Electromagnetic interference(EMI)shielding materials with superior shielding efficiency and low-reflection properties hold promising potential for utilization across electronic components,precision instruments,and fif...Electromagnetic interference(EMI)shielding materials with superior shielding efficiency and low-reflection properties hold promising potential for utilization across electronic components,precision instruments,and fifth-generation communication equipment.In this study,multistage microcellular waterborne polyurethane(WPU)composites were constructed via gradient induction,layer-by-layer casting,and supercritical carbon dioxide foaming.The gradient-structured WPU/ironcobalt loaded reduced graphene oxide(FeCo@rGO)foam serves as an impedance-matched absorption layer,while the highly conductive WPU/silver loaded glass microspheres(Ag@GM)layer is employed as a reflection layer.Thanks to the incorporation of an asymmetric structure,as well as the introduction of gradient and porous configurations,the composite foam demonstrates excellent conductivity,outstanding EMI SE(74.9 dB),and minimal reflection characteristics(35.28%)in 8.2-12.4 GHz,implying that more than 99.99999%of electromagnetic(EM)waves were blocked and only 35.28%were reflected to the external environment.Interestingly,the reflectivity of the composite foam is reduced to 0.41%at 10.88 GHz due to the resonance for incident and reflected EM waves.Beyond that,the composite foam is characterized by low density(0.47 g/cm^(3))and great stability of EMI shielding properties.This work offers a viable approach for craft-ing lightweight,highly shielding,and minimally reflective EMI shielding composites.展开更多
With the rapid development of 5G communication technology and wearable electronic devices,the demand for low-reflection electromagnetic interference(EMI)shielding materials is becoming increasingly urgent.In this work...With the rapid development of 5G communication technology and wearable electronic devices,the demand for low-reflection electromagnetic interference(EMI)shielding materials is becoming increasingly urgent.In this work,reduced graphene oxide-MXene(rGMH)@FeNi/epoxy EMI shielding composites with a regular honeycomb structure were successfully prepared by the combination of surface functionalization modification,sacrificial template,and freeze-drying.The effects of magnetic FeNi alloy particle loading mode and loading amount on the EMI shielding performance of composites were investigated.The results show that rGMH@FeNi/epoxy EMI shielding composites have the highest EMI shielding effectiveness(EMI SE)and the lowest reflection shielding effectiveness when magnetic FeNi alloy particles are loaded only on the graphene skeleton.In this composite,the EMI SE value of the composite is 61 dB when the rGMH@FeNi mass fraction is 5.4 wt%(f-FeNi mass fraction is 0.9 wt%),which is 4.7 times that of the blended rGO/MXene/FeNi/epoxy resin composite(13 dB)with the same mass fraction.At the same time,the rGMH@FeNi/epoxy composite has excellent thermal stability(heat-resistance index of 190.3℃)and mechanical properties(energy storage modulus of 8606.7 MPa).These polymer-based EMI shielding composites with excellent EMI shielding properties and low reflection effectiveness have great potential in the protection of high-power,portable and wearable electronic devices against electromagnetic pollution.展开更多
Although multifunctional electromagnetic interference(EMI)shielding materials with ultrahigh electromagnetic wave absorption are highly required to solve increasingly serious electromagnetic radiation and pollution an...Although multifunctional electromagnetic interference(EMI)shielding materials with ultrahigh electromagnetic wave absorption are highly required to solve increasingly serious electromagnetic radiation and pollution and meet multi-scenario applications,EMI shielding materials usually cause a lot of reflection and have a single function.To realize the broadband absorption-dominated EMI shielding via absorption-reflection-reabsorption mechanisms and the interference cancelation effect,multifunctional asymmetric bilayer aerogels are designed by sequential printing of a MXene-graphene oxide(MG)layer with a MG emulsion ink and a conductive MXene layer with a MXene ink and subsequent freeze-drying for generating and solidifying numerous pores in the aerogels.The top MG layer of the asymmetric bilayer aerogel optimizes impedance matching and achieves re-absorption,while the bottom MXene layer enhances the reflection of the incident electromagnetic waves.As a result,the asymmetric bilayer aerogel achieves an average absorption coefficient of 0.95 in the X-band and shows the tunable absorption ability to electromagnetic wave in the ultrawide band from 8.2 to 40 GHz.Finite element simulations substantiate the effectiveness of the asymmetric bilayer aerogel for electromagnetic wave absorption.The multifunctional bilayer aerogels exhibit hydrophobicity,thermal insulation and Joule heating capacities and are efficient in solar-thermal/electric heating,infrared stealth,and clean-up of spilled oil.展开更多
In this paper,a sparse graph neural network-aided(SGNN-aided)decoder is proposed for improving the decoding performance of polar codes under bursty interference.Firstly,a sparse factor graph is constructed using the e...In this paper,a sparse graph neural network-aided(SGNN-aided)decoder is proposed for improving the decoding performance of polar codes under bursty interference.Firstly,a sparse factor graph is constructed using the encoding characteristic to achieve high-throughput polar decoding.To further improve the decoding performance,a residual gated bipartite graph neural network is designed for updating embedding vectors of heterogeneous nodes based on a bidirectional message passing neural network.This framework exploits gated recurrent units and residual blocks to address the gradient disappearance in deep graph recurrent neural networks.Finally,predictions are generated by feeding the embedding vectors into a readout module.Simulation results show that the proposed decoder is more robust than the existing ones in the presence of bursty interference and exhibits high universality.展开更多
Brain lesions,such as those caused by stroke or traumatic brain injury(TBI),frequently result in persistent motor and cognitive impairments that significantly affect the individual patient's quality of life.Despit...Brain lesions,such as those caused by stroke or traumatic brain injury(TBI),frequently result in persistent motor and cognitive impairments that significantly affect the individual patient's quality of life.Despite differences in the mechanisms of injury,both conditions share a high prevalence of motor and cognitive impairments.These deficits show only limited natural recovery.展开更多
