Preparation and electromagnetic properties of multiwalled carbon nanotubes/Ni composites by γ-irradiation technique

Multiwalled carbon nanotubes (MWCNTs) were coated with Ni nanoparticles prepared from reduction of Ni²⁺ by a γ-irradiation technique, producing MWCNTs/Ni composite. It was determined that surface modification of MWCNTs and generation of hydrophilic environment by γ-irradiation was crucial to the dispersion of metal nanoparticles on MWCNTs. The prepared MWCNTs/Ni composite was demonstrated to be a ferromagnetic material, and the relative complex permeability and permittivity were studied. It was calculated that after coating with Ni nanoparticles, the reflection loss properties of MWCNTs were greatly improved in the frequency range between 3.8 GHz and 18 GHz, with a maximum absorption of -7.2 dB at 6.4 GHz. Furthermore, the microwave absorbing properties could be modulated simply by manipulating the thickness of the prepared MWCNTs/Ni composite for application in different frequency bands.