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
The thermal conductivity of nanofluids is an important property that influences the heat transfer capabilities of nanofluids.Researchers rely on experimental investigations to explore nanofluid properties,as it is a n...The thermal conductivity of nanofluids is an important property that influences the heat transfer capabilities of nanofluids.Researchers rely on experimental investigations to explore nanofluid properties,as it is a necessary step before their practical application.As these investigations are time and resource-consuming undertakings,an effective prediction model can significantly improve the efficiency of research operations.In this work,an Artificial Neural Network(ANN)model is developed to predict the thermal conductivity of metal oxide water-based nanofluid.For this,a comprehensive set of 691 data points was collected from the literature.This dataset is split into training(70%),validation(15%),and testing(15%)and used to train the ANN model.The developed model is a backpropagation artificial neural network with a 4–12–1 architecture.The performance of the developed model shows high accuracy with R values above 0.90 and rapid convergence.It shows that the developed ANN model accurately predicts the thermal conductivity of nanofluids.展开更多
Recent advancements in thermal conductivity modulating strategies have shown promising enhancements to the thermal management capabilities of two-dimensional materials.In this article,both the iterative Boltzmann tran...Recent advancements in thermal conductivity modulating strategies have shown promising enhancements to the thermal management capabilities of two-dimensional materials.In this article,both the iterative Boltzmann transport equation solution and the two-temperature model were employed to investigate the efficacy of targeted phonon excitation applied to hexagonal boron nitride(hBN).The results indicate significant modifications to hBN's thermal conductivity,achieving increases of up to 30.1%as well as decreases of up to 59.8%.These findings validate the reliability of the strategy,expand its scope of applicability,and establish it as a powerful tool for tailoring thermal properties across a wider range of fields.展开更多
Interface design for synergistic improvement of the thermal conductivity and dielectric properties of dielectrics is urgently needed but still challenging for the next generation of electronic and electrical equipment...Interface design for synergistic improvement of the thermal conductivity and dielectric properties of dielectrics is urgently needed but still challenging for the next generation of electronic and electrical equipment development.Herein,the authors report a strategy to screen structural units for the interface design of polymer dielectrics working under high-frequency and high-voltage conditions.Thermal conductivity,dielectric loss,the highest occupied molecular orbital(HOMO)and the lowest unoccupied molecular orbital(LUMO)gap are employed as key parameters to be considered simultaneously in the interface design for the screening.The authors find that a rigid ring with hydroxyl groups at symmetric sites can suppress the steric hindrance of neighbouring hydrogen bonds,leading to a better phonon spectrum matching and more efficient suppression of molecular chain segment motion,which ensures the dielectric insulating performance and thermal conduction performance simultaneously.Typically,alkyl polyglucoside(APG)was selected as the optimal modifier to demonstrate the interface designing principle experimentally,exhibiting improved thermal conductivity and suppressed dielectric loss,ultimately resulting in a 4.98-fold increase in the high-frequency breakdown time.This study provides important insights into decisive structural factors necessary to achieve dielectrics with excellent insulating properties under high-frequency applications.展开更多
Lead-free halide double perovskites(HDPs)provide a promising platform for high-performance thermoelectric due to their intrinsically ultralow lattice thermal conductivity k_(l).In this study,we comprehensively investi...Lead-free halide double perovskites(HDPs)provide a promising platform for high-performance thermoelectric due to their intrinsically ultralow lattice thermal conductivity k_(l).In this study,we comprehensively investigate the lattice dynamics of Cs_(2)AgInCl_(6)using first-principles calculations.By explicitly incorporating four-phonon scattering and wave-like phonon tunneling,we predict a k_(l)of 0.52 W·m^(-1)·K^(-1)with a remarkably weak temperature dependence(k_(l)∝T^(-0.31)),confirming the intrinsically glass-like ultralow k_(l)in Cs_(2)AgInCl_(6).Further analyses reveal that hierarchical chemical bonds,loosely bonded rattling atoms and a mixed crystalline-liquid state collectively induce strong anharmonicity manifested in flat phonon modes.These factors dominate the glass-like thermal transport component of k_(l).This work uncovers the underlying mechanisms governing the unusual thermal transport properties in lead-free HDPs and offers guiding principles for designing novel energy conversion technologies.展开更多
In recent years,there has been a growing global demand for carbon neutrality and energy efficiency,which are expected to become long-term trends.In the field of architecture,an effective approach to achieve this is to...In recent years,there has been a growing global demand for carbon neutrality and energy efficiency,which are expected to become long-term trends.In the field of architecture,an effective approach to achieve this is to reduce heat loss in buildings.Vacuum insulation panels(VIPs),a type of high-performance insulation material,have been increasingly utilised in the construction industry and have played an increa-singly important role as their performance and manufacturing processes continue to improve.This paper provides a review of the factors affecting the thermal conductivity of VIPs and presents a detailed overview of the research progress on core materials,barrier films,and getters.The current research status of VIPs is summarised,including their thermal conductivity,service life,and thermal bridging effects,as well as their applications in the field of architecture.This review aims to provide a comprehensive understanding for relevant practitioners on the factors influencing the thermal conductivity of VIPs,and based on which,measures can be taken to produce VIPs with lower thermal conductivity and longer service life.展开更多
