High pressure ultrasonic and x-ray studies on monolithic SiC composite

The equation of state (pressure-volume relationship) of a monolithic SiC composite has been determined separately by high pressure ultrasonic and x-ray techniques. The ultrasonic measurements were performed on a cylindrical specimen, 2.2 mm in diameter and 2.2 mm in length, in a large-volume uniaxial split cylinder press to 13.6 GPa. The synchrotron measurements were carried out on the polycrystalline sample loaded in a diamond anvil cell up to a pressure of 27 GPa. The room temperature bulk modulus obtained from the ultrasonic measurements is K-0=216.5+/-1.1 GPa and the pressure derivative is K-0'=4.19+/-0.09. The shear modulus obtained is G(0)=196.7+/-0.7 GPa with its pressure derivative G(0)'=0.95+/-0.03. Using K-0(') obtained from the ultrasonic measurements in the Birch-Murnaghan equation to fit the synchrotron x-ray data, we obtain a bulk modulus of K-0=218.4+/-4.9 GPa for the composite. (C) 2004 American Institute of Physics.