The in-flight heating process of cerium dioxide(CeO_(2))powders was investigated through experiments and numerical simulations.In the experiment,CeO_(2)powder(average size of 30μm)was injected into radio-frequency(RF...The in-flight heating process of cerium dioxide(CeO_(2))powders was investigated through experiments and numerical simulations.In the experiment,CeO_(2)powder(average size of 30μm)was injected into radio-frequency(RF)argon plasma,and the temperatures were measured using a DPV-2000 monitor.A model combining the electromagnetism,thermal flow,and heat transfer characteristics of powder during in-flight heating in argon plasma was proposed.The melting processes of CeO_(2)powders of different diameters,with and without thermal resistance effect,were investigated.Results show that the heating process of CeO_(2)powder particles consists of three main stages,one of which is relevant to a dimensionless parameter known as the Biot number.When the Biot value≥0.1,thermal resistance increases significantly,especially for the larger powders.The predicted temperature of the particles at the outlet(1800–2880 K)is in good agreement with the experimental result.展开更多
Six new lanthanide complexes:[Ln(3,4-DEOBA)3(4,4'-DM-2,2'-bipy)]2·2C_(2)H_(5)OH,[Ln=Dy(1),Eu(2),Tb(3),Sm(4),Ho(5),Gd(6);3,4-DEOBA-=3,4-diethoxybenzoate,4,4'-DM-2,2'-bipy=4,4'-dimethyl-2,2'...Six new lanthanide complexes:[Ln(3,4-DEOBA)3(4,4'-DM-2,2'-bipy)]2·2C_(2)H_(5)OH,[Ln=Dy(1),Eu(2),Tb(3),Sm(4),Ho(5),Gd(6);3,4-DEOBA-=3,4-diethoxybenzoate,4,4'-DM-2,2'-bipy=4,4'-dimethyl-2,2'-bipyridine]were successfully synthesized by the volatilization of the solution at room temperature.The crystal structures of six complexes were determined by single-crystal X-ray diffraction technology.The results showed that the complexes all have a binuclear structure,and the structures contain free ethanol molecules.Moreover,the coordination number of the central metal of each structural unit is eight.Adjacent structural units interact with each other through hydrogen bonds and further expand to form 1D chain-like and 2D planar structures.After conducting a systematic study on the luminescence properties of complexes 1-4,their emission and excitation spectra were obtained.Experimental results indicated that the fluorescence lifetimes of complexes 2 and 3 were 0.807 and 0.845 ms,respectively.The emission spectral data of complexes 1-4 were imported into the CIE chromaticity coordinate system,and their corre sponding luminescent regions cover the yellow light,red light,green light,and orange-red light bands,respectively.Within the temperature range of 299.15-1300 K,the thermal decomposition processes of the six complexes were comprehensively analyzed by using TG-DSC/FTIR/MS technology.The hypothesis of the gradual loss of ligand groups during the decomposition process was verified by detecting the escaped gas,3D infrared spectroscopy,and ion fragment information detected by mass spectrometry.The specific decomposition path is as follows:firstly,free ethanol molecules and neutral ligands are removed,and finally,acidic ligands are released;the final product is the corresponding metal oxide.CCDC:2430420,1;2430422,2;2430419,3;2430424,4;2430421,5;2430423,6.展开更多
The present work provides a facile and efficient method for producing ultrafine copper powders.Ultrafine copper powders were synthesized through a solvothermal method,utilizing ethanol both as a solvent and a reducing...The present work provides a facile and efficient method for producing ultrafine copper powders.Ultrafine copper powders were synthesized through a solvothermal method,utilizing ethanol both as a solvent and a reducing agent.Specifically,by exploiting the weak reducing property of ethanol,the copper precursor is first converted to copper oxide and then further reduced to cuprous oxide and pure copper.Such a method can effectively control the morphology and particle size of the copper powder,reduce particle aggregation,and enhance oxidation resistance.It is cost-effective and produces fewer toxic by-products.Spherical copper particles with an average particle size of about 180 nm were obtained.The initial oxidation temperature is approximately 150℃,and the resulting copper powders can be stored stably under ambient conditions for at least 5 months,demonstrating excellent oxidation resistance and thermal stability.展开更多
A series of blue and blue‑green Ir(Ⅲ)complexes has been investigated theoretically to explore their electronic structures,photophysical properties,efficiency roll‑off effect,and thermal activation delayed fluorescenc...A series of blue and blue‑green Ir(Ⅲ)complexes has been investigated theoretically to explore their electronic structures,photophysical properties,efficiency roll‑off effect,and thermal activation delayed fluorescence(TADF)properties.All calculations were performed using density functional theory(DFT)and time‑dependent density functional theory(TDDFT).Calculations for electronic structures,frontier molecular orbital characteristics(which determine the efficiency roll‑off effect of the complexes),and photophysical properties were conducted using the Gaussian 09 software package.The calculation of spin‑orbit coupling matrix elements<T|HSOC|S>,which determine the TADF properties of the complexes,was performed using the ORCA software package.The calculation results show that the auxiliary ligand tetraphenylimidodiphosphinate(tpip),a strong electron‑withdrawing group,can mitigate the efficiency roll‑off effect of the complex.Furthermore,TADF is observed in one of the designed complexes,(F_(3)Phppy)_(2)Ir(tpip),where F_(3)Phppy=2‑[4‑(2,4,6‑trifluorophenyl)phenyl]pyridine.展开更多
Dual-layer thermal barrier coatings(TBCs)with ultrahigh temperature resistance were prepared on the surface of molybdenum-rhenium alloy hot-end components.The preparation of the MoSi_(2)-Gd_(2)Zr_(2)O_(7)dual-layer TB...Dual-layer thermal barrier coatings(TBCs)with ultrahigh temperature resistance were prepared on the surface of molybdenum-rhenium alloy hot-end components.The preparation of the MoSi_(2)-Gd_(2)Zr_(2)O_(7)dual-layer TBCs was designed based on the coefficient of thermal expansion and the coating functionality,and it was completed using atmospheric plasma spraying technique.The microstructure,mechanical properties,and thermal properties were analyzed.Results indicate that the adhesion of the prepared dual-layer composite TBCs is excellent,and no noticeable cracks appear at the interface.Compared with the MoSi_(2)coating with a low fracture toughness(0.88 MPa·m^(1/2)),the Gd_(2)Zr_(2)O_(7)coating exhibits higher fracture toughness(1.74 MPa·m^(1/2))and stronger resistance to crack propagation.The prepared MoSi_(2)-Gd_(2)Zr_(2)O_(7)composite coatings have a high porosity(39%),low thermal conductivity(1.020 W·(m·K)^(−1),1200℃),and low thermal diffusivity(0.249 mm^(2)/s,1200℃).Additionally,they possess a high oxygen-vacancy concentration,which ensures excellent insulation performance.展开更多
