HIP production of diamond/SiC composites and their application to high-pressure anvils

Abstract

Using a hot isostatic pressing (HIP) technique, diamond/SiC composites were synthesized from diamond and Si powders. At an HIP condition of 1450 oC and 100 MPa, a pressure much lower than that of the diamond stability field, diamond powders react with molten Si to form well-sintered diamond/SiC composites. Cubes of the composites with 15 mm edge length were thereby fabricated, and an application to the second stage anvils in a Kawai-type high-pressure apparatus was attempted. The anvils were proved to be hard enough for the generation of pressures up to 30 GPa. For high-pressure and high-temperature in-situ X-ray experiments using synchrotron radiation, a hybrid anvil system using 4 cubes of the composites and 4 of conventional WC was introduced and heating experiments up to 1600 oC at 20 GPa became possible. Because the diamond/SiC composites are transparent to X rays, the present system is applicable not only to diffraction studies but also to radiographic studies that need a larger window for an X-ray image.