Fabrication of SiC bodies by optimized gel-casting method

Abstract

In this research, acrylate gel maker monomers Mathacrylamide (MAM) and Methylenebisacrylamide (MBAM) were used through a gel casting process to fabricate SiC bodies. Investigation of rheological behavior of suspensions showed that optimum amount of surfactant (Tetramethylammonium hydroxide) was equaled with 0.7 wt% of ceramic powders and ceramic powders could be added up to 37 vol% of solvent without any problems in casting. The effects of monomers content, monomers ratio and also solid loading on gelation time, bending strength of samples were investigated. Results showed that increasing the monomers content (MAM + MBAM) and ceramic solid loading led to the reduction of gelation time. Also alteration of these parameters resulted in variation of samples bending strength from ~6 MPa to 19 MPa, the best strength was obtained in the sample containing 35 wt% monomers with the MAM/MBAM ratio of 3 and 35 vol% SiC. Finally the samples containing different amounts of SiC were casted according to the pre-determined optimum parameters and after being dried they were sintered at 2150 °C for 1 h. According to the results, the highest density, Young's modulus, hardness and indentation fracture resistance were obtained in sample containing 37 vol% SiC and were equaled with 96.89%, 499.24 GPa, 27.51 GPa and 6.3 MPa·m1/2, Respectively. Microstructural studies showed that cleavage fracture planes, crack deflection and branching were the most important mechanisms on toughness enhancement.