Synthesis And Properties Of Carbon Nanotube Composites Modified By Magnetic Nano Particles

In this paper, wave-absorbing composite materials that carbon nanotubes coated withspinel ferrites and nickel-cobalt particles were prepared，its magnetic andwave-absorbing properties between0and6GHz were investigated.（1） Zn_0.5Co_0.5La_xFe_2-xO₄/CNTs （x=0.00,0.01,0.03,0.05） andNi_0.4Zn_0.35Co_0.25LaxFe_2-xO₄/CNTs composite were prepared by refluxing method,transmission electron microscope （TEM） and X-ray diffraction （XRD） analyses demonstratedthat ferrite nanoparticles were successfully immobilized on the surface of the carbonnanotubes.（2）The effect of the contents of carbon nanotubes on wave-absorbing property wasinvestigated, it has been found that10wt%Zn_0.5Co_0.5Fe₂O₄/CNTs obtained the bestwave-absorbing properties, the maximal absorbing peak-5.66dB and peak width of R<-5dBwas744MHz.（3） Based on the study of10wt%Zn_0.5Co_0.5Fe₂O₄/CNTs, lanthanum was doped intoferrite. When doping amount x value was0.03, the composite possessed the best propertieswith the highest saturation magnetization （Ms） of24.581emu/g and the maximal absorbingpeak-27.6dB at5758.80MHz.（4） Consider of the effect of lanthanum doping amount on the magnetic and microwaveabsorbing properties of Ni_0.4Zn_0.35Co_0.25LaxFe_2-xO₄/CNTs composites.Ni_0.4Zn_0.35Co_0.25La_0.05Fe_1.95O₄/CNTs exhibits the highest saturation magnetization(40.00emu.g^-1) while Ni_0.4Zn_0.35Co_0.25La0.07Fe1.93O4/CNTs with the maximal coercivity of34.38Oe. In the low-frequency band （0～6GHz）, the largest reflection loss of composite was-12.0dB when the doping amount value x is0.07, and the peak width of R<-10dB and R<-5dB was447MHz,1414MHz, respectively.（5） Composites that carbon nanotubes coated by nickel-cobalt were prepared byelectroless plating. The temperature of the reaction solution, pH value and mole ratio of Ni toCo were determined by orthogonal test. The results of magnetic research on productsshowed that sample had the highest coercivity （349.776Oe）when the reaction conditions wereT=60℃、pH=10、Ni：Co=3:7and the highest saturation magnetization (46.396emu·g^-1)whenT=70℃、pH=10、Ni：Co=5:5.（6） The experimental factors that influence the wave-absorbing property should befollowed as temperature﹥pH value﹥Ni/Co ratio. The optimum experiment conditionswere proposed for the best reflex value.