Towards ferrofluids with enhanced magnetization

It is well known that the saturation magnetization of a sterically stabilized magnetic fluid (ferrofluid) is limited by the presence of a surfactant coating on the surface, and in some cases, by an effectively demagnetized surface layer in the solid magnetic particle. These surface layers take up a disproportionate volume in the colloidal dispersion there by severely limiting the volume fraction of the core magnetic substance. This work proposes and analyzes Janus particles having the objective of increasing the magnetic loading beyond the present day constraints. Using numerical computation of the virial coefficient it is calculated that the magnetic volume fraction of magnetite ferrofluids might be increased by a factor approaching 2 and that of iron-based ferrofluids by a factor of 3. (C) 2010 Elsevier B.V. All rights reserved.