Cold Plasma Treatment Of Magnetic Nanoparticles

Abstract

This thesis investigates the application of cold plasma to remove the oleic acid bonded on magnetic nanoparticles: SmCo5 nanoflakes prepared via surfactant assisted high energy ball milling and CoFe2O4 nanoparticles prepared via chemical synthesis. Oleic acid molecules bonded on nanoparticles are in the carboxylate form which could not be washed away by organic solvents in ultrasonic bath; only free oleic acid molecules left on the nanoparticle surface after ball milling can be washed away through ultrasonic bath. High temperature annealing method works for removing oleic acid but nanoparticles would be damaged because of oxidation and decomposition.The RF cold plasma has advantages over above methods as the plasma temperature is typically around room temperature, and the energetic ions could strike away carboxylate molecules bonded on the surface of nanoparticles without changing the surface chemistry. Powder X-ray diffraction (XRD) was performed to see if there was phase transformation, decomposition during plasma treatment. The content change of oleic acid moleculs on the nanoparticles surface was confirmed by X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR).