HIP production of a diamond/SiC composite and application to high-pressure anvils

Using a hot isostatic pressing (HIP) technique, sintering of diamond/SiC composites was performed. At an HIP condition of 1450 °C and 200 MPa, a pressure much lower than that of the diamond stability field, the formation of well-sintered diamond/SiC composites was confirmed. No trace of graphite was observed. An application of the composite to high-pressure anvils was attempted. Cubes of the composites were used as the second stage anvils in a Kawai-type high-pressure apparatus. Because the diamond/SiC composites are transparent to X-rays, diffraction patterns of NaCl powder compressed in the high-pressure apparatus were successfully recorded through the anvils and thereby the generated pressures were determined using the equation of state of NaCl. The anvils were proved to be hard enough for the generation of pressures up to 30 GPa. The present anvils will be applicable not only to diffraction but also to radiographic studies under pressure, since almost the entire part of the high-pressure cell can be observed with the X-ray beam.