390/cryst10050403 - 16 May 2020
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Abstract
Lightweight, high-strength metal matrix composites have attracted considerable interest because of their attractive physical, mechanical and tribological properties. Moreover, they may offer distinct advantages due to good strength and wear resistance. In this research, AA6063 was reinforced with FA particles using compocasting methods. [...] Read more.
Lightweight, high-strength metal matrix composites have attracted considerable interest because of their attractive physical, mechanical and tribological properties. Moreover, they may offer distinct advantages due to good strength and wear resistance. In this research, AA6063 was reinforced with FA particles using compocasting methods. The effects of fly ash content, load, sliding speed and performance tribology of AA6063 –FA composite were evaluated. Dry sliding wear tests were carried out according to experimental design using the pin-on-disc method with three different loads (24.5, 49 and 73.5 N) and three speeds (150, 200 and 250 rpm) at room temperature. Response surface methodology (RSM) was used to analyze the influence of the process parameters on the tribological behavior of the composites. The surface plot showed that the wear rate increased with increasing load, time and sliding velocity. In contrast, the friction coefficient decreased with increasing these parameters. Optimal models for wear rate and friction coefficient showed appropriate results that can be estimated, hence reducing wear testing time and cost. Full article
(This article belongs to the Special Issue Microstructural and Mechanical Characterization of Alloys)
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Open AccessArticle
Investigation of Total Phenolic Content and Antioxidant Activities of Spruce Bark Extracts Isolated by Deep Eutectic Solvents
Crystals 2020, 10(5), 402; https://doi.org/10.3390/cryst10050402 - 16 May 2020
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Abstract
Extracts from spruce bark obtained using different deep eutectic solvents were screened for their total phenolic content (TPC) and antioxidant activities. Water containing choline chloride-based deep eutectic solvents (DESs) with lactic acid and 1,3-propanediol, 1,3-butanediol, 1,4-butanediol, and 1,5-pentanediol, with different molar ratios, were [...] Read more.
Extracts from spruce bark obtained using different deep eutectic solvents were screened for their total phenolic content (TPC) and antioxidant activities. Water containing choline chloride-based deep eutectic solvents (DESs) with lactic acid and 1,3-propanediol, 1,3-butanediol, 1,4-butanediol, and 1,5-pentanediol, with different molar ratios, were used as extractants. Basic characteristics of the DESs (density, viscosity, conductivity, and refractive index) were determined. All the DESs used behave as Newtonian liquids. The extractions were performed for 2 h at 60 °C under continuous stirring. TPC was determined spectrophotometrically, using the Folin-Ciocalteu reagent, and expressed as gallic acid equivalent (GAE). The antioxidant activity was determined spectrophotometrically by 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging assay. The TPC varied from 233.6 to 596.2 mg GAE/100 g dry bark; radical scavenging activity (RSA) ranged between 81.4% and 95%. This study demonstrated that deep eutectic solvents are suitable solvents for extracting phenolic compounds from spruce bark. Full article
(This article belongs to the Special Issue Eutectic Solvents)
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Open AccessArticle
Effect of Cholesterol and Ibuprofen on DMPC-β-Aescin Bicelles: A Temperature-Dependent Wide-Angle X-ray Scattering Study
Crystals 2020, 10(5), 401; https://doi.org/10.3390/cryst10050401 - 16 May 2020
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Abstract
β-aescin is a versatile biosurfactant extracted from the seeds of the horse chestnut tree Aesculus hippocastanum with anti-cancer potential and is commonly used in the food and pharmaceutical and cosmetic industries. In this article, wide-angle X-ray scattering (WAXS) is used in order [...] Read more.
