Development of mullite-SiC nanocomposites by pyrolysis of filled polymethylsiloxane gels

A modified processing route, which is based on the active filler controlled pyrolysis technique, was followed here to form a homogeneous mullite-SiC nanocomposite. An Al2O3-filled polymethylsiloxane was prepared by the in-situ formation of the SiCO network via a sol-gel process. The filled gels obtained in this way show an excellent machinability with conventional surface grinding techniques. Heat treatment up to 1500°C initiated crystallization of mullite, which showed intragranular SiC precipitation. Based on microstructure characterization in conjunction with thermal analysis, a formation mechanism is proposed which includes the glass transition temperature of SiCO as well as its phase sparation into SiO2 plus nanosized SiC crystallites, giving rise to this new mullite-SiC nanocomposite.