| abstract |
This specification discloses a process wherein by applying certain controlled homogeneous precipitation techniques in the presence of a homogeneously distributed finely divided particulate supporting material, there is effected a deposition precipitation of a metal or metal compound on the surfaces of the support particles. This deposition precipitation process may be effected in a number of ways, such as by homogeneous changes in the pH of the solution, or decomplexation to an insolubilizable metal ion, or introduction of the metal component to be precipitated, or oxidation or reduction techniques, or by introduction of precipitating ions, etc. The process requires compliance with conditions to substantially avoid any stable free nucleation and crystal development in the solution phase per se, and to cause nucleation and particle formation substantially only at or on the supporting surfaces, which must, therefore, be selected so as to provide a nucleating surface for the component to be precipitated, under the conditions of the reaction. The deposited metal or metal compound is obtained in the form of a thin layer or in the form of discrete very small particles, and, in either form is substantially homogeneously distributed over the said surface, and is further either crystallographically or electrostatically adhered to the support particle. The resulting products may be used as such, or may be treated by subsequent heating, oxidation, or reduction steps to be converted into still further useful products. The materials thus provided are especially valuable for their catalytic activity, and, where ferromagnetic deposited particles are obtained, for their highly advantageous properties derived from the magnetocrystalline anisotropy. |