Balancing Dielectric Loss and Magnetic Loss in Fe–NiS2/NiS/PVDF Composites toward Strong Microwave Reflection Loss

Lightweight, broad-band, and highly efficient microwave-absorbing materials (MAMs) with tunable electromagnetic properties are in high demand. However, the absorption properties are limited by the simple loss mechanism in commonly used absorbing materials. Here, we tested the microwave-absorbing properties of Fe–NiS2/NiS/poly(vinylidene fluoride) (PVDF) in the frequency range of 2–18 GHz. For the 2.5% Fe–NiS2/NiS/PVDF with the filling content of 20 wt %, the maximum reflection loss can reach −61.72 dB at 14.88 GHz, and the bandwidth can reach 3.8 GHz with the reflection loss value below −10 dB. Loss mechanisms of different composites were analyzed on the basis of their magnetic and dielectric properties using both experimental and computational methods. The results indicate that strong microwave absorption property is achieved through a balancing of dielectric loss and magnetic loss. These findings present a new strategy for the future design of MAMs.