Ni@C nanocapsules-decorated SrFe12O19 hexagonal nanoflakes for high-frequency microwave absorption

• SrFe12O19 nanoflakes decorated with Ni@C nanocapsules were prepared.
• The RL exceeding −10 dB is obtained in 14.4–18 GHz for the thickness of 2.0 mm.
• The strong absorption peak reaches −55.72 dB at 8.48 GHz for the thickness of 3.6 mm.

The novel structures of SrFe12O19 nanoflakes decorated with Ni@C nanocapsules were successfully prepared by the conjugating assemble process, in which Ni@C nanocapsules with the diameter of about 5 nm adhered to the surface of SrFe12O19 hexagonal nanoflakes with the length of a side from 0.5 to 1.0 μm and the thickness of about 80 nm. The electromagnetic properties of SrFe12O19/Ni@C-paraffin composite were investigated in the 2–18 GHz frequency range. The effects of Ni@C nanocapsules on the electromagnetic properties of SrFe12O19/Ni@C were studied. The reflection loss exceeding −10 dB is obtained in 14.4–18 GHz for an absorber thickness of 2.0 mm. Moreover, the strong absorption peak reaching −55.72 dB can be observed in 8.48 GHz when the thickness is 3.6 mm. Compared with the SrFe12O19 nanoflakes, the nanocomposites exhibit the thinner thickness, the broader absorption bandwidth and the stronger absorption intensity, which is ascribed to the introduction of Ni@C nanocapsules. Ni@C nanocapsules can induce double dielectric relaxation loss and enhance dielectric loss and generate the cooperative effects of dielectric-magnetic properties. These excellent absorbing performances show that the SrFe12O19/Ni@C nanocomposites have great potential for application in a microwave-absorption field for their strong absorption and broad bandwidth.