采用非平衡分子动力学模拟的方法探究了石墨烯层数对石墨烯/聚乙烯复合材料界面热导的影响。结果表明,随着石墨烯层数的增大,界面热导呈现较小的增长趋势。通过分析石墨烯碳原子与聚乙烯碳原子间的振动能谱(vibration power spectra,VPS...采用非平衡分子动力学模拟的方法探究了石墨烯层数对石墨烯/聚乙烯复合材料界面热导的影响。结果表明,随着石墨烯层数的增大,界面热导呈现较小的增长趋势。通过分析石墨烯碳原子与聚乙烯碳原子间的振动能谱(vibration power spectra,VPS)探究了石墨烯层数影响的内在机理。结果发现,石墨烯碳原子低频范围(<50THz)的振动模式主要影响界面的热传输。展开更多
With the increasing demand for petroleum,shale oil with considerable reserves has become an important part of global oil resources.The shale oil reservoir has a large number of nanopores and a complicated mineral comp...With the increasing demand for petroleum,shale oil with considerable reserves has become an important part of global oil resources.The shale oil reservoir has a large number of nanopores and a complicated mineral composition,and the effect of nanopore confinement and pore type usually makes the effective development of shale oil challenging.For a shale oil reservoir,CO_(2) flooding can effectively reduce the oil viscosity and improve the reservoir properties,which can thus improve the recovery performance.In this study,the method of non-equilibrium molecular dynamics(NEMD)simulation is used to simulate the CO_(2) flooding process in the nanoscale pores of shale oil reservoir.The performance difference between the organic kerogen slit nanopore and four types of inorganic nanopores is discussed.Thus,the effects of nanopore type and displacement velocity on the nanoscale displacement behavior of CO_(2) are analyzed.Results indicate that the CO_(2) flooding process of different inorganic pores is different.In comparison,the displacement efficiency of light oil components is higher,and the transport distance is longer.The intermolecular interaction can significantly affect the CO_(2) displacement behavior in nanopores.The CO_(2) displacement efficiency is shown as montmorillonite,feldspar>quartz>calcite>kerogen.On the other hand,it is found that a lower displacement velocity can benefit the miscibility process between alkane and CO_(2),which is conducive to the overall displacement process of CO_(2).The displacement efficiency can significantly decrease with the increase in displacement velocity.But once the displacement velocity is very high,the strong driving force can promote the alkane to move forward,and the displacement efficiency will recover slightly.This study further reveals the microscopic oil displacement mechanism of CO_(2) in shale nanopores,which is of great significance for the effective development of shale oil reservoirs by using the method of CO_(2) injection.展开更多
Previous experimental and computational results have confirmed that the thermal conductivity of a twodimensional(2D) material can be considerably affected by strain. Numerous attention has been paid to explore the rel...Previous experimental and computational results have confirmed that the thermal conductivity of a twodimensional(2D) material can be considerably affected by strain. Numerous attention has been paid to explore the relevant mechanisms. However, the strain effects on the interfacial thermal conductance(ITC) of 2D heterostructure have attracted little attention. Herein, the non-equilibrium molecular dynamics(NEMD) simulations were conducted to the graphene/hexagonal boron nitride(GR/h-BN) heterostructure to investigate the strain effects on the ITC. Three types of strains were considered, i.e., tensile strain, compressive strain, and shear strain.The results indicate that the strain can adjust the ITC for the GR/h-BN heterostructure effectively, and the strain loading direction also influences the ITC. Generally, the tensile strain reduces the ITC of the heterostructure, in addition to the BN-C system at small tensile strain;both the compressive strain and shear strain increase the ITC,especially at a small strain. For the NB-C system, it is more sensitive to the strain loading direction and the yx shear strain of 0.06 is the most effective way to strengthen the ITC. Our results also show that the out-of-plane deformation weakens the in-plane vibration of atoms, leading to a reduction of the interfacial thermal energy transport.展开更多
Probing the ideal limit of interfacial thermal conductance(ITC)in two-dimensional(2D)heterointerfaces is of paramount importance for assessing heat dissipation in 2D-based nanoelectronics.Using graphene/hexagonal boro...Probing the ideal limit of interfacial thermal conductance(ITC)in two-dimensional(2D)heterointerfaces is of paramount importance for assessing heat dissipation in 2D-based nanoelectronics.Using graphene/hexagonal boron nitride(Gr/h-BN),a structurally isomorphous heterostructure with minimal mass contrast,as a prototype,wedevelop an accurate yet highly efficient machine-learned potential(MLP)model,which drives nonequilibrium molecular dynamics(NEMD)simulations on a realistically large systemwith over 300,000 atoms,enabling us to report the ideal limit range of ITC for 2D heterostructures at room temperature.We further unveil an intriguing stackingsequence-dependent ITC hierarchy in the Gr/h-BN heterostructure,which can be connected to moirépatterns and is likely universal in van der Waals layered materials.The underlying atomic-level mechanisms can be succinctly summarized as energy-favorable stacking sequences facilitating outof-plane phonon energy transmission.This work demonstrates that MLP-driven MD simulations can serve as a new paradigm for probing and understanding thermal transport mechanisms in 2D heterostructures and other layered materials.展开更多
文摘采用非平衡分子动力学模拟的方法探究了石墨烯层数对石墨烯/聚乙烯复合材料界面热导的影响。结果表明,随着石墨烯层数的增大,界面热导呈现较小的增长趋势。通过分析石墨烯碳原子与聚乙烯碳原子间的振动能谱(vibration power spectra,VPS)探究了石墨烯层数影响的内在机理。结果发现,石墨烯碳原子低频范围(<50THz)的振动模式主要影响界面的热传输。
基金supported by the National Natural Science Foundation of China(No.52004303)Beijing Natural Science Foundation(No.3212020).