β -aescin is a versatile biosurfactant extracted from the seeds of the horse chestnut tree Aesculus hippocastanum with anti-cancer potential and is commonly used in the food and pharmaceutical and cosmetic industries. In this article, wide-angle X-ray scattering (WAXS) is used in order to study the modifications of the structural parameters at the molecular scale of lipid bilayers in the form of bicelles composed of 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) and the triterpenoid saponin β -aescin. In particular, the impact on the cooperative phase transition and the structural parameters of the DMPC bilayers at different compositions and temperatures is of special interest. Moreover, we show how cholesterol and the non-steroidal anti-inflammatory drug (NSAID) ibuprofen modulate the structural parameters of the β -aescin-DMPC assemblies on a molecular scale. Ibuprofen and cholesterol interact with different parts of the bilayer, namely the head-region in the former and the tail-region in the latter case allowing for specific molecular packing and phase formation in the binary and ternary mixtures. Full article
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Open AccessArticle
Enhanced Photocatalytic and Antibacterial Activities of K2Ti6O13 Nanowires Induced by Copper Doping
Crystals 2020, 10(5), 400; https://doi.org/10.3390/cryst10050400 - 15 May 2020
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Abstract
Cu-doped K2Ti6O13 (Cu–KTO) nanowires were prepared using a combination of sol–gel and hydrothermal methods to improve the photocatalytic and antibacterial performance of K2Ti6O13 (KTO) nanowires. The Cu–KTO nanowires maintained the monoclinic structure of [...] Read more.
Cu-doped K2Ti6O13 (Cu–KTO) nanowires were prepared using a combination of sol–gel and hydrothermal methods to improve the photocatalytic and antibacterial performance of K2Ti6O13 (KTO) nanowires. The Cu–KTO nanowires maintained the monoclinic structure of KTO. The Cu2+ ions could enter into the lattice of KTO by substituting for certain Ti4+ ions and cause the formation of defects and oxygen vacancies. The UV–Visible absorption spectra showed that after Cu doping, the absorption edge of KTO moved to the visible region, indicating that the band gap decreased and the ability to absorb visible light was acquired. The photocatalytic properties of the Cu–KTO nanowires with different doping amounts were assessed by simulating the photodegradation of rhodamine B (RhB) under simulated sunlight irradiation. The 1.0 mol% Cu–KTO nanowires showed the best photocatalytic performance, and 91% of RhB was decomposed by these nanowires (the catalyst dose was only 0.3 g/L) within 5 h. The performance of the Cu–KTO nanowires was much better than that of the KTO nanowires. The Cu–KTO nanowires also showed high antibacterial activity for Escherichia coli (ATCC 25922) of up to 99.9%, which was higher than that of the pure KTO samples. Results proved that Cu doping is an effective means to develop multifunctional KTO nanomaterials. It can be used to degrade organic pollutants and remove harmful bacteria simultaneously in water environments. Full article
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Open AccessArticle
Effect of the Zr-Substitution on the Structural and Electrical Properties of LaFeO3: XRD, Raman Scattering, SEM, and Impedance Spectroscopy Study
Crystals 2020, 10(5), 399; https://doi.org/10.3390/cryst10050399 - 15 May 2020
Viewed by 259
Abstract
The LaFe1−xZrxO3 (x = 0.01, 0.05) ceramics were prepared by sol-gel and annealing method and studied by XRD, Raman scattering analysis, SEM, and impedance spectroscopy method. The crystal structure and phonon characteristics analysis revealed that the crystal structure [...] Read more.