High-concentration photovoltaic(HCPV)systems present significant thermal management challenges due to the intense heat fluxes generated under concentrated solar irradiation,especially in arid environments.Effective he...High-concentration photovoltaic(HCPV)systems present significant thermal management challenges due to the intense heat fluxes generated under concentrated solar irradiation,especially in arid environments.Effective heat dissipation is critical to prevent performance degradation and structural failure.This study investigates the thermal performance and design optimization of an enhanced HCPV module,integrating numerical,analytical,and experimental methods.A coupled optical-thermal-electrical model was developed to simulate ray tracing,heat transfer,and temperature-dependent electrical behaviour,with predictions validated under real-world desert conditions.Compared to a baseline commercial module operating at 106℃,the optimized design achieved a peak temperature reduction of 16℃,lowering the cell temperature to 90℃under a concentration ratio of 961×and direct normal irradiance(DNI)of 950 W/m^(2).The total thermal resistance was reduced from 0.25 to 0.15 K/W(a 40%improvement),and the electrical efficiency increased from 37.5%to 38.6%,representing a relative gain of approximately 3.1%.The system consistently maintained a fill factor exceeding 78%,underscoring stable performance under high thermal load.These findings demonstrate that targeted thermal design,informed by integrated modeling,is essential for unlocking the reliability and efficiency of high-flux solar energy systems.展开更多
Typically used thermal insulation materials such as foam insulation and fibreglass may pose notable health risks and environmental impacts thereby resulting in respiratory irritation andwaste disposal issues,respectiv...Typically used thermal insulation materials such as foam insulation and fibreglass may pose notable health risks and environmental impacts thereby resulting in respiratory irritation andwaste disposal issues,respectively.While these materials are affordable and display good thermal insulation,their unsustainable traits pertaining to an intensive manufacturing process and poor disposability are major concerns.Alternative insulation materials with enhanced sustainable characteristics are therefore being explored,and one type of material which has gained notable attention owing to its low carbon footprint and low thermal conductivity is natural fibre.Among the few review studies conducted on Natural Fibre Reinforced Composite(NFRC)insulation boards,the multitude of factors and underlying mechanisms affecting their thermal conductivity performance have been sparsely covered.This review study aimed to address this gap by providing a holistic overview of some of the key intrinsic and extrinsic factors affecting the thermal conductivity performance of NFRCs.Key intrinsic factors pertaining to the microstructural features and to the physico-mechanical traits of NFRCs,namely the fibre lumen size,α,and the fibre-matrix thermal conductivity ratio,β,respectively,were found to largely affect the Transverse Thermal Conductivity(TTC)in NFRC boards.Extrinsic factors,which were found to indirectly affect NFRCs’thermal conductivity,such as fibre pre-processing,composite manufacturing and environmental factors,were also covered.Some of the noteworthy NFRC featureswhich were found to affect their thermal conductivity are volume fraction of fibres,bulk density and porosity.The findings of this study highlight the need for additional research investigation to address the foregoing limitations observed in NFRC thermal insulation boards by considering appropriate natural fibres,composition and fabrication techniques.The fabrication of high-grade NFRC boards,which will display an optimum balance between enhanced thermal insulation and long-term durability performance,could further replace conventionally used thermal insulation boards in the modern building and construction industry.展开更多
Investigating the damage evolution of surrounding rock under thermal shock cycles is crucial for ensuring the stability of engineering rock masses.This study performed Brazilian splitting tests on granite specimens un...Investigating the damage evolution of surrounding rock under thermal shock cycles is crucial for ensuring the stability of engineering rock masses.This study performed Brazilian splitting tests on granite specimens under varying temperature and cycle conditions,employing acoustic emission monitoring,digital image correlation,and three-dimensional scanning technology.A systematic analysis was conducted on the patterns of damage evolution,failure precursor,and response mechanisms under combined thermal and cyclic loading.Experimental results show that both P-wave velocity and tensile strength degrade significantly with increasing temperature and cycle count,with temperature having a more pronounced effect than cycle count.Notably,damage evolution exhibits a dual-threshold behavior in which degradation accelerates markedly above 400℃ and stabilizes after 5 thermal cycles.Fracture surfaces evolve from initially planar to rugged morphologies,with peak-valley height differences at 600℃ being approximately three times greater than those at 200℃.Furthermore,based on acoustic emission energy entropy analysis,we introduce a novel failure precursor indicator where the sustained increase and critical surge in average entropy serve as reliable early-warning signals for impending rock failure.These findings establish a solid theoretical basis and practical methodology for damage assessment and instability early-warning systems in high-temperature rock engineering.展开更多
The effect of real-time high temperature and thermal treatment on the mechanical characteristics and crack evolution of granite with different grain sizes(i.e.,0.5 mm,0.7 mm and 1.0 mm)is investigated by numerical sim...The effect of real-time high temperature and thermal treatment on the mechanical characteristics and crack evolution of granite with different grain sizes(i.e.,0.5 mm,0.7 mm and 1.0 mm)is investigated by numerical simulation employing a grain-based model,and the impact of initial cracks on thermal-induced strengthening is also examined by integrating random cracks within the model before tests.The results revealed that thermal stress,induced by the mismatch in thermal expansion coefficient between various minerals,is the primary distinction between rock specimens in real-time high temperature and thermal treatment.With increasing temperature,the thermal stress gradually accumulates in quartz minerals under real-time high temperature but releases after thermal treatment.The high local contact force significantly affects the peak stress and crack evolution.Uniaxial compression simulation results demonstrate that progressive accumulation of thermal stress induces degradation in macroscopic peak strength and increase of microcrack density.The grain size controls the ratio of intergranular contacts to intragranular contacts,and leads to an increase in strong contact number in the intragrain and a decrease in strong contact number in the intergrain.The strengthening of uniaxial compression strength in the experiment can be well simulated by controlling the number of pre-existing initial cracks in the numerical model.Our conclusions are beneficial to a better understanding of the underlying mechanisms of thermal damage and thermal strengthening of granite for deep geological engineering.展开更多
There is an urgent need to develop magnesium-matrix materials that exhibit both high thermal conductivity and low thermal expansion to ensure compatibility with chips.This study aims to develop a Mg-Zn-Cu alloy with h...There is an urgent need to develop magnesium-matrix materials that exhibit both high thermal conductivity and low thermal expansion to ensure compatibility with chips.This study aims to develop a Mg-Zn-Cu alloy with high thermal conductivity.Furthermore,it explores the preparation of AlN_(P)/Mg-Zn-Cu composites featuring low coefficients of thermal expansion.The stir casting method was utilized to fabricate the composites and an investigation was conducted to examine their microstructure and thermal properties.Results indicate that the addition of AlN_(P)reduces the thermal expansion coefficient while maintaining relatively high thermal conductivity.Specifically,the AlN_(P)/Mg-0.5Zn-0.5Cu composite with 30wt.%AlN_(P)achieves a thermal conductivity of 132.7 W·m^(-1)·K^(-1)and a thermal expansion coefficient of 18.5×10^(-6)K^(-1),rendering it suitable for electronic packaging applications where thermal management is critical.展开更多
