Absorbing properties of α-manganese dioxide/carbon black double-layer composites

In order to improve the absorbing properties of the electromagnetic wave absorbing plate, double-layer wave absorbing materials, which are composed of a matching layer and an absorbing layer, were devised. The matching layer is a surface layer of the wave absorbing sample, from which most of the incident waves easily enter the sample, and the absorbing layer is a second layer under the matching layer, which plays an important role in incident wave attenuation. The total thickness of the double-layer composites is the sum of the thicknesses of the matching layer and the absorbing layer. In this paper, alpha-manganese dioxide and carbon black (CB) were used as absorbents in the matching layer and the absorbing layer respectively. Meanwhile, the structure of the a-manganese dioxide and the CB particles were analysed by x-ray diffraction and transmission electron microscopy, and the dielectric property and absorbing mechanics were also studied. The results showed that, in the case of the mass fraction of CB in the absorbing layer being 30% and the thickness of the absorbing layer being 3 mm, the effectual absorption band (below -10 dB) of the double-layer wave absorbing materials reaches 8.6 GHz and 7.6 GHz in the testing frequency range between 8 GHz and 18 GHz, respectively, when the mass fraction of alpha-MnO2 in the matching layer was 10% and the thicknesses of the matching layer were 2mm and 1 mm, respectively, and the effectual absorption band (below -10 dB) reaches 8.7 GHz in 8 -18 GHz when the mass fraction of alpha-MnO2 in the matching layer was 20% and the thickness of the matching layer was 2 mm.