Surface Modification And Microwave Absorbing Properties Of Multi Walled Carbon Nanotubes

Carbon nanotubes have attracted much attention for their many promising properties and potential applications. Carbon nanotubes have special structure and specific electromagnetic properties, such as high aspect ratio, high surface area, small size et al, so they own potential applications in microwave absorbing filed. In this dissertation, dispersiility of multi walled carbon nanotubes (MWNTs) was enhanced by purification treatment, surface modification and electroless nickel plating. At the same time,the application of MWNTs with Ni coating in the field of the compound microwave absorbing material was studied.Firstly, the purification treatment of the MWNTs was studied. MWNTs was purified with the adjoining method of concentrated nitric acid condensate return flow and mixed acid ultrasonic treatment. By the result of scanning electron microscope,it was found that the amorphous carbon , catalyzer and other impurities on the carbon nanotubes surface were removed and the purity of the carbon nanotubes was raised obviously. The purification treatment make carbon nanotubes open, short cutting and enhance its dispersibility.Secondly,the modification and the nickel plating on the surface of MWNTs were analyzed. MWNTs was coated with nickel through the method of electroless plating. The coating was consecutive and homogeneous, which became more smooth and compact after heat treatment. In addition,the mechanism of sensitization, activation and chemistry nickel-plating were investigated in this dissertation.Finally,the carbon nanotubes/epoxy group compound microwave absorbing material was analyzed and its microwave absorbing mechanism was discussed. The reflectivity curve at 2 ~ 18GHz was measured with Vector Network Analyzer. It is found that the maximum absorbing peak of the microwave absorbing composite material containing the carbon nanotubes with Ni coating is 10.46dB at 6.92GHz .The band width (R < -10 dB) of the composites containing carbon nanotubes with Ni coating is 2.46 GHz, band width (R < -6 dB) is 5.41GHz. Comparing with MWNTs, the maximum absorbing peak of the MWNTs with Ni coating reduce, but the band width has the broad trend.