To address the challenge of balancing thermal management and thermal runaway mitigation,it is crucial to explore effective methods for enhancing the safety of lithium-ion battery systems.Herein,an innovative hydrated ...To address the challenge of balancing thermal management and thermal runaway mitigation,it is crucial to explore effective methods for enhancing the safety of lithium-ion battery systems.Herein,an innovative hydrated salt composite phase change material(HSCPCM)with dual phase transition temperature zones has been proposed.This HSCPCM,denoted as SDMA10,combines hydrophilic modified expanded graphite,an acrylic emulsion coating,and eutectic hydrated salts to achieve leakage prevention,enhanced thermal stability,cycling stability,and superior phase change behavior.Battery modules incorporating SDMA10 demonstrate significant thermal control capabilities.Specifically,the cylindrical battery modules with SDMA10 can maintain maximum operating temperatures below 55°C at 4 C discharge rate,while prismatic battery modules can keep maximum operating temperatures below 65°C at 2 C discharge rate.In extreme battery overheating conditions simulated using heating plates,SDMA10 effectively suppresses thermal propagation.Even when the central heating plate reaches 300°C,the maximum temperature at the module edge heating plates remains below 85°C.Further,compared to organic composite phase change materials(CPCMs),the battery module with SDMA10 can further reduce the peak thermal runaway temperature by 93°C and delay the thermal runaway trigger time by 689 s,thereby significantly decreasing heat diffusion.Therefore,the designed HSCPCM integrates excellent latent heat storage and thermochemical storage capabilities,providing high thermal energy storage density within the thermal management and thermal runaway threshold temperature range.This research will offer a promising pathway for improving the thermal safety performance of battery packs in electric vehicles and other energy storage systems.展开更多
In electrochemical energy storage systems,the sodium-ion battery is typically integrated in the form of a“cell-module-cluster”,but its cross-scale thermal runaway triggering risk and the propagation mechanism remain...In electrochemical energy storage systems,the sodium-ion battery is typically integrated in the form of a“cell-module-cluster”,but its cross-scale thermal runaway triggering risk and the propagation mechanism remain unclear.This study reveals the cross-scale thermal runaway triggering and propagation behavior of sodium-ion batteries of“cell-module-cluster”under overcharge conditions,and investigates the effects of key factors,including module spacing,triggering cell location,and heat dissipation condition,on the thermal runaway propagation behavior.Results demonstrate that the thermal runaway propagation in a module containing the overcharged cell follows a sequential triggering mode,while thermal runaway in the downstream module exhibits a simultaneous triggering mode with greater severity.Furthermore,increasing the module spacing or enhancing the heat dissipation capacity can effectively reduce the heat accumulation and prevent the trigger of thermal runaway.On the above basis,the multi-dimensional evaluation strategy is proposed to quantitatively assess the hazard of sodium-ion battery cluster thermal runaway.The findings serve as a foundation for the safe design of sodium-ion batteries in energy storage systems.展开更多
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
Thermochromic soft materials are flexible functional materials that adaptively tune optical properties(transmittance,reflectance,or scattering)with temperature for thermal modulation.Herein,a laminated thermochromic g...Thermochromic soft materials are flexible functional materials that adaptively tune optical properties(transmittance,reflectance,or scattering)with temperature for thermal modulation.Herein,a laminated thermochromic gel(DEE-DA)is synthesized by encapsulating a thermochromic hydrogel(DA)between two hydrophobic ionogels(DEE)in a stacked configuration.The synergy of multiple dynamic bonds endows the DEE-DA gel with exceptional mechanical properties and remarkable self-healing capability(98.8%at 30℃).More importantly,attributed to the temperature-responsive reversible cleavage and recombination of hydrogen bonds and borate ester bonds,DEE-DA gel demonstrates tunable transmittance with a light modulation efficiency of 85.45%.In response to the various external conditions,the gel can auto-adjust the optical properties to avoid sun irradiation or heat loss.Accordingly,the gel enables efficient dual-mode thermal modulation across a broad temperature range to realize thermal management.The research proposes gel thermochromism and laminated durability enhancement for adaptive materials in smart buildings and wearables.展开更多
Centrifugal casting of ductile iron pipe is a high-temperature,semi-continuous production process.However,conducting laboratory research on the solidification process of centrifugal casting of ductile iron pipe presen...Centrifugal casting of ductile iron pipe is a high-temperature,semi-continuous production process.However,conducting laboratory research on the solidification process of centrifugal casting of ductile iron pipe presents significant challenges.In this study,a novel research method was introduced for investigating the solidification process of ductile iron pipe,namely thermal simulation of ductile iron pipe.Comparative research was conducted on the microstructure and properties of the thermal simulation sample and the ductile iron pipe.The findings indicate that the thermal simulation sample and ductile iron pipe exhibit good heat transfer similarity and microstructure similarity.The difference of cooling rate between thermal simulation sample and ductile pipe is less than 0.24℃·s^(-1),and the difference of microstructure content of free cementite,ferrite,and pearlite is less than 5%.The tensile strength of annealed ductile iron pipe is 466 MPa,with an elongation of 16.1%and a Brinell hardness of 156.5 HBW.In comparison,the tensile strength of annealed thermal simulation sample is 482.0 MPa,with an elongation of 15.5%and a Brinell hardness of 159.0 HBW.These results suggest that the thermal simulation experimental research method is both scientific and feasible,offering an objective,reliable,and cost-effective approach to laboratory research on ductile iron pipe.展开更多
