Electromagnetic and absorbing properties of multi-walled carbon nanotubes/epoxy-silicone coatings

Multi-walled carbon nanotubes as dielectric absorber and epoxy-silicone resin as matrix were used to fabricate multi-walled carbon nanotubes/epoxy-silicone resin coatings. The effects of multi-walled carbon nanotubes content and diameter on dielectric and microwave absorbing properties of the coatings were investigated in the frequency range from 2GHz to 18GHz. The results indicate that both of the real and imaginary part of the permittivity are enhanced with increasing multi-walled carbon nanotubes content and diameter. When the multi-walled carbon nanotubes content is 2wt%, the complex permittivity of the coatings keep almost constant in the frequency range from 2GHz to 18GHz, and are independent on the multi-walled carbon nanotubes diameter. As the multi-walled carbon nanotubes content increases to 5wt%, the complex permittivity of the coatings decreases with the increase of frequency, and also exhibits visible frequency-dependence dielectric response. The minimum reflection loss of the coatings shifts to the low frequency region (from 12. 8GHz to 10.8GHz) as the multi-walled carbon nanotubes diameter increasing. The results of the microwave absorbing properties show that the good microwave absorption ability (below -10dB) can be obtained in a frequency range from 7GHz to 14GHz when the multi-walled carbon nanotubes content is 10wt% and the coating thickness is 2mm.