Effect of ρ-Al2O3-CAC composite sintering aid on properties of porous SiC ceramics
In order to improve the performance of porous SiC ceramics,green silicon carbide was used as the main raw material,graphite as the pore forming agent,and ρ-Al2O3-CAC as a composite sintering aid which is prepared from calcium aluminate cement(CAC)and hydrated alumina(ρ-Al2O3),firing at 1 450 ℃ for 3 h.The effect of the ρ-Al2O3-CAC addition(2.5％-20％,by mass)on the phase composi-tion,microstructure,and properties of porous SiC ceramics was studied.The results reveal several key find-ings:ρ-Al2O3-CAC facilitates the oxidation of silicon carbide and reacts in situ with SiO2 produced by the oxidation of silicon carbide,forming a glass-mullite composite;bubbles are introduced into the composite phase,with their size increasing with the rising ρ-Al2O3-CAC addition;at an ρ-Al2O3-CAC addition of 12.5％,the prepared porous SiC ceramics exhibit the optimal comprehensive properties:the apparent po-rosity is 39.1％;the flexural strength is 39.3 MPa;the air permeability reaches 26.74 m3·h-1·kPa-1·m-2,and the thermal shock resistance is the best.
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