An energetic binder based on hydroxyl-terminated polybutadiene(HTPB),doped with different ratios of nitrocellulose(NC)(10%,20%,30%,and 50%),was developed to study the effect of NC doping on the thermal decomposition b...An energetic binder based on hydroxyl-terminated polybutadiene(HTPB),doped with different ratios of nitrocellulose(NC)(10%,20%,30%,and 50%),was developed to study the effect of NC doping on the thermal decomposition behavior of a composite propellant(CP)comprising ammonium nitrate(AN)as an oxidizer and magnesium(Mg)as a fuel.Optimization of the propellant formulation was conducted using Chemical Equilibrium with Applications-National Aeronautics and Space Administration(CEA-NASA)software,which demonstrated an increase in specific impulse by 12.09 s when the binder contained 50%NC.Fourier-transform infrared spectroscopy(FTIR)analysis confirmed the excellent compatibility between the components,and density measurements revealed an increase of 6.4%with a higher NC content.Morphological analysis using optical microscopy showed that NC doping improved the uniformity and compactness of the surface,reduced cavities,and achieved a more homogeneous particle distribution.Differential scanning calorimetry(DSC)analysis indicated a decrease in the decomposition temperature of the propellant as the NC content increased,while kinetic studies revealed a 48.68%reduction in the activation energy when 50%NC was incorporated into the binder.These findings suggest that the addition of NC enhances combustion efficiency and improves overall propellant performance.This study highlights the potential of the new HTPB-NC energetic binder as a promising approach for advancing solid propellant technology.展开更多
The growing demand for geothermal energy exploration and deep engineering projects necessitates a deeper understanding of rock behavior under extreme thermal conditions.This study investigates the effect of thermal tr...The growing demand for geothermal energy exploration and deep engineering projects necessitates a deeper understanding of rock behavior under extreme thermal conditions.This study investigates the effect of thermal treatment on the shear behavior of sedimentary sandstone and igneous granite,which are abundant in the Earth's crust.Direct shear tests were conducted on rock joints at room temperature(RT),250℃,and 500℃.The results show that the joints in sandstone and granite exhibit improved compressive and shear strength up to a temperature threshold of 200℃–350℃,followed by significant weakening beyond this range.This study investigated key parameters,including normal and shear stiffness,maximum joint closure,peak and residual shear strengths,internal friction angle,dilation angle,and cohesion.The compressive behavior of both rock types followed a modifiedBandis's equation.The peak shear strength followed Patton's bilinear and Jaeger's nonlinear failure criteria more accurately than the Mohr–Coulomb criterion.The results of this study provide valuable insights into the temperature-dependent behavior of sandstone and granite joints under compressive and shear loads,and their interoperation was strongly dependent on the mineralogical and structural components of the two rock types.These results have advanced our understanding of the temperature-dependent behavior of rock fractures,improving the safety of underground structures under thermal effects.展开更多
High temperature and high stress are critical challenges facing enhanced geothermal systems(EGS).This study investigates the physical and mechanical behavior and acoustic emission(AE)characteristics of granite subject...High temperature and high stress are critical challenges facing enhanced geothermal systems(EGS).This study investigates the physical and mechanical behavior and acoustic emission(AE)characteristics of granite subjected to heating–water cooling treatments at temperatures ranging from 25℃ to 400℃.Changes in physical properties,including volume expansion,mass loss,and P-wave velocity,were examined to quantify the extent of thermal damage.Results show that visible surface cracking occurs on granite samples treated above 300℃,with P-wave velocity being the most sensitive indicator of thermal damage.Uniaxial and triaxial compression tests were conducted to explore the effects of temperature and confining pressure on granite’s strength,deformation,failure modes,energy evolution,and brittleness.While peak strength remains largely unaffected by temperature,failure modes transition from axial splitting to shear as confining pressure increases.Thermal damage reduces the rock’s energy storage capacity and increases energy dissipation during loading.The brittleness index decreases with temperature and confining pressure,though granite still exhibits pronounced brittle behavior within the studied range.Distinct differences were observed in the AE temporal characteristics and energy evolution of granite samples under uniaxial and triaxial compression conditions.As the specimen approaches failure,the abrupt increase in AE hit rate occurs earlier than the corresponding rise in AE energy.The global b-value of the granite samples increased with treatment temperature,and the global b-value in triaxial compression tests was higher than that in uniaxial compression tests.The evolution of timedependent b-value also varied with increasing confining pressure.These findings,particularly the AE temporal characteristics and distinct b-value evolution under confinement of thermally damaged granite,provide important implications for microseismic-based stability assessment and early warning in thermally damaged rock masses.展开更多
Exploring dynamic mechanical responses and failure behaviors of hot dry rock(HDR)is significant for geothermal exploitation and stability assessment.In this study,via the split Hopkinson pressure bar(SHPB)system,a ser...Exploring dynamic mechanical responses and failure behaviors of hot dry rock(HDR)is significant for geothermal exploitation and stability assessment.In this study,via the split Hopkinson pressure bar(SHPB)system,a series of dynamic compression tests were conducted on granite treated by cyclic thermal shocks at different temperatures.We analyzed the effects of cyclic thermal shock on the thermal-related physical and dynamic mechanical behaviors of granite.Specifically,the P-wave velocity,dynamic strength,and elastic modulus of the tested granite decrease with increasing temperature and cycle number,while porosity and peak strain increase.The degradation law of dynamic mechanical properties could be described by a cubic polynomial.Cyclic thermal shock promotes shear cracks propagation,causing dynamic failure mode of granite to transition from splitting to tensile-shear composite failure,accompanied by surface spalling and debris splashing.Moreover,the thermal shock damage evolution and coupled failure mechanism of tested granite are discussed.The evolution of thermal shock damage with thermal shock cycle numbers shows an obvious S-shaped surface,featured by an exponential correlation with dynamic mechanical parameters.In addition,with increasing thermal shock temperature and cycles,granite mineral species barely change,but the length and width of thermal cracks increase significantly.The non-uniform expansion of minerals,thermal shock-induced cracking,and water-rock interaction are primary factors for deteriorating dynamic mechanical properties of granite under cyclic thermal shock.展开更多
Sandwich piezoelectric semiconductor(PS)structures have significant applications in multi-functional semiconductor devices.The analysis of multi-field coupling behaviors of PS structures is of fundamental importance i...Sandwich piezoelectric semiconductor(PS)structures have significant applications in multi-functional semiconductor devices.The analysis of multi-field coupling behaviors of PS structures is of fundamental importance in developing novel PS devices.In this paper,we develop a general temperature-deformation-polarization-carrier(TDPC)coupling model for sandwich-type PS beams involving pyroelectricity under thermal loadings,based on three-dimensional(3D)basic equations of the thermo-piezoelectric semiconductor(TPS).We derive analytical solutions for extensional,bending,and buckling deformations of simply-supported sandwich n-type PS beams subjected to open-circuit and electrically isolated boundary conditions.The accuracy of the proposed model in this paper is verified through finite element simulations implemented in the COMSOL software.Numerical results show that the initial electron concentration and the thickness ratio of the PS layer to the beam's total thickness have a significant effect on thermally induced extensional and bending responses,as well as critical buckling mechanical and thermal loadings.This study provides a theoretical framework and guidance for designing semiconductor devices based on sandwich PS beam structures.展开更多
