Preparation Of Flaky Alumina Powder By Molten Salt Synthesis Method

Flaky alumina is one of the new inorganic fine chemicals with special two-dimensional structure and excellent physicochemical prosperities, and is widely applied in pigments, cosmetics, fillers and abrasive. The powders were prepared by molten salt synthesis method, and the influence factors, such as molten salts, sintering conditions, additive and seed, were investigated. The flaky powders obtained were characterized by means of microscope, TG-DTA, laser sizer, covering power measurement, et al. It was found that flaky a-A12O3 powder with diameter of 5~25um, thickness of 200~400nm and aspect ratio of 30~ 60, could be synthesized at 1200℃ for 5 hours when the mole ratio of aluminum sulfide to mixture sulfate salts (Na2SO4:K2SO4:=:2.4:1.6) was 1:4, and the additive amounts of phosphate, titania and silica were 3wt%, lwt% and lwt% (based on alumina) respectively. The size and aspect ratio of the powder can be adjusted and controlled by changing the amount of additives. The crystal growth mechanism of flaky alumina was also studied, which is useful to control the crystal growth of alumina in molten salts.