Abstract
The formation of finely-divided alumina from AlCl3 by the vapor phase decomposition with steam or oxygen was investigated with emphasis on the effects of its reaction conditions on the properties of the products. The reaction apparatus and conditions are shown in Fig. 1 and Table I, respectively.
The reaction products from AlCl3 and H2O at 700°and 900°C were amorphous and contaminated with a Cl-containing compound, presumably AlOCl. The amorphous products crystallized in κ-Al2O3 by heating to 830°C. The products from AlCl3 and H2O at 1100°C and from AlCl3 and O2 at 1000°and 1100°C were δ-Al2O3 with a small amount of κ-Al2O3 (Table I). The electron micrographs (Fig. 3) show that the reaction products are spheres with diameters smaller than 2000Å. The particle sizes of the products prepared from AlCl3 and H2O are smaller and have wider distributions than those from AlCl3 and O2. The particle size distributions of products from AlCl3 and O2 are shown in Fig. 4. The distribution in Run 0-4 where AlCl3 and O2 were mixed at the highest temperature zone spreads toward smaller particle sizes. The wider distributions in AlCl3-H2O systems and in Run 0-4 are considered to have been caused by the fact that the reaction between AlCl3 and H2O or O2 at 1100°C took place rapidly before both the reactants were mixed homogeneously. The present results show that the alumina powder with narrow particle size distribution can be obtained from AlCl3 and O2 by mixing them at a lower temperature and subsquently heating the mixture at temperature above 1000°C.