In this study,we simulated the thermal behavior of the mud-brick walls of a Nubian vault.We used EnergyPlus software for the simulation.The results obtained showed that the indoor temperature varies from 25.5℃ to 26....In this study,we simulated the thermal behavior of the mud-brick walls of a Nubian vault.We used EnergyPlus software for the simulation.The results obtained showed that the indoor temperature varies from 25.5℃ to 26.5℃ for the period of January 2018.It varies from 33.2℃ to 33.6℃ with an average value of 33.1℃ for the month of April 2018.For the period of July 2018,it varies from 30.3℃ to 32.2℃ with an average value of 31.2℃..Relative humidity for the period of July ranged from 62.3%to 73.5%,with an average value of 67.9%.The simulation enabled us to compare simulated and measured temperature and humidity values.We found that the level of thermal comfort in the Nubian vault is acceptable in both cool and hot periods.In view of these results,we can say that the Nubian vault is an architecture suited to our climate.The technical concept of the Nubian vault is adapted to the climatic conditions and traditional know-how of the Sahel.We also found that the use of raw earth,a locally available material,and the Nubian vault architectural process,contribute to thermal comfort and a reappropriation of local and adapted know-how.展开更多
In integrated circuit packaging,thermal interface materials(TIMs)must exhibit high thermal conductivity and electrical resistivity to prevent short circuits,enhance reliability,and ensure safety in high-voltage applic...In integrated circuit packaging,thermal interface materials(TIMs)must exhibit high thermal conductivity and electrical resistivity to prevent short circuits,enhance reliability,and ensure safety in high-voltage applications.We proposed the thermal-percolation electrical-resistive TIM incorporating binary fillers of both insulating and metallic nanowires with an orientation in the insulating polymer matrix.High thermal conductivity can be achieved through thermal percolation,while electrical non-conductivity is preserved by carefully controlling the electrical percolation threshold through metallic nanowire orientation.The electrical conductivity of the composite can be further regulated by adjusting the orientation and aspect ratio of the metallic fillers.A thermal conductivity of 10 W·m^(-1)·K^(-1)is achieved,with electrical non-conductive behavior preserved.This approach offers a pathway to realizing“thermal-percolation electrical-resistive”in hybrid TIMs,providing a strategic framework for designing high-performance TIMs.展开更多
An experiment was conducted to assess the impact of fused calcia-stabilized zirconia micro-powder on the thermal shock behavior of magnesia–spinel refractories.The effects of calcia-stabilized zirconia on the microst...An experiment was conducted to assess the impact of fused calcia-stabilized zirconia micro-powder on the thermal shock behavior of magnesia–spinel refractories.The effects of calcia-stabilized zirconia on the microstructure evolution and properties of magnesia–spinel refractories were characterized by the high-temperature elastic modulus,thermal shock damage resistance parameters,retainment of elastic modulus after thermal shock,and scanning electron microscopy.The results indicated that the incorporation of calcia-stabilized zirconia improved the thermomechanical properties and thermal shock behavior of magnesia–spinel specimens.The hot modulus of rupture of magnesia–spinel specimens increased by 2.5-fold due to the incorporation of calcia-stabilized zirconia micro-powder.The presence of a martensitic phase transformation in partially unstable ZrO2 and thermal mismatches among various phases contributed to a controlled formation of microcracks.And the pinning effect caused by the calcia-stabilized zirconia particles surrounding the grain boundaries played a crucial role in preventing the propagation of microcracks.This phenomenon significantly bolstered the thermal shock stability of magnesia–spinel refractories,consequently prolonging their service life.展开更多
This investigation aims to analyze thermal buckling and post-buckling behavior of functionally graded graphene nanoplateletreinforced composite(FG-GPLRC)beams.The beams are classified into two types of ideal and non-i...This investigation aims to analyze thermal buckling and post-buckling behavior of functionally graded graphene nanoplateletreinforced composite(FG-GPLRC)beams.The beams are classified into two types of ideal and non-ideal FG-GPLRC beams in which the ideal beams have smooth profiles of material distributions and another beams have layer-wise distributions of materials.The material profiles of the ideal beams are utilized as the controlling tracks for producing the material distributions of the non-ideal beams via a layer-to-layer integration technique.This technique confirms that the overall weight fraction of the materials is the same for both types of beams.The proposed models can be used to determine the material properties of the beams for further investigation on thermal buckling and post-buckling of the beams.Third-order shear deformation theory is employed to construct the energy equations of the problems,and then they are solved by the implementation of the Jacobi-Ritz method cooperating with the direct iteration procedure and Newton-Raphson technique.From our investigation,it can be disclosed that when non-ideal beams are created using ideal beams parabolic profile,the results differ significantly.However,the differences between the results of ideal and non-ideal beams can be eliminated by adding more layers.展开更多
The stimulation of shale reservoirs frequently involves significant shear failure,which is crucial for creating fracture networks and enhancing permeability to boost production.As the depth of extraction increases,the...The stimulation of shale reservoirs frequently involves significant shear failure,which is crucial for creating fracture networks and enhancing permeability to boost production.As the depth of extraction increases,the impact of elevated temperatures on the anisotropic shear strength and failure mechanisms of shale becomes pronounced,yet there is a notable lack of relevant research.This study conducts,for the first time,direct shear experiment on shales at four different temperatures and seven bedding angles.By employing acoustic emission(AE)and digital image correlation(DIC)techniques,the evolution of damage and the mechanism of crack propagation under anisotropic direct shearing at varying temperatures is revealed.The results indicate that both shear displacement and strength of shale increase with temperature across different bedding angles.Additionally,shale demonstrates distinct brittle failure characteristics under various conditions during direct shearing tests.The types of anisotropic shear failure observed under the influence of temperature include central shearing fracture,central shearing with secondary fracture,and deflected slip along the bedding.Moreover,the temperature effect enhances shear-induced crack propagation along bedding planes.Shear failure in shale predominantly occurs during higher loading stages,which coincide with a substantial amount of AE signals.Finally,the introduction of the anisotropy index and temperature sensitivity coefficient further elucidates the interaction mechanism between thermal effects and anisotropy.This study offers a novel methodology to explore the anisotropic shear failure behavior of shale under elevated temperatures,and also provides crucial theoretical and experimental insights into shear failure behavior relevant to practical shale reservoir stimulation.展开更多
