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THE PASSIVATION OF COLLOIDAL IRON DISPERSIONS

IP.com Disclosure Number: IPCOM000024459D
Original Publication Date: 1980-Aug-31
Included in the Prior Art Database: 2004-Apr-02
Document File: 2 page(s) / 52K

Publishing Venue

Xerox Disclosure Journal

Abstract

Disclosed is a process to retard the surface oxidation of colloidal iron particles involving solubilizing inorganic passivators such as potassium nitrates and potas-sium chromates in an organic dispersion medium by the use of the crown ether "18 crown 6" as a complexing agent. The passivators increase the stability of the natural passive oxide film on colloidal iron particles and suppresses the formation of Beta iron oxide hydroxide (FeOOH). Colloidal iron dispersions have potential applications in numerous imaging and recording systems including magnetic inks, magnetic recording devices and magnetic pigments. In one important embodiment, these particles have a high initial permeability and are therefore attractive as the magnetic component of magnetic toners and carriers. Such particles produced by prior art methods have been shown to be unstable to atmospheric oxidation, which results in the formation of iron oxides and oxyhydroxides with low magnetic moments. The process disclosed herein eliminates such problems.

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XEROX DISCLOSURE JOURNAL

THE PASSIVATION OF COLLOIDAL IRON DISPERSIONS U.S. C1. 430/644 Clifford H. Griffiths

Pro posed Classification

Int. C1. G03c 1/02

Michael P. O'Horo
Thomas W. Smith

Disclosed is a process to retard the surface oxidation of colloidal iron particles involving solubilizing inorganic passivators such as potassium nitrates and potas- sium chromates in an organic dispersion medium by the use of the crown ether "18 crown 6" as a complexing agent. The passivators increase the stability of the natural passive oxide film on colloidal iron particles and suppresses the formation of Beta iron oxide hydroxide (FeOOH). Colloidal iron dispersions have potential applications in numerous imaging and recording systems including magnetic inks, magnetic recording devices and magnetic pigments. In one important embodiment, these particles have a high initial permeability and are therefore attractive as the magnetic component of magnetic toners and carriers. Such particles produced by prior art methods have been shown to be unstable to atmospheric oxidation, which results in the formation of iron oxides and oxyhydroxides with low magnetic moments. The process disclosed herein eliminates such problems.

Volume 5 Number 4 July/August 1980 473

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