Preparation and Microwave Absorption Properties of SiC@C/Co₂Si@C/Polyvinylidene Fluoride Composites

With glucose as the carbon source, SiC@C core-shell whiskers were prepared through hydrothermal method and high-temperature sintering successively. These whiskers were then mixed with cobalt-based zeolitic imidazolate framework materials （Co-ZIF） in solution and sintered at high temperatures to prepare microwave absorbing fillers. These fillers and polyvinylidene fluoride （PVDF） and were mixed and hot-pressed to fabricate composites with different filler mass fractions （5%, 10%, 15%, 20%, 25%, 30%）. The microwave absorption properties of the composites were investigated. The results show that the carbon sheel on the surface of SiC whisker of the absorbing filler had poor continuity, and the nano-sized Co₂Si particles were attached to the surface of the carbon shell. With the increase of filler content, the dielectric constant of the composites increased, the real and imaginary parts of the magnetic permeability remained at relatively low levels; the dielectric loss tangent increased and was greater than the magnetic loss tangent, indicating that dielectric loss played a dominant role in the microwave absorption. When the filler mass fraction was 10%, the minimum reflection loss of the 2.41 mm thick composite reached −53.19 dB, and the effective absorption bandwidth was 7.64 GHz （10.28−17.92 GHz）, showing excellent microwave absorption performance and impedance matching. The effective absorption bandwidth of the 2.36 mm thick composite fully covered the Ku band （12−18 GHz） and partially covered the X band （8−12 GHz）, indicating good broadband microwave absorption adaptability across multiple frequency bands.