Non-isothermal aging(NIA)is a composite heat treatment process that involves heating aging,cooling aging,and complex solute precipitation sequences.The precipitation behavior and the strengthening and toughening mecha...Non-isothermal aging(NIA)is a composite heat treatment process that involves heating aging,cooling aging,and complex solute precipitation sequences.The precipitation behavior and the strengthening and toughening mechanisms of the 2014 Al alloy during NIA were studied by employing tensile,fatigue crack growth,hardness,and electronic conductivity tests,as well as high-resolution transmission electron microscopy and scanning electron microscopy.The results show that during NIA,theθ′phase exhibits a complex process of nucleation,nucleation and growth,nucleation and growth and coarsening,growth and coarsening,nucleation and growth,and nucleation.NIA treatment imparts a mixed precipitation characteristic on the alloy,which is manifested as coherent precipitates,including GP zones,θ′′phases,small-sizedθ′phases,and semi-coherent or non-coherent precipitates such as large-sizedθ′phases and equilibriumθphases.The simultaneous strengthening and toughening of the NIA-treated 2014 Al alloy is caused by the synergistic effects of the particle-shearing mechanism and Orowan bypassing mechanism.展开更多
The Mountain Pass mine is recognized as one of the world's primary sources of rare earth minerals.These rare earth minerals mainly consist of bastnaesite and a small amount of monazite phosphate,which cannot be de...The Mountain Pass mine is recognized as one of the world's primary sources of rare earth minerals.These rare earth minerals mainly consist of bastnaesite and a small amount of monazite phosphate,which cannot be decomposed and recovered through conventional oxidative roasting and hydrochloric acid leaching process.An efficient,clean,and economical process called the"combined method"was proposed for the utilization of the Mountain Pass mine to extract rare earths from Mountain Pass rare earth concentrate(MPREC).The main steps of this process include weak oxidation atmosphere roasting,step leaching of hydrochloric acid,solid-liquid separation,the monazite slag with sulfuric acid roasting water leaching,etc.In this paper,the roasting process of MPREC under a weak oxidation atmosphere was investigated.The study examines the thermal decomposition kinetics,phase transition process,and leaching behavior of MPREC in air/CO_(2)atmosphere.Results show that,the activation energy(Ea)for MPREC thermal decomposition in air and CO_(2)atmosphere are 146 and 320 kJ/mol,respectively.At temperature above 500℃in air or above 700℃in CO_(2)atmosphere,REOF are generated from bastnaesite through an in-situ reaction with CaO,which is decomposed from CaCO_(3),to form CaF_(2)and rare earth oxide(REO).Thus,F is regulated into solid phase.In an oxidizing atmosphere,the thermal decomposition of bastnaesite is accompanied by the rapid oxidation of Ce(Ⅲ).In co ntrast,the oxidation of Ce(Ⅲ)in a CO_(2)atmosphere is significantly inhibited.At 700℃,the oxidation rate of Ce in air is 74.09%,while in a CO_(2)atmosphere,it is only 33.83%.The hydrochloric acid leaching experiment shows that,the leaching rate of rare earth after roasting at 600℃under an air atmosphere reaches to 82.9%,and it reaches 87%after roasting at 800℃under a CO_(2)atmosphere.The reduction of Ce oxidation in a weak oxidizing atmosphere significantly improves the leaching rate of Ce.展开更多
Effective thermal management is paramount for successfully deploying lithium-ion batteries in residential settings as storage systems for the exploitation of renewable sources.Uncontrolled temperature increases within...Effective thermal management is paramount for successfully deploying lithium-ion batteries in residential settings as storage systems for the exploitation of renewable sources.Uncontrolled temperature increases within battery packs can lead to critical issues such as cell overheating,potentially culminating in thermal runaway events and,in extreme cases,leading to fire or explosions.Thiswork presents a comprehensive numerical thermalmodel of a battery pack made of prototype pouch cells based on lithium ferrophosphate(LFP)chemistry.The multi-physical model is specifically developed to investigate real-world operating scenarios and to assess safety considerations.The considered energy storage system is a battery designed for residential applications,in its integration with a photovoltaic(PV)installation.The actual electrochemical behavior of the prototype cell during the charging and discharging processes is modeled and validated on the ground of experimental data.The essential steps leading to the numerical schematization of the battery pack are then presented to apply themodel to two different use scenarios,differing for the user loads.The first scenario corresponds to a typical residential load,with standby lights being active during the night,solar generation with its peak at noon,and appliance use shifting in the afternoon and the evening.In the second scenario,a double demand for energy is present thatmakes the battery never reach 100%of the State of Charge(SoC)and dischargemore rapidly with respect to what occurs under the first scenario.Comparing the simulated temperature with the assumed C-rate,namely the charge or discharge current divided by the battery nominal capacity,it is found that peaks coincide with the charging phase;subsequently,the current tends to a zero value,and consequently,the temperature suddenly reaches the value of the environment.Finally,the model is also utilized to simulate a condition of thermal runaway by introducing critical conditions within a specific pouch cell.In this simulation,the thermal exchange between the cell in thermal runaway and the rest of the system remains within acceptable limits.This occurs due to the short duration of the process and to the module casing coated with an insulating material.The work provides an essential foundation for conducting numerical simulations of battery packs operating also at higher power levels.展开更多
This study investigates the long-term thermal-oxidative stability and mechanical properties of phenolcontaining phthalonitrile monomer(PN75)and dicyanate ester of bisphenol-A(DCBA)composites reinforced with short carb...This study investigates the long-term thermal-oxidative stability and mechanical properties of phenolcontaining phthalonitrile monomer(PN75)and dicyanate ester of bisphenol-A(DCBA)composites reinforced with short carbon fibers T700SC(SCF)within a temperature range of 330375℃.The research focuses on the PN75 monomer and DCBA blend reinforced SCF composites with varying SCF content,examining mass loss and changes in flexural strength after thermal aging for 50 h(h).Results show that the SCF-reinforced composites based on the PN75/DCBA blend consistently outperform the neat blend in flexural strength,both at room temperature and after thermal aging.The introduction of the SCF significantly improves the composites'thermal stability and mechanical retention,with higher SCF content correlating to better performance.Notably,after aging at 350℃,the SCF-reinforced composites based(30%(mass)SCF)retained 88.8%of its flexural strength,compared to 61.1%for the neat blend.Morphological analysis reveals that while thermal aging causes degradation of the PN75/DCBA blend layer on SCF surfaces,the overall composite structure maintains good mechanical properties up to 350℃.At 375℃,significant degradation occurs,yet the composites still retain flexural strengths above 78 MPa.This study demonstrates the potential of the SCF-reinforced composites based on PN75/DCBA blend for high-temperature applications,establishing their upper-temperature limit for long-term use in oxidative environments.展开更多
