太阳能热发电用氧化铝基复相陶瓷抗热震性及EPMA分析

THERMAL SHOCK BEHAVIOUR AND EPMA OF Al_2O_3 MATRIX COMPOSITE CERAMICS USED IN SOLAR THERMAL POWER

为了提高Al2O3陶瓷的抗热震性及强度,在Al2O3基陶瓷中添加SiC、nano-ZrO2+SiC,利用无压烧结工艺,制备了用于太阳能热发电的Al2O3-SiC及Al2O3-ZrO2(3Y)-SiC复相陶瓷。材料的EPMA分析结果表明:样品中ZrO2颗粒在室温下为以亚稳四方相存在,在裂纹尖端应力场的作用下,ZrO2粒子发生四方相→单斜相的相变吸收能量,从而提高了材料强度及断裂韧性;原料中的部分SiC颗粒发生氧化反应,反应生成莫来石,针棒状莫来石形成桥连结构,阻止热震情况下产生的微裂纹发展成危险裂纹,从而提高材料抗热震性。SEM研究显示,SiC晶粒在外力作用下发生穿晶断裂、被拔出及桥结作用。

The Al2O3-SiC and Al2O3-ZrO2（3Y）-SiC composite ceramics were prepared by pressureless sintering.The results of EPMA show that the disperse phase of the metastable tetragonal ZrO2 grains inclines to transfor-mation to monoclinic phase at room temperature.In most ceramics,the dispersed metastable tetragonal ZrO2 grains lead to high strength and toughness.The mechanism of the ZrO2 phase transformation toughening is mainly due to the tetragonal（t）-monoclinic（m） ZrO2 phase transformation caused by the external stress,which absorbs the fracture energy,so that the stress concentration in the crack tip is released.Acicular mul-lite which is obtained from reaction of oxidized SiC with Al2O3 leads to the formation of the bridge structure,which prevents the dangerous crack from micro-crack deterioration,consequently,enhancing materials＇ thermal shock resistance.SiC rupture,SiC pulling-out and SiC bridging are clearly seen in SEM figures.