High thermal conductivity and high strength Mg-1.5Mn-2.5Ce alloy with a tensile yield strength of 387.0 MPa,ultimate tensile strength of 395.8 MPa,and thermal conductivity of 142.1 W/(m·K)was successfully fabrica...High thermal conductivity and high strength Mg-1.5Mn-2.5Ce alloy with a tensile yield strength of 387.0 MPa,ultimate tensile strength of 395.8 MPa,and thermal conductivity of 142.1 W/(m·K)was successfully fabricated via hot extrusion.The effects of La and Ce additions on the microstructure,thermal conductivity,and mechanical properties of the Mg-1.5Mn alloy were investigated.The results indicated that both the as-extruded Mg-1.5Mn-2.5La and Mg-1.5Mn-2.5Ce alloys exhibited a bimodal grain structure,with dynamically precipitated nano-scaleα-Mn phases.In comparison with La,the addition of Ce enhanced the dynamic precipitation more effectively during hot extrusion,while its influence on promoting the dynamic recrystallization was relatively weaker.The high tensile strength obtained in the as-extruded Mg-1.5Mn-2.5RE alloys can be attributed to the combined influence of the bimodal grain structure(with fine dynamic recrystallized(DRXed)grain size and high proportion of un-dynamic recrystallized(unDRXed)grains),dense nano-scale precipitates,and broken Mg12RE phases,while the remarkable thermal conductivity was due to the precipitation of Mn-rich phases from the Mg matrix.展开更多
The rapid development of the information era has led to in-creased power consumption,which generates more heat.This requires more efficient thermal management systems,with the most direct ap-proach being the developme...The rapid development of the information era has led to in-creased power consumption,which generates more heat.This requires more efficient thermal management systems,with the most direct ap-proach being the development of su-perior thermal interface materials(TIMs).Mesocarbon microbeads(MCMBs)have several desirable properties for this purpose,includ-ing high thermal conductivity and excellent thermal stability.Although their thermal conductivity(K)may not be exceptional among all carbon materials,their ease of production and low cost make them ideal filler materials for developing a new generation of carbon-based TIMs.We report the fabrication of high-performance TIMs by incorporating MCMBs in a polyimide(PI)framework,producing highly graphitized PI/MCMB(PM)foams and anisotropic polydimethylsiloxane/PM(PDMS/PM)composites with a high thermal conductivity using directional freezing and high-temperature thermal annealing.The resulting materials had a high through-plane(TP)K of 15.926 W·m^(−1)·K^(−1),4.83 times that of conventional thermally conductive silicone pads and 88.5 times higher than that of pure PDMS.The composites had excellent mechanical properties and thermal stability,meeting the de-mands of modern electronic products for integration,multi-functionality,and miniaturization.展开更多
As one of the core components of a magnetic refrigerator,magnetic refrigeration materials are expected to have not only a considerable magnetocaloric effect but also excellent thermal conductivity.The poor thermal con...As one of the core components of a magnetic refrigerator,magnetic refrigeration materials are expected to have not only a considerable magnetocaloric effect but also excellent thermal conductivity.The poor thermal conductivity of many competitive oxide-based magnetic refrigerants,exemplified by EuTiO3-based compounds,acts as a major limitation to their practical application.Therefore,improving the thermal conductivity of magnetic refrigeration materials has become a research emphasis of magnetic refrigeration in recent years.In this work,a series of EuTiO_(3)(ETO)/Cu composites with different copper additives was prepared using a solid-phase reaction method by introducing appropriate amounts of copper powder.The influence of the introduction of copper on the phase composition,microstructure,thermal conductivity,and magnetocaloric effect of the composites was systematically investigated.Unexpectedly,the thermal conductivity of the composites is enhanced by up to 260%due to copper addition,accompanied by only a 5%decrease in magnetic entropy change and refrigerating capacity.Copper additive forms localized thermal conductive networks and promotes the densification process,resulting in significantly enhanced thermal conductivity of the composites.This work demonstrates the feasibility of improving the thermal conductivity of oxide-base d magnetic refrigeration materials by introducing highly thermally conductive substances.展开更多
The contradiction between mechanical properties and thermal conductivity of magnesium alloys is a roadblock for their widespread applications.In this study,we developed a hot-extruded Mg-8Gd-1Er-8Zn-1Mn alloy with hig...The contradiction between mechanical properties and thermal conductivity of magnesium alloys is a roadblock for their widespread applications.In this study,we developed a hot-extruded Mg-8Gd-1Er-8Zn-1Mn alloy with high-strength and high-thermal-conductivity via dual-phase,W-phase andα-Mn,synergistically strengthening.The alloy extruded at 300℃ exhibited the yield strength and elongation of 372 MPa and 12%,respectively,it simultaneously demonstrated a high thermal conductivity of 134.3W/(m·K).After extrusion,the original coarse W-phase in the alloy was broken into near-spheroidal particles,which reduced the probability of electron scattering.In addition,a large number of solute atoms dynamically precipitated in the form of nanoscale rod-like W-phase andα-Mn,makingα-Mg matrix revert to a nearly periodic arrangement state.The high yield strength of the alloy is predominantly determined by grain boundary strengthening as well as W-phase andα-Mn dual-phase strengthening.Notably,the strategy of dual-phase strengthening provides a valuable approach for developing structure-function integrated Mg alloys.展开更多
Heat dissipation highly relies on the thermal conductivity(κ)of materials.Materials with large bandgaps and signifcant atomic mass ratios,such as BAs,SiC,andθ-TaN,have attracted considerable attention due to their p...Heat dissipation highly relies on the thermal conductivity(κ)of materials.Materials with large bandgaps and signifcant atomic mass ratios,such as BAs,SiC,andθ-TaN,have attracted considerable attention due to their potential for achieving ultra-highκ,with BAs serving as a particularly representative example due to its unique combination of large bandgap and high thermal conductivity.In this paper,the efects of atomic mass modifcation on phonon bandgap andκare systematically investigated using a BAs model,accounting for both three-and four-phonon scattering processes.A 20%increase inκcan be obtained by substituting B,achieved through widening the phonon bandgap,which suppresses phonon scattering.Notably,the AAOO four-phonon scattering channel is more suppressed than the AAO three-phonon channel,leading to an increased phonon lifetime(τ).For As,κcan also be enhanced by 5%when replaced by lighter atoms,such as^(69)As,primarily due to the increased phonon group velocity(υ).We systematically clarify how atomic-mass-induced bandgap variations afectτ,υ,and thereforeκin wide-bandgap systems.Our work provides a specifc scheme for further improving the ultra-highκof materials with large bandgaps,which possesses great guiding signifcance.展开更多