Investigation of thermal effects on the strain rate-dependent properties of compacted bentonite is crucial for the long-term safety assessment of deep geological repository for disposal of high-level radioactive waste...Investigation of thermal effects on the strain rate-dependent properties of compacted bentonite is crucial for the long-term safety assessment of deep geological repository for disposal of high-level radioactive waste.In the present work,cylindrical GMZ01 bentonite specimens were compacted with suction-controlled by the vapor equilibrium technique.Then,a series of temperature-and suction-controlled stepwise constant rate of strain(CRS)tests was performed and the rate-dependent compressibility behavior of the highly compacted GMZ01 bentonite was investigated.The plastic compressibility parameterλ,the elastic compressibility parameterκ,the yield stress p0,as well as the viscous parameterαwere determined.Results indicate thatλ,κandαdecrease and p0 increases as suction increases.Upon heating,parametersλ,αand p0 decrease.It is also found that p0 increases linearly with increasing CRS in a double-logarithm coordinate.Based on the experimental results,a viscosity parameterα(s,T)was fitted to capture the effects of suction s and temperature T on the relationship between yield stress and strain rate.Then,an elastic-thermo-viscoplastic model for unsaturated soils was developed to describe the thermal effects on the rate-dependent behavior of highly compacted GMZ01 bentonite.Validation showed that the calculated results agreed well to the measured ones.展开更多
In this study,a novel Ni-based superalloy,ZGH451,has been fabricated using direct energy deposition(DED).The thermal fatigue resistance of ZGH451 is systematically evaluated at 900,1000,and 1100℃,primarily focusing o...In this study,a novel Ni-based superalloy,ZGH451,has been fabricated using direct energy deposition(DED).The thermal fatigue resistance of ZGH451 is systematically evaluated at 900,1000,and 1100℃,primarily focusing on the crack initiation and propagation behaviors.The results indicate that higher peak temperatures lead to earlier initiation and more rapid propagation of cracks.Cracks are initiated at the defects and grain boundaries in the vicinity of the notch,and different crack propagation mecha-nisms(γ'phase slip shearing,γ'phase distortion shearing,andγ'phase rafting shearing at 900,1000,and 1100℃,respectively)are the main reason for the different cracks propagation behaviors under the three temperatures.The main crack propagation paths are oriented at approximately 45°with respect to the build direction,suggesting activation of the{111}<110>slip system.Additionally,oxidation reduces the matrix strength and passivates the crack tips,leading to varying rates of crack propagation.At ele-vated temperatures,the synergistic effects of thermal stress and oxidative erosion are found to be the primary damage mechanisms of thermal fatigue.Overall,the proposed ZGH451 superalloy demonstrates exceptional thermal fatigue resistance,providing a crucial experimental reference for thermal fatigue in additively manufactured superalloys.展开更多
In lead-cooled fast reactor(LFR)systems,the liquid lead-bismuth eutectic(LBE)coolant provides a cor-rosive environment that damages the steel components during high-temperature operation.This study investigated the mi...In lead-cooled fast reactor(LFR)systems,the liquid lead-bismuth eutectic(LBE)coolant provides a cor-rosive environment that damages the steel components during high-temperature operation.This study investigated the microstructural deterioration of 9Cr ferritic/martensitic(F/M)steel under thermal aging at 550℃for 2,000,10,000,or 20,000 h and its effect on oxidation corrosion in an LBE environment using multiscale characterization techniques.The results indicated that the thickness of the internal oxidation zone(IOZ)increased significantly with extended thermal aging,whereas that of the spinel layer remained relatively constant.The abundant subgrain boundaries that emerged during extensive thermal aging facil-itated Fe diffusion,and the enlarged Cr-rich M23C6 carbides contributed to the formation of preferential oxidation regions,accelerating IOZ layer growth.The spinel layer formed from the IOZ was influenced by microstructural defects within the IOZ.A theoretical model describing the accelerated oxide layer growth due to thermal aging was developed.These findings support the advancement of LFR technology.展开更多
The AlMgScZr high-strength aluminum alloy fabricated by selective laser melting(SLM)technology exhibits a“bimodal microstructure”,resulting in significant non-uniform deformation during thermal deformation.This stud...The AlMgScZr high-strength aluminum alloy fabricated by selective laser melting(SLM)technology exhibits a“bimodal microstructure”,resulting in significant non-uniform deformation during thermal deformation.This study investigates the flow behavior of SLM-processed AlMgScZr aluminum alloy utilizing the Gleeble-1500D thermal simulation machine.The true stress-strain curves were amended based on the friction theory.Through determining the Zener-Hollomon parameters,the correlation between flow stress,deformation temperature,and strain rate during the high-temperature thermoplastic deformation of SLM-processed AlMgScZr aluminum alloy with a“bimodal microstructure”was established.In addition,the microstructural evolution during thermal deformation was analyzed.The results indicated that the predicted flow stress values obtained from the Arrhenius constitutive equation with coupled correction of thermal deformation parameters closely matched the experimental values.The correlation coefficient and the average absolute relative error of the corrected model were 0.999 and 2.766%,respectively,accurately predicting the thermoplastic deformation behavior of SLM-processed high-strength aluminum alloy with a“bimodal microstructure”.Furthermore,hot processing maps at different strains were established,identifying stable and unstable regions under different deformation conditions.Microstructural observations revealed different thermal deformation mechanisms under various deformation temperatures.Specifically,dynamic recrystallization characteristics dominated the microstructure at lower temperatures(300-360℃),while dynamic recovery was dominant at higher temperatures(390-500℃).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 influence of Hf on the precipitation behavior of γ'phase and the subsequent tensile properties of a Ni-Cr-Mo alloy after long-term thermal exposure was investigated.The results reveal that the addition of Hf ...The influence of Hf on the precipitation behavior of γ'phase and the subsequent tensile properties of a Ni-Cr-Mo alloy after long-term thermal exposure was investigated.The results reveal that the addition of Hf increases the average diameter ofγ'phases after thermal exposure at 700℃ for 5000 h,which enhances the critical resolved shear stress required for dislocations to shear the γ'phases in the Ni-Cr-Mo alloy.Simultaneously,element Hf incorporated into the γ'phases increases the lattice mismatch between the γ'and γ phase,thereby strengthening the coherency strengthening effect.These two factors collectively contribute to the enhanced strength of the alloy.Thus,Hf alloying effectively improves the yield strength of the Ni-Cr-Mo alloy after thermal exposure at 700℃.展开更多
文摘An energetic binder based on hydroxyl-terminated polybutadiene(HTPB),doped with different ratios of nitrocellulose(NC)(10%,20%,30%,and 50%),was developed to study the effect of NC doping on the thermal decomposition behavior of a composite propellant(CP)comprising ammonium nitrate(AN)as an oxidizer and magnesium(Mg)as a fuel.Optimization of the propellant formulation was conducted using Chemical Equilibrium with Applications-National Aeronautics and Space Administration(CEA-NASA)software,which demonstrated an increase in specific impulse by 12.09 s when the binder contained 50%NC.Fourier-transform infrared spectroscopy(FTIR)analysis confirmed the excellent compatibility between the components,and density measurements revealed an increase of 6.4%with a higher NC content.Morphological analysis using optical microscopy showed that NC doping improved the uniformity and compactness of the surface,reduced cavities,and achieved a more homogeneous particle distribution.Differential scanning calorimetry(DSC)analysis indicated a decrease in the decomposition temperature of the propellant as the NC content increased,while kinetic studies revealed a 48.68%reduction in the activation energy when 50%NC was incorporated into the binder.These findings suggest that the addition of NC enhances combustion efficiency and improves overall propellant performance.This study highlights the potential of the new HTPB-NC energetic binder as a promising approach for advancing solid propellant technology.
