水热法低温合成α-Al_2O_3粉体的影响因素

FACTORS AFFECTING PREPARATION OF α-Al_2O_3 POWDER AT LOW TEMPERATURE BY HYDROTHERMAL METHOD

以工业Al(OH)3为原料,通过引入晶种和矿化剂,用水热法低温合成α-Al2O3粉体。研究了固相含量、原料粒度、水热温度、保温时间、晶种加入量、矿化剂种类等因素对α-Al2O3产率和产物晶粒形貌的影响。结果表明:随固相含量的增加,产物的收率增加,当固相含量增大到8%(质量分数,下同)时,产物的收率开始降低;原料粒度从16μm减小到2.5μm时,产物的收率增大,当原料粒度减小到1.5μm,产物的收率变化不明显;随着水热温度的升高、水热时间的延长,α-Al2O3含量相对增多,晶粒发育渐趋完善;晶种的引入有效地降低了α-Al2O3成核的活化能,有利于α-Al2O3形成;矿化剂的种类对水热合成α-Al2O3的作用效果差别很大,加入矿化剂KBr更有利于α-Al2O3生成和晶体发育。发育完善的α-Al2O3呈六方柱状,晶体显露{0001}和{1120}面族。最佳的实验工艺条件为:固相含量5%,反应温度390℃,保温时间2h,晶种加入量5%(质量分数),填充度40%(体积分数),矿化剂KBr加入量0.5mol/L。

The hydrothermal method was used to prepare α-Al2O3 powders using industrial grade AI（OH）3 as a starting material with the addition of seeds and mineralizers. The effects of solid content, particle size of the starting material, hydrothermal temperature, hydrothermal holding time, addition of seeds and kinds of mineralizers on the productivity of α-Al2O3 and on the morphology of the product were investigated. The results show that the productivity of α-Al2O3 increases and then decreases with the increase of the solid content. The smaller the particle size （16 um to 2.5 um） of starting material, the more the productivity of α-Al2O3, but firther decreasing the particle size exhibits little influence on the productivity. The productivity of α-Al2O3 increases and the crystal structure develops well with elevating hydrothermal temperature, prolonging hydrothermal holding time and addition of seeds. The nucleation activation energy of α-Al2O3 decreases with the addition of seeds. The well-developed α-Al2O3 crystal is a hexagonal prism with {0001 } and { 11 20} crystal face appearance. The processing parameters are a solid content of 5% （in mass）, temperature of 390 ℃, holding time of 2 h, the addition of 5%（in mass） seeds, a filling factor of 40% （in volume） and mineralizer of 0.5 mol/L KBr.