High purity $\alpha$-$\rm Al_2\rm O_3$ synthesis from boehmite produced by hydrothermal oxidation of aluminum

We demonstrate the possibility of obtaining high-purity aluminum oxide by successive processes of hydrothermal oxidation of aluminum and vacuum heat treatment of the solid oxidation product (boehmite). The results of studies of changes in the structural properties and chemical purity of alumina samples obtained in the different modes of vacuum heat treatment of boehmite are presented. Experiments have shown the ability to produce alumina with a purity of $99.997\%$ (the total content of all impurities is approximately $30$ ppm) of aluminum with a purity of $99.8\%$. It was shown that the chemical purity of the final product depends on not only the temperature and time of heat treatment but also a number of other parameters of the process.