The seismic data of the Laoshan Uplift in the South Yellow Sea Basin reveal a low signal-tonoise ratio and low refl ection signal energy in the deep Mesozoic–Paleozoic strata.The main reason is that the Mesozoic-Pale...The seismic data of the Laoshan Uplift in the South Yellow Sea Basin reveal a low signal-tonoise ratio and low refl ection signal energy in the deep Mesozoic–Paleozoic strata.The main reason is that the Mesozoic-Paleozoic marine carbonate rock strata are directly covered by the Cenozoic terrestrial clastic rock strata,which form a strong shielding layer.To obtain the reflection signals of the strata below the strong shielding layer,a one-way wave equation bidirectional illumination analysis of the main observation system parameters was conducted by analyzing the mechanism of the strong shielding layer.Low-frequency seismic sources are assumed to have a high illumination intensity on the reflection layer below the strong shielding layer.Accordingly,optimized acquisition parameter suggestions were proposed,and reacquisition was performed at the existing survey line locations in the Laoshan Uplift area.The imaging of the newly acquired data in the middle and deep layers was drastically improved.It revealed the unconformity between the Sinian and Cambrian under the strong shielding layer.The study yielded new insights into the tectonic and sedimentary evolution of the Lower Paleozoic in the South Yellow Sea.展开更多
The investigation of absorption-led shielding mechanisms has now made practical progress as a result of the concept of green EM shielding.The extant studies primarily concentrate on the introduction of mag-netic parti...The investigation of absorption-led shielding mechanisms has now made practical progress as a result of the concept of green EM shielding.The extant studies primarily concentrate on the introduction of mag-netic particles into the system,with the objective of enhancing the absorption rate(A)through dielectric-magnetic modulation for absorption-led electromagnetic shielding.In contrast,this paper presents a novel approach whereby PVA,glycerol,and MXene are combined into an organohydrogel(PMG)with oriented pores.This results in the creation of a non-magnetic medium that exhibits high absorption loss in mul-tiple bands,thereby establishing a novel shielding system.The PMG20-3 organohydrogel(0.78 wt%MX-ene)has a shielding performance in the X-band of 42.34 dB(A/R=1).In the terahertz band,the organic hydrogel gel exhibits an absorption rate of 99.9%,a performance that exceeds that of the majority of previously reported systems.The PMG gel displays remarkable flexibility and strength,with a hysteresis return line that remains stable under 1000 compression cycles.Additionally,it offers versatile sensing capabilities and infrared stealth.The findings of this study offer novel insights that may facilitate the accelerated utilization of innovative multifunctional and environmentally conscious electromagnetic in-terference(EMI)shielding materials.展开更多
The development of materials with excellent microwave absorption(MWA)and electromagnetic interference(EMI)shielding performances has currently received attention.Herein,mesophase pitch-based carbon foam(MPCF)with 3D i...The development of materials with excellent microwave absorption(MWA)and electromagnetic interference(EMI)shielding performances has currently received attention.Herein,mesophase pitch-based carbon foam(MPCF)with 3D interconnected pore structure was prepared through the high pressure pyrolysis of mesophase coal tar pitch.It is found that the 3D interconnected cellular pores of MPCF facilitate multiple reflections of electromagnetic waves,which results in the minimum reflection loss(RLmin)value of MPCF reaches-37.84 dB with the effective absorption bandwidth(EAB)of 5.44 GHz at a thickness of 2.70 mm,and the total average electromagnetic shielding effectiveness(SE_(T))under 3.00 mm thickness achieves 26.52 dB in X-band.Subsequently,MPCF is activated by KOH to obtain activated carbon foam(A-MPCF).The average SE_(T)of A-MPCF achieves 103.00 dB for abundant nanopores on the pore cell walls,which leads to a transition from the multiple reflections of electromagnetic waves on the walls to diffuse reflection.Unfortunately,the reflection coefficient(R)of A-MPCF increases from 0.78 to 0.90.To reduce the R value,Fe_(3)O_(4)/A-MPCF was fabricated via the in situ growth of nano Fe_(3)O_(4)on A-MPCF.Consequently,the R value of Fe_(3)O_(4)/A-MPCF was reduced from 0.90 to 0.74,whereas the MWA performance was only slightly decreased.This work proposes a simple strategy for simultaneously adjusting MWA and EMI shielding performances of materials.展开更多
Biochar and biochar composites are versatile materials that can be used in many applications.In this study,biochar was prepared from sawdust and combined with the yttrium iron garnet(YIG)nanocrystal to investigate the...Biochar and biochar composites are versatile materials that can be used in many applications.In this study,biochar was prepared from sawdust and combined with the yttrium iron garnet(YIG)nanocrystal to investigate the shielding effectiveness of the composite structure.Firstly,the effect of the pyrolysis temperature on the shielding effectiveness of biochar was investigated.Secondly,biochars combined with YIG nanocrystals with different contents and shielding effectiveness of the composites were investigated.The electromagnetic effectiveness of the samples was investigated within the X band(8-12 GHz).The findings indicate that biochar demonstrates enhanced absorption properties with elevated pyrolysis temperatures.Biochars demonstrated an approximate 40 d B shielding effectiveness,while YIG exhibited approximately 7 d B,corresponding to absorption at 8 GHz.However,the combination of biochar and YIG exhibited exceptional absorption,reaching 67.12 d B at 8 GHz.展开更多
In a rapid cycling synchrotron(RCS),the magnetic field is synchronized with the beam energy,creating a highly dynamic magnetic environment.A ceramic chamber with a shielding layer(RF shield),composed of a series of co...In a rapid cycling synchrotron(RCS),the magnetic field is synchronized with the beam energy,creating a highly dynamic magnetic environment.A ceramic chamber with a shielding layer(RF shield),composed of a series of copper strips connected to a capacitor at either end,is typically employed as a vacuum chamber to mitigate eddy current effects and beam coupling impedance.Consequently,the ceramic chamber exhibits a thin-walled multilayered complex structure.Previous theoretical studies have suggested that the impedance of such a structure has a negligible impact on the beam.However,recent impedance measurements of the ceramic chamber in the China Spallation Neutron Source(CSNS)RCS revealed a resonance in the low-frequency range,which was confirmed by further theoretical analysis as a source of beam instability in the RCS.Currently,the magnitude of this impedance cannot be accurately assessed using theoretical calculations.In this study,we used the CST Microwave Studio to confirm the impedance of the ceramic chamber.Further simulations covering six different types of ceramic chambers were conducted to develop an impedance model in the RCS.Additionally,this study investigates the resonant characteristics of the ceramic chamber impedance,finding that the resonant frequency is closely related to the capacitance of the capacitors.This finding provides clear directions for further impedance optimization and is crucial for achieving a beam power of 500 kW for the CSNS Phase-Ⅱ project(CSNS-Ⅱ).However,careful attention must be paid to the voltage across the capacitors.展开更多
