Preparation of oxidation resistant cobalt oil colloids

In this work a successfully applied method is reported far the preparation of stable colloidal cobalt-based oils. The two-step process comprises therm olysis of a Co-2(CO)(8)-toluene solution in the presence of Na-AOT or lauro ylsarcosin oleic acid followed by an exchange step for the carrier liquid. In this step a second surfactant compatible with the oil carrier was used l eading to a double-layer coating of the Co particles. Magnetic oil-based li quids with a saturation magnetization up to 120 mT could be prepared this w ay. The sedimentation stability in the presence of a strong magnetic field and the oxidation resistance are excellent. (C) 1999 Elsevier Science B.V. All rights reserved.