Comparison of two processes for manufacturing ceramic matrix composites from organometallic precursors

A commercial polysilazane is used as a silicon carbonitride matrix precurso r for the manufacture of ceramic matrix composites using bi-directional SiC Nicalon fabrics as reinforcing material. The objective is to develop a sim ple and fast process lending to materials able to compete with SiC/C/SiC co mposites obtained by the Chemical Vapour Infiltration (CVI) route. Two proc esses are investigated: (I) a 'conventional' process using the densificatio n of a SiC fibre preform by several cycles of impregnation of the preform w ith the polymer followed by pyrolysis and (2) a 'modified' process consisti ng in a powder filling of the fibre preform prior to the precursor impregna tion and pyrolysis. This paper describes the different steps of both proces ses. The materials obtained are characterised in terms of their porosity, m icrostructure and mechanical properties. (C) 1999 Elsevier Science Limited. All rights reserved.