A novel 3D silver nanowires@polypyrrole sponge loaded with water giving excellent microwave absorption properties

Three-dimensional (3D) porous structure has attracted considerable interest owing to its flexibility, low density and potential applications. Here, Ag@PPy sponge was synthesized via solvothermal, in situ polymerization and freeze-drying techniques. The Ag@PPy sponge exhibits well elasticity and water absorption capacities due to the 3D network structure. The microwave absorption properties of the Ag@PPy sponge were measured by coaxial line and wave guide methods. The results show that the effective bandwidth (reflection loss values of less than −10 dB) of the Ag@PPy sponge without resin or paraffin matrix could cover the whole X-band (8.2–12.4 GHz) at the thickness of 5 mm. Besides, the complex permittivity of the Ag@PPy sponge can be modulated by adjusting the water ratios from 0 to 78.4 wt%. When the water ratio is 26.2 wt%, the Ag@PPy-26.2 sponge exhibits optimal microwave absorption properties, which the minimum reflection loss ( RL ) value reaches −33 dB at 8.8 GHz with the thickness of 3 mm. Our research provides a new strategy to design microwave absorbers by using water.