The thrust hydraulic system of the prototype shield machine with pressure and flow compound control scheme was introduced. The experimental system integrated with proportional valves for study was designed. Dynamics m...The thrust hydraulic system of the prototype shield machine with pressure and flow compound control scheme was introduced. The experimental system integrated with proportional valves for study was designed. Dynamics modeling of multi-cylinder thrust system and synchronous control design were accomplished. The simulation of the synchronization motion control system was completed in AMESim and Matlab/Simulink software environments. The experiment was conducted by means of master/slave PID with dead band compensating flow and conventional PID regulating pressure. The experimental results show that the proposed thrust hydraulic system and its control strategy can meet the requirements of tunneling in motion and posture control for the shield machine, keeping the non-synchronous error within ±3 mm.展开更多
An estimation approach using least squares method was presented for identificationof model parameters of pressure control in shield tunneling.The state equation ofthe pressure control system for shield tunneling was a...An estimation approach using least squares method was presented for identificationof model parameters of pressure control in shield tunneling.The state equation ofthe pressure control system for shield tunneling was analytically derived based on themass equilibrium principle that the entry mass of the pressure chamber from cutting headwas equal to excluding mass from the screw conveyor.The randomly observed noise wasnumerically simulated and mixed to simulated observation values of system responses.The numerical simulation shows that the state equation of the pressure control system forshield tunneling is reasonable and the proposed estimation approach is effective even ifthe random observation noise exists.The robustness of the controlling procedure is validatedby numerical simulation results.展开更多
The development of the preparation strategy for high-quality and large-size graphene via eco-friendly routes is still a challenging issue.Herein,we have successfully developed a novel route to chemically exfoliate nat...The development of the preparation strategy for high-quality and large-size graphene via eco-friendly routes is still a challenging issue.Herein,we have successfully developed a novel route to chemically exfoliate natural graphite into high-quality and large-size graphene in a binary-peroxidant system.This system is composed of urea peroxide(CO(NH_(2))_(2)·H_(2)O_(2))and hydrogen peroxide(H_(2)O_(2)),where CO(NH_(2))_(2)·H_(2)O_(2)is used in preparing graphene for the first time.Benefiting from the complete decomposition of CO(NH_(2))_(2)·H_(2)O_(2)and H_(2)O_(2)into gaseous species under microwave(MW)irradiation,no water-washing and effluent-treatment are needed in this chemical exfoliation procedure,thus the preparation of graphene in an eco-friendly way is realized.The resultant graphene behaves a large-size,high-quality and few-layer feature with a yield of~100%.Then 4µm-thick ultrathin graphene paper fabricated from the as-exfoliated graphene is used as an electromagnetic interference(EMI)shielding material.And its absolute effectiveness of EMI shielding(SSE/t)is up to 34,176.9 dB cm^(2)/g,which is,to the best of our knowledge,among the highest values so far reported for typical EMI shielding materials.The EMI shielding performance demonstrates a great application potential of graphene paper in meeting the ever-increasingly EMI shielding demands in miniaturized electronic devices.展开更多
For the purpose of increasing the in vivo stability of polycation gene carriers, we prepared a kind of p H-sensitive poly（ethylene glycol）-poly（γ-benzyl-L-glutamate-co-glutamic acid）（PEG-PGA（65）, 65 denotes th...For the purpose of increasing the in vivo stability of polycation gene carriers, we prepared a kind of p H-sensitive poly（ethylene glycol）-poly（γ-benzyl-L-glutamate-co-glutamic acid）（PEG-PGA（65）, 65 denotes the molar ratio of glutamic acid in poly（γ-benzyl-L-glutamate-co-glutamic acid））. PEG-PGA（65） showed low cytotoxicity and could shield the positive charge of DNA/PEI（1：1） polyplexes efficiently. The transfection was enhanced due to the partially charge shielding in He La cell line at pH of 7.4. There was almost no transfection efficiency when the surface charge of the ternary particles turned to negative at p H of 7.4. However, the transfection efficiency recovered a lot by culturing at p H of 6.0 at the beginning of transfection. Confocal microscopic observation and flow cytometry results showed DNA/PEI polyplexes should be efficiently released and endocytosized at p H 6.0, because of the p H triggered deshielding action of PEG-PGA（65）. Due to the good biocompatibility and suitable p H triggered shielding/deshielding property, PEG-PGA（65） could be a potential shielding system for polycationic gene carriers used in vivo.展开更多
The relatively fragile low-temperature stability of cryogen-free superconducting magnetic resonance imaging(MRI)magnets requires the careful management of exogenous heat sources.A strongly shielded gradient magnetic f...The relatively fragile low-temperature stability of cryogen-free superconducting magnetic resonance imaging(MRI)magnets requires the careful management of exogenous heat sources.A strongly shielded gradient magnetic field is important for the optimal operation of cryogen-free MRI systems.In this study,we present an enhanced shielding method incorporating a regionalized stray field constraining strategy.By optimizing the constraint parameters,we could develop engineering-feasible gradient coil schemes without increasing system complexity but with the stray field intensity reduced by half.In real measurement in an integrated MRI system,the developed gradient assembly demonstrated good performance and supported to output images of excellent quality.Our findings suggested that the proposed method could potentially form a useful design paradigm for cryogen-free MRI magnets.展开更多
