A novel approach to develop composite ceramics based on active filler loaded precursor employing plasma assisted pyrolysis

Aim of the work was to employ for the first time the novel process of plasma assisted pyrolysis (PAP) for developing dense ceramic composites based on a polyorganosilazane as a ceramic forming binder and TiSi2 as active filler.

Initially it was necessary to investigate the influence of PAP on the pyrolysis behavior of the precursor in comparison to conventional pyrolysis. We could demonstrate that the ceramic yield as well as the elemental composition of the polyorganosilazane are not adversely influenced by PAP process. This is an indication that no depolymerization of the precursor occurred under plasma atmosphere, which is a precondition for the use as ceramic binder to manufacture ceramic composites.

TiSi2 exhibits a high mass gain during thermal treatment in air, but the conversion under N-2 atmosphere into nitrides is insufficient. In contrast the use of PAP led not only to an enhanced filler conversion but also to a densification of the composite. The resulting microstructure is dominated by Ti(C,N) as well as a mixture of alpha- and beta-Si3N4 phases embedded in an amorphous SiCN matrix.

It could be demonstrated that plasma assisted pyrolysis is a very suitable technology to process dense Ti-Si-C-N composite materials with a tailored microstructure.