Elastic moduli and strength of nanocrystalline cubic ${\text{BC}}_{2}\text{N}$ from x-ray diffraction under nonhydrostatic compression

Elastic moduli and strength of nanocrystalline cubic ${BC}_{2} N$ from x-ray diffraction under nonhydrostatic compression

Haini Dong, Duanwei He, Thomas S. Duffy, and Yusheng Zhao

Phys. Rev. B 79, 014105 – Published 9 January 2009

Abstract

The stress behavior of nanocrystalline cubic boron carbon nitride $(c {-BC}_{2} N)$ was investigated using radial and axial x-ray diffractions in the diamond-anvil cell under nonhydrostatic compression up to ~100 GPa. The radial x-ray diffraction (RXRD) data yield a bulk modulus $K_{0} = 276 \pm 20 GPa$ with a fixed pressure derivative $K_{0}^{'} = 3.4$ at $ψ = 54.7 °$ , which corresponds to the hydrostatic compression curve. The bulk modulus obtained from axial x-ray diffraction (AXRD) gives a value of $420 \pm 11 GPa$ . A comparative study of the observed compression curves from radial and axial diffractions shows that the ruby-fluorescence pressure scale may reflect the maximum stress under nonhydrostatic compression. It was found that nanocrystalline $c {-BC}_{2} N$ sample could support a maximum differential stress of ~38 GPa when it started to yield at ~66 GPa under uniaxial compression. Moreover, the aggregate elastic moduli of the nanocrystalline $c {-BC}_{2} N$ have been determined from the RXRD data at high pressures.