Ultralight aerogel sphere composed of nanocellulose-derived carbon nanofiber and graphene for excellent electromagnetic wave absorption

A novel type of three-dimensional ultralight aerogel sphere,consisting of one-dimensional nanocellulose-derived carbon fibers and two-dimensional graphene layers,was prepared based on a developed drop-freeze-drying followed by carbonization approach.The nanofibrous carbon efficiently prevents the agglomeration of the graphene layers,which,in turn,reduces the shrinkage and maintains the structural stability of the hybrid carbon aerogel spheres.Consequently,the aerogel spheres showing an ultralow-density of 2.8 mg/cm^(3) and a porosity of 99.98%accomplish the tunable dielectric property and electromagnetic wave(EMW)absorption performance.The high-efficiency utilization of biomass-derived fibrous nanocarbon,graphene,the porous structure of the hybrid aerogel spheres leads to the excellent EMW absorption performance.The aerogel spheres display an effective absorption bandwidth of 6.16 GHz and a minimum reflection loss of−70.44 dB even at a filler loading of merely 3 wt.%,significantly outperforming that of other biomass-derived carbon-based EMW absorbing materials.This work offers a feasible,facile,scalable approach for fabricating high-performance and sustainable biomass-based aerogels,suggesting a tremendous application potential in EMW absorption and aerospace.

超细纤维素纳米晶增强MXene仿生复合材料的多功能电磁屏蔽性能

聚合物用于改善过渡金属碳化物和/或氮化物(MXenes)的力学性能、构建高性能电磁(EMI)屏蔽结构面临以下挑战:绝缘聚合物对MXene基复合材料导电性和电磁屏蔽性能的影响以及聚合物的不可再生性.本文将一维、超细、可持续的纤维素纳米晶体(CNCs)用于增强MXene纳米片,从而制备出高强度、高柔性、同时兼顾优异导电性和电磁屏蔽效能(SE)的仿生复合材料,其性能优于目前报道的聚合物复合材料.在厚度仅为2–14μm的情况下,MXene/CNC纳米复合材料的电磁屏蔽效能分别达到30–66 d B,比屏蔽效能和面比屏蔽效能分别达到15,155 d B mm^(-1)和54,125 d B cm^(2)g^(-1).复合薄膜具有良好的光热性能,扩展了其应用场景.结合简便、高效、可规模化的常压干燥制备方法得到的超薄、柔韧、高强度、多功能的CNC增强MXene基仿生薄膜在下一代先进电子或航空航天领域显示出巨大的应用潜力.

Biopolymer-Based Aerogels for Electromagnetic Wave Shielding and Absorbing

The rapid development of communication technology and electronic industry has brought unprecedented serious electromagnetic interference(EMI)and electromagnetic wave(EMW)pollution.Although EMI shields and EMW absorbers based on metal or magnetic materials were used to solve these problems,they have long been criticized for their high price,high density and easy corrosion.In order to achieve low density and efficient dissipation of electromagnetic energy,aerogels stand out among manifold materials.However,constructing aerogels with good EMI shielding or EMW absorption performance and acceptable mechanical properties is not an easy task.Burgeoning biopolymers,such as cellulose,lignin,chitin/chitosan and alginate,breathe new life into aerogels for high-efficiency EMW shielding and absorbing.Here,we reviewed the contributions of biopolymers in the fields of aerogels for EMW shielding and absorbing.At the same time,some challenges and outlook were also pointed out,aiming to promote the advance of aerogel-based EMI shields and EMW absorbers as well as the rational utilization of biopolymers.

Nanocellulose-assisted preparation of electromagnetic interference shielding materials with diversified microstructure

Sustainable and renewable nanocellulose attracts more and more attention in various fields due to its high strength-to-weight ratio,small diameter,large aspect ratio,and abundant functional groups.The excellent properties and structural characteristics enabled a great potential of nanocellulose for efficient interactions with functional nanomaterials such as carbon nanotube,graphene,transition metal carbides/nitrides(MXenes),and metal nanoparticles,which is beneficial for preparing high-performance electromagnetic interference(EMI)shields.We review the advances in the nanocelluloseassisted preparation of composite films and aerogels for EMI shielding application.The nanocellulose-based composites are evaluated in terms of their EMI shielding performance and the shielding mechanisms,including conduction,polarization,and multiple reflections are summarized.In addition to the constituent structure and contents,we highlight the significance of the microstructure design in enhancing the EMI shielding performance of the nanocellulose-based EMI shields.Finally,the current challenges and outlook for these fascinating nanocellulose-based EMI shielding composites are discussed.