Heat dissipation highly relies on the thermal conductivity(κ)of materials.Materials with large bandgaps and signifcant atomic mass ratios,such as BAs,SiC,andθ-TaN,have attracted considerable attention due to their p...Heat dissipation highly relies on the thermal conductivity(κ)of materials.Materials with large bandgaps and signifcant atomic mass ratios,such as BAs,SiC,andθ-TaN,have attracted considerable attention due to their potential for achieving ultra-highκ,with BAs serving as a particularly representative example due to its unique combination of large bandgap and high thermal conductivity.In this paper,the efects of atomic mass modifcation on phonon bandgap andκare systematically investigated using a BAs model,accounting for both three-and four-phonon scattering processes.A 20%increase inκcan be obtained by substituting B,achieved through widening the phonon bandgap,which suppresses phonon scattering.Notably,the AAOO four-phonon scattering channel is more suppressed than the AAO three-phonon channel,leading to an increased phonon lifetime(τ).For As,κcan also be enhanced by 5%when replaced by lighter atoms,such as^(69)As,primarily due to the increased phonon group velocity(υ).We systematically clarify how atomic-mass-induced bandgap variations afectτ,υ,and thereforeκin wide-bandgap systems.Our work provides a specifc scheme for further improving the ultra-highκof materials with large bandgaps,which possesses great guiding signifcance.展开更多
Reducing the thermal boundary resistance(TBR)is critical to enhance the thermal management efficiency and optimize the performance of electronic and thermoelectric devices.In this study,we employed non-equilibrium mol...Reducing the thermal boundary resistance(TBR)is critical to enhance the thermal management efficiency and optimize the performance of electronic and thermoelectric devices.In this study,we employed non-equilibrium molecular dynamics(NEMD)simulations using neuroevolution potential(NEP)machine learning models to investigate the impact of embedding nanoparticles in Si/Ge heterostructures on the TBR.Our results showed a significant reduction in the TBR.This was attributed to the enhanced phonon density of states matching via resonance,which promoted more efficient elastic phonon transport across the interface.However,this approach also led to a substantial increase in the bulk thermal resistance,highlighting a trade-off in which the overall heat dissipation is compromised.To address this,we investigated an alternative strategy in which a nanoparticle was positioned directly at the interface to modulate the interfacial modes,thereby improving the phonon transport efficiency without adversely affecting the bulk thermal properties.NEMD simulations validated this approach,showing a comparable TBR reduction,while mitigating the bulk thermal resistance increase observed with the resonance-based embedding method.This study offers valuable insights into resolving interfacial heat dissipation challenges and provides a balanced strategy for optimizing the thermal transport efficiency of nanoscale material systems.展开更多
Localization,one of the basic phenomena for wave transport,has been demonstrated to be an effective strategy to manipulate electronic,photonic,and acoustic properties of materials.Due to the wave nature of phonons,the...Localization,one of the basic phenomena for wave transport,has been demonstrated to be an effective strategy to manipulate electronic,photonic,and acoustic properties of materials.Due to the wave nature of phonons,the tuning of thermal properties through phonon localization would also be expected,which is beneficial to many applications such as thermoelectrics,electronics,and phononics.With the development of nanotechnology,nanostructures with characteristic length about ten nanometers can give rise to phonon localization,which has attracted considerable attention in recent years.This review aims to summarize recent advances with theoretical,simulative,and experimental studies toward understanding,prediction,and utilization of phonon localization in disordered nanostructures,focuses on the effect of phonon localization on thermal conductivity.Based on previous researches,perspectives regarding further researches to clarify this hecticinvestigated and immature topic and its exact effect on thermal transport are given.展开更多
