Ultra-light, high flexible and efficient CNTs/Ti₃C₂-sodium alginate foam for electromagnetic absorption application

Ultra-light carboxylic functionalized multi-walled carbon nanotubes (CNTs-COOH) and Ti₃C₂ MXene hybrids modified sodium alginate (CNTs/Ti₃C₂-SA) based composite foams were prepared through ice-templated freeze-drying method. The microstructure of the synthesized CNTs/Ti₃C₂ hybrids and CNTs/Ti₃C₂-SA foams is characterized by the presence of CNTs inserted between MXene layers which prevents their restacking. The resultant CNTs/Ti₃C₂ hybrids exhibit a unique sandwich-like hierarchical structure. Scanning electron microscopy (SEM) images show that the CNTs/Ti₃C₂-SA foam exhibits a heterogeneous anisotropic microstructure and CNTs/Ti₃C₂ hybrids are homogeneously dispersed in the skeleton of the porous foam. In case that the content of the hybrids amounts 40 mg/cm³, the CNTs/Ti₃C₂-SA foam possesses excellent electromagnetic (EM) absorption performance with a minimum reflection coefficient (RC_min) as low as -40.0 dB. In case of a sample thickness of 3.95 mm, the RC_min reaches -24.4 dB and the effective absorption bandwidth covers the whole X band from 8.2 to 12.4 GHz. A control test shows that, with the same absorbent content, the CNTs/Ti₃C₂-SA foam exhibits a far better EM performance than that of CNT-free Ti₃C₂-SA foam.