Natsukaze Saito

Particulate characteristics and deposition features of fine AIN powder synthesized by vapour-phase reaction

Fine AIN powder was synthesized by the vapour-phase reaction of AICl3 and NH3 at 600 to 1100° C, and the particulate characteristics and the deposition features were investigated. The powder deposited near the AlCl3-feeding nozzle included radially-grown particles with columnar crystals. The powder deposited apart from the AlCl3-feeding nozzle consisted of only fine, spherical particles. Vapour-phase reaction at 1100° C produced fine powder, which was characterized by uniform and fine particle size; its distribution width was from 0.1 to 0.3μm, and median diameter was 0.18μm. Deposition area of the powder was affected by the reaction temperature and the temperature profile in the reactor.

Preparation of fine composite particles composed of inorganic solid powders and organic polymers by utilizing liquid-liquid dispersion

Abstract Composite particles composed of organic polymer and inorganic powder were prepared by two methods; suspension polymerization and drying-in-liquid method. The hydrophilic powders such as nickel, magnetite and indium oxide were added into the continuous water phase. Composite particles which were uniformly covered with these powders were prepared. It was investigated how the operating conditions, such as the size of solid powder, the amounts of powders added and the impeller speed, affected the characteristics of composite particles.

Sintering and characterization of Al2O3-TiB2 composites

Abstract Al 2 O 3 -TiB 2 composites containing 0–50 wt% TiB 2 were prepared by sintering at 1600–1750°C for 15–120 min in a vacuum. Relative density increased with TiB 2 addition from 97% (no TiB 2 ) to about 99% (10–40 wt% TiB 2 ) on sintering at 1750°C for 60 min. TiB 2 behaved as a sintering aid to promote densification by inhibiting rapid grain growth of Al 2 O 3 . Bending strength and microhardness increased with increasing relative density. In particular, microhardness was so improved as to exceed that of Al 2 O 3 and reach 30·1 GPa. Resistivity decreased with increasing TiB 2 content and dropped down to 3 × 10 −2 ω m with 30 wt% TiB 2 .

Microencapsulation of thermal-sensitive pigment with inorganic wall material by interfacial reaction in multiple dispersion

Microcapsules, of which the wall material was made of calcium silicate, with a core material of thermal-sensitive pigment were prepared by interfacial reaction in multiple dispersion. The microcapsules obtained were characterized as follows. The shape was observed with a low-vacuum scanning electron microscope (LVSEM). The size was directly measured from the LVSEM micrographs. The yield was evaluated by the total mass balance of the materials involved. The color was observed by the naked eye. Effects of the concentration of stabilizer and the impeller speeds on the mean particle size and the yield were investigated.

Synthesis of AlN by the nitridation of the floating Al particles in N2 gas

The nitriding reaction of floating Al particles in N2 gas was studied at 1350°-1550°C. The hollow spherical and fibrous AlNs formed were examined by X-ray diffraction and scanning electron microscopy. The nitriding reaction of floating Al particles in N2 gas proceeded in the following four steps: (i) floating Al particles melted and became spherical by surface tension, (ii) up to 1350°C the nitriding reaction was controlled by the diffusion of nitrogen through the AlN surface layer, (iii) cracks propagated in the AlN layer at 1400°-1550°C. The nitriding reaction rapidly proceeded with the eruption of internally melted Al, (iv) the eruption of Al also caused the nitriding reaction between vaporized Al and N2 gas to form AlN, resulting in hollow spherical AlN and fibrous AlN. The synthesized AlN was white, indicative of high purity. Since the particle size of floating Al was determined by controlling the N2 gas velocity, the classification of Al particles was possible. The mean size and size distribution of hollow spherical AlN particles formed were controlled within the range 4 to 12μm. The hollow spherical AlN particles were so brittle that they were easily crushed to fine particles even by fingers. Thus obtained AlN particles were very fine and had narrow size distribution of 0.1-0.2μm.

The preparation of microcapsules which include silicon carbide particles in a wall material

Microcapsules, of which the wall material was made of polystyrene, with a core material of water were prepared by the drying-in-liquid method. In order to improve the thermal conductivity of the wall material, an attempt was made to get silicon carbide (SiC) particles to disperse in it. SiC powder had been treated with a silane coupling agent to change its affinity for an oil phase. When untreated SiC powder was added, spherical-shaped single cellular microcapsules were obtained and SiC particles were localized at the surface of the wall material. When treated SiC powder was added, irregular-shaped multicellular microcapsules were obtained and SiC particles were dispersed in the wall material. The formation mechanism of the microcapsules was proposed on the basis of stabilizing effect of SiC particles on coalescence between water-in-oil droplets.

Preparation of Microcapsules Containing Camellia Oil with Heterocoagulation between Chitosan and Oleic Acid

It was tried to microencapsulate camellia oil using heterocoagulation between fatty acid dissolved in camellia oil and chitosan dissolved in the continuous water phase. Oleic acid as a fatty acid was dissolved in camellia oil in order to certainly form the microcapsule shell made from oleic acid and chitosan. The microcapsules were observed with optical microscope and characterized about the diameters, ζ-potential, FTIR analysis and adhesion feature on human hair. Microcapsules with the mean diameter in the range from ca. 1.5 μm to 4.5 μm could be prepared with the preparation method presented in this study. The oil droplets of camellia oil charged negatively to be -54.6 mV and the microcapsules charged positively to be 59.6 mV. The microcapsules adhered well on the negatively charged human hair and were kept stably before and after drying at room temperature for 24 h and blowing.

Preparation of Soft Microcapsules Containing Multiple Core Materials with Interfacial Dehydration Reaction Using the (W/O)/W Emulsion

Abstract The soft microcapsules containing eucalyptus oil, ubiquinone and the fine water droplets could be prepared with interfacial dehydration reaction between hydroxy methyl cellulose and tannic acid using the water-in-oil-in-water type multiple (W/O)/W emulsion. The diameters of the microcapsules and the content and the microencapsulation efficiency of the core materials were significantly affected by the revolution velocity (Nr1) to form the (W/O) emulsion and the revolution velocity (Nr2) to form the (W/O)/W emulsion and the lecithin concentration. The mean diameters of the inner water droplets and those of the microcapsules were proportional to Nr1−1.25 and Nr1−0.11 for the revolution velocity (Nr1), respectively. With increasing the revolution velocity (Nr1), the content and the microencapsulation efficiency of the inner water droplets increased, while those of the oil phase decreased. The mean diameters of the microcapsules were proportional to Nr2−1.1. The content and the microencapsulation efficiency of the inner water droplets and those of the oil phase decreased with the revolution velocity (Nr1) and increased with the lecithin concentration.