Processing and characterization of particles reinforced Sisingle bondOsingle bondC composites via pyrolysis of polysiloxane with SiC or/and Al fillers

Polysiloxane loaded with SiC as inert filler, and Al as active filler, was pyrolyzed in nitrogen to fabricate Sisingle bondOsingle bondC composites, and the processing and properties of the filled Sisingle bondOsingle bondC composites were investigated. Adding SiC fillers could reduce the linear shrinkage of filler-free cured polysiloxane in order to obtain monolithic SiC/Sisingle bondOsingle bondC composites. The flexural strength of SiC/Sisingle bondOsingle bondC composites reached 201.3 MPa at a SiC filler content of 27.6 vol.%. However, SiC/Sisingle bondOsingle bondC composites exhibited poor oxidation resistance, thermal shock resistance and high temperature resistance. Al fillers could react with hydrocarbon generated during polysiloxane pyrolysis at 600 °C and N2 at 800 °C to form Al4C3 and AlN, respectively. The volume expansions resulting from these two reactions were in favor of the reduction in linear shrinkage and the improvement in flexural strength of SiC/Sisingle bondOsingle bondC composites. The flexural strength of Al-containing SiC/Sisingle bondOsingle bondC composites was 1.36 times that of SiC/Sisingle bondOsingle bondC composites without Al at an Al filler content of 20 vol.%. The addition of Al fillers remarkably improved the high temperature resistance and oxidation resistance of SiC/Sisingle bondOsingle bondC composites, but not thermal shock resistance.