Assembly of CoNi nanoparticles on Ketjenblack carbon with superior performance and optimized impedance matching for electromagnetic wave absorption

Nanocomposites of CoNi alloy nanoparticles loaded on Ketjenblack carbon (CoNi/KB) are successfully prepared through one-pot thermal decomposition of organic precursor solution. It can be proved, through a serious of characterization methods, that the introduction of porous carbon nanospheres with high specific surface area effectively prevents the serious agglomeration and oxidation of alloy nanoparticles. Highly dispersed CoNi alloy nanoparticles are evenly distributed on the surface of carbon nanospheres with a size of about ca. 5 nm. The CoNi/carbon nanosphere composites exhibit excellent electromagnetic wave absorbability when the doping mass is merely 15 wt% with the minimum reflection loss of -39.5 dB at 12.4 GHz and the effective absorption bandwidth (<-10.0 dB) is 5.6 GHz for a thickness of 2 mm. This study demonstrates that rational compositions, surface defects, mesoporous structure, enhanced interfacial polarization and synergistic effect can optimize impedance matching of CoNi/KB, and improve the wave absorption performance. Consequently, the CoNi/KB nanocomposites have vast potential applications as a novel high-efficiency microwave absorbing materials. (C) 2019 Elsevier B.V. All rights reserved.