The Effects of Dry Grinding on the Physico-Chemical Properties of NiO Powder

Abstract

The purpose of this study is to obtain the fundamental information of physico-chemical properties of commercial NiO powder in the grinding process. The effects of dry grinding by ball-milling for hundreds of hours on the physico-chemical properties of the powder have been studied by X-ray diffraction, BET adsorption, air permeability, spectroscopic reflection, and some other methods.The following results have been obtained:(1) As the grinding proceeds both the lattice distortion and the surface area determined by BET method increse gradually. During the early stage of grinding, both the crystallite dimension and the surface area determined by permeability method decrese, and the apparent density increases considerablly, but those take almost constant values in further grinding. It is suggested that a non-crystalline substance is not produced by dry grinding.(2) The catalytic activity increases with increasing lattice distortion in the early stage, but increases with increasing surface area determined by BET method in the final stage.(3) The reflection spectra of the ground NiO exhibit characteristic peaks at 420, and 670mμ. In an early stage, the absorption in the range of visible ray increases considerablly.(4) When the ground NiO powders are heated at various temperature for about 3 hours, both the lattice distortion and color tone become nearly the same as the original powder. Then occur both loss in weight on heating and increase in crystallite dimension.