Shield machine is the major technical equipment badly in need in national infrastructure construction. The service conditions of shield machine are extremely complex. The driving interface load fluctuation caused by g...Shield machine is the major technical equipment badly in need in national infrastructure construction. The service conditions of shield machine are extremely complex. The driving interface load fluctuation caused by geological environment changes and multi field coupling of stress field may lead into imbalance of redundant drive motors output torque in main driving system. Therefore, the shield machine driving synchronous control is one of the key technologies of shield machine. This paper is in view of the shield machine main driving synchronous control, achieving the system＇s adaptive load sharing. From the point of view of cutterhead load changes, nonlinear factors of mechanical transmission mechanism and the control system synchronization performance, the authors analyze the load sharing performance of shield machine main drive system in the event of load mutation. The paper proposes a data-driven synchronized control method applicable to the main drive system. The effectiveness of the method is verified through simulation and experimental methods. The new method can make the system synchronization error greatly reduced, thus it can effectively adapt to load mutation, and reduce shaft broken accident.展开更多
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
High-performance MXene-based polymer nanocomposites are well-suited for various industrial applications owing to their excellent mechanical,thermal,and other properties.However,the fabrication of flame-retardant polym...High-performance MXene-based polymer nanocomposites are well-suited for various industrial applications owing to their excellent mechanical,thermal,and other properties.However,the fabrication of flame-retardant polymer/MXene nanocom-posites remains challenging owing to the limited flame-retardant properties of MXene itself.This study prepared a novel MXene@Ag@PA hybrid material via radiation modification and complexation reaction.This material was used to further enhance the key properties of ethylene-vinyl acetate(EVA),such as its mechanical properties,thermal conductivity,flame retardancy,and electromagnetic shielding.The addition of two parts of this hybrid material increased the thermal conduc-tivity of EVA by 44.2%and reduced its peak exothermic rate during combustion by 30.1%compared with pure EVA.The material also significantly reduced smoke production and increased the residue content.In the X-band,the electromagnetic shielding effectiveness of the EVA composites reached 20 dB.Moreover,the MXene@Ag@PA hybrid material could be used to further enhance the mechanical properties of EVA composites under electron-beam irradiation.Thus,this study contributes to the development of MXene-based EVA advanced materials that are fire-safe,have high strength,and exhibit good electromagnetic shielding performance for various applications.展开更多
The performances of magnesium alloys remain insufficient to further enhance the application potential of ultralight magnesium alloys.In this work,a Mg-8Li-3Y-2Zn alloy was prepared through vacuum melting and subsequent...The performances of magnesium alloys remain insufficient to further enhance the application potential of ultralight magnesium alloys.In this work,a Mg-8Li-3Y-2Zn alloy was prepared through vacuum melting and subsequent heat treatment at 300,450,and 500°C.The material properties of the resulting samples were assessed through microstructural observation,tensile testing,electrical conductivity measurements,and electromagnetic shielding effectiveness(EMI-SE)testing.The influence of the Mg-8Li-3Y-2Zn alloy microstructure on its mechanical and electromagnetic shielding properties in different states was investigated.It was found that the as-cast alloy containsα-Mg,β-Li,Mg_(3)Zn_(3)Y_(2),and Mg_(12)ZnY phases.Following heat treatment at 500℃(HT500),the blockα-Mg phase transformedfine needle-shapes,its tensile strength increased to 263.7 MPa,and its elongation reached 45.3%.The mechanical properties of the alloy were significantly improved by the synergistic effects imparted by the needle-shapedα-Mg phase,solid solution strengthening,and precipitation strengthening.The addition of Y and Zn improved the EMI-SE of Mg-8Li-1Zn alloy,wherein the HT500 sample exhibits the highest SE,maintaining a value of 106.7–76.9 dB in the frequency range of 30–4500 MHz;this performance has rarely been reported for electromagnetically shielded alloys.This effect was mainly attributed to the multiple reflections of electromagnetic waves caused by the severe impedance mismatch of the abundant phase boundaries,which were in turn provided by the dual-phase(α/β)and secondary phases.Furthermore,the presence of nano-precipitation was also believed to enhance the absorption of electromagnetic waves.展开更多
In the present work,by virtue of the synergistic and independent effects of Janus structure,an asymmetric nickel-chain/multiwall carbon nanotube/polyimide(Ni/MWCNTs/PI)composite foam with absorption-dominated electrom...In the present work,by virtue of the synergistic and independent effects of Janus structure,an asymmetric nickel-chain/multiwall carbon nanotube/polyimide(Ni/MWCNTs/PI)composite foam with absorption-dominated electromagnetic interference(EMI)shielding and thermal insulation performances was successfully fabricated through an ordered casting and directional freeze-drying strategy.Water-soluble polyamic acid(PAA)was chosen to match the oriented freeze-drying method to acquire oriented pores,and the thermal imidization process from PAA to PI exactly eliminated the interface of the multilayered structure.By controlling the electro-magnetic gradient and propagation path of the incident microwaves in the MWCNT/PI and Ni/PI layers,the PI composite foam exhibited an efficient EMI SE of 55.8 dB in the X-band with extremely low reflection characteristics(R=0.22).The asymmetric conductive net-work also greatly preserved the thermal insulation properties of PI.The thermal conductivity(TC)of the Ni/MWCNT/PI composite foam was as low as 0.032 W/(m K).In addition,owing to the elimination of MWCNT/PI and Ni/PI interfaces during the thermal imidization process,the composite foam showed satisfactory compressive strength.The fabricated PI composite foam could provide reliable electromagnetic protection in complex applications and withstand high temperatures,which has great potential in cuttingedge applications such as advanced aircraft.展开更多
With the wide application of electromagnetic wave,a high performance electromagnetic shielding material is urgently needed to solve the harm caused by electromagnetic wave.Complete cross-linking strategy is adopted in...With the wide application of electromagnetic wave,a high performance electromagnetic shielding material is urgently needed to solve the harm caused by electromagnetic wave.Complete cross-linking strategy is adopted in this paper.Polyacrylamide(PAM)was synthesized by in-situ polymerization of acrylamide(AM)monomer.The obtained PAM was blended with polyethylene glycol(PEG)to prepare PAM/PEG hydrogels and form rigid support structures.Subsequently,the modified carbon nanotubes(S-CNTs)were incorpor-ated into sodium alginate(SA)and PAM/PEG.Finally,Na+was used to trigger SA self-assembly,which significantly improved the mechanical properties and electrical conductivity of the hydrogels,and prepared PAM/PEG/SA/S-CNTs-Na hydrogels with high tough-ness and strong electromagnetic interference(EMI)shielding efficiency(SE).The results showed that the compressive strength of PAM/PEG/SA/S-CNTs-Na hydrogel was 19.05 MPa,which was 7.69%higher than that of PAM/PEG hydrogel(17.69 MPa).More en-couraging,the average EMI SE of PAM/PEG/SA/S-CNTs-Na hydrogels at a thickness of only 3 mm and a CNTs content of 16.53wt%was 32.92 dB,which is 113.21%higher than that of PAM/PEG hydrogels(15.44 dB).展开更多