The majority of industrial aluminum casting alloys exhibit low thermal conductivity,which is insufficient for effective heat transfer in electronic devices.The objective of this investigation was to develop new alumin...The majority of industrial aluminum casting alloys exhibit low thermal conductivity,which is insufficient for effective heat transfer in electronic devices.The objective of this investigation was to develop new aluminum casting alloys with high thermal conductivity.The impact of alloying elements on the thermal conductivity of pure aluminum was examined,and the relationships among microstructure,thermal conductivity,and the mechanical and corrosion properties of Al-Zn-Ca-(Cu,Mg)alloys were explored.The findings indicate that in the as-cast state,the structure of the alloys consists ofα-Al and a eutectic containing the(Al,Zn)4Ca phase.Following the solution heat treatment,the(Al,Zn)4Ca phase is spheroidised,and thermal conductivity of the alloys increases,reaching over 75%that of pure aluminum.However,the heat-treated alloys exhibit low mechanical properties:tensile yield strength<60 MPa,ultimate tensile strength<160 MPa,and elongation at fracture>15%.The alloys demonstrate satisfactory fluidity and low hot tearing susceptibility.With the exception of the alloy containing copper,the alloys exhibit low corrosion rates,estimated at approximately 0.02 mm/a.展开更多
Three kinds of Al−5Sr−5Sb modifiers were prepared by permanent mold casting(PMC),controlled diffusion solidification(CDS),and rolling.The influence of the preparation method on Al−5Sr−5Sb was examined by assessing the...Three kinds of Al−5Sr−5Sb modifiers were prepared by permanent mold casting(PMC),controlled diffusion solidification(CDS),and rolling.The influence of the preparation method on Al−5Sr−5Sb was examined by assessing the melting enthalpy from DSC curves and conducting first-principles calculations.Al−5Sr−5Sb was incorporated into AlSi10MnMg alloy to examine the modification effect and mechanism.It is found that the AlSi10MnMg alloy modified with CDS-prepared Al−5Sr−5Sb shows significant improvement in its microstructure,changing the eutectic Si phase from lamellar to coral-like or fiber-like structures.This modification leads to enhanced macroscopic properties:the thermal conductivity is increased by 24.14%to 189.63 W/(m·K),elongation is increased by 59.15%to 10.87%,and tensile strength is increased by 66.9%to 254.98 MPa compared to the unmodified alloy.展开更多
Carbon nanotubes are uniquely featured by the nanoscale tubular structure with a highly-curved surface and defined chirality.The diameter and chirality fundamentally determine their stability and electrical and therma...Carbon nanotubes are uniquely featured by the nanoscale tubular structure with a highly-curved surface and defined chirality.The diameter and chirality fundamentally determine their stability and electrical and thermal properties.Up to now,the relationship between the intrinsic thermal conductivity and the atomic features of CNTs has not been established,due to the challenges in precise measurements and characterizations.In this work,we develop a micro electro-thermal device enabling simultaneous thermal measurements by Raman spectroscopy and atomic structural characterization by transmission electron microscopy for individual CNTs.The influence of diameter and chirality is systematically investigated.In addition,the temperature dependence of the thermal conductivity was extracted from parameter optimization of finite-element modeling.It is found that the thermal transport of CNTs depends mainly on the diameter,while the chiral angle has no significant influence.Along with increasing diameter,the room temperature thermal conductivity increases and eventually approaches the limit of flat graphene.展开更多
Lead-free halide perovskites provide a promising solution for efficient thermoelectric materials due to their ultralow lattice thermal conductivity(κ_(L)).However,disadvantages such as the electrically resistive natu...Lead-free halide perovskites provide a promising solution for efficient thermoelectric materials due to their ultralow lattice thermal conductivity(κ_(L)).However,disadvantages such as the electrically resistive nature strongly affect their power factor.In this work,we introduced the Te-based halide perovskites thermoelectric material Cs_(2)TeI_(6),which is already known as a promising candidate for photovoltaic applications due to its moderate band gap.Our findings reveal that Cs_(2)TeI_(6)has an exceptionally ultralow κ_(L)at room temperature,reaching as low as 0.17 W·m^(-1)·K^(-1).We found that the four-phonon scattering processes play a dominant role in suppressing the thermal transport,leading to an approximate 50% reduction in its particle-like thermal conductivity κ_(p) at 300 K.The ultralow κ_(L)can be mainly attributed to the strong discrepancy in bonding strength,which induces large anharmonicity.The flat and dense phonon dispersions result in a strong phonon scattering rate,making it easy to generate wavelike phonon tunneling.After accounting for the wavelike thermal conductivity κ_(c),a nonstandard T^(-0.30)temperature dependence was observed.Benefiting from the ultralow κ_(L),n-type Cs_(2)TeI_(6)is predicted to achieve an extraordinary ZT of 2.26 at 700 K.This work highlights a pathway for searching high-performance and low-cost thermoelectrics based on lead-free halide perovskites.展开更多
This study explores the magnetohydrodynamic(MHD)boundary layer flow of a water-based Boger nanofluid over a stretching sheet,with particular focus on the influences of nanoparticle diameter,nanolayer effects,and therm...This study explores the magnetohydrodynamic(MHD)boundary layer flow of a water-based Boger nanofluid over a stretching sheet,with particular focus on the influences of nanoparticle diameter,nanolayer effects,and thermal radiation.The primary aim is to examine how variations in nanoparticle size and nanolayer thickness affect the hydrothermal behavior of the nanofluid.The model also incorporates the contributions of viscous dissipation and Joule heating within the heat transfer equation.The governing momentum and energy equations are converted into dimensionless partial differential equations(PDEs)using appropriate similarity variables and are numerically solved using the finite element method(FEM)implemented in MATLAB.Extensive validation of this method confirms its reliability and accuracy in numerical solutions.The findings reveal that increasing the diameter of copper nanoparticles significantly enhances the velocity profile,with a more pronounced effect observed at wider inter-particle spacings.A higher solvent volume fraction leads to decreased velocity and temperature distributions,while a greater relaxation time ratio improves velocity and temperature profiles due to the increased elastic response of the fluid.Moreover,enhancements in the magnetic parameter,thermal radiation,and Eckert number lead to an elevation in temperature profiles.Furthermore,higher nanolayer thickness reduces the temperature profile,whereas particle radius yields the opposite outcome.展开更多