基金the ORSP at Abu Dhabi University,UAE,for funding this project(Grant No.19300751).
文摘The growing demand for geothermal energy exploration and deep engineering projects necessitates a deeper understanding of rock behavior under extreme thermal conditions.This study investigates the effect of thermal treatment on the shear behavior of sedimentary sandstone and igneous granite,which are abundant in the Earth's crust.Direct shear tests were conducted on rock joints at room temperature(RT),250℃,and 500℃.The results show that the joints in sandstone and granite exhibit improved compressive and shear strength up to a temperature threshold of 200℃–350℃,followed by significant weakening beyond this range.This study investigated key parameters,including normal and shear stiffness,maximum joint closure,peak and residual shear strengths,internal friction angle,dilation angle,and cohesion.The compressive behavior of both rock types followed a modifiedBandis's equation.The peak shear strength followed Patton's bilinear and Jaeger's nonlinear failure criteria more accurately than the Mohr–Coulomb criterion.The results of this study provide valuable insights into the temperature-dependent behavior of sandstone and granite joints under compressive and shear loads,and their interoperation was strongly dependent on the mineralogical and structural components of the two rock types.These results have advanced our understanding of the temperature-dependent behavior of rock fractures,improving the safety of underground structures under thermal effects.
基金supported by the CHN Energy Investment Group,grant numbers GJNY-23-86 and GJNY-23-92.
文摘High temperature and high stress are critical challenges facing enhanced geothermal systems(EGS).This study investigates the physical and mechanical behavior and acoustic emission(AE)characteristics of granite subjected to heating–water cooling treatments at temperatures ranging from 25℃ to 400℃.Changes in physical properties,including volume expansion,mass loss,and P-wave velocity,were examined to quantify the extent of thermal damage.Results show that visible surface cracking occurs on granite samples treated above 300℃,with P-wave velocity being the most sensitive indicator of thermal damage.Uniaxial and triaxial compression tests were conducted to explore the effects of temperature and confining pressure on granite’s strength,deformation,failure modes,energy evolution,and brittleness.While peak strength remains largely unaffected by temperature,failure modes transition from axial splitting to shear as confining pressure increases.Thermal damage reduces the rock’s energy storage capacity and increases energy dissipation during loading.The brittleness index decreases with temperature and confining pressure,though granite still exhibits pronounced brittle behavior within the studied range.Distinct differences were observed in the AE temporal characteristics and energy evolution of granite samples under uniaxial and triaxial compression conditions.As the specimen approaches failure,the abrupt increase in AE hit rate occurs earlier than the corresponding rise in AE energy.The global b-value of the granite samples increased with treatment temperature,and the global b-value in triaxial compression tests was higher than that in uniaxial compression tests.The evolution of timedependent b-value also varied with increasing confining pressure.These findings,particularly the AE temporal characteristics and distinct b-value evolution under confinement of thermally damaged granite,provide important implications for microseismic-based stability assessment and early warning in thermally damaged rock masses.
基金The authors are grateful for the financial support from the National Natural Science Foundation of China(Grant Nos.52225904 and 52039007)the Natural Science Foundation of Sichuan Province(Grant No.2023NSFSC0377)supported by the New Cornerstone Science Foundation through the XPLORER PRIZE.
文摘Exploring dynamic mechanical responses and failure behaviors of hot dry rock(HDR)is significant for geothermal exploitation and stability assessment.In this study,via the split Hopkinson pressure bar(SHPB)system,a series of dynamic compression tests were conducted on granite treated by cyclic thermal shocks at different temperatures.We analyzed the effects of cyclic thermal shock on the thermal-related physical and dynamic mechanical behaviors of granite.Specifically,the P-wave velocity,dynamic strength,and elastic modulus of the tested granite decrease with increasing temperature and cycle number,while porosity and peak strain increase.The degradation law of dynamic mechanical properties could be described by a cubic polynomial.Cyclic thermal shock promotes shear cracks propagation,causing dynamic failure mode of granite to transition from splitting to tensile-shear composite failure,accompanied by surface spalling and debris splashing.Moreover,the thermal shock damage evolution and coupled failure mechanism of tested granite are discussed.The evolution of thermal shock damage with thermal shock cycle numbers shows an obvious S-shaped surface,featured by an exponential correlation with dynamic mechanical parameters.In addition,with increasing thermal shock temperature and cycles,granite mineral species barely change,but the length and width of thermal cracks increase significantly.The non-uniform expansion of minerals,thermal shock-induced cracking,and water-rock interaction are primary factors for deteriorating dynamic mechanical properties of granite under cyclic thermal shock.
基金Project supported by the National Natural Science Foundation of China(No.11672265)。
文摘Sandwich piezoelectric semiconductor(PS)structures have significant applications in multi-functional semiconductor devices.The analysis of multi-field coupling behaviors of PS structures is of fundamental importance in developing novel PS devices.In this paper,we develop a general temperature-deformation-polarization-carrier(TDPC)coupling model for sandwich-type PS beams involving pyroelectricity under thermal loadings,based on three-dimensional(3D)basic equations of the thermo-piezoelectric semiconductor(TPS).We derive analytical solutions for extensional,bending,and buckling deformations of simply-supported sandwich n-type PS beams subjected to open-circuit and electrically isolated boundary conditions.The accuracy of the proposed model in this paper is verified through finite element simulations implemented in the COMSOL software.Numerical results show that the initial electron concentration and the thickness ratio of the PS layer to the beam's total thickness have a significant effect on thermally induced extensional and bending responses,as well as critical buckling mechanical and thermal loadings.This study provides a theoretical framework and guidance for designing semiconductor devices based on sandwich PS beam structures.
