The 3D CoNi alloy particles embedded in N-doped porous carbon foams for high-performance microwave absorbers

The 3D CoNi alloy particles embedded N-doped porous carbon (CoNi@PRM-NC) foam with open reticular structures and high-performance microwave absorption are prepared by the novel sponge-templated strategy that uses melamine foam as a sacrificial scaffold and supporting template, phenolic resol as a carbon precursor and cobalt nickel nitrate as a magnetic particle precursor. It is worth noting that the surface of the skeleton has a large amount of honeycomb-like pores without add any pore formers and surfactants. After adding cobalt nickel metal particles, all three materials exhibit the enhanced electromagnetic wave absorption. By contrast, 3D CoNi@PRM-NC performs best, with the minimum reflection loss values of -56 dB at 17.8 GHz when the thickness is 1.7 mm. Meanwhile, an ultrabroad bandwidth of 11.9 GHz (6.1-18 GHz) at the thickness range of 1-5 mm is also obtained. The excellent microwave absorption performance of these materials is ascribed to the multiple scatterings caused by 3D conductive foam structure, large attenuation as well as the balanced impedance match between dielectric loss and magnetic loss. This strategy might open an avenue to large-scale synthesization of various porous carbon-magnetic metal composites which can be a promising candidate for high-performance microwave absorber. (C) 2019 Elsevier Ltd. All rights reserved.