Surfactant-assisted solvothermal synthesis of pure nickel submicron spheres with microwave-absorbing properties

Pure metallic nickel submicron spheres (Ni-SSs), flower-like nickel nanoflakes, and hollow micrometer-sized nickel spheres/tubes were controllably synthesized by a facile and efficient one-step solvothermal method with no reducing agent. The characteristics of these nickel nanostructures include morphology, structure, and purification. Possible synthesis mechanisms were discussed in detail. The resultant Ni-SSs had a wide diameter distribution of 200~800 nm through the aggregation of small nickel nanocrystals. The ferromagnetic behaviors of Ni-SSs investigated at room temperature showed high coercivity values. Furthermore, the microwave absorption properties of magnetic Ni-SSs were studied in the frequency range of 0.5-18.0 GHz. The minimum reflection loss reached -17.9 dB at 17.8 GHz with a thin absorption thickness of 1.2 mm, suggesting that the submicron spherical structures could exhibit excellent microwave absorption properties. More importantly, this one-pot synthesize route provides a universal and convenient way for preparation of larger scale pure Ni-SSs, showing excellent microwave absorption properties.