With the miniaturization and high-frequency evolution of antennas in 5G/6G communications,aerospace,and transportation,polymer composite papers integrating superior wave-transparent performance and thermal conductivit...With the miniaturization and high-frequency evolution of antennas in 5G/6G communications,aerospace,and transportation,polymer composite papers integrating superior wave-transparent performance and thermal conductivity for radar antenna systems are urgently needed.Herein,a down-top strategy was employed to synthesize poly(p-phenylene benzobisoxazole)precursor nanofibers(prePNF).The prePNF was then uniformly mixed with fluorinated graphene(FG)to fabricate FG/PNF composite papers through consecutively suction filtration,hot-pressing,and thermal annealing.The hydroxyl and amino groups in prePNF enhanced the stability of FG/prePNF dispersion,while the increasedπ-πinteractions between PNF and FG after annealing improved their compatibility.The preparation time and cost of PNF paper was significantly reduced when applying this strategy,which enabled its large-scale production.Furthermore,the prepared FG/PNF composite papers exhibited excellent wave-transparent performance and thermal conductivity.When the mass fraction of FG was 40 wt%,the FG/PNF composite paper prepared via the down-top strategy achieved the wave-transparent coefficient(|T|2)of 96.3%under 10 GHz,in-plane thermal conductivity(λ_(∥))of 7.13 W m^(−1)K^(−1),and through-plane thermal conductivity(λ_(⊥))of 0.67 W m^(−1)K^(−1),outperforming FG/PNF composite paper prepared by the top-down strategy(|T|2=95.9%,λ_(∥)=5.52 W m^(−1)K^(−1),λ_(⊥)=0.52 W m^(−1)K^(−1))and pure PNF paper(|T|2=94.7%,λ_(∥)=3.04 W m^(−1)K^(−1),λ_(⊥)=0.24 W m^(−1)K^(−1)).Meanwhile,FG/PNF composite paper(with 40 wt%FG)through the down-top strategy also demonstrated outstanding mechanical properties with tensile strength and toughness reaching 197.4 MPa and 11.6 MJ m^(−3),respectively.展开更多
Currently,the demand for electromagnetic wave(EMW)absorbing materials with specific functions and capable of withstanding harsh environments is becoming increasingly urgent.Multi-component interface engineering is con...Currently,the demand for electromagnetic wave(EMW)absorbing materials with specific functions and capable of withstanding harsh environments is becoming increasingly urgent.Multi-component interface engineering is considered an effective means to achieve high-efficiency EMW absorption.However,interface modulation engineering has not been fully discussed and has great potential in the field of EMW absorption.In this study,multi-component tin compound fiber composites based on carbon fiber(CF)substrate were prepared by electrospinning,hydrothermal synthesis,and high-temperature thermal reduction.By utilizing the different properties of different substances,rich heterogeneous interfaces are constructed.This effectively promotes charge transfer and enhances interfacial polarization and conduction loss.The prepared SnS/SnS_(2)/SnO_(2)/CF composites with abundant heterogeneous interfaces have and exhibit excellent EMW absorption properties at a loading of 50 wt%in epoxy resin.The minimum reflection loss(RL)is−46.74 dB and the maximum effective absorption bandwidth is 5.28 GHz.Moreover,SnS/SnS_(2)/SnO_(2)/CF epoxy composite coatings exhibited long-term corrosion resistance on Q235 steel surfaces.Therefore,this study provides an effective strategy for the design of high-efficiency EMW absorbing materials in complex and harsh environments.展开更多
Gradient magnetic heterointerfaces have injected infinite vitality in optimizing impedance matching,adjusting dielectric/magnetic resonance and promoting electromagnetic(EM)wave absorption,but still exist a significan...Gradient magnetic heterointerfaces have injected infinite vitality in optimizing impedance matching,adjusting dielectric/magnetic resonance and promoting electromagnetic(EM)wave absorption,but still exist a significant challenging in regulating local phase evolution.Herein,accordion-shaped Co/Co_(3)O_(4)@N-doped carbon nanosheets(Co/Co_(3)O_(4)@NC)with gradient magnetic heterointerfaces have been fabricated via the cooperative high-temperature carbonization and lowtemperature oxidation process.The results indicate that the surface epitaxial growth of crystal Co_(3)O_(4) domains on local Co nanoparticles realizes the adjustment of magnetic-heteroatomic components,which are beneficial for optimizing impedance matching and interfacial polarization.Moreover,gradient magnetic heterointerfaces simultaneously realize magnetic coupling,and long-range magnetic diffraction.Specifically,the synthesized Co/Co_(3)O_(4)@NC absorbents display the strong electromagnetic wave attenuation capability of−53.5 dB at a thickness of 3.0 mm with an effective absorption bandwidth of 5.36 GHz,both are superior to those of single magnetic domains embedded in carbon matrix.This design concept provides us an inspiration in optimizing interfacial polarization,regulating magnetic coupling and promoting electromagnetic wave absorption.展开更多
With the continuous development of electronic devices and the information industry towards miniaturization,integration,and high-power consumption,the using of electronic devices will inevitably generate and accumulate...With the continuous development of electronic devices and the information industry towards miniaturization,integration,and high-power consumption,the using of electronic devices will inevitably generate and accumulate heat,which will cause local high temperatures and will seriously reduce their performance,reliability,and lifetime.Therefore,having efficient heat-conducting functional materials is crucial to the normal and stable operation of electrical equipment and microelectronic products.In view of the excellent comprehensive performance of polymer-based thermally conductive materials(including intrinsic polymers and filler-filled polymer-based composites),it has shown great advantages in thermal management applications.In this review,the research status of preparing polymer-based thermally conductive composites and effective strategies to improve their thermal conductivity(TC)are reviewed.Compared with the higher cost and technical support with adjusting the molecular chain structure and cross-linking mode to improve the intrinsic TC of the polymer,introducing suitable fillers into the polymer to build a thermally conductive network or oriented structure can simply and efficiently improve the overall TC.Typical applications of polymer-based composites were discussed with detailed examples in the field of electronic packaging.Challenges and possible solutions to solve the issues are discussed together with the perspectives.This study provides guidance for the future development of polymer-based thermally conductive composites.展开更多
The microstructure design for thermal conduction pathways in polymeric electrical encapsulation materials is essential to meet the stringent requirements for efficient thermal management and thermal runaway safety in ...The microstructure design for thermal conduction pathways in polymeric electrical encapsulation materials is essential to meet the stringent requirements for efficient thermal management and thermal runaway safety in modern electronic devices.Hence,a composite with three-dimensional network(Ho/U-BNNS/WPU)is developed by simultaneously incorporating magnetically modified boron nitride nanosheets(M@BNNS)and non-magnetic organo-grafted BNNS(U-BNNS)into waterborne polyurethane(WPU)to synchronous molding under a horizontal magnetic field.The results indicate that the continuous in-plane pathways formed by M@BNNS aligned along the magnetic field direction,combined with the bridging structure established by U-BNNS,enable Ho/U-BNNS/WPU to exhibit exceptional in-plane(λ//)and through-plane thermal conductivities(λ_(⊥)).In particular,with the addition of 30 wt%M@BNNS and 5 wt%U-BNNS,theλ//andλ_(⊥)of composites reach 11.47 and 2.88 W m^(-1) K^(-1),respectively,which representing a 194.2%improvement inλ_(⊥)compared to the composites with a single orientation of M@BNNS.Meanwhile,Ho/U-BNNS/WPU exhibits distinguished thermal management capabilities as thermal interface materials for LED and chips.The composites also demonstrate excellent flame retardancy,with a peak heat release and total heat release reduced by 58.9%and 36.9%,respectively,compared to WPU.Thus,this work offers new insights into the thermally conductive structural design and efficient flame-retardant systems of polymer composites,presenting broad application potential in electronic packaging fields.展开更多
