Preparation And Properties Of Carbon Nanotube Composite Absorbing Materials

In this paper, complex permittivity and permeability of carbonnanotubes（CNTs）, rare earth/carbon nanotubes, rare earth/carbon nanotubes/bariumferrite and carbon nanotubes/carbonyl iron（CI） composite absorbers weredetermined. Composite absorbers reflection was caculated by taransmission line.Microwave absorbing patch composites with silicone rubber as matrix and bothcarbon nanotubes and carbonyl iron particles as absorbers were prepared, andreflection loss of composites was tested. Microstructures were observed by SEM,simultaneously, microwave composites absorbing mechanism were alsoinvestigated.The results indicated that the amorphous carbon and catalyst of the surface ofCNTs were oxidized to remove after treating with regurgitating nitric acid, whichimproved the purity. With the addition of dispersant agent SDS, the surface groupsof CNTs acted with the hudrophobic chains, CNTs uniformly dispersed byelectrostatic repulsion force to make the reunion phenomenon is reduced to improvethe dispersion in water.Complex permittivity increased with the content of CNTs increasing as CNTsfor microwave absorbers, however, complex permeability changed little. Reflectionloss values exceeding-5dB can be obtained bandwith up to9.2GHz, and the bandwithover to2.48GHz with the reflection below-10dB for the composite filled with10vol%CNTs.Complex permittivity and permeability were effectively regulates andabsorbing performance were improved after rare earth mixed CNTs as compositeabsorbers. Different types and contents of rare earth oxides makes the differentregulatories of electromagnetic parameters. CeO₂and Eu₂O₃can improve thecomposite absorbers complex permittivity, but Sm₂O₃can reduce, it can be selectedas needed.Electromagnetic parameters can improve with increasing content of CNTs inthe CNTs/CI composite absorbers. Reflection loss values exceeding-5dB can beobtained in the frequency range of2¹8GHz（the whole range） and over-10dB canbe obtained bandwith range of2.32³.6GHz when the composite filled with0.5vol%CNTs and50vol%CI particles.Microwave absorbing patch composites with silicon rubber as a matrix andboth CNTs and CI particles were prepared. Dispersion of composites with CNTs andCI particles in the rubber was observed by scanning electron microscopy. The testresult with the calculation comparision showed that non-uniform dispersion makes different reflection results.