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 with 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-pressing. Emphasis is given to the preparation of-a single-step-firing matrix powder leading to dense composites. Three-point flexural strengths have 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 Science Limited