Method for manufacturing oil-based ferrofluid

摘要

A slurry is formed of particles of a non-magnetic oxide of iron ( alpha -Fe2O3), an oil carrier liquid and a surfactant. The slurry is then processed in an attrition mill where kinetic energy is applied to the slurry to convert the alpha -Fe2O3 particles to magnetic iron oxide particles to form an oil-based ferrofluid. In order to increase the saturation magnetization of the resulting ferrofluid, a beneficial agent is brought into contact with the slurry during processing in the attrition mill. The beneficial agent can be a magnetic material, such as elemental iron, or can be water. A ferrofluid can also be formed by creating a powder of surfactant-coated magnetic particles and using an attrition mill to coat the particles with a second surfactant and suspend the coated particles in a carrier liquid.