Flower-like NiO to flower-like NiO/Ni@C microspheres: An effective strategy to comprehensively improve the loss capabilities.

It was well recognized that the penetrated electromagnetic (EM) wave could be dissipated by means of magnetic loss, polarization loss and conduction loss. In order to improve their loss capacities and take full advantage of flower-like geometrical morphology, in this study, we proposed a simple route for the production of flower-like core@shell structure NiO/Ni@C microspheres through the carbon thermal reaction using NiO microflowers as precursor. The obtained results revealed that our proposed strategy successfully synthesized the core@shell structure magnetic carbon-based multicomponent nanocomposites without destroying the geometrical morphology of precursor. By regulating the annealing temperature, the as-prepared NiO/Ni@C microspheres with different contents of Ni and degrees of graphitization could be selectively synthesized, which effectively boosted their magnetic loss, polarization loss and conduction loss capabilities. Therefore, the elaborately designed NiO/Ni@C microspheres displayed the superior microwave absorption performances including strong absorption capability, broad absorption bandwidth and thin matching thicknesses compared to the NiO precursor. In summary, our findings not only provided a simple route to design and synthesize flower-like core@shell structure magnetic carbon-based nanocomposites as novel microwave absorbers, but also presented an effective strategy to comprehensively improve their loss capacities.