Skin collagen fiber-based radar absorbing materials

By using skin collagen fiber (CF) as raw material, Schiff base structure containing CF (Sa-CF) was synthesized through CF-salicylaldehyde reaction. Then a novel radar absorbing material (Fe-Sa-CF) was prepared by chelating reaction between Sa-CF and Fe³⁺. The coaxial transmission and reflection method was used to analyze the complex permittivity and complex magnetic permeability of these CF-based materials, and the radar cross section (RCS) method was used to investigate their radar absorbing properties in the frequency range of 1.0-18.0 GHz. Experimental results indicated that the conductivity of CF increased from initial 1.08×10^-11 to 2.86×10^-6S/cm after being transferred into Fe-Sa-CF, and its dielectric loss tangent (tanδ) in the frequency range of 1.0–17.0 GHz also increased. These facts suggest that the Fe-Sa-CF is electric-loss type radar absorbing material. In the frequency range of 3.0–18.0 GHz, Sa-CF (1.0 mm in thickness) exhibited somewhat radar absorbing property with maximum radar reflection loss (RL) of -4.73 dB. As for Fe-Sa-CF, the absorbing bandwidth was broadened, and the absorbing intensity significantly increased in the frequency range of 1.0–18.0 GHz where a maximum radar RL of -9.23 dB was observed. In addition, the radar absorbing intensity of Fe-Sa-CF can be further improved by increasing membrane thickness. When the thickness reached to 2.0 mm, the RL values of Fe-Sa-CF were -15.0 - -18.0 dB in the frequency range of 7.0-18.0 GHz. Consequently, a kind of novel radar absorbing material can be prepared by chemical modification of collagen fiber, which is characterized by thin thickness, low density, broad absorption bandwidth and high absorption intensity.