X-Ray determination of crystallite size and effect of lattice strain on the Debye-Waller factors of Ni nano powders usig high energy ball mill

Abstract

The synthesis of Ni nanocrystalline powder by high-energy ball milling has been investigated. Ni  powders were ball milled in an argon inert atmosphere. The milled powders were characterized by X-ray diffraction and scanning electron microscopy measurements. The high-energy ball milling of Ni after 12hours resulted in crystalline size of about 48 nm The lattice strains in nickel (Ni) powders produced by milling have been analyzed by X-ray powder diffraction. The lattice strain (e) and Debye-Waller factor (B) are determined from the half-widths and integrated intensities of the Bragg reflections. In Ni the Debye-Waller factor is found to increase with the lattice strain. From the correlation between the strain and effective Debye-Waller factor, the Debye-Waller factors for zero strain have been estimated for Ni. The variation of energy of vacancy formation as a function of lattice strain has been studied.

Keywords: X-ray diffraction, lattice strain, crystallite size, Debye-Waller factor, vacancy formation energy