The full arrival of 5 G and advances in electronic integration make efficient heat dissipation crucial for stable operation and longer product lifespan. In this study, a vacuum-assisted filtration process was employed...The full arrival of 5 G and advances in electronic integration make efficient heat dissipation crucial for stable operation and longer product lifespan. In this study, a vacuum-assisted filtration process was employed to fabricate ammoniated alumina/MXene/bacterial cellulose (Al_(2)O_(3)-NH_(2)/MXene/BC) composite films that display a unique integration of properties, encompassing ultra-high thermal conductivity (λ), mechanical flexibility, and high photothermal conversion performance. By leveraging the bridging effect among spherical Al_(2)O_(3)-NH_(2) and MXene nanosheets, a densely packed “point-surface” structure was constructed in BC by using a one-step preparation process. When the mass fraction of Al_(2)O_(3)-NH_(2)/MXene (1:3, w/w) is 40 wt%, the O-BAl1M3 exhibited an in-plane λ of 20.02 W m^(-1) K^(-1), which was 436 % and 94 % higher than that of pure BC and T-BAl1M3 (prepared by a two-step method), respectively. Furthermore, constructing an intact thermal conductive network within BC notably promoted photothermal and photoelectric conversion performance. The maximum surface temperature and voltage of the O-BAl1M3 film reached 106.9 ℃ and 48.34 mV when a sample with an area of 1.56 cm^(2) was exposed under a light intensity of 200 mW cm^(-2). By applying O-BAl1M3 film, the temperature inside a self-built greenhouse model reached up to 64.8 ℃ within 1200 s under a light intensity of 100 mW cm^(-2), which validated the practical application of the composite films and offered a novel approach for creating flexible films with superior photothermal conversion capability. This work provided insights into preparing functional composite films for efficient thermal management and photothermal conversion applications.展开更多
The demand for energy-efficient and environmental-friendly power grid construction has made the exploitation of bio-based electrical epoxy resins with excellent properties increasingly important.This work developed th...The demand for energy-efficient and environmental-friendly power grid construction has made the exploitation of bio-based electrical epoxy resins with excellent properties increasingly important.This work developed the bio-based electrotechnical epoxy resins based on magnolol.High-performance epoxy resin(DGEMT)with a double crosslinked points and its composites(Al_(2)O_(3)/DGEMT)were obtained taking advantages of the two bifunctional groups(allyl and phenolic hydroxyl groups)of magnolol.Benefitting from the distinctive structure of DGEMT,the Al_(2)O_(3)/DGEMT composites exhibited the advantages of intrinsically high thermal conductivity,high insulation,and low dielectric loss.The AC breakdown strength and thermal conductivity of Al_(2)O_(3)/DGEMT composites were 35.5 kV/mm and 1.19 W·m-1·K-1,respectively,which were 15.6%and 52.6%higher than those of petroleum-based composites(Al_(2)O_(3)/DGEBA).And its dielectric loss tanδ=0.0046 was 20.7%lower than that of Al_(2)O_(3)/DGEBA.Furthermore,the mechanical,thermal and processing properties of Al_(2)O_(3)/DGEMT are fully comparable to those of Al_(2)O_(3)/DGEBA.This work confirms the feasibility of manufacturing environmentally friendly power equipment using bio-based epoxy resins,which has excellent engineering applications.展开更多
The thermal conductivity of plasma-facing materials(PFM)exposed to intense radiation is a critical concern for the reliable usage of materials in fusion reactors.However,limited research has been performed regarding t...The thermal conductivity of plasma-facing materials(PFM)exposed to intense radiation is a critical concern for the reliable usage of materials in fusion reactors.However,limited research has been performed regarding the thermal conductivity of structures that rapidly change in a short time during collision cascade processes under irradiation.In this study,we employed the tight-binding(TB)method to investigate the electronic thermal conductivity(κ_(e))of tungsten-based systems during various cascading processes.We found thatκ_(e) values sharply decrease within the initial 0.3 picoseconds and then partially recover at a slow pace;this is closely linked to the evolution of defects and microstructural distortions.The increase in the initial kinetic energy of the primary knock-on atom and the presence of a high concentration of hydrogen atoms further decrease theκ_(e) values.Conversely,higher temperatures have a significant positive effect onκ_(e).Furthermore,the presence of a grain boundary∑5[001](130)substantially reducesκ_(e),whereas the absorption effect of point defects by the grain boundary has little influence onκ_(e) during cascades.Our findings provide a theoretical basis for evaluating changes in the thermal conductivity performance of PFMs during their usage in nuclear fusion reactors.展开更多
Polymer dielectrics possessing excellent electrical insulation and high thermal conductivity are pivotal for dielectric capacitors at elevated temperatures.However,the integration of electrical insulation and thermal ...Polymer dielectrics possessing excellent electrical insulation and high thermal conductivity are pivotal for dielectric capacitors at elevated temperatures.However,the integration of electrical insulation and thermal conductivity in polymers remains a challenge.In this work,we present a feasible strategy to integrate high electrical insulation and high thermal conductivity by bonding carbon quantum dots(CQDs)with the diamine monomer of polyetherimide(PEI).The CQDs with Coulomb blockade effect serve as traps for the migrating of electrons in the dielectrics,while the bonding networks formed by CQDs and PEI further deepen the traps and augment trap density.As a result,the hybrid dielectrics(PEI-NH_(2)-CQDs)exhibit nearly an order of magnitude higher electrical resistivity than that of pure PEI,leading to an 80%increase in discharge energy density with an energy efficiency of 90%at 200℃ compared to pure counterpart.Additionally,this all-organic dielectric achieves a significantly increased thermal conductivity of 0.65 W m^(-1) K^(-1) compared to 0.26 W m^(-1) K^(-1) of PEI,which supports its cyclic stability at elevated temperatures.We also demonstrate the kilogram-scale production of CQDs,synthesizing over 8 kg in a single batch,paving the way for large-scale production of reliable PEI-NH_(2)-CQDs dielectrics.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supported by Basic Science Research Program through the National Research Foundation of Korea(NRF)funded by the Ministry of Education(2021R1A6A1A10044950).
文摘The thermal conductivity of nanofluids is an important property that influences the heat transfer capabilities of nanofluids.Researchers rely on experimental investigations to explore nanofluid properties,as it is a necessary step before their practical application.As these investigations are time and resource-consuming undertakings,an effective prediction model can significantly improve the efficiency of research operations.In this work,an Artificial Neural Network(ANN)model is developed to predict the thermal conductivity of metal oxide water-based nanofluid.For this,a comprehensive set of 691 data points was collected from the literature.This dataset is split into training(70%),validation(15%),and testing(15%)and used to train the ANN model.The developed model is a backpropagation artificial neural network with a 4–12–1 architecture.The performance of the developed model shows high accuracy with R values above 0.90 and rapid convergence.It shows that the developed ANN model accurately predicts the thermal conductivity of nanofluids.
