Study On Preparation Process And Properties Of Gelcasting SiC Based Composites

In order to solve problems such as the high temperature of SiC ceramics densification,difficulty of molding complex shape of SiC based composites and the toxic gel system,the nontoxic glutinous rice flour-GRF-poly carboxylic acid JSS water based gel-casting method was studied.SiC-ZrSiO₄,SiC-ZrO₂,SiC-Sialon and SiC-Al N composites were prepared by using the gel-casting method and pressureless sintering process,and the effect of the combinations and atmosphere（air,N₂）on the structure and properties of SiC based composites was discussed.The results showed that through the adjustment of SiC particles’ sizes and the selection of JSS,a novel nontoxic GRF-JSS based gel-casting method was obtained,SiC ceramics slurry with solid content of 65 vol.% could be prepared by using this method;using the same amount of ZrSiO₄ and ZrO₂,the structure and properties of SiC-ZrSiO₄ and SiC-ZrO₂ composites which sintered in air atmosphere were better than those in N₂ atmosphere,meanwhile,the composition and structure of sintering SiC-ZrSiO₄ composites samples were better than those of SiC-ZrO₂ composites in the same atmosphere;similarly,to the same amount of Sialon and Al N,the structure and properties of sintering SiC-Sialon composites samples were batter than those of SiC-Al N composites in N₂ atmosphere;among four kinds of combinations including ZrSiO₄,ZrO₂,Sialon and Al N,ZrSiO₄ was the most suitable one for SiC based composites.After sintering the composites at 1550 ℃ for 4h in air atmosphere,the highest room temperature flexural strength of SiC-ZrSiO₄ composites samples was 56.25 MPa,and the residual strength after 5 times thermal shock was 16.2MPa.