Research On Preparation And Application Of Magnetic Properties Encapsulated In Carbon Nanotubes

Since the discovery of carbon nanotubes,the investigation on Carbon nanotubes (CNTs)has become a hot topic in the world due to their potential applications as high-performance nanoscale materials and electronic devices.More specifically metal-filled carbon nanotubes may also have a variety of industrial applications. Many methods of synthesis have been attempted and various materials encapsulated have been tested,in particular those involving magnetic or ferromagnetic materials. Magnetic nanocomposites have potential applications in various areas such as magnetic recording,magnetic data storage devices,toners and inks for xerography, and magnetic resonance imaging.Therefore,studies on magnetic nanocomposites, especially on magnetic CNT,are rapidly expanding.On the side,the technique of the realignment of purified CNT is meaning for the field emission characteristics and the. preparation of cold cathode.In this thesis,two kinds of decorated carbon nanotubes were chosen as the experimental material:At first,CNTs encapsulated magnetic Ni,Co,Fe,and Ni,Co,Fe alloy nanoparticles were prepared successfully by the in situ method of anodic arc discharging plasma evaporating the Ni,Co and Fe powder filled graphite bar in He atmosphere,and the magnetic nanoparticles filled multiwalled carbon nanotubes (MWCNTs)were also prepared in the same process;Secondly,the pristine products were characterized by the transmission electron microscopy(TEM),electron energy disperse spectroscopy(EDS),and X-ray diffraction(XRD).The magnetic properties of the products were characterized by vibration sample magnetometer(VSM).The experiment results show that the carbon encapsulated magnetic nanoparticles have uniform size with an average diameter of 25 nm,the thickness of the coated carbon layer is range from 10 nm to 20 nm.The core magnetic nanoparticles are Ni,Co,Fe. The saturated magnetizationσ_s,remanenceσ_m and coercivity H_c of the sample are 17.30 emu/g,3.96 emu/g and 396 O_e respectively.Thirdly,the optimal conditions for the production of high quality carbon encapsulated magnetic nanoparticles in our case are:a helium gas atmosphere of6.0×10~4 Pa,an arc current of 70 A,a voltage drop of 24 V,the catalyst content of W(Co):W(Ni):W(Fe)= 1:1:1,and well cooled electrodes and collector;Fourthly,the technology of the realignment of purified CNTS in the shear flow and in the mechanical stretching process is presented in this paper.This experimental result is consistent with our theory analysis.