1) Near-net shape forming of preform by PIM
Our speciality on the fabrication of ceramic preform is the application of powder injection molding (PIM) technology. PIM is a near-net shape forming technology, which is suitable for producing small parts with complex shape and high content (>50%, volume fraction) of reinforcement. It is possible to accurately adjust the volume fraction and particle size of reinforcement. PIM involves three steps. Firstly, the feedstocks for PIM are produced by mixing SiC powder and the binder in the double planetary mixer in the temperature range of 135–160 °C. Secondly, the preforms are injected under the pressure of 60–80 MPa. Thirdly, molded preforms are subjected to debinding and pre-sintering. Figure 1(a) shows SiC preform fabricated by PIM. Figures 1(b), (c) and (d) indicate SiCp/Al, SiCp/Cu and diamond/Cu composites fabricated by the combination of powder injection molding and pressureless infiltration, respectively. Figure 2 shows the microstructures of SiCp/Al, SiCp/Cu, diamond/Cu and Cf/Cu composites. It is seen that the distribution of reinforcement is uniform and high volume fraction is achieved. As for SiC/metal composites, interfacial reaction is restricted (Figs. 2(b) and (d)) by alloying matrix. In the case of diamond/metal and C/metal composites, Ti-coated diamond (Fig. 2(f)), Ni-coated diamond (Fig. 2(g)) and Mo-coated carbon fiber (Fig. 2(h)) are used in order to ameliorate the interfacial bonding.