MANUFACTURE OF FERROMAGNETIC POWDER FOR MAGNETIC RECORDING

摘要

PURPOSE:To improve dispersibility in a binder and stability against oxidization by a method wherein an alkaline suspension is obtained by adding a silicate to ferromagnetic powder obtained by liquid phase reduction and the suspension is neutralized by carbon dioxide gas or the like to form a silicon oxide film on the surface of a metal powder particle. CONSTITUTION:Ferromagnetic metal powder is obtained by reduction in the solution from the solution of a ferromagnetic metallic salt such as a sulfate or a nitrate of metals such as Co or Ni or their alloys. A water-soluble silicate such as ortho-sodium silicate or meta-pottasium silicate is added to the ferromagnetic metal powder to compose an alkaline suspension. The alkaline suspension is neutralized by adding an acid such as carbon dioxide gas or an inorganic acid to form a silicon dioxide film on the particle surface of the metal powder. With this constitution, cohesion of the particles caused by deformation of needle shape during dispersion is avoided and the powder is dispersed well in a binder and has an excellent stability against oxidization.