Comparison in dielectric and microwave absorption properties of SiC coated carbon fibers with PyC and BN interphases

SiC coated carbon fibers with two different types of interphases, pyrolytic carbon and boron nitride (C-f-PyCi-SiC and C-f-BNi-SiC), were respectively prepared and their dielectric and microwave absorption properties were investigated. Results showed that both real (epsilon') and imaginary part (epsilon) of permittivity of these two SiC coated carbon fibers decrease significantly, in comparison to carbon fibers. The decreased permittivity is mainly due to the large decrease in electrical conductivity. Furthermore, electromagnetic impedance match is improved with the decreasing permittivity, leading to much better microwave absorption properties. Compared to PyC, BN with higher electrical resistivity and lower permittivity endues better impedance match and stronger microwave attenuation for C-f-BNi-SiC. Both C-f-PyCi-SiC and C-f-BNi-SiC with superior microwave attenuation performance exhibit promising prospects as microwave absorbing materials.