燃烧法制备镁铝尖晶石粉体及其烧结活性研究

Investigation on combustion synthesis of MgAl_2O_4 powder and its sintering activity

按Mg(NO3)2.6H2O与A l(NO3)3.9H2O的摩尔比为1∶2配料,分别添加20.120 g尿素、15.015 g尿素+4.500 g甘氨酸、7.987 g尿素+9.980 g甘氨酸为燃烧剂,采用燃烧合成法制备了镁铝尖晶石粉体,分析了镁铝尖晶石粉体的物相组成和显微结构,并用谢乐公式计算粉体的晶粒尺寸;然后,将镁铝尖晶石粉体成型为样块,在1 600℃保温3 h煅烧,计算块体的烧后永久线变化率,并检测烧后块体的吸水率、显气孔率和体积密度,分析其显微结构。结果表明:1)随着燃烧剂中甘氨酸含量的增加,制备的镁铝尖晶石粉体的晶粒尺寸逐渐减小,粒径分布逐渐均匀,但团聚现象逐渐明显。2)随着燃烧剂中甘氨酸含量的增加,由镁铝尖晶石粉体制成的块体在1 600℃保温3 h煅烧后的永久线收缩率逐渐增大,烧后块体的吸水率和显气孔率逐渐减小,体积密度逐渐增大;烧后块体中的颗粒粒径逐渐均匀,异常长大的晶粒逐渐减少。这表明,在燃烧剂中添加甘氨酸有利于提高燃烧合成法制备的镁铝尖晶石粉体的烧结活性。

MgAl2O4 powder was synthesized by combustion method, mixing Mg （NO3）2 · 6H20 and AI （NO3 ）3 · 9H2O according to the molar ratio of 1：2,and adding 20. 120 g urea,15. 015 g urea ＋4. 500 g glycine,7. 987 g urea ＋9. 980 g glycine as burning agent, respectively. The phase composition and microstructure of spinel powder were analyzed, and the grain size was calculated by Scherrer formula. Then, the sample blocks were prepared with spinel powder,and fired at 1600 ℃ for 3 h. The permanent linear change on heating was calculated ,water absorption,apparent porosity, and bulk density were determined ,and microstructure was analyzed. The results show that： （1）the grain size of the spinel powder decreases gradually,the distribution of grain size is more uniform, but the agglomeration becomes more obvious with the increase of the glycine addition; （2）the permanent linear shrinkage on heating and bulk density of spinel block fired at 1 600℃ for 3 h increase gradually, the water absorption and apparent porosity decrease, grain size becomes more uniform,less grains grow up abnormally with the increase of the glycine addition. It suggests that it is good for improving the sintering activity of spinel prepared by the combustion synthesis method to add glycine in burning agent.