To investigate the effects of mRNA interference on aquaporin-4 expression in swollen tissue of rats with ischemic cerebral edema, and diagnose the significance of diffusion-weighted MRI, we injected 5 pL shRNA- aquapo...To investigate the effects of mRNA interference on aquaporin-4 expression in swollen tissue of rats with ischemic cerebral edema, and diagnose the significance of diffusion-weighted MRI, we injected 5 pL shRNA- aquaporin-4 （control group） or siRNA- aquaporin-4 solution （1：800） （RNA interference group） into the rat right basal ganglia immediately before occlusion of the middle cerebral artery. At 0.25 hours after occlusion of the middle cerebral artery, diffusion-weighted MRI displayed a high signal; within 2 hours, the relative apparent diffusion coefficient decreased markedly, aquaporin-4 expression increased rapidly, and intracellular edema was obviously aggravated; at 4 and 6 hours, the relative apparent diffusion coefficient slowly returned to control levels, aquaporin-4 expression slightly increased, and angioedema was observed. In the RNA interference group, during 0.25- 6 hours after injection of siRNA- aquaporin-4 solution, the relative apparent diffusion coefficient slightly fluctuated and aquaporin-4 expression was upregulated; during 0.5 4 hours, the relative apparent diffusion coefficient was significantly higher, while aquaporin-4 expression was significantly lower when compared with the control group, and intracellular edema was markedly reduced; at 0.25 and 6 hours, the relative apparent diffusion coefficient and aquaporin-4 expression were similar when compared with the control group; obvious angioedema remained at 6 hours. Pearson＇s correlation test results showed that aquaporin-4 expression was negatively correlated with the apparent diffusion coefficient （r = -0.806, P 〈 0.01）. These findings suggest that upregulated aquaporin-4 expression is likely to be the main molecular mechanism of intracellular edema and may be the molecular basis for decreased relative apparent diffusion coefficient. Aquaporin-4 gene interference can effectively inhibit the upregulation of aquaporin-4 expression during the stage of intracelfular edema with time-effectiveness. Moreover, diffusion-weighted MRI can accurately detect intracellular edema.展开更多
An electromagnetic interference （EMI） shielding composite based on ultrahigh molecular weight polyethylene （UHMWPE） loaded with economical graphite-carbon black （CB） hybrid fillers was prepared via a green and f...An electromagnetic interference （EMI） shielding composite based on ultrahigh molecular weight polyethylene （UHMWPE） loaded with economical graphite-carbon black （CB） hybrid fillers was prepared via a green and facile methodology, i.e., high-speed mechanical mixing combined with hot compression thus avoiding the assistance of the intensive ultrasound dispersion in volatile organic solvents. In this composite, the graphite-CB hybrid fillers were selectively distributed in the interfacial regions of UHMWPE domains resulting a typical segregated structure. Thanks to the specific morphology of segregated conductive networks along with the synergetic effect of large-sized graphite flakes and small-sized CB nanoparticles, a low filler loading of 7.7 vol% （15 wt%） yielded the graphite-CB/UHMWPE composites with a satisfactory electrical conductivity of 33.9 S/m and a superior shielding effectiveness of 40.2 dB, manifesting the comparable value of the pricey large-aspect-ratio carbon nanofillers （e.g., carbon nanotubes and graphene nanosheets） based polymer composites. More interestingly, with the addition of 15 wt% graphite-CB （1/3, W/W） hybrid fillers, the tensile strength and elongation at break of the composite reached 25.3 MPa and 126%, respectively; with a remarkable increase of 58.1% and 2420% over the conventional segregated graphite/UHMWPE composites. The mechanical reinforcement could be attributed to the favor of the small-sized CB particles in the polymer molecular diffusion between UHMWPE domains which in tuna provided a stronger interfacial adhesion. This work provides a facile, green and affordable strategy to obtain the polymer composites with high electrical conductivity, efficient EMI shielding, and balanced mechanical performance.展开更多
In this paper, we exploit clustered interference alignment(IA) for efficient subchannel allocation in ultra-dense orthogonal frequency division multiplexing access(OFDMA) based femtocell networks, which notably improv...In this paper, we exploit clustered interference alignment(IA) for efficient subchannel allocation in ultra-dense orthogonal frequency division multiplexing access(OFDMA) based femtocell networks, which notably improves the spectral efficiency as well as addresses the feasibility issue of IA. Our problem is formulated as a combinatorial optimization problem which is NP-hard. To avoid obtaining its optimal solution by exhaustive search, we propose a two-phases efficient solution with low-complexity. The first phase groups all the femtocell user equipments(FUEs) into disjoint clusters, and the second phase allocates subchannels to the formed clusters where IA is performed. By doing this, the intra-cluster and inter-cluster interferences are mitigated by clustered IA and subchannel allocation in ultra-dense femtocell networks, respectively.Also, low-complexity algorithm is proposed to solve the corresponding sub-problem in each phase. Simulation results demonstrate that the proposed scheme not only outperforms other related schemes, but also provides a close performance to the optimal solution.展开更多
With the rapid development of fifth-generation mobile com-munication technology and wearable electronic devices,electromagnetic interference and radiation pollution caused by electromagnetic waves have attracted world...With the rapid development of fifth-generation mobile com-munication technology and wearable electronic devices,electromagnetic interference and radiation pollution caused by electromagnetic waves have attracted worldwide attention.Therefore,the design and development of highly efficient EMI shielding materials are of great importance.In this work,the three-dimensional graphene oxide(GO)with regular honeycomb structure(GH)is firstly constructed by sacrificial template and freeze-dry-ing methods.Then,the amino functionalized FeNi alloy particles(f-FeNi)are loaded on the GH skeleton followed by in-situ reduction to prepare rGH@FeNi aerogel.Finally,the rGH@FeNi/epoxy EMI shielding com-posites with regular honeycomb structure is obtained by vacuum-assisted impregnation of epoxy resin.Benefitting from the construction of regular honeycomb structure and electromagnetic synergistic effect,the rGH@FeNi/epoxy composites with a low rGH@FeNi mass fraction of 2.1 wt%(rGH and f-FeNi are 1.2 and 0.9 wt%,respectively)exhibit a high EMI shielding effectiveness(EMI SE)of 46 dB,which is 5.8 times of that(8 dB)for rGO/FeNi/epoxy composites with the same rGO/FeNi mass fraction.At the same time,the rGH@FeNi/epoxy composites also possess excellent thermal stability(heat-resistance index and temperature at the maximum decomposition rate are 179.1 and 389.0°C respectively)and mechanical properties(storage modulus is 8296.2 MPa).展开更多
Current researches have not yet found the effect law of the cutter parameters and machining parameters on the interference in gear slicing,the interference between the cutter and machined gear often happens because th...Current researches have not yet found the effect law of the cutter parameters and machining parameters on the interference in gear slicing,the interference between the cutter and machined gear often happens because the appropriate cutter parameters and machining parameters cannot be set,which reduces the gear machining accuracy.The relative position between the major flank face and edge-sweeping surface,distribution law of the interference area in forming process of edge-sweeping surface,and effect law of relative positions among edge-sweeping surfaces on the interference are studied by graphical analysis.The effect law of the cutter parameters and machining parameters on the interference is found.The effect law shows that the interference in gear slicing can be controlled when the relief angle measured on the top edge and feed of every rotation are chosen respectively larger than 9~and smaller than 0.15 mrn/r.An internal helical gear is sliced with the spur slice cutter and the cutter parameters and machining parameters are set based on above the effect law.The machined gear is measured in Gear Measuring Center and the detection result shows that the comprehensive accuracy reaches GB/T Class 7,where some reach GB/T Class 6.The result can meet the gear machining accuracy requirement and shows that the effect law found is valid.The problem of the interference in gear slicing is solved and the gear machining accuracy can be improved.展开更多
