Hard-soft magnetic MnBi/SiO2/FeCo nanoparticles

Patent metadata

Field	Value
Publication number	US-9607740-B2
Application number	US-201414270619-A
Country	US
Kind code	B2
Filing date	May 6, 2014
Priority date	May 6, 2014
Publication date	Mar 28, 2017
Grant date	Mar 28, 2017

Abstract

Core-shell-core nanoparticles of an iron-cobalt alloy core, a silica shell and a manganese bismuth alloy core or nanoparticle on the surface of the silica shell (FeCo/SiO 2 /MnBi) are provided. The core-shell-core nanoparticles are alternative materials to rare-earth permanent magnets because of the hard magnetic manganese bismuth in nanometer proximity to the soft magnetic iron cobalt.

First claim

The invention claimed is:

1. A core-shell-core nanoparticle system, comprising:
a superparamagnetic core comprising an iron cobalt alloy;
an intermediate shell of a silicon dioxide coating the core;
an outer core of manganese bismuth alloy on the intermediate silicon dioxide shell; and
a metal silicate interface layer between the superparamagnetic core and the silicon dioxide shell;
wherein
a diameter of the iron cobalt alloy core is 200 nm or less.

2. The core-shell-core nanoparticle system according to claim 1 , wherein a diameter of the MnBi core is from 0.5 to 200 nm.

3. The core-shell-core nanoparticle system according to claim 1 , wherein the metal silicate of the interface layer comprises at least one of iron silicate and cobalt silicate.

4. The core-shell-core nanoparticle system according to claim 1 , wherein the thickness of the metal silicate interface layer is from 0.5 nm to 15 nm.

5. The core-shell-core nanoparticle system according to claim 1 , wherein the superparamagnetic core consists of an iron cobalt alloy.

6. The core-shell-core nanoparticle system according to claim 1 , wherein the diameter of the iron cobalt core is from 2 to 75 nm.

7. A method to prepare a core-shell-core FeCo/SiO 2 /MnBi nanoparticle system, comprising:
co-reducing an iron ion and a cobalt ion from a common solution; and coprecipitating an FeCo alloy nanoparticle to obtain a reduction mixture;
isolating the FeCo nanoparticle from the reduction mix e;
forming a silica coating on the FeCo nanoparticle to obtain a core-shell nanoparticle; and
forming a MnBi alloy nanoparticle on the core-shell nanoparticle by reduction of Bi ions with a Mn and lithium borohydride reducing complex ions to obtain a MnBi alloy nanoparticle on the silica shell.

8. A composition comprising:
a nanoaggregation of FeCo/SiO 2 core/shell nanoparticles with islands of MnBi nanoparticles attached to surfaces of the SiO 2 shells.

Assignees

• Toyota Motor Co Ltd

Inventors

• Rowe Michael Paul
• Desautels Ryan Daniel

Classifications

• B22F1/056

  Submicron particles having a size above 100 nm up to 300 nm · CPC title

• B22F1/054

  Nanosized particles · CPC title

• B22F1/16

  Metallic particles coated with a non-metal (coated with lubricating or binding agents or with organic material B22F1/10) · CPC title

• H01F7/02

  Permanent magnets {[PM]} · CPC title

• C01P2004/64

  Nanometer sized, i.e. from 1-100 nanometer · CPC title