SURFACTANT-COATED PARTICLES IN MAGNETIC FLUIDS - CHARACTERIZATION ANDSTUDY OF THERMAL-STABILITY UNDER INERT ATMOSPHERE

In this paper is described a simple and quick process, based on phase separation, leadind to a magnetic fluid composed of magnetite nanopart icles dispersed in cyclohexane using oleic acid as surfactant. This fl uid and the solid particles were characterized using several technique s : magnetization curve, Xray diffraction, electronic microscopy and c hemical analysis. ; Study of thermal stability of the surfactant coate d particles under inert athmosphere shows that the spinel structure an d the size of the particles remain up to 450 degrees C. However the ol eic acid pyrolysis which occurs between 250 and 400 degrees C leads to an amorphous residue of carbon on the magnetite particles. This carbo n can reduce magnetite into ferrous oxid FeO at higher temperature.