Thermally curable poly(silylacetylene)siloxane as polymeric precursor of SiC ceramic

The pressureless pyrolysis of poly(silylacetylene)siloxane precursor to silicon carbide (SiC) was studied. Poly(silylacetylene)siloxane was synthesized via organometallic condensation. The precursor resin was well soluble in acetone, toluene and tetrahydrofuran (THF), etc. Thermal cure was conducted readily at 180-250 °C to form a hard brittle solid, and the cure mechanism was radical polymerization of ethynyl groups. The ceramic yield of pyrolysis at 1500 °C was at about 67 wt.%. The molar ratio of Si/C in the SiC was found at 1:1.1-1:3 based on elements analysis. The results of x-ray diffraction (XRD) revealed the typical β-SiC structure in the poly(silylacetylene)siloxane derived ceramics.