氧化物纤维增强陶瓷基复合材料高温力学性能及微观形貌研究

Study on the Mechanical Properties and microstructure of Oxide Fiber Reinforced Ceramic Matrix Composites at high Temperature

摘要:

本文研究了氧化物纤维增强陶瓷基复合材料在室温~1400℃条件下,其力学性能和微观结构随温度的变化规律。分别以氧化铝纤维和石英纤维作为增强体,采用溶胶-凝胶成型工艺制备出了氧化铝纤维增强二氧化硅复合材料(Al₂O_3f/SiO₂)和石英纤维增强二氧化硅复合材料(SiO_2f/SiO₂)两种氧化物纤维增强陶瓷基复合材料。分别研究了其在室温~1400 ℃温度条件下的拉伸强度及压缩强度,并采用电子显微镜(SEM)和X射线衍射(XRD)对复合材料的微观形貌和晶相结构进行了表征。结果表明,在室温~1000 ℃条件下,氧化铝纤维增强二氧化硅复合材料的力学性能远高于石英纤维增强二氧化硅复合材料。而当温度升高到1200 ℃及以上温度时,复合材料力学性能急剧下降,基体中的二氧化硅颗粒与氧化铝纤维之间发生强结合。当温度进一步提升到1300~1400℃时生成了莫来石相和α-方石英相,界面消失导致的脆性断裂是复合材料高温失效的主要机理。

Abstract:

The present article focuses on the change of mechanical properties of oxide fiber reinforced ceramic matrix composites with temperature from room temperature (RT) to 1400 ℃. Alumina fiber reinforced silica composite (Al₂O_3f /SiO₂) and quartz fiber reinforced silica composite (SiO_2f/SiO₂) were prepared by sol-gel process with alumina fiber and quartz fiber as reinforcement respectively. The tensile strength and compressive strength of the composites at room temperature ~1400 ℃ were investigated, and the microstructure and crystal phase structure of the composites were characterized by electron microscopy (SEM) and X-ray diffraction (XRD). The results show that the mechanical properties of alumina fiber reinforced SiO₂ composites are much higher than those of quartz fiber reinforced SiO₂ composites under RT~1000 ℃. However, while the temperature was raised to 1200^℃, the mechanical properties decrease sharply, and strong bonding occurs between silica particles and fibers. As the temperature was further increased to 1300~1400 ℃, mullite and α-quartzite phases were formed. The mechanical properties of composites are sharply decreased due to brittle fracture under the action of stress. The brittle fracture caused by the disappearance of interfaces is the main mechanism of high temperature failure of composites.