Processing of Ceramic Matrix Composites

Abstract

The main processing techniques used to fabricate ceramic matrix composites (CMCs) with continuous fibers are reviewed. They involve liquid or gas phase routes, the starting material often being a fiber preform. In the reactive melt infiltration processes, the preform is densified with a liquid (Al or Si) reacting with the preform or the atmosphere (O{sub 2} or N{sub 2}). The polymer impregnation/pyrolysis as well as the slurry impregnation/hot pressing processes are based on techniques previously utilized for polymer matrix composites or/and monolithic ceramics. In the gas phase routes, or chemical vapor infiltration (CVI), the fiber preform is densified with the matrix, which is formed in-situ as the result of chemical reactions involving a gaseous precursor. When performed under isothermal/isobaric conditions (I-CVI) at low temperatures and pressures, the process is slow but highly flexible. The densification rate is significantly improved when a temperature gradient or/and a pressure gradient (F-CVI) are applied to the preform. Finally, pressure-pulsed CVI (P-CVI) is a unique technique for the fabrication of composites with highly engineered interphases or matrices. (orig.) 40 refs.