The LaFe1−xZrxO3 (x = 0.01, 0.05) ceramics were prepared by sol-gel and annealing method and studied by XRD, Raman scattering analysis, SEM, and impedance spectroscopy method. The crystal structure and phonon characteristics analysis revealed that the crystal structure tends to preserve its ideal orthorhombic structure, following the increase in driving force of the Fe/ZrO6 octahedral tilting. The frequency-dependent dielectric parameters at each temperature decreased with increasing Zr content. The temperature dependence dielectric relaxation and dc conduction mechanism satisfied the Arrhenius law and increased with increasing Zr content. The activation energy ranged from 0.30 to 0.50 eV and was similar in the relaxation and conduction mechanisms, indicating that both transport mechanisms were based on a similar mechanism. Full article
(This article belongs to the Special Issue Sol-Gel Method Applied to Crystalline Materials)
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Open AccessArticle
The Effect of Printing Parameters on Electrical Conductivity and Mechanical Properties of PLA and ABS Based Carbon Composites in Additive Manufacturing of Upper Limb Prosthetics
Crystals 2020, 10(5), 398; https://doi.org/10.3390/cryst10050398 - 15 May 2020
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Abstract
Additive manufacturing technologies are dynamically developing, strongly affecting almost all fields of industry and medicine. The appearance of electrically conductive polymers has had a great impact on the prototyping process of different electrical components in the case of upper limb prosthetic development. The [...] Read more.
Additive manufacturing technologies are dynamically developing, strongly affecting almost all fields of industry and medicine. The appearance of electrically conductive polymers has had a great impact on the prototyping process of different electrical components in the case of upper limb prosthetic development. The widely used FFF 3D printing technology mainly uses PLA (polylactic acid) and ABS (acrylonitrile butadiene styrene) based composites, and despite their presence in the field, a detailed, critical characterization and comparison of them has not been performed yet. Our aim was to characterize two PLA and ABS based carbon composites in terms of electrical and mechanical behavior, and extend the observations with a structural and signal transfer analysis. The measurements were carried out by changing the different printing parameters, including layer resolution, printing orientation and infill density. To determine the mechanical properties, static and dynamic tests were conducted. The electrical characterization was done by measuring the resistance and signal transfer characteristics. Scanning electron microscopy was used for the structural analysis. The results proved that the printing parameters had a significant effect on the mechanical and electrical characteristics of both materials. As a major novelty, it was concluded that the ABS carbon composite has more favorable behavior in the case of additive manufacturing of electrical components of upper limb prosthetics, and they can be used as moving, rotating parts as well. Full article
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Open AccessArticle
Structural, Hirshfeld Surface Analysis, Morphological Approach, and Spectroscopic Study of New Hybrid Iodobismuthate Containing Tetranuclear 0D Cluster Bi4I16·4(C6H9N2) 2(H2O)
Crystals 2020, 10(5), 397; https://doi.org/10.3390/cryst10050397 - 15 May 2020
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Abstract
The Bi4I16·4(C6H9N2) 2(H2O) compound was synthesized by slow evaporation at room temperature. It exhibits a zero-dimensional (0D) tetrameric structure, comprising [Bi4I16]4− distorted octahedra, with strong I⋯I [...] Read more.
The Bi4I16·4(C6H9N2) 2(H2O) compound was synthesized by slow evaporation at room temperature. It exhibits a zero-dimensional (0D) tetrameric structure, comprising [Bi4I16]4− distorted octahedra, with strong I⋯I interactions among adjacent anionic clusters. We used Hirshfeld surface analysis to discuss the strength of hydrogen bonds and to quantify the inter-contacts (two-dimensional (2D) fingerprint plots). It revealed that the hydrogen bonding interactions H⋯I (56.3%), π–π stacking (11.7%), and I⋯I interactions (5.9%) play the major role in the stability of the crystal structure. The crystal morphology was simulated using Bravais–Friedel, Donnay–Harker (BFDH) and growth morphology (GM) methods. The experimental habit of the title compound was adequately reproduced by the two models. The calculated results show that the crystal morphology of the title compound in a vacuum is dominated by five facets: (020), (011), (110), (10−1), and (11−1). The (020) facet is the largest among all the facets calculated. Projection of the facet showed that there are a few polar groups on the (020) facet. In the 50–400 and 400–4000 cm−1 frequency regions, we measured the Raman and infrared spectra, respectively, of the title compound, and we assigned the observed vibration modes. Full article
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Open AccessArticle
Luminescence Behavior of GdVO4: Tb Nanocrystals in Silica Glass-Ceramics
Crystals 2020, 10(5), 396; https://doi.org/10.3390/cryst10050396 - 15 May 2020
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Abstract
Glass ceramics with GdVO4: Tb nanocrystals impregnated in the highly transparent silica glass were prepared by the porous glass and sintering process and confirmed by XRD, Raman spectrum, and TEM. Spectral analysis shows that there are multifarious energy transfer processes in [...] Read more.
