The lattice thermal conductivity(κ_(latt))of mantle minerals plays a crucial role in the heat flow and temperature distribution within the Earth.MgSiO_(3)akimotoite is stable at the bottom of the mantle transition zo...The lattice thermal conductivity(κ_(latt))of mantle minerals plays a crucial role in the heat flow and temperature distribution within the Earth.MgSiO_(3)akimotoite is stable at the bottom of the mantle transition zone;it transitions to MgSiO_(3)perovskite(MgPv).Inκ_(latt)this work,we carry out a study of the of MgSiO_(3)akimotoite for pressures up to 25 GPa and temperatures up to 2500 K,based onκ_(latt)first-principles calculations combined with lattice dynamics theory.At 300 K and 25 GPa,the of MgSiO_(3)akimotoite is 37.66 W m^(-1)K^(-1),κ_(latt)larger than that of MgPv(13.46 W m^(-1)K^(-1)),which implies that the phase transition explains the reduction in.At 300 K,the pressureκ_(latt)κ_(latt)dependence of is 0.68 W m^(-1)K^(-1)GPa-1,stronger than that of MgPv(0.48 W m^(-1)K^(-1)GPa-1).The azimuthal anisotropy in of MgSiO_(3)akimotoite decreases from 45.5%at 0 GPa to 28.94%at 25 GPa,while the variation trend is opposite to that of MgPv.In MgSiO_(3)κ_(latt)akimotoite,Fe incorporating in the mineral leads to a decrease in and an increase in azimuthal anisotropy.Along the geotherm,theκ_(latt)of MgSiO_(3)akimotoite is lower than that of ringwoodite,which would suggest that MgSiO_(3)akimotoite slows down heat conduction at the bottom of mantle transition zone.These findings are useful for determining the thermal structure of,and understanding heat transfer in,the interior of the Earth.展开更多
The two-dimensional(2D)material-based thermal switch is attracting attention due to its novel applications,such as energy conversion and thermal management,in nanoscale devices.In this paper,we observed that the rever...The two-dimensional(2D)material-based thermal switch is attracting attention due to its novel applications,such as energy conversion and thermal management,in nanoscale devices.In this paper,we observed that the reversible 2H–1T′phase transition in MoTe_(2)is associated with about a fourfold/tenfold change in thermal conductivity along the X/Y direction by using first-principles calculations.This phenomenon can be profoundly understood by comparing the Mo–Te bonding strength between the two phases.The 2H-MoTe_(2)has one stronger bonding type,while 1T′-MoTe_(2)has three weaker types of bonds,suggesting bonding inhomogeneity in 1T′-MoTe_(2).Meanwhile,the bonding inhomogeneity can induce more scattering of vibration modes.The weaker bonding indicates a softer structure,resulting in lower phonon group velocity,a shorter phonon relaxation lifetime and larger Gr¨uneisen constants.The impact caused by the 2H to 1T′phase transition in MoTe_(2)hinders the propagation of phonons,thereby reducing thermal conductivity.Our study describes the possibility for the provision of the MoTe_(2)-based controllable and reversible thermal switch device.展开更多
Liquid metal gallium has been widely used in numerous fields, from nuclear engineering, catalysts, and energy storage to electronics owing to its remarkable thermal and electrical properties along with low viscosity a...Liquid metal gallium has been widely used in numerous fields, from nuclear engineering, catalysts, and energy storage to electronics owing to its remarkable thermal and electrical properties along with low viscosity and nontoxicity. Compared with high-temperature liquid metals, room-temperature liquid metals, such as gallium(Ga), are emerging as promising alternatives for fabricating advanced energy storage devices, such as phase change materials, by harvesting the advantageous properties of their liquid state maintained without external energy input. However, the thermal and electrical properties of liquid metals at the phase transition are rather poorly studied, limiting their practical applications. In this study, we reported on the physical properties of the solid–liquid phase transition of Ga using a custom-designed, solid–liquid electrical and thermal measurement system. We observed that the electrical conductivity of Ga progressively decreases with an increase in temperature. However, the Seebeck coefficient of Ga increases from 0.2 to 2.1 μV/K, and thermal conductivity from 7.6 to 33 W/(K·m). These electrical and thermal properties of Ga at solid–liquid phase transition would be useful for practical applications.展开更多
Monolayer transition metal dichalcogenides can normally exist in several structural polymorphs with distinct electrical,optical,and catalytic properties.Effective control of the relative stability and transformation o...Monolayer transition metal dichalcogenides can normally exist in several structural polymorphs with distinct electrical,optical,and catalytic properties.Effective control of the relative stability and transformation of different phases in these materials is thus of critical importance for applications.Using density functional theory calculations,we investigate the effects of low-work-function metal substrates including Ti,Zr,and Hf on the structural,electronic,and catalytic properties of monolayer MoS_(2) and WS_(2).The results indicate that such substrates not only convert the energetically stable structure from the 1H phase to the 1T'/1T phase,but also significantly reduce the kinetic barriers of the phase transformation.Furthermore,our calculations also indicate that the 1T' phase of MoS_(2) with Zr or Hf substrate is a potential catalyst for the hydrogen evolution reaction.展开更多
