气压烧结氮化硅陶瓷致密化研究

Densification Research of Gas Pressure sintered Silicon Nitride

研究了Ｓｉ３Ｎ４ 陶瓷恒温气压烧结的致密化行为．恒温烧结过程中，表面液相蒸发形成的毛细管拉力以及从表面到中心的元素浓度梯度，是致密化动力之一．在此动力的作用下，Ｓｉ３Ｎ４ 呈现着从边缘到中心的渐进的“波浪式”传质过程和致密化进程．“取向”现象证实了表面液相蒸发的拉力作用，同时说明材料的显微结构不仅与实施工艺有关，而且与素坯的表面状态有关．

The densification behavior of isothermal gas pressure sintered Si 3N 4 was studied. It was discovered that the evaporation of liquid phase on surface can cause the capillary force and the elemental concentration grade, which is one of the driving forces of the densification. With this force, “wave like” densification process of Si 3N 4 from edge to center come into being. The phenomenon of the “orientation effect” proves that the evaporation of liquid phase on surface is one of the driving force. It is also suggested that the final microstructure of materials relates to not only sintering process, but also the formal shape of green body. This is important for the microstructure design of the materials.