Doubly-coated iron particles
AssigneeHoeganaes Corporation
InventorsHoward Rutz, Francis G. Hanejko
Life of this patent
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Abstract
Methods of doubly coating iron particles. The methods comprise treating the iron particles with phosphoric acid to form a layer of hydrated iron phosphate at the surfaces of the iron particles. The particles are heated in an inert atmosphere at a temperature and for a time sufficient to convert the hydrated layer to an iron phosphate layer. The particles are then coated with a termoplastic material to provide a coating of thermoplastic material substantially uniformly circumferentially surrounding the iron phosphate layer. Doubly-coated iron particles provided in accordance with this invention are generally useful for forming magnetic components and cores for use in high frequency switching applications.
Claims23
A method of doubly coating iron particles comprising the steps of:
- treating the iron particles with phosphoric acid to form a layer of hydrated iron phosphate at the surface of the iron particles;
- heating the iron particles in an inert atmosphere at a temperature and for a time sufficient to convert the hydrated layer to an iron phosphate layer;
- and
- coating said particles with a thermoplastic material that is a polyethersulfone or a polyetherimide to provide a coating of said thermoplastic material substantially uniformly circumferentially surrounding said iron phosphate layer, wherein sufficient thermoplastic material is used to provide a coating that constitutes from about 0.2% to about 15.0% by weight of the doubly-coated particles.
The method recited in claim 3 or 5 wherein the iron particles have a weight average particle size of 20-200 microns and the thermoplastic material is a polyethersulfone.
A mixture of doubly-coated iron particles for molding high frequency magnetic components wherein said coated iron particles comprise:
- iron core particles having a weight average paticle size of about 20-200 microns;
- a layer of iron phosphate at the surface of the iron core particles;
- and
- a substantially uniform circumferential coating of a thermoplastic material that is a polyethersulfone or a polyetherimide surrounding the iron phosphate layer, said thermoplastic material constituting about 0.2% to about 15.0% by weight of said particles.
The coated particles recited in calim 7 wherein the iron phosphate layer is up to about 0.001% by weight of the doubly-coated particles.
A method of making high frequency magnetic components comprising the steps of:
- (a) providing a mixture of doubly-coated iron particles comprising:
- (1) iron particles;
- (2) a layer of iron phosphate at the surface of the iron particles;
- and
- (3) a coating of a thermoplastic material that is a polyethersulfone or a polyetherimide surrounding the iron phosphate layer, said thermoplastic material constituting about 0.2% to about 15.0% by weight of said doubly-coated particles;
- and
- (b) molding the mixture of doubly-coated iron particles into a magnetic component having a density that is at least about 96.5% of theoretical density.
Dependencies are inferred from the claim text.