Hollow polypyrrole/Ni/PVDF microspheres for broadband microwave absorption via a spray phase inversion method

There is growing interest in porous multi-component composites as efficient electromagnetic wave absorption (EMWA) materials at microwave frequencies. Herein, a novel spray phase inversion method was used to fabricate porous composites containing 1D polypyrrole (PPy) nanofibers and 1D nickel nanochains (Ni-NC) in hollow polyvinylidene fluoride (PVDF) microspheres. Interconnected conductive and magnetic networks endowed the hollow PPy/Ni-NC/PVDF microspheres with remarkable EMWA properties in the 18–40 GHz region. By optimizing the PPy and Ni-NC contents, the minimum reflection loss (RL min ) in the composite microspheres reached −47.2 dB (at 25.36 GHz) and −39.8 dB (at 31.30 GHz). The effective absorption bandwidth (EAB) could be tuned to cover 18–40 GHz range by varying the absorber thickness from 1.0 to 3.5 mm. The results show that magnetic materials (Ni-NC) with large aspect ratio and hollow microsphere-shaped absorbers are beneficial for improving EMWA performance. Results guide the future development of low-cost/high performance EMWA materials.