文摘In this study,we simulated the thermal behavior of the mud-brick walls of a Nubian vault.We used EnergyPlus software for the simulation.The results obtained showed that the indoor temperature varies from 25.5℃ to 26.5℃ for the period of January 2018.It varies from 33.2℃ to 33.6℃ with an average value of 33.1℃ for the month of April 2018.For the period of July 2018,it varies from 30.3℃ to 32.2℃ with an average value of 31.2℃..Relative humidity for the period of July ranged from 62.3%to 73.5%,with an average value of 67.9%.The simulation enabled us to compare simulated and measured temperature and humidity values.We found that the level of thermal comfort in the Nubian vault is acceptable in both cool and hot periods.In view of these results,we can say that the Nubian vault is an architecture suited to our climate.The technical concept of the Nubian vault is adapted to the climatic conditions and traditional know-how of the Sahel.We also found that the use of raw earth,a locally available material,and the Nubian vault architectural process,contribute to thermal comfort and a reappropriation of local and adapted know-how.
基金supported by the National Key R&D Program(Grant No.2022YFA1203-100)sponsorship by Shanghai Sailing Program(Grant No.24YF2713800)+2 种基金financial support from the Local College Capacity Building Project of Shanghai Municipal Science and Technology Commission(Grant No.20010500700)the Natural Science Foundation of Shanghai(Grant No.23ZR1424300)Shanghai Shuguang Program(Grant No.22SG56)。
文摘In integrated circuit packaging,thermal interface materials(TIMs)must exhibit high thermal conductivity and electrical resistivity to prevent short circuits,enhance reliability,and ensure safety in high-voltage applications.We proposed the thermal-percolation electrical-resistive TIM incorporating binary fillers of both insulating and metallic nanowires with an orientation in the insulating polymer matrix.High thermal conductivity can be achieved through thermal percolation,while electrical non-conductivity is preserved by carefully controlling the electrical percolation threshold through metallic nanowire orientation.The electrical conductivity of the composite can be further regulated by adjusting the orientation and aspect ratio of the metallic fillers.A thermal conductivity of 10 W·m^(-1)·K^(-1)is achieved,with electrical non-conductive behavior preserved.This approach offers a pathway to realizing“thermal-percolation electrical-resistive”in hybrid TIMs,providing a strategic framework for designing high-performance TIMs.
基金supported by the Key Project of the National Natural Science Foundation of China(Grant No.U21A2058)the Hebei Guoliang New Materials Co.,Ltd.(Grant No.22150239J).
文摘An experiment was conducted to assess the impact of fused calcia-stabilized zirconia micro-powder on the thermal shock behavior of magnesia–spinel refractories.The effects of calcia-stabilized zirconia on the microstructure evolution and properties of magnesia–spinel refractories were characterized by the high-temperature elastic modulus,thermal shock damage resistance parameters,retainment of elastic modulus after thermal shock,and scanning electron microscopy.The results indicated that the incorporation of calcia-stabilized zirconia improved the thermomechanical properties and thermal shock behavior of magnesia–spinel specimens.The hot modulus of rupture of magnesia–spinel specimens increased by 2.5-fold due to the incorporation of calcia-stabilized zirconia micro-powder.The presence of a martensitic phase transformation in partially unstable ZrO2 and thermal mismatches among various phases contributed to a controlled formation of microcracks.And the pinning effect caused by the calcia-stabilized zirconia particles surrounding the grain boundaries played a crucial role in preventing the propagation of microcracks.This phenomenon significantly bolstered the thermal shock stability of magnesia–spinel refractories,consequently prolonging their service life.
基金supported by the Thailand Science Research and Innovation Fund(Grant No.FRB660041/0227).
文摘This investigation aims to analyze thermal buckling and post-buckling behavior of functionally graded graphene nanoplateletreinforced composite(FG-GPLRC)beams.The beams are classified into two types of ideal and non-ideal FG-GPLRC beams in which the ideal beams have smooth profiles of material distributions and another beams have layer-wise distributions of materials.The material profiles of the ideal beams are utilized as the controlling tracks for producing the material distributions of the non-ideal beams via a layer-to-layer integration technique.This technique confirms that the overall weight fraction of the materials is the same for both types of beams.The proposed models can be used to determine the material properties of the beams for further investigation on thermal buckling and post-buckling of the beams.Third-order shear deformation theory is employed to construct the energy equations of the problems,and then they are solved by the implementation of the Jacobi-Ritz method cooperating with the direct iteration procedure and Newton-Raphson technique.From our investigation,it can be disclosed that when non-ideal beams are created using ideal beams parabolic profile,the results differ significantly.However,the differences between the results of ideal and non-ideal beams can be eliminated by adding more layers.
基金supported by the National Natural Science Fund of China (Grant Nos.U22A20166 and 52374131)the Shenzhen Science and Technology Program (Grant No.JCYJ20220531102012028)the Young Elite Scientists Sponsorship Program by CAST.
文摘The stimulation of shale reservoirs frequently involves significant shear failure,which is crucial for creating fracture networks and enhancing permeability to boost production.As the depth of extraction increases,the impact of elevated temperatures on the anisotropic shear strength and failure mechanisms of shale becomes pronounced,yet there is a notable lack of relevant research.This study conducts,for the first time,direct shear experiment on shales at four different temperatures and seven bedding angles.By employing acoustic emission(AE)and digital image correlation(DIC)techniques,the evolution of damage and the mechanism of crack propagation under anisotropic direct shearing at varying temperatures is revealed.The results indicate that both shear displacement and strength of shale increase with temperature across different bedding angles.Additionally,shale demonstrates distinct brittle failure characteristics under various conditions during direct shearing tests.The types of anisotropic shear failure observed under the influence of temperature include central shearing fracture,central shearing with secondary fracture,and deflected slip along the bedding.Moreover,the temperature effect enhances shear-induced crack propagation along bedding planes.Shear failure in shale predominantly occurs during higher loading stages,which coincide with a substantial amount of AE signals.Finally,the introduction of the anisotropy index and temperature sensitivity coefficient further elucidates the interaction mechanism between thermal effects and anisotropy.This study offers a novel methodology to explore the anisotropic shear failure behavior of shale under elevated temperatures,and also provides crucial theoretical and experimental insights into shear failure behavior relevant to practical shale reservoir stimulation.
