X-ray diffraction study of nanocrystalline tungsten nitride and tungsten to 31 GPa

X-ray diffraction measurement determined that a newly synthesized nanocrystalline tungsten nitride (W2N) has a substantially larger cell parameter than its bulk material. Yet the lattice of a metal nanocrystalline tungsten (W) remained unchanged. High-pressure diffraction study to 31 GPa resolved a much lower bulk modulus of 240 GPa for nanocrystalline W2N and a relatively unchanged bulk modulus of 307 GPa for nanocrystalline W compared to its bulk material. We found that the metallic bonding of a metal is not affected by reduction of the grain size. The enlarged cell parameter and the relatively low bulk modulus of W2N reflect the size effect of nanocrystalline W2N. (c) 2007 American Institute of Physics.