Soret effect is temperature-gradient-driven mass diffusion in a multicomponent system. This paper reviews the recent progress of understanding the Soret effect in glass-forming oxide melts. A new model, called adjusted Kempers model, is proposed to quantitatively predict Soret coefficients in binary glass-forming oxide melts. The model is verified by experiment and molecular dynamics simulation. In a 11Na2O–89B2O3 (mol %) melt, the difference of the Soret coefficient of Na2O between experiment and theory is 19%. In the nonequilibrium molecular dynamics simulation of CaO–SiO2 glass melts, the Soret coefficient of SiO2 is decreased with SiO2 content and a sign change is observed, which is consistent with the adjusted Kempers model. These results indicate that the adjusted Kempers model is promising. Additionally, this paper reviews the laser-induced Soret effect in multicomponent glasses.
Mechanochemical (MC) process is one of the most effective methods to produce amorphous and cation disordered electrode active materials. We individually synthesized amorphous and cation disordered cubic rocksalt Na2TiS3 by controlling the preparation conditions of the MC process. Cubic rocksalt Na2TiS3 and ordered monoclinic Na2TiS3 were also obtained via the heat treatment of amorphous Na2TiS3. The all-solid-state cell with cubic rocksalt Na2TiS3 showed a high reversible capacity of 270 mAh g−1, which corresponds to the theoretical capacity of Na2TiS3. The cell maintained the capacity for more than 30 cycles, indicating that the active materials can endure long operation life. The MC methods for transition metal sulfides and the search for ordered monoclinic polymorphs are necessary for the pursuit of novel electrode materials.
Drastically higher conductivity was found in the amorphous lithium-ion conducting nitride relative to the crystal. The amorphous Li2CN2 prepared by a mechanochemical process has the conductivity of 1.1 × 10−6 S cm−1 at 25°C, which is more than 1000 times higher than that of the crystalline form. The nitride has a better deformability compared to Li3BO3 oxide glass.
Single-crystal rods of Li7−xLa3Zr2−xTaxO12 (X = 0.2, 0.4, 0.5, 0.6, 0.8) were grown by floating zone melting. The typical size of the single-crystal rod was 8 mm in diameter and 70 mm in length. Li7−xLa3Zr2−xTaxO12 (X = 0.2, 0.4, 0.5, 0.6, 0.8) crystallizes in a cubic structure with an Ia-3d space group. Single crystal structure analysis was performed for all single crystals. How the lithium ion conductivity varies with the substitution amount of tantalum was investigated using a single crystal. Analyzing the results of AC impedance measurements, we estimated the total Li-ion conductivity of member in Li7−xLa3Zr2−xTaxO12 single-crystal. As a result, when X = 0.4, the lithium ion conductivity became the maximum, and it was 1.10 × 10 −3 S cm−1 at 298 K. The activation energy ticked up with increasing tantalum substitution.
The compressive properties of chemical vapor deposited zinc sulfide are studied up to 1050°C for the first time. The specimen with columns parallel to the compression direction fails by shear firstly and then the part below the slip plane is split. The fracture mode changes from intergranular to transgranular as temperature increases. During compression, the load firstly increases rapidly, then decreases gradually, and lastly drops sharply as displacement increases. The compressive strength decreases as temperature increases. Above 800°C, recrystallization is driven by diffusional processes, which leads to the reduction in compressive strength because of the grown grains and the increase in strain softening as holding time increases. At higher temperatures, diffusional processes are joined by plastic deformation which leads to strain hardening and results in the increase in compressive strength with holding time. This plastic deformation mechanism during recrystallization is observed directly from the load-displacement curve by the high-temperature in-situ compression test for the first time.
Ordered mesoporous silica SBA-15 with homogeneously dispersed platinum nanoparticles (PtNPs) was prepared via a sol–gel process. The PtNP content in the SBA-15 support as a result of this procedure was estimated to be up to 0.029 wt % using inductively coupled plasma analysis. Small-angle X-ray scattering measurements revealed that SBA-15 with PtNPs possessed regular pores with a two-dimensional hexagonal structure and p6mm symmetry. Nitrogen adsorption/desorption measurements for SBA-15 revealed an average pore size of 5.8 nm and a Brunauer–Emmett–Teller surface area as high as 1034 m2/g; this pore size is comparable to those of SBA-15 prepared using the conventional immersion method while the specific surface area is higher. Transmission electron microscopy with energy dispersive X-ray spectrometry revealed that the PtNPs were dispersed in the as-prepared SBA-15 interpore. These results indicate that this method is a new route for preparing SBA-15 with PtNPs that suppresses aggregation between the PtNPs.
