Thermal analysis of corundum crystallization

With thermal analysis (DTA/TG) the crystallisation behaviour of corundum wi th influence of the fluor compounds were investigated. The formation of alu minium fluoridhydroxide in the temperature range 400-600 degrees C are obse rved. Through the influence of AlF3 or HF the strong exothermic effect incr eased and a rapid loss of mass were noticed. The particle of corundum grow more, when the exothermic effects are large. We supposed, that also these exothermic effect will be due to the decomposi tion of may be adsorbed AlOF gas molecules.