Preparation of ultrafine α-Al₂O₃ powders by catalytic sintering of ammonium aluminum carbonate hydroxide at low temperature

Abstract

The precursor of ammonium aluminum carbonate hydroxide was synthesized by using aluminum sulfate (Al₂(SO₄)₃) and ammonium carbonate (NH₄)₂CO₃). The effects of α-Al₂O₃ seeds and mixture composed of α-Al₂O₃ and ammonium nitrate, as well as multiplex catalysts (AT) on phase transformation of alumina in sintering process were investigated respectively. The results show that the α-Al₂O₃ seeds and the mixture of α-Al₂O₃ and ammonium nitrate can lower the phase transformation temperature of α-Al₂O₃ to different extents while the particles obtained agglomerate heavily. AT has great potential synergistic effects on the phase transformation of alumina and reduces the phase transformation temperature of α-Al₂O₃ and the trends of necking-formation between particles. Therefore the dispersion of powder particles is improved significantly.

Keywords

ammonium aluminum carbonate hydroxide / phase transformation temperature / α-Al₂O₃ / agglomeration