MXene@c-MWCNT Adhesive Silica Nanofiber Membranes Enhancing Electromagnetic Interference Shielding and Thermal Insulation Performance in Extreme Environments

A lightweight flexible thermally stable composite is fabricated by com-bining silica nanofiber membranes(SNM)with MXene@c-MWCNT hybrid film.The flexible SNM with outstanding thermal insulation are prepared from tetraethyl orthosilicate hydrolysis and condensation by electrospinning and high-temperature calcination;the MXene@c-MWCNT_(x:y)films are prepared by vacuum filtration tech-nology.In particular,the SNM and MXene@c-MWCNT_(6:4)as one unit layer(SMC_(1))are bonded together with 5 wt%polyvinyl alcohol(PVA)solution,which exhibits low thermal conductivity(0.066 W m^(-1)K^(-1))and good electromagnetic interference(EMI)shielding performance(average EMI SE_(T),37.8 dB).With the increase in func-tional unit layer,the overall thermal insulation performance of the whole composite film(SMC_(x))remains stable,and EMI shielding performance is greatly improved,especially for SMC_(3)with three unit layers,the average EMI SET is as high as 55.4 dB.In addition,the organic combination of rigid SNM and tough MXene@c-MWCNT_(6:4)makes SMC_(x)exhibit good mechanical tensile strength.Importantly,SMC_(x)exhibit stable EMI shielding and excellent thermal insulation even in extreme heat and cold environment.Therefore,this work provides a novel design idea and important reference value for EMI shielding and thermal insulation components used in extreme environmental protection equipment in the future.

Hollow Gradient-Structured Iron-Anchored Carbon Nanospheres for Enhanced Electromagnetic Wave Absorption

In the present paper,a microwave absorber with nanoscale gradient structure was proposed for enhancing the electromagnetic absorption performance.The inorganic-organic competitive coating strategy was employed,which can effectively adjust the thermodynamic and kinetic reactions of iron ions during the solvothermal process.As a result,Fe nanoparticles can be gradually decreased from the inner side to the surface across the hollow carbon shell.The results reveal that it offers an outstanding reflection loss value in combination with broadband wave absorption and flexible adjustment ability,which is superior to other relative graded distribution structures and satisfied with the requirements of lightweight equipment.In addition,this work elucidates the intrinsic microwave regulation mechanism of the multiscale hybrid electromagnetic wave absorber.The excellent impedance matching and moderate dielectric parameters are exhibited to be the dominative factors for the promotion of microwave absorption performance of the optimized materials.This strategy to prepare gradient-distributed microwave absorbing materials initiates a new way for designing and fabricating wave absorber with excellent impedance matching property in practical applications.

One-step wet-spinning assembly of twisting-structured graphene/carbon nanotube fiber supercapacitor

Graphene fiber-based supercapacitors hold great promise as flexible energy-storage devices. However, simultaneously achieving high ion-transport ability in electrode and electrolyte layer, which is crucial for realizing the high electrochemical performance, still remains challenging. Here, a facile and effective strategy to solve the problem was proposed by developing a twisting-structured graphene/carbon nanotube(CNT) fiber supercapacitor via one-step wet-spinning process with customized multi-channel spinneret.The remarkable structure features of the resulting fiber supercapacitor with wrinkled and thin electrolyte layer, and well-developed porosity of fiber electrode favored the rapid infiltration and transport of electrolyte ions inside the electrode, as well as between electrode and electrolyte, thus boosting high specific capacitance of 187.6 mF cm^(-2) and energy density of 30.2 μWh cm^(-2), and featuring long cycling life(93%capacitance retention after 10,000 cycles) and excellent flexibility. Moreover, the specific capacitance and energy density could be further improved to 267.2 m F cm^(-2) and 66.8 μWh cm^(-2), respectively, when Mn O2 was incorporated into the fiber.

Carbon nanotube fibers with excellent mechanical and electrical properties by structural realigning and densification

Floating catalysis chemical vapor deposition(FCCVD)direct spinning process is an attractive method for fabrication of carbon nanotube fibers(CNTFs).However,the intrinsic structural defects,such as entanglement of the constituent carbon nanotubes(CNTs)and inter-tube gaps within the FCCVD CNTFs,hinder the enhancement of mechanical/electrical properties and the realization of practical applications of CNTFs.Therefore,achieving a comprehensive reassembly of CNTFs with both high alignment and dense packing is particularly crucial.Herein,an efficient reinforcing strategy for FCCVD CNTFs was developed,involving chlorosulfonic acid-assisted wet stretching for CNT realigning and mechanical rolling for densification.To reveal the intrinsic relationship between the microstructure and the mechanical/electrical properties of CNTFs,the microstructure evolution of the CNTFs was characterized by cross-sectional scanning electron microscopy(SEM),wide angle X-ray scattering(WAXS),polarized Raman spectroscopy and Brunauer–Emmett–Teller(BET)analysis.The results demonstrate that this strategy can improve the CNT alignment and eliminate the inter-tube voids in the CNTFs,which will lead to the decrease of mean distance between CNTs and increase of inter-tube contact area,resulting in the enhanced inter-tube van der Waals interactions.These microstructural evolutions are beneficial to the load transfer and electron transport between CNTs,and are the main cause of the significant enhancement of mechanical and electrical properties of the CNTFs.Specifically,the tensile strength,elastic modulus and electrical conductivity of the high-performance CNTFs are 7.67 GPa,230 GPa and 4.36×10^(6)S/m,respectively.It paves the way for further applications of CNTFs in high-end functional composites.