Although electrically conductive and hydrophilic MXene sheets are promising for multifunctional fibers and electronic textiles,it is still a challenge to simultaneously enhance both conductivity and mechanical propert...Although electrically conductive and hydrophilic MXene sheets are promising for multifunctional fibers and electronic textiles,it is still a challenge to simultaneously enhance both conductivity and mechanical properties of MXene fibers because of the high rigidity of MXene sheets and insufficient inter-sheet interactions.Herein,we demonstrate a core-shell wet-spinning methodology for fabricating highly conductive,super-tough,ultra-strong,and environmentally stable Ti_(3)C_(2)T_(x) MXene-based core-shell fibers with conductive MXene cores and tough aramid nanofiber(ANF)shells.The highly orientated and low-defect structure endows the ANF@MXene core-shell fiber with supertoughness of~48.1 MJ m^(-3),high strength of~502.9 MPa,and high conductivity of~3.0×10^(5)S m^(-1).The super-tough and conductive ANF@MXene fibers can be woven into textiles,exhibiting an excellent electromagnetic interference(EMI)shielding efficiency of 83.4 dB at a small thickness of 213μm.Importantly,the protection of the ANF shells provides the fibers with satisfactory cyclic stability under dynamic stretching and bending,and excellent resistance to acid,alkali,seawater,cryogenic and high temperatures,and fire.The oxidation resistance of the fibers is demonstrated by their wellmaintained EMI shielding performances.The multifunctional core-shell fibers would be highly promising in the fields of EMI shielding textiles,wearable electronics and aerospace.展开更多
The utilization of eco-friendly,lightweight,high-efficiency and high-absorbing electromagnetic interference(EMI)shielding composites is imperative in light of the worldwide promotion of sustainable manufacturing.In th...The utilization of eco-friendly,lightweight,high-efficiency and high-absorbing electromagnetic interference(EMI)shielding composites is imperative in light of the worldwide promotion of sustainable manufacturing.In this work,magnetic poly(butyleneadipate-coterephthalate)(PBAT)microspheres were firstly synthesized via phase separation method,then PBAT composite foams with layered structure was constructed through the supercritical carbon dioxide foaming and scraping techniques.The merits of integrating ferroferric oxideloaded multi-walled carbon nanotubes(Fe3O4@MWCNTs)nanoparticles,a microcellular framework,and a highly conductive silver layer have been judiciously orchestrated within this distinctive layered configuration.Microwaves are consumed throughout the process of“absorption-reflection-reabsorption”as much as possible,which greatly declines the secondary radiation pollution.The biodegradable PBAT composite foams achieved an EMI shielding effectiveness of up to 68 dB and an absorptivity of 77%,and authenticated favorable stabilization after the tape adhesion experiment.展开更多
In order to investigate the influence of silencing soluble epoxide hydrolase（sEH） with double-stranded small interfering RNA（siRNA） on cardiomyocytes apoptosis induced by doxorubicin（DOX）,two plasmids containing...In order to investigate the influence of silencing soluble epoxide hydrolase（sEH） with double-stranded small interfering RNA（siRNA） on cardiomyocytes apoptosis induced by doxorubicin（DOX）,two plasmids containing siRNA sequences specific to sEH were constructed and transfected into the primary cultured cardiomyocytes by using FuGENE HD transfection agents.The mRNA and protein expression levels of sEH were detected by semiquantitative RT-PCR and Western blotting respectively,and the plasmids that silenced sEH most significantly were selected,and renamed EH-R.The plasmids carrying a nonspecific siRNA coding sequence（PCN） served as the negative control.Cardiomyocytes were divided into four groups：control group,DOX group,PCN＋DOX group,and EH-R＋DOX group.Apoptosis of cardiomyocytes was induced by DOX at a concentration of 1 μmol/L.Apoptosis rate of cardiomyocytes was determined by flow cytometery.The protein expression levels of Bcl-2 and Bax were detected by Western blotting.The results showed that the expression of sEH was down-regulated by EH-R plasmid.The expression levels of sEH mRNA and protein in the EH-R＋DOX group were significantly decreased as compared with other groups（P0.01）.As compared with the control group,the apoptosis rate of cardiomyocytes in three DOX-treated groups was obviously increased,the expression levels of Bax increased,and those of Bcl-2 decreased（P0.01）.However,the expression levels of Bax were decreased,those of Bcl-2 increased and the apoptosis rate of cardiomyocytes obvi-ously decreased in EH-R＋DOX group when compared with those in the DOX group and the PCN＋DOX group（P0.01 for each）.It was concluded that the recombinant plasmids could be successfully constructed,and transfected into the primary cultured cardiomyocytes.They could ameliorate the DOX-induced cardiomyocytes apoptosis by selectively inhibiting the expression of sEH with RNAi and increasing the expression of Bcl-2.展开更多
Flexible, lightweight, robust and versatile properties are essential for the next generation of wearable as well as intelligent electromagnetic interference(EMI) shielding materials. In this work, multilayered films c...Flexible, lightweight, robust and versatile properties are essential for the next generation of wearable as well as intelligent electromagnetic interference(EMI) shielding materials. In this work, multilayered films containing cellulose nanofiber(CNF) layers, CNF/MXene layers, and CNF/silver nanowires(CNF/Ag NWs)layers were fabricated by an efficient and easy-to-use vacuum filtration method. Compared with a uniformly mixed film, the resultant layered composite films that loaded with a low MXene and AgNWs content exhibit superior mechanical properties with a tensile strength of 137 MPa, a strain at break of 5.7%, excellent EMI shielding effectiveness(EMI SE) of 61.9 d B, and higher EMI SE/t of 20,653 d B cm^(-1).This is attributed to the high-performance CNF substrate, the highly efficient layered structures, and extensive hydrogen-bonding interactions. In particular, a high degree of ohmic loss of multiple interfaces and polarization relaxation of local defects, as well as an abundance of terminal groups, favor the loss of electromagnetic waves(EMW) within the material. In addition, the prepared multifunctional layered composite films also show good antibacterial properties. As a result, the obtained new kind of flexible layered structure EMI shielding composite films with excellent EMI shielding performance, and mechanical properties present promising application prospects in the fields of EMI shielding and protection for aerospace, portable, and wearable flexible electronic devices.展开更多
Integrating smart functions into one flexible electronic is vastly valuable in improving their working performances and broadening applications.Here,this work reports a ultraflexible,highly efficient electromagnetic i...Integrating smart functions into one flexible electronic is vastly valuable in improving their working performances and broadening applications.Here,this work reports a ultraflexible,highly efficient electromagnetic interference(EMI)shielding,and self-healable triboelectric nanogenerator(TENG)that is assembled by modified Ti_(3)C_(2)T_(x) MXene(m-MXene)-based nanocomposite elastomers.Benefitting from the excellent electronegativity of m-MXene,the single-electrode mode-based TENG can generate high open-circuit voltage(V_(oc))oscillating between-65 and 245 V,high short-circuit current(I_(sc))of 29 μA,and an instantaneously maximum peak power density of 1150 mW m^(-2) that can power twenty light-emitting diodes(LEDs).Moreover,the resultant TENG possesses outstanding EMI shielding performance with the maximum shielding effectiveness of 48.1 dB in the X-band.The enhanced shielding capability is dominated by the electromagnetic absorption owning to high conduction loss in m-MXene network,multiple reflections between m-MXene sheets,and polarization effect on the surface of m-MXene sheets.Additionally,a self-powered wearable sensor is fabricated based on the as-prepared TENG.The sensor shows an intrinsic healing ability with healing efficiency of 98.2% and can accurately detect the human large-scale motions and delicate physical signal.This work provides an enhanced way to fabricate the wearable electronics integrated with smart functions,and the reported MXene-based TENG may have a broad prospect in the fields of aerospace,artificial intelligence,and healthcare systems.展开更多