Chemical warfare agents(CWAs)remain a persistent hazard in many parts of the world,necessitating a deeper exploration of their chemical and physical characteristics and reactions under diverse conditions.Diisopropyl m...Chemical warfare agents(CWAs)remain a persistent hazard in many parts of the world,necessitating a deeper exploration of their chemical and physical characteristics and reactions under diverse conditions.Diisopropyl methylphosphonate(DIMP),a commonly used CWA surrogate,is widely studied to enhance our understanding of CWA behavior.The prevailing thermal decomposition model for DIMP,developed approximately 25 years ago,is based on data collected in nitrogen atmospheres at temperatures ranging from 700 K to 800 K.Despite its limitations,this model continues to serve as a foundation for research across various thermal and reactive environments,including combustion studies.Our recent experiments have extended the scope of decomposition analysis by examining DIMP in both nitrogen and zero air across a lower temperature range of 175℃ to 250℃.Infrared spectroscopy results under nitrogen align well with the established model;however,we observed that catalytic effects,stemming from decomposition byproducts and interactions with stainless steel surfaces,alter the reaction kinetics.In zero air environments,we observed a novel infrared absorption band.Spectral fitting suggests this band may represent a combination of propanal and acetone,while GCMS analysis points to vinyl formate and acetone as possible constituents.Although the precise identity of these new products remains unresolved,our findings clearly indicate that the existing decomposition model cannot be reliably extended to lower temperatures or non-nitrogen environments without further revisions.展开更多
Extreme cold weather seriously harms human thermoregulatory system,necessitating high-performance insulating garments to maintain body temperature.However,as the core insulating layer,advanced fibrous materials always...Extreme cold weather seriously harms human thermoregulatory system,necessitating high-performance insulating garments to maintain body temperature.However,as the core insulating layer,advanced fibrous materials always struggle to balance mechanical properties and thermal insulation,resulting in their inability to meet the demands for both washing resistance and personal protection.Herein,inspired by the natural spring-like structures of cucumber tendrils,a superelastic and washable micro/nanofibrous sponge(MNFS)based on biomimetic helical fibers is directly prepared utilizing multiple-jet electrospinning technology for high-performance thermal insulation.By regulating the conductivity of polyvinylidene fluoride solution,multiple-jet ejection and multiple-stage whipping of jets are achieved,and further control of phase separation rates enables the rapid solidification of jets to form spring-like helical fibers,which are directly entangled to assemble MNFS.The resulting MNFS exhibits superelasticity that can withstand large tensile strain(200%),1000 cyclic tensile or compression deformations,and retain good resilience even in liquid nitrogen(-196℃).Furthermore,the MNFS shows efficient thermal insulation with low thermal conductivity(24.85 mW m^(-1)K^(-1)),close to the value of dry air,and remains structural stability even after cyclic washing.This work offers new possibilities for advanced fibrous sponges in transportation,environmental,and energy applications.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
In this work,a computational modelling and analysis framework is developed to investigate the thermal buckling behavior of doubly-curved composite shells reinforced with graphene-origami(G-Ori)auxetic metamaterials.A ...In this work,a computational modelling and analysis framework is developed to investigate the thermal buckling behavior of doubly-curved composite shells reinforced with graphene-origami(G-Ori)auxetic metamaterials.A semi-analytical formulation based on the First-Order Shear Deformation Theory(FSDT)and the principle of virtual displacements is established,and closed-form solutions are derived via Navier’s method for simply supported boundary conditions.The G-Ori metamaterial reinforcements are treated as programmable constructs whose effective thermo-mechanical properties are obtained via micromechanical homogenization and incorporated into the shell model.A comprehensive parametric study examines the influence of folding geometry,dispersion arrangement,reinforcement weight fraction,curvature parameters,and elastic foundation support on the critical buckling temperature(CBT).The results reveal that,under optimal folding geometry and reinforcement alignment with principal stress trajectories,the CBT can increase by more than 150%.Furthermore,the combined effect of G-Ori reinforcement and elastic foundation substantially enhances thermal buckling resistance.These findings establish design guidelines for architected composite shells in applications such as aerospace thermal skins,morphing structures,and thermally-responsive systems,and illustrate the potential of auxetic graphene metamaterials for multifunctional,lightweight,and thermally robust structural components.展开更多
This study explores the nonlinear resonance of a rotating solar sail membrane exposed to time-varying solar thermal and solar radiation pressure.The sail membrane is modeled using a cantilever membrane,applying the vo...This study explores the nonlinear resonance of a rotating solar sail membrane exposed to time-varying solar thermal and solar radiation pressure.The sail membrane is modeled using a cantilever membrane,applying the von Kármán theory for membrane large deflection.The membrane’s nonlinear equation is derived by employing the Lagrange equation while accounting for excitations from solar thermal and radiation pressure.The equation is solved via the Rayleigh-Ritz method.The bifurcation diagram of membrane motion is applied to reveal membrane resonance responses under different solar sail rotating frequencies.The displacement time history,phase portrait,Poincarémap,frequency spectrum,and the largest Lyapunov exponent are used to study nonlinear vibrations that occur near resonance regions.The results indicate that time-varying thermal loading excites membrane motions with multiple natural frequencies by the parametric resonance mechanics,leading to the onset of membrane chaotic motion.The membrane’s primary resonance is stimulated in harmonic oscillation by the time-varying radiation pressure.The divergence instability caused by thermal excitation is also illustrated by comparing the membrane’s vibration amplitude with and without thermal excitation.The membrane’s nonlinear vibration characteristics vary significantly with solar illumination angles,the membrane’s thermal expansion coefficients,and structural damping.展开更多
基金National Natural Science Foundation of China(11875039)Shanxi Scholarship Council of China(2023-033)+2 种基金Fundamental Research Program of Shanxi Province(202303021221071)China Baowu Low Carbon Metallurgical Innovation Foundation(2022)2023 Anhui Major Industrial Innovation Plan Project。
文摘The in-flight heating process of cerium dioxide(CeO_(2))powders was investigated through experiments and numerical simulations.In the experiment,CeO_(2)powder(average size of 30μm)was injected into radio-frequency(RF)argon plasma,and the temperatures were measured using a DPV-2000 monitor.A model combining the electromagnetism,thermal flow,and heat transfer characteristics of powder during in-flight heating in argon plasma was proposed.The melting processes of CeO_(2)powders of different diameters,with and without thermal resistance effect,were investigated.Results show that the heating process of CeO_(2)powder particles consists of three main stages,one of which is relevant to a dimensionless parameter known as the Biot number.When the Biot value≥0.1,thermal resistance increases significantly,especially for the larger powders.The predicted temperature of the particles at the outlet(1800–2880 K)is in good agreement with the experimental result.
