CONTINUOUS FIBER-REINFORCED MULLITE MATRIX COMPOSITES BY SOL-GEL PROCESSING .1. FABRICATION AND MICROSTRUCTURES

The fabrication of ceramic composites based on a mullite matrix uniaxi ally reinforced with either high strength carbon or Nicalon-SiC contin uous fibres is described. Sets of high solids contents of up to 40 vol % were prepared using colloidal silica sol with either alpha-alumina p owder or colloidal boehmite as reactants for the preparation of the mu llite matrix, 3Al(2)O(3) . 2SiO(2). Single-stage infiltration was used for the preparation of prepregs for laminating into composites. The c omposites were consolidated by uniaxially hot-pressing at 1300 or 1550 degrees C, depending on the matrix precursors and the final phases in the matrix. Highly densified composites with fibre volume fractions o f 32-60% were obtained and the microstructures characterised by mercur y porosimetry, X-ray diffraction, scanning electron microscopy and tra nsmission electron microscopy.