Lightweight,flexible,ultrahigh-performance electromagnetic-interfe rence(EMI)shielding materials are urgently required in the areas of aircraft/aerospace,portable and wearable electronics.Herein,1 D carbon nanotubes(C...Lightweight,flexible,ultrahigh-performance electromagnetic-interfe rence(EMI)shielding materials are urgently required in the areas of aircraft/aerospace,portable and wearable electronics.Herein,1 D carbon nanotubes(CNT)and carbon nanofibers(CNF)with 2 D edge-rich graphene(ERG)are used to form a lightweight,flexible CNT-ERG-CNF hybrid foam.This foam was fabricated through a self-sacrificial templating chemical vapor deposition process,where nanocarbons bond through covalent bonding,forming a hierarchical 3 D hybridized carbon nanostructure.Multistage conductive networks and heterogeneous interfaces were constructed using edge-rich nanocarbons to increase the induced currents and interfacial polarization which makes great contributions to achieve high absorption electromagnetic shielding effectiveness(SEA).The CNT-ERG-CNF hybrid foam exhibits EMI shielding effectiveness(SE)exceeding55.4 dB in the X-band while the specific SE(SSE,SE divided by mass density)achieves 9200 dB cm^(3)g^(-1),which surpasses that of nearly all other carbon-based composite materials.Furthermore,the structural stability and durability of the flexible CNT-ERG-CNF hybrid foams is examined by measuring EMI SE after 10000 times cyclic bending.Remarkably,this work not only provides a new idea for preparing hierarchical carbon materials for a wide range of applications,but presents some fundamental insights for achieving higher absorption losses in EMI shielding materials.展开更多
Electromagnetic interference(EMI)shielding materials with excellent flexibility and mechanical properties and outstanding thermal conductivity have become a hot topic of research in functional composites.In this study...Electromagnetic interference(EMI)shielding materials with excellent flexibility and mechanical properties and outstanding thermal conductivity have become a hot topic of research in functional composites.In this study,the“sol-gel-film conversion technique”is used to assemble polyetherimidefunctionalized Ti_(3)C_(2)T_(x)nanosheets(f-Ti_(3)C_(2)T_(x))with poly(p-phenylene-2,6-benzobisoxazole)(PBO)nanofibers(PNFs),followed by dialysis and vacuum drying to prepare f-Ti_(3)C_(2)T_(x)/PNF films with lamellar structures.When the loading of f-Ti_(3)C_(2)T_(x)is 70 wt%,the f-Ti_(3)C_(2)T_(x)/PNF film presents optimal comprehensive properties,with an EMI shielding effectiveness(SE)of 35 dB and a specific SE/thickness((SSE,SE/density)/t)of 8211 dB cm^(2)/g,a tensile strength of 125.1 MPa,an in-plane thermal conductivity coefficient(λ)of 5.82 W/(m K),and electrical conductivity of 1943 S/m.After repeated folding for 10,000 cycles,the EMI SE and the tensile strength of f-Ti_(3)C_(2)T_(x)/PNFs films still remain 33.4 dB and 116.1 MPa,respectively.Additionally,the f-Ti_(3)C_(2)T_(x)/PNF film also shows excellent thermal stability,flame retardancy,and structural stability.This would provide a novel method for the design and fabrication of multifunctional composite films and considerably expand the applications of MXene-and PNF-based composites in the fields of EMI shielding and thermal management.展开更多
High-performance multifunctional polymeric materials integrated with high fire safety,excel-lent mechanical performances and electromagnetic interference(EMI)shielding properties have great prospects in practical appl...High-performance multifunctional polymeric materials integrated with high fire safety,excel-lent mechanical performances and electromagnetic interference(EMI)shielding properties have great prospects in practical applications.However,designing highly fire-safe and mechanically ro-bust EMI shielding nanocomposites remains a great challenge.Herein,hierarchical thermoplastic polyurethane/cyclophosphazene functionalized titanium carbide/carbon fiber fabric(TPU/CP-Ti_(3)C_(2)T_(x)/CF)nanocomposites with high fire safety and mechanical strength and toughness were prepared through the methods of melt blending,layer-by-layer stacking and thermocompression.The TPU/CP-Ti_(3)C_(2)T_(x)showed improved thermal stability.Moreover,the peak of heat release rate and total heat release of the hi-erarchical TPU sample containing 4.0 wt.%CP-Ti_(3)C_(2)T_(x)were respectively reduced by 64.4%and 31.8%relative to those of pure TPU,which were far higher than those of other TPU-based nanocomposites.The averaged EMI shielding effectiveness value of the hierarchical TPU/CP-Ti_(3)C_(2)T_(x)-2.0/CF nanocomposite reached 30.0 dB,which could satisfy the requirement for commercial applications.Furthermore,the ten-sile strength of TPU/CP-Ti_(3)C_(2)T_(x)-2.0/CF achieved 43.2 MPa,and the ductility and toughness increased by 28.4%and 84.3%respectively compared to those of TPU/CF.Interfacial hydrogen bonding in combination with catalytic carbonization of CP-Ti_(3)C_(2)T_(x)nanosheets and continuous conductive network of CF were re-sponsible for the superior fire safety,excellent EMI shielding and outstanding mechanical performances.This work offers a promising strategy to prepare multifunctional TPU-based nanocomposites,which have the potential for large-scale application in the fields of electronics,electrical equipment and 5 G facilities.展开更多
In this study,flexible and highly conductive composite rubber at low filler content was successfully prepared through polydopamine-assisted electroless silver plating plus mechanical mixing.Firstly,carbon fibers(CF)we...In this study,flexible and highly conductive composite rubber at low filler content was successfully prepared through polydopamine-assisted electroless silver plating plus mechanical mixing.Firstly,carbon fibers(CF)were activated by polydopamine(PDA)to improve the surface activity by self-polymerization reaction.Next,because of the metal chelating ability of PDA,silver layer was firmly deposited on the surface of CF through a facile electroless silver plating method.Finally,flexible silver-plated carbon fibers(Ag/pCF)silicone rubber composites prepared by mechanical mixing.By using X-ray photoelectron spectroscopy(XPS)and X-ray diffraction(XRD),the chemical composition and crystal structure of Ag/pCF were examined,and scanning electron microscopy(SEM)was used to assess the surface morphology of the Ag/pCF.The results showed that a uniform and dense silver layer was formed on the surface of the CF,and the conductivity of the Ag/pCF could reach 7885 S/cm.It was noteworthy that the composite rubber filled with only 45 phr Ag/pCF had a high electromagnetic interference shielding effectiveness(100 dB)due to the low density and high aspect ratio of Ag/pCF.The composite rubber has excellent potential for application in the field of electromagnetic interference shielding.展开更多
基金supported by the Natural Science Foundation of Anhui Province(No.2308085QE146 and 2208085ME116)the National Natural Science Foundation of China(No.52173039)+1 种基金the Natural Science Foundation of Jiangsu Province(No.BK20210894)the Anhui Provincial Universities Outstanding Youth Research Project(No.2023AH020018).
