Advanced aerogel fibers possess numerousadvantages amalgamating the attributes of aerogels and fibermaterials, rendering them invaluable in the realm of thermalmanagement and regulation. However, the achievement ofrobust mechanical properties and increased temperaturestability is still a major challenge for the majority of aerogelfibers. Herein, SiO_(2)-Kevlar hybrid aerogel fibers with bioniccore-shell structure were prepared by reaction spinning andweaved into fabric. Kevlar nanowires dispersion is pumpedinto a bath comprising a self-synthesized silica sol, whichfacilitates the hybridization of biphasic aerogels through thegel reaction. Precise control over the diameter (200-800 μm)and structure of the wet gel fibers was achieved throughmeticulous adjustment of the spinning solution composition and spinning parameters. Subsequent freeze-drying processfacilitates the formation of a core-shell hybrid structure, in which the SiO_(2) aerogel layer effectively encapsulate the Kevlaraerogel core fiber. Taking full advantage of the mechanical properties of the Kevlar core fiber, the resulting SiO_(2)-Kevlaraerogel fibers exhibit commendable weaving characteristics (51.8 MPa). Furthermore, SiO_(2)-Kevlar aerogel fabrics exhibitenhanced thermal insulation characteristics with a thermal conductivity of 0.037 W/(m·K). As a result of the presence ofexternal SiO_(2) aerogel layer, the overall temperature resistance performance of the SiO_(2)-Kevlar fabric reach up to 700 ℃.
Thermal management system is highly desirable to guarantee the performance and thermal safety of lithium-ion batteries,but it reduces the energy density of battery modules and even is unable to provide highly effective protection.Here,a thermal management function integrated material is presented based on high-temperature resistant aerogel and phase change material and is applied at both charge–discharge process and thermal runaway condition.In this sandwich structure Paraffin@SiC nanowire/Aerogel sheet (denoted as PA@SAS) system,SiC nanowires endow the middle aerogel sheet (SAS) a dual nano-network structure.The enhanced mechanical properties of SAS were studied by compressive tests and dynamic mechanical analysis.Besides,the thermal conductivity of SAS at 600°C is only 0.042 W/(m K).The surface phase change material layers facilitate temperature uniformity of batteries (surface temperature difference less than 1.82°C) through latent heat.Moreover,a large-format battery module with four 58 Ah LiNi0.5Co0.2Mn0.3O2LIBs was assembled.PA@SAS successfully prevents thermal runaway propagation,yielding a temperature gap of 602°C through the 2 mm-thick cross section.PA@SAS also exhibits excellent performance in other safety issues such as temperature rise rate,flame heat flux,etc.The lightweight property and effective insulation performance achieves significant safety enhancement with mass and volume energy density reduction of only 0.79%and 5.4%,respectively.The originality of the present research stems from the micro and macro structure design of the proposed thermal management material and the combination of intrinsic advantages of every component.This work provides a reliable design of achieving the integration of thermal management functions into an aerogel composite and improves the thermal safety of lithium-ion batteries.
Sensors with enhanced biocompatibility, highsensitivity, and stable output have gained prominence with therapid advancement of piezoresistive sensor technologies.However, conventional piezoresistive sensors struggle to balance sensitivity and output stability. Here, we fabricated synergistic methylcellulose/chitosan MXene-based (MC/CS@MXene) aerogels through physical blending and freeze-drying,emulating the hollow bamboo structure. The aerogels formsynergistic interconnection via electrostatic adsorption andhydrogen bonding, endowing the aerogel-assembled resistivesensor with high sensitivity (2.90 kPa^(−1)), exceptional mechanical stability (8000 compression cycles at 10 kPa), andrapid response and recovery times (119 and 91 ms, respectively). A piezoresistive sensor array based on MC/CS/@MXene shows considerable potential for human–computerinteractions and wearable technologies. Furthermore, thesensor array can monitor real-time physiological signals ofcivil aviation pilots.
Graphene aerogel(GA)is a promising lightweight and high-performance material for electromagnetic wave absorption due to its ultra-light mass.However,the impedance matching and attenuation capabilities of GA are limited by its high conductivity and constrained attenuation paths.To address this limitation,magnetic materials are often combined with GA to enhance both impedance matching and attenuation performance.Nevertheless,little attention has been given to the influence of magnetic materials with varying morphologies on the electromagnetic wave absorption(EMA)properties.In this study,CoFe_(2)O_(4) nanofibers were prepared via electrospinning technology as an alternativeto commercial CoFe_(2)0_(4) nanoparticles.Subsequently,CoFe_(2)O_(4)@GA composites were synthesized through a hydrothermal reaction in a graphene oxide(GO)solution.Moreover,the inclusion of ethylene glycol in the GO solution helped regulate the volume shrinkage of GA after the adding of CoFe_(2)O_(4),thus preventing structural instability and fragmentation.The introduction of a small quantity of magnetic nanofibers significantly enhanced the EMA performance of the CoFe_(2)O_(4)@GA composite,increasing the strongest absorption from-34.5 to-53.5 dB and widening the maximum effective absorption bandwidth(EAB)from 8.0 to 8.7 GHz.Finally,the study revealed that CoFe_(2)O_(4) nanofibers outperformed nanoparticles in electromagnetic wave loss mechanisms,including magnetic coupling,magnetic resonance,eddy current loss,and interface polarization.This finding provides valuable insights for the selection and optimization of magnetic component morphologies in EMA materials.
