Microwave Electromagnetic and Absorption Properties of N-Doped Ordered Mesoporous Carbon Decorated with Ferrite Nanoparticles

Lightweight nitrogen-doped ordered mesoporous carbon (NOMC) with high specific surface area and pore volume have been prepared through self-assembly and subsequent heat treatment route. The spherical NOMC particles are decorated with CoFe2O4 nanoparticles via coprecipitation method to enhance their microwave absorption property. The electromagnetic parameters of the NOMC and CoFe2,04/NOMC composites are measured and the microwave reflection loss properties are evaluated in the frequency range of 0.5-18 GHz. The results show that both the real part and imaginary part of permittivity of NOMC totally decline and the real part of permeability increases with the introduction of ferrite. However, the negative values of the imaginary part of the complex permeability appear for the CoFe2O4/NOMC composites, which may be caused by enhanced eddy current effect due to the introduction of ferrite. The reflection loss results exhibit that the CoFe2O4/NOMC composites have excellent microwave absorption performances. The absorption bandwidth less than 10 dB reaches 5.0 GHz (11.9-16.9 GHz) for 40-F/NOMC composite (40 wt % ferrite) with 1.5 mm of thickness and the minimum reflection loss value is up to -38.3 dB at 3.9 GHz for 30-F/NOMC composite with 4.0 mm of thickness. The excellent absorption properties derive from the synergistic effect between dielectric loss of NOMC and magnetic loss of ferrite and better impendence matching at air and ferrite/NOMC composite interface. Thus, the lightweight ferrite/NOMC composites exhibit their great potential as microwave absorbing materials.