文摘Electromagnetic interference(EMI)shielding materials with superior shielding efficiency and low-reflection properties hold promising potential for utilization across electronic components,precision instruments,and fifth-generation communication equipment.In this study,multistage microcellular waterborne polyurethane(WPU)composites were constructed via gradient induction,layer-by-layer casting,and supercritical carbon dioxide foaming.The gradient-structured WPU/ironcobalt loaded reduced graphene oxide(FeCo@rGO)foam serves as an impedance-matched absorption layer,while the highly conductive WPU/silver loaded glass microspheres(Ag@GM)layer is employed as a reflection layer.Thanks to the incorporation of an asymmetric structure,as well as the introduction of gradient and porous configurations,the composite foam demonstrates excellent conductivity,outstanding EMI SE(74.9 dB),and minimal reflection characteristics(35.28%)in 8.2-12.4 GHz,implying that more than 99.99999%of electromagnetic(EM)waves were blocked and only 35.28%were reflected to the external environment.Interestingly,the reflectivity of the composite foam is reduced to 0.41%at 10.88 GHz due to the resonance for incident and reflected EM waves.Beyond that,the composite foam is characterized by low density(0.47 g/cm^(3))and great stability of EMI shielding properties.This work offers a viable approach for craft-ing lightweight,highly shielding,and minimally reflective EMI shielding composites.
基金support and funding from the National Natural Science Foundation of China(Nos.52303104,52203100 and 52403132)Young Talent Fund of Association for Science and Technology in Shaanxi,China(No.20240455)+4 种基金Basic Research Program of Natural Science of Shaanxi Province(No.2024JCYBMS-275)Natural Science Foundation of Chongqing,China(No.2023NSCQ-MSX2682)the Doctoral Research Start-up Funds of Xi’an University of Technology(No.108/451122007)Innovation Foundation for Doctor Dissertation of Northwestern Polytechnical University(No.CX2024094)the Transformation Projects of Scientific and Technological Achievements of Qinchuangyuan Platform(2023JH-QCYCK-0026).
文摘With the rapid development of 5G communication technology and wearable electronic devices,the demand for low-reflection electromagnetic interference(EMI)shielding materials is becoming increasingly urgent.In this work,reduced graphene oxide-MXene(rGMH)@FeNi/epoxy EMI shielding composites with a regular honeycomb structure were successfully prepared by the combination of surface functionalization modification,sacrificial template,and freeze-drying.The effects of magnetic FeNi alloy particle loading mode and loading amount on the EMI shielding performance of composites were investigated.The results show that rGMH@FeNi/epoxy EMI shielding composites have the highest EMI shielding effectiveness(EMI SE)and the lowest reflection shielding effectiveness when magnetic FeNi alloy particles are loaded only on the graphene skeleton.In this composite,the EMI SE value of the composite is 61 dB when the rGMH@FeNi mass fraction is 5.4 wt%(f-FeNi mass fraction is 0.9 wt%),which is 4.7 times that of the blended rGO/MXene/FeNi/epoxy resin composite(13 dB)with the same mass fraction.At the same time,the rGMH@FeNi/epoxy composite has excellent thermal stability(heat-resistance index of 190.3℃)and mechanical properties(energy storage modulus of 8606.7 MPa).These polymer-based EMI shielding composites with excellent EMI shielding properties and low reflection effectiveness have great potential in the protection of high-power,portable and wearable electronic devices against electromagnetic pollution.
基金the National Natural Science Foundation of China(52090034,52273064,52221006)the Fundamental Research Funds for the Central Universities(JD2417)is gratefully acknowledged.
文摘Although multifunctional electromagnetic interference(EMI)shielding materials with ultrahigh electromagnetic wave absorption are highly required to solve increasingly serious electromagnetic radiation and pollution and meet multi-scenario applications,EMI shielding materials usually cause a lot of reflection and have a single function.To realize the broadband absorption-dominated EMI shielding via absorption-reflection-reabsorption mechanisms and the interference cancelation effect,multifunctional asymmetric bilayer aerogels are designed by sequential printing of a MXene-graphene oxide(MG)layer with a MG emulsion ink and a conductive MXene layer with a MXene ink and subsequent freeze-drying for generating and solidifying numerous pores in the aerogels.The top MG layer of the asymmetric bilayer aerogel optimizes impedance matching and achieves re-absorption,while the bottom MXene layer enhances the reflection of the incident electromagnetic waves.As a result,the asymmetric bilayer aerogel achieves an average absorption coefficient of 0.95 in the X-band and shows the tunable absorption ability to electromagnetic wave in the ultrawide band from 8.2 to 40 GHz.Finite element simulations substantiate the effectiveness of the asymmetric bilayer aerogel for electromagnetic wave absorption.The multifunctional bilayer aerogels exhibit hydrophobicity,thermal insulation and Joule heating capacities and are efficient in solar-thermal/electric heating,infrared stealth,and clean-up of spilled oil.
文摘In this paper,a sparse graph neural network-aided(SGNN-aided)decoder is proposed for improving the decoding performance of polar codes under bursty interference.Firstly,a sparse factor graph is constructed using the encoding characteristic to achieve high-throughput polar decoding.To further improve the decoding performance,a residual gated bipartite graph neural network is designed for updating embedding vectors of heterogeneous nodes based on a bidirectional message passing neural network.This framework exploits gated recurrent units and residual blocks to address the gradient disappearance in deep graph recurrent neural networks.Finally,predictions are generated by feeding the embedding vectors into a readout module.Simulation results show that the proposed decoder is more robust than the existing ones in the presence of bursty interference and exhibits high universality.
基金supported by the Defitech Foundation(Morges,CH)to FCHthe Bertarelli Foundation-Catalyst program(Gstaad,CH)to FCH+2 种基金the Wyss Center for Bio and Neuroengineering the Lighthouse Partnership for AI-guided Neuromodulation to FCHthe Fonds de recherche du Quebec-Sante(FRQS#342969)to CEPthe Neuro X Postdoctoral Fellowship Program to CEP。
文摘Brain lesions,such as those caused by stroke or traumatic brain injury(TBI),frequently result in persistent motor and cognitive impairments that significantly affect the individual patient's quality of life.Despite differences in the mechanisms of injury,both conditions share a high prevalence of motor and cognitive impairments.These deficits show only limited natural recovery.
基金supported by the National Natural Science Foundation of China, No. 30960399, 81160181
文摘To investigate the effects of mRNA interference on aquaporin-4 expression in swollen tissue of rats with ischemic cerebral edema, and diagnose the significance of diffusion-weighted MRI, we injected 5 pL shRNA- aquaporin-4 （control group） or siRNA- aquaporin-4 solution （1：800） （RNA interference group） into the rat right basal ganglia immediately before occlusion of the middle cerebral artery. At 0.25 hours after occlusion of the middle cerebral artery, diffusion-weighted MRI displayed a high signal; within 2 hours, the relative apparent diffusion coefficient decreased markedly, aquaporin-4 expression increased rapidly, and intracellular edema was obviously aggravated; at 4 and 6 hours, the relative apparent diffusion coefficient slowly returned to control levels, aquaporin-4 expression slightly increased, and angioedema was observed. In the RNA interference group, during 0.25- 6 hours after injection of siRNA- aquaporin-4 solution, the relative apparent diffusion coefficient slightly fluctuated and aquaporin-4 expression was upregulated; during 0.5 4 hours, the relative apparent diffusion coefficient was significantly higher, while aquaporin-4 expression was significantly lower when compared with the control group, and intracellular edema was markedly reduced; at 0.25 and 6 hours, the relative apparent diffusion coefficient and aquaporin-4 expression were similar when compared with the control group; obvious angioedema remained at 6 hours. Pearson＇s correlation test results showed that aquaporin-4 expression was negatively correlated with the apparent diffusion coefficient （r = -0.806, P 〈 0.01）. These findings suggest that upregulated aquaporin-4 expression is likely to be the main molecular mechanism of intracellular edema and may be the molecular basis for decreased relative apparent diffusion coefficient. Aquaporin-4 gene interference can effectively inhibit the upregulation of aquaporin-4 expression during the stage of intracelfular edema with time-effectiveness. Moreover, diffusion-weighted MRI can accurately detect intracellular edema.