The preparation of electromagnetic(EM)wave absorption materials provided with the characteristics of thin matching thickness,broad bandwidth,and mighty absorption intensity is an efficient solution to current EM pollu...The preparation of electromagnetic(EM)wave absorption materials provided with the characteristics of thin matching thickness,broad bandwidth,and mighty absorption intensity is an efficient solution to current EM pollution.Herein,Graphene nanosheets(GN)were firstly fabricated via a facile high-energy ball milling method,subsequently high-purity 1T-MoS_(2) petals were uniformly anchored on the surface of GN to prepare 1T-MoS_(2)@GN nanocomposites.Plentiful multiple reflection and scattering of EM waves in a distinctive multidimensional structure formed by GN and 1T-MoS_(2),copious polarization loss consisting of interfacial polarization loss and dipolar polarization loss severally derived from multitudinous heterointerfaces and profuse electric dipoles in 1T-MoS_(2)@GN,and mighty conduction loss originated from plentiful induced current in 1T-MoS_(2)@GN generated via the migration of massive electrons,all of which endowed 1T-MoS_(2)@GN nanocomposites with exceptional EM wave absorption performances.The minimum reflection loss(RLmin)of 1T-MoS_(2)@GN reached–50.14 dB at a thickness of only 2.10 mm,and the effective absorption bandwidth(EAB)was up to 6.72 GHz at an ultra-thin matching thickness of 1.84 mm.Moreover,the radar scattering cross section(RCS)reduction value of 36.18 dB m2 at 0°could be achieved as well,which ulteriorly validated the tremendous potential of 1T-MoS_(2)@GN nanocomposites in practical applications.展开更多
Flexible multifunctional polymer-based electromagnetic interference(EMI)shielding composite films play a pivotal role in 5 G communication technology,smart wearables,automotive electronics,and aerospace.In this work,(...Flexible multifunctional polymer-based electromagnetic interference(EMI)shielding composite films play a pivotal role in 5 G communication technology,smart wearables,automotive electronics,and aerospace.In this work,(Ti_(3)C_(2)T_(x) MXene/cellulose nanofibers(CNF)-(hydroxy‑functionalized BNNS(BNNS-OH)/CNF)composite films(TBCF)with Janus structure are prepared via vacuum-assisted filtration of BNNS-OH/CNF and Ti_(3)C_(2)T_(x)/CNF suspension by one after another.Then ionic bonding-strengthened TBCF(ITBCF)is obtained by Ca^(2+)ion infiltration and cold-pressing technique.The Janus structure endows ITBCF with the unique“conductive on one side and insulating on the other”property.When the mass ratio of Ti_(3)C_(2)T_(x) and BNNS is 1:1 and the total mass fraction is 70 wt.%,the electrical conductivity(σ)of the Ti_(3)C_(2)T_(x)/CNF side of ITBCF reaches 166.7 S/cm,while the surface resistivity of the BNNS-OH/CNF side is as high as 304 MΩ.After Ca^(2+)ion infiltration,the mechanical properties of ITBCF are significantly enhanced.The tensile strength and modulus of ITBCF are 73.5 MPa and 15.6 GPa,which are increased by 75.9%and 46.2%compared with those of TBCF,respectively.Moreover,ITBCF exhibits outstanding EMI shielding effectiveness(SE)of 57 dB and thermal conductivity(λ)of 9.49 W/(m K).In addition,ITBCF also presents excellent photothermal and photoelectric energy conversion performance.Under simulated solar irradiation with a power density of 120 mW/cm^(2),the surface stabilization temperature reaches up to 65.3°C and the maximum steady state voltage reaches up to 58.2 mV.展开更多
The previous studies mainly focused on improving microwave absorbing(MA)performances of MA materials.Even so,these designed MA materials were very difficult to be employed in complex and changing environments owing to...The previous studies mainly focused on improving microwave absorbing(MA)performances of MA materials.Even so,these designed MA materials were very difficult to be employed in complex and changing environments owing to their single-functionalities.Herein,a combined Prussian blue analogues derived and catalytical chemical vapor deposition strategy was proposed to produce hierarchical cubic sea urchin-like yolk–shell CoNi@Ndoped carbon(NC)-CoNi@carbon nanotubes(CNTs)mixed-dimensional multicomponent nanocomposites(MCNCs),which were composed of zerodimensional CoNi nanoparticles,three-dimensional NC nanocubes and onedimensional CNTs.Because of good impedance matching and attenuation characteristics,the designed CoNi@NC-CoNi@CNTs mixed-dimensional MCNCs exhibited excellent MA performances,which achieved a minimum reflection loss(RL_(min))of−71.70 dB at 2.78 mm and Radar Cross section value of−53.23 dB m^(2).More importantly,the acquired results demonstrated that CoNi@NC-CoNi@CNTs MCNCs presented excellent photothermal,antimicrobial and anti-corrosion properties owing to their hierarchical cubic sea urchin-like yolk–shell structure,highlighting their potential multifunctional applications.It could be seen that this finding not only presented a generalizable route to produce hierarchical cubic sea urchin-like yolk–shell magnetic NC-CNTs-based mixed-dimensional MCNCs,but also provided an effective strategy to develop multifunctional MCNCs and improve their environmental adaptabilities.展开更多
The miniaturization and high-power density of electronic devices presents new challenges in thermal management.The precise control of microstructure arrangement,particularly in boron nitride nanosheets(BNNS),is essent...The miniaturization and high-power density of electronic devices presents new challenges in thermal management.The precise control of microstructure arrangement,particularly in boron nitride nanosheets(BNNS),is essential for achieving efficient heat dissipation in highly thermally conductive composites within electrically insulating package.In this work,manganese ferrite was hydrothermally synthesized on BNNS,creating a layered structure in a magnetically responsive nanohybrid material named BNNS@M.This material was then integrated into a waterborne polyurethane(WPU)solution and shaped under a magnetic field to produce thermally conductive film.By altering the magnetic field direction,the mi-crostructure orientation of BNNS@M was controlled,resulting in anisotropic thermally conductive com-posite films with horizontal and vertical orientations.Specifically,under a vertical magnetic field,the film 30-Ve-BNNS@WPU,containing 30 wt.%BNNS@M,achieved a through-plane thermal conductivity of 8.5 W m^(−1)K^(−1)and an in-plane thermal conductivity of 1.8 W m^(−1)K^(−1),showcasing significant anisotropic thermal conductivity.Meanwhile,these films demonstrated excellent thermal stability,mechanical per-formance,and flame retardancy.Furthermore,employing Foygel’s theory elucidated the impact of filler arrangement on thermal conductivity mechanisms and the actual application of 5 G device chips and LED lamps emphasizing the potential of these thermally conductive films in thermal management appli-cations.This investigation contributes valuable design concepts and foundations for the development of anisotropic thermally conductive composites suitable for electron thermal management.展开更多
A series of divinylphenyl-acryloyl chloride copolymers(PDVB-co-PACl)is synthesized via atom transfer radical polymerization employing tert-butyl acrylate and divinylbenzene as monomers.PDVB-co-PACl is utilized to graf...A series of divinylphenyl-acryloyl chloride copolymers(PDVB-co-PACl)is synthesized via atom transfer radical polymerization employing tert-butyl acrylate and divinylbenzene as monomers.PDVB-co-PACl is utilized to graft on the surface of spherical aluminum nitride(AlN)to prepare functionalized AlN(AlN@PDVB-co-PACl).Polymethylhydrosiloxane(PMHS)is then used as the matrix to prepare thermally conductive AlN@PDVB-co-PACl/PMHS composites with AlN@PDVB-co-PACl as fillers through blending and curing.The grafting of PDVB-co-PACl synchronously enhances the hydrolysis resistance of AlN and its interfacial compatibility with PMHS matrix.When the molecular weight of PDVB-co-PACl is 5100 g mol^(-1)and the grafting density is 0.8 wt%,the composites containing 75 wt%of AlN@PDVB-co-PACl exhibit the optimal comprehensive performance.The thermal conductivity(λ)of the composite is 1.14 W m^(-1)K^(-1),which enhances by 20%and 420%compared to theλof simply physically blended AlN/PMHS composite and pure PMHS,respectively.Meanwhile,AlN@PDVB-co-PACl/PMHS composites display remarkable hydrothermal aging resistance by retaining 99.1%of itsλafter soaking in 90°C deionized water for 80 h,whereas theλof the blended AlN/PMHS composites decreases sharply to 93.7%.展开更多
