Development of Si(3)N(4/)BAS ceramic matrix composite for engineering applications

The processing response of a 70% silicon nitride-30% barium aluminum silicate (70%-Si(3)N(4)-30%-BAS) ceramic-matrix composite was studied using pressureless sintering. The relationship between the processing parameters and the microstructural constituents, such as morphology of the beta-Si(3)N(4) whisker and crystallization of the BAS matrix, was evaluated. The mechanical response of this array of microstructures was characterized for flexural strength, as well as fracture behavior, at test temperatures up to 1300 C. The indentation method was used to estimate the fracture resistance, and R-curves were obtained from modified compact-tension samples of selected microstructures at room temperature. Further whisker morphology modification was performed based upon abnormal grain growth via different method. It was observed that the presence of even a small amount of abnormally grown beta-Si(3)N(4) grains improved the fracture toughness and minimized the variability in flexural strength.