Dielectric and microwave absorption properties of CB doped SiO_2f/PI double-layer composites

Carbon black (CB) with contents of 5.5 wt% and 15 wt% filled quartz glass fiber reinforced polyimide (SiO_2f/PI) composite were designed and prepared. A double-layer absorbing material was designed using the two composites materials as a matching layer and an absorption layer, respectively. The microwave absorption property of single-layer and double-layer composites is calculated according to transmission line theory. The results show that the microwave absorbing property of double-layer composite is better than that of single-layer at the same thickness. When the 5.5 wt%CB doped SiO_2f/PI composite is used as the matching layer with a thickness of 0.7 mm and 15 wt%CB doped SiO_2f/PI composite is used as the absorption layer with a thickness of 0.9 mm, the RL (reflection loss) of the composite reaches a minimum value of −46.18 dB at 16.07 GHz. Meanwhile, the bandwidth of RL ≤ −5 dB is 5.87 GHz and the bandwidth of RL ≤ −10 dB is 3.95 GHz.