Yan-Fang Li,Li-Fang Wang,Shu-Juan Gao,Tan-Lai Yu,Qi-Feng Li,Jun-Wei Wang
A Co-doped porous carbon was successfully fabricated by a facile carbonizing procedure using coal hydrogasification semi-coke (SC) as the carbon and cobalt nitrate as the magnetic precursors, respectively. The mass ratio of the precursors was changed to regulate the microwave absorption (MA) capabilities. The favorable MA capabilities are a result of a synergistic interaction be-tween the dielectric loss from the carbon framework, the magnetic loss from nano-sized Co particles, and multiple scattering from the residual pores. At a thickness of 4.0 mm, the Co/C composite showed the lowest reflection loss of −33.45 dB when the initial mass ratio of cobalt nitrate and SC was 1:1. The effective absorbing bandwidth (EAB) could achieve 3.5 GHz at 2 mm thickness. This work not only opens up a new avenue for the facile fabrication of dielectric and magnetic loss combinations and their structural design, but it also creates a new route for the high value-added exploitation of SC.
Yanfang Li,Xiaoyun Li,Maoqing Kang,Yuhua Zhao,Qifeng Li,Junwei Wang
A series of microwave absorbers (SFs) were prepared using coal hydrogasification semi-coke as the carbon and ferric nitrate as the magnetic precursors. The absorbers were then incorporated to waterborne polyurethane to prepare composites (WSF). The microwave absorption performance of the composites can be tuned by adjusting the annealing temperature of the hybrids. The composite films can be fabricated to gradient or homogeneous structures by a facile viscosity-controlling method. The film with gradient structure is more conducive to alleviating the impedance mismatch and enhancing the attenuation. The WSF700 composite with gradient structure performs favorable MA property, with the minimum reflection loss of −42.08 dB and effective absorption bandwidth of 6.78 GHz at a thickness of 1.7 mm. The preparation strategy is rather facile, and the ingredients are inexpensive and easily accessible. This work shows great potential for the applications of the composites in MA coatings and flexible electronics.
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