82 / 2021-06-14 09:24:32

Nanocellulose-Assisted Lightweight Aerogels with Orientated Biomimetic Cell Walls for High-Performance Electromagnetic Interference Shielding

lightweight,porous materals,MXene,nanocellulose,EMI shielding

Lightweight nanostructured aerogels have attracted more and more attention for addressing emergency electromagnetic radiation or interference thanks to their high and controllable electromagnetic interference (EMI) shielding performances arising from cellular structure and nanoscale building blocks thereof including their synergistic interactions. Efficient design and utilization of cellular morphologies and functional nanomaterials for higher EMI shielding effectiveness (SE) at lower material consumption is always the research trend yet remains challenging. Recently, novel two-dimensional (2D) transmission metal carbides and nitrides (MXenes) sheets, commonly known as Ti₃C₂T_x MXenes, have attracted attention for constructing high-performance EMI shielding materials due to the metallic conductivity and the solution processability derived from their hydrophilic functional groups (-F, -O, -OH). Nevertheless, the main challenge for constructing lightweight, high-performance MXene based shields is the weak gelation ability of MXenes, resulting in inferior mechanical performance of the corresponding macrostructures. Here, we employed thin-dimension cellulose nanofibrils (CNFs) for assisting in building ultralow-density, robust, and highly flexible MXene aerogels with orientated biomimetic hybrid cell walls. The ultrathin cell walls with nanoscale MXene “bricks” bonded by nanoscale CNF “mortar” maintain high electrical conductivity of MXene and enhance significantly the mechanical strength of MXene/CNF hybrid aerogels. High conductivity and introduced interfaces between MXenes and CNFs lead to high intrinsic shielding ability of cell walls, which can be amplified by the cellular structures in the aerogels. Particularly, a significant influence of angles between cell walls' orientated direction and electric field direction of incident EM waves on EMI shielding performance is displayed. This provides an intriguing and crucial concept for controlling EMI shielding performance based on the microstructural design strategy in EMI shielding applications. Taking completely advantage of the biomimetic cell walls and cellular structure, EMI SE of the MXene/CNF hybrid aerogels can reach as high as 74.6 or 35.5 dB at densities of merely 8.0 or 1.5 mg/cm3, respectively. The normalized surface specific SE (defined as the SE divided by the material density and thickness) are up to 189400 dB·cm2/g, significantly exceeds that of other EMI shielding materials reported so far. This work thus suggests a convenient, facile, low-cost, and scalable preparation approach for constructing high-performance MXene macrostructures with potential applications in next-generation lightweight, flexible electronic devices and aerospace.



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