Magnetizable colloids on strongly polar carriers -: preparation and manifold characterization

The aim of this paper is to present methods applied to obtain and to investigate the properties of magnetic fluids on strongly polar carrier liquids, such as short-chain-length alcohols and water. The high degree of colloidal stability of these colloids is achieved by double-layer sterical stabilization of Fe2O3 and CoFe2O4 nanoparticles dispersed in the carrier liquid, the adequate choice and efficient adsorption of the surfactant(s) used being one of the key problems to be solved in each particular case, in order to obtain high-quality magnetic fluids. The samples were investigated using a vibrating-sample magnetometer, a rheo/magnetorheometer with various measuring cells, as well as by small-angle neutron scattering, in order to detect magnetic-field-induced changes at the nanometric level and qualitative differences in the macroscopic behaviour of various samples. The conclusions refer to the dependence of the colloidal stability on the composition and volumic concentration of the magnetic fluid samples, as well as on the applied magnetic field.