基金supported by the Science Foundation of Hunan Province,China(No.2020JJ5215)Scientific Research Project of Hunan Provincial Department of Education,China(No.21B0594)the Open Fund of Hunan Key Laboratory of Electromagnetic Equipment Design and Manufacturing,China(No.DC202007)。
文摘Non-isothermal aging(NIA)is a composite heat treatment process that involves heating aging,cooling aging,and complex solute precipitation sequences.The precipitation behavior and the strengthening and toughening mechanisms of the 2014 Al alloy during NIA were studied by employing tensile,fatigue crack growth,hardness,and electronic conductivity tests,as well as high-resolution transmission electron microscopy and scanning electron microscopy.The results show that during NIA,theθ′phase exhibits a complex process of nucleation,nucleation and growth,nucleation and growth and coarsening,growth and coarsening,nucleation and growth,and nucleation.NIA treatment imparts a mixed precipitation characteristic on the alloy,which is manifested as coherent precipitates,including GP zones,θ′′phases,small-sizedθ′phases,and semi-coherent or non-coherent precipitates such as large-sizedθ′phases and equilibriumθphases.The simultaneous strengthening and toughening of the NIA-treated 2014 Al alloy is caused by the synergistic effects of the particle-shearing mechanism and Orowan bypassing mechanism.
基金supported by the National Key Research and Development Program of China(2020YFC1909104)National Natural Science Foundation of China(52274355)Major Science and Technology Project of Inner Mongolia Autonomous Region(2021ZD0016)。
文摘The Mountain Pass mine is recognized as one of the world's primary sources of rare earth minerals.These rare earth minerals mainly consist of bastnaesite and a small amount of monazite phosphate,which cannot be decomposed and recovered through conventional oxidative roasting and hydrochloric acid leaching process.An efficient,clean,and economical process called the"combined method"was proposed for the utilization of the Mountain Pass mine to extract rare earths from Mountain Pass rare earth concentrate(MPREC).The main steps of this process include weak oxidation atmosphere roasting,step leaching of hydrochloric acid,solid-liquid separation,the monazite slag with sulfuric acid roasting water leaching,etc.In this paper,the roasting process of MPREC under a weak oxidation atmosphere was investigated.The study examines the thermal decomposition kinetics,phase transition process,and leaching behavior of MPREC in air/CO_(2)atmosphere.Results show that,the activation energy(Ea)for MPREC thermal decomposition in air and CO_(2)atmosphere are 146 and 320 kJ/mol,respectively.At temperature above 500℃in air or above 700℃in CO_(2)atmosphere,REOF are generated from bastnaesite through an in-situ reaction with CaO,which is decomposed from CaCO_(3),to form CaF_(2)and rare earth oxide(REO).Thus,F is regulated into solid phase.In an oxidizing atmosphere,the thermal decomposition of bastnaesite is accompanied by the rapid oxidation of Ce(Ⅲ).In co ntrast,the oxidation of Ce(Ⅲ)in a CO_(2)atmosphere is significantly inhibited.At 700℃,the oxidation rate of Ce in air is 74.09%,while in a CO_(2)atmosphere,it is only 33.83%.The hydrochloric acid leaching experiment shows that,the leaching rate of rare earth after roasting at 600℃under an air atmosphere reaches to 82.9%,and it reaches 87%after roasting at 800℃under a CO_(2)atmosphere.The reduction of Ce oxidation in a weak oxidizing atmosphere significantly improves the leaching rate of Ce.
文摘Effective thermal management is paramount for successfully deploying lithium-ion batteries in residential settings as storage systems for the exploitation of renewable sources.Uncontrolled temperature increases within battery packs can lead to critical issues such as cell overheating,potentially culminating in thermal runaway events and,in extreme cases,leading to fire or explosions.Thiswork presents a comprehensive numerical thermalmodel of a battery pack made of prototype pouch cells based on lithium ferrophosphate(LFP)chemistry.The multi-physical model is specifically developed to investigate real-world operating scenarios and to assess safety considerations.The considered energy storage system is a battery designed for residential applications,in its integration with a photovoltaic(PV)installation.The actual electrochemical behavior of the prototype cell during the charging and discharging processes is modeled and validated on the ground of experimental data.The essential steps leading to the numerical schematization of the battery pack are then presented to apply themodel to two different use scenarios,differing for the user loads.The first scenario corresponds to a typical residential load,with standby lights being active during the night,solar generation with its peak at noon,and appliance use shifting in the afternoon and the evening.In the second scenario,a double demand for energy is present thatmakes the battery never reach 100%of the State of Charge(SoC)and dischargemore rapidly with respect to what occurs under the first scenario.Comparing the simulated temperature with the assumed C-rate,namely the charge or discharge current divided by the battery nominal capacity,it is found that peaks coincide with the charging phase;subsequently,the current tends to a zero value,and consequently,the temperature suddenly reaches the value of the environment.Finally,the model is also utilized to simulate a condition of thermal runaway by introducing critical conditions within a specific pouch cell.In this simulation,the thermal exchange between the cell in thermal runaway and the rest of the system remains within acceptable limits.This occurs due to the short duration of the process and to the module casing coated with an insulating material.The work provides an essential foundation for conducting numerical simulations of battery packs operating also at higher power levels.
基金funded by the Innovative Research Group project of the National Natural Science Foundation of China(52373003).
文摘This study investigates the long-term thermal-oxidative stability and mechanical properties of phenolcontaining phthalonitrile monomer(PN75)and dicyanate ester of bisphenol-A(DCBA)composites reinforced with short carbon fibers T700SC(SCF)within a temperature range of 330375℃.The research focuses on the PN75 monomer and DCBA blend reinforced SCF composites with varying SCF content,examining mass loss and changes in flexural strength after thermal aging for 50 h(h).Results show that the SCF-reinforced composites based on the PN75/DCBA blend consistently outperform the neat blend in flexural strength,both at room temperature and after thermal aging.The introduction of the SCF significantly improves the composites'thermal stability and mechanical retention,with higher SCF content correlating to better performance.Notably,after aging at 350℃,the SCF-reinforced composites based(30%(mass)SCF)retained 88.8%of its flexural strength,compared to 61.1%for the neat blend.Morphological analysis reveals that while thermal aging causes degradation of the PN75/DCBA blend layer on SCF surfaces,the overall composite structure maintains good mechanical properties up to 350℃.At 375℃,significant degradation occurs,yet the composites still retain flexural strengths above 78 MPa.This study demonstrates the potential of the SCF-reinforced composites based on PN75/DCBA blend for high-temperature applications,establishing their upper-temperature limit for long-term use in oxidative environments.
