The effect of high energy ball milling on the crystal structure of GDNi(5)

X-ray powder diffraction was used to determine the effect of, dry, in air p erformed high energy ball milling, on the intermetallic compound GdNi5. It was found that the crystal structure of GdNi5 is not stable. At the early s tage of milling (up to after 10 h of milling) the gadolinium component oxid ises causing thus the decomposition of GdNi5 into monoclinic Gd2O3 and meta llic nickel. Both. the crystallite (grain) size and the particle size of po wder decrease during the early stage of milling. At the later stage of mill ing (up to 50 h) the nickel phase from the mixture of Gd2O3 and nanocrystal line nickel oxidises into nanocrystalline NiO. Therefore, the final product after 150 h of milling of GdNi5 is a mixture of oxides of the constituent metals. i.e., amorphous Gd2O3 and nanocrystalline NiO. Traces of contaminat ion by alpha -SiO2 have been observed in the milled powder, being more pron ounced as the milling process proceeds. This is ascribed to the wear effect of agate milling assembly. (C) 2001 Elsevier Science B.V. All rights reser ved.