Abstract :
Biomorphic C/SiC composites were fabricated from different kinds of wood by
liquid silicon infiltration (LSI) following a two-step process. In the first-step, the wood is
converted into carbon preforms by pyrolysis in a nitrogen atmosphere. The carbon preforms
are then infiltrated by silicon melt at 1,560◦C under vacuum to fabricate C/SiC composites.
The mechanical properties of the C/SiC composites were characterized by flexural tests at
ambient temperature, 1,000, and 1,300◦C, and the relationship between mechanical properties
and microstructure was analyzed. The flexural strength of the biomorphic composites
was strongly dependent on the properties of the carbon preforms and the degree of silicon
infiltration. The flexural strength increased with increasing SiC content and bulk density of
composite, and with decreasing porosity in the C/SiC composite. An analysis of fractographs
of fractured C/SiC composites showed a cleavage type fracture, indicating brittle fracture
behavior.
