Preparation Of High Strength Silicate Bonded SiC Porous Composite Materials

In this paper,considering the low-temperature sintering and the high-temperature oxidation of silicon carbide,according to the designing principle of composite materials,especially the match of the thermal-expansion coefficient, mullite,Beta - the spodumene glass-ceramic,Alpha - the cordierite glass-ceramic and the borosilicate glass were designed.Porous silicon carbide composite materials with high strength were made under low temperature.Mullite/SiC porous composite material was got through joining high-activity aluminum hydroxide aluminum raw materials and silicon raw material gas phase silicon dioxide and micro-silicon dioxide,and the mullite conversion rate in the low temperature 1330℃has been reached 93%;the strength of the composite material was 86 MPa when the porosity was 31%.The influence of the sintered temperature, the ratio of aluminum raw material and the silicon raw material to the mullite conversion rate were discussed;Mullite/SiC porous materials with high strength of 70 MPa when the porosity was 28%was made using andalusite and kyanite mineral raw materials.Beta - the spodumene glass-ceramic and Alpha - the cordierite glass-ceramic bonded SiC porous composite materials with porosity of 28%and flexural strength 108MPa,131MPa separately were got with LAS and MAS as additives through fast high temperature sintering,then fast cooling,after that reaching the coring and crystallization temperatures slowly,keeping 2h;the influence of the sintered temperatures and the ratio of LAS,MAS to the mechanical properties were discussed.Amorphous glass bonded SiC porous composite material was got by choosing borosilicate glass 3.3 which has the closer thermal-expansion coefficient with SiC as matrix-phase,through liquid phase sintering mechanism and hot unbalance enhancement mechanism.Through the model established,the stress of the matrix-phase in the composites, which caused by hot unbalance,was calculated approximately,and the influence to the mechanical properties of the matrix-phase with different thermal-expansion coefficients was also discussed.It was showed that we got the silicon carbide porous ceramic with high porosity and good mechanical properties under the low temperature with narrow grain-size distribution silicon carbide and mullite,α-cordierite glass-ceramic,β- spodumene glass-ceramic and the borosilicate glass 3.3 as matrix-phase,avoiding the silicon carbide material active oxidation.Glass-ceramic with the particle size 0.1μm has the best enhancement effect.The borosilicate glass 3.3 has the obvious effect on reducing the silicon carbide's sintering temperature.The residual stress which causes by the hot unbalance has less influence to the material mechanical properties in the porous composites materials.