Environmentally Friendly Synthesis of Velutipes-Shaped Ni@CNTs Composites as Efficient Thin Microwave Absorbers

Abstract

An environmentally friendly solvent-free strategy for synthesis of velutipes-shaped Ni@CNTs-x composites as high-performance electromagnetic wave (EMW) absorbers by combining Ni particles with carbon nanotubes (Ni@CNTs) through in situ pyrolysis of a mixture of nickel nitrate and melamine is proposed. The CNTs contained several microporous structures, thereby facilitating a reduction in density and an enhancement of the EMW absorption. The EMW absorption performance first increased then decreased with increasing Ni content. The effective absorption bandwidth (RL < −10 dB) of the synthesized Ni@CNTs-x was up to 5.45 GHz for a thickness of 1.79 mm, while the minimum reflection loss (RLmin) was −60.56 dB at 17.32 GHz for a thickness of 1.582 mm and 20 wt.% loading. Overall, the results of this study indicate that this facile environmentally friendly method is effective to prepare excellent, thin, lightweight EMW absorbers with wide absorption bandwidth and high absorption efficiency.