Low erosion high-energy propellant is one of the research directions to extend the weapon’s life and improve the weapon’s capability.In this study,energetic propellants containing different corrosion inhibitors were...Low erosion high-energy propellant is one of the research directions to extend the weapon’s life and improve the weapon’s capability.In this study,energetic propellants containing different corrosion inhibitors were designed and prepared.Close bomb tests and semi-confined bomb experiments were used to investigate the burning and erosion properties of the propellants.The mechanism of erosion-reducing of titanium dioxide(titania,TiO_(2)),talc,and octaphenylsilsesquioxane(OPS)on the propellant was comparatively analyzed.The results show that OPS has the lowest burning rate and the longest burning time,and a minimized loss of fire force,with the best effect of explosion heat reduction.The erosion reduction efficiency of OPS is twice that of TiO_(2) and talc.The mechanism analysis shows that the decomposition and heat absorption of OPS can effectively reduce the thermal erosion effect and carbon erosion,and the gas produced can reduce the loss of chamber pressure and form a uniformly distributed nano-SiO_(2) protective layer.This solid-state high-efficiency organosilicon erosion inhibitor is an important guide for designing high-energy low-erosion gun propellants.展开更多
Polysiloxane-based thermally conductive composites are essential for electronic heat management,but they face challenges such as limited thermal conductivity enhancement and low improvement efficiency.In this work,a n...Polysiloxane-based thermally conductive composites are essential for electronic heat management,but they face challenges such as limited thermal conductivity enhancement and low improvement efficiency.In this work,a novel liquid crystal crosslinker(LCC)based on biphenyl liquid crystal moieties was synthe-sized.Liquid crystal polydimethylsiloxane(LC-PDMS)with intrinsic highλwas prepared by crosslinking vinyl/methyl-hydrogen functionalized PDMS by LCC at its liquid crystal transition temperature,and boron nitride nanosheets(BNNs)with different particle sizes were used to prepare BNNs/LC-PDMS composites.When the mass ratio of LCC to vinyl-terminated PDMS is 2:1,the LC-PDMS exhibitsa well-ordered liquid crystal phase,and itsλ_(Ⅱ)reachesthe maximum value of 0.34 W(m K)^(-1),approximately 1.7 times that of general PDMS(0.20 W(m K)^(-1)).Theλ_(Ⅱ)of BNNs/LC-PDMS composites increases with the addition of BNNs,and when the mass fraction of BNNs reaches 30 wt%,with a 1:9 mass ratio of small BNNs(1μm)to large BNNs(10μm),the composite achieves the highestλ_(Ⅱ)of 12.50 W(m K)^(-1),a 68.5%increase com-pared to BNNs/PMDS composites containing the same amount of BNNs(7.42 W(m K)^(-1)).Additionally,BNNs/LC-PDMS composites also demonstrate excellent electrical insulation properties and low density,making them promising candidates for applications in highly integrated electronics fields.展开更多
Phase change materials(PCMs)offer a promising solution to address the challenges posed by intermittency and fluctuations in solar thermal utilization.However,for organic solid-liquid PCMs,issues such as leakage,low th...Phase change materials(PCMs)offer a promising solution to address the challenges posed by intermittency and fluctuations in solar thermal utilization.However,for organic solid-liquid PCMs,issues such as leakage,low thermal conductivity,lack of efficient solar-thermal media,and flamma-bility have constrained their broad applications.Herein,we present an innova-tive class of versatile composite phase change materials(CPCMs)developed through a facile and environmentally friendly synthesis approach,leveraging the inherent anisotropy and unidirectional porosity of wood aerogel(nanowood)to support polyethylene glycol(PEG).The wood modification process involves the incorporation of phytic acid(PA)and MXene hybrid structure through an evaporation-induced assembly method,which could impart non-leaking PEG filling while concurrently facilitating thermal conduction,light absorption,and flame-retardant.Consequently,the as-prepared wood-based CPCMs showcase enhanced thermal conductivity(0.82 W m^(-1)K^(-1),about 4.6 times than PEG)as well as high latent heat of 135.5 kJ kg^(-1)(91.5%encapsula-tion)with thermal durability and stability throughout at least 200 heating and cooling cycles,featuring dramatic solar-thermal conversion efficiency up to 98.58%.In addition,with the synergistic effect of phytic acid and MXene,the flame-retardant performance of the CPCMs has been significantly enhanced,showing a self-extinguishing behavior.Moreover,the excellent electromagnetic shielding of 44.45 dB was endowed to the CPCMs,relieving contemporary health hazards associated with electromagnetic waves.Overall,we capitalize on the exquisite wood cell structure with unidirectional transport inherent in the development of multifunctional CPCMs,showcasing the operational principle through a proof-of-concept prototype system.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
With the rapid development of 5G technology and the interconnection of industrial production,electro-magnetic pollution has become a serious problem.Achieving lightweight and controllable loads of ab-sorbers while obt...With the rapid development of 5G technology and the interconnection of industrial production,electro-magnetic pollution has become a serious problem.Achieving lightweight and controllable loads of ab-sorbers while obtaining corrosion-resistant absorbers with high electromagnetic response properties is still considered a huge challenge.In this work,carbon fiber with a multichannel hollow structure is ob-tained by PAN/PS hybrid electrospinning and subsequent high-temperature roasting process.The spatial structure inside the carbon fiber plays an active role in optimizing the impedance matching character-istics of the absorber.In addition,bimetallic metal-organic frameworks(MOFs)derivatives are obtained by a precisely controlled ion exchange as well as a high-temperature gas-phase selenization process.The resulting introduction of a non-homogeneous interface induces interfacial polarization and improves the absorption behavior of the absorber.The analysis of the experimental results shows that the electro-magnetic wave(EMW)absorption performance can be effectively enhanced due to the mechanisms of interface polarization and dipole polarization.The prepared NiSe/ZnSe/MHCFs composite can obtain ex-cellent EMW absorption properties in C,X,and Ku bands by adjusting the thickness.Structural design and component modulation play a crucial role in realizing the strong absorption and wide bandwidth of the absorber.Radar cross-section calculations indicate that NiSe/ZnSe/MHCFs have tremendous potential in practical military stealth technology.And the prepared composite coating can provide periodic corrosion resistance to Q235 steel sheet when dealing with complex and extreme environments.展开更多
Multiple hetero-interfaces would strengthen interfacial polarization and boost electromagnetic wave absorption,but still remain the formidable challenges in decreasing filler loadings.Herein,sandwich NC@Co/NC@MnO_(2)c...Multiple hetero-interfaces would strengthen interfacial polarization and boost electromagnetic wave absorption,but still remain the formidable challenges in decreasing filler loadings.Herein,sandwich NC@Co/NC@MnO_(2)composites with hollow cavity,multiple hetero-interfaces,and hierarchical structures have been fabricated via the cooperative processes of self-sacrifice strategy and sequential hydrothermal reaction.In the sandwich composites,middle magnetic components(Co/NC)are wrapped by inner N-doped carbon(NC)matrix and outer hierarchical MnO_(2)nanosheets.Importantly,hollow engineering of sandwich composites with multiple hetero-interfaces greatly facilitates the enhancement of absorption bandwidth without sacrificing the absorption intensity.The maximum reflection loss of sandwich NC@Co/NC@MnO_(2)composites reaches-44.8 dB at 2.5 mm and the effective bandwidths is achieved as wide as 9.6 GHz at 2.3 mm.These results provide us a new insight into preparing efficient electromagnetic wave absorbers by interface engineering and hollow construction.展开更多