基金financially supported by the National Natural Science Foundation of China(Nos.51421061,51120135002 and 51473102)the Innovation Team Program of Science and Technology Department of Sichuan Province(No.2014TD0002)the China Postdoctoral Science Foundation(Nos.2015M572474 and 2016T90848)
文摘An electromagnetic interference （EMI） shielding composite based on ultrahigh molecular weight polyethylene （UHMWPE） loaded with economical graphite-carbon black （CB） hybrid fillers was prepared via a green and facile methodology, i.e., high-speed mechanical mixing combined with hot compression thus avoiding the assistance of the intensive ultrasound dispersion in volatile organic solvents. In this composite, the graphite-CB hybrid fillers were selectively distributed in the interfacial regions of UHMWPE domains resulting a typical segregated structure. Thanks to the specific morphology of segregated conductive networks along with the synergetic effect of large-sized graphite flakes and small-sized CB nanoparticles, a low filler loading of 7.7 vol% （15 wt%） yielded the graphite-CB/UHMWPE composites with a satisfactory electrical conductivity of 33.9 S/m and a superior shielding effectiveness of 40.2 dB, manifesting the comparable value of the pricey large-aspect-ratio carbon nanofillers （e.g., carbon nanotubes and graphene nanosheets） based polymer composites. More interestingly, with the addition of 15 wt% graphite-CB （1/3, W/W） hybrid fillers, the tensile strength and elongation at break of the composite reached 25.3 MPa and 126%, respectively; with a remarkable increase of 58.1% and 2420% over the conventional segregated graphite/UHMWPE composites. The mechanical reinforcement could be attributed to the favor of the small-sized CB particles in the polymer molecular diffusion between UHMWPE domains which in tuna provided a stronger interfacial adhesion. This work provides a facile, green and affordable strategy to obtain the polymer composites with high electrical conductivity, efficient EMI shielding, and balanced mechanical performance.
基金supported by China Scholarship Council (201406960042)the National Science Foundation (91338115,61231008)+2 种基金National S&T Major Project (2015ZX03002006)Program for Changjiang Scholars and Innovative Research Team in University (IRT0852)the 111 Project (B08038)
文摘In this paper, we exploit clustered interference alignment(IA) for efficient subchannel allocation in ultra-dense orthogonal frequency division multiplexing access(OFDMA) based femtocell networks, which notably improves the spectral efficiency as well as addresses the feasibility issue of IA. Our problem is formulated as a combinatorial optimization problem which is NP-hard. To avoid obtaining its optimal solution by exhaustive search, we propose a two-phases efficient solution with low-complexity. The first phase groups all the femtocell user equipments(FUEs) into disjoint clusters, and the second phase allocates subchannels to the formed clusters where IA is performed. By doing this, the intra-cluster and inter-cluster interferences are mitigated by clustered IA and subchannel allocation in ultra-dense femtocell networks, respectively.Also, low-complexity algorithm is proposed to solve the corresponding sub-problem in each phase. Simulation results demonstrate that the proposed scheme not only outperforms other related schemes, but also provides a close performance to the optimal solution.
基金supports from the National Natural Science Foundation of China(U21A2093 and 51903145)Natural Science Basic Research Plan for Distinguished Young Scholars in Shaanxi Province of China(2019JC-11)and Fundamental Research Funds for the Central Universities(D5000210627)This work is also financially supported by Polymer Electromagnetic Functional Materials Innovation Team of Shaanxi Sanqin Scholars.
文摘With the rapid development of fifth-generation mobile com-munication technology and wearable electronic devices,electromagnetic interference and radiation pollution caused by electromagnetic waves have attracted worldwide attention.Therefore,the design and development of highly efficient EMI shielding materials are of great importance.In this work,the three-dimensional graphene oxide(GO)with regular honeycomb structure(GH)is firstly constructed by sacrificial template and freeze-dry-ing methods.Then,the amino functionalized FeNi alloy particles(f-FeNi)are loaded on the GH skeleton followed by in-situ reduction to prepare rGH@FeNi aerogel.Finally,the rGH@FeNi/epoxy EMI shielding com-posites with regular honeycomb structure is obtained by vacuum-assisted impregnation of epoxy resin.Benefitting from the construction of regular honeycomb structure and electromagnetic synergistic effect,the rGH@FeNi/epoxy composites with a low rGH@FeNi mass fraction of 2.1 wt%(rGH and f-FeNi are 1.2 and 0.9 wt%,respectively)exhibit a high EMI shielding effectiveness(EMI SE)of 46 dB,which is 5.8 times of that(8 dB)for rGO/FeNi/epoxy composites with the same rGO/FeNi mass fraction.At the same time,the rGH@FeNi/epoxy composites also possess excellent thermal stability(heat-resistance index and temperature at the maximum decomposition rate are 179.1 and 389.0°C respectively)and mechanical properties(storage modulus is 8296.2 MPa).
基金supported by National Natural Science Foundation of China(Grant No.51175376)
文摘Current researches have not yet found the effect law of the cutter parameters and machining parameters on the interference in gear slicing,the interference between the cutter and machined gear often happens because the appropriate cutter parameters and machining parameters cannot be set,which reduces the gear machining accuracy.The relative position between the major flank face and edge-sweeping surface,distribution law of the interference area in forming process of edge-sweeping surface,and effect law of relative positions among edge-sweeping surfaces on the interference are studied by graphical analysis.The effect law of the cutter parameters and machining parameters on the interference is found.The effect law shows that the interference in gear slicing can be controlled when the relief angle measured on the top edge and feed of every rotation are chosen respectively larger than 9~and smaller than 0.15 mrn/r.An internal helical gear is sliced with the spur slice cutter and the cutter parameters and machining parameters are set based on above the effect law.The machined gear is measured in Gear Measuring Center and the detection result shows that the comprehensive accuracy reaches GB/T Class 7,where some reach GB/T Class 6.The result can meet the gear machining accuracy requirement and shows that the effect law found is valid.The problem of the interference in gear slicing is solved and the gear machining accuracy can be improved.
