Fabrication of Cu-30 vol% SiC Composites by Pressureless Sintering of Polycarbosilane Coated SiC and Cu Powder Mixtures

Cu-30 vol% SiC composites with relatively densified microstructure and a sound interface between the Cu and SiC phases were obtained by pressureless sintering of PCS-coated SiC and Cu powders. The coated SiC powders were prepared by thermal curing and pyrolysis of PCS. Thermal curing at 200 degrees C was performed to fabricate infusible materials prior to pyrolysis. The cured powders were heated treated up to 1600 degrees C for the pyrolysis process and for the formation of SiC crystals on the surface of the SiC powders. XRD analysis revealed that the main peaks corresponded to the alpha-SiC phase; peaks for beta-SiC were newly appeared. The formation of beta-SiC is explained by the transformation of thermally-cured PCS on the surface of the initial alpha-SiC powders. Using powder mixtures of coated SiC powder, hydrogen-reduced Cu-nitrate, and elemental Cu powders, Cu-SiC composites were fabricated by pressureless sintering at 1000 degrees C. Microstructural observation for the sintered composites showed that the powder mixture of PCS-coated SiC and Cu exhibited a relatively dense and homogeneous microstructure. Conversely, large pores and separated interfaces between Cu and SiC were observed in the sintered composite using uncoated SiC powders. These results suggest that Cu-SiC composites with sound microstructure can be prepared using a PCS coated SiC powder mixture.