The control of undesired electromagnetic radiation in S-and C-band spectra requires novel microwave absorbing materials(MAMs)having high microwave attenuation capability together with optimal impedance matching.CNTs a...The control of undesired electromagnetic radiation in S-and C-band spectra requires novel microwave absorbing materials(MAMs)having high microwave attenuation capability together with optimal impedance matching.CNTs are conformally coated onto the surface of one-dimensional FeCo-based magnetic microchains via electrostatic self-assembly,and then the magnetic inclusions are collectively oriented in matrices by applying an external magnetic field.The proper incorporation of CNTs with magnetic microchains demonstrates a feasible pathway for effectively absorbing microwaves in the S and C band.MAMs consisting of oriented microchains have anisotropic complex permittivity,of which the real part ranges from 6.1 to 30.4 at 2 GHz.When the electric field is parallel to microchains,the 5-mm-thick MAM has an effective absorbing bandwidth(EAB)in the range of 2.3 to 2.9 GHz,and reduces the radar cross section to be lower than-15.9 dB m^(2) from the vertical to the glancing incidence.When the magnetic field is parallel to microchains,the MAM adsorbs C-band microwaves with an EAB of 1.5 GHz,and achieves maximal reflection loss of-46.4 dB.The collective orientation of shape-anisotropic magnetic materials,in addition to the composition and microstructure,is a new variable for the design of effective MAMs.展开更多
High integration,high frequency,high power,and miniaturization of electrical and electronic devices have raised higher demands for epoxy resins with both high intrinsic thermal conductivity and low dielectric properti...High integration,high frequency,high power,and miniaturization of electrical and electronic devices have raised higher demands for epoxy resins with both high intrinsic thermal conductivity and low dielectric properties.Herein,a series of linear fluorinated epoxy copolymers(poly(PFS-co-GMA))were synthesized via reversible addition-fragmentation chain transfer(RAFT)polymerization.Poly(PFS-co-GMA)was introduced into the cross-linked network of a biphenyl-based liquid crystalline epoxy(LCE)by forming a semi-interpenetrating polymer network(semi-IPN).The prepared liquid crystalline epoxy resins(LCERs)simultaneously exhibited high intrinsic thermal conductivity and low dielectric properties.The molar mass and mass fraction of poly(PFS-co-GMA)were found to have a profound effect on the thermal conductivity and dielectric performance of LCERs.For instance,poly(PFS-co-GMA)with the number average molar mass(M_(n))of 4300 and 7800 g/mol showed a decreasing effect on the thermal conductivity(λ)of LCERs whereas the polymer with M_(n)of 10500 g/mol enhanced theλ.The intrinsicλof LCERs increased to a remarkable highest value of 0.40 W/(m K),which was twice that of conventional epoxy resin(0.20 W/(m·K)).In addition,introducing poly(PFS-co-GMA)would significantly decrease the dielectric constant(ε)and dielectric loss tangent(tanδ)of LCERs from 3.44 and 0.035 to 2.49 and 0.001 at 1 MHz,respectively.Notably,theεand tanδcould remain relatively stable over a wide range of frequencies and temperatures up to 120℃.Additionally,the semi-IPN structure enhanced the hardness,electrical insulation,and hydrophobicity of LCERs.展开更多
The directional arrangement of two-dimensional thermally conductive fillers can fully exploit their anisotropic advantages and form efficient thermal conduction paths within the composites,thereby significantly improv...The directional arrangement of two-dimensional thermally conductive fillers can fully exploit their anisotropic advantages and form efficient thermal conduction paths within the composites,thereby significantly improving their thermal conduction efficiency.In this study,“point-surface”hetero-structured boron nitride nanosheets(BNNS)@Ni thermally conductive fillers with magnetic response are synthesized via in-situ growth and high-temperature carbonization.The H-BNNS@Ni/PDMS(BNNS@Ni horizontally arranged in the polydimethylsiloxane(PDMS)matrix)thermally conductive composites are fabricated via magnetic field orientation.When the mass ratio of BNNS to Ni in BNNS@Ni is 8:1 and the mass fraction of BNNS@Ni is 50 wt.%,the in-plane thermal conductivity(λ_(∥))of H-BNNS@Ni/PDMS thermally conductive composites reaches 5.50 W/(m·K),which is 27.8 times higher than that of pure PDMS(0.19 W/(m·K)),and is also significantly higher than that of R-BNNS@Ni/PDMS(BNNS@Ni randomly distributed in the PDMS matrix)thermally conductive composites(4.76 W/(m·K))with the same mass fraction of BNNS@Ni.H-BNNS@Ni/PDMS thermally conductive composites can reduce the operating temperature at full power by 19.2℃compared to pure PDMS when used for CPU cooling.Meanwhile,H-BNNS@Ni/PDMS thermally conductive composites also exhibit excellent thermal resistance,photothermal conversion performance,and hydrophobicity.展开更多
Heterostructure fillers are crucial for enhancing the electromagnetic interference(EMI)shielding performance of composites,and the core lies in the regulation of their morphology.Inspired by the radial structures on m...Heterostructure fillers are crucial for enhancing the electromagnetic interference(EMI)shielding performance of composites,and the core lies in the regulation of their morphology.Inspired by the radial structures on marimo surfaces during growth,we propose a bioinspired heterostructure assembly strategy to fabricate novel marimo-like hollow spherical reduced graphene oxide(hs-rGO)@nickel-catalyzed nitrogen-doped carbon nanotubes(Ni-NCNTs)and their corresponding polyimide aerogels.Benefiting from the synergistic design of multilevel porous architectures formed by the hollow microspheres in combination with the aerogel matrix,as well as radially aligned Ni-NCNTs epitaxially grown on hs-rGO surfaces,the resulting aerogels exhibit exceptional EMI shielding effectiveness,reaching up to 68 dB.Finite element simulations further elucidate the shielding mechanisms.Additionally,these aerogels exhibit rapid,durable pressure-sensing performance due to their excellent resilience and conductivity.The multifunctional combination of high-efficiency EMI shielding and mechanical sensing highlights their promising potential in next-generation intelligent electronics,aerospace systems,and advanced communication technologies.展开更多
基金the support from the National Natural Science Foundation of China(52473083,52373089,52403085)Natural Science Basic Research Program of Shaanxi(2024JC-TBZC-04)+2 种基金the Innovation Capability Support Program of Shaanxi(2024RS-CXTD-57)Natural Science Basic Research Plan in Shaanxi Province of China(2024JC-YBMS-279)Natural Science Foundation of Chongqing,China(2023NSCQMSX2547)
文摘With the miniaturization and high-frequency evolution of antennas in 5G/6G communications,aerospace,and transportation,polymer composite papers integrating superior wave-transparent performance and thermal conductivity for radar antenna systems are urgently needed.Herein,a down-top strategy was employed to synthesize poly(p-phenylene benzobisoxazole)precursor nanofibers(prePNF).The prePNF was then uniformly mixed with fluorinated graphene(FG)to fabricate FG/PNF composite papers through consecutively suction filtration,hot-pressing,and thermal annealing.The hydroxyl and amino groups in prePNF enhanced the stability of FG/prePNF dispersion,while the increasedπ-πinteractions between PNF and FG after annealing improved their compatibility.The preparation time and cost of PNF paper was significantly reduced when applying this strategy,which enabled its large-scale production.Furthermore,the prepared FG/PNF composite papers exhibited excellent wave-transparent performance and thermal conductivity.When the mass fraction of FG was 40 wt%,the FG/PNF composite paper prepared via the down-top strategy achieved the wave-transparent coefficient(|T|2)of 96.3%under 10 GHz,in-plane thermal conductivity(λ_(∥))of 7.13 W m^(−1)K^(−1),and through-plane thermal conductivity(λ_(⊥))of 0.67 W m^(−1)K^(−1),outperforming FG/PNF composite paper prepared by the top-down strategy(|T|2=95.9%,λ_(∥)=5.52 W m^(−1)K^(−1),λ_(⊥)=0.52 W m^(−1)K^(−1))and pure PNF paper(|T|2=94.7%,λ_(∥)=3.04 W m^(−1)K^(−1),λ_(⊥)=0.24 W m^(−1)K^(−1)).Meanwhile,FG/PNF composite paper(with 40 wt%FG)through the down-top strategy also demonstrated outstanding mechanical properties with tensile strength and toughness reaching 197.4 MPa and 11.6 MJ m^(−3),respectively.
基金financially supported by the National Natural Science Foundation of China(No.52377026 and No.52301192)Taishan Scholars and Young Experts Program of Shandong Province(No.tsqn202103057)+4 种基金Postdoctoral Fellowship Program of CPSF under Grant Number(No.GZB20240327)Shandong Postdoctoral Science Foundation(No.SDCXZG-202400275)Qingdao Postdoctoral Application Research Project(No.QDBSH20240102023)China Postdoctoral Science Foundation(No.2024M751563)the Qingchuang Talents Induction Program of Shandong Higher Education Institution(Research and Innovation Team of Structural-Functional Polymer Composites).
