莫来石加入量对SiC-莫来石材料性能的影响

Effect of mullite addition on properties of SiC-mullite composites

以SiC颗粒(2～1mm、≤1mm)、SiC细粉(≤0.066mm)、莫来石细粉(≤0.074mm)和SiO2微粉(≤0.045mm)为原料,在w(SiC细粉)=40%的基础配方中分别以质量分数为5%、10%、15%、20%和25%的莫来石细粉取代相应量的SiC细粉,并外加2%的SiO2微粉,成型后分别在1300℃和1500℃的大气气氛中煅烧3h,测定试样煅烧前后的质量变化率以及烧后试样的显气孔率、常温抗折强度和抗热震性,并用扫描电镜观察试样的显微结构。结果表明:在SiC自保护氧化的作用下,试样的抗氧化性较强,而且随着莫来石加入量的增大,1300℃烧后试样的氧化程度减小,1500℃烧后试样的氧化程度先减小,至15%后又增大;1300℃烧后试样比1500℃具有较高的抗热震性,并且随着试样中莫来石加入量的增大,烧后试样的抗热震性提高。

SiC -mullite composites with different addition of muliite were prepared by using SiC grains （2 - 1 mm, ≤1 mm）,SiC powder（ ≤0.66 mm）,mullite powder（≤0.074 mm） and SiO2 powder（ ≤0.045 mm）. Based on the formula, w（SiC powder） =40%, mullite powder in mass percentage of 5%, 10%, 15% ,20% and 25% was respectively added to replace corresponding SiC powder and then addition 2% silica fume. After moulding ,the specimen was fired at 1 300℃ and 1 500℃ respectively for 3 h, Mass change ratio,apparent porosity ,cold crushing strength and thermal shock resistance of burned specimens were determined and microstructure was analyzed by SEM. The results showed that the specimens had good oxidation resistance by self protection oxidation of SiC;with the increase of mullite addition,the oxidation of the specimens fired at 1 300℃ decreased while that of the specimen fired at 1 500℃ decreased firstly and then began increasing when the mullite addition came up to 15% ;the specimens fired at 1 300℃ had the better thermal shock resistance,which increased with the increase of mullite addition.