The emergence of MAX borides as well as MAB phases attracted great attention because of the renewable developments of ternary ceramics and offering great opportunities in potential applications.However,the number of b...The emergence of MAX borides as well as MAB phases attracted great attention because of the renewable developments of ternary ceramics and offering great opportunities in potential applications.However,the number of borides remains limited,and further fundamental descriptions and detailed investigations on various properties are still lacking.In this report,we employ an integrated computational scheme that combines density functional theory with the evolutional algorithm to search for the favorable structures of P-and S-glued ternary borides terminated by Nb metal.We discover that the structures of 212-type,as e.g.Nb_(2)PB_(2)and Nb_(2)SB_(2),belong to the P6m2 space group,while those of 211-type,as e.g.Nb_(2)PB and Nb_(2)SB,prefer to crystallize in the P6_(3)/mmc space group,and the corresponding carbides Nb_(2)PC and Nb_(2)SC are also considered for the sake of completeness and comparative analsys.The predicted Nb_(2)PB_(2),Nb_(2)PB,Nb_(2)SB,Nb_(2)PC and Nb_(2)SC are energetically stable,as revealed by the negative formation energies and by the proposed reaction paths with respect to the most competing phases,as well as dynamically stable,as suggested by the non-imaginary phonon spectra.The thermal conductivities of the six materials show unusual behaviors,particularly for the acoustic and optical contributions,and are accompanied by a strong anisotropy.Most importantly,Nb_(2)PB_(2) is found to be an excellent thermal conductor with a total thermal conductivity of~65 W/(m K),while Nb_(2)SC is found to be an ultra-low thermal conductor,with a total thermal conductivity of~5 W/(m K).These values are clearly outside the currently reported range of thermal conductivities,which makes Nb_(2)PB_(2)and Nb_(2)SC extremely interesting for fundamental research as well as prospective applications with the aid of artificial tunings on the almost independent MB block and the A layer.The discovery of these novel materials is expected to contribute substantially to the rapid development of ternary ceramics and to accelerate attempts in the applicability of MAX phases for heat conduction.展开更多
Phase change materials(PCM)have evolved over time and gradually adapted to the emerging needs of society.Their excellent properties,such as high latent heat storage capacity and fast response time,have aroused tremend...Phase change materials(PCM)have evolved over time and gradually adapted to the emerging needs of society.Their excellent properties,such as high latent heat storage capacity and fast response time,have aroused tremendous interest in applications such as thermal management systems,building energy efficiency,communications,and power.However,drawbacks such as low thermal conductivity,susceptibility to leakage,and small latent heat of phase transition limit the practical application of PCM.In this work,an innovative wood derived carbon-carbon nanotubes-paraffin wax(WDC-CNTs-PW)phase change energy storage composite is prepared by the high-temperature carbonization process,injection chemical vapor deposition,and vacuum impregnation method.The enhanced thermal conductivity of WDC-CNTs-PW is mainly due to the three-dimensional porous structure of WDC and the homogeneous introduction of the thermally enhanced filler CNTs.The axial and radial thermal conductivities of WDC-CNTs-PW are 0.35 and 0.29 W·m^(-1)·K^(-1),respectively.The enthalpies of melting and crystallization of WDC-CNTs-PW are 142.02 and 136.14 J·g^(-1),respectively,with impregnation efficiency of 70.95% and loading ratio of 73.01%.With excellent thermal conductivity,latent heat of phase transition,and encapsulation property,WDC-CNTs-PW opens up a surprising strategy for PCM applications in areas such as high technology microelectronics and energy-saving in houses.展开更多
