Preparation Of Graphite, Nickel Nanoparticles By Electrolysis And Their Magnetic Properties

It is quite difficult to preparing monodisperse nanoparticles,because of their huge ratio surface area and high surface energy.The nanoparticles can easily be reunited during the preparation process.How to prepare monodisperse nanoparticles with narrow particles size distribution is always a focus.In this present work,monodisperse graphite and nickel nanoparticles were prepared by electrolysis method.The microstructure and morphology of the graphite and nickel nanoparticles were characterized,and their magnetic properties were also tested.Carbon hydrosol was prepared by electrolysis between two graphite electrodes in an aqueous solution,which most of the particle size ranged from 10-30 nm.Effects of current intensity,current style and ultrasonic on the concentration and particle size of carbon hydrosol were investigated,respectively.Both the concentration and the particle size of graphite hydrosol increased as the current intensity increased.Carbon hydrosol with suitable concentration and particle size was obtained when the current intensity ranged from 4-6 mA/cm~2.In comparison The DC-biased pulsed electrolysis can accelerate preparation,compared to the direct current electrolysis and pulsed electrolysis.But the particle sizes of carbon hydrosol prepared by there three current styles were nearly the same.Furthermore,the ultrasonic can also accelerate preparation process.Carbon nanoparticles were obtained by centrifugal separating and vacuum drying of the carbon hydrosol.The results of XRD and Raman spectroscopy showed that the nanoscale carbon powder exhibited good nanocrystalline structure.It was further proved by HRTEM.TEM and laser particle size analysis showed that the graphite nanoparticles were monodisperse and most of the particle size ranged from 10-30 nm.Magnetic properties were investigated in the temperature range from 2 to 300 K.The graphite nanoparticles were diamagnetic at high temperature,and paramagnetic at low temperature.Nickel nanoparticles(＜30 nm)were produced by ultrasonic pulsed electrolysis between two nickel electrodes in an aqueous solution with addition of polyglycol, polyvinylpyrrolidone and so on,as surfactants.Magnetic properties were investigated at the room temperature.The nickel nanoparticles showed weak ferromagnetic.The saturation magnetization of the nickel nanopartMes was lower than that of bulk nickel. Both the small size effect and the very slight amount of the adsorbed surfactant molecules on the nickel nanoparticles might cause a decrease in saturation magnetization.