Cellulose nanofibrils-based hybrid foam generated from Pickering emulsion toward high-performance microwave absorption.

The development of multifunctional microwave absorbers that worked in complex environments remains challenging. In this study, oil-in-water Pickering emulsion gelation approach was combined with freeze-drying to prepare foam-based microwave absorbers along with appealing photo-thermal conversion and thermal insulation. In hybrid foam, cellulose nanofibrils (CNF) and polylactic acid (PLA) serve as three-dimensional skeleton, where carbon nanotubes (CNT) and Fe3O4 nanoparticles are homogeneously incorporated, which forms a conductive network with hetero-interfaces. The optimal reflection loss value of the foam reaches -65.14 dB with a thickness of 3.0 mm. The foam also demonstrate high photo-thermal conversion performance with its surface temperature up to 97 °C after irradiation under 1 Sun for 5 min. Additionally, the foam shows superior thermal insulation comparing with the commercial polyvinyl alcohol and polyurethane foams. This study may offer a promising approach to develop ultralight and high-performance microwave absorber with great potential for multifunctional applications.