The recent upsurge in metro construction emphasizes the necessity of understanding the mechanical performance of metro shield tunnel subjected to the influence of ground fissures.In this study,a largescale experiment,...The recent upsurge in metro construction emphasizes the necessity of understanding the mechanical performance of metro shield tunnel subjected to the influence of ground fissures.In this study,a largescale experiment,in combination with numerical simulation,was conducted to investigate the influence of ground fissures on a metro shield tunnel.The results indicate that the lining contact pressure at the vault increases in the hanging wall while decreases in the footwall,resulting in a two-dimensional stress state of vertical shear and axial tension-compression,and simultaneous vertical dislocation and axial tilt for the segments around the ground fissure.In addition,the damage to curved bolts includes tensile yield,flexural yield,and shear twist,leading to obvious concrete lining damage,particularly at the vault,arch bottom,and hance,indicating that the joints in these positions are weak areas.The shield tunnel orthogonal to the ground fissure ultimately experiences shear failure,suggesting that the maximum actual dislocation of ground fissure that the structure can withstand is approximately 20 cm,and five segment rings in the hanging wall and six segment rings in the footwall also need to be reinforced.This study could provide a reference for metro design in ground fissure sites.展开更多
Metal foams are a fascinating group of materials that possess distinct physicochEMIcal properties and interconnected strut features with high surface area-to-volume ratios, high specific strength and lightweight natur...Metal foams are a fascinating group of materials that possess distinct physicochEMIcal properties and interconnected strut features with high surface area-to-volume ratios, high specific strength and lightweight nature. These characteristics make them ideal for applications in vibration damping, heat insulation and weight reduction. In recent years, there has been increasing interest in the application of interfering energy conversion such as electromagnetic wave (EMW) and sound, where the metal foams could emerge as a solution. This paper will present a comprehensive review of the preparation methods as well as the interference energy converting mechanisms for metal foams. Typically, the progress and prospective aspects of metal foams for EMW absorption, electromagnetic interference (EMI) shielding and sound absorption have been emphasized. Through this review, we aspire to offer valuable insights for the development of multifunctional applications with metal foam materials.展开更多
As modern communication and detection technologies advance at a swift pace,multifunctional electromagnetic interference(EMI)shielding materials with active/positive infrared stealth,hydrophobicity,and electric-thermal...As modern communication and detection technologies advance at a swift pace,multifunctional electromagnetic interference(EMI)shielding materials with active/positive infrared stealth,hydrophobicity,and electric-thermal conversion ability have received extensive attention.Meeting the aforesaid requirements simultaneously remains a huge challenge.In this research,the melamine foam(MF)/polypyrrole(PPy)nanowire arrays(MF@PPy)were fabricated via one-step electrochemical polymerization.The hierarchical MF@PPy foam was composed of three-dimensional PPy micro-skeleton and ordered PPy nanowire arrays.Due to the upwardly grown PPy nanowire arrays,the MF@PPy foam possessed good hydrophobicity ability with a water contact angle of 142.00°and outstanding stability under various harsh environments.Meanwhile,the MF@PPy foam showed excellent thermal insulation property on account of the low thermal conductivity and elongated ligament characteristic of PPy nanowire arrays.Furthermore,taking advantage of the high conductivity(128.2 S m^(-1)),the MF@PPy foam exhibited rapid Joule heating under 3 V,resulting in dynamic infrared stealth and thermal camouflage effects.More importantly,the MF@PPy foam exhibited remarkable EMI shielding effectiveness values of 55.77 dB and 19,928.57 dB cm^(2)g^(-1).Strong EMI shielding was put down to the hierarchically porous PPy structure,which offered outstanding impedance matching,conduction loss,and multiple attenuations.This innovative approach provides significant insights to the development of advanced multifunctional EMI shielding foams by constructing PPy nanowire arrays,showing great applications in both military and civilian fields.展开更多
Herein,a novel Janus-structured multifunctional membrane with integrated electromagnetic interference(EMI)shielding and personalized thermal management is fabricated using shear-induced in situ fibrillation and vacuum...Herein,a novel Janus-structured multifunctional membrane with integrated electromagnetic interference(EMI)shielding and personalized thermal management is fabricated using shear-induced in situ fibrillation and vacuum-assisted filtration.Interestingly,within the polytetrafluoroethylene(PTFE)-carbon nanotube(CNT)-Fe_(3)O_(4)layer(FCFe),CNT nanofibers interweave with PTFE fibers to form a stable“silk-like”structure that effectively captures Fe_(3)O_(4)particles.By incorporating a highly conductive MXene layer,the FCFe/MXene(FCFe/M)membrane exhibits excellent electrical/thermal conductivity,mechanical properties,and flame retardancy.Impressively,benefiting from the rational regulation of component proportions and the design of a Janus structure,the FCFe/M membrane with a thickness of only 84.9μm delivers outstanding EMI shielding effectiveness of 44.56 dB in the X-band,with a normalized specific SE reaching 10,421.3 dB cm^(2)g^(-1),which is attributed to the“absorption-reflection-reabsorption”mechanism.Furthermore,the membrane demonstrates low-voltage-driven Joule heating and fast-response photothermal performance.Under the stimulation of a 3 V voltage and an optical power density of 320 mW cm^(-2),the surface temperatures of the FCFe/M membranes can reach up to 140.4 and 145.7℃,respectively.In brief,the FCFe/M membrane with anti-electromagnetic radiation and temperature regulation is an attractive candidate for the next generation of wearable electronics,EMI compatibility,visual heating,thermotherapy,and military and aerospace applications.展开更多
基金“High precision prestack reverse time depth migration imaging of long array seismic data in the East China Sea Shelf Basin”of the National Natural Science Foundation of China(No.42106207)“Seismic acquisition technology for deep strata under strong shielding layers in the sea and rugged seabed”of Laoshan Laboratory Science and Technology Innovation Project(No.LSKJ202203404)“Research on the compensation methods of the middledeep weak seismic reflections in the South Yellow Sea based on multi-resolution HHT time-frequency analysis”of the National Natural Science Foundation of China(No.42106208).
