a1 Department of Physics and Astronomy, Texas Christian University, Fort Worth, Texas 76129
a2 Department of Solid State Physics, Eötvös University, Budapest H-1518, Hungary
a3 Department of General Physics, Eötvös University, Budapest H-1518, Hungary
a4 Institute for Superhard Materials of the NAS of Ukraine, Kiev 02074, Ukraine
A high-pressure silicon infiltration technique was applied to sinter diamond–SiC composites with different diamond crystal sizes. Composite samples were sintered at pressure 8 GPa and temperature 2170 K. The structure of composites was studied by evaluating x-ray diffraction peak profiles using Fourier coefficients of ab initio theoretical size and strain profiles. The composite samples have pronounced nanocrystalline structure: the volume-weighted mean crystallite size is 41–106 nm for the diamond phase and 17–37 nm for the SiC phase. The decrease of diamond crystal size leads to increased dislocation density in the diamond phase, lowers average crystallite sizes in both phases, decreases composite hardness, and improves fracture toughness.
(Received March 11 2004)
(Accepted June 04 2004)