文摘Currently,the demand for electromagnetic wave(EMW)absorbing materials with specific functions and capable of withstanding harsh environments is becoming increasingly urgent.Multi-component interface engineering is considered an effective means to achieve high-efficiency EMW absorption.However,interface modulation engineering has not been fully discussed and has great potential in the field of EMW absorption.In this study,multi-component tin compound fiber composites based on carbon fiber(CF)substrate were prepared by electrospinning,hydrothermal synthesis,and high-temperature thermal reduction.By utilizing the different properties of different substances,rich heterogeneous interfaces are constructed.This effectively promotes charge transfer and enhances interfacial polarization and conduction loss.The prepared SnS/SnS_(2)/SnO_(2)/CF composites with abundant heterogeneous interfaces have and exhibit excellent EMW absorption properties at a loading of 50 wt%in epoxy resin.The minimum reflection loss(RL)is−46.74 dB and the maximum effective absorption bandwidth is 5.28 GHz.Moreover,SnS/SnS_(2)/SnO_(2)/CF epoxy composite coatings exhibited long-term corrosion resistance on Q235 steel surfaces.Therefore,this study provides an effective strategy for the design of high-efficiency EMW absorbing materials in complex and harsh environments.
基金financially supported by the National Natural Science Foundation of China(52373271)Science,Technology and Innovation Commission of Shenzhen Municipality under Grant(KCXFZ20201221173004012)+1 种基金National Key Research and Development Program of Shaanxi Province(No.2023-YBNY-271)Open Testing Foundation of the Analytical&Testing Center of Northwestern Polytechnical University(2023T019).
文摘Gradient magnetic heterointerfaces have injected infinite vitality in optimizing impedance matching,adjusting dielectric/magnetic resonance and promoting electromagnetic(EM)wave absorption,but still exist a significant challenging in regulating local phase evolution.Herein,accordion-shaped Co/Co_(3)O_(4)@N-doped carbon nanosheets(Co/Co_(3)O_(4)@NC)with gradient magnetic heterointerfaces have been fabricated via the cooperative high-temperature carbonization and lowtemperature oxidation process.The results indicate that the surface epitaxial growth of crystal Co_(3)O_(4) domains on local Co nanoparticles realizes the adjustment of magnetic-heteroatomic components,which are beneficial for optimizing impedance matching and interfacial polarization.Moreover,gradient magnetic heterointerfaces simultaneously realize magnetic coupling,and long-range magnetic diffraction.Specifically,the synthesized Co/Co_(3)O_(4)@NC absorbents display the strong electromagnetic wave attenuation capability of−53.5 dB at a thickness of 3.0 mm with an effective absorption bandwidth of 5.36 GHz,both are superior to those of single magnetic domains embedded in carbon matrix.This design concept provides us an inspiration in optimizing interfacial polarization,regulating magnetic coupling and promoting electromagnetic wave absorption.
基金We acknowledge the Henan Young Backbone Teachers Foundation(No.2021GGJS135)。
文摘With the continuous development of electronic devices and the information industry towards miniaturization,integration,and high-power consumption,the using of electronic devices will inevitably generate and accumulate heat,which will cause local high temperatures and will seriously reduce their performance,reliability,and lifetime.Therefore,having efficient heat-conducting functional materials is crucial to the normal and stable operation of electrical equipment and microelectronic products.In view of the excellent comprehensive performance of polymer-based thermally conductive materials(including intrinsic polymers and filler-filled polymer-based composites),it has shown great advantages in thermal management applications.In this review,the research status of preparing polymer-based thermally conductive composites and effective strategies to improve their thermal conductivity(TC)are reviewed.Compared with the higher cost and technical support with adjusting the molecular chain structure and cross-linking mode to improve the intrinsic TC of the polymer,introducing suitable fillers into the polymer to build a thermally conductive network or oriented structure can simply and efficiently improve the overall TC.Typical applications of polymer-based composites were discussed with detailed examples in the field of electronic packaging.Challenges and possible solutions to solve the issues are discussed together with the perspectives.This study provides guidance for the future development of polymer-based thermally conductive composites.
基金support from the National Natural Science Foundation of China(22268025,52473083,and 22475176)Key Research and Development Program of Yunnan Province(202403AP140036)+2 种基金Natural Science Basic Research Program of Shaanxi(2024JC-TBZC-04)Applied Basic Research Program of Yunnan Province(202201AT070115 and 202201BE070001-031)supported by the Innovation Capability Support Program of Shaanxi(2024RS-CXTD-57).
文摘The microstructure design for thermal conduction pathways in polymeric electrical encapsulation materials is essential to meet the stringent requirements for efficient thermal management and thermal runaway safety in modern electronic devices.Hence,a composite with three-dimensional network(Ho/U-BNNS/WPU)is developed by simultaneously incorporating magnetically modified boron nitride nanosheets(M@BNNS)and non-magnetic organo-grafted BNNS(U-BNNS)into waterborne polyurethane(WPU)to synchronous molding under a horizontal magnetic field.The results indicate that the continuous in-plane pathways formed by M@BNNS aligned along the magnetic field direction,combined with the bridging structure established by U-BNNS,enable Ho/U-BNNS/WPU to exhibit exceptional in-plane(λ//)and through-plane thermal conductivities(λ_(⊥)).In particular,with the addition of 30 wt%M@BNNS and 5 wt%U-BNNS,theλ//andλ_(⊥)of composites reach 11.47 and 2.88 W m^(-1) K^(-1),respectively,which representing a 194.2%improvement inλ_(⊥)compared to the composites with a single orientation of M@BNNS.Meanwhile,Ho/U-BNNS/WPU exhibits distinguished thermal management capabilities as thermal interface materials for LED and chips.The composites also demonstrate excellent flame retardancy,with a peak heat release and total heat release reduced by 58.9%and 36.9%,respectively,compared to WPU.Thus,this work offers new insights into the thermally conductive structural design and efficient flame-retardant systems of polymer composites,presenting broad application potential in electronic packaging fields.
基金supported by the PhD Start-up Fund of the Science and Technology Department of Liaoning Province(No.2022-BS-306)the General Cultivation Scientific Research Project of Bohai University(No.0522xn058)the PhD Research Startup Foundation of Bohai University(No.0521bs021).
文摘The preparation of electromagnetic(EM)wave absorption materials provided with the characteristics of thin matching thickness,broad bandwidth,and mighty absorption intensity is an efficient solution to current EM pollution.Herein,Graphene nanosheets(GN)were firstly fabricated via a facile high-energy ball milling method,subsequently high-purity 1T-MoS_(2) petals were uniformly anchored on the surface of GN to prepare 1T-MoS_(2)@GN nanocomposites.Plentiful multiple reflection and scattering of EM waves in a distinctive multidimensional structure formed by GN and 1T-MoS_(2),copious polarization loss consisting of interfacial polarization loss and dipolar polarization loss severally derived from multitudinous heterointerfaces and profuse electric dipoles in 1T-MoS_(2)@GN,and mighty conduction loss originated from plentiful induced current in 1T-MoS_(2)@GN generated via the migration of massive electrons,all of which endowed 1T-MoS_(2)@GN nanocomposites with exceptional EM wave absorption performances.The minimum reflection loss(RLmin)of 1T-MoS_(2)@GN reached–50.14 dB at a thickness of only 2.10 mm,and the effective absorption bandwidth(EAB)was up to 6.72 GHz at an ultra-thin matching thickness of 1.84 mm.Moreover,the radar scattering cross section(RCS)reduction value of 36.18 dB m2 at 0°could be achieved as well,which ulteriorly validated the tremendous potential of 1T-MoS_(2)@GN nanocomposites in practical applications.
基金financially supported by the National Natural Science Foundation of China(Nos.52303090,52403132,52403112,52473083)the Natural Science Basic Research Plan in Shaanxi Province of China(No.2023-JC-QN-0168,2024JC-TBZC-04)+6 种基金the Innovation Capability Support Plan of Shaanxi Province(No.2024ZC-KJXX-022)the Shaanxi Province Key Research and Development Plan Project(No.2023-YBGY-461)the Innovation Capability Support Program of Shaanxi(No.2024RS-CXTD-57)the Natural Science Foundation of Chongqing,China(No.2023NSCQ-MSX2547)the Youth Talent Promotion Project of Shaanxi Science and Technology Association(No.20240426)The Special Scientific Research Plan of Education Department of Shaanxi Province(No.23JK0376)the authors would also like to thank Shiyaniia lab for the sup-port of SEM and XPS tests.