Introducing porosity with different degrees of disorder has been widely used to regulate thermal properties of materials, which generally results in decrease of thermal conductivity. We investigate the thermal conduct...Introducing porosity with different degrees of disorder has been widely used to regulate thermal properties of materials, which generally results in decrease of thermal conductivity. We investigate the thermal conductivity of porous metamaterials in the ballistic transport region by using the Lorentz gas model. It is found that the introduction of asymmetry and Gaussian disorder into porous metamaterials can lead to a strong enhancement of thermal conductivity. By dividing the transport process into ballistic transport, non-ballistic transport, and unsuccessful transport processes, we find that the enhancement of thermal conductivity originates from the significant increase ballistic transport ratio. The findings enhance the understanding of ballistic thermal transport in porous materials and may facilitate designs of high-performance porous thermal metamaterials.展开更多
We study the mechanism of van der Waals(vdW)interactions on phonon transport in atomic scale,which would boost developments in heat management and energy conversion.Commonly,the vdW interactions are regarded as a hind...We study the mechanism of van der Waals(vdW)interactions on phonon transport in atomic scale,which would boost developments in heat management and energy conversion.Commonly,the vdW interactions are regarded as a hindrance in phonon transport.Here we propose that the vdW confinement can enhance phonon transport.Through molecular dynamics simulations,it is realized that the vdW confinement is able to make more than two-fold enhancement on thermal conductivity of both polyethylene single chain and graphene nanoribbon.The quantitative analyses of morphology,local vdW potential energy and dynamical properties are carried out to reveal the underlying physical mechanism.It is found that the confined vdW potential barriers reduce the atomic thermal displacement magnitudes,leading to less phonon scattering and facilitating thermal transport.Our study offers a new strategy to modulate the phonon transport.展开更多
An electrochemical vicinal heterodifunctionalization of olefins for the synthesis ofβ-oxysulfones is described.With suitable choice of the conditions,including current,electrodes,and electrolyte,this oxidation reacti...An electrochemical vicinal heterodifunctionalization of olefins for the synthesis ofβ-oxysulfones is described.With suitable choice of the conditions,including current,electrodes,and electrolyte,this oxidation reaction proceeded efficiently in an undivided cell without the use of a stoichiometric chemical oxidant.In addition to the previously established synthesis ofβ-hydroxysulfones in the presence of water,minor modification of this protocol by using either external alcohol nucleophiles or internal carboxylic acid nucleophile also led to the synthesis ofβ-alkoxysulfones,andβ-sulfonyl lactones.展开更多
With the hypothesis of simple units integration to create new reactivities,a strategy for the synthesis of polyfunctionalized 5-alkenyl-3-carbonylfurans fromγ-hydroxyl enal and 1,3-dicarbonyl compounds is established...With the hypothesis of simple units integration to create new reactivities,a strategy for the synthesis of polyfunctionalized 5-alkenyl-3-carbonylfurans fromγ-hydroxyl enal and 1,3-dicarbonyl compounds is established,featuring readily available starting materials,high efficiency,good functional groups compatibility,green chemistry with high atom economy and only water release,etc.,to provide a series of polyfunctionalized 5-alkenyl-3-carbonylfurans,which could be applied to the late-stage functionalization of naturally occurring compounds and bioactive molecules,as well as the transformation to pyrroles and polycyclic aromatic hydrocarbon via electrocyclic reaction.Theγ-hydroxyl has played an important role in the unexpected process of ring opening isomerization of 2H-pyran to furanones,as confirmed by detailed mechanistic studies.展开更多
An organocatalytic approach for direct conversion of racemic diarylmethanols to valuable chiral diarylmethyiamines is described. Ditterent from the previously reported elegant ＂borrowing hydrogen＂ approach, the pres...An organocatalytic approach for direct conversion of racemic diarylmethanols to valuable chiral diarylmethyiamines is described. Ditterent from the previously reported elegant ＂borrowing hydrogen＂ approach, the present process employs a distinct complementary formal SN 1 strategy. This approach enjoys excellent enantioselectivity, mild conditions, broad scope, and easy product derivatization. Mechanistically, control experiments also provided important insights into some notable features, such as substrate kinetic resolution and reversibility as well as the critical role of the ortho- hydroxy group in the substrate.展开更多