Natural gas-hydrates are valuable energy resource with rich deposits,and their thermal transport and thermal dynamic mechanical behaviors significantly affect the long-term production process and phase change-based th...Natural gas-hydrates are valuable energy resource with rich deposits,and their thermal transport and thermal dynamic mechanical behaviors significantly affect the long-term production process and phase change-based thermal energy storage characteristics of these energy resources.This paper aims to propose novel relations to predict the thermophysical properties,to investigate the hydrate phase evolution in microstructures,and to study the thermal transport and thermal dynamic mechanical properties.Hydrates formation experiments in sandpack samples and ultrasonic wave tests are conducted with the aid of X-ray CT imaging.Digitalization microstructures models and variables are defined to describe the hydrate phase evolution,and novel relations are proposed to accurately predict the thermophysical properties based on the microporosity and ultrasonic wave velocities.The thermal transport and thermal dynamic mechanical properties in microstructures with hydrate,water,residuary pore and grain phases are studied.Results show that the average errors of porosity,P-wave and S-wave velocities between the experimental data and computed results by the proposed relations are less than 5%,indicating the accuracy and reliability of the proposed method.The temperature fraction decreases with increasing underground temperature and decreasing hydrate saturation.The thermal stress and thermal displacement increase as temperature and hydrate saturation increase.There are strong anisotropy for the temperature fraction,thermal stress and thermal displacement during the thermal transport of hydrates.展开更多
Barocaloric materials have attracted extensive attention for their promising applications in low-carbon refrigeration technology.Given that the performances of barocaloric materials are intrinsically and even inversel...Barocaloric materials have attracted extensive attention for their promising applications in low-carbon refrigeration technology.Given that the performances of barocaloric materials are intrinsically and even inversely correlated,an overall trade-off is necessitated.Here,we have prepared the 1-bromoadamantanegraphene composite(15 wt.%graphene),whose pressure-induced entropy change,pressure-induced adiabatic temperature change,and thermal hysteresis nearly remain unchanged.The pressure-induced adiabatic temperature change is comparable to the prototype neopentylglycol while the thermal hysteresis is much smaller.More importantly,by incorporating the additive the thermal conductivity has been elevated by 10 times.Such a combination renders the composite state-of-the-art barocaloric performances and is expected to benefit the design of barocaloric refrigeration technology.展开更多
基金supported by the National Natural Science Foundation of China(Nos.41474067,12174352).
文摘The lattice thermal conductivity(κ_(latt))of mantle minerals plays a crucial role in the heat flow and temperature distribution within the Earth.MgSiO_(3)akimotoite is stable at the bottom of the mantle transition zone;it transitions to MgSiO_(3)perovskite(MgPv).Inκ_(latt)this work,we carry out a study of the of MgSiO_(3)akimotoite for pressures up to 25 GPa and temperatures up to 2500 K,based onκ_(latt)first-principles calculations combined with lattice dynamics theory.At 300 K and 25 GPa,the of MgSiO_(3)akimotoite is 37.66 W m^(-1)K^(-1),κ_(latt)larger than that of MgPv(13.46 W m^(-1)K^(-1)),which implies that the phase transition explains the reduction in.At 300 K,the pressureκ_(latt)κ_(latt)dependence of is 0.68 W m^(-1)K^(-1)GPa-1,stronger than that of MgPv(0.48 W m^(-1)K^(-1)GPa-1).The azimuthal anisotropy in of MgSiO_(3)akimotoite decreases from 45.5%at 0 GPa to 28.94%at 25 GPa,while the variation trend is opposite to that of MgPv.In MgSiO_(3)κ_(latt)akimotoite,Fe incorporating in the mineral leads to a decrease in and an increase in azimuthal anisotropy.Along the geotherm,theκ_(latt)of MgSiO_(3)akimotoite is lower than that of ringwoodite,which would suggest that MgSiO_(3)akimotoite slows down heat conduction at the bottom of mantle transition zone.These findings are useful for determining the thermal structure of,and understanding heat transfer in,the interior of the Earth.
基金the China Scholarship Council(Grant No.202107000030)RIE2020 Advanced Manufacturing and Engineering(AME)Programmatic(Grant No.A1898b0043)A*STAR Aerospace Programme(Grant No.M2115a0092)。
文摘The two-dimensional(2D)material-based thermal switch is attracting attention due to its novel applications,such as energy conversion and thermal management,in nanoscale devices.In this paper,we observed that the reversible 2H–1T′phase transition in MoTe_(2)is associated with about a fourfold/tenfold change in thermal conductivity along the X/Y direction by using first-principles calculations.This phenomenon can be profoundly understood by comparing the Mo–Te bonding strength between the two phases.The 2H-MoTe_(2)has one stronger bonding type,while 1T′-MoTe_(2)has three weaker types of bonds,suggesting bonding inhomogeneity in 1T′-MoTe_(2).Meanwhile,the bonding inhomogeneity can induce more scattering of vibration modes.The weaker bonding indicates a softer structure,resulting in lower phonon group velocity,a shorter phonon relaxation lifetime and larger Gr¨uneisen constants.The impact caused by the 2H to 1T′phase transition in MoTe_(2)hinders the propagation of phonons,thereby reducing thermal conductivity.Our study describes the possibility for the provision of the MoTe_(2)-based controllable and reversible thermal switch device.
