Facile synthesis of 3D flower-like Ni microspheres with enhanced microwave absorption properties

Rational design of the microstructure of functional materials provides a new opportunity to improve their performance. However, it is always difficult to construct desirable microstructures in magnetic metals due to their strong magnetic interactions. Herein, we demonstrate the successful synthesis of three-dimensional flower-like Ni microspheres (FNMs) through a simple two-step process, in which flower-like Ni(OH)₂ microspheres are firstly prepared by a hydrothermal route and then are reduced under a high-temperature H₂/N₂ atmosphere. The as-prepared FNMs are composed of cross-linked nanoparticles directed by their precursor. Compared with commercial and home-made Ni powder, FNMs exhibit enhanced conductivity and dielectric loss ability, as well as significantly improved impedance matching. As a result, FNMs exhibit good microwave absorption properties, including a strong reflection loss (−56.8 dB at 15.8 GHz) and a broad qualified frequency range (2.5-18.0 GHz) with thicknesses ranging from 5.0 to 1.0 mm and a thin matching thickness of 1.12 mm. Such an excellent performance is substantially superior to those of Ni-based materials derived from various elaborate strategies. It is believed that our work may inspire the controlled synthesis of conventional magnetic metal materials with enhanced microwave absorption properties in the future.