基金supported by the National Key Research and Development Program of China(Grant No.2023YFA1407001)the Department of Science and Technology of Jiangsu Province(Grant No.BK20220032)+1 种基金support from the Guang Dong Basic and Applied Basic Research Foundation(Grant No.2023A1515010365)support from the Postgraduate Research and Practice Innovation Program of Jiangsu Province under Grant No.KYCX25_1934。
文摘Heat dissipation highly relies on the thermal conductivity(κ)of materials.Materials with large bandgaps and signifcant atomic mass ratios,such as BAs,SiC,andθ-TaN,have attracted considerable attention due to their potential for achieving ultra-highκ,with BAs serving as a particularly representative example due to its unique combination of large bandgap and high thermal conductivity.In this paper,the efects of atomic mass modifcation on phonon bandgap andκare systematically investigated using a BAs model,accounting for both three-and four-phonon scattering processes.A 20%increase inκcan be obtained by substituting B,achieved through widening the phonon bandgap,which suppresses phonon scattering.Notably,the AAOO four-phonon scattering channel is more suppressed than the AAO three-phonon channel,leading to an increased phonon lifetime(τ).For As,κcan also be enhanced by 5%when replaced by lighter atoms,such as^(69)As,primarily due to the increased phonon group velocity(υ).We systematically clarify how atomic-mass-induced bandgap variations afectτ,υ,and thereforeκin wide-bandgap systems.Our work provides a specifc scheme for further improving the ultra-highκof materials with large bandgaps,which possesses great guiding signifcance.
基金supported in part by the National Natural Science Foundation of China(Grant No.12105242)the Yunnan Fundamental Research Project(Grant Nos.202201AT070161 and 202301AW070006)+2 种基金the Department of Science and Technology of Jiangsu Province(Grant No.BK20231279)the financial support provided by the Xing Dian Talent Programthe support provided by the Graduate Scientific Research and Innovation Fund of Yunnan University(KC-23234635)。
文摘Reducing the thermal boundary resistance(TBR)is critical to enhance the thermal management efficiency and optimize the performance of electronic and thermoelectric devices.In this study,we employed non-equilibrium molecular dynamics(NEMD)simulations using neuroevolution potential(NEP)machine learning models to investigate the impact of embedding nanoparticles in Si/Ge heterostructures on the TBR.Our results showed a significant reduction in the TBR.This was attributed to the enhanced phonon density of states matching via resonance,which promoted more efficient elastic phonon transport across the interface.However,this approach also led to a substantial increase in the bulk thermal resistance,highlighting a trade-off in which the overall heat dissipation is compromised.To address this,we investigated an alternative strategy in which a nanoparticle was positioned directly at the interface to modulate the interfacial modes,thereby improving the phonon transport efficiency without adversely affecting the bulk thermal properties.NEMD simulations validated this approach,showing a comparable TBR reduction,while mitigating the bulk thermal resistance increase observed with the resonance-based embedding method.This study offers valuable insights into resolving interfacial heat dissipation challenges and provides a balanced strategy for optimizing the thermal transport efficiency of nanoscale material systems.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11975125,11890703,and 21803031)the Natural Science Foundation of the Jiangsu Higher Education Institution of China(Grant No.18KJB150022)+1 种基金Postdoctoral Research Funding Program of Jiangsu,China(Grant No.2020Z163)China Postdoctoral Science Foundation(Grant No.2020M671533)。
文摘Localization,one of the basic phenomena for wave transport,has been demonstrated to be an effective strategy to manipulate electronic,photonic,and acoustic properties of materials.Due to the wave nature of phonons,the tuning of thermal properties through phonon localization would also be expected,which is beneficial to many applications such as thermoelectrics,electronics,and phononics.With the development of nanotechnology,nanostructures with characteristic length about ten nanometers can give rise to phonon localization,which has attracted considerable attention in recent years.This review aims to summarize recent advances with theoretical,simulative,and experimental studies toward understanding,prediction,and utilization of phonon localization in disordered nanostructures,focuses on the effect of phonon localization on thermal conductivity.Based on previous researches,perspectives regarding further researches to clarify this hecticinvestigated and immature topic and its exact effect on thermal transport are given.