文摘Flexible multifunctional polymer-based electromagnetic interference(EMI)shielding composite films play a pivotal role in 5 G communication technology,smart wearables,automotive electronics,and aerospace.In this work,(Ti_(3)C_(2)T_(x) MXene/cellulose nanofibers(CNF)-(hydroxy‑functionalized BNNS(BNNS-OH)/CNF)composite films(TBCF)with Janus structure are prepared via vacuum-assisted filtration of BNNS-OH/CNF and Ti_(3)C_(2)T_(x)/CNF suspension by one after another.Then ionic bonding-strengthened TBCF(ITBCF)is obtained by Ca^(2+)ion infiltration and cold-pressing technique.The Janus structure endows ITBCF with the unique“conductive on one side and insulating on the other”property.When the mass ratio of Ti_(3)C_(2)T_(x) and BNNS is 1:1 and the total mass fraction is 70 wt.%,the electrical conductivity(σ)of the Ti_(3)C_(2)T_(x)/CNF side of ITBCF reaches 166.7 S/cm,while the surface resistivity of the BNNS-OH/CNF side is as high as 304 MΩ.After Ca^(2+)ion infiltration,the mechanical properties of ITBCF are significantly enhanced.The tensile strength and modulus of ITBCF are 73.5 MPa and 15.6 GPa,which are increased by 75.9%and 46.2%compared with those of TBCF,respectively.Moreover,ITBCF exhibits outstanding EMI shielding effectiveness(SE)of 57 dB and thermal conductivity(λ)of 9.49 W/(m K).In addition,ITBCF also presents excellent photothermal and photoelectric energy conversion performance.Under simulated solar irradiation with a power density of 120 mW/cm^(2),the surface stabilization temperature reaches up to 65.3°C and the maximum steady state voltage reaches up to 58.2 mV.
基金support from the National Natural Science Foundation of China(U21A2093)Shaanxi Province Key Research and Development Plan Project(2023-YBGY-461)+4 种基金Platform of Science and Technology and Talent Team Plan of Guizhou province(GCC[2023]007)Guizhou Provincial Basic Research Program(Natural Science)(No.ZK[2025]Key 086)Fok Ying Tung Education Foundation(171095)financial support,Innovation Capability Support Program of Shaanxi(2024RS-CXTD-57)Innovation Foundation for Doctor Dissertation of Northwestern Polytechnical University(CX2024094)。
文摘The previous studies mainly focused on improving microwave absorbing(MA)performances of MA materials.Even so,these designed MA materials were very difficult to be employed in complex and changing environments owing to their single-functionalities.Herein,a combined Prussian blue analogues derived and catalytical chemical vapor deposition strategy was proposed to produce hierarchical cubic sea urchin-like yolk–shell CoNi@Ndoped carbon(NC)-CoNi@carbon nanotubes(CNTs)mixed-dimensional multicomponent nanocomposites(MCNCs),which were composed of zerodimensional CoNi nanoparticles,three-dimensional NC nanocubes and onedimensional CNTs.Because of good impedance matching and attenuation characteristics,the designed CoNi@NC-CoNi@CNTs mixed-dimensional MCNCs exhibited excellent MA performances,which achieved a minimum reflection loss(RL_(min))of−71.70 dB at 2.78 mm and Radar Cross section value of−53.23 dB m^(2).More importantly,the acquired results demonstrated that CoNi@NC-CoNi@CNTs MCNCs presented excellent photothermal,antimicrobial and anti-corrosion properties owing to their hierarchical cubic sea urchin-like yolk–shell structure,highlighting their potential multifunctional applications.It could be seen that this finding not only presented a generalizable route to produce hierarchical cubic sea urchin-like yolk–shell magnetic NC-CNTs-based mixed-dimensional MCNCs,but also provided an effective strategy to develop multifunctional MCNCs and improve their environmental adaptabilities.
基金supported by the National Natural Science Foundation of China(No.22268025)the Guangdong Basic and Applied Basic Research Foundation(No.2023A1515011985)the Applied Basic Research Program of Yunnan Province(Nos.202201AT070115,202201BE070001–031).
文摘The miniaturization and high-power density of electronic devices presents new challenges in thermal management.The precise control of microstructure arrangement,particularly in boron nitride nanosheets(BNNS),is essential for achieving efficient heat dissipation in highly thermally conductive composites within electrically insulating package.In this work,manganese ferrite was hydrothermally synthesized on BNNS,creating a layered structure in a magnetically responsive nanohybrid material named BNNS@M.This material was then integrated into a waterborne polyurethane(WPU)solution and shaped under a magnetic field to produce thermally conductive film.By altering the magnetic field direction,the mi-crostructure orientation of BNNS@M was controlled,resulting in anisotropic thermally conductive com-posite films with horizontal and vertical orientations.Specifically,under a vertical magnetic field,the film 30-Ve-BNNS@WPU,containing 30 wt.%BNNS@M,achieved a through-plane thermal conductivity of 8.5 W m^(−1)K^(−1)and an in-plane thermal conductivity of 1.8 W m^(−1)K^(−1),showcasing significant anisotropic thermal conductivity.Meanwhile,these films demonstrated excellent thermal stability,mechanical per-formance,and flame retardancy.Furthermore,employing Foygel’s theory elucidated the impact of filler arrangement on thermal conductivity mechanisms and the actual application of 5 G device chips and LED lamps emphasizing the potential of these thermally conductive films in thermal management appli-cations.This investigation contributes valuable design concepts and foundations for the development of anisotropic thermally conductive composites suitable for electron thermal management.
基金support from the National Natural Science Foundation of China(52473083 and 52403112)the Technological Base Scientific Research Projects(Highly Thermal conductivity Nonmetal Materials),the Natural Science Basic Research Program of Shaanxi(2024JC-TBZC-04)+4 种基金the Shaanxi Province Key Research and Development Plan Project(2023-YBGY-461)the Innovation Capability Support Program of Shaanxi(2024RS-CXTD-57),the Natural Science Foundation of Chongqing,China(2023NSCQ-MSX2547)the Fundamental Research Funds for the Central Universities(D5000240077 and D5000240067)the Innovation Foundation for Doctor Dissertation of Northwestern Polytechnical University(CX2024094)the Analytical&Testing Center of Northwestern Polytechnical University for FT-IR,XRD and TEM tests performed in this work.
文摘A series of divinylphenyl-acryloyl chloride copolymers(PDVB-co-PACl)is synthesized via atom transfer radical polymerization employing tert-butyl acrylate and divinylbenzene as monomers.PDVB-co-PACl is utilized to graft on the surface of spherical aluminum nitride(AlN)to prepare functionalized AlN(AlN@PDVB-co-PACl).Polymethylhydrosiloxane(PMHS)is then used as the matrix to prepare thermally conductive AlN@PDVB-co-PACl/PMHS composites with AlN@PDVB-co-PACl as fillers through blending and curing.The grafting of PDVB-co-PACl synchronously enhances the hydrolysis resistance of AlN and its interfacial compatibility with PMHS matrix.When the molecular weight of PDVB-co-PACl is 5100 g mol^(-1)and the grafting density is 0.8 wt%,the composites containing 75 wt%of AlN@PDVB-co-PACl exhibit the optimal comprehensive performance.The thermal conductivity(λ)of the composite is 1.14 W m^(-1)K^(-1),which enhances by 20%and 420%compared to theλof simply physically blended AlN/PMHS composite and pure PMHS,respectively.Meanwhile,AlN@PDVB-co-PACl/PMHS composites display remarkable hydrothermal aging resistance by retaining 99.1%of itsλafter soaking in 90°C deionized water for 80 h,whereas theλof the blended AlN/PMHS composites decreases sharply to 93.7%.
基金supported by the China Postdoc-toral Science Foundation(No.2023M732495)the Shanxi Provincial Basic Research Program(Nos.202103021223180 and 202203021221120)the Deanship of Scientific Research at Northern Border University,Arar,KSA for funding this research work through the project number“NBU-FPEJ-2024-1261-02”.
