| 简介 |
PROBLEM TO BE SOLVED : To provide an extremely useful rare-earth magnet used as a bond magnet in a high-temperature, high-humidity environment, which is excellent in oxidation resistance and maintains its magnetic properties.
SOLUTION : A method of manufacturing silica-coated rare-earth magnetic powder comprises a process of dispersing rare-earth magnetic powder in a solution including a hydrolytic catalyst, water, and a hydrophilic organic solvent, and of mixing a solution including a Si-containing compound into the dispersion solution so that the maximum deposition rate of a silica film is ≤50 nm/hr. The rare-earth magnetic powder has a multilayer coating consisting of silica thin films, each of which has a thickness of 0.5 nm to 5 nm, and has an average particle diameter of 0.1 μm to 20μm. When six hours have passed at a temperature of 50°C since the silica-coated rare-earth magnetic powder was mixed into water, the volume of hydrogen gas generated by one gram of the magnetic powder is ≤5 cm3.
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