文摘The seismic data of the Laoshan Uplift in the South Yellow Sea Basin reveal a low signal-tonoise ratio and low refl ection signal energy in the deep Mesozoic–Paleozoic strata.The main reason is that the Mesozoic-Paleozoic marine carbonate rock strata are directly covered by the Cenozoic terrestrial clastic rock strata,which form a strong shielding layer.To obtain the reflection signals of the strata below the strong shielding layer,a one-way wave equation bidirectional illumination analysis of the main observation system parameters was conducted by analyzing the mechanism of the strong shielding layer.Low-frequency seismic sources are assumed to have a high illumination intensity on the reflection layer below the strong shielding layer.Accordingly,optimized acquisition parameter suggestions were proposed,and reacquisition was performed at the existing survey line locations in the Laoshan Uplift area.The imaging of the newly acquired data in the middle and deep layers was drastically improved.It revealed the unconformity between the Sinian and Cambrian under the strong shielding layer.The study yielded new insights into the tectonic and sedimentary evolution of the Lower Paleozoic in the South Yellow Sea.
基金the National Natural Science Foundation of China(Nos.52373073,52073091,52303083,22171086)the Shanghai Pujiang Program(No.22PJ1402500)the Fundamental Research Funds for the Central Universities(No.JKD01231701).
文摘The investigation of absorption-led shielding mechanisms has now made practical progress as a result of the concept of green EM shielding.The extant studies primarily concentrate on the introduction of mag-netic particles into the system,with the objective of enhancing the absorption rate(A)through dielectric-magnetic modulation for absorption-led electromagnetic shielding.In contrast,this paper presents a novel approach whereby PVA,glycerol,and MXene are combined into an organohydrogel(PMG)with oriented pores.This results in the creation of a non-magnetic medium that exhibits high absorption loss in mul-tiple bands,thereby establishing a novel shielding system.The PMG20-3 organohydrogel(0.78 wt%MX-ene)has a shielding performance in the X-band of 42.34 dB(A/R=1).In the terahertz band,the organic hydrogel gel exhibits an absorption rate of 99.9%,a performance that exceeds that of the majority of previously reported systems.The PMG gel displays remarkable flexibility and strength,with a hysteresis return line that remains stable under 1000 compression cycles.Additionally,it offers versatile sensing capabilities and infrared stealth.The findings of this study offer novel insights that may facilitate the accelerated utilization of innovative multifunctional and environmentally conscious electromagnetic in-terference(EMI)shielding materials.
基金Supported by the National Natural Science Foundation of China(22378181).
文摘The development of materials with excellent microwave absorption(MWA)and electromagnetic interference(EMI)shielding performances has currently received attention.Herein,mesophase pitch-based carbon foam(MPCF)with 3D interconnected pore structure was prepared through the high pressure pyrolysis of mesophase coal tar pitch.It is found that the 3D interconnected cellular pores of MPCF facilitate multiple reflections of electromagnetic waves,which results in the minimum reflection loss(RLmin)value of MPCF reaches-37.84 dB with the effective absorption bandwidth(EAB)of 5.44 GHz at a thickness of 2.70 mm,and the total average electromagnetic shielding effectiveness(SE_(T))under 3.00 mm thickness achieves 26.52 dB in X-band.Subsequently,MPCF is activated by KOH to obtain activated carbon foam(A-MPCF).The average SE_(T)of A-MPCF achieves 103.00 dB for abundant nanopores on the pore cell walls,which leads to a transition from the multiple reflections of electromagnetic waves on the walls to diffuse reflection.Unfortunately,the reflection coefficient(R)of A-MPCF increases from 0.78 to 0.90.To reduce the R value,Fe_(3)O_(4)/A-MPCF was fabricated via the in situ growth of nano Fe_(3)O_(4)on A-MPCF.Consequently,the R value of Fe_(3)O_(4)/A-MPCF was reduced from 0.90 to 0.74,whereas the MWA performance was only slightly decreased.This work proposes a simple strategy for simultaneously adjusting MWA and EMI shielding performances of materials.
基金support provided by the Center for Fabrication and Application of Electronic Materials at Dokuz Eylül University,Türkiye。
文摘Biochar and biochar composites are versatile materials that can be used in many applications.In this study,biochar was prepared from sawdust and combined with the yttrium iron garnet(YIG)nanocrystal to investigate the shielding effectiveness of the composite structure.Firstly,the effect of the pyrolysis temperature on the shielding effectiveness of biochar was investigated.Secondly,biochars combined with YIG nanocrystals with different contents and shielding effectiveness of the composites were investigated.The electromagnetic effectiveness of the samples was investigated within the X band(8-12 GHz).The findings indicate that biochar demonstrates enhanced absorption properties with elevated pyrolysis temperatures.Biochars demonstrated an approximate 40 d B shielding effectiveness,while YIG exhibited approximately 7 d B,corresponding to absorption at 8 GHz.However,the combination of biochar and YIG exhibited exceptional absorption,reaching 67.12 d B at 8 GHz.
基金supported by the Guangdong Basic and Applied Basic Research Foundation,China(No.2021B1515140007).
文摘In a rapid cycling synchrotron(RCS),the magnetic field is synchronized with the beam energy,creating a highly dynamic magnetic environment.A ceramic chamber with a shielding layer(RF shield),composed of a series of copper strips connected to a capacitor at either end,is typically employed as a vacuum chamber to mitigate eddy current effects and beam coupling impedance.Consequently,the ceramic chamber exhibits a thin-walled multilayered complex structure.Previous theoretical studies have suggested that the impedance of such a structure has a negligible impact on the beam.However,recent impedance measurements of the ceramic chamber in the China Spallation Neutron Source(CSNS)RCS revealed a resonance in the low-frequency range,which was confirmed by further theoretical analysis as a source of beam instability in the RCS.Currently,the magnitude of this impedance cannot be accurately assessed using theoretical calculations.In this study,we used the CST Microwave Studio to confirm the impedance of the ceramic chamber.Further simulations covering six different types of ceramic chambers were conducted to develop an impedance model in the RCS.Additionally,this study investigates the resonant characteristics of the ceramic chamber impedance,finding that the resonant frequency is closely related to the capacitance of the capacitors.This finding provides clear directions for further impedance optimization and is crucial for achieving a beam power of 500 kW for the CSNS Phase-Ⅱ project(CSNS-Ⅱ).However,careful attention must be paid to the voltage across the capacitors.
