用六面顶压机研究了AlN微米粉体高压(2.0~6.0 GPa)下晶粒演化行为, 用 X 射线衍射仪和扫描电子显微镜对高压样品的物相组成、晶粒尺寸以及微观形貌进行了表征. 结果表明, 在室温下, AlN压制体的相对密度随着压力的升高也相应增加, 开气孔率则呈下降趋势. 经6.0 GPa压制后样品的相对密度达到88.72%, 出现了“冷烧结”现象. 高压作用后AlN微米晶的粒径变小, 压力从常压升高到6.0 GPa时微粉的平均粒径由2.10 μm下降到1.47 μm, 存在明显的压制碎化效应. 该效应提高了AlN粉体的表面自由能, 增强了粉体烧结的驱动力; 另一方面, 由于AlN粉末产生了一定的位错、裂纹等缺陷, 还可以起到活化烧结的作用, 提高AlN陶瓷的烧结速率.
Grain fragmentation of AlN micron?powder under high pressure (2.0–6.0 GPa) was studied on cubic high pressure apparatus. Phase composition, grain size and microstructure of the samples were characterized by X-ray diffraction (XRD) and scanning electron microscope (SEM). The results show that relative density of AlN microcrystal increases and open pore decreases with the rise of high pressure. “Cold-sintering” occurs in the AlN sample pressed at 6.0 GPa because its relative density reaches 88.72%. Obvious pressure-induced grain fragmentation is observed during the compacting of AlN powder under high pressure. The average particle diameter drops to 1.47 μm from 2.10 μm when high pressure is increased to 6.0 GPa from atmospheric pressure. Pressure-induced grain fragmentation can improve the surface free energy of AlN powder and increase sintering driving force. Meanwhile, it can activate sintering to improve AlN sintering rate because of the presence of defects (such as dislocation, crack, etc.) caused by high pressure.
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