Al_2O_3/SiC纳米复合陶瓷中SiC粉料的氧化现象

Oxidation of SiC powder in Al_2O_3/SiC nanocomposite

为验证在空气环境中,烧结Al2O3/SiC纳米复合陶瓷过程是否出现纳米SiC粉料的氧化现象,以及氧化后纳米陶瓷性能的变化规律,分别采用了常压氩气保护烧结和常压空气环境中烧结两种工艺,制备了Al2O3/SiC纳米复合陶瓷.经检测,前者性能优异,其相对密度为98.82%,抗弯强度为489 MPa,断裂韧性达6.67 MPa.m1/2;而后者性能大幅度降低,经x-ray检测发现,烧结后样品中SiC衍射峰消失,即纳米SiC严重氧化;同时发现随纳米SiC粒径的减小及含量增加,氧化现象加剧,性能更加变差.借助断口的SEM图像对烧结过程SiC粉料氧化机理进行分析,发现:碳化硅已经分解为CO2和SiO2,前者以气体形式挥发并在陶瓷体内留下气孔,而后者以玻璃相形态存在于晶界中.

In order to validate both oxidation phenomena of SiC nano powder during sintering and variety in properties of nano-ceramics after oxidation, Al2O3/SiC nanocomposite was fabricated through pressureless sintering in argon atmosphere and in air respectively. The experimental results show that the ceramics sintered in argon atmosphere has good physical and mechanical properties where the relative density is 98.82%, the flexural strength and fracture toughness reach 489 MPa and 6.67 MPa· m^1/2 respectively. It has been verified by x-ray diffraction that for the ceramics sintered in air, the diffraction peaks of SiC disappears. It means that the oxidation of SiC nano powder is serious during sintering, resulting in a significant decrease in the properties of the ceramics sintered in air. With reducing its diameter and increasing its content, the oxidation of SiC nano powder becomes much more serious so that the properties of the ceramics is much worse. The SEM analysis on pores and glass phases. It can be guessed that during SiO2, where the former results in the formation of boundaries. the fracture surface reveals that there exist a lot of sintering in air, SiC has decomposed into CO2 and pores and the later become glass phases at grain