Fabrication of Fe/Fe3C-functionalized carbon nanotubes and their electromagnetic and microwave absorbing properties

Fe/Fe3C-functionalized carbon nanotubes (CNTs) have been prepared by the floating catalyst chemical vapor-deposition method. It is demonstrated that the Fe and Fe3C nanostructures are both encapsulated in the CNTs or decorated on the surface of CNTs. The Fe/Fe3C content in the composites can easily be adjusted by changing the ferrocene concentration in the preparation. The electromagnetic properties of the CNTs have been evaluated in the frequency range of 2-18 GHz, and the nanocomposites exhibit excellent microwave absorbing performance. The CNT composites with higher Fe/Fe3C content show enhanced microwave reflection losses. The significant influence of the Fe/Fe3C nanostructures on the microwave absorption is realized by tuning the characteristic impedance of the nanocomposites. With increasing thickness, the maximum reflection loss peak shifts to lower frequency. The microwave absorbing performance of the composites is mainly caused by dielectric loss, resulting from the continuous CNT networks with excellent electrical conductivity.