Cellulose Nanofiber/Mxene Nanosheet/Nickel Chain Composite\nCarbon Foams for Electromagnetic Wave Absorption

Abstract

Developing\ncomposite carbon foams with multiple loss mechanisms\nand achieving stable and efficient electromagnetic wave absorption\nperformance in harsh environments remain challenges. In this study,\naqueous dispersions containing Ni²⁺ cellulose nanofiber\n(CNF) and Ti₃C₂T_<i>x</i> MXene were used to stabilize a styrene–butadiene–styrene\n(SBS) cyclohexane solution in the oil phase to form a Pickering emulsion\ngel. This gel was combined with freeze-drying and thermal annealing\nprocesses to synthesize nickel nanowires (Ni NWs) <i>in situ</i> within a three-dimensional pore structure at elevated temperatures,\nresulting in the production of C–CNF/MXene/Ni NW composite\ncarbon foams. In this process, carbonized CNF and SBS function as\nthree-dimensional scaffolds, while two-dimensional MXene sheets and <i>in situ</i> synthesized Ni NWs are uniformly integrated to establish\na conductive network with heterogeneous interfaces. The resultant\ncomposite carbon foam demonstrates stable microwave absorption properties,\nwith the C-C1M1N3 carbon foam achieving a minimum reflection loss\n(<i>RL</i>_min) of −45.2 dB at 13.6 GHz\nwhen the thickness is only 3.0 mm and a wide effective absorption\nbandwidth (EAB) of 7.6 GHz at the same thickness. Additionally, the\ncarbon foam exhibited excellent hydrophobicity and lipophilicity,\nindicating potential for oil–water separation applications.