基金supported by the National Key Research and Development Project of China(Grant No.2018YFE0127800)。
文摘Recent advancements in thermal conductivity modulating strategies have shown promising enhancements to the thermal management capabilities of two-dimensional materials.In this article,both the iterative Boltzmann transport equation solution and the two-temperature model were employed to investigate the efficacy of targeted phonon excitation applied to hexagonal boron nitride(hBN).The results indicate significant modifications to hBN's thermal conductivity,achieving increases of up to 30.1%as well as decreases of up to 59.8%.These findings validate the reliability of the strategy,expand its scope of applicability,and establish it as a powerful tool for tailoring thermal properties across a wider range of fields.
基金supported by National Key Research and Development Program of China(Grant No.2023YFB2408200).
文摘Interface design for synergistic improvement of the thermal conductivity and dielectric properties of dielectrics is urgently needed but still challenging for the next generation of electronic and electrical equipment development.Herein,the authors report a strategy to screen structural units for the interface design of polymer dielectrics working under high-frequency and high-voltage conditions.Thermal conductivity,dielectric loss,the highest occupied molecular orbital(HOMO)and the lowest unoccupied molecular orbital(LUMO)gap are employed as key parameters to be considered simultaneously in the interface design for the screening.The authors find that a rigid ring with hydroxyl groups at symmetric sites can suppress the steric hindrance of neighbouring hydrogen bonds,leading to a better phonon spectrum matching and more efficient suppression of molecular chain segment motion,which ensures the dielectric insulating performance and thermal conduction performance simultaneously.Typically,alkyl polyglucoside(APG)was selected as the optimal modifier to demonstrate the interface designing principle experimentally,exhibiting improved thermal conductivity and suppressed dielectric loss,ultimately resulting in a 4.98-fold increase in the high-frequency breakdown time.This study provides important insights into decisive structural factors necessary to achieve dielectrics with excellent insulating properties under high-frequency applications.
基金supported by the National Natural Science Foundation of China(Grant No.12204482),the Natural Science Foundation of Shanxi Province(Grant No.202403021221164)Higher education teaching reform and innovation project of Shanxi Province(Grant No.J20220480)the Natural Science Foundation of Hainan Province(Grant Nos.525MS080 and 225MS076).
文摘Lead-free halide double perovskites(HDPs)provide a promising platform for high-performance thermoelectric due to their intrinsically ultralow lattice thermal conductivity k_(l).In this study,we comprehensively investigate the lattice dynamics of Cs_(2)AgInCl_(6)using first-principles calculations.By explicitly incorporating four-phonon scattering and wave-like phonon tunneling,we predict a k_(l)of 0.52 W·m^(-1)·K^(-1)with a remarkably weak temperature dependence(k_(l)∝T^(-0.31)),confirming the intrinsically glass-like ultralow k_(l)in Cs_(2)AgInCl_(6).Further analyses reveal that hierarchical chemical bonds,loosely bonded rattling atoms and a mixed crystalline-liquid state collectively induce strong anharmonicity manifested in flat phonon modes.These factors dominate the glass-like thermal transport component of k_(l).This work uncovers the underlying mechanisms governing the unusual thermal transport properties in lead-free HDPs and offers guiding principles for designing novel energy conversion technologies.
文摘In recent years,there has been a growing global demand for carbon neutrality and energy efficiency,which are expected to become long-term trends.In the field of architecture,an effective approach to achieve this is to reduce heat loss in buildings.Vacuum insulation panels(VIPs),a type of high-performance insulation material,have been increasingly utilised in the construction industry and have played an increa-singly important role as their performance and manufacturing processes continue to improve.This paper provides a review of the factors affecting the thermal conductivity of VIPs and presents a detailed overview of the research progress on core materials,barrier films,and getters.The current research status of VIPs is summarised,including their thermal conductivity,service life,and thermal bridging effects,as well as their applications in the field of architecture.This review aims to provide a comprehensive understanding for relevant practitioners on the factors influencing the thermal conductivity of VIPs,and based on which,measures can be taken to produce VIPs with lower thermal conductivity and longer service life.
基金supported by National Key Research&Development Program of China(Grant Nos.2021YFB3703300,2021YFE010016 and 2020YFA0405900)National Natural Science Foundation(Grant Nos.52220105003 and 51971075)+2 种基金the Fundamental Research Funds for the Central Universities(Grant No.FRFCU5710000918)Natural Science Foundation of Heilongjiang Province-Outstanding Youth Fund(Grant No.YQ2020E006)JSPS KAKENHI(Grant No.JP21H01669).
文摘High thermal conductivity and high strength Mg-1.5Mn-2.5Ce alloy with a tensile yield strength of 387.0 MPa,ultimate tensile strength of 395.8 MPa,and thermal conductivity of 142.1 W/(m·K)was successfully fabricated via hot extrusion.The effects of La and Ce additions on the microstructure,thermal conductivity,and mechanical properties of the Mg-1.5Mn alloy were investigated.The results indicated that both the as-extruded Mg-1.5Mn-2.5La and Mg-1.5Mn-2.5Ce alloys exhibited a bimodal grain structure,with dynamically precipitated nano-scaleα-Mn phases.In comparison with La,the addition of Ce enhanced the dynamic precipitation more effectively during hot extrusion,while its influence on promoting the dynamic recrystallization was relatively weaker.The high tensile strength obtained in the as-extruded Mg-1.5Mn-2.5RE alloys can be attributed to the combined influence of the bimodal grain structure(with fine dynamic recrystallized(DRXed)grain size and high proportion of un-dynamic recrystallized(unDRXed)grains),dense nano-scale precipitates,and broken Mg12RE phases,while the remarkable thermal conductivity was due to the precipitation of Mn-rich phases from the Mg matrix.