Shuang XuQinghai LiuZhaoliang YuLijun LiXiaodong DaiShuyan YuCongju Li
With vigorous developments in nanotechnology,the elaborate regulation of microstructure shows attractive potential in the design of electromagnetic wave absorbers.Herein,a hierarchical porous structure and composite heterogeneous interface are constructed successfully to optimize the electromagnetic loss capacity.The macro–micro-synergistic graphene aerogel formed by the ice template‑assisted 3D printing strategy is cut by silicon carbide nanowires(SiC_(nws))grown in situ,while boron nitride(BN)interfacial structure is introduced on graphene nanoplates.The unique composite structure forces multiple scattering of incident EMWs,ensuring the combined effects of interfacial polarization,conduction networks,and magnetic-dielectric synergy.Therefore,the as-prepared composites present a minimum reflection loss value of−37.8 dB and a wide effective absorption bandwidth(EAB)of 9.2 GHz(from 8.8 to 18.0 GHz)at 2.5 mm.Besides,relying on the intrinsic high-temperature resistance of SiC_(nws) and BN,the EAB also remains above 5.0 GHz after annealing in air environment at 600℃ for 10 h.
Precise modulation of the pore structure and modification of the surface groups(–NH_(2))of MXene aerogels by the solid foaming method in combination with Na^(+)pre intercalation can significantly increase the layer spacing and change the electronic structure of MXene,thereby significantly optimizing its electrochemical performance.The three dimensional(3D)network structure provides numerous active sites on the surface of MXene and provides more ion transfer pathways and the large layer spacing allows electrolyte ions fast transport and the surface groups provide more active sites for the pseudocapacitive reaction.As a result,the prepared Na Ti_(3)C_(2)T_(x)(where T is–O,–OH,–F,and/or–NH_(2),and x represents the number of such groups)film aerogel delivers a high mass specific capacitance of 560 F·g^(-1) and excellent cycling performance of 94.5%capacitance retention after 12,000 cycles in 0.5 M H_(2)SO_(4).In addition,the flexible all-solid state supercapacitor(ASC)composed of MXene film electrodes has excellent specific capacitance~277 F·g^(-1) and high energy density~52.8 Wh·kg^(-1) at 1600 W·kg^(-1).Therefore,this work not only proposes a feasible synthetic method that can precisely regulate the pore structure and surface features of film aerogels,but also demonstrates the broad application prospects of aerogel materials in wearable power devices.
MXene,as a rising star among two-dimensional(2D)electromagnetic wave materials,faces urgent challenges in addressing its self-stacking issue and regulating its conductivity.Herein,a micro-macro collaborative design strategy was proposed to regulate heterogeneous interface engineering in MXene-based absorbers.Biomass-based cotton was introduced as three dimensional(3D)framework for constructing a porous structure,TiO_(2) was in-situ generated and nitrogen atom was doped on Ti_(3)C_(2)T_(x) MXene to regulate its dielectric properties,a 3D N-doped carbon fiber/MXene/TiO_(2)(CMT)nano-aerogel was successful constructed.The synergistic effects of diverse components and structural designs,porous frameworks and TiO_(2) lattice contraction can significantly adjust the density of the conductive network and create abundant heterogeneous interfaces,as well as the lattice defects induced by nitrogen atom doping can enhance polarization loss,ultimately leading to the excellent microwave absorption performance of 3D N-CMT nano-aerogels.The optimized N-CMT 30%aerogel exhibited a minimum reflection loss(RLmin)of−72.56 dB and an effective absorption bandwidth(EAB)of 6.92 GHz at 2.23 mm.Notably,when the thickness was adjusted from 1 to 5 mm,the EAB of the N-CMT 30%aerogel reached 13.94 GHz,achieving coverage of 98% of the C-band and the entire X and Ku bands.Furthermore,the attenuation capabilities of the N-CMT aerogel were further confirmed through RCS simulations,whose RCS reduction value reaches up to 19.969 dB·m^(2).These results demonstrate that 3D N-CMT nano-aerogel relying on interface engineering design exhibits significant potential in the field of electromagnetic protection,providing an important reference for future efficient absorbers.
Ying LiChunlei DongSijia WangDongyi LeiBinbin YinYifei CuiYanru WangRan Li
