Microwave Absorption and Shielding Property of Composites with FeSiAl and Carbonous Materials as Filler

Silicone rubber composites filled with FeSiAl alloys and multi-walled carbon nanotubes (MWCNT)/graphite have been prepared for the first time by a coating process. The complex permittivity and permeability of the composites were measured with a vector network analyzer in a 1-4 GHz frequency range, and the DC electric conductivity was measured by a standard four-point contact method. These parameters were then used to calculate the reflection loss (RL) and shielding effectiveness (SE) of the composites. The results showed that the added MWCNT increased the permittivity and permeability of composites in the L-band, while the added graphite increased only the permittivity. The variation lies in the interactions between two carbonous absorbents. Addition of 1 wt% MWCNT enhanced the RL in the L-band (minimum -5.7 dB at 1 mm, -7.3 dB at 1.5 mm), while the addition of graphite did not. Addition of MWCNT as well as graphite reinforced the shielding property of the composites (maximum SE 13.3 dB at 1 mm, 18.3 dB at 1.5 mm) owing to the increase of conductivity. The addition of these carbonous materials could hold the promise of enforcing the absorption and shielding property of the absorbers.