No abstract

Optically transparent and stable sols of copper ion doped zinc sulfide (ZnS:Cu) nanoparticles were obtained by heating a mixture of ethylene glycol aqueous solution and sulfide precipitate at 348 K for 24 h. The sulfide precipitates containing zinc ions, copper ions and citrate ions were peptized in an aqueous solution of ethylene glycol having a 0.5 molar fraction of [Ethylene glycol]/ ([H 2 O]+[Ethylene glycol]). Photoluminescence characteristics and stability of the sols depended on the amount of citrate ions in the aqueous solution which was used for preparing sulfide precipitates. The citrate ions strongly affected the characteristics of the obtained sols with dispersion of the copper ion doped-ZnS nanoparticles. According to TGDTA curves and N 2 adsorption isotherms of the precipitated sulfides, the citrate ions in the aqueous solution containing zinc ions, copper ions coprecipitated in the sulfide precipitates formed by adding the sodium sulfide aq. The citrate ions played an important role for the peptization and the formation of stable sols.

Possibility of a use of SiC as SPS die was examined. Although SiC has good strength even at high temperature, electrical conductivity is too low as the SPS die. Maximum output voltage of typical SPS machine is 10 V. Joule heat of SiC by application of 10 V is too small to increase its temperature. One idea to solve this problem in this study is to apply higher voltage to the SiC die. Using prototype high voltage SPS equipment, the temperature of SiC die was successfully elevated. Another idea is to heat the SiC die in advance. SiC has a semiconducting behavior, so that the electrical conductivity at high temperature becomes sufficient for the ordinary SPS equipment. Using SPS machine which has hot-wall, heaters surrounding the die, the temperature of the SiC die was successfully increased by application of low voltage. This SPS had similar sintering effects as the ordinary ones. Partly transparent alumina was successfully prepared. Initial compositional fluctuation of Pb (Zr,Ti)O3was maintained after it was densified by this SiC-SPS.

An aqueous solution of aluminum nitrate and yttrium nitrate was prepared and ethylenediamine molecules were added into the aqueous solution. The obtained precipitated precursor particles were fired and oxide particles were obtained. When ethylenediamine was used for the precipitation, the single phase of YAG was obtained by firing the precursor particles at more than 1073 K. On the other hand, when hexamethylenediamine was used for the precipitation, the YAG phase was not able to obtained by firing the precursor at 1373 K. Formation behavior of YAG phase greatly depended on the used diamine molecules. Furthermore, Ce 3+ -doped YAG particles were prepared by firing precipitated particles from the aqueous solution in which the nitrates of Al 3+ , Y 3+, and Ce 3+ were dissolved with ethylenediamine as precipitating agent. The PL spectra of the obtained particles had the photoluminescence (PL) peak at 535 nm even though the firing temperature was 1073 K.

Sols with stable dispersion of layered titanate nanoparticles were prepared at 298 K using dialysis of a mixed solution of ethylene glycol, TiCl3, ammonium carbonate, and H2O2. Raman spectra of the particles in the obtained sols showed Raman scattering peaks which can be assigned to a layered titanate structure. The stability of the obtained sols depended on the molar ratio of [ammonium carbonate] / [Ti ion]. The molar ratios of 3, 4, and 5 produced transparent yellow stable sols. Peptization of titanium hydroxide precipitate with H2O2 formed stable sols with dispersion of layered titanate nanoparticles, which had plate -shaped morphology. The obtained sols formed layered titanate thin films on glass substrates easily by drying the sols. Furthermore, when the layered titanate thin films were heated at 773 K for 1 h, anatase TiO2 thin films were obtained with (101) orientation of crystallites and optical transparency.