LiAlO2为烧结助剂低温无压烧结制备致密Si3N4陶瓷

Preparation of dense Si 3N 4 ceramics by low temperature pressureless sintering with LiAlO 2 as sintering aid

以高α相含量的Si3N4粉体为主要原料,LiAlO2作为烧结助剂,在1650℃无压烧结制备Si3N4陶瓷。研究LiAlO2烧结助剂含量(质量分数分别为6%、9%、12%、15%、18%)及保温时间(1、4、7、10 h)对Si3N4陶瓷试样的线收缩率、质量损失率、相对密度、相组成以及显微结构的影响。结果表明:LiAlO2能够显著降低Si3N4陶瓷的致密化温度。随着LiAlO2含量的增加,试样的相对密度先增大后减小,烧结助剂含量为12%(w)时相对密度达到97%以上。而β-Si3N4转化率随着LiAlO2含量的增加而升高。LiAlO2含量为12%(w),保温时间为4 h时,试样的相对密度达到最高。随着保温时间继续延长,相对密度略有降低。但β-Si3N4转化率则随着保温时间延长而不断升高。

Si 3N 4 ceramics were prepared by pressureless sintering at 1650℃with highαphase content Si 3N 4 powder as the main raw material and LiAlO 2 as the sintering aid.The effects of the LiAlO 2 content(6%,9%,12%,15%,and 18%,by mass)and the soaking time(1,4,7,and 10 h)on the linear shrinkage,the mass loss and the relative density,the phase composition and the microstructure of the Si 3N 4 ceramics were analyzed.The results show that LiAlO 2 can play a significant role in reducing the densification temperature of the Si 3N 4 ceramics;with the increase of the LiAlO 2 content,the relative density of the specimens increases firstly and then declines,reaching 97%at the LiAlO 2 content of 12%;the conversion rate ofβ-Si 3N 4 increases with the increasing content of LiAlO 2;when the soaking time is 4 h and the LiAlO 2 content is 12%,the relative density of the specimens is the highest;the relative density decreases slightly with the further prolonging of the soaking time,but the conversion ofβ-Si 3N 4 increases with the prolonging of the soaking time.