文摘Six new lanthanide complexes:[Ln(3,4-DEOBA)3(4,4'-DM-2,2'-bipy)]2·2C_(2)H_(5)OH,[Ln=Dy(1),Eu(2),Tb(3),Sm(4),Ho(5),Gd(6);3,4-DEOBA-=3,4-diethoxybenzoate,4,4'-DM-2,2'-bipy=4,4'-dimethyl-2,2'-bipyridine]were successfully synthesized by the volatilization of the solution at room temperature.The crystal structures of six complexes were determined by single-crystal X-ray diffraction technology.The results showed that the complexes all have a binuclear structure,and the structures contain free ethanol molecules.Moreover,the coordination number of the central metal of each structural unit is eight.Adjacent structural units interact with each other through hydrogen bonds and further expand to form 1D chain-like and 2D planar structures.After conducting a systematic study on the luminescence properties of complexes 1-4,their emission and excitation spectra were obtained.Experimental results indicated that the fluorescence lifetimes of complexes 2 and 3 were 0.807 and 0.845 ms,respectively.The emission spectral data of complexes 1-4 were imported into the CIE chromaticity coordinate system,and their corre sponding luminescent regions cover the yellow light,red light,green light,and orange-red light bands,respectively.Within the temperature range of 299.15-1300 K,the thermal decomposition processes of the six complexes were comprehensively analyzed by using TG-DSC/FTIR/MS technology.The hypothesis of the gradual loss of ligand groups during the decomposition process was verified by detecting the escaped gas,3D infrared spectroscopy,and ion fragment information detected by mass spectrometry.The specific decomposition path is as follows:firstly,free ethanol molecules and neutral ligands are removed,and finally,acidic ligands are released;the final product is the corresponding metal oxide.CCDC:2430420,1;2430422,2;2430419,3;2430424,4;2430421,5;2430423,6.
文摘The present work provides a facile and efficient method for producing ultrafine copper powders.Ultrafine copper powders were synthesized through a solvothermal method,utilizing ethanol both as a solvent and a reducing agent.Specifically,by exploiting the weak reducing property of ethanol,the copper precursor is first converted to copper oxide and then further reduced to cuprous oxide and pure copper.Such a method can effectively control the morphology and particle size of the copper powder,reduce particle aggregation,and enhance oxidation resistance.It is cost-effective and produces fewer toxic by-products.Spherical copper particles with an average particle size of about 180 nm were obtained.The initial oxidation temperature is approximately 150℃,and the resulting copper powders can be stored stably under ambient conditions for at least 5 months,demonstrating excellent oxidation resistance and thermal stability.
文摘A series of blue and blue‑green Ir(Ⅲ)complexes has been investigated theoretically to explore their electronic structures,photophysical properties,efficiency roll‑off effect,and thermal activation delayed fluorescence(TADF)properties.All calculations were performed using density functional theory(DFT)and time‑dependent density functional theory(TDDFT).Calculations for electronic structures,frontier molecular orbital characteristics(which determine the efficiency roll‑off effect of the complexes),and photophysical properties were conducted using the Gaussian 09 software package.The calculation of spin‑orbit coupling matrix elements<T|HSOC|S>,which determine the TADF properties of the complexes,was performed using the ORCA software package.The calculation results show that the auxiliary ligand tetraphenylimidodiphosphinate(tpip),a strong electron‑withdrawing group,can mitigate the efficiency roll‑off effect of the complex.Furthermore,TADF is observed in one of the designed complexes,(F_(3)Phppy)_(2)Ir(tpip),where F_(3)Phppy=2‑[4‑(2,4,6‑trifluorophenyl)phenyl]pyridine.
基金Supported by Scientific and Technological Innovation of Shaanxi Provincial State-Owned Capital Operation Budget(2022-056)Institute's Self-Developed Technology Program(0801YK2317)+4 种基金Qin Chuangyuan Cites High-Level Innovation and Entrepreneurship Talent Program(QCYRCXM-2023-120)Qin Chuangyuan Industry Cluster Zone“Four Chains”Integration Program(2024CY-JJQ-46)National Natural Science Foundation of China(52071274)Key Research and Development Projects of Shaanxi Province(2023-YBGY-442)Science and Technology Nova Project-Innovative Talent Promotion Program of Shaanxi Province(2020KJXX-062)。
文摘Dual-layer thermal barrier coatings(TBCs)with ultrahigh temperature resistance were prepared on the surface of molybdenum-rhenium alloy hot-end components.The preparation of the MoSi_(2)-Gd_(2)Zr_(2)O_(7)dual-layer TBCs was designed based on the coefficient of thermal expansion and the coating functionality,and it was completed using atmospheric plasma spraying technique.The microstructure,mechanical properties,and thermal properties were analyzed.Results indicate that the adhesion of the prepared dual-layer composite TBCs is excellent,and no noticeable cracks appear at the interface.Compared with the MoSi_(2)coating with a low fracture toughness(0.88 MPa·m^(1/2)),the Gd_(2)Zr_(2)O_(7)coating exhibits higher fracture toughness(1.74 MPa·m^(1/2))and stronger resistance to crack propagation.The prepared MoSi_(2)-Gd_(2)Zr_(2)O_(7)composite coatings have a high porosity(39%),low thermal conductivity(1.020 W·(m·K)^(−1),1200℃),and low thermal diffusivity(0.249 mm^(2)/s,1200℃).Additionally,they possess a high oxygen-vacancy concentration,which ensures excellent insulation performance.