Glass ceramics with GdVO4: Tb nanocrystals impregnated in the highly transparent silica glass were prepared by the porous glass and sintering process and confirmed by XRD, Raman spectrum, and TEM. Spectral analysis shows that there are multifarious energy transfer processes in GdVO4: Tb nanocrystals, such as VO43− → Tb3+, Gd3+ → VO43−, Gd3+ → VO43− → Tb3+, and Gd3+ → Tb3+, and the main one is VO43− → Tb3+. In this process, 3T1,21A1 transition of VO43− transfers the energy to Tb3+ and generates 5D37F6,5,4,3,2 and 5D47F5 transitions of Tb3+. The energy transfer efficiency is 29.5%, and the excitation wavelength range of Tb3+ ions can be shifted from 230–260 nm to 280–365 nm. This shows that GdVO4 can effectively change the excitation wavelength of Tb3+, which is conducive to the application of Tb3+ ions excited by LED light sources. Full article
(This article belongs to the Special Issue Transparent Glass Ceramics)
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Open AccessArticle
Characterization of Silver Nanoparticles Obtained by a Green Route and Their Evaluation in the Bacterium of Pseudomonas aeruginosa
Crystals 2020, 10(5), 395; https://doi.org/10.3390/cryst10050395 - 15 May 2020
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Abstract
Metal nanoparticles are widely used in different areas such as biotechnology and biomedicine, for example in drug delivery, imaging and control of bacterial growth. The antimicrobial effect of silver has been identified as an alternative approach to the increasing bacterial resistance to antibiotics. [...] Read more.
Metal nanoparticles are widely used in different areas such as biotechnology and biomedicine, for example in drug delivery, imaging and control of bacterial growth. The antimicrobial effect of silver has been identified as an alternative approach to the increasing bacterial resistance to antibiotics. Silver nanoparticles were synthesized by the green route using the Geranium extract as a reducing agent. The characterization was carried out by the techniques of UV-Vis spectrophotometry, transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), X-ray emitted photoelectron spectroscopy (XPS) and X-ray diffraction. Nanoparticle diameters between 15 and 50 nm were obtained and the interplanar spaces calculated from the electron diffraction pattern corresponding to a mixture of silver with 4H and FCC structures. To determine the minimum inhibitory concentration of silver nanoparticles (AgNPs) on the Pseudomonas aeruginosa bacteria (ATCC-27853), different concentrations of colloidal solution 0.36, 0.18, 0.09 and 0.05 μg/mL were evaluated as a function of the incubation time, measuring the inhibition halo and colony forming unit (CFU) during 0, 2 and 4 h of incubation. The minimum inhibitory AgNPs concentration (MIC) is 0.36 μg/mL at 0 h while the concentration of 0.18 μg/mL presents a total inhibition of the bacterium after 2 h. For the rest of the dilutions, gradual inhibitions as a function of time were observed. We evaluate the antibacterial effect of silver nanoparticles obtained by a green methodology in Pseudomonas aeruginosa bacteria. Finally, the colloidal nanoparticle solution can be an antibacterial alternative for different biomedical approaches. Full article
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Open AccessArticle
Systematic Investigations on Continuous Fluidized Bed Crystallization for Chiral Separation
Crystals 2020, 10(5), 394; https://doi.org/10.3390/cryst10050394 - 14 May 2020
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Abstract
A recently developed continuous enantioseparation process utilizing two coupled fluidized bed crystallizers is systematically investigated to identify essential correlations between different operation parameters and the corresponding process performance on the example of asparagine monohydrate. Based on liquid phase composition and product crystal size [...] Read more.
