Effect of Lattice Strain on Measured Thermal Properties of Fe Nanoparticles - An X-ray Diffraction Study

Abstract

In this paper, nano Fe particles have been produced by ball milling process. Fe powder was ball milled in an argon inert atmosphere Ball milling was carried out for the total duration of 20 hours. The sample was taken out after every 4 hours of milling and it was characterized for its particle size, lattice strain, and Debye-Waller factor, root mean square amplitudes of vibration by X-ray powder diffraction. The high-energy ball milling of Fe after 20 hours resulted in particle size of 39.44 nm and lattice stain 0.68 Lattice strains in Fe powder produced by milling have been analyzed by X-ray powder diffraction. The lattice strain (ε) and Debye-Waller factor (B) are determined from the half-widths and integrated intensities of the Bragg reflections. Debye-Waller factor is found to increase with the lattice strain. From the correlation between the strain and effective Debye-Waller factors have been estimated for Fe. The variation of energy of vacancy formation as a function of lattice strain has been studied. The lattice strain (ε) and Debye-Waller factor (B) are determined from the half-widths and integrated intensities of the Bragg reflections. In Fe, 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 Fe. The variation of energy of vacancy formation as a function of lattice strain has been studied. As grinding time increases energy of vacancy formation decreases. However, the milling produces lattice strain and also enhances the effective Debye-Waller factor. By an extrapolation of the plot between the Debye-Waller factor and the lattice strain, the zero strain Debye-Waller factors are obtained for Fe. The variation of energy of vacancy formation as a function of lattice strain has been studied.