文摘With the increasing demand for petroleum,shale oil with considerable reserves has become an important part of global oil resources.The shale oil reservoir has a large number of nanopores and a complicated mineral composition,and the effect of nanopore confinement and pore type usually makes the effective development of shale oil challenging.For a shale oil reservoir,CO_(2) flooding can effectively reduce the oil viscosity and improve the reservoir properties,which can thus improve the recovery performance.In this study,the method of non-equilibrium molecular dynamics(NEMD)simulation is used to simulate the CO_(2) flooding process in the nanoscale pores of shale oil reservoir.The performance difference between the organic kerogen slit nanopore and four types of inorganic nanopores is discussed.Thus,the effects of nanopore type and displacement velocity on the nanoscale displacement behavior of CO_(2) are analyzed.Results indicate that the CO_(2) flooding process of different inorganic pores is different.In comparison,the displacement efficiency of light oil components is higher,and the transport distance is longer.The intermolecular interaction can significantly affect the CO_(2) displacement behavior in nanopores.The CO_(2) displacement efficiency is shown as montmorillonite,feldspar>quartz>calcite>kerogen.On the other hand,it is found that a lower displacement velocity can benefit the miscibility process between alkane and CO_(2),which is conducive to the overall displacement process of CO_(2).The displacement efficiency can significantly decrease with the increase in displacement velocity.But once the displacement velocity is very high,the strong driving force can promote the alkane to move forward,and the displacement efficiency will recover slightly.This study further reveals the microscopic oil displacement mechanism of CO_(2) in shale nanopores,which is of great significance for the effective development of shale oil reservoirs by using the method of CO_(2) injection.
基金funded by the National Natural Science Foundation of China (11902056, 11632004, 11902053, and U1864208)the National Key Research and Development Program of China (2018YFC1105800)+7 种基金the National Science and Technology Major Project (2017-VII-0011-0106)the Key Program for International Science and Technology Cooperation Projects of the Ministry of Science and Technology of China (2016YFE0125900)the Key Project of Natural Science Foundation of CQ CSTC (cstc2017jcyj BX0063)Science and Technology Planning Project of Tianjin (20ZYJDJC00030)Key Program of Research and Development of Hebei Province (202030507040009)the Fund for Innovative Research Groups of Natural Science Foundation of Hebei Province (A2020202002)the Key Project of Natural Science Foundation of Tianjin (S20ZDF077)the China Postdoctoral Science Foundation funded project (2019M653334 and 2020M680842)。
文摘Previous experimental and computational results have confirmed that the thermal conductivity of a twodimensional(2D) material can be considerably affected by strain. Numerous attention has been paid to explore the relevant mechanisms. However, the strain effects on the interfacial thermal conductance(ITC) of 2D heterostructure have attracted little attention. Herein, the non-equilibrium molecular dynamics(NEMD) simulations were conducted to the graphene/hexagonal boron nitride(GR/h-BN) heterostructure to investigate the strain effects on the ITC. Three types of strains were considered, i.e., tensile strain, compressive strain, and shear strain.The results indicate that the strain can adjust the ITC for the GR/h-BN heterostructure effectively, and the strain loading direction also influences the ITC. Generally, the tensile strain reduces the ITC of the heterostructure, in addition to the BN-C system at small tensile strain;both the compressive strain and shear strain increase the ITC,especially at a small strain. For the NB-C system, it is more sensitive to the strain loading direction and the yx shear strain of 0.06 is the most effective way to strengthen the ITC. Our results also show that the out-of-plane deformation weakens the in-plane vibration of atoms, leading to a reduction of the interfacial thermal energy transport.
基金support from the National Key R&D Program of China(Grant No.2022YFA1203100)the Research Grants Council of Hong Kong(Grant No.AoE/P-701/20)+3 种基金RGC GRF(No.14220022)T.L.sincerely thanks the Postgraduate Studentship from The Chinese University of Hong Kong.P.Y.is supported by the Israel Academy of Sciences and Humanities&the Council for Higher Education Excellence Fellowship Program for International Postdoctoral Researcherssupport from the National Natural Science Foundation of China(Nos.12472099 and 12102307)Z.Y.thanks the Stable Support Project of Shenzhen(No.20231122125728001).Some of the computations were conducted at the Supercomputing Center of Wuhan University.The authors also thank for the support of Open Source Supercomputing Center of S-A-I.
文摘Probing the ideal limit of interfacial thermal conductance(ITC)in two-dimensional(2D)heterointerfaces is of paramount importance for assessing heat dissipation in 2D-based nanoelectronics.Using graphene/hexagonal boron nitride(Gr/h-BN),a structurally isomorphous heterostructure with minimal mass contrast,as a prototype,wedevelop an accurate yet highly efficient machine-learned potential(MLP)model,which drives nonequilibrium molecular dynamics(NEMD)simulations on a realistically large systemwith over 300,000 atoms,enabling us to report the ideal limit range of ITC for 2D heterostructures at room temperature.We further unveil an intriguing stackingsequence-dependent ITC hierarchy in the Gr/h-BN heterostructure,which can be connected to moirépatterns and is likely universal in van der Waals layered materials.The underlying atomic-level mechanisms can be succinctly summarized as energy-favorable stacking sequences facilitating outof-plane phonon energy transmission.This work demonstrates that MLP-driven MD simulations can serve as a new paradigm for probing and understanding thermal transport mechanisms in 2D heterostructures and other layered materials.