基金Financial support from the National Natural Science Foundation of China(51922020,52090034)the Fundamental Research Funds for the Central Universities(BHYC1707B,XK1802-2)。
文摘Although electrically conductive and hydrophilic MXene sheets are promising for multifunctional fibers and electronic textiles,it is still a challenge to simultaneously enhance both conductivity and mechanical properties of MXene fibers because of the high rigidity of MXene sheets and insufficient inter-sheet interactions.Herein,we demonstrate a core-shell wet-spinning methodology for fabricating highly conductive,super-tough,ultra-strong,and environmentally stable Ti_(3)C_(2)T_(x) MXene-based core-shell fibers with conductive MXene cores and tough aramid nanofiber(ANF)shells.The highly orientated and low-defect structure endows the ANF@MXene core-shell fiber with supertoughness of~48.1 MJ m^(-3),high strength of~502.9 MPa,and high conductivity of~3.0×10^(5)S m^(-1).The super-tough and conductive ANF@MXene fibers can be woven into textiles,exhibiting an excellent electromagnetic interference(EMI)shielding efficiency of 83.4 dB at a small thickness of 213μm.Importantly,the protection of the ANF shells provides the fibers with satisfactory cyclic stability under dynamic stretching and bending,and excellent resistance to acid,alkali,seawater,cryogenic and high temperatures,and fire.The oxidation resistance of the fibers is demonstrated by their wellmaintained EMI shielding performances.The multifunctional core-shell fibers would be highly promising in the fields of EMI shielding textiles,wearable electronics and aerospace.
基金This work was supported by the National Natural Science Foundation of China(No.U21A2093)the Anhui Provincial Natural Science Foundation(No.2308085QE146)the National Natural Science Foundation of Jiangsu Province(No.BK20210894).
文摘The utilization of eco-friendly,lightweight,high-efficiency and high-absorbing electromagnetic interference(EMI)shielding composites is imperative in light of the worldwide promotion of sustainable manufacturing.In this work,magnetic poly(butyleneadipate-coterephthalate)(PBAT)microspheres were firstly synthesized via phase separation method,then PBAT composite foams with layered structure was constructed through the supercritical carbon dioxide foaming and scraping techniques.The merits of integrating ferroferric oxideloaded multi-walled carbon nanotubes(Fe3O4@MWCNTs)nanoparticles,a microcellular framework,and a highly conductive silver layer have been judiciously orchestrated within this distinctive layered configuration.Microwaves are consumed throughout the process of“absorption-reflection-reabsorption”as much as possible,which greatly declines the secondary radiation pollution.The biodegradable PBAT composite foams achieved an EMI shielding effectiveness of up to 68 dB and an absorptivity of 77%,and authenticated favorable stabilization after the tape adhesion experiment.
文摘In order to investigate the influence of silencing soluble epoxide hydrolase（sEH） with double-stranded small interfering RNA（siRNA） on cardiomyocytes apoptosis induced by doxorubicin（DOX）,two plasmids containing siRNA sequences specific to sEH were constructed and transfected into the primary cultured cardiomyocytes by using FuGENE HD transfection agents.The mRNA and protein expression levels of sEH were detected by semiquantitative RT-PCR and Western blotting respectively,and the plasmids that silenced sEH most significantly were selected,and renamed EH-R.The plasmids carrying a nonspecific siRNA coding sequence（PCN） served as the negative control.Cardiomyocytes were divided into four groups：control group,DOX group,PCN＋DOX group,and EH-R＋DOX group.Apoptosis of cardiomyocytes was induced by DOX at a concentration of 1 μmol/L.Apoptosis rate of cardiomyocytes was determined by flow cytometery.The protein expression levels of Bcl-2 and Bax were detected by Western blotting.The results showed that the expression of sEH was down-regulated by EH-R plasmid.The expression levels of sEH mRNA and protein in the EH-R＋DOX group were significantly decreased as compared with other groups（P0.01）.As compared with the control group,the apoptosis rate of cardiomyocytes in three DOX-treated groups was obviously increased,the expression levels of Bax increased,and those of Bcl-2 decreased（P0.01）.However,the expression levels of Bax were decreased,those of Bcl-2 increased and the apoptosis rate of cardiomyocytes obvi-ously decreased in EH-R＋DOX group when compared with those in the DOX group and the PCN＋DOX group（P0.01 for each）.It was concluded that the recombinant plasmids could be successfully constructed,and transfected into the primary cultured cardiomyocytes.They could ameliorate the DOX-induced cardiomyocytes apoptosis by selectively inhibiting the expression of sEH with RNAi and increasing the expression of Bcl-2.
基金supported by the National Natural Science Foundation of China(Nos.51773167,52102303,52103095)the China Postdoctoral Science Foundation(No.2019M650268)+1 种基金the Opening Project of State Key Laboratory of Polymer Materials Engineering(Sichuan University)(No.sklpme2021-05-09)Foundation of Education Department of Shaanxi Province(No.20JK0805)。
文摘Flexible, lightweight, robust and versatile properties are essential for the next generation of wearable as well as intelligent electromagnetic interference(EMI) shielding materials. In this work, multilayered films containing cellulose nanofiber(CNF) layers, CNF/MXene layers, and CNF/silver nanowires(CNF/Ag NWs)layers were fabricated by an efficient and easy-to-use vacuum filtration method. Compared with a uniformly mixed film, the resultant layered composite films that loaded with a low MXene and AgNWs content exhibit superior mechanical properties with a tensile strength of 137 MPa, a strain at break of 5.7%, excellent EMI shielding effectiveness(EMI SE) of 61.9 d B, and higher EMI SE/t of 20,653 d B cm^(-1).This is attributed to the high-performance CNF substrate, the highly efficient layered structures, and extensive hydrogen-bonding interactions. In particular, a high degree of ohmic loss of multiple interfaces and polarization relaxation of local defects, as well as an abundance of terminal groups, favor the loss of electromagnetic waves(EMW) within the material. In addition, the prepared multifunctional layered composite films also show good antibacterial properties. As a result, the obtained new kind of flexible layered structure EMI shielding composite films with excellent EMI shielding performance, and mechanical properties present promising application prospects in the fields of EMI shielding and protection for aerospace, portable, and wearable flexible electronic devices.
基金financially supported by the National Natural Science Foundation of China(No.21909230)the Postdoctoral Science Foundation of Shaanxi Province(No.2018BSHEDZZ208)+1 种基金the Project funded by China Postdoctoral Science Foundation(No.2017M623235)the Analytical&Testing Center of Northwestern Polytechnical University for SEM and TEM characterizations and the Open Teat Foundation(No.2020T022)。
文摘Integrating smart functions into one flexible electronic is vastly valuable in improving their working performances and broadening applications.Here,this work reports a ultraflexible,highly efficient electromagnetic interference(EMI)shielding,and self-healable triboelectric nanogenerator(TENG)that is assembled by modified Ti_(3)C_(2)T_(x) MXene(m-MXene)-based nanocomposite elastomers.Benefitting from the excellent electronegativity of m-MXene,the single-electrode mode-based TENG can generate high open-circuit voltage(V_(oc))oscillating between-65 and 245 V,high short-circuit current(I_(sc))of 29 μA,and an instantaneously maximum peak power density of 1150 mW m^(-2) that can power twenty light-emitting diodes(LEDs).Moreover,the resultant TENG possesses outstanding EMI shielding performance with the maximum shielding effectiveness of 48.1 dB in the X-band.The enhanced shielding capability is dominated by the electromagnetic absorption owning to high conduction loss in m-MXene network,multiple reflections between m-MXene sheets,and polarization effect on the surface of m-MXene sheets.Additionally,a self-powered wearable sensor is fabricated based on the as-prepared TENG.The sensor shows an intrinsic healing ability with healing efficiency of 98.2% and can accurately detect the human large-scale motions and delicate physical signal.This work provides an enhanced way to fabricate the wearable electronics integrated with smart functions,and the reported MXene-based TENG may have a broad prospect in the fields of aerospace,artificial intelligence,and healthcare systems.