Absorption edge energy has been studied in Bi2O3–B2O3, and (Li2O, Na2O, K2O, CaO, BaO, ZnO, Ga2O3 and Nb2O5)–Bi2O3–B2O3 glasses containing a large amount of Bi2O3. It was found that the absorption edge energy obeyed Duffy’s theoretical basicity formula, that is, the additivity rule with glass composition. The additivity factor depended on electronegativity of each constituent atom, except bismuth. The additivity factor of Bi2O3 was much smaller than that expected from electronegativity. The small value of additivity factor of Bi2O3 was discussed on the basis of Bi–O–Bi bond formation.
Nano-scale rod arrays of titania were prepared on commercially available pure titanium (cpTi) substrates by a chemical treatment at 80°C for 3 d and a subsequent aging treatment in ultra-pure water at 80°C for 1 d. Treating solutions (TSs) for chemical treatment contained titanyl sulfate (TiOSO4), hydrogen peroxide (H2O2), and nitric acid (HNO3). Fourier transform infrared spectroscopy analysis indicated that an amorphous titania gel layer containing Ti–O–O bonds formed on the chemically treated cpTi substrate in 0.10 mol·m−3 TS, which was then transformed into anatase rods during aging treatment. Thin-film X-ray diffraction and scanning-electron microscopy analyses showed that the 0.10 mol·m−3 TiOSO4 TS provided randomly packed aggregates of oriented anatase and rutile rods, while 0.14 and 0.18 mol·m−3 TiOSO4 TSs yielded highly ordered rutile rods of ca. 20 nm in diameter. The rutile rods grew perpendicular to the cpTi substrate and the rod array fully covered the surface of the cpTi substrate. It is proposed that the nucleation of rutile occurs on the amorphous titania gel layer, and the rate of nucleation and growth of rutile increase with increasing concentration of TS, accompanied by the consumption of amorphous titania gel. Rutile layers with high rod density and 3.0 µm thickness were successfully prepared on the surface of cpTi substrates.
In this study, aeolian-sand powder was used for replacing cement-based gelling material in order to prepare aeolian-sand powder concrete in C25 and C35 strength grades. Through relative dynamic elastic modulus and carbonization depth changes, the deterioration laws of the aeolian-sand powder concrete under the coupling effects of freeze-thaw + carbonization and carbonization + freeze-thaw were studied. Then, field emission scanning electron microscopy, X-ray diffraction, and nuclear magnetic resonance porosity measurement technology were applied to analyze the microstructure, hydration products, and porosity changes. The results show that the Carbonation Mechanism of aeolian sand powder concrete is different from that of ordinary concrete. The carbonation of ordinary concrete results in calcium carbonate, and the carbonation of aeolian sand powder concrete results in calcium sulfate and calcium carbonate; The decrease of relative dynamic elastic modulus of aeolian sand powder concrete under freeze-thaw and carbonation environment is lower than that of ordinary concrete, and the results indicated that the relative dynamic elastic modulus of the aeolian-sand powder concrete under the freeze-thaw + carbonization effects was higher than that under the carbonization + freeze-thaw effects by 1.5 times. Also, the carbonization depth was less than that under the carbonization + freeze-thaw effects by 5.0%. Under the freeze-thaw + carbonization effects, the internal harmless pores of the aeolian-sand powder concrete were higher than carbonation + freeze-thaw by 16.85%, higher than those of the ordinary concrete by 15.35%, the multi-harm pores were observed to be less than that of carbonization + freeze-thaw by 22.5%, which is lower than that of ordinary concrete by 22.25%. At the same time, the irreducible fluid saturation and permeability of aeolian sand powder concrete are 0.34 and 1.5% higher than those of ordinary concrete under the action of carbonization and freeze-thaw, thus the deterioration of aeolian sand powder concrete is significantly lower than that of ordinary concrete, while that of aeolian sand powder concrete under the action of carbonization and freeze-thaw is significantly higher.
