KUGELFOERMIGE, HOHLRAUMFREIE FERRITPARTIKELCHEN

1481711 Ferrites XEROX CORP 14 Nov 1974 [12 Dec 1973] 49374/74 Headings C1J and C1A [Also in Division G2] Ferrite (e.g. NiZn and MnZn ferrites or Fe 3 O 4 ) particles which are substantially spherical in shape, continuous in surface area and free of interior voids are made by preparing a slurry of ferrite-forming metal oxides in a liquid, the slurry having a viscosity at 23‹ C of between 55,000 and 140,000 centipoise, spray-drying to form substantially spherical metal oxide beads and sintering. The metal oxides may either be added to the liquid before mixing to form the slurry or may be mixed dry before addition to the liquid to form the slurry. A flow-promoting ingredient (e.g. zirconia or alumina) may be added to the metal oxide beads to prevent bead-to-bead agglomeration and bead-to-furnace-wall sticking. A deflocculent (various acids and salts are exemplified) may be added to the slurry. A binder may also be present in the slurry. Examples describe the preparation of Ni ferrites using a deflocculent in the slurry. The ferrite particles may act as electrostatographic carrier materials, toner particles (of which many are exemplified) being capable of electrostatically clinging thereto.