Study On The Preparation Of Nano-magnetic Fluids By Non-equilibrium Plasma

Nano-magnetic fluids,often referred as the forefront of researches in materials science, have a widely applications due to their special physical and chemical properties.The synthesis of nano-magnetic particles is one of the key technologies before magnetic fluids could be applied,and is also a difficult problem to be urgently resolved.In this work,nano-magnetic fluids have been prepared with non-equilibrium plasma method.The influencing factors of preparation have been systematically investigated from discharge to the processing parameters.The effect of the capacity of NH₃ and Fe(CO)₅,the pulse frequency and the discharged voltage on saturation magnetization of these magnetic fluids has been revealed.The constraint relations between the space length of electrode and the time of reaction;the amount of surfactant and particle size have also been investiaged. Characterization techniques such as transmission electron microscopy(TEM),small angle X-ray scattering(SAXS),density cup and vibrating sample magnetometer(VSM)have been used to measure morphology,particle size,density and saturation magnetization of these particles and magnetic fluids.At last,the best optimized preparing technical scheme for magnetic fluids by plasma has been studied.The main results obtained in our investigations are as follows:The effect of the pulse frequency and the discharged voltage on saturation magnetization of these magnetic fluids has been investigated by means of VSM.The results show that the magnetic fluids have been prepared quickly and efficiently by plasma having sufficient activation energy,at enviroment temperature of 120～160℃,in about three hours,with the discharged voltage 18kV and the pulse frequency 63kHz.The process parameters have been investigated by experiment.The results show that the best optimized preparing technical scheme for magnetic fluids:the amount of Fe(CO)₅,white oil-based liquid and surfactant were as follows:104g,56g and 8g;the flow capacity were 280 mL/min. The diameters,their distribution,and conglomeration behavior of the nanoparticles in dispersion medium were observed through TEM and SAXS methods.The results indicated that the nanoparticles dispersed in medium,in shape of sphericity and without agglomeration, the bareness diameter were 10～20 nanometer,the sizes of nanoparticles were uniform.