Fabrication of co-continuous SiC/Al composites from novel SiC preforms with high porosity and controllable pore size

The preparation of porous SiC ceramics is the key process for co-continuous SiC/Al composites, which are promising materials for electronic packaging and precision instrument. Porous ceramics prepared by mould pressing and freeze casting are the most widely used preforms. However, the former preforms own high solid loading, raising the machining difficulty of composites. The latter preforms possess nonuniform microstructure, which is inappropriate for precision instruments. In this work, SiC preforms with low solid loading and uniform microstructure were prepared by non-aqueous gelcasting. Moreover, the pore size of the preforms could be controlled easily (1.03-22.82 mu m) by changing the raw powder size. The effects of preform pore size on the mechanical properties and thermal expansion coefficient of the composites were researched. When the preform with a proper pore size of 7.14 mu m was applied, the flexural strength and thermal expansion coefficient of the composite were 986.8 MPa and 8.11 x 10(-6)/K (50 degrees C), respectively.