Electromagnetic and microwave absorbing properties of Co-filled carbon nanotubes

Microwave absorbing property, complex permittivity and permeability of the Co-filled carbon nanotubes (CNTs) have been investigated. CNTs were filled with Co nanoparticles via a wet-chemical method. Compared with the CNTs, the real part (ɛ′) and imaginary part (ɛ″) of the complex permittivity as well as the dielectric dissipation factor (tan δɛ = ɛ″/ɛ′) of the Co-filled CNTs were much smaller, while the real part (μ′) and imaginary part (μ″) of the complex permeability and the magnetic dissipation factor (tan δμ = μ″/μ′) were greater. The Co-filled CNT/epoxy composites achieved a reflection loss below −10 dB (90% absorption) at 10.8–14.2 GHz, and the minimum value was −21.84 dB at 12.2 GHz. The microwave enhancement absorption of the Co-filled CNT/epoxy composites was attributed to both dielectric and magnetic losses. The microwave absorbing peak of the CNT/epoxy composites moved to the higher frequency by filling the Co nanoparticles into the CNTs. Compared with the CNTs, there are more interfaces between the Co nanoparticles and CNT inner surfaces in the Co-filled CNTs. Therefore, interfacial multipoles contributed to the absorption of the Co-filled CNT/epoxy composites.