Synthesis of Controllable Nickel Chalcogenide Nano-Hollow Spheres and Their Tunable Absorbing Properties

A series of nickel chalcogenide compounds (NiS₂, NiS, NiO and NiSe₂) with nanoscale hollow sphere structure have been successfully designed and fabricated by a simple and effective hydrothermal process. By appropriately adjusting the reaction temperature, we have obtained chalcogenide nickel nanomaterials with uniform size and controllable morphology. Subsequently, the electromagnetic wave absorption properties of nickel chalcogenide nano-hollow sphere compounded with paraffin and polyvinylidene fluoride (PVDF) were investigated in a frequency range of 2–18 GHz. Under the same filling amount, the optimal absorbing performance of PVDF-based composites can all exceed −10dB, which is significantly better than paraffin-based composites. Therefore, PVDF-based composites are more conducive to microwave absorption performance than paraffin-based composites. Interestingly, the optimal effective frequency bandwidth of NiS/PVDF nanocomposites with 20 wt% filler content covers 5.0 GHz at a thin coating layer of 2.0 mm, and the corresponding reflection loss value can reach −36.3 dB at 15.2 GHz. Moreover, the fundamental attenuation mechanisms are discussed in detail.