A recently developed continuous enantioseparation process utilizing two coupled fluidized bed crystallizers is systematically investigated to identify essential correlations between different operation parameters and the corresponding process performance on the example of asparagine monohydrate. Based on liquid phase composition and product crystal size distribution data, it is proven that steady state operation is achieved reproducibly in a relatively short time. The process outputs at steady state are compared for different feed flow rates, supersaturations, and crystallization temperatures. It is shown that purities >97% are achieved with productivities up to 40 g/L/h. The size distribution, which depends almost exclusively on the liquid flow rate, can be easily adjusted between 260 and 330 µm (mean size) with an almost constant standard deviation of ±55 µm. Full article
(This article belongs to the Special Issue Advances in Industrial Crystallization)
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Open AccessArticle
Interactions on the Interface between Two Liquid Crystal Materials
Crystals 2020, 10(5), 393; https://doi.org/10.3390/cryst10050393 - 14 May 2020
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Abstract
In liquid crystal applications, boundary conditions are essential to ensuring suitable bulk molecular orientation and a deterministic response to external fields. Be it confinement to a droplet or a shell, a glass plate, or an interface with air or another liquid, proper surface [...] Read more.
In liquid crystal applications, boundary conditions are essential to ensuring suitable bulk molecular orientation and a deterministic response to external fields. Be it confinement to a droplet or a shell, a glass plate, or an interface with air or another liquid, proper surface alignment must be ensured—mechanically by rubbing, by chemical treatment that adds a layer of aligning molecules, by using photoalignment or even by leaving the surface untreated, using the intrinsic properties of the substrate itself. The anchoring can be classified as unidirectional (perpendicular homeotropic, or at oblique angles), or degenerate (planar or pre-tilted). However, if both substances at the interface are anisotropic, more diverse behaviour is expected. Here, we present a numerical simulation of a nematic droplet in a nematic host, and investigate behaviour of the director field and defects at the interface for different interfacial couplings. Finally, we compare the simulations to experimental images of discotic droplets in a calamitic nematic host. Full article
(This article belongs to the Special Issue Early Career Stars of the Decade)
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Open AccessArticle
Microstructure and Mechanical Properties of an Austenitic CrMnNiMoN Spring Steel Strip with a Reduced Ni Content
Crystals 2020, 10(5), 392; https://doi.org/10.3390/cryst10050392 - 12 May 2020
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Abstract
The article presents the mechanical properties of the austenitic stainless steel X5CrMnNiMoN16-4-4 after deformation by cold rolling and subsequent short-term tempering (deformation and partitioning (D&P) treatment). Tensile strengths of 1700–900 MPa and beyond were achieved both after work hardening and in the D&P-treated [...] Read more.
The article presents the mechanical properties of the austenitic stainless steel X5CrMnNiMoN16-4-4 after deformation by cold rolling and subsequent short-term tempering (deformation and partitioning (D&P) treatment). Tensile strengths of 1700–900 MPa and beyond were achieved both after work hardening and in the D&P-treated strip. The initial state of austenite in terms of grain size and pre-strengthening, as well as the selected cold rolling temperature significantly influenced the deformation-induced formation of α’ martensite and thus the flow and hardening behavior of the steel. The usage of two different rolling temperature regimes showed that the strength properties in the cold strip can be specifically adjusted. Lower deformation-induced martensite fractions enabled a larger thickness reduction of the strip without increasing the rolling force, while high deformation-induced martensite fractions led to strong hardening at low deformation levels. The D&P-treatment permits the strength of the cold-rolled strip with a predominantly austenitic microstructure to be increased to the required level. The total elongation of such a D&P strip was well over 2%. The D&P treatment of the spring steel strip is a cost-effective alternative to conventional tempering treatment. Full article
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