基金funded by King Abdullah City for Atomic and Renewable Energy(KACARE),grant number“PC-2020-1”.
文摘High-concentration photovoltaic(HCPV)systems present significant thermal management challenges due to the intense heat fluxes generated under concentrated solar irradiation,especially in arid environments.Effective heat dissipation is critical to prevent performance degradation and structural failure.This study investigates the thermal performance and design optimization of an enhanced HCPV module,integrating numerical,analytical,and experimental methods.A coupled optical-thermal-electrical model was developed to simulate ray tracing,heat transfer,and temperature-dependent electrical behaviour,with predictions validated under real-world desert conditions.Compared to a baseline commercial module operating at 106℃,the optimized design achieved a peak temperature reduction of 16℃,lowering the cell temperature to 90℃under a concentration ratio of 961×and direct normal irradiance(DNI)of 950 W/m^(2).The total thermal resistance was reduced from 0.25 to 0.15 K/W(a 40%improvement),and the electrical efficiency increased from 37.5%to 38.6%,representing a relative gain of approximately 3.1%.The system consistently maintained a fill factor exceeding 78%,underscoring stable performance under high thermal load.These findings demonstrate that targeted thermal design,informed by integrated modeling,is essential for unlocking the reliability and efficiency of high-flux solar energy systems.
文摘Typically used thermal insulation materials such as foam insulation and fibreglass may pose notable health risks and environmental impacts thereby resulting in respiratory irritation andwaste disposal issues,respectively.While these materials are affordable and display good thermal insulation,their unsustainable traits pertaining to an intensive manufacturing process and poor disposability are major concerns.Alternative insulation materials with enhanced sustainable characteristics are therefore being explored,and one type of material which has gained notable attention owing to its low carbon footprint and low thermal conductivity is natural fibre.Among the few review studies conducted on Natural Fibre Reinforced Composite(NFRC)insulation boards,the multitude of factors and underlying mechanisms affecting their thermal conductivity performance have been sparsely covered.This review study aimed to address this gap by providing a holistic overview of some of the key intrinsic and extrinsic factors affecting the thermal conductivity performance of NFRCs.Key intrinsic factors pertaining to the microstructural features and to the physico-mechanical traits of NFRCs,namely the fibre lumen size,α,and the fibre-matrix thermal conductivity ratio,β,respectively,were found to largely affect the Transverse Thermal Conductivity(TTC)in NFRC boards.Extrinsic factors,which were found to indirectly affect NFRCs’thermal conductivity,such as fibre pre-processing,composite manufacturing and environmental factors,were also covered.Some of the noteworthy NFRC featureswhich were found to affect their thermal conductivity are volume fraction of fibres,bulk density and porosity.The findings of this study highlight the need for additional research investigation to address the foregoing limitations observed in NFRC thermal insulation boards by considering appropriate natural fibres,composition and fabrication techniques.The fabrication of high-grade NFRC boards,which will display an optimum balance between enhanced thermal insulation and long-term durability performance,could further replace conventionally used thermal insulation boards in the modern building and construction industry.
基金supported by National Natural Science Foundation of China (Nos.52264006,52364004,and 52464005)the Guizhou Provincial Science and Technology Foundation (No.GCC[2022]005-1)。
文摘Investigating the damage evolution of surrounding rock under thermal shock cycles is crucial for ensuring the stability of engineering rock masses.This study performed Brazilian splitting tests on granite specimens under varying temperature and cycle conditions,employing acoustic emission monitoring,digital image correlation,and three-dimensional scanning technology.A systematic analysis was conducted on the patterns of damage evolution,failure precursor,and response mechanisms under combined thermal and cyclic loading.Experimental results show that both P-wave velocity and tensile strength degrade significantly with increasing temperature and cycle count,with temperature having a more pronounced effect than cycle count.Notably,damage evolution exhibits a dual-threshold behavior in which degradation accelerates markedly above 400℃ and stabilizes after 5 thermal cycles.Fracture surfaces evolve from initially planar to rugged morphologies,with peak-valley height differences at 600℃ being approximately three times greater than those at 200℃.Furthermore,based on acoustic emission energy entropy analysis,we introduce a novel failure precursor indicator where the sustained increase and critical surge in average entropy serve as reliable early-warning signals for impending rock failure.These findings establish a solid theoretical basis and practical methodology for damage assessment and instability early-warning systems in high-temperature rock engineering.
基金Project(51879135)supported by the Taishan Scholars Program,ChinaProject(52309130)supported by the National Natural Science Foundation of China+1 种基金Project(SKLGME023003)supported by the Open Research Fund of State Key Laboratory of Geomechanics and Geotechnical Engineering Safety,ChinaProject(2022AH051754)supported by the Natural Science Research Project of Anhui Universities,China。
文摘The effect of real-time high temperature and thermal treatment on the mechanical characteristics and crack evolution of granite with different grain sizes(i.e.,0.5 mm,0.7 mm and 1.0 mm)is investigated by numerical simulation employing a grain-based model,and the impact of initial cracks on thermal-induced strengthening is also examined by integrating random cracks within the model before tests.The results revealed that thermal stress,induced by the mismatch in thermal expansion coefficient between various minerals,is the primary distinction between rock specimens in real-time high temperature and thermal treatment.With increasing temperature,the thermal stress gradually accumulates in quartz minerals under real-time high temperature but releases after thermal treatment.The high local contact force significantly affects the peak stress and crack evolution.Uniaxial compression simulation results demonstrate that progressive accumulation of thermal stress induces degradation in macroscopic peak strength and increase of microcrack density.The grain size controls the ratio of intergranular contacts to intragranular contacts,and leads to an increase in strong contact number in the intragrain and a decrease in strong contact number in the intergrain.The strengthening of uniaxial compression strength in the experiment can be well simulated by controlling the number of pre-existing initial cracks in the numerical model.Our conclusions are beneficial to a better understanding of the underlying mechanisms of thermal damage and thermal strengthening of granite for deep geological engineering.
