Corncob-derived hierarchical porous carbon/Ni composites for microwave absorbing application

Abstract

The pore structure and the large surface area have an important role on enhancing microwave absorption performances. It is still a challenge for adjusting pore structure and surface area by a simple method. Hierarchical porous carbon/Ni composites have been fabricated by carbonizing corncob under Ar atmosphere. The pore diameter, surface area and the size of Ni particles can be adjusted by controlling ball milling time. With increasing ball milling time, the surface area increases, pore diameter and Ni particle size drops, resulting in the multi-reflection and absorption of incident electromagnetic wave and the increase of interface between Ni and carbon. The improved electromagnetic loss ability and the optimal impedance matching accompanied with the large surface area, the small pore diameter and Ni particles lead to the good microwave absorbing behaviors. The composite with 2 h ball milling at 1.7 mm possesses the optimal overall microwave absorbing behaviors (117.7 dB GHz of absorption capacity, 69.24 dB GHz/mm of absorption efficiency, 5.0 GHz of effective absorption bandwidth and −42.51 dB of the maximal reflection loss).