Nanocrystallization of Fe73.5Si13.5B9Nb3Cu1 soft-magnetic alloy from amorphous precursor in a magnetic field

The effect of a magnetic field on the nature of nanocrystallization from a melt-spun Fe_73.5Si_13.5B₉Nb₃Cu₁ amorphous precursor has been studied with the aim of controlling microstructures and magnetic properties. Annealing for magnetic crystallization was carried out at temperatures between the Curie temperature of the amorphous phase (586 K) and that of the crystalline phase (920 K). It was found that the {110} texture component in crystallized α-Fe(Si) phase increased in importance with increasing magnetic-field strength. An X-ray diffraction analysis based on the Shultz method revealed that the magnetic field caused preferential formation of {110}-oriented nuclei. In addition, the applied field enhanced crystallization kinetics, particularly the nucleation rate. No significant difference in grain growth behavior was observed as a result of applying a magnetic field. We therefore conclude that the development of the {110} texture by magnetic crystallization is predominantly attributable to preferential nucleation, rather than preferential growth, of {110}-oriented nuclei. The saturation magnetization of nanocrystallized specimens, evaluated using a vibrating sample magnetometer (VSM), was increased by the application of a magnetic field up to 4T during nanocrystallization.     

Hydrothermal epitaxy of KTaO3 thin films under supercritical water conditions

Potassium tantalate powders were hydrothermally synthesized at 400 °C using Ta₂O₅ and KOH as starting materials with various KOH concentrations (0.1–1.0 M) and heating durations (2–48 h). A defect pyrochlore phase of KTa₂O₅(OH)·nH₂O, was obtained at low KOH concentration and short reaction time. The perovskite phase of KTaO₃ predominated as the heating duration and the KOH concentration increased. Pure KTaO₃ was obtained in 0.5–1.0 M KOH aqueous solutions and reaction times of 8–48 h. Heteroepitaxitial KTaO₃ thin films were achieved on the (100) SrTiO₃ substrate in 0.5 M KOH solution under supercritical water conditions. Based on the XRD, SEM-EDX and EBSP (Electron BackScatter Pattern) results, epitaxial KTaO₃ crystals were grown on the (100) oriented single-crystal SrTiO₃ substrate. Synthesis of perovskite KTaO₃ crystals in supercritical water employed significantly low KOH concentrations (<0.5 M), which was far less than the very high concentrations (>7 M) required for conventional hydrothermal method.     

Thermal Stability of Hexaaluminate Film Coated on SiC Substrate for High-Temperature Catalytic Application

A coating of barium hexaaluminate (Ba_0.75Al_11.0O_17.25) on an α-SiC substrate and the thermal stability of the formed film were investigated for a high-temperature catalytic application. The film prepared by sol coating consisted of BaAl₂Si₂O₈ and α-Al₂O₃ phases and always contained many cracks or exfoliations after heating at 1200C. A hexaaluminate porous film was successfully formed by slurry coating without void formation at the interface between the film and the substrate and exfoliation due to the formation of the intermediate layer after heating at 1200°C. The microstructure of the film remained unchanged, even after heating at 1300°C.     

An X-ray absorption approach to mixed and metallicity-sorted single-walled carbon nanotubes

Carbon based structures have been widely studied by X-ray absorption (XAS), also called NEXAFS, which is a very useful bulk probing method that allows examining the unoccupied density of states (DOS) and the site selective bonding environment. Two very well known spectral features in the XAS core level spectrum are the σ* and π* bands, and both have been analyzed in several studies for graphitic-like systems. However, among all the carbon materials, the unique one-dimensional electronic properties attributed to single-walled carbon nanotubes (SWCNTs) exhibit features that reveal clearly their electronic structure in the core level XAS spectrum. In this article, we outline the C1s response in XAS, which is related to the DOS of the conduction band in SWCNTs and its fine structure, revealed by experiments performed on metallicity-sorted SWCNT material. The progress in the identification of changes in the site selective conduction band electronic structure with XAS is discussed in detail.     

Microstructures of Annealed TiNiSn-Based Alloy Ribbons

The thermoelectric half-Heusler compounds Ti _x NiSn_0.998Sb_0.002 (x = 1.0 to 1.2) and Ti _y Zr_0.25Hf_0.25NiSn_0.998Sb_0.002 (y = 0.5 to 0.65) with nonstoichiometric nominal compositions were prepared by spin-casting and subsequent annealing at 1073 K for 24 h. The dimensionless figure of merit ZT at room temperature was maximized at x = 1.1 and y = 0.6 in Ti-rich compounds through an increase in absolute Seebeck coefficients despite a decrease in electrical conductivities. ZT reached 0.07 at x = 1.1 and 0.14 at y = 0.6. In powder x-ray diffraction analysis, minor phases of β-Sn, TiNi, Ti₂Sn, and Ti₅Sn₃ were observed in addition to a major phase of half-Heusler. The quantity of the minor phases was minimized at x = 1.1 and y = 0.55, where the absolute Seebeck coefficients are maximized. In transmission electron microscopic (TEM) analysis of Ti_0.55Zr_0.25Hf_0.25NiSn_0.998Sb_0.002, crystal grains of the half-Heusler phase, from several hundred nanometers to several micrometers in size, were observed. TEM energy-dispersive spectroscopy measurements indicated that fluctuations of Ti, Zr, and Hf compositions within the Ti-site in the half-Heusler phase may occur. Thermoelectric properties were improved at x = 1.1 and y = 0.6 rather than at the stoichiometric compositions of x = 1.0 and y = 0.5 due to minimization of the precipitate quantities.     

STEAM DRYING OF SINTERED SPHERES OF GLASS BEADS

ABSTRACT

Superheated steam drying of sintered spheres of glass beads with different diameters is investigated to reveal the effects of the gravitational force on drying rates. In a previous study, the drying rate curves of small samples with coarse glass beads in which the frictional resistance to flow of water and the effect of the gravitational force are negligible, were predicted by an evaporation zone model.In the present investigation, the drying rate curves of sintered spheres of glass beads with diameters ranging from 1.53×10^-2m to 4.99×lO^-2m are experimentally and theoretically obtained, and also the capillary pressure curves are measured by use of Haines' apparatus. The drying rate curves of large samples in which the effect of the gravitational force can not be negligible, are compared with those for small samples and the difference among these curves is discussed in terms of the moisture distributions which are estimated from the evaporation zone model with the observed capillary pressure curves.     

野外试验场黄土的理化分析

本实验为低，中水平放射性废物浅地层处置安全评价提供现场土壤的物理化学参数。采样深度在０．５－９．１ｍ范围内，每个样品进行１０项测定；矿物组成，粒度分布、密度、总孔隙度、有效孔隙度、给水度、持水度、渗透系数、阳离子交换容量、含水量。     

POROSITY AND RESIDUAL EQUILIBRIUM SATURATION OF SINTERED SPHERES OF GLASS BEADS

Sintered spheres(made of glass beads) were simply produced with a definite diameter, with a precision of ±0·5 mm in diameter, for a wide range of sintered angles (0-27°). The experimental values of the porosity of the sintered spheres were consistent with the calculated results for the coordination number N ≠ 8. The residual equilibrium saturation, as one of the basic physical properties of sintered glass beads was investigated experimentally and theoretically, resulting in the presence of a distribution in the angle of pendular ring.