Evolution of microstructure of niobium carbide NbC0.77 powders
The microstructural evolution of annealed nonstoichiometric niobium carbide NbC0.77 powders subjected to high energy ball milling has been investigated by time of flight (TOF) high resolution neutron diffraction. The diffraction patterns have been collected with the high resolution Fourier diffractometer HRFD by using the TOF mode of data acquisition. The nanocrystalline powders produced by high energy milling have an inhomogeneous microstructure, in which two fractions with different particle size and composition can be identified. The average sizes of the coherent scattering regions and microstrains in nanocrystallites with allowance for the anisotropy of the deformation distortions have been estimated. It is shown that TOF neutron diffraction patterns can provide the very accurate data for microstructure analysis of nanocrystalline powders. No superstructure has been observed in the annealed NbC0.77 carbide.