文摘Low erosion high-energy propellant is one of the research directions to extend the weapon’s life and improve the weapon’s capability.In this study,energetic propellants containing different corrosion inhibitors were designed and prepared.Close bomb tests and semi-confined bomb experiments were used to investigate the burning and erosion properties of the propellants.The mechanism of erosion-reducing of titanium dioxide(titania,TiO_(2)),talc,and octaphenylsilsesquioxane(OPS)on the propellant was comparatively analyzed.The results show that OPS has the lowest burning rate and the longest burning time,and a minimized loss of fire force,with the best effect of explosion heat reduction.The erosion reduction efficiency of OPS is twice that of TiO_(2) and talc.The mechanism analysis shows that the decomposition and heat absorption of OPS can effectively reduce the thermal erosion effect and carbon erosion,and the gas produced can reduce the loss of chamber pressure and form a uniformly distributed nano-SiO_(2) protective layer.This solid-state high-efficiency organosilicon erosion inhibitor is an important guide for designing high-energy low-erosion gun propellants.
基金support from the National Nat-ural Science Foundation of China(No.52403114)the Technolog-ical Base Scientific Research Projects(Highly Thermally Conduc-tive Nonmetal Materials)+3 种基金the Innovation Capability Support Pro-gram of Shaanxi(No.2024RS-CXTD-57)the Natural Science Foun-dation of Chongqing(No.2023NSCQ-MSX2547)the Fundamental Research Funds for the Central Universities(No.D5000240077)the Shaanxi Coal Chemical Industry Technology Research In-stitute Co.,Ltd.(No.2023YJY-Y-HZ-XS-NX003).
文摘Polysiloxane-based thermally conductive composites are essential for electronic heat management,but they face challenges such as limited thermal conductivity enhancement and low improvement efficiency.In this work,a novel liquid crystal crosslinker(LCC)based on biphenyl liquid crystal moieties was synthe-sized.Liquid crystal polydimethylsiloxane(LC-PDMS)with intrinsic highλwas prepared by crosslinking vinyl/methyl-hydrogen functionalized PDMS by LCC at its liquid crystal transition temperature,and boron nitride nanosheets(BNNs)with different particle sizes were used to prepare BNNs/LC-PDMS composites.When the mass ratio of LCC to vinyl-terminated PDMS is 2:1,the LC-PDMS exhibitsa well-ordered liquid crystal phase,and itsλ_(Ⅱ)reachesthe maximum value of 0.34 W(m K)^(-1),approximately 1.7 times that of general PDMS(0.20 W(m K)^(-1)).Theλ_(Ⅱ)of BNNs/LC-PDMS composites increases with the addition of BNNs,and when the mass fraction of BNNs reaches 30 wt%,with a 1:9 mass ratio of small BNNs(1μm)to large BNNs(10μm),the composite achieves the highestλ_(Ⅱ)of 12.50 W(m K)^(-1),a 68.5%increase com-pared to BNNs/PMDS composites containing the same amount of BNNs(7.42 W(m K)^(-1)).Additionally,BNNs/LC-PDMS composites also demonstrate excellent electrical insulation properties and low density,making them promising candidates for applications in highly integrated electronics fields.
基金funding from the National Natural Science Foundation of China(No.22268025)China Postdoctoral Science Foundation(NO.2022MD713757)+2 种基金Yunnan Provincial Postdoctoral Science Foundation(NO.34Y2022)Yunnan Province Joint Special Project for Enterprise Fundamental Research and Applied Basic Research(No.202101BC070001-016)Guangdong Basic and Applied Basic Research Foundation(No.2023A1515011985).
文摘Phase change materials(PCMs)offer a promising solution to address the challenges posed by intermittency and fluctuations in solar thermal utilization.However,for organic solid-liquid PCMs,issues such as leakage,low thermal conductivity,lack of efficient solar-thermal media,and flamma-bility have constrained their broad applications.Herein,we present an innova-tive class of versatile composite phase change materials(CPCMs)developed through a facile and environmentally friendly synthesis approach,leveraging the inherent anisotropy and unidirectional porosity of wood aerogel(nanowood)to support polyethylene glycol(PEG).The wood modification process involves the incorporation of phytic acid(PA)and MXene hybrid structure through an evaporation-induced assembly method,which could impart non-leaking PEG filling while concurrently facilitating thermal conduction,light absorption,and flame-retardant.Consequently,the as-prepared wood-based CPCMs showcase enhanced thermal conductivity(0.82 W m^(-1)K^(-1),about 4.6 times than PEG)as well as high latent heat of 135.5 kJ kg^(-1)(91.5%encapsula-tion)with thermal durability and stability throughout at least 200 heating and cooling cycles,featuring dramatic solar-thermal conversion efficiency up to 98.58%.In addition,with the synergistic effect of phytic acid and MXene,the flame-retardant performance of the CPCMs has been significantly enhanced,showing a self-extinguishing behavior.Moreover,the excellent electromagnetic shielding of 44.45 dB was endowed to the CPCMs,relieving contemporary health hazards associated with electromagnetic waves.Overall,we capitalize on the exquisite wood cell structure with unidirectional transport inherent in the development of multifunctional CPCMs,showcasing the operational principle through a proof-of-concept prototype system.
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supported by the National Natural Sci-ence Foundation of China(Nos.52377026 and 52301192)Tais-han Scholars and Young Experts Program of Shandong Province(No.tsqn202103057)+4 种基金Postdoctoral Fellowship Program of CPSF(No.GZB20240327)Shandong Postdoctoral Science Foundation(No.SDCX-ZG-202400275)Qingdao Postdoctoral Application Re-search Project(No.QDBSH20240102023)China Postdoctoral Sci-ence Foundation(No.2024M751563)the Qingchuang Talents Induction Program of Shandong Higher Education Institution(Re-search and Innovation Team of Structural-Functional Polymer Composites).
文摘With the rapid development of 5G technology and the interconnection of industrial production,electro-magnetic pollution has become a serious problem.Achieving lightweight and controllable loads of ab-sorbers while obtaining corrosion-resistant absorbers with high electromagnetic response properties is still considered a huge challenge.In this work,carbon fiber with a multichannel hollow structure is ob-tained by PAN/PS hybrid electrospinning and subsequent high-temperature roasting process.The spatial structure inside the carbon fiber plays an active role in optimizing the impedance matching character-istics of the absorber.In addition,bimetallic metal-organic frameworks(MOFs)derivatives are obtained by a precisely controlled ion exchange as well as a high-temperature gas-phase selenization process.The resulting introduction of a non-homogeneous interface induces interfacial polarization and improves the absorption behavior of the absorber.The analysis of the experimental results shows that the electro-magnetic wave(EMW)absorption performance can be effectively enhanced due to the mechanisms of interface polarization and dipole polarization.The prepared NiSe/ZnSe/MHCFs composite can obtain ex-cellent EMW absorption properties in C,X,and Ku bands by adjusting the thickness.Structural design and component modulation play a crucial role in realizing the strong absorption and wide bandwidth of the absorber.Radar cross-section calculations indicate that NiSe/ZnSe/MHCFs have tremendous potential in practical military stealth technology.And the prepared composite coating can provide periodic corrosion resistance to Q235 steel sheet when dealing with complex and extreme environments.
基金support from the National Natural Science Foundation of China(No.U21A2093)Natural Science Foundation of Shaanxi Province(No.2022JM-260)Fundamental Research Funds for the Central Universities(No.G2022KY05109).This work is also financially supported by the Polymer Electromagnetic Functional Materials Innovation Team of Shaanxi Sanqin Scholars.We would like to thank Zhang San from Shiyanjia Lab(www.shiyanjia.com)for the VSM analysis.
文摘Multiple hetero-interfaces would strengthen interfacial polarization and boost electromagnetic wave absorption,but still remain the formidable challenges in decreasing filler loadings.Herein,sandwich NC@Co/NC@MnO_(2)composites with hollow cavity,multiple hetero-interfaces,and hierarchical structures have been fabricated via the cooperative processes of self-sacrifice strategy and sequential hydrothermal reaction.In the sandwich composites,middle magnetic components(Co/NC)are wrapped by inner N-doped carbon(NC)matrix and outer hierarchical MnO_(2)nanosheets.Importantly,hollow engineering of sandwich composites with multiple hetero-interfaces greatly facilitates the enhancement of absorption bandwidth without sacrificing the absorption intensity.The maximum reflection loss of sandwich NC@Co/NC@MnO_(2)composites reaches-44.8 dB at 2.5 mm and the effective bandwidths is achieved as wide as 9.6 GHz at 2.3 mm.These results provide us a new insight into preparing efficient electromagnetic wave absorbers by interface engineering and hollow construction.