基金financial supports of this work by National Natural Science Foundation of China(51821091,51872234)Natural Science Basic Research Plan in Shaanxi(No.2020JQ-154)。
文摘Lightweight,flexible,ultrahigh-performance electromagnetic-interfe rence(EMI)shielding materials are urgently required in the areas of aircraft/aerospace,portable and wearable electronics.Herein,1 D carbon nanotubes(CNT)and carbon nanofibers(CNF)with 2 D edge-rich graphene(ERG)are used to form a lightweight,flexible CNT-ERG-CNF hybrid foam.This foam was fabricated through a self-sacrificial templating chemical vapor deposition process,where nanocarbons bond through covalent bonding,forming a hierarchical 3 D hybridized carbon nanostructure.Multistage conductive networks and heterogeneous interfaces were constructed using edge-rich nanocarbons to increase the induced currents and interfacial polarization which makes great contributions to achieve high absorption electromagnetic shielding effectiveness(SEA).The CNT-ERG-CNF hybrid foam exhibits EMI shielding effectiveness(SE)exceeding55.4 dB in the X-band while the specific SE(SSE,SE divided by mass density)achieves 9200 dB cm^(3)g^(-1),which surpasses that of nearly all other carbon-based composite materials.Furthermore,the structural stability and durability of the flexible CNT-ERG-CNF hybrid foams is examined by measuring EMI SE after 10000 times cyclic bending.Remarkably,this work not only provides a new idea for preparing hierarchical carbon materials for a wide range of applications,but presents some fundamental insights for achieving higher absorption losses in EMI shielding materials.
基金The authors are grateful for the support of and funding from the Foundation of National Natural Science Foundation of China(51903145 and 51973173)the Natural Science Basic Research Plan for Distinguished Young Scholars in Shaanxi Province of China(2019JC-11)+1 种基金Fundamental Research Funds for the Central Universities(D5000210627)L.Wang is grateful to the Innovation Foundation for Doctor Dissertation of Northwestern Polytechnical University(CX202053).
文摘Electromagnetic interference(EMI)shielding materials with excellent flexibility and mechanical properties and outstanding thermal conductivity have become a hot topic of research in functional composites.In this study,the“sol-gel-film conversion technique”is used to assemble polyetherimidefunctionalized Ti_(3)C_(2)T_(x)nanosheets(f-Ti_(3)C_(2)T_(x))with poly(p-phenylene-2,6-benzobisoxazole)(PBO)nanofibers(PNFs),followed by dialysis and vacuum drying to prepare f-Ti_(3)C_(2)T_(x)/PNF films with lamellar structures.When the loading of f-Ti_(3)C_(2)T_(x)is 70 wt%,the f-Ti_(3)C_(2)T_(x)/PNF film presents optimal comprehensive properties,with an EMI shielding effectiveness(SE)of 35 dB and a specific SE/thickness((SSE,SE/density)/t)of 8211 dB cm^(2)/g,a tensile strength of 125.1 MPa,an in-plane thermal conductivity coefficient(λ)of 5.82 W/(m K),and electrical conductivity of 1943 S/m.After repeated folding for 10,000 cycles,the EMI SE and the tensile strength of f-Ti_(3)C_(2)T_(x)/PNFs films still remain 33.4 dB and 116.1 MPa,respectively.Additionally,the f-Ti_(3)C_(2)T_(x)/PNF film also shows excellent thermal stability,flame retardancy,and structural stability.This would provide a novel method for the design and fabrication of multifunctional composite films and considerably expand the applications of MXene-and PNF-based composites in the fields of EMI shielding and thermal management.
基金This work was financially supported by the National Natural Science Foundation of China(No.52173070)the Opening Test-ing Funds for the Valuable Equipments of Fuzhou University(No.2023T013).
文摘High-performance multifunctional polymeric materials integrated with high fire safety,excel-lent mechanical performances and electromagnetic interference(EMI)shielding properties have great prospects in practical applications.However,designing highly fire-safe and mechanically ro-bust EMI shielding nanocomposites remains a great challenge.Herein,hierarchical thermoplastic polyurethane/cyclophosphazene functionalized titanium carbide/carbon fiber fabric(TPU/CP-Ti_(3)C_(2)T_(x)/CF)nanocomposites with high fire safety and mechanical strength and toughness were prepared through the methods of melt blending,layer-by-layer stacking and thermocompression.The TPU/CP-Ti_(3)C_(2)T_(x)showed improved thermal stability.Moreover,the peak of heat release rate and total heat release of the hi-erarchical TPU sample containing 4.0 wt.%CP-Ti_(3)C_(2)T_(x)were respectively reduced by 64.4%and 31.8%relative to those of pure TPU,which were far higher than those of other TPU-based nanocomposites.The averaged EMI shielding effectiveness value of the hierarchical TPU/CP-Ti_(3)C_(2)T_(x)-2.0/CF nanocomposite reached 30.0 dB,which could satisfy the requirement for commercial applications.Furthermore,the ten-sile strength of TPU/CP-Ti_(3)C_(2)T_(x)-2.0/CF achieved 43.2 MPa,and the ductility and toughness increased by 28.4%and 84.3%respectively compared to those of TPU/CF.Interfacial hydrogen bonding in combination with catalytic carbonization of CP-Ti_(3)C_(2)T_(x)nanosheets and continuous conductive network of CF were re-sponsible for the superior fire safety,excellent EMI shielding and outstanding mechanical performances.This work offers a promising strategy to prepare multifunctional TPU-based nanocomposites,which have the potential for large-scale application in the fields of electronics,electrical equipment and 5 G facilities.
基金supported by the National Natural Science Foundation of China(No.51833002).
文摘In this study,flexible and highly conductive composite rubber at low filler content was successfully prepared through polydopamine-assisted electroless silver plating plus mechanical mixing.Firstly,carbon fibers(CF)were activated by polydopamine(PDA)to improve the surface activity by self-polymerization reaction.Next,because of the metal chelating ability of PDA,silver layer was firmly deposited on the surface of CF through a facile electroless silver plating method.Finally,flexible silver-plated carbon fibers(Ag/pCF)silicone rubber composites prepared by mechanical mixing.By using X-ray photoelectron spectroscopy(XPS)and X-ray diffraction(XRD),the chemical composition and crystal structure of Ag/pCF were examined,and scanning electron microscopy(SEM)was used to assess the surface morphology of the Ag/pCF.The results showed that a uniform and dense silver layer was formed on the surface of the CF,and the conductivity of the Ag/pCF could reach 7885 S/cm.It was noteworthy that the composite rubber filled with only 45 phr Ag/pCF had a high electromagnetic interference shielding effectiveness(100 dB)due to the low density and high aspect ratio of Ag/pCF.The composite rubber has excellent potential for application in the field of electromagnetic interference shielding.
