Fabrication of Sr0.5Ba0.5Nb2O6 Nanocrystallite‐Precipitated Transparent Phosphate Glass‐Ceramics

Transparent (Sr_0.5Ba_0.5)Nb₂O₆ (SBN50) nanocrystallite‐precipitated phosphate glass‐ceramics were prepared by a conventional glass‐ceramic process. x(SrO–BaO–2Nb₂O₅) ? (100–4x)P₂O₅ (xSBNP) glasses with a refractive index of 1.9–2.0 exhibited high water resistance owing to the presence of Q⁰ and Q¹ phosphate units. Both bulk and surface crystallization of the SBN50 phase were observed in 20SBNP and 21SBNP glass‐ceramics. Although the nominal content of SBN50 crystals in the 21SBNP glass was larger than that in the 20SBNP glass, the latter exhibited better crystallinity of SBN50 and a higher number density of precipitated SBN nanocrystallites. By tuning the two‐step heat‐treatment and the chemical composition, transparent SBN50‐precipitated glass‐ceramics were successfully obtained. Given that no remarkable increase of the relative dielectric constants was observed after crystallization of the SBN50 nanocrystallites, it is postulated that the relative dielectric constant of the bulk is mainly governed by the amorphous phosphate region, and that the contribution of precipitation of the SBN50 nanocrystallites to the dielectric constant is not very significant in this system.     

Effects of sintering additives on dispersion properties of Al2O3 slurry containing polyacrylic acid dispersant

The effects of sintering aid adsorption on the dispersion properties of aluminum oxide slurries were investigated. We considered Al₂O₃ slurry without additives and Al₂O₃ slurry with a Mg additive with 0.1 mass% in oxide equivalent as a sintering aid. In this study, we evaluated the adsorption isotherm of polyacrylic acid (PAA) onto Al₂O₃ and the dispersion degree of Al₂O₃ slurries in sedimentation tests under gravity. The adsorption isotherm featured a characteristic adsorption isothermal line with a maximum value when Mg additive was present in Al₂O₃. In addition, the packing fractions did not correspond to the apparent viscosity. However, in slurry that was allowed to settle for several days, both of them agreed.Therefore, the disagreement between the packing fraction and the apparent viscosity immediately after preparation arose from changes of the dispersion state, such as the decrease of the distance between particles with time.     

Stable equilibrium shift of methane steam reforming in membrane reactors with hydrogen‐selective silica membranes

Equilibrium shifts of methane steam reforming in membrane reactors consisting of either tetramethoxysilane‐derived amorphous hydrogen‐selective silica membrane and rhodium catalysts, or hexamethyldisiloxane‐derived membrane and nickel catalysts is experimentally demonstrated. The hexamethyldisiloxane‐derived silica membrane showed stable permeance as high as 8 × 10^?8 mol m^?2 s^?1 Pa^?1 of H₂ after exposure to 76 kPa of vapor pressure at 773 K for 60 h, which was a much better performance than that from the tetramethoxysilane‐derived silica membrane. Furthermore, the better silica membrane also maintained selectivity of H₂/N₂ as high as 10³ under the above hydrothermal conditions. The degree of the equilibrium shifts under various feedrate and pressure conditions coincided with the order of H₂ permeance. In addition, the equilibrium shift of methane steam reforming was stable for 30 h with an S/C ratio of 2.5 at 773 K using a membrane reactor integrated with hexamethyldisiloxane‐derived membrane and nickel catalyst. © 2010 American Institute of Chemical Engineers AIChE J, 2011     

Composition dependence of the oxygen-evolution reaction rate on Ir x Ti1−x O2 mixed-oxide electrodes

Mudcrack-free oxide films of Ir _x Ti_1–x O₂ (0 < x 1) on titanium substrates were obtained, and the effects of the oxide composition on the rate of oxygen-evolution reaction were investigated. At x 0.6, Ir-rich grains appear on the mudcrack-free surface. In the purely single-phase region (0 < x 0.5), the pseudo-capacitive charge is proportional to the surface composition, x _s, and the exchange-current density for the oxygen-evolution reaction increases linearly with x _s at 0.2 x _s 0.5, with an extrapolated intercept at x _s 0.15, below which the oxides are inactive.     

Gas permeation properties for organosilica membranes with different Si/C ratios and evaluation of microporous structures

Organosilica membranes were fabricated using bridged organoalkoxysilanes (bis(triethoxysilyl)methane (BTESM), bis(triethoxysilyl)ethane (BTESE), bis(triethoxysilyl)propane (BTESP), bis(trimethoxysilyl)hexane (BTMSH), bis(triethoxysilyl)benzene (BTESB), and bis(triethoxysilyl)octane (BTESO)) to produce highly permeable molecular sieving membranes. The effect of the organoalkoxysilanes on network pore size and microporous structure was evaluated by examining the molecular size and temperature dependence of gas permeance across a wide range of temperatures. Organosilica membranes showed H₂/N₂ and H₂/CH₄ permeance ratios that ranged from 10 to 150, corresponding to network pore size, and both H₂ selectivity decreased with an increase in the carbon number between 2 Si atoms. Organosilica membranes showed activated diffusion for He and H₂, and a slope of temperature dependence that increased approximate to the increase in the carbon number between 2 Si atoms. The relationship between activation energy and He/H₂ permeance ratio for SiO₂ and organosilica membranes suggested that the molecular sieving can dominate He and H₂ permeation properties via the rigid microporous structure, which was constructed by BTESM and BTESE. With increased in the carbon concentration in silica, polymer chain vibration in organic bridges, which is a kind of solution/diffusion mechanism, can dominate the permeation properties. © 2017 American Institute of Chemical Engineers AIChE J, 63: 4491–4498, 2017     

