Patent ID: 9378876
Filing Date: 2016-06-28
CPC Classification: B22F,C01B,C01P,C22C,H01F

Claim Text:
1. A process for producing ferromagnetic particles comprising an Fe 16 N 2 compound phase in an amount of not less than 80% as measured by Mössbauer spectrum, and each having an outer shell in which FeO is present in the form of a film having a thickness of not more than 5 nm, the process comprising the steps of: subjecting iron oxide or iron oxyhydroxide having an average major axis diameter of 40 to 5000 nm and an aspect ratio (major axis diameter/minor axis diameter) of 1 to 200 as a starting material to dispersing treatment to prepare aggregated particles having D50 of not more than 40 μm and D90 of not more than 150 μm; allowing the obtained aggregated particles to pass through a mesh having a size of not more than 250 μm; subjecting the iron compound particles passed through the mesh to hydrogen reducing treatment at a temperature of 160 to 420° C.; and then subjecting the resulting particles to nitridation treatment at a temperature of 130 to 170° C.