基金financial support from the National Natural Science Foundation of China(Nos.U21A2093,and 12104164)partially financed by the Polymer Electro-magnetic Functional Materials Innovation Team of Shaanxi Sanqin Scholars.
文摘The control of undesired electromagnetic radiation in S-and C-band spectra requires novel microwave absorbing materials(MAMs)having high microwave attenuation capability together with optimal impedance matching.CNTs are conformally coated onto the surface of one-dimensional FeCo-based magnetic microchains via electrostatic self-assembly,and then the magnetic inclusions are collectively oriented in matrices by applying an external magnetic field.The proper incorporation of CNTs with magnetic microchains demonstrates a feasible pathway for effectively absorbing microwaves in the S and C band.MAMs consisting of oriented microchains have anisotropic complex permittivity,of which the real part ranges from 6.1 to 30.4 at 2 GHz.When the electric field is parallel to microchains,the 5-mm-thick MAM has an effective absorbing bandwidth(EAB)in the range of 2.3 to 2.9 GHz,and reduces the radar cross section to be lower than-15.9 dB m^(2) from the vertical to the glancing incidence.When the magnetic field is parallel to microchains,the MAM adsorbs C-band microwaves with an EAB of 1.5 GHz,and achieves maximal reflection loss of-46.4 dB.The collective orientation of shape-anisotropic magnetic materials,in addition to the composition and microstructure,is a new variable for the design of effective MAMs.
基金supported by the National Natural Science Foundation of China(52473083,52473084)the Natural Science Basic Research Program of Shaanxi(2024JC-TBZC-04)+6 种基金the Shaanxi Province Key Research and Development Plan Project(2023-YBGY-461,2024GX-YBXM-386)the Innovation Capability Support Program of Shaanxi(2024RS-CXTD-57)the Natural Science Basic Research Plan in Shaanxi Province of China(2024JC-YBMS-279)the Natural Science Foundation of Chongqing,China(2023NSCQ-MSX2547)the Innovation Foundation for Doctor Dissertation of Northwestern Polytechnical University(CX2024094)the Practice and Innovation Funds for Graduate Students of Northwestern Polytechnical University(PF2024119)the Undergraduate Innovation&Business Program in Northwestern Polytechnical University(S202410699503)。
文摘High integration,high frequency,high power,and miniaturization of electrical and electronic devices have raised higher demands for epoxy resins with both high intrinsic thermal conductivity and low dielectric properties.Herein,a series of linear fluorinated epoxy copolymers(poly(PFS-co-GMA))were synthesized via reversible addition-fragmentation chain transfer(RAFT)polymerization.Poly(PFS-co-GMA)was introduced into the cross-linked network of a biphenyl-based liquid crystalline epoxy(LCE)by forming a semi-interpenetrating polymer network(semi-IPN).The prepared liquid crystalline epoxy resins(LCERs)simultaneously exhibited high intrinsic thermal conductivity and low dielectric properties.The molar mass and mass fraction of poly(PFS-co-GMA)were found to have a profound effect on the thermal conductivity and dielectric performance of LCERs.For instance,poly(PFS-co-GMA)with the number average molar mass(M_(n))of 4300 and 7800 g/mol showed a decreasing effect on the thermal conductivity(λ)of LCERs whereas the polymer with M_(n)of 10500 g/mol enhanced theλ.The intrinsicλof LCERs increased to a remarkable highest value of 0.40 W/(m K),which was twice that of conventional epoxy resin(0.20 W/(m·K)).In addition,introducing poly(PFS-co-GMA)would significantly decrease the dielectric constant(ε)and dielectric loss tangent(tanδ)of LCERs from 3.44 and 0.035 to 2.49 and 0.001 at 1 MHz,respectively.Notably,theεand tanδcould remain relatively stable over a wide range of frequencies and temperatures up to 120℃.Additionally,the semi-IPN structure enhanced the hardness,electrical insulation,and hydrophobicity of LCERs.
基金support from the National Natural Science Foundation of China(Nos.52403114 and 52303104)Natural Science Basic Research Program of Shaanxi(No.2024JCTBZC-04)+8 种基金the Innovation Capability Support Program of Shaanxi(No.2024RS-CXTD-57)Shaanxi Province Key Research and Development Plan Project(No.2024GX-YBXM-386)Natural Science Foundation of Chongqing,China(No.2023NSCQMSX2547)Foundation of Aeronautics Science Fund(No.2024Z054053002)Fundamental Research Funds for the Central Universities(Nos.D5000240067 and D5000240077)Young Talent Fund of Association for Science and Technology in Shaanxi,China(No.20240455)Scientific Research Plan Project of Shaanxi Provincial Department of Education(No.24JP120)the Doctoral Research Start-up Funds of Xi'an University of Technology(No.108/451122007)the Analytical&Testing Center of Northwestern Polytechnical University for SEM,TEM and AFM tests performed in this work.
文摘The directional arrangement of two-dimensional thermally conductive fillers can fully exploit their anisotropic advantages and form efficient thermal conduction paths within the composites,thereby significantly improving their thermal conduction efficiency.In this study,“point-surface”hetero-structured boron nitride nanosheets(BNNS)@Ni thermally conductive fillers with magnetic response are synthesized via in-situ growth and high-temperature carbonization.The H-BNNS@Ni/PDMS(BNNS@Ni horizontally arranged in the polydimethylsiloxane(PDMS)matrix)thermally conductive composites are fabricated via magnetic field orientation.When the mass ratio of BNNS to Ni in BNNS@Ni is 8:1 and the mass fraction of BNNS@Ni is 50 wt.%,the in-plane thermal conductivity(λ_(∥))of H-BNNS@Ni/PDMS thermally conductive composites reaches 5.50 W/(m·K),which is 27.8 times higher than that of pure PDMS(0.19 W/(m·K)),and is also significantly higher than that of R-BNNS@Ni/PDMS(BNNS@Ni randomly distributed in the PDMS matrix)thermally conductive composites(4.76 W/(m·K))with the same mass fraction of BNNS@Ni.H-BNNS@Ni/PDMS thermally conductive composites can reduce the operating temperature at full power by 19.2℃compared to pure PDMS when used for CPU cooling.Meanwhile,H-BNNS@Ni/PDMS thermally conductive composites also exhibit excellent thermal resistance,photothermal conversion performance,and hydrophobicity.
基金support from the National Natural Science Foundation of China(52203100,52403112)the Innovation Capability Support Program of Shaanxi(2024RS-CXTD-57)+3 种基金the Natural Science Foundation of Chongqing,China(2023NSCQ-MSX2682)the Fundamental Research Funds for the Central Universities(D5000240062)the Wuhan University of Science and Technology Open Fund(KB202503)the Analytical&Testing Center of Northwestern Polytechnical University for the SEM,TEM,and AFM tests performed in this work.
文摘Heterostructure fillers are crucial for enhancing the electromagnetic interference(EMI)shielding performance of composites,and the core lies in the regulation of their morphology.Inspired by the radial structures on marimo surfaces during growth,we propose a bioinspired heterostructure assembly strategy to fabricate novel marimo-like hollow spherical reduced graphene oxide(hs-rGO)@nickel-catalyzed nitrogen-doped carbon nanotubes(Ni-NCNTs)and their corresponding polyimide aerogels.Benefiting from the synergistic design of multilevel porous architectures formed by the hollow microspheres in combination with the aerogel matrix,as well as radially aligned Ni-NCNTs epitaxially grown on hs-rGO surfaces,the resulting aerogels exhibit exceptional EMI shielding effectiveness,reaching up to 68 dB.Finite element simulations further elucidate the shielding mechanisms.Additionally,these aerogels exhibit rapid,durable pressure-sensing performance due to their excellent resilience and conductivity.The multifunctional combination of high-efficiency EMI shielding and mechanical sensing highlights their promising potential in next-generation intelligent electronics,aerospace systems,and advanced communication technologies.
