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Particle Size Analysis of Magnetic Powders

IP.com Disclosure Number: IPCOM000094958D
Original Publication Date: 1965-Jul-01
Included in the Prior Art Database: 2005-Mar-06
Document File: 1 page(s) / 12K

Publishing Venue

IBM

Related People

Schwartz, B: AUTHOR [+2]

Abstract

The magnetic properties of a device fabricated from magnetic powders is, in part, a function of the particle sizes of the powders used. For many computer applications, process control over this parameter becomes extremely important. But, owing to the magnetic attraction between individual particles of that ferrite powder, realization of this control is most difficult to achieve. Now a method is provided which circumvents these heretofore-mentioned problems and makes it possible to accurately determine particle sizes of the magnetic powders.

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Particle Size Analysis of Magnetic Powders

The magnetic properties of a device fabricated from magnetic powders is, in part, a function of the particle sizes of the powders used. For many computer applications, process control over this parameter becomes extremely important. But, owing to the magnetic attraction between individual particles of that ferrite powder, realization of this control is most difficult to achieve. Now a method is provided which circumvents these heretofore-mentioned problems and makes it possible to accurately determine particle sizes of the magnetic powders.

The process entails heating a batch of the magnetic powder to a temperature that is above the Curie temperature of the powder. Such changes the properties of the powder from ferri- or ferromagnetic to paramagnetic. For, in the paramagnetic state, the attractive forces decrease sufficiently for the particles to release from each other. The powder, while in the paramagnetic state, is then dispersed in a viscous medium which is maintained above the Curie temperature of the powder.

Classification then proceeds principally upon the basic of Stokes' law of sedimentation. The particles of various sizes, shapes and specific gravities are separated by being allowed to settle in the viscous fluid. The coarser, heavier and rounder particles settle faster than the finer, lighter and more angular ones. Thus, a particle size distribution appears in the viscous medium with the size of the particles...