Wave-absorbing properties of carbonyl iron powder/carbon fiber reinforced cement-based composites

A lab-scale reflectivity test system was used to investigate wave absorbing properties of cement-based composites with carbon fiber and carbonyl iron powder/carbon fiber in a frequency range of 2-18 GHz. The microstructures and compositions of the composites were analyzed by scanning electron microscopy and X-ray diffractometer. The results show that the reflectivity of the composites with carbon fibers increases with increasing carbon fiber content in the frequency range of 2-8 GHz. In the high frequency range of 8-18 GHz, the wave absorbing property oscillation was larger when carbon fiber contents increased. Compared to the reflectivity of the composites with fiber content of 0.6%, the wave absorbing properties could not improved in the frequency range of 2-4 GHz when carbon fiber and carbonyl iron powder both were added. In the frequency range of 4-12 GHz, the reflectivity was decreased. In the frequency range of 12-18 GHz, a minimum reflectivity of -11.9 dB with a wave absorbing frequency band width of 7.3 GHz appeared and the wave was totally absorbed. The wave absorbing frequency band width of the composites with carbonyl iron powder at high frequencies was widened, and the variation of wave absorbing properties became smaller when carbonyl iron powder content increased.