NiO, ZnOおよびCaCO₃粉末の構造に及ぼす摩砕効果

抄録

It is the purpose of this study to obtain the fundamental information of physico-chemical properties of commercial NiO, ZnO and CaCO₃ powders in the grinding process. The effects of dry grinding by ball-milling for hundreds of hours on the structure of the powders have been studied by X-ray diffraction, spectroscopic reflection, and some other methods.
The following results have been obtained.
(1) During the early stage of grinding, the crystallite dimension of these powders decreases considerablly, but in further grinding it maintains almost constant value between 400∼700Å which is independent of the crystallite dimension of the original powders.
(2) In the early stage of grinding, the lattice distortion of these powders increases with the decreasing crystallite dimension, but a structural disordering on the surface and in the interior is increasing gradually during the further stage of grinding.
(3) As the grinding proceeds, no non-crystalline substance is produced in NiO particles. Considerable decrease in crystallinity occurs only on the surface of a CaCO₃ particles in the early stage of grinding, but gradual decrease in crystallinity occurs from the surface of ZnO particles towards the interior as the grinding proceeds.
(4) As the lattice distortion increases, the catalytic activity of the ground NiO increases correspondingly, but that of the ground ZnO decreases.
(5) The absorption in the visible region of the reflection spectrum of ZnO powder increases considerablly as the grinding proceeds, and the change of the spectrum is similar to that of NiO powder.
When the ground powder is heated at various degrees of temperature for about 3 hours, the reflection spectrum of NiO powder becomes perfectly the same as the original powder, but that of ZnO powder is imperfect. It seems reasonable to conclude that the phenomenon with the ZnO powder depends on the change in crystallinity.