Methanol oxidation on carbon-supported Pt-Ru and TiO2 (Pt-Ru/TiO2/C) electrocatalyst prepared using polygonal barrel-sputtering method

Methanol oxidation performance of a carbon-supported Pt-Ru alloy catalyst used at the direct methanol fuel cell (DMFC) anode is improved by adding TiO₂. However, the methanol oxidation performance of the electrocatalyst described above must be enhanced further to realize practical application in DMFCs. In this study, we used our original surface-modifying technique termed the “polygonal barrel-sputtering method” to prepare a carbon-supported Pt-Ru and TiO₂ (Pt-Ru/TiO₂/C) electrocatalyst offering higher methanol oxidation performance. The obtained results show that the methanol oxidation performance of the prepared Pt-Ru/TiO₂/C is superior to that using wet process as the TiO₂ deposition method. Furthermore, for our sputtering method, the peak current of methanol oxidation on the Pt-Ru/TiO₂/C is enhanced by increasing the TiO₂ deposited amount up to 2.8 wt.%. These results suggest that a Pt-Ru/TiO₂ interface area is increased using the polygonal barrel-sputtering method, providing the high methanol oxidation performance of Pt-Ru/TiO₂/C.     

Local coordination,electronic structure,and thermal quenching of Ce3+ in isostructural Sr2GdAlO5 and Sr3AlO4F phosphors

Sr₂GdAlO₅:Ce and Sr₃AlO₄F:Ce are isostructural phosphors in which the Ce³⁺ 4f-5d₁ transition can be efficiently excited by a photon with energy lower than 3.1 eV. Herein, we analyze the crystal chemistry of the Ce³⁺ local coordination, compare the thermal quenching behavior and construct the electronic structure of Ce³⁺ in them. The Rietveld refinement on two occupancy models suggests that Gd³⁺ only occupies the 8h site in Sr₂GdAlO₅; this provides a hint on the preferred occupancy of dopant Ce³⁺ in this site. The large crystal filed splitting of Ce_8h is mainly due to the fact that the 8h site is bonded to two oxygen with relatively short d_Sr/Gd-O and forms a quasi-square antiprism which experiences a large distortion. The Ce³⁺ 5d-4f luminescence in Sr₃AlO₄F is much more stable against thermal quenching than that in Sr₂GdAlO₅, as evidenced by the temperature-dependent luminescence intensity and luminescence decay studies. The energy of the O²⁻-Eu^3+/2+ and O²⁻-Ce^4+/3+ charge transfer as well as bandgap were estimated and the electronic structure of Ce³⁺ were constructed. A larger energy barrier ΔE_dC between the Ce³⁺ 5d₁ level and the conduction band bottom in Sr₃AlO₄F is seen from the Vacuum Referred Binding Energy (VRBE) diagrams which explains the higher thermal quenching temperature by thermal ionization model.     

一种新的精炼太阳能级多晶硅工艺的热力学分析(英文)

提出了一种新的硅精炼工艺生产太阳能级多晶硅,即Si-Al熔体低温凝固精炼硅技术。通过杂质在固相硅和Si-Al熔体中的分离热力学分析研究了采用Si-Al熔体分区凝固精炼硅的可行性。用温度梯度区域熔炼法来测定磷和硼的分离比,采用热力学计算金属杂质的分离比。新工艺具有很小的杂质低温分离比,表明其有很好的精炼能力。采用感应加热分区凝固实验进行验证;对Si-Al合金定向凝固中硅晶体生长进行了研究,结果表明,硅晶体的生长过程是受扩散控制的。     

Rectification of 3D data obtained from moving range sensor by using extended projective multiple view geometry

To measure the 3D shape of large objects, scanning by a moving range sensor is one of the most efficient methods. However, if we use moving range sensors, the obtained data have some distortions due to the movement of the sensor during the scanning process. In this paper, we propose a method for recovering correct 3D range data from a moving range sensor by using the multiple view geometry under projective projections in space-time. We assume that range sensor radiates laser beams in a raster scan order, and they are observed from two cameras. We first show that we can deal with range data as 2D images, and show that the extended multiple view geometry can be used for representing the relationship between the 2D image of range data and the 2D image of cameras. We next show that the extended multiple view geometry can be used for rectifying 3D data obtained by the moving range sensor. The method is implemented and tested in synthetic images and range data. The stability of the recovered 3D shape is also evaluated.     

Handwritten digit recognition: benchmarking of state-of-the-art techniques

This paper presents the results of handwritten digit recognition on well-known image databases using state-of-the-art feature extraction and classification techniques. The tested databases are CENPARMI, CEDAR, and MNIST. On the test data set of each database, 80 recognition accuracies are given by combining eight classifiers with ten feature vectors. The features include chaincode feature, gradient feature, profile structure feature, and peripheral direction contributivity. The gradient feature is extracted from either binary image or gray-scale image. The classifiers include the k-nearest neighbor classifier, three neural classifiers, a learning vector quantization classifier, a discriminative learning quadratic discriminant function (DLQDF) classifier, and two support vector classifiers (SVCs). All the classifiers and feature vectors give high recognition accuracies. Relatively, the chaincode feature and the gradient feature show advantage over other features, and the profile structure feature shows efficiency as a complementary feature. The SVC with RBF kernel (SVC-rbf) gives the highest accuracy in most cases but is extremely expensive in storage and computation. Among the non-SV classifiers, the polynomial classifier and DLQDF give the highest accuracies. The results of non-SV classifiers are competitive to the best ones previously reported on the same databases.