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Preparation of High Coercivity Magnetic Particles

IP.com Disclosure Number: IPCOM000094293D
Original Publication Date: 1966-Aug-01
Included in the Prior Art Database: 2005-Mar-06
Document File: 1 page(s) / 11K

Publishing Venue

IBM

Related People

Alberts, GS: AUTHOR [+2]

Abstract

Borate buffered solutions, similar to those used in the preparation of plated material by chemical reduction, are used to prepare magnetic particles having high coercivity. The solution contains cobalt ion, a reducing agent, a complexing agent and a borate buffer to control pH.

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Preparation of High Coercivity Magnetic Particles

Borate buffered solutions, similar to those used in the preparation of plated material by chemical reduction, are used to prepare magnetic particles having high coercivity. The solution contains cobalt ion, a reducing agent, a complexing agent and a borate buffer to control pH.

Decomposition of the bath, with the resulting formation of magnetic particles, is induced by raising the temperature of the bath near the boiling point or by adding finely divided catalytic material, or salts of catalytic material, to the solution. Catalytic materials include cobalt, nickel, iron, platinum, and many other materials. With the advent of spontaneous decomposition, a fine powdered magnetic material is formed.

A typical solution from which magnetic particles are prepared is: CoSO(4) 7H(2)O 25 g Na(3)C(6)H(5)O(7). 2H(2)O 50 g NaH(2)PO(2). H(2)O 50 g Na(2) B(4) O(7) 150 g pH = 9.2.

The resulting powder has a coercivity on the order of about 1100 oersteds. It contains less than 5% phosphorus and exhibits a structure of randomly orientated hexagonal close packed cobalt. Electron micrographs show that the particles are spherical, between 0.5 and 1.5 microns in diameter, and that they tend to form chains with one another.

The size and magnetic properties of magnetic material produced in this manner are varied by controlling bath compositions, temperature of formation, and other bath parameters.

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