Abstract: Magnetically attractable particles comprise a core of magnetic material encapsulated in a metal oxide coating. They may be made by emulsifying an aqueous solution or dispersion of the magnetic material or precursor, and an aqueous solution or sol of a coating inorganic oxide or precursor, in an inert water-immiscible liquid. The aqueous droplets are gelled, e.g. by ammonia or an amine, recovered, and heated at 250.degree.-2000.degree. C. The resulting particles are generally smooth spheres below 100 microns in diameter and often of sub-micron size.
Type:
Grant
Filed:
November 29, 1994
Date of Patent:
September 2, 1997
Assignee:
Alfa Biotech SpA
Inventors:
Jean Victor Sang, Paul Groves, Robert Edward Burrell, Gerard Flynn