Through X ray diffraction patterns and scanning electronic micrographs, temperature dependence of the
crystal structure
of roasted diasporic bauxite at different temperatures and the digestibility of roasting production were investigated systematically. The lattice parameters of unit cell for chemically purified diaspore and unequilibrium alumina contained oxide obtained from the diaspore roasted at different temperatures were determined. It is found that, with roasting temperature increasing, the roasting production changes from the original dense and perfect diaspore crystal into imperfect corundum with many microcracks and small pores on its surface and then into perfect corundum with low digestibility. The optimum roasting temperature with best digestibility is approximately 525 ℃ when residence time is about 25 min. It is thought that the change of
crystal structure, formation of microcracks and small pores in the
temperature field are the main essential reasons for improving digestibility of diasporic bauxite and its roasting production.