Processing and evaluation of RBSN composite containing SiC filaments

摘要

Ceramics are candidate materials for a number of future civil and military applications. These applications include advanced gas turbines for aeroengines, advance diesel engines, land-based gas turbines and hypersonic vehicles. Ceramic compositesincorporate secondary ceramic phases within a ceramic matrix to improve the overall toughness and reliability. In designing and developing new ceramic matrix composite systems, other concurrent technologies must be advanced in parallel. One of the mostimportant is processing technology. The materials must be produced in a uniform and repeatable manner. This report outlines progress made in the fabrication of reaction bonded silicon nitride, (RBSN)-based composites, incorporating continuous siliconcarbide (SiC) filaments. A processing route has been determined which utilises equipment and techniques developed to give accurate and uniform control of fibre spacing. The process involves composite sheet fabrication by tape casting silicon powderslurries over aligned silicon carbide filaments. Sheets are stacked to form a green block which then undergoes drying, debinding and nitriding. Optical and electron optical evaluation of the composites is carried out to assess the processing route.Mechanical behaviour is also investigated via four-point flexure testing to provide comparisons with monolithic RBSN. The conclusions reached relate to the suitability and wider applicability of this process to fabricate aligned fibre, ceramic matrixcomposites.