采用Li2O-Al2O3助烧剂低温埋碳制备Si3N4陶瓷

Preparation of Si3N4 ceramics by Li2O-Al2O3 sintering aid at low temperature with carbon embedded

为了制备致密的Si3N4陶瓷,在Si3N4粉末中加入15%(w)的助烧剂(Li2O-Al2O3),经过球磨、造粒、烘干成型后,在传统电炉中埋碳和Si3N4粉,于1550、1600、1650℃保温2 h后无压烧结制备Si3N4陶瓷,研究了烧结助剂配比和烧结温度对试样致密化、线收缩率、质量损失率、相转变以及微观结构的影响。结果表明:1)随着助烧剂中Li 2O比例的增加,Si3N4陶瓷的致密度先增加后降低。随着温度的升高,Si3N4陶瓷的密度不断提高,当达到1600和1650℃时,试样的相对密度分别达到93%和95%以上;2)在1600℃时,所有试样物相中都已经生成β-Si3N4,并随着烧结温度的升高其转化率逐渐增加,显微结构照片可以看到明显的棒状β-Si3N4;3)采用低温埋碳和Si3N4粉的烧结工艺为低成本Si3N4陶瓷的制备提出了可行的方法。

The dense Si 3N 4 ceramics were prepared by adding 15 mass%additives(Li 2O-Al 2O3)in Si 3N 4 powder,ball-milling,pelleting,drying,molding and pressureless sintering in an electric furnace at 1550,1600,or 1650℃for 2 h with Si 3N 4 and carbon powders embedded.The effects of the sintering aid proportion and the sintering temperature on the densification,linear shrinkage,mass change,phase transformation,and microstructure were researched.The results reveal that:(1)the densification of Si 3N 4 ceramics increases first and then decreases with the increasing ratio of Li 2O in the additives;with the increase of the temperature,the density of Si 3N 4 ceramics increases continuously;when the temperature reaches 1600 and 1650℃,the relative density of the specimens is over 93%and 95%,respectively;(2)at 1600℃,β-Si 3N 4 forms in all specimens and the conversion rate increases gradually with the increase of the sintering temperature;elongatedβ-Si 3N 4 can be seen from the SEM images;(3)the low-temperature sintering of silicon nitride ceramics with Si 3N 4 and carbon powder embedded provides a feasible method for the preparation of low-cost Si 3N 4 ceramics.