Multiwalled carbon nanotubes (MWCNTs)/Fe, MWCNTs/Co, and MWCNTs/Ni nanopowders have been prepared conveniently by a simple chemical method. The excellent microwave absorption properties in S-band have been obtained due to proper combination of the complex permeability and permittivity resulting from the magnetic nanoparticles and lightweight MWCNTs. The frequency of microwave absorption obeys the quarter-wavelength matching model. For the most excellent microwave absorption properties in S-band, it is found that the reflection loss exceeds −20 dB from 2.04 to 3.47 GHz for the absorber thickness between 3.36 and 5.57 mm, and a minimum reflection loss value of −39 dB was observed at 2.68 GHz on a specimen with a matching thickness of 4.27 mm for MWCNTs/Fe. The MWCNTs/Fe/Co/Ni nanopowders all can be a promising candidate for lightweight microwave absorption materials in S-band.

Investigation on Microwave Absorption Properties for Multiwalled Carbon Nanotubes/Fe/Co/Ni Nanopowders as Lightweight Absorbers