A series of TiSiN coatings were deposited on the surface of Ti(C,N) based cermets by multi-arc ion plating technique with different substrate negative bias. The microstructure, composition and mechanical properties of the coatings were studied. The results showed that the TiSiN coating showed a typical columnar growth, and composed of TiN, amorphous Si3N4 and a few TiSi2 phases. There was an element diffusion at the interface between the substrate, transition layer and coating, which resulted in a relatively smaller compressive residual stress in the coating and relatively higher adhesion of the coating on substrate. For the coating with the substrate negative bias of −200 V, it had a relatively higher hardness, adhesion strength and wear resistance, and the wear mechanisms were adhesive and oxidative wear.
Effect of processing conditions on the crystallinity and luminescent characteristics of aeschynite-type Dy3+- and Eu3+-doped GdTiNbO6 formed under hydrothermal conditions from precursor solutions of inorganic salts, i.e. Dy(NO3)3, EuCl3, GdCl3, TiOSO4, and NbCl5 was investigated. A processing condition using the hydrolysis of urea promoted the formation of aeschynite with finer crystallite due to an increase in nucleation number. The aeschynite-type solid solution was directly formed under hydrothermal conditions at 240°C because its lattice parameters changed according to the Vegard’s Law. The photoluminescence (PL) emission intensity of aeschynite crystals depended on their crystallinity, which was closely related to their processing conditions. Without subsequent heat treatment in air, the as-prepared aeschynite-type solid solutions substitutionally doped with 5 mol % Dy3+ and 50 mol % Eu3+ showed the maximum and intense PL emissions under direct excitation of dopant ions. In the case of indirect excitation using energy transfer from the host absorption band at 280 nm, the characteristic blue and yellow PL emission intensities involved in the broad host emission of the Dy3+-doped GdTiNbO6 were improved dramatically after heating at 1300°C in air.
Microwave heating is often used to fabricate silicon carbide (SiC) from mixtures of silicon and carbon powders. Mixing these reactant powders has been considered important because the carbonization of silicon has long been regarded as a solid-state reaction occurring via atomic diffusion among powders. Here, we present a facile alternative approach to microwave-heating synthesis of SiC from silicon powder which was simply embedded in graphite powder without mixing with the graphite powder. 10-min microwave heating in air turned the silicon powder into a consolidated chunk of almost fully carbonized β-SiC. This result suggests that carbon atoms experienced a millimeter-order mass transfer from graphite to silicon within 10 min. Atomic diffusion alone can hardly explain such a large transfer of carbon atoms within such a short period. The rapid reaction displayed by the long-distance mass transfer of carbon can be explained instead by gas-solid carbonization between carbon monoxide (CO) and solid silicon, since the atmosphere in which the reaction occurred comprised a vast majority of CO gas, according to the Boudouard equilibrium.
LTA-type zeolites were synthesized by the microwave-assisted hydrothermal process and conventional hydrothermal process. Obtained products were characterized by X-ray powder diffraction and X-ray absorption near edge structure measurements and their microstructures were observed by scanning electron microscopy. In this study, the effects of microwave-assisted hydrothermal process on the morphology (particle size etc) and microstructures for the LTA-type zeolite were mainly examined. As a result, the crystallization of precursor gel of LTA was rapidly carried out by the exposure of microwave for a significantly short term and consequently LTA-type zeolite obtained by the microwave-assisted hydrothermal process had well-defined cubic facet and moreover the small average particle size, compared with the samples obtained by conventional hydrothermal process.
Excellent quality amorphous aluminum oxide (AlOx) thin films have been obtained by atmospheric pressure solution-processed mist chemical vapor deposition (mist-CVD) technique at 400°C using water-free solvent. X-ray fluorescence investigations verified the formation of AlOx film by the mist-CVD. X-ray diffraction, X-ray photoelectron spectroscopy, ellipsometry and X-ray reflectivity analyses revealed that the synthesized amorphous AlOx films have bandgap of 6.5 eV, refractive index of 1.64 and mass density of 2.78 g/cm3. These values are comparable to those reported for high-quality amorphous Al2O3 thin films deposited by atomic layer deposition method.