基金financially supported by National Natural Science Foundation of China(No.52175321)the Fund of Key Laboratory of High Temperature Electromagnetic Materials and Structure of MOE(No.KB202505)。
文摘There is an urgent need to develop magnesium-matrix materials that exhibit both high thermal conductivity and low thermal expansion to ensure compatibility with chips.This study aims to develop a Mg-Zn-Cu alloy with high thermal conductivity.Furthermore,it explores the preparation of AlN_(P)/Mg-Zn-Cu composites featuring low coefficients of thermal expansion.The stir casting method was utilized to fabricate the composites and an investigation was conducted to examine their microstructure and thermal properties.Results indicate that the addition of AlN_(P)reduces the thermal expansion coefficient while maintaining relatively high thermal conductivity.Specifically,the AlN_(P)/Mg-0.5Zn-0.5Cu composite with 30wt.%AlN_(P)achieves a thermal conductivity of 132.7 W·m^(-1)·K^(-1)and a thermal expansion coefficient of 18.5×10^(-6)K^(-1),rendering it suitable for electronic packaging applications where thermal management is critical.
基金financially supported by Natural Science Foundation of Guangdong province(2024A1515010228)CATARC Automotive Inspection Center Excellent Engineer Program(2023B0909050007).
文摘To address the challenge of balancing thermal management and thermal runaway mitigation,it is crucial to explore effective methods for enhancing the safety of lithium-ion battery systems.Herein,an innovative hydrated salt composite phase change material(HSCPCM)with dual phase transition temperature zones has been proposed.This HSCPCM,denoted as SDMA10,combines hydrophilic modified expanded graphite,an acrylic emulsion coating,and eutectic hydrated salts to achieve leakage prevention,enhanced thermal stability,cycling stability,and superior phase change behavior.Battery modules incorporating SDMA10 demonstrate significant thermal control capabilities.Specifically,the cylindrical battery modules with SDMA10 can maintain maximum operating temperatures below 55°C at 4 C discharge rate,while prismatic battery modules can keep maximum operating temperatures below 65°C at 2 C discharge rate.In extreme battery overheating conditions simulated using heating plates,SDMA10 effectively suppresses thermal propagation.Even when the central heating plate reaches 300°C,the maximum temperature at the module edge heating plates remains below 85°C.Further,compared to organic composite phase change materials(CPCMs),the battery module with SDMA10 can further reduce the peak thermal runaway temperature by 93°C and delay the thermal runaway trigger time by 689 s,thereby significantly decreasing heat diffusion.Therefore,the designed HSCPCM integrates excellent latent heat storage and thermochemical storage capabilities,providing high thermal energy storage density within the thermal management and thermal runaway threshold temperature range.This research will offer a promising pathway for improving the thermal safety performance of battery packs in electric vehicles and other energy storage systems.
基金supported by the Anhui Quality Infrastructure Standardization Project(Grant No.2024MKSO7)the Science and Technology Project of State Grid(SGAHDK00DJJS2310027)the Anhui Provincial Natural Science Foundation(Grant No.2208085UD03).
文摘In electrochemical energy storage systems,the sodium-ion battery is typically integrated in the form of a“cell-module-cluster”,but its cross-scale thermal runaway triggering risk and the propagation mechanism remain unclear.This study reveals the cross-scale thermal runaway triggering and propagation behavior of sodium-ion batteries of“cell-module-cluster”under overcharge conditions,and investigates the effects of key factors,including module spacing,triggering cell location,and heat dissipation condition,on the thermal runaway propagation behavior.Results demonstrate that the thermal runaway propagation in a module containing the overcharged cell follows a sequential triggering mode,while thermal runaway in the downstream module exhibits a simultaneous triggering mode with greater severity.Furthermore,increasing the module spacing or enhancing the heat dissipation capacity can effectively reduce the heat accumulation and prevent the trigger of thermal runaway.On the above basis,the multi-dimensional evaluation strategy is proposed to quantitatively assess the hazard of sodium-ion battery cluster thermal runaway.The findings serve as a foundation for the safe design of sodium-ion batteries in energy storage systems.
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 the Yunlong Lake Laboratory of Deep Underground Science and Engineering Project(104024004)the National Natural Science Foundation of China(62288102)+2 种基金the Key Project of Basic Research Program of Jiangsu Province(BK20243036)the State Key Laboratory of Mechanics and Control for Aerospace Structures(Nanjing University of Aeronautics and astronautics)(MCAS-E-0124K01)the Cultivation Program for the Excellent Doctoral Dissertation of Nanjing Tech University(2023-06)。
文摘Thermochromic soft materials are flexible functional materials that adaptively tune optical properties(transmittance,reflectance,or scattering)with temperature for thermal modulation.Herein,a laminated thermochromic gel(DEE-DA)is synthesized by encapsulating a thermochromic hydrogel(DA)between two hydrophobic ionogels(DEE)in a stacked configuration.The synergy of multiple dynamic bonds endows the DEE-DA gel with exceptional mechanical properties and remarkable self-healing capability(98.8%at 30℃).More importantly,attributed to the temperature-responsive reversible cleavage and recombination of hydrogen bonds and borate ester bonds,DEE-DA gel demonstrates tunable transmittance with a light modulation efficiency of 85.45%.In response to the various external conditions,the gel can auto-adjust the optical properties to avoid sun irradiation or heat loss.Accordingly,the gel enables efficient dual-mode thermal modulation across a broad temperature range to realize thermal management.The research proposes gel thermochromism and laminated durability enhancement for adaptive materials in smart buildings and wearables.
