Preparation of hierarchically porous carbon/magnetic particle composites with broad microwave absorption bandwidth

Abstract

Hierarchically porous carbon/magnetic particle composites have been successfully prepared via drying the gels of gelatin/metal nitrates and subsequent carbonization process. The micro-scale pores are formed due to the self-foaming of the gels during the drying process. At the early stage of carbonization process, metal nitrates are converted into metal oxides rapidly. Then the nano-scale pores are generated via the etching reaction between the gelatin-derived carbon and the nucleated metal oxides induced by gelatin with the elongation of carbonization process. Eventually, the nucleated metal oxides are further reduced by gelatin-derived carbon to form carbon/magnetic particle composites. The superimposed effects between heterogeneous chemical components and hierarchical porosity endow the absorbent with excellent microwave absorption (MA) performance. A maximum reflection loss (RL) of −57.1 dB and a broad effective absorption bandwidth (EAB) of 8.16 GHz are achieved in the hierarchically porous C/Fe3C composites. Similarly, the broad EABs of 6.32 and 8.80 GHz can be gained by drying and carbonization of gelatin/cobalt nitrate and gelatin/nickel nitrate gels, respectively. All the results demonstrate that the combination of hierarchically porous structures and dual loss components is a promising strategy for the preparation of high-performance MA materials with broad EAB.