SYNTHESIZE MODIFICATION AND MAGNETIC CHARACTERISTIC IMPROVEMENT OF Fe/Fe OXIDE CORE/SHELL NANOPARTCLE PRODUCE BY BOROHYDRYDE REDUCTION REACTION

Abstract

Nanoparticle of Fe/Fe oxide core/shell structure with high magnetization values has been successfully sinthesized through reduction of FeCl3 by NaBH4 reductor, repeat washing in ethanol, heat treatment at 75 °C and vacuum atmosphere, followed by controlled oxidation with Trimethylamine N-Oxide (TMNO). Morphological structure of the core/shell nanoparticles were evaluated from the image observed with Transmission Electron Microscope (TEM), magnetic properties through the hysteresis curve measured by Vibrating Sample Magnetometer (VSM) while the phase were analysed fromits X-Ray diffraction patterns. Magnetic characteristics of the nanoparticles are found to be affected by the condition of washing process to remove residual phase reactants and heat treatment conditions for the completion of core formation. Too long heating tend to lowered the magnetic properties due to increasing of FeB and Fe2B minor phases. During oxidation process, beside formation of Fe oxide shell on the surface of Fe core, reduction of these minor phases was also proceed and resulted in enhanced ofmagnetic properties. Optimal characteristics of nanoparticle with a crystalline size of ~ 8 nm within Fe core of < 30 nm particle size and Fe oxide shell of ~ 3 nm thickness with saturation magnetization Ms ~ 130 emu/g obtained in the synthesis with 15x washing steps followed by heat treatment at 4 hours.