Optimization of Process Parameters for Preparation of Flaky α-Al₂O₃ by Molten Salt Method with Al(OH)₃

The flaky α-Al₂O₃ was prepared by the molten salt method with Al(OH)₃ as precursor. The effects of the mass ratio of Al(OH)₃ to molten salt (NaCl+Na₂SO₄) (1:1,1:2,1:3), the mass fraction of Na₃PO₄ additive (0.1%, 1%, 2%), the mass fraction of TiOSO₄ additive (0.5%, 1%, 3%), the sintering temperature (900,1 050,1 200 ℃) and the holding time (1,3,5 h) on the Al₂O₃ morphology were investigated by orthogonal experiment combined with single factor method,and the optimal process parameters were obtained. The results show that the factors influencing the morphology of flaky α-Al₂O₃ in descending order were sintering temperature, mass ratio of Al(OH)₃ to molten salt, Na₃PO₄ content, and holding time. Combined with the single factor method, the optimal process parameters were sintering temperature of 1 050 ℃, Al(OH)₃ to molten salt mass ratio of 1:2, Na₃PO₄ mass fraction of 1%, TiOSO₄ mass fraction of 1%, and holding time of 3 h. Under the optimized process conditions, the flaky α-Al₂O₃ had the average diameter of 15.413 μm, thickness of 0.765 μm, and radius to thickness ratio of 20.147; the Al₂O₃ was pure and free of impurities.