Preparation of high purity α-Al2O3 from industrial aluminum hydroxide

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, χAl2O3 and ρ-Al2O3. 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.