籽晶对碳酸铝铵热分解相变及α-Al_2O_3纳米粉烧结活性的影响

EFFECTS OF SEED ON PHASE TRANSFORMATION OF AACH UPON HEATING AND SINTERING REACTIVITY OF ULTRAFINE α-Al_2O_3 POWDER

研究了碳酸铝铵的合成，并对碳酸铝该加热过程中的物相变化和。α－Al2O3籽晶对θ－Al2O3→α－Al2O3的相变的影响进行了分析．结果表明，将硫酸铝铵溶液以小于20mL／min的速度滴入碳酸氢按溶液，可以合成颗粒尺寸小于5um的碳酸铝铵沉淀．不合籽晶的碳酸铝铵煅烧时θ－Al2O3→α－Al2O3相变温度为1100℃，获得的α－Al2O3粒径约为70um；质量分数为5％的α-Al2O3籽晶可将该相变温度降至900℃，获得的α-Al2O3粒径约为30nm．烧结实验表明，经1400℃，2h烧结后，粒径约30um的α-Al2O3粉可达到98．5％理论密度；而粒径约70um的α－Al2O3粉在相同烧结条件下的相对密度为95.0％.

Syathesis of ammonium aluminum carbonate hydrokide (AACH), phase transformationof AACH upon heating, and effects of a-Al2O3 seed on the transformation kinetics were investigated. Theresults show that AACH with particle sizes less than 5 nm can be produced by adding ammonium aluminumsulphate solution to ammonium hydro-carbonate solution with a rate less than 20 mL/min. For the samplewithout α-Al2O3 seed, phase transformation temperature of e-A12O3 - a-Al2O3 is 1100℃, and particlesize of the obtained α-Al2O3 powder is about 7O nm. θ-Al2O3 →α-Al2O3 transformation temperaturecan be reduced to 900℃ by adding 5%α-Al2O3 seed, and particle size of the obtained α-Al2O3 powder isabout 30 nm. Sintering experiments show that the a-Al2O3 powder with a particle size of 30 nm can besilltered to 98.5% relative density at 1400℃ for two hours, and the powder with a particle size of 70 nmcan reach 95.0% relative density under the same sintering condition.