Alumina-titania composite powder and process for preparing the same

摘要

Alumina-titania composite powder comprising spherical particles each of which contains about 30 to 80 wt % of gamma - phase or delta -phase alumina and about 70 to 20 wt % of titania comprising rutile-phase in the majority and is substantially free from X-phase (3Al2O3-TiO2) and aluminum titanate-phase. These alumina-titania composite powders are prepared by blowing a vapor mixture of AlCl3 and TiCl4 into a burning flame to effect oxidation, which is characterized in that a temperature of a mixing section, where a combustible gas, an oxidizing gas, AlCl3 gas, TiCl4 gas and a carrier gas are mixed and subjected to combustion, is kept at about 1450 DEG C. or higher and lower than a melting point of aluminum titanate; a temperature of an outlet portion of a reacting section connected to the mixing section is kept at about 800 DEG C. or higher; and an average total gas retention time in the mixing section and the reacting section are 20 to 500 msec.