Effect of hydrodynamic size on colloidal stability and lifetime of Mn-Zn magnetic fluids

For transformer cooling applications, magnetic particles need to be dispersed in carrier fluids with high colloidal stability for a long period without significant degradation. However, stability of the suspension, especially the long term colloidal stability is a crucial factor for the applications in power transformers because aggregation of particles could cause clogging of micro-channels in transformers. In this article, we have reported effect of hydrodynamic size on the colloidal stability of Mn 1-x Zn x Fe 2 O 4 (MZ) nanoparticles (NPs)–based magnetic fluids. Lifetime of fluids has been determined from the increase in hydrodynamic size of magnetic NPs due to aggregation. Colloidal stability of fluids decreases with increase in the polydispersity of fluids caused by the enhanced dipole interactions between NPs resulting in the aggregation of NPs in chain-like structures. Graphic Chain formation in magnetic nanoparticles in fluids due to aging