基金Project(50425518) supported by National Outstanding Youth Foundation of China Project(2007CB714004) supported by National Basic Research Program of China
文摘The thrust hydraulic system of the prototype shield machine with pressure and flow compound control scheme was introduced. The experimental system integrated with proportional valves for study was designed. Dynamics modeling of multi-cylinder thrust system and synchronous control design were accomplished. The simulation of the synchronization motion control system was completed in AMESim and Matlab/Simulink software environments. The experiment was conducted by means of master/slave PID with dead band compensating flow and conventional PID regulating pressure. The experimental results show that the proposed thrust hydraulic system and its control strategy can meet the requirements of tunneling in motion and posture control for the shield machine, keeping the non-synchronous error within ±3 mm.
基金Supported by the National Basic Research Program of China(2007CB714006)the National Natural Science Foundation of China(90815023)
文摘An estimation approach using least squares method was presented for identificationof model parameters of pressure control in shield tunneling.The state equation ofthe pressure control system for shield tunneling was analytically derived based on themass equilibrium principle that the entry mass of the pressure chamber from cutting headwas equal to excluding mass from the screw conveyor.The randomly observed noise wasnumerically simulated and mixed to simulated observation values of system responses.The numerical simulation shows that the state equation of the pressure control system forshield tunneling is reasonable and the proposed estimation approach is effective even ifthe random observation noise exists.The robustness of the controlling procedure is validatedby numerical simulation results.
基金supported by National Natural Science Foundation of China(No.51872253)supported by Hebei Natural Science Foundation of China(No.E2019203480).
文摘The development of the preparation strategy for high-quality and large-size graphene via eco-friendly routes is still a challenging issue.Herein,we have successfully developed a novel route to chemically exfoliate natural graphite into high-quality and large-size graphene in a binary-peroxidant system.This system is composed of urea peroxide(CO(NH_(2))_(2)·H_(2)O_(2))and hydrogen peroxide(H_(2)O_(2)),where CO(NH_(2))_(2)·H_(2)O_(2)is used in preparing graphene for the first time.Benefiting from the complete decomposition of CO(NH_(2))_(2)·H_(2)O_(2)and H_(2)O_(2)into gaseous species under microwave(MW)irradiation,no water-washing and effluent-treatment are needed in this chemical exfoliation procedure,thus the preparation of graphene in an eco-friendly way is realized.The resultant graphene behaves a large-size,high-quality and few-layer feature with a yield of~100%.Then 4µm-thick ultrathin graphene paper fabricated from the as-exfoliated graphene is used as an electromagnetic interference(EMI)shielding material.And its absolute effectiveness of EMI shielding(SSE/t)is up to 34,176.9 dB cm^(2)/g,which is,to the best of our knowledge,among the highest values so far reported for typical EMI shielding materials.The EMI shielding performance demonstrates a great application potential of graphene paper in meeting the ever-increasingly EMI shielding demands in miniaturized electronic devices.
基金financially supported by the National Natural Science Foundation of China(Nos.51203132,51222307,51303173,51390484,21474104 and 51403205)Natural Science Foundation of Guangdong Province,China(S2012040008070)Foundation for Distinguished Young Talents in Higher Education of Guangdong,China(2012LYM_0093)
文摘For the purpose of increasing the in vivo stability of polycation gene carriers, we prepared a kind of p H-sensitive poly（ethylene glycol）-poly（γ-benzyl-L-glutamate-co-glutamic acid）（PEG-PGA（65）, 65 denotes the molar ratio of glutamic acid in poly（γ-benzyl-L-glutamate-co-glutamic acid））. PEG-PGA（65） showed low cytotoxicity and could shield the positive charge of DNA/PEI（1：1） polyplexes efficiently. The transfection was enhanced due to the partially charge shielding in He La cell line at pH of 7.4. There was almost no transfection efficiency when the surface charge of the ternary particles turned to negative at p H of 7.4. However, the transfection efficiency recovered a lot by culturing at p H of 6.0 at the beginning of transfection. Confocal microscopic observation and flow cytometry results showed DNA/PEI polyplexes should be efficiently released and endocytosized at p H 6.0, because of the p H triggered deshielding action of PEG-PGA（65）. Due to the good biocompatibility and suitable p H triggered shielding/deshielding property, PEG-PGA（65） could be a potential shielding system for polycationic gene carriers used in vivo.
基金This work is funded by the Magnetic Resonance Union of the Chinese Academy of Sciences(Grant No.2021gzl002)the International Partnership Program of Chinese Academy of Sciences(Grant No.182111KYSB20210014)+1 种基金the National Science Foundation of China(Grant No.52293423,Grant No.52277031)the Research and Development of Key Technologies and Equipment for Major Science and Technology Infrastructure of Development and Reform Commission of Shenzhen Municipality,China(Grant No.ZDKJ20190305002).
文摘The relatively fragile low-temperature stability of cryogen-free superconducting magnetic resonance imaging(MRI)magnets requires the careful management of exogenous heat sources.A strongly shielded gradient magnetic field is important for the optimal operation of cryogen-free MRI systems.In this study,we present an enhanced shielding method incorporating a regionalized stray field constraining strategy.By optimizing the constraint parameters,we could develop engineering-feasible gradient coil schemes without increasing system complexity but with the stray field intensity reduced by half.In real measurement in an integrated MRI system,the developed gradient assembly demonstrated good performance and supported to output images of excellent quality.Our findings suggested that the proposed method could potentially form a useful design paradigm for cryogen-free MRI magnets.
文摘Shield machine is the major technical equipment badly in need in national infrastructure construction. The service conditions of shield machine are extremely complex. The driving interface load fluctuation caused by geological environment changes and multi field coupling of stress field may lead into imbalance of redundant drive motors output torque in main driving system. Therefore, the shield machine driving synchronous control is one of the key technologies of shield machine. This paper is in view of the shield machine main driving synchronous control, achieving the system＇s adaptive load sharing. From the point of view of cutterhead load changes, nonlinear factors of mechanical transmission mechanism and the control system synchronization performance, the authors analyze the load sharing performance of shield machine main drive system in the event of load mutation. The paper proposes a data-driven synchronized control method applicable to the main drive system. The effectiveness of the method is verified through simulation and experimental methods. The new method can make the system synchronization error greatly reduced, thus it can effectively adapt to load mutation, and reduce shaft broken accident.
