Controllable Construction of Hollow Ni/NiO@PPy Particles for Broadband and Highly Efficient Microwave Absorption

Abstract Microwave‐absorbing materials are widely used in electromagnetic protection and military stealth fields. Hollow structure materials, as efficient microwave absorbing materials, have garnered considerable attention, since they are beneficial to multiple reflection and enhance the attenuation loss of microwaves. Herein, a strategy is proposed to prepare hollow Ni/NiO@PPy particles using a water‐soluble template method combined with in situ polymerization process. The cuboid hollow Ni/NiO@PPy particles are constructed with Na 2 SO 4 as templates and then filled into epoxy resin to form composite films with excellent microwave absorption properties. The Ni/NiO@PPy composite film under optimal conditions exhibits a minimum reflection loss value of −72.14 dB and the absorption rate is more than 99.99% with filling content of 10 wt.%. By adjusting the film thickness, an effective absorption bandwidth of 15.94 GHz can be achieved, which almost completely covers the S, C, X, and Ku bands. The CST simulation results confirm the outstanding radar cross‐section attenuation of the composite film. Remarkably, with an ultra‐low filling content of 2.5 wt.%, the composite film still achieves an absorption rate of 99.90%, demonstrating highly efficient microwave absorption with ultra‐low filling content.