基金the support provided by A*STAR and the Industry Alignment Fund through the Pharos “Hybrid thermoelectric materials for ambient applications” Program (No.1527200021)。
文摘Liquid metal gallium has been widely used in numerous fields, from nuclear engineering, catalysts, and energy storage to electronics owing to its remarkable thermal and electrical properties along with low viscosity and nontoxicity. Compared with high-temperature liquid metals, room-temperature liquid metals, such as gallium(Ga), are emerging as promising alternatives for fabricating advanced energy storage devices, such as phase change materials, by harvesting the advantageous properties of their liquid state maintained without external energy input. However, the thermal and electrical properties of liquid metals at the phase transition are rather poorly studied, limiting their practical applications. In this study, we reported on the physical properties of the solid–liquid phase transition of Ga using a custom-designed, solid–liquid electrical and thermal measurement system. We observed that the electrical conductivity of Ga progressively decreases with an increase in temperature. However, the Seebeck coefficient of Ga increases from 0.2 to 2.1 μV/K, and thermal conductivity from 7.6 to 33 W/(K·m). These electrical and thermal properties of Ga at solid–liquid phase transition would be useful for practical applications.
基金Project supported by the National Key Research and Development Program of China(Grant Nos.2017YFA0204904 and 2019YFA0210004)the Strategic Priority Research Program of the Chinese Academy of Sciences(Grant No.XDB30000000)the Fundamental Research Funds for the Central Universities,China(Grant No.WK3510000013).
文摘Monolayer transition metal dichalcogenides can normally exist in several structural polymorphs with distinct electrical,optical,and catalytic properties.Effective control of the relative stability and transformation of different phases in these materials is thus of critical importance for applications.Using density functional theory calculations,we investigate the effects of low-work-function metal substrates including Ti,Zr,and Hf on the structural,electronic,and catalytic properties of monolayer MoS_(2) and WS_(2).The results indicate that such substrates not only convert the energetically stable structure from the 1H phase to the 1T'/1T phase,but also significantly reduce the kinetic barriers of the phase transformation.Furthermore,our calculations also indicate that the 1T' phase of MoS_(2) with Zr or Hf substrate is a potential catalyst for the hydrogen evolution reaction.
基金the National Natural Science Foundation of China(No.51902052)partially supported by“the Fundamental Research Funds for the Central Universities”+1 种基金supported by appointments to the JRG program at the APCTP through the Science and Technology Promotion Fund and Lottery Fund of the Korean Government,the Korean Local Governments,Gyeongsangbuk-do Province and Pohang Citypartially funded by the Swedish Research Council through grant agreement no.2018-05973 for providing the facility support on the numerical calculations in this paper。
文摘The emergence of MAX borides as well as MAB phases attracted great attention because of the renewable developments of ternary ceramics and offering great opportunities in potential applications.However,the number of borides remains limited,and further fundamental descriptions and detailed investigations on various properties are still lacking.In this report,we employ an integrated computational scheme that combines density functional theory with the evolutional algorithm to search for the favorable structures of P-and S-glued ternary borides terminated by Nb metal.We discover that the structures of 212-type,as e.g.Nb_(2)PB_(2)and Nb_(2)SB_(2),belong to the P6m2 space group,while those of 211-type,as e.g.Nb_(2)PB and Nb_(2)SB,prefer to crystallize in the P6_(3)/mmc space group,and the corresponding carbides Nb_(2)PC and Nb_(2)SC are also considered for the sake of completeness and comparative analsys.The predicted Nb_(2)PB_(2),Nb_(2)PB,Nb_(2)SB,Nb_(2)PC and Nb_(2)SC are energetically stable,as revealed by the negative formation energies and by the proposed reaction paths with respect to the most competing phases,as well as dynamically stable,as suggested by the non-imaginary phonon spectra.The thermal conductivities of the six materials show unusual behaviors,particularly for the acoustic and optical contributions,and are accompanied by a strong anisotropy.Most importantly,Nb_(2)PB_(2) is found to be an excellent thermal conductor with a total thermal conductivity of~65 W/(m K),while Nb_(2)SC is found to be an ultra-low thermal conductor,with a total thermal conductivity of~5 W/(m K).These values are clearly outside the currently reported range of thermal conductivities,which makes Nb_(2)PB_(2)and Nb_(2)SC extremely interesting for fundamental research as well as prospective applications with the aid of artificial tunings on the almost independent MB block and the A layer.The discovery of these novel materials is expected to contribute substantially to the rapid development of ternary ceramics and to accelerate attempts in the applicability of MAX phases for heat conduction.