基金the support of the National Natural Science Foundation of China(Grant Nos.42030714,42177138 and 41907239).
文摘Investigation of thermal effects on the strain rate-dependent properties of compacted bentonite is crucial for the long-term safety assessment of deep geological repository for disposal of high-level radioactive waste.In the present work,cylindrical GMZ01 bentonite specimens were compacted with suction-controlled by the vapor equilibrium technique.Then,a series of temperature-and suction-controlled stepwise constant rate of strain(CRS)tests was performed and the rate-dependent compressibility behavior of the highly compacted GMZ01 bentonite was investigated.The plastic compressibility parameterλ,the elastic compressibility parameterκ,the yield stress p0,as well as the viscous parameterαwere determined.Results indicate thatλ,κandαdecrease and p0 increases as suction increases.Upon heating,parametersλ,αand p0 decrease.It is also found that p0 increases linearly with increasing CRS in a double-logarithm coordinate.Based on the experimental results,a viscosity parameterα(s,T)was fitted to capture the effects of suction s and temperature T on the relationship between yield stress and strain rate.Then,an elastic-thermo-viscoplastic model for unsaturated soils was developed to describe the thermal effects on the rate-dependent behavior of highly compacted GMZ01 bentonite.Validation showed that the calculated results agreed well to the measured ones.
基金supported by the Defense Indus-trial Technology Development Program(No.JCKY2020130C024)the National Key R&D Program of China(No.2021YFB3702503)+1 种基金the Science Center for Gas Turbine Project(No.P2022-C-Ⅳ-002-001)the National Science and Technology Major Project(No.Y2019-VII-0011-0151).
文摘In this study,a novel Ni-based superalloy,ZGH451,has been fabricated using direct energy deposition(DED).The thermal fatigue resistance of ZGH451 is systematically evaluated at 900,1000,and 1100℃,primarily focusing on the crack initiation and propagation behaviors.The results indicate that higher peak temperatures lead to earlier initiation and more rapid propagation of cracks.Cracks are initiated at the defects and grain boundaries in the vicinity of the notch,and different crack propagation mecha-nisms(γ'phase slip shearing,γ'phase distortion shearing,andγ'phase rafting shearing at 900,1000,and 1100℃,respectively)are the main reason for the different cracks propagation behaviors under the three temperatures.The main crack propagation paths are oriented at approximately 45°with respect to the build direction,suggesting activation of the{111}<110>slip system.Additionally,oxidation reduces the matrix strength and passivates the crack tips,leading to varying rates of crack propagation.At ele-vated temperatures,the synergistic effects of thermal stress and oxidative erosion are found to be the primary damage mechanisms of thermal fatigue.Overall,the proposed ZGH451 superalloy demonstrates exceptional thermal fatigue resistance,providing a crucial experimental reference for thermal fatigue in additively manufactured superalloys.
基金supported by the Natural Science Foundation of Shandong Province with grant No.ZR2023ME196the Science and Technology Support Plan for Young Innovation of Colleges and Universities of Shandong Province with grant No.2022KJ273+1 种基金the Youth Innovation Promotion Association of the Chinese Academy of Sciences with grant No.2017486the Patent Navigation Project of Shandong Province with grant No.D202327.
文摘In lead-cooled fast reactor(LFR)systems,the liquid lead-bismuth eutectic(LBE)coolant provides a cor-rosive environment that damages the steel components during high-temperature operation.This study investigated the microstructural deterioration of 9Cr ferritic/martensitic(F/M)steel under thermal aging at 550℃for 2,000,10,000,or 20,000 h and its effect on oxidation corrosion in an LBE environment using multiscale characterization techniques.The results indicated that the thickness of the internal oxidation zone(IOZ)increased significantly with extended thermal aging,whereas that of the spinel layer remained relatively constant.The abundant subgrain boundaries that emerged during extensive thermal aging facil-itated Fe diffusion,and the enlarged Cr-rich M23C6 carbides contributed to the formation of preferential oxidation regions,accelerating IOZ layer growth.The spinel layer formed from the IOZ was influenced by microstructural defects within the IOZ.A theoretical model describing the accelerated oxide layer growth due to thermal aging was developed.These findings support the advancement of LFR technology.
基金Project(22KJB430023)supported by the Natural Science Foundation for Colleges and Universities of Jiangsu Province,ChinaProject(1172922101)supported by the Youth Science and Technology Innovation Project of Jiangsu University of Science and Technology,China。
文摘The AlMgScZr high-strength aluminum alloy fabricated by selective laser melting(SLM)technology exhibits a“bimodal microstructure”,resulting in significant non-uniform deformation during thermal deformation.This study investigates the flow behavior of SLM-processed AlMgScZr aluminum alloy utilizing the Gleeble-1500D thermal simulation machine.The true stress-strain curves were amended based on the friction theory.Through determining the Zener-Hollomon parameters,the correlation between flow stress,deformation temperature,and strain rate during the high-temperature thermoplastic deformation of SLM-processed AlMgScZr aluminum alloy with a“bimodal microstructure”was established.In addition,the microstructural evolution during thermal deformation was analyzed.The results indicated that the predicted flow stress values obtained from the Arrhenius constitutive equation with coupled correction of thermal deformation parameters closely matched the experimental values.The correlation coefficient and the average absolute relative error of the corrected model were 0.999 and 2.766%,respectively,accurately predicting the thermoplastic deformation behavior of SLM-processed high-strength aluminum alloy with a“bimodal microstructure”.Furthermore,hot processing maps at different strains were established,identifying stable and unstable regions under different deformation conditions.Microstructural observations revealed different thermal deformation mechanisms under various deformation temperatures.Specifically,dynamic recrystallization characteristics dominated the microstructure at lower temperatures(300-360℃),while dynamic recovery was dominant at higher temperatures(390-500℃).
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.
基金National Key Research and Development Program of China(2021YFB3704103)National Natural Science Foundation of China(51571191)。
文摘The influence of Hf on the precipitation behavior of γ'phase and the subsequent tensile properties of a Ni-Cr-Mo alloy after long-term thermal exposure was investigated.The results reveal that the addition of Hf increases the average diameter ofγ'phases after thermal exposure at 700℃ for 5000 h,which enhances the critical resolved shear stress required for dislocations to shear the γ'phases in the Ni-Cr-Mo alloy.Simultaneously,element Hf incorporated into the γ'phases increases the lattice mismatch between the γ'and γ phase,thereby strengthening the coherency strengthening effect.These two factors collectively contribute to the enhanced strength of the alloy.Thus,Hf alloying effectively improves the yield strength of the Ni-Cr-Mo alloy after thermal exposure at 700℃.
