Preparation of high purity α-Al2O3 from industrial aluminum hydroxide

Abstract

Aluminum oxide (alumina; Al₂O₃) has advantages such as its thermal, chemical, and physical properties when compared with several ceramics materials. It is widely used in ceramics such as firebricks, abrasives and integrated circuit (IC) packages; catalysts; catalyst supports; ion exchange and other fields. Alumina has a complex structure and many crystalline polymorphic phases such as α-Al₂O₃, βAl₂O₃, γ-Al₂O₃, δ-Al₂O₃, θ-Al₂O₃, η-Al₂O₃, κ-Al₂O₃, χA_l2O₃ and ρ-A_l2O₃. Among these phases, α-Al₂O₃ is widely used and studied as high temperature structural material, electronic packaging, corrosion resistance ceramics and translucent ceramics. This study focus on the preparation of high purity α-Al₂O₃ from industrial aluminum hydroxide. The results show that after removing Na₂O and SiO₂ with distilled water, the sample was dissolved in NaOH solution to form NaAlO₂ solution. Precipitating of Al(OH)₃ from NaAlO₂ solution with one of the following substances: HCl (4N), H₂SO₄ (4N), CH₃COOH (4N) or CO₂ (45% Vol). The precipitated Al(OH)₃ was filtered and washed with distilled water and then dried. Finally, thermally decompose Al(OH)₃ at 1100⁰C in 2 hours to form pure α-Al₂O₃.