Large-scale ceramic composite structures via near-net-shape processing of carbon preforms

摘要

Processing of ceramic matrix composites (CMC) presented in this article is based on the conversion of porous carbon preforms into C/SiC-ceramics by reaction infiltration of liquid silicon. For the processing itself as well as for the materials properties of the derived composites, microstructure and architecture of the used preforms play a key role. Composites are fabricated by starting from chopped, carbon short fiber reinforced carbons (C/C) which are machined by conventional CNC milling. Accordingly, very complex component geometries can be shaped. After subsequent reaction infiltration by a silicon melt, silicon carbide (SiC) is formed. In the as-processed composites, remnants of unreacted carbon as well as excess silicon are also present. The infiltration process is accompanied by no significant volume change. This near-net-shape feature allows to fabricate comparatively large components. At the same time also very thin-walled, light-weight structures can be processed. Furthermore, the near-net-shape character of the process allows a joining technique to be applied for the fabrication of multi-segmented components. This contribution presents C/SiC composites for specific applications that are derived from different types of carbon/carbon starting materials. Examples include large-dimensioned optical light-weight structures, large retorts for processing of metals and tube components to be used in combustion technology.