Cellular-structured carbon nanotube composite films with broadband microwave absorption and shape memory

Carbon nanotube (CNT) composite films consisting of a microcellular structure are prepared by layer-by-layer deposition and phase separation processing. Polyvinyl butyral (PVB) and CNTs form a continuous network of cell walls of less than 100 nm thick and epoxy resin (EP) spheres of 4–6 μm in diameter constitute the cell cores with Ba-ferrite lamella aggregated among the cells. The layer-by-layer deposition of CNTs ensures a uniform dispersion of CNTs, and the EP spheres separate CNTs and Ba-ferrite to form a dielectric-magnetic coupling network. The resultant cell structure is conducive not only to achieve electromagnetic impedance matching but also to induce wave attenuation by multiple mechanisms. The composite film with optimal electromagnetic loss and impedance matching has a broad effective bandwidth of 11.5 GHz in microwave absorption at a thickness of only 0.3 mm, superior over most carbon-based microwave absorbing materials reported so far. In addition, the composite film also shows good thermal response for shape memory. This study provides a microcellular strategy for developing materials with light weight, thin thickness, broadband absorption, and shape memory for applications in civil and military fields.