基金supported by the Key R&D Program of Shaanxi Province(No.2021ZDLGY14-04)the National Training Program of Innovation and Entrepreneurship for Undergraduates(No.XN2022023)the Joint Funds of the National Natural Science Foundation of China(No.U21B2067).
文摘Phase change materials(PCM)have evolved over time and gradually adapted to the emerging needs of society.Their excellent properties,such as high latent heat storage capacity and fast response time,have aroused tremendous interest in applications such as thermal management systems,building energy efficiency,communications,and power.However,drawbacks such as low thermal conductivity,susceptibility to leakage,and small latent heat of phase transition limit the practical application of PCM.In this work,an innovative wood derived carbon-carbon nanotubes-paraffin wax(WDC-CNTs-PW)phase change energy storage composite is prepared by the high-temperature carbonization process,injection chemical vapor deposition,and vacuum impregnation method.The enhanced thermal conductivity of WDC-CNTs-PW is mainly due to the three-dimensional porous structure of WDC and the homogeneous introduction of the thermally enhanced filler CNTs.The axial and radial thermal conductivities of WDC-CNTs-PW are 0.35 and 0.29 W·m^(-1)·K^(-1),respectively.The enthalpies of melting and crystallization of WDC-CNTs-PW are 142.02 and 136.14 J·g^(-1),respectively,with impregnation efficiency of 70.95% and loading ratio of 73.01%.With excellent thermal conductivity,latent heat of phase transition,and encapsulation property,WDC-CNTs-PW opens up a surprising strategy for PCM applications in areas such as high technology microelectronics and energy-saving in houses.
基金supported by the National Natural Science Foundation of China(Grant Nos.51839009 and 51679017)。
文摘Natural gas-hydrates are valuable energy resource with rich deposits,and their thermal transport and thermal dynamic mechanical behaviors significantly affect the long-term production process and phase change-based thermal energy storage characteristics of these energy resources.This paper aims to propose novel relations to predict the thermophysical properties,to investigate the hydrate phase evolution in microstructures,and to study the thermal transport and thermal dynamic mechanical properties.Hydrates formation experiments in sandpack samples and ultrasonic wave tests are conducted with the aid of X-ray CT imaging.Digitalization microstructures models and variables are defined to describe the hydrate phase evolution,and novel relations are proposed to accurately predict the thermophysical properties based on the microporosity and ultrasonic wave velocities.The thermal transport and thermal dynamic mechanical properties in microstructures with hydrate,water,residuary pore and grain phases are studied.Results show that the average errors of porosity,P-wave and S-wave velocities between the experimental data and computed results by the proposed relations are less than 5%,indicating the accuracy and reliability of the proposed method.The temperature fraction decreases with increasing underground temperature and decreasing hydrate saturation.The thermal stress and thermal displacement increase as temperature and hydrate saturation increase.There are strong anisotropy for the temperature fraction,thermal stress and thermal displacement during the thermal transport of hydrates.
基金financially supported by the Ministry of Science and Technology of China(No.2022YFE0109900)Key Research Program of Frontier Sciences of Chinese Academy of Sciences(No.ZDBS-LY-JSC002)+3 种基金the National Natural Science Foundation of China(Nos.52401253 and 52201029)the Natural Science Foundation of Liaoning Province(No.2024-BSBA-41)Postdoctoral Fellowship Program of China Postdoctoral Science Foundation(No.GZC20232741)Innovation Fund of Institute of Metal Research,CAS(No.2024-PY05).
文摘Barocaloric materials have attracted extensive attention for their promising applications in low-carbon refrigeration technology.Given that the performances of barocaloric materials are intrinsically and even inversely correlated,an overall trade-off is necessitated.Here,we have prepared the 1-bromoadamantanegraphene composite(15 wt.%graphene),whose pressure-induced entropy change,pressure-induced adiabatic temperature change,and thermal hysteresis nearly remain unchanged.The pressure-induced adiabatic temperature change is comparable to the prototype neopentylglycol while the thermal hysteresis is much smaller.More importantly,by incorporating the additive the thermal conductivity has been elevated by 10 times.Such a combination renders the composite state-of-the-art barocaloric performances and is expected to benefit the design of barocaloric refrigeration technology.
