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 n anocomposite. An Al2O3-filled polymethylsiloxane was prepared by the in-sit u formation of the SiCO network via a sol-gel process. The filled gels obta ined in this way show an excellent machinability with conventional surface grinding techniques. Heat treatment up to 1500 degreesC initiated crystalli zation of mullite, which showed intragranular SiC precipitation. Based on m icrostructure characterization in conjunction with thermal analysis, a form ation mechanism is proposed which includes the glass transition temperature of SiCO as well as its phase sparation into SiO2 plus nanosized SiC crysta llites, giving rise to this new mullite-SiC nanocomposite. (C) 2000 Elsevie r Science Ltd. All rights reserved.