Production of acicular magnetic iron oxides
AssigneeToda Kogyo Corporation
InventorsYosiro Okuda, Nanao Horiishi, Hiroshi Sumita, Tosiharu Harada
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Abstract
In the production of acicular ferromagnetic iron oxide of highly uniform particle size by oxidizing an iron (II) hydroxide suspension at a pH of at least 11 with an oxygen-containing gas to form acicular iron (III) oxide hydroxide, reducing and optionally further reoxidizing this into ferromagnetic iron oxide, the improvement which comprises providing the iron (II) hydroxide suspension with a water-soluble silicate in an amount of less than 1.7% by atom based on the amount of the iron (II) hydroxide in the suspension and calculated as the ratio of Si to Fe (II) while prior to the oxidation of the suspension with the oxygen-containing gas.
Claims17
In the production of acicular ferromagnetic iron oxide of highly uniform particle size by oxidizing an iron (II) hydroxide suspension at a pH of at least 11 with an oxygen-containing gas to form acicular iron (III) oxide hydroxide, and reducing said acicular iron (III) oxide hydroxide into ferromagnetic iron oxide, the improvement which comprises:
- prior to the oxidation of said suspension with said oxygen-containing gas, providing said iron (II) hydroxide suspension with a water-soluble silicate in an amount of 0.1-1.7 atomic % based on the amount of the iron (II) hydroxide in the suspension and calculated as the ratio of Si to Fe (II).
In the production of acicular ferromagnetic iron oxide of highly uniform particle size and large length-to-width ratio by oxidizing an iron (II) hydroxide suspension at a pH of at least 11 with an oxygen-containing gas to form acicular iron (III) oxide hydroxide, and reducing said acicular iron (III) oxide hydroxide into ferromagnetic iron oxide, the improvement which comprises:
- prior to the oxidation of said suspension with said oxygen-containing gas, providing said iron (II) hydroxide suspension with a water-soluble silicate and zinc compound in amounts between 0.1-1.7 atomic % and 0.1-2.3 atomic % based on the amount of the iron (II) hydroxide in the suspension and calculated as the ratio of Si or Zn to Fe (II) respectively, the ratio of Si plus Zn to Fe (II) being in the range of 0.3-2.5 atomic %.
Dependencies are inferred from the claim text.