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.
文摘High-performance MXene-based polymer nanocomposites are well-suited for various industrial applications owing to their excellent mechanical,thermal,and other properties.However,the fabrication of flame-retardant polymer/MXene nanocom-posites remains challenging owing to the limited flame-retardant properties of MXene itself.This study prepared a novel MXene@Ag@PA hybrid material via radiation modification and complexation reaction.This material was used to further enhance the key properties of ethylene-vinyl acetate(EVA),such as its mechanical properties,thermal conductivity,flame retardancy,and electromagnetic shielding.The addition of two parts of this hybrid material increased the thermal conduc-tivity of EVA by 44.2%and reduced its peak exothermic rate during combustion by 30.1%compared with pure EVA.The material also significantly reduced smoke production and increased the residue content.In the X-band,the electromagnetic shielding effectiveness of the EVA composites reached 20 dB.Moreover,the MXene@Ag@PA hybrid material could be used to further enhance the mechanical properties of EVA composites under electron-beam irradiation.Thus,this study contributes to the development of MXene-based EVA advanced materials that are fire-safe,have high strength,and exhibit good electromagnetic shielding performance for various applications.
基金supported by the National Natural Sci-ence Foundation of China[No.51564032]Yunnan Provin-cial Department of Education Science Research Fund Project[KKPH202132005]the Analysis and Testing Founda-tion of Kunming University of Science and Technology[2022M20212130086].
文摘The performances of magnesium alloys remain insufficient to further enhance the application potential of ultralight magnesium alloys.In this work,a Mg-8Li-3Y-2Zn alloy was prepared through vacuum melting and subsequent heat treatment at 300,450,and 500°C.The material properties of the resulting samples were assessed through microstructural observation,tensile testing,electrical conductivity measurements,and electromagnetic shielding effectiveness(EMI-SE)testing.The influence of the Mg-8Li-3Y-2Zn alloy microstructure on its mechanical and electromagnetic shielding properties in different states was investigated.It was found that the as-cast alloy containsα-Mg,β-Li,Mg_(3)Zn_(3)Y_(2),and Mg_(12)ZnY phases.Following heat treatment at 500℃(HT500),the blockα-Mg phase transformedfine needle-shapes,its tensile strength increased to 263.7 MPa,and its elongation reached 45.3%.The mechanical properties of the alloy were significantly improved by the synergistic effects imparted by the needle-shapedα-Mg phase,solid solution strengthening,and precipitation strengthening.The addition of Y and Zn improved the EMI-SE of Mg-8Li-1Zn alloy,wherein the HT500 sample exhibits the highest SE,maintaining a value of 106.7–76.9 dB in the frequency range of 30–4500 MHz;this performance has rarely been reported for electromagnetically shielded alloys.This effect was mainly attributed to the multiple reflections of electromagnetic waves caused by the severe impedance mismatch of the abundant phase boundaries,which were in turn provided by the dual-phase(α/β)and secondary phases.Furthermore,the presence of nano-precipitation was also believed to enhance the absorption of electromagnetic waves.
基金supported by the Natural Science Foundation of Shanxi Province(Nos.20210302123015 and 20210302123035)the Opening Project of State Key Laboratory of Polymer Materials Engineering(Sichuan University)(No.sklpme2022-4-06)the Open Foundation of China-Belarus Belt and Road Joint Laboratory on Electromagnetic Environment Effect(No.ZBKF2022030301).
文摘In the present work,by virtue of the synergistic and independent effects of Janus structure,an asymmetric nickel-chain/multiwall carbon nanotube/polyimide(Ni/MWCNTs/PI)composite foam with absorption-dominated electromagnetic interference(EMI)shielding and thermal insulation performances was successfully fabricated through an ordered casting and directional freeze-drying strategy.Water-soluble polyamic acid(PAA)was chosen to match the oriented freeze-drying method to acquire oriented pores,and the thermal imidization process from PAA to PI exactly eliminated the interface of the multilayered structure.By controlling the electro-magnetic gradient and propagation path of the incident microwaves in the MWCNT/PI and Ni/PI layers,the PI composite foam exhibited an efficient EMI SE of 55.8 dB in the X-band with extremely low reflection characteristics(R=0.22).The asymmetric conductive net-work also greatly preserved the thermal insulation properties of PI.The thermal conductivity(TC)of the Ni/MWCNT/PI composite foam was as low as 0.032 W/(m K).In addition,owing to the elimination of MWCNT/PI and Ni/PI interfaces during the thermal imidization process,the composite foam showed satisfactory compressive strength.The fabricated PI composite foam could provide reliable electromagnetic protection in complex applications and withstand high temperatures,which has great potential in cuttingedge applications such as advanced aircraft.
基金supported by the National Natural Science Foundation of China(No.52163001)the Guizhou Provincial Science and Technology Program Project Grant,China(Qiankehe Platform Talents-CXTD[2021]005,Qiankehe Platform Talents-GCC[2022]010-1,Qiankehe Fuqi[2023]001,Qiankehe Platform Talents-GCC[2023]035,and Qiankehe Platform Talents-CXTD[2023]003)+3 种基金the Guizhou Minzu University Research Platform Grant,China(No.GZMUGCZX[2021]01)the Central Guided Local Science and Technology Development Funds Project,China(Qiankehe Zhong Yindi[2023]035)the Green Chemistry and Resource Environment Innovation Team of Guizhou Higher Education Institutions,China(Guizhou Education and Technology[2022]No.13)the Doctor Startup Fund of Guizhou Minzu University,China(No.GZMUZK[2024]QD77).
文摘With the wide application of electromagnetic wave,a high performance electromagnetic shielding material is urgently needed to solve the harm caused by electromagnetic wave.Complete cross-linking strategy is adopted in this paper.Polyacrylamide(PAM)was synthesized by in-situ polymerization of acrylamide(AM)monomer.The obtained PAM was blended with polyethylene glycol(PEG)to prepare PAM/PEG hydrogels and form rigid support structures.Subsequently,the modified carbon nanotubes(S-CNTs)were incorpor-ated into sodium alginate(SA)and PAM/PEG.Finally,Na+was used to trigger SA self-assembly,which significantly improved the mechanical properties and electrical conductivity of the hydrogels,and prepared PAM/PEG/SA/S-CNTs-Na hydrogels with high tough-ness and strong electromagnetic interference(EMI)shielding efficiency(SE).The results showed that the compressive strength of PAM/PEG/SA/S-CNTs-Na hydrogel was 19.05 MPa,which was 7.69%higher than that of PAM/PEG hydrogel(17.69 MPa).More en-couraging,the average EMI SE of PAM/PEG/SA/S-CNTs-Na hydrogels at a thickness of only 3 mm and a CNTs content of 16.53wt%was 32.92 dB,which is 113.21%higher than that of PAM/PEG hydrogels(15.44 dB).
