Robust microwave absorption in silver-cobalt hollow microspheres with heterointerfaces and electric-magnetic synergism:Towards achieving lightweight and absorption-type microwave shielding composites

Lightweight and high-efficiency microwave shielding materials based on high absorption loss are the hotspot of current research.Herein,the silver-cobalt bimetallic hollow microspheres(Ag-Co-HM)with low reflection loss and broadband absorption efficiency were fabricated and then used to construct bimetallic hollow structures in polydimethylsiloxane/carbon nanotube composites(PDMS/CNT)to obtain the lightweight and absorption-type microwave shielding composites.The microwave absorption of Ag-Co-HM and the microwave shielding effectiveness(SE T)of the PDMS/CNT/Ag-Co-HM composites was evaluated and discussed.The Ag-Co-HM with a molar ratio(Co/Ag)of 2.07 exhibited a low reflection loss as-46.6 dB at a thickness of 2.6 mm,and an effective absorption bandwidth of 8.40 GHz.The SE T of the PDMS/CNT composites was greatly enhanced by the incorporation of the Ag-Co-HM.Furthermore,the absorption coefficient(A)was also improved by adding the Ag-Co-HM and was much higher than the reflection coefficient.The composites exhibited absorption-type microwave shielding composites.For example,the average microwave SE T of 59.4 dB and A value of 0.78 are achieved in the PDMS/CNT/Ag-Co-HM composites containing 5 wt%CNTs and 10 wt%Ag-Co-HMs,which are much higher than the cor-responding values of 33.7 dB and 0.63 in the PDMS/CNT composites with only 5 wt%CNTs.In addition,the hollow structure of Ag-Co-HM endows the PDMS/CNT/Ag-Co-HM composites to have a low density.