文摘The rapid development of the information era has led to in-creased power consumption,which generates more heat.This requires more efficient thermal management systems,with the most direct ap-proach being the development of su-perior thermal interface materials(TIMs).Mesocarbon microbeads(MCMBs)have several desirable properties for this purpose,includ-ing high thermal conductivity and excellent thermal stability.Although their thermal conductivity(K)may not be exceptional among all carbon materials,their ease of production and low cost make them ideal filler materials for developing a new generation of carbon-based TIMs.We report the fabrication of high-performance TIMs by incorporating MCMBs in a polyimide(PI)framework,producing highly graphitized PI/MCMB(PM)foams and anisotropic polydimethylsiloxane/PM(PDMS/PM)composites with a high thermal conductivity using directional freezing and high-temperature thermal annealing.The resulting materials had a high through-plane(TP)K of 15.926 W·m^(−1)·K^(−1),4.83 times that of conventional thermally conductive silicone pads and 88.5 times higher than that of pure PDMS.The composites had excellent mechanical properties and thermal stability,meeting the de-mands of modern electronic products for integration,multi-functionality,and miniaturization.
基金Project supported by the National Key R&D Program of China(2021YFB3501204)the National Science Fund for Distinguished Young Scholars(51925605)+1 种基金the National Science Foundation for Excellent Young Scholars(52222107)the National Natural Science Foundation of China(52171195,52201036)。
文摘As one of the core components of a magnetic refrigerator,magnetic refrigeration materials are expected to have not only a considerable magnetocaloric effect but also excellent thermal conductivity.The poor thermal conductivity of many competitive oxide-based magnetic refrigerants,exemplified by EuTiO3-based compounds,acts as a major limitation to their practical application.Therefore,improving the thermal conductivity of magnetic refrigeration materials has become a research emphasis of magnetic refrigeration in recent years.In this work,a series of EuTiO_(3)(ETO)/Cu composites with different copper additives was prepared using a solid-phase reaction method by introducing appropriate amounts of copper powder.The influence of the introduction of copper on the phase composition,microstructure,thermal conductivity,and magnetocaloric effect of the composites was systematically investigated.Unexpectedly,the thermal conductivity of the composites is enhanced by up to 260%due to copper addition,accompanied by only a 5%decrease in magnetic entropy change and refrigerating capacity.Copper additive forms localized thermal conductive networks and promotes the densification process,resulting in significantly enhanced thermal conductivity of the composites.This work demonstrates the feasibility of improving the thermal conductivity of oxide-base d magnetic refrigeration materials by introducing highly thermally conductive substances.
基金supported by the Nation Key Research and Development Program of China(No.2021YFB3701100).
文摘The contradiction between mechanical properties and thermal conductivity of magnesium alloys is a roadblock for their widespread applications.In this study,we developed a hot-extruded Mg-8Gd-1Er-8Zn-1Mn alloy with high-strength and high-thermal-conductivity via dual-phase,W-phase andα-Mn,synergistically strengthening.The alloy extruded at 300℃ exhibited the yield strength and elongation of 372 MPa and 12%,respectively,it simultaneously demonstrated a high thermal conductivity of 134.3W/(m·K).After extrusion,the original coarse W-phase in the alloy was broken into near-spheroidal particles,which reduced the probability of electron scattering.In addition,a large number of solute atoms dynamically precipitated in the form of nanoscale rod-like W-phase andα-Mn,makingα-Mg matrix revert to a nearly periodic arrangement state.The high yield strength of the alloy is predominantly determined by grain boundary strengthening as well as W-phase andα-Mn dual-phase strengthening.Notably,the strategy of dual-phase strengthening provides a valuable approach for developing structure-function integrated Mg alloys.
基金supported by the National Key Research and Development Program of China(Grant No.2023YFA1407001)the Department of Science and Technology of Jiangsu Province(Grant No.BK20220032)+1 种基金support from the Guang Dong Basic and Applied Basic Research Foundation(Grant No.2023A1515010365)support from the Postgraduate Research and Practice Innovation Program of Jiangsu Province under Grant No.KYCX25_1934。
文摘Heat dissipation highly relies on the thermal conductivity(κ)of materials.Materials with large bandgaps and signifcant atomic mass ratios,such as BAs,SiC,andθ-TaN,have attracted considerable attention due to their potential for achieving ultra-highκ,with BAs serving as a particularly representative example due to its unique combination of large bandgap and high thermal conductivity.In this paper,the efects of atomic mass modifcation on phonon bandgap andκare systematically investigated using a BAs model,accounting for both three-and four-phonon scattering processes.A 20%increase inκcan be obtained by substituting B,achieved through widening the phonon bandgap,which suppresses phonon scattering.Notably,the AAOO four-phonon scattering channel is more suppressed than the AAO three-phonon channel,leading to an increased phonon lifetime(τ).For As,κcan also be enhanced by 5%when replaced by lighter atoms,such as^(69)As,primarily due to the increased phonon group velocity(υ).We systematically clarify how atomic-mass-induced bandgap variations afectτ,υ,and thereforeκin wide-bandgap systems.Our work provides a specifc scheme for further improving the ultra-highκof materials with large bandgaps,which possesses great guiding signifcance.
基金supported by the Russian Science Foundation(No.24-29-00682,https://rscf.ru/project/24-29-00682/).
文摘The majority of industrial aluminum casting alloys exhibit low thermal conductivity,which is insufficient for effective heat transfer in electronic devices.The objective of this investigation was to develop new aluminum casting alloys with high thermal conductivity.The impact of alloying elements on the thermal conductivity of pure aluminum was examined,and the relationships among microstructure,thermal conductivity,and the mechanical and corrosion properties of Al-Zn-Ca-(Cu,Mg)alloys were explored.The findings indicate that in the as-cast state,the structure of the alloys consists ofα-Al and a eutectic containing the(Al,Zn)4Ca phase.Following the solution heat treatment,the(Al,Zn)4Ca phase is spheroidised,and thermal conductivity of the alloys increases,reaching over 75%that of pure aluminum.However,the heat-treated alloys exhibit low mechanical properties:tensile yield strength<60 MPa,ultimate tensile strength<160 MPa,and elongation at fracture>15%.The alloys demonstrate satisfactory fluidity and low hot tearing susceptibility.With the exception of the alloy containing copper,the alloys exhibit low corrosion rates,estimated at approximately 0.02 mm/a.