基金supported by the National Key Research&Development Program of China(Grant No.2023YFC3008404)the Key Laboratory of Earth Fissures Geological Disaster,Ministry of Natural Resources,China(Grant Nos.EFGD20240609 and EFGD20240610).
文摘The recent upsurge in metro construction emphasizes the necessity of understanding the mechanical performance of metro shield tunnel subjected to the influence of ground fissures.In this study,a largescale experiment,in combination with numerical simulation,was conducted to investigate the influence of ground fissures on a metro shield tunnel.The results indicate that the lining contact pressure at the vault increases in the hanging wall while decreases in the footwall,resulting in a two-dimensional stress state of vertical shear and axial tension-compression,and simultaneous vertical dislocation and axial tilt for the segments around the ground fissure.In addition,the damage to curved bolts includes tensile yield,flexural yield,and shear twist,leading to obvious concrete lining damage,particularly at the vault,arch bottom,and hance,indicating that the joints in these positions are weak areas.The shield tunnel orthogonal to the ground fissure ultimately experiences shear failure,suggesting that the maximum actual dislocation of ground fissure that the structure can withstand is approximately 20 cm,and five segment rings in the hanging wall and six segment rings in the footwall also need to be reinforced.This study could provide a reference for metro design in ground fissure sites.
基金supported by the National Natural Science Foundation of China(No.52271180)the Leading Goose R&D Program of Zhejiang Province(2022C01110).
文摘Metal foams are a fascinating group of materials that possess distinct physicochEMIcal properties and interconnected strut features with high surface area-to-volume ratios, high specific strength and lightweight nature. These characteristics make them ideal for applications in vibration damping, heat insulation and weight reduction. In recent years, there has been increasing interest in the application of interfering energy conversion such as electromagnetic wave (EMW) and sound, where the metal foams could emerge as a solution. This paper will present a comprehensive review of the preparation methods as well as the interference energy converting mechanisms for metal foams. Typically, the progress and prospective aspects of metal foams for EMW absorption, electromagnetic interference (EMI) shielding and sound absorption have been emphasized. Through this review, we aspire to offer valuable insights for the development of multifunctional applications with metal foam materials.
基金supported by the Key Research and Development Program of Sichuan Province(Grant No.2023ZHCG0050)the Fundamental Research Funds for the Central Universities of China(Grant No.2682024QZ006 and 2682024ZTPY042)the Analytic and Testing Center of Southwest Jiaotong University.
文摘As modern communication and detection technologies advance at a swift pace,multifunctional electromagnetic interference(EMI)shielding materials with active/positive infrared stealth,hydrophobicity,and electric-thermal conversion ability have received extensive attention.Meeting the aforesaid requirements simultaneously remains a huge challenge.In this research,the melamine foam(MF)/polypyrrole(PPy)nanowire arrays(MF@PPy)were fabricated via one-step electrochemical polymerization.The hierarchical MF@PPy foam was composed of three-dimensional PPy micro-skeleton and ordered PPy nanowire arrays.Due to the upwardly grown PPy nanowire arrays,the MF@PPy foam possessed good hydrophobicity ability with a water contact angle of 142.00°and outstanding stability under various harsh environments.Meanwhile,the MF@PPy foam showed excellent thermal insulation property on account of the low thermal conductivity and elongated ligament characteristic of PPy nanowire arrays.Furthermore,taking advantage of the high conductivity(128.2 S m^(-1)),the MF@PPy foam exhibited rapid Joule heating under 3 V,resulting in dynamic infrared stealth and thermal camouflage effects.More importantly,the MF@PPy foam exhibited remarkable EMI shielding effectiveness values of 55.77 dB and 19,928.57 dB cm^(2)g^(-1).Strong EMI shielding was put down to the hierarchically porous PPy structure,which offered outstanding impedance matching,conduction loss,and multiple attenuations.This innovative approach provides significant insights to the development of advanced multifunctional EMI shielding foams by constructing PPy nanowire arrays,showing great applications in both military and civilian fields.
基金support from the National Natural Science Foundation of China(NSFC,Grant No.52175341)Shandong Provincial Natural Science Foundation(Grant No.ZR2022JQ24)Funding Project of Jinan City’s New Twenty Items for Colleges and Universities(Grant No.202333038).
文摘Herein,a novel Janus-structured multifunctional membrane with integrated electromagnetic interference(EMI)shielding and personalized thermal management is fabricated using shear-induced in situ fibrillation and vacuum-assisted filtration.Interestingly,within the polytetrafluoroethylene(PTFE)-carbon nanotube(CNT)-Fe_(3)O_(4)layer(FCFe),CNT nanofibers interweave with PTFE fibers to form a stable“silk-like”structure that effectively captures Fe_(3)O_(4)particles.By incorporating a highly conductive MXene layer,the FCFe/MXene(FCFe/M)membrane exhibits excellent electrical/thermal conductivity,mechanical properties,and flame retardancy.Impressively,benefiting from the rational regulation of component proportions and the design of a Janus structure,the FCFe/M membrane with a thickness of only 84.9μm delivers outstanding EMI shielding effectiveness of 44.56 dB in the X-band,with a normalized specific SE reaching 10,421.3 dB cm^(2)g^(-1),which is attributed to the“absorption-reflection-reabsorption”mechanism.Furthermore,the membrane demonstrates low-voltage-driven Joule heating and fast-response photothermal performance.Under the stimulation of a 3 V voltage and an optical power density of 320 mW cm^(-2),the surface temperatures of the FCFe/M membranes can reach up to 140.4 and 145.7℃,respectively.In brief,the FCFe/M membrane with anti-electromagnetic radiation and temperature regulation is an attractive candidate for the next generation of wearable electronics,EMI compatibility,visual heating,thermotherapy,and military and aerospace applications.
