Silicon based preceramic polymers as a matrix material in composite technology

In this thesis, two preceramic polymers with different side groups, polymethylsilsesquioxane (PMSQ) and polyphenylsilsesquioxane (PPSQ), used as matrix material for preparation of ceramic matrix composite by addition of four different ingredients (i.e., steel fiber, silicon carbide, tin sulfide and vermiculite). PMSQ and PPSQ matrix composite materials were produced by mixing powder components, and pressed with uniaxial warm pressing under 100 MPa pressure for 2 min at 60C and 150C, then, cross-linked at 250C and 300C for 4.0 h, respectively. The cross-linked samples were heat treated at five different pyrolysis temperatures (i.e., 400, 500, 600, 700, and 800C) for 2 h. The effect of different side groups and pyrolysis temperature on the thermal, physical, mechanical property of the materials, and phase and micro-structural development in the produced composite samples were investigated by thermal (TG-DTA), phase (XRD), microstructural (SEM-EDX) analysis and density and compressive strength measurements. As a result of this study, it was observed that the PPSQ polymer have positive effect on the thermal degradation of composite material and the compressive strength values of the PPSQ matrix composite samples have considerably stable at between 150 and 600C by comparison with PMSQ matrix samples. The formation of the pore quantity and pore size distribution was depended on the used preceramic polymer side group and applied heat treatment temperatures.