Preparation mechanism and properties of a ceramic–based interference microwave absorbing composite prepared by a high–temperature foaming method

Abstract

A ceramic–based interference microwave absorbing composite was prepared by sintering green bodies embedded with carbon fibre films (CFF). The entrapment of CO2 released by CaCO3 in the molten green bodies during sintering prevented CFF oxidation, which was the key for the preparation of the composite. CFF addition scattered the microwave that entered the composite, causing microwave to deviate from its original propagation direction and then resulting in reduction of the microwave received by the horn antenna. The composite with a double–layer CFF possessed good microwave absorbing performance with entire reflectivity curve below −10 dB and mean reflectivity as low as −10.9 dB in the 8.0–18.0 GHz frequency range, had a porous internal structure but dense surface, a high total/closed porosity of 82–84%/81–83%, a moderate compressive strength of 3.3–3.5 MPa and a relatively high surface hardness of 1.1 GPa, which was an excellent microwave absorber with promising features in terms of being lightweight, thermally insulated, waterproof and resistant to thermal aging.