A simple synthesis of magnetic metal implanted hierarchical porous carbon networks for efficient microwave absorption

Abstract

There still exist major challenges for the development of practical microwave absorbers, due to the great difficulty in fabricating highly efficient and lightweight microwave absorbers with strong absorbing ability and wide bandwidth for effective absorption at a low filler loading level. In this work, composite absorbers of hierarchical porous carbon networks embedded with magnetic metal nano sites (HPC/M) were successfully synthesized via simple freezing drying and carbonization process. Poly(vinylpyrrolidone) and sodium chloride were used as a cheap carbon source and a green template recyclable by washing, respectively. The composites could readily enable impedance matching and effectively boost the damping of microwaves, thus leading to a significantly enhanced performance for microwave absorption. For example, when evaluated as microwave absorbers with a low loading ratio of 20 wt%, the HPC/Ni composite delivered a superb absorption intensity with a minimum reflection loss (RL_min) of −58.7 dB and a wide microwave absorption bandwidth of 3.7 GHz, and the HPC/Co exhibited a remarkable RL_min of −50.2 dB with a broad effective absorption bandwidth (EAB) of 4.9 GHz at a thickness of 1.7 mm. This method provides a simple and extendible approach for tailoring high performance microwave absorption materials at the nano–macro scale.