Solid State Phenomena Vols. 124-126

Abstract: Al2O3-SiO2 nanoparticles have been synthesized by a sol-gel processing. Size and composition of the synthesized particles can be controlled by manipulating the relative rates of the hydrolysis and condensation reaction of precursor. The average size of synthesized Al2O3-SiO2 nanoparticles was about in the size range of 50~100nm. The effects of synthesis parameters, such as the molar ratio of water to precursor, the molar ratio of water to surfactant and stirring rate, are discussed.

Abstract: The organic-inorganic hybrid membranes of poly(N-vinylpyrrolidone) (PVP) and 3- aminopropyltriethoxysilane (APTEOS) were prepared by sol-gel process and their permeation properties of N2 and O2 were studied. The gas permeability coefficients of N2 and O2 are increased with increasing temperature in a range of 30-50°C. The positive dependence on temperature and higher ideal separation factor than theoretical Knudsen value indicates that PVP/APTEOS hybrid membranes follow solution-diffusion mechanism, which is applied to nonporous membrane. The permeability coefficients of N2 and O2 are decreased with increasing PVP content, at a given temperature. It can be explained that the stronger interaction between PVP and APTEOS reduces available free volume, although the increasing of PVP content may lead to an enhancement of chain flexibility.

Abstract: Uniform spherical- and rod-shaped TiO2 nanoparticles of anatase phase were prepared using decanoic acid at 300°C by reverse micelle method. The nanoparticles were characterized by transmission electron microscope (TEM), scanning electron microscope (SEM), X-ray diffractometry (XRD) and FT-Raman spectroscope. The content of decanoic acid and operating temperature were noted as crucial parameters, controlling the shape, size and phase of TiO2 nanoparticles. RMS roughness (1.62 nm), measured by atomic force microscope (AFM), confirmed its superiority over other methods. The DCB photodegradation reaction rate constant (first order) TiO2 nanoparticles was found superior to that of commercial TiO2, Degussa P-25.

Abstract: In this paper, the influence of nickel (Ni) nano-powders addition on the microstructures and dielectric properties of Ba(Ti,Zr)O3 based Y5V non-reducing ceramics were investigated. The X-ray diffraction (XRD) analysis indicated that the primary phase was Ba(Ti,Zr)O3 and no Ni phase appeared until the amount of Ni exceeded 5mol%. Scanning electron microscope (SEM) observation showed that the Ni particles distributed homogenously throughout BTZ ceramic matrix. The incorporation of Ni altered the perovskite lattice parameters and thus led to the change of polarization degree under electric field and the improvement of the dielectric constant at Curie temperature.

Abstract: Molten Soda lime glass (SLG) was penetrated into the surface of ZTA at 1500°C for the holding time of 1 to 10 h. The depth of the glass penetration increased with increasing holding time. The thermal expansion mismatch and elastic property mismatch between the penetrated glass and ZTA produced residual compression in the surface region during cooling. This residual compression enhanced the flexural strength and fracture toughness remarkably.

Abstract: Nano infiltration transient eutectic ceramic (NITE-SiC) was fabricated by hot pressing method using Al2O3 and Y2O3 as sintering additives. The ratio of the Al2O3/Y2O3 additives was changed between 6:4 and 4:6. The densification and mechanical properties were investigated for the sintered temperature. The starting powder was high purity β -SiC nano-powder with an average particle size of 30nm. The bending strength characterization and densification of NITE-SiC was investigated by the FE-SEM and three point bending test.

Abstract: Single phase monoclinic vanadium dioxide (VO2) films were successfully grown on sapphire (001) substrate by means of an inductively coupled plasma (ICP)-assisted sputtering with an internal coil. In x-ray diffraction patterns, we observed reflections originating from monoclinic VO2 with a main peak at 2θ = 39.77° corresponding to VO2 (020) for films on sapphire (001) substrates. The VO2 films exhibited metal-insulater transition (MIT) at temperatures around 65°C with three orders of change in resistivity. A simple device of VO2 film on sapphire (001) substrate having aluminum electrodes as ohmic contacts with gap separation of 1.0 mm showed current jump at an applied voltage of 48 V. The current jumped from 7 mA to 200 mA which was a limited value of voltage source.

Abstract: The characteristics of nucleation and the crystal growth of aragonite-precipitated calcium carbonate in Ca(OH)2 – MgCl2 – CO2 system by a carbonation process is investigated. MgCl2, in this study, was added in order to increase the formation yield of aragonite precipitated calcium carbonate. Optimum conditions of the concentration of the reactants, the temperature and the amount of additives were studied. The formation yield of calcite gradually decreased, and the formation yield of aragonite increased with the addition of MgCl2. A higher formation yield of above 98% for aragonite is obtained by the adding of the Mg2+ ion in a 0.2M Ca(OH)2 – 0.6M MgCl2 – CO2 system at 80
. The nucleation rate increased as the temperature decreased and as the CO2 gas flow rate increased. The particle size and aspect ratio increased at a high temperature, a low flow rate of gas, and a high concentration of Ca(OH)2 slurry. Small-sized aragonite was obtained at a low temperature. The increase in crystal size with the decrease in the CO2 gas flow rate can be explained by the decrease in the nucleation rate, in addition to the increase in the crystal growth rate resulting from the decrease in the dissolution rate to CO3 2- ion.

Abstract: SiC nanowires could be grown homogeneously within SiC fiber preforms by controlling the concentration of a reactant gas. The morphology and the growth behavior of the SiC nanowires were largely dependent on the degree of the reactant supersaturation. The SiC nanowires incorporated in the fiber preform increased the surface area at which the matrix deposition could take place, enhancing an efficiency of the matrix infiltration and altering the remaining pore structure of the SiCf/SiC composite.

Abstract: Tourmaline has unique electrical properties originated from its crystal structure such as pyroelectricity, piezioelectricity and emission of anion. These properties can derivate the making of feeble current around 0.06 mA. This weak current enables to electrolyze continuously and to make the hydroxyl anion, which may play a role of surface active agent against fouling of ocean organism. Two kinds of the mixture, tourmaline-monazite-quartz and tourmaline-monazite-illite-zeolite, were tested for the filling materials of antifouling paints. As a whole, the anion emits actively, at least around 4000 negative ion/cc. This high emission property maintains constantly for long time over 500 days. This implies that the tourmaline mixture treated mechanochemically can emit anion over 4000 negative ion/cc for a long time. These results enable us to make possible for application of the tourmaline containing mixture as the filling materials of antifouling paint