Journal of Inorganic Materials

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Synthesis of Ultrafine α-Alumina Powder by Pyrolysis of Ammonium Aluminium Carbonate Hydroxide

LI Ji-Guang; SUN Xu-Dong; ZHANG Min; LI Xiao-Dong; RU Hong-Qiang   

  1. School of Materials Science and Metallurgy; Northeastern University Shenyang 110006 China)
  • Received:1997-11-20 Revised:1998-01-19 Published:1998-12-20 Online:1998-12-20

Abstract: By using ammonium aluminium sulfate and ammonium hydro-carbonate as the starting materials, the synthesis of ammonium aluminium carbonate hydroxide (NH4AlO(OH)HCO3)
was studied. It was found that NH4AlO(OH)HCO3 can be synthesized by adding ammonium aluminium sulfate solution to ammonium hydro-carbonate solution
with a adding rate less than 1.2L·h-1. Under other conditions the precipitate was γ-AlOOH in the experimental range. The sequence of phase transformation of
γ-AlOOH during heating was found to be γ-AlOOH →γ-Al2O3→δ-Al2O3θ-Al2O3→α-Al2O3; while that of NH4AlO(OH)HCO3 was found to be NH4AlO(OH)HCO3 →amorhous Al2O3θ
-Al2O3→α-Al2O3. The transformation temperatures of NH4AlO(OH)HCO3 to θ-Al2O3 and α-Al2O3 were both about 100→ lower than those of γ-AlOOH. γ-AlOOH can transform to
α-Al2O3 completely by calcining at 1200℃ for 1h, and the obtained powder,with a particle size of 150nm, can be sintered to 84.46% relative density at 1450→
for 2h. NH4AlO(OH)HCO3 can transform to α-Al2O3 completely by calcining at 1100℃ for 1h, and the obtained powder, with a particle
size of 70nm, can be sintered to 97.80% relative density under the same sintering condition.

Key words: NH4AlO(OH)HCO3, α-Al2O3, ultrafine powder, synthesis, sintering

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