Preparation And Performance Of Magnetic Carbon Nanotubes With High Saturation Magnetization

With excellent physical and chemical properties of carbon nanotubes(carbon nanotubes,CNTs)since its discovery in 1991,it has been excavated a number of advantages,for example,good heat resistance,large specific surface area,high mechanical strength.Through the organic integration of carbon nanotubes with magnetic particles(on the surface of carbon nanotubes coated or filled in the tube,magnetic nanoparticles)can also integrated their physical and chemical properties,the composite product has a wide application prospect in biomedicine,catalyst,magnetic storage,absorbing agent.Therefore,compared with other materials,the use of carbon nanotubes composite materials will have unexpected excellent performance.This paper aims at using the filling method for the preparation of Fe-N/CNTs nano composite material under certain temperature.The effects of different ammonia flow rate on the microstructure,composition and properties of the samples were studied,and the formation mechanism was analyzed.In this paper,based on the research work of others,with an average diameter of 20?50 nanometer carbon nanotubes(>90%purity)as raw materials,using different concentrations of Fe(NO3)3 solution and carbon nanotubes were prepared by capillary action CNTs-Fe(NO3)3 composite powder.After the powder was dried,the gas nitriding process was carried out under different ammonia flow rate(0.1-2m3/h)at 650? for 2h,and the experiment was carried out under the ammonia atmosphere.The micro structure and magnetic properties of the samples prepared by different processes were tested and analyzed.The results show that the filling method used in this paper,by capillary action of carbon nanotubes with different ammonia flow was successfully prepared with magnetic filled carbon nanotube composite material,magnetic particles including ?'-Fe4N??-Fe3N??-Fe2N and ?-Fe2O3.In the preparation of Fe-N/CNTs composite material,because of the different ammonia flow rate obtained Fe-N alloy with different nitrogen content.And during the nitriding of 650?,due to the presence of nano-y-Fe2O3 particles and the controllable nitrogen potential and iron nitrate concentration,the reaction deviated from the eutectoid transformation theory.In this paper Fe-N/CNTs composite material preparation process,?'-Fe4N/CNTs which obtained at 650? for 2h with the ammonia flow rate of 0.5m3/h,has the best comprehensive performance,such as high saturation magnetization(91.79emu/g)and coercivity(219.350e),magnetic properties of uniform distribution and huge potential in low frequency absorbing wave properties(RL=-10.91dB).In the contrast experiment,through a series of reactions,the Fe(NO3)3 of Fe(NO3)3/CNTs was decomposed into ?-Fe2O3 in the atmosphere without ammonia gas.?-Fe2O3/CNTs not only has good magnetic properties(Ms=61.86emu/g,Hc=232.5Oe)but excellent absorbing performance(d=1.8mm,RL=-34.23dB,the effective bandwidth is 1.2GHz)because of the impedance matching which better than Fe-N/CNTs composites.The impedance matching of?'-Fe4N/CNTs composite material is still lacking,so it is necessary to further study and broaden the absorbing agent.