Preparation and characterization of silicon oil based ferrofluid

Stable silicon oil based ferrofluid was prepared in the present investigation. Silicon oil surfactant ethoxy terminated polydimethylsiloxane was used to modify the Fe(3)O(4) nanoparticles. The Fe(3)O(4) nanoparticles were firstly coated with a SiO(2) layer by the hydrolysis of tetraethoxysilane. Then using the active hydroxyl groups on the surface of the SiO(2), silicon oil surfactant was covalently grafted onto the Fe(3)O(4) nanoparticles surface. The ethoxy terminated polydimethylsiloxane has similar molecular chain structure and good compatibility with that of the carrier liquid, thus ensuring stable dispersion of modified Fe(3)O(4) in the carrier silicon oil. The interaction between Fe(3)O(4) and the modifier was characterized by IR and XPS. The crystal structure and the magnetic properties of the Fe(3)O(4) nanoparticles were determined by XRD and VSM, respectively. The size and morphology of the particles were observed using TEM. The properties of the silicon oil based ferrofluid were characterized by Gouy magnetic balance. The results indicated that the ferrofluid had high magnetism and good stability. The rheological properties and thermostability of the ferrofluid were also investigated. (C) 2011 Elsevier B.V. All rights reserved.