High performance magnetorheological fluids: very high magnetization FeCo-FeO nanoclusters in a ferrofluid carrier.

High magnetization FeO/OA-FeCo/AlO nanocomposite magnetic clusters have been obtained using a modified oil-in-water miniemulsion method. These nanocomposite clusters dispersed in a ferrofluid carrier result in a magnetorheological fluid with improved characteristics. The magnetic clusters have a magnetic core consisting of a mixture of magnetite nanoparticles of about 6 nm average size, stabilized with oleic acid (FeO/OA) and FeCo/AlO particles of about 50 nm average size, compactly packed in the form of spherical clusters with a diameter distribution in the range 100-300 nm and a hydrophilic coating of sodium lauryl sulphate surfactant.