Preparation and Properties of Dense SiC/SiC Composites

SiC/SiC composites fabricated by a new process, named Nano-powder Infiltration and Transient Eutectoid (NITE) process has been developed and exhibited attractive thermomechanical properties and gas tightness. For the NITE-SiC/SiC composites, Tyranno Fiber SA and nano-sized SiC powder with certain amounts of sintering aids were employed as the reinforcement and the starting material of matrix, respectively. The NITE-SiC/SiC composites were densified by hot pressing with 20 MPa at 1800°C. In this study, effects of variation of the nano-sized SiC powders on mechanical properties of the NITE-SiC/SiC composites were evaluated. It was found that high specific surface area and carbon rich atomic ratio of the nanosized SiC powder were necessary for the NITE-SiC/SiC composites with high strength and non-catastorophic fracture behavior. Another objective of the study was to develop the near-net shape process and large-scale production process called pseudo-HIP process, which was a new type HIP using a carbon powder as the pressure transmitter and carbon mold with near-net shape cavity. Small and large diameter cylindrical shape (ϕ12/ϕ 10×50 mm, ϕ200/ϕ 194×80 mm) NITE-SiC/SiC composites can be fabricated by the pseudo-HIP process. Hence, the Pseudo-HIP process was found to be a useful process for near-net shape and large-scale NITE-SiC/SiC products.