摘要
The primary impregnation slurry was prepared using active alumina(56.25 mass%),kaolin(15 mass%),zirconia(3.75 mass%),deionized water(25 mass%),and extra adding FS(0.2 mass%)and CMC(0.4 mass%).The effects of the active alumina particle size(d50=5.043,2.934,and 1.629μm)on the rheology and the thixotropy of the slurry were researched.It was found that the bimodal activeα-Al2O3(AMA-10)with d50=1.629μm was optimum.The secondary impregnation slurry was prepared using AMA-10,kaolin and zirconia as the main raw materials.Then the alumina-based reticulated porous ceramics were fabricated by the organic foam impregnation method combined with a secondary vacuum impregnation process.The influence of the AMA-10 content on the properties of the ceramics was studied.The residual stress of the specimens was analyzed by finite element analysis.The results show that the smaller alumina particle size and multimodal distribution are beneficial to the thixotropy of the primary impregnation slurry.The secondary vacuum impregnation technique can significantly improve the mechanical properties,the thermal shock resistance and the residual strength of the alumina-based reticulated porous ceramics.With the decrease of alumina content in the secondary impregnation slurry,the residual stress of the external layer of ceramic reinforcement gradually changes from tensile stress to compressive stress,which effectively inhibits the expansion of the surface crack,and remarkably improves the crushing strength retention ratio of alumina reticulated porous ceramics.