基金supported by the National Natural Science Foundation of China (Grant Nos. 11975125 and 11890703)the Department of Science and Technology of Jiangsu Province (Grant No. BK20220032)。
文摘Introducing porosity with different degrees of disorder has been widely used to regulate thermal properties of materials, which generally results in decrease of thermal conductivity. We investigate the thermal conductivity of porous metamaterials in the ballistic transport region by using the Lorentz gas model. It is found that the introduction of asymmetry and Gaussian disorder into porous metamaterials can lead to a strong enhancement of thermal conductivity. By dividing the transport process into ballistic transport, non-ballistic transport, and unsuccessful transport processes, we find that the enhancement of thermal conductivity originates from the significant increase ballistic transport ratio. The findings enhance the understanding of ballistic thermal transport in porous materials and may facilitate designs of high-performance porous thermal metamaterials.
基金Supported by the National Natural Science Foundation of China(Grant Nos.51606072 and 51576077).
文摘We study the mechanism of van der Waals(vdW)interactions on phonon transport in atomic scale,which would boost developments in heat management and energy conversion.Commonly,the vdW interactions are regarded as a hindrance in phonon transport.Here we propose that the vdW confinement can enhance phonon transport.Through molecular dynamics simulations,it is realized that the vdW confinement is able to make more than two-fold enhancement on thermal conductivity of both polyethylene single chain and graphene nanoribbon.The quantitative analyses of morphology,local vdW potential energy and dynamical properties are carried out to reveal the underlying physical mechanism.It is found that the confined vdW potential barriers reduce the atomic thermal displacement magnitudes,leading to less phonon scattering and facilitating thermal transport.Our study offers a new strategy to modulate the phonon transport.
基金Financial support was provided by Hong Kong RGC (No. 16302318)Shenzhen Science and Technology Innovation Committee (No. JCYJ20170818113708560)HKUST (No. IEG17SC03)
文摘An electrochemical vicinal heterodifunctionalization of olefins for the synthesis ofβ-oxysulfones is described.With suitable choice of the conditions,including current,electrodes,and electrolyte,this oxidation reaction proceeded efficiently in an undivided cell without the use of a stoichiometric chemical oxidant.In addition to the previously established synthesis ofβ-hydroxysulfones in the presence of water,minor modification of this protocol by using either external alcohol nucleophiles or internal carboxylic acid nucleophile also led to the synthesis ofβ-alkoxysulfones,andβ-sulfonyl lactones.
基金Financial support from National Natural Science Foundation of China(Grant No.22201187)the starting grant from Capital Medical University(Grant No.3100-12400123)。
文摘With the hypothesis of simple units integration to create new reactivities,a strategy for the synthesis of polyfunctionalized 5-alkenyl-3-carbonylfurans fromγ-hydroxyl enal and 1,3-dicarbonyl compounds is established,featuring readily available starting materials,high efficiency,good functional groups compatibility,green chemistry with high atom economy and only water release,etc.,to provide a series of polyfunctionalized 5-alkenyl-3-carbonylfurans,which could be applied to the late-stage functionalization of naturally occurring compounds and bioactive molecules,as well as the transformation to pyrroles and polycyclic aromatic hydrocarbon via electrocyclic reaction.Theγ-hydroxyl has played an important role in the unexpected process of ring opening isomerization of 2H-pyran to furanones,as confirmed by detailed mechanistic studies.
文摘An organocatalytic approach for direct conversion of racemic diarylmethanols to valuable chiral diarylmethyiamines is described. Ditterent from the previously reported elegant ＂borrowing hydrogen＂ approach, the present process employs a distinct complementary formal SN 1 strategy. This approach enjoys excellent enantioselectivity, mild conditions, broad scope, and easy product derivatization. Mechanistically, control experiments also provided important insights into some notable features, such as substrate kinetic resolution and reversibility as well as the critical role of the ortho- hydroxy group in the substrate.