基金supported by Gansu Provincial Basic Research Program-Natural Science Fund,China(No.22JR5RA251)Science Fund for Distinguished Young Scholars of Gansu Province,China(No.23JRRA785)。
文摘Three kinds of Al−5Sr−5Sb modifiers were prepared by permanent mold casting(PMC),controlled diffusion solidification(CDS),and rolling.The influence of the preparation method on Al−5Sr−5Sb was examined by assessing the melting enthalpy from DSC curves and conducting first-principles calculations.Al−5Sr−5Sb was incorporated into AlSi10MnMg alloy to examine the modification effect and mechanism.It is found that the AlSi10MnMg alloy modified with CDS-prepared Al−5Sr−5Sb shows significant improvement in its microstructure,changing the eutectic Si phase from lamellar to coral-like or fiber-like structures.This modification leads to enhanced macroscopic properties:the thermal conductivity is increased by 24.14%to 189.63 W/(m·K),elongation is increased by 59.15%to 10.87%,and tensile strength is increased by 66.9%to 254.98 MPa compared to the unmodified alloy.
基金financially supported by the National Key Research and Development Program of China(Grant No.2022YFA1203302)the National Natural Science Foundation of China(Grant Nos.52130209,52188101)+4 种基金the JSPS Kakenhi(Grant Nos.JP25820336,JP20K05281,and JP23H01796)the JST-FOREST Program(Grant No.JPMJFR223T)the WPI-MANA“Challenging Research Program(CRP)”the National Institute for Materials Science(NIMS)“Support system for curiosity-driven research”the“Advanced Research Infrastructure for Materials and Nanotechnology in Japan(ARIM)”of the Ministry of Education,Culture,Sports,Science and Technology(MEXT)(Grant No.JPMXP1223NM5306).
文摘Carbon nanotubes are uniquely featured by the nanoscale tubular structure with a highly-curved surface and defined chirality.The diameter and chirality fundamentally determine their stability and electrical and thermal properties.Up to now,the relationship between the intrinsic thermal conductivity and the atomic features of CNTs has not been established,due to the challenges in precise measurements and characterizations.In this work,we develop a micro electro-thermal device enabling simultaneous thermal measurements by Raman spectroscopy and atomic structural characterization by transmission electron microscopy for individual CNTs.The influence of diameter and chirality is systematically investigated.In addition,the temperature dependence of the thermal conductivity was extracted from parameter optimization of finite-element modeling.It is found that the thermal transport of CNTs depends mainly on the diameter,while the chiral angle has no significant influence.Along with increasing diameter,the room temperature thermal conductivity increases and eventually approaches the limit of flat graphene.
基金supported by the National Natural Science Foundation of China(Grant Nos.12204482 and U2330104)the Scientific and Technological Innovation Programs of Higher Education Institutions in Shanxi(Grant No.2020L0537)+2 种基金the Natural Science Foundation of Shanxi Province(Grant No.202403021221164)Higher Education Teaching Reform and Innovation Project of Shanxi Province(Grant No.J20220480)Graduate Curriculum Ideological and Political Education Project of Shanxi Normal University(Grant No.010520233013)。
文摘Lead-free halide perovskites provide a promising solution for efficient thermoelectric materials due to their ultralow lattice thermal conductivity(κ_(L)).However,disadvantages such as the electrically resistive nature strongly affect their power factor.In this work,we introduced the Te-based halide perovskites thermoelectric material Cs_(2)TeI_(6),which is already known as a promising candidate for photovoltaic applications due to its moderate band gap.Our findings reveal that Cs_(2)TeI_(6)has an exceptionally ultralow κ_(L)at room temperature,reaching as low as 0.17 W·m^(-1)·K^(-1).We found that the four-phonon scattering processes play a dominant role in suppressing the thermal transport,leading to an approximate 50% reduction in its particle-like thermal conductivity κ_(p) at 300 K.The ultralow κ_(L)can be mainly attributed to the strong discrepancy in bonding strength,which induces large anharmonicity.The flat and dense phonon dispersions result in a strong phonon scattering rate,making it easy to generate wavelike phonon tunneling.After accounting for the wavelike thermal conductivity κ_(c),a nonstandard T^(-0.30)temperature dependence was observed.Benefiting from the ultralow κ_(L),n-type Cs_(2)TeI_(6)is predicted to achieve an extraordinary ZT of 2.26 at 700 K.This work highlights a pathway for searching high-performance and low-cost thermoelectrics based on lead-free halide perovskites.
基金supported by the Fundamental Research Funds for the Central Universities(Grant No.D5000230061)the Guangdong Basic and Applied Basic Research Foundation(Grant No.2025A1515011192).
文摘This study explores the magnetohydrodynamic(MHD)boundary layer flow of a water-based Boger nanofluid over a stretching sheet,with particular focus on the influences of nanoparticle diameter,nanolayer effects,and thermal radiation.The primary aim is to examine how variations in nanoparticle size and nanolayer thickness affect the hydrothermal behavior of the nanofluid.The model also incorporates the contributions of viscous dissipation and Joule heating within the heat transfer equation.The governing momentum and energy equations are converted into dimensionless partial differential equations(PDEs)using appropriate similarity variables and are numerically solved using the finite element method(FEM)implemented in MATLAB.Extensive validation of this method confirms its reliability and accuracy in numerical solutions.The findings reveal that increasing the diameter of copper nanoparticles significantly enhances the velocity profile,with a more pronounced effect observed at wider inter-particle spacings.A higher solvent volume fraction leads to decreased velocity and temperature distributions,while a greater relaxation time ratio improves velocity and temperature profiles due to the increased elastic response of the fluid.Moreover,enhancements in the magnetic parameter,thermal radiation,and Eckert number lead to an elevation in temperature profiles.Furthermore,higher nanolayer thickness reduces the temperature profile,whereas particle radius yields the opposite outcome.
基金support of this work by the Project of Education Department of Shaanxi Province(No.23JK0373)the Shaanxi University of Technology Graduate Innovation Fund(No.SLGYCX2402)the Talent Start-up Fund of Shaanxi University of Technology(No.SLGRCQD2329).
