Ferrite powder of consistent good quality and homogeneity is obtained by using nitric acid to form solutions of the nitrate of each of the metals involved, mixing the solutions in the requisite proportions, and decomposing the mixture by spray deposition on the hot surface of an agitated bed of granular material identical with the decomposition product while avoiding any accumulation of liquid, and then calcining the obtained oxide mixture to obtain ferrite powder with a desired proportion of ready-formed ferrite. The nitrous gases formed during solution and decomposition are used for the reconstitution of nitric acid, the tail gas of the reconstitution system being preferably contacted with an aqueous suspension of a basic oxide of a constituent metal of the ferrite, whereafter nitric acid is added to form the required nitrate solution of the constituent metal.
This application is a continuation-in-part of our co-pending Application Ser. No. 746,233 filed July 19, 1968, now abandoned, which itself is a continuation-in-part of our Application Ser. No. 719,878 filed Apr. 9, 1968, now abandoned.
Methods of manufacturing a composite ferrite of two or more of metal oxides prepared from a chloride solution containing ions of these metals, one of the metals being zinc. The methods comprise (a) ejecting a high temperature gas to the solution or atomizing the solution and (b) supplying the atomized gas to a combustion gas containing oxygen, to evaporate moisture from mist particles of the solution in a short period of time so that the zinc chloride in the solution is not substantially evaporated and to induce a heat decomposition or chemical reaction for the remaining metal salt particles, thereby forming a composite ferrite.
Nitric acid is added to an aqueous solution of organic acid salts of metals to be included in a resulting complex oxide powder, into which an aqueous solution of an inorganic salt of other metal component has been incorporated according to need, and the resulting solution is heated until the organic acid salts are decomposed and the decomposition product is heated, whereby a intended complex powder which is very fine and highly bulky and has a large specific surface area is obtained.
