冲击波处理的AlN粉体的低温烧结特性

Characteristics of Low-Temperature Sintering of Shocked Aluminium Nitride Powder

利用X射线衍射仪，对冲击波（压力为9．SGPa）处理的AIN粉体的衍射峰展宽现象进行分析，得到粉体内平均微观应变为2．85×10-3；相应的位错密度为1011／cm2；体内储存的缺陷能为0．36Cal／g．研究了以冲击波处理的AIN粉体为原料，在添加6Wt％以Dy2O3为主的助烧结剂的低温无压烧结过程中，缺陷对低温烧结和热导率的影响．结果表明：冲击波处理AIN粉体所致缺陷能，除了可以促进烧结；同时还起到了去除AIN晶格中的Al2O3，及提高热导率的作用．粉体中储存的能量在烧结过程中释放，使冲击粉试样比未冲击粉试样达到最大线收缩速率时的温度降低25℃；试样在1610℃，无压烧结4h，冲击粉试样密度为理论值的98％，而未冲击试样仅为80％．位错在烧结过程中为氧扩散提供渠道，使氧的扩散除了通过溶解一析出过程，还有固态扩散的作用，而这些位错在烧结后期得到回复．

AIN powder was treated by shock waves with pressure of 9.8GPa. X--ray line broadening effect was found as the result of strain stored in shocked AlN lattice. Estimated value of the strain is 2.85×10-3, related dislocation density in shocked AlN powder is in the order of 1011/cm2, the energy stored in shocked powder is 0.36Caf/g. The low temperature pressureless sintering processand thermal conductivity of shocked AlN powder with 6wt% additives were investigated. The results showed that, the dislocation in shocked AlN powder can promote low temperature sinetring.In addition, it can remove A12O3 from AlN lattices and achieve high thermal conductivity. The energy stored in the shocked powder was released during the sintering process. The temperature of maximum shrink rate of shocked sample was about 25'C lower than that of unshocked one. The density of the shocked sample sintered at 1610℃ for 4h was 98% of its theoretical value, compared with 80% of the unshocked one. The dislocation in shocked AlN powder can provide paths for the diffusion of oxygen through the grain in sintering process. So besides di ssolution-reprecipitation,dislocation-- enhanced diffusion contributes its efforts to sintering, and it is beneficial for both sintering and achieving high thermal conductivity. The dislocation then can recover in the laterstage of the sintering process.