二维石英纤维增强多孔Si_3N_4-SiO_2基复合材料的制备及其力学性能

Preparation and properties of 2D fused-silica fiber reinforced porous Si_3N_4-SiO_2 matrix composites

采用浆料法结合真空浸渗工艺,制备了二维(2D)石英纤维增强多孔Si3N4-SiO2基复合材料。采用X射线衍射技术就粘结剂种类和氮化硅的加入对材料析晶性能的影响进行了分析,采用扫描电镜对不同浸渗次数复合材料的截面和断口形貌进行了观察,并采用裂纹偏转因子对复合材料断裂模式进行了分析。结果表明,粘结剂中杂质Na+促进了石英析晶,而Si3N4对石英析晶影响不大。增加浸渗次数虽不能有效提高复合材料强度,但却使裂纹偏转因子变小,断裂模式由韧性断裂向脆性断裂转变,断口形貌由纤维成束拔出变为多级拔出。

2D fused-silica fiber reinforced porous Si3N4-SiO2 matrix composites were prepared by combining the slurry method and vacuum infiltration technology. X-ray diffraction technique was used to analyze the crystallization behavior of the fused silica with different binders and of the addition of silicon nitride. The polished section and fracture morphology of the composites with different cycles of infiltration were characterized by SEM. Using crack deflection parameter, the fracture models were discussed. The results show that the concentration of Na^＋ has great effect on the crystallization of silica, while Si3N4 powder has little influence on it. Increasing the cycles of infiltration, the strength of the composites can not be improved, but the crack deflection parameter decreases, the fracture model converts toughness rupture into brittle rupture, and the fracture morphology turns out to be multistage pullout rather than whole fiber tow pull-out.