基金financially supported by the National Natural Science Foundation of China(52130109)。
文摘Centrifugal casting of ductile iron pipe is a high-temperature,semi-continuous production process.However,conducting laboratory research on the solidification process of centrifugal casting of ductile iron pipe presents significant challenges.In this study,a novel research method was introduced for investigating the solidification process of ductile iron pipe,namely thermal simulation of ductile iron pipe.Comparative research was conducted on the microstructure and properties of the thermal simulation sample and the ductile iron pipe.The findings indicate that the thermal simulation sample and ductile iron pipe exhibit good heat transfer similarity and microstructure similarity.The difference of cooling rate between thermal simulation sample and ductile pipe is less than 0.24℃·s^(-1),and the difference of microstructure content of free cementite,ferrite,and pearlite is less than 5%.The tensile strength of annealed ductile iron pipe is 466 MPa,with an elongation of 16.1%and a Brinell hardness of 156.5 HBW.In comparison,the tensile strength of annealed thermal simulation sample is 482.0 MPa,with an elongation of 15.5%and a Brinell hardness of 159.0 HBW.These results suggest that the thermal simulation experimental research method is both scientific and feasible,offering an objective,reliable,and cost-effective approach to laboratory research on ductile iron pipe.
基金sponsored by the Department of Defense,Defense Threat Reduction Agency under the Materials Science in Extreme Environments University Research Alliance,HDTRA1-20-2-0001。
文摘Chemical warfare agents(CWAs)remain a persistent hazard in many parts of the world,necessitating a deeper exploration of their chemical and physical characteristics and reactions under diverse conditions.Diisopropyl methylphosphonate(DIMP),a commonly used CWA surrogate,is widely studied to enhance our understanding of CWA behavior.The prevailing thermal decomposition model for DIMP,developed approximately 25 years ago,is based on data collected in nitrogen atmospheres at temperatures ranging from 700 K to 800 K.Despite its limitations,this model continues to serve as a foundation for research across various thermal and reactive environments,including combustion studies.Our recent experiments have extended the scope of decomposition analysis by examining DIMP in both nitrogen and zero air across a lower temperature range of 175℃ to 250℃.Infrared spectroscopy results under nitrogen align well with the established model;however,we observed that catalytic effects,stemming from decomposition byproducts and interactions with stainless steel surfaces,alter the reaction kinetics.In zero air environments,we observed a novel infrared absorption band.Spectral fitting suggests this band may represent a combination of propanal and acetone,while GCMS analysis points to vinyl formate and acetone as possible constituents.Although the precise identity of these new products remains unresolved,our findings clearly indicate that the existing decomposition model cannot be reliably extended to lower temperatures or non-nitrogen environments without further revisions.
基金supported by Young Elite Scientists Sponsorship Program by China Association for Science and Technology(No.2022QNRC001)the National Natural Science Foundation of China(No.52273053)the Chenguang Program of Shanghai Education Development Foundation and Shanghai Municipal Education Commission(No.21CGA41)。
文摘Extreme cold weather seriously harms human thermoregulatory system,necessitating high-performance insulating garments to maintain body temperature.However,as the core insulating layer,advanced fibrous materials always struggle to balance mechanical properties and thermal insulation,resulting in their inability to meet the demands for both washing resistance and personal protection.Herein,inspired by the natural spring-like structures of cucumber tendrils,a superelastic and washable micro/nanofibrous sponge(MNFS)based on biomimetic helical fibers is directly prepared utilizing multiple-jet electrospinning technology for high-performance thermal insulation.By regulating the conductivity of polyvinylidene fluoride solution,multiple-jet ejection and multiple-stage whipping of jets are achieved,and further control of phase separation rates enables the rapid solidification of jets to form spring-like helical fibers,which are directly entangled to assemble MNFS.The resulting MNFS exhibits superelasticity that can withstand large tensile strain(200%),1000 cyclic tensile or compression deformations,and retain good resilience even in liquid nitrogen(-196℃).Furthermore,the MNFS shows efficient thermal insulation with low thermal conductivity(24.85 mW m^(-1)K^(-1)),close to the value of dry air,and remains structural stability even after cyclic washing.This work offers new possibilities for advanced fibrous sponges in transportation,environmental,and energy applications.
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.
文摘In this work,a computational modelling and analysis framework is developed to investigate the thermal buckling behavior of doubly-curved composite shells reinforced with graphene-origami(G-Ori)auxetic metamaterials.A semi-analytical formulation based on the First-Order Shear Deformation Theory(FSDT)and the principle of virtual displacements is established,and closed-form solutions are derived via Navier’s method for simply supported boundary conditions.The G-Ori metamaterial reinforcements are treated as programmable constructs whose effective thermo-mechanical properties are obtained via micromechanical homogenization and incorporated into the shell model.A comprehensive parametric study examines the influence of folding geometry,dispersion arrangement,reinforcement weight fraction,curvature parameters,and elastic foundation support on the critical buckling temperature(CBT).The results reveal that,under optimal folding geometry and reinforcement alignment with principal stress trajectories,the CBT can increase by more than 150%.Furthermore,the combined effect of G-Ori reinforcement and elastic foundation substantially enhances thermal buckling resistance.These findings establish design guidelines for architected composite shells in applications such as aerospace thermal skins,morphing structures,and thermally-responsive systems,and illustrate the potential of auxetic graphene metamaterials for multifunctional,lightweight,and thermally robust structural components.
基金supported by the Science Fund of NPU-Duke China Seeds Program(Grant No.119003067)the CAST-BISEE Fund(Grant No.MC010175)+1 种基金the Project of National Natural Science Foundation of China(Grant No.12372233)the“111”project of China(Grant No.B17037).
文摘This study explores the nonlinear resonance of a rotating solar sail membrane exposed to time-varying solar thermal and solar radiation pressure.The sail membrane is modeled using a cantilever membrane,applying the von Kármán theory for membrane large deflection.The membrane’s nonlinear equation is derived by employing the Lagrange equation while accounting for excitations from solar thermal and radiation pressure.The equation is solved via the Rayleigh-Ritz method.The bifurcation diagram of membrane motion is applied to reveal membrane resonance responses under different solar sail rotating frequencies.The displacement time history,phase portrait,Poincarémap,frequency spectrum,and the largest Lyapunov exponent are used to study nonlinear vibrations that occur near resonance regions.The results indicate that time-varying thermal loading excites membrane motions with multiple natural frequencies by the parametric resonance mechanics,leading to the onset of membrane chaotic motion.The membrane’s primary resonance is stimulated in harmonic oscillation by the time-varying radiation pressure.The divergence instability caused by thermal excitation is also illustrated by comparing the membrane’s vibration amplitude with and without thermal excitation.The membrane’s nonlinear vibration characteristics vary significantly with solar illumination angles,the membrane’s thermal expansion coefficients,and structural damping.
