Investigation Of Rectification And Microwave Absorbing Ability Of Carbon Nanotubes

The Carbon nanotube, discovered in 1991 is another allotrope of carbon and typically one-dimension nanomaterial. Carbon nanotubes have special structure and specific electromagnetic properties and own potential applications in microwave absorbing filed. In this dissertation, decentrality of multi-walled carbon nanotubes (MWNTs) was enhanced by purification treatment, electroless nickel plating andγ-Fe₂O₃ loading. At the same time,the application of MWNTs with Ni andγ-Fe₂O₃ coating in the field of the compound microwave absorbing material was studied.Firstly, the purification treatment of the MWNTs was studied. MWNTs were purified by the method of concentrated nitric acid and mixed acid (H2SO4/HNO3 = 5/2) condensate return flow. It was found that the amorphous carbon,catalyzer and other impurities on the surface of MWNTs were removed and the purity was raised obviously. Active radicals were built on the surface and the dispersibility was enhanced.Secondly,the nickel plating andγ-Fe₂O₃ loading on the surface of MWNTs were analyzed. MWNTs were coated with nickel through two different methods with or without Pt activation. The coating was consecutive and homogeneous, especially the method without Pt greatly remove the cost and afford facilities for industrialization. MWNTs coated withγ-Fe₂O₃ were gained by series deoxidization and oxidation agglomeration.Finally, the carbon nanotubes/epoxy group compound microwave absorbing material were analyzed and the microwave absorbing mechanism was discussed. 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 is 2.46GHz(R<-10dB) and 5.41GHz(R<-6dB). The maximum absorbing peak of the carbon nanotubes withγ-Fe₂O₃ coating is 10.40dB at 4.45GHz .The band width is 1.70 GHz(R<-10dB) and5.12GHz (R<-6dB) .Comparing with MWNTs, the maximum absorbing peaks of the MWNTs with Ni andγ-Fe₂O₃ coating reduce, but the band width have the broad trend.