Effect of Content of Mg(NO_3)_2·6H_2O on Fabrication of α-Alumina Nanopowders by Thermal Decomposition of Ammonium Aluminum Carbonate (AACH)

摘要

An α-Al_2O_3 and MgAl_2O_3 spinel phase doped α-Al_2O_3 nanopowders were fabricated by the thermal decomposition and synthetic of ammonium aluminum carbonate hydroxide (AACH). Crystallite size of 5 to 8 nm were fabricated when reaction temperature of AACH was low, 8℃, and the highest [NH_4~+][AlO(OH)_2~-][HCO_3~-] ionic concentration of pH 10 from the ammonium hydrogen carbonate (AHC) aqueous solution. The phase transformation of amorphous-s, θ-, α-Al_2O_3, MgAl_2O_3 spinel phases was examined at each temperature according to the amount of Mg(NO_3)_2·6H_2O and AACH. A time-temperature-transformation (TTT) diagram for thermal decomposition in air was determined. Homogeneous, spherical α-Al_2O_3 nanopowders with a particle size of 60 nm were obtained by firing the crystallites, which had been synthesized from AACH at pH 10 and 8℃, at 1050℃ for 6 h in air.