Synthesis Of Plate-like Single-phase α-Al₂O₃ Particles

Plate-likeα-Al₂O₃ have been widely used in the fields of pigment,cosmetic, vehicle paint,refractory,and toughness ceramic because of its especial structure and excellent properties.In the paper,a new method to prepare plate-likeα-Al₂O₃ is introduced.Plate-like single-phaseα-Al₂O₃ particles were successfully synthesized by calcining the ball-milled mixture of bayerite and K₂SO₄ at 900℃for 2h.The average diameter of pate-likeα-Al₂O₃ particles is around 700 nm.The phase transition sequence of milled bayerite and the influence of the ball milling and K₂SO₄ additive on the structure and morphology of the product were studied in the paper to realize artificial control of plate-likeα-Al₂O₃ particle size and shape during the preparation process.It was found that the milled bayerite undergoes a series of phase transformations via theα-Al(OH)₃→γ-AlOOH→γ-Al₂O₃→α-Al₂O₃ path.The addition of K₂SO₄ andα-Al₂O₃ seeding to the bayerite powder does not affect the sequence of the phase transformation of bayerite.However,the completion temperatures of the transformation toα-Al₂O₃ in the milled bayerite with K₂SO₄ additive andα-Al₂O₃ seeding are about 200℃lower than that without K₂SO₄ additive andα-Al₂O₃ seeding.The influence of the rotation speed of the mill and milling time on the structure and morphology of the product were significant.It was found that milling at a high speed and for a longer time can prepare plate-likeα-Al₂O₃ particles with better purity and smaller average diameter.