NEW SOL-GEL MATRICES OF CHEMICALLY STABLE COMPOSITES OF BAS, NAS AND CAS

The preparation of ceramic-matrix composites made with celsian (BAS), anorthite (GAS), and amorphous albite (NAS) matrices and reinforced wi th Nicalon(R) NLM202 SiC woven fibers is reported. The method used to make composites is a three stage sol-gel process: (i) in situ gelation of-a mixture of alkoxides in a ceramic fibre fabric; (ii) deposit of a matrix precursor onto the impregnated fabrics; and (iii) hot-pressin g. Emphasis is given to the preparation of-a single-step-firing matrix powder leading to dense composites. Three-point flexural strengths ha ve been determined. The matrix and fibre corrosion by proton or sodium ions is discussed. The BAS matrix presents a good compromise between chemical, mechanical and manufacturing criteria. (C) 1996 Elsevier Sci ence Limited