Patents Examined by Mark A. Formos
  • Acicular cobalt-modified iron oxides and their preparation
    Patent number: 5183709
    Abstract: Acicular, cobalt-modified iron oxides consisting of a core of an iron oxide of the formula FeO.sub.x where x is from 1.33 to 1.5 and a ferrite shell which contains a total amount of from 0.4 to 12% by weight of cobalt ions and not more than 5% by weight of iron(II) ions, the percentages being based on the total amount of the material, which iron oxides have improved aging resistance, particularly with regard to the coercive forces, and a process for their preparation.
    Type: Grant
    Filed: May 21, 1990
    Date of Patent: February 2, 1993
    Assignee: BASF Aktiengesellschaft
    Inventors: Ekkehard Schwab, Ronald J. Veitch, Helmut Auweter