文摘The full arrival of 5 G and advances in electronic integration make efficient heat dissipation crucial for stable operation and longer product lifespan. In this study, a vacuum-assisted filtration process was employed to fabricate ammoniated alumina/MXene/bacterial cellulose (Al_(2)O_(3)-NH_(2)/MXene/BC) composite films that display a unique integration of properties, encompassing ultra-high thermal conductivity (λ), mechanical flexibility, and high photothermal conversion performance. By leveraging the bridging effect among spherical Al_(2)O_(3)-NH_(2) and MXene nanosheets, a densely packed “point-surface” structure was constructed in BC by using a one-step preparation process. When the mass fraction of Al_(2)O_(3)-NH_(2)/MXene (1:3, w/w) is 40 wt%, the O-BAl1M3 exhibited an in-plane λ of 20.02 W m^(-1) K^(-1), which was 436 % and 94 % higher than that of pure BC and T-BAl1M3 (prepared by a two-step method), respectively. Furthermore, constructing an intact thermal conductive network within BC notably promoted photothermal and photoelectric conversion performance. The maximum surface temperature and voltage of the O-BAl1M3 film reached 106.9 ℃ and 48.34 mV when a sample with an area of 1.56 cm^(2) was exposed under a light intensity of 200 mW cm^(-2). By applying O-BAl1M3 film, the temperature inside a self-built greenhouse model reached up to 64.8 ℃ within 1200 s under a light intensity of 100 mW cm^(-2), which validated the practical application of the composite films and offered a novel approach for creating flexible films with superior photothermal conversion capability. This work provided insights into preparing functional composite films for efficient thermal management and photothermal conversion applications.
基金supported by the China Postdoctoral Science Foundation(No.2023M743622)Natural Science Foundation of Ningbo City(No.2024J109)+2 种基金National Natural Science Foundation of China(Nos.E52307038 and U23A20589)Ningbo 2025 Key Scientific Research Programs(Nos.2022Z111,2022Z160 and 2022Z198)the Leading Innovativeand Entrepreneur Team Introduction Program of Zhejiang(No.2021R01005).
文摘The demand for energy-efficient and environmental-friendly power grid construction has made the exploitation of bio-based electrical epoxy resins with excellent properties increasingly important.This work developed the bio-based electrotechnical epoxy resins based on magnolol.High-performance epoxy resin(DGEMT)with a double crosslinked points and its composites(Al_(2)O_(3)/DGEMT)were obtained taking advantages of the two bifunctional groups(allyl and phenolic hydroxyl groups)of magnolol.Benefitting from the distinctive structure of DGEMT,the Al_(2)O_(3)/DGEMT composites exhibited the advantages of intrinsically high thermal conductivity,high insulation,and low dielectric loss.The AC breakdown strength and thermal conductivity of Al_(2)O_(3)/DGEMT composites were 35.5 kV/mm and 1.19 W·m-1·K-1,respectively,which were 15.6%and 52.6%higher than those of petroleum-based composites(Al_(2)O_(3)/DGEBA).And its dielectric loss tanδ=0.0046 was 20.7%lower than that of Al_(2)O_(3)/DGEBA.Furthermore,the mechanical,thermal and processing properties of Al_(2)O_(3)/DGEMT are fully comparable to those of Al_(2)O_(3)/DGEBA.This work confirms the feasibility of manufacturing environmentally friendly power equipment using bio-based epoxy resins,which has excellent engineering applications.
基金supported by the Collaborative Innovation Program of Hefei Science Center of CAS(No.2022HSC-CIP007)。
文摘The thermal conductivity of plasma-facing materials(PFM)exposed to intense radiation is a critical concern for the reliable usage of materials in fusion reactors.However,limited research has been performed regarding the thermal conductivity of structures that rapidly change in a short time during collision cascade processes under irradiation.In this study,we employed the tight-binding(TB)method to investigate the electronic thermal conductivity(κ_(e))of tungsten-based systems during various cascading processes.We found thatκ_(e) values sharply decrease within the initial 0.3 picoseconds and then partially recover at a slow pace;this is closely linked to the evolution of defects and microstructural distortions.The increase in the initial kinetic energy of the primary knock-on atom and the presence of a high concentration of hydrogen atoms further decrease theκ_(e) values.Conversely,higher temperatures have a significant positive effect onκ_(e).Furthermore,the presence of a grain boundary∑5[001](130)substantially reducesκ_(e),whereas the absorption effect of point defects by the grain boundary has little influence onκ_(e) during cascades.Our findings provide a theoretical basis for evaluating changes in the thermal conductivity performance of PFMs during their usage in nuclear fusion reactors.
基金supported by the National Natural Science Foundation of China(52172265)Excellent Youth Science Foundation of Hunan Province(2022JJ20067)+1 种基金The Science and Technology Innovation Program of Hunan Province(2022RC1074)Central South University Innovation-Driven Research Program(2023CXQD010).
文摘Polymer dielectrics possessing excellent electrical insulation and high thermal conductivity are pivotal for dielectric capacitors at elevated temperatures.However,the integration of electrical insulation and thermal conductivity in polymers remains a challenge.In this work,we present a feasible strategy to integrate high electrical insulation and high thermal conductivity by bonding carbon quantum dots(CQDs)with the diamine monomer of polyetherimide(PEI).The CQDs with Coulomb blockade effect serve as traps for the migrating of electrons in the dielectrics,while the bonding networks formed by CQDs and PEI further deepen the traps and augment trap density.As a result,the hybrid dielectrics(PEI-NH_(2)-CQDs)exhibit nearly an order of magnitude higher electrical resistivity than that of pure PEI,leading to an 80%increase in discharge energy density with an energy efficiency of 90%at 200℃ compared to pure counterpart.Additionally,this all-organic dielectric achieves a significantly increased thermal conductivity of 0.65 W m^(-1) K^(-1) compared to 0.26 W m^(-1) K^(-1) of PEI,which supports its cyclic stability at elevated temperatures.We also demonstrate the kilogram-scale production of CQDs,synthesizing over 8 kg in a single batch,paving the way for large-scale production of reliable PEI-NH_(2)-CQDs dielectrics.
