Excellent microwave absorbing and electromagnetic shielding performance of grown MWCNT on activated carbon bifunctional composite

Various materials are being explored to efficiently work either as microwave (MW) absorbing material or EMI shielding materials. In the present study, we have reported a bifunctional composite material made by growing MWCNTs on waste biomass derived activated carbon (ACNT), which can be used for both microwave absorption and EMI shielding applications. The ACNT at 10 wt% (ACNT10) filler loading demonstrated an effective absorption bandwidth (EAB) of 5.8 GHz at 1.98 mm thickness which covered 96.6% of K-u band, whereas at 2.85 mm thickness it covered entire X band (8-12.25 GHz). A maximum reflection loss (RLmax) of -27.6 dB at 16.16 GHz was achieved by ACNT10 at 1.83 mm thickness. At the same time by increasing ACNT loading to 25 wt%, the increase in conductivity and charge transport was observed, due to which ACNT25 displayed an outstanding EMI shielding performance and achieved total EMI shielding effectiveness (SET) of 137 dB. Thus, by tuning the loading of ACNT, the absorber material can be converted from MW absorption to high performance EMI shielding material.