Process for preparing magnetic iron oxide and magnetic iron oxide produced thereby
First Claim
1. A process for preparing magnetic iron oxide, which comprises,(a) coating the surface of needle-like particles of magnetic iron oxide with a cobalt compound, said iron oxide having the formula FeOx wherein x is from about 1.36 to 1.49,(b) placing the coated iron oxide particles in a unidirectionally oriented magnetic field of at least about 300 Oe, thereby to orient most of the needle-like particles in the direction of said magnetic field,(c) heat-treating said needle-like particles at a temperature of from about 200°
- to 800°
C., in an atmosphere of inert gas, and(d) conducting said heat treating while said needle-like particles are in a magnetized state or, if said needle-like particles are not in a magnetized state, then conducting said heat treating while simultaneously applying an external magnetic field to said needle-like particles.
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Abstract
A magnetic iron oxide having a large coercive force and an improved squareness ratio prepared by coating the surface of needle-like particles of magnetic iron oxide with a cobalt compound, placing the coated iron oxide particles in a unidirectionally oriented magnetic field thereby orienting the particles in the direction of the magnetic field, and heat-treating the needle-like particles in this state with the application of an external magnetic field, or heat-treating the needle-like particles in a magnetized state.
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Citations
10 Claims
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1. A process for preparing magnetic iron oxide, which comprises,
(a) coating the surface of needle-like particles of magnetic iron oxide with a cobalt compound, said iron oxide having the formula FeOx wherein x is from about 1.36 to 1.49, (b) placing the coated iron oxide particles in a unidirectionally oriented magnetic field of at least about 300 Oe, thereby to orient most of the needle-like particles in the direction of said magnetic field, (c) heat-treating said needle-like particles at a temperature of from about 200° - to 800°
C., in an atmosphere of inert gas, and(d) conducting said heat treating while said needle-like particles are in a magnetized state or, if said needle-like particles are not in a magnetized state, then conducting said heat treating while simultaneously applying an external magnetic field to said needle-like particles. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
- to 800°
Specification