The thermal conductivity of GaN nanofilm is simulated by using the molecular dynamics(MD)method to explore the influence of the nanofilm thickness and the pre-strain field under different temperatures.It is demonstrat...The thermal conductivity of GaN nanofilm is simulated by using the molecular dynamics(MD)method to explore the influence of the nanofilm thickness and the pre-strain field under different temperatures.It is demonstrated that the thermal conductivity of GaN nanofilm increases with the increase of nanofilm thickness,while decreases with the increase of temperature.Meanwhile,the thermal conductivity of strained GaN nanofilms is weakened with increasing the tensile strain.The film thickness and environment temperature can affect the strain effect on the thermal conductivity of GaN nanofilms.In addition,the analysis of phonon properties of GaN nanofilm shows that the phonon dispersion and density of states of GaN nanofilms can be significantly modified by the film thickness and strain.The results in this work can provide the theoretical supports for regulating the thermal properties of GaN nanofilm through tailoring the geometric size and strain engineering.展开更多
The recent studies on nanotwinned(NT)and hierarchical nanotwinned(HNT)face-centered cubic(FCC)metals are presented in this review.The HNT structures have been supposed as a kind of novel structure to bring about highe...The recent studies on nanotwinned(NT)and hierarchical nanotwinned(HNT)face-centered cubic(FCC)metals are presented in this review.The HNT structures have been supposed as a kind of novel structure to bring about higher strength/ductility than NT counterparts in crystalline materials.We primarily focus on the recent developments of the experimental,atomistic and theoretical studies on the NT and HNT structures in the metallic materials.Some advanced bottom-up and top-down techniques for the fabrication of NT and HNT structures are introduced.The deformation induced HNT structures are available by virtue of severe plastic deformation(SPD)based techniques while the synthesis of growth HNT structures is so far almost unavailable.In addition,some representative molecular dynamics(MD)studies on the NT and HNT FCC metals unveil that the nanoscale effects such as twin spacing,grain size and plastic anisotropy greatly alter the performance of NT and HNT metals.The HNT structures may initiate unique phenomena in comparison with the NT ones.Furthermore,based on the phenomena and mechanisms revealed by experimental and MD simulation observations,a series of theoretical models have been proposed.They are effective to describe the mechanical behaviors of NT and HNT metals within the applicable scope.So far the development of manufacturing technologies of HNT structures,as well as the studies on the effects of HNT structures on the properties of metals are still in its infancy.Further exploration is required to promote the design of advanced materials.展开更多
The construction of electrode materials for lithium-ion batteries(LIBs)and sodium-ion batteries(SIBs)has gradually been an appealing and attractive technology in energy storage research field.In the present work,a fac...The construction of electrode materials for lithium-ion batteries(LIBs)and sodium-ion batteries(SIBs)has gradually been an appealing and attractive technology in energy storage research field.In the present work,a facile strategy of synthesizing ultrathin amorphous/nanocrystal dual-phase P-doped Bi_(2)MoO_(6)(denoted as P-BiMO)nanosheets via a one-step wet-chemical synthesis approach is explored.Quite distinct from conventional two-dimensional(2D)nanosheets,our newly developed ultrathin P-BiMO nanosheets exhibit a unique tunable amorphous/nanocrystalline dual-phase structure with several compelling advantages including fast ion exchange ability and superb volume change buffer capability.The experimental results reveal that our prepared P-BiMO-6 electrode delivers an excellent reversible capacity of 509.6 mA·g^(−1) after continuous 1,500 cycles at the current densities of 1,500 mA·g^(−1) and improved rate performance for LIBs.In the meanwhile,the P-BiMO-6 electrode also shows a reversible capacity of 300.6 mA·g^(−1) after 100 cycles at 50 mA·g^(−1) when being used as the SIBs electrodes.This present work uncovers an effective dual-phase nanosheet structure to improve the performance of batteries,providing an attractive paradigm to develop superior electrode materials.展开更多
Super square(SS)carbon nanotube(CNT)networks,acting as a new kind of nanoporous membrane,manifest excellent water desalination performance.Nanopores in SS CNT network can efficiently filter NaCl from water.The water d...Super square(SS)carbon nanotube(CNT)networks,acting as a new kind of nanoporous membrane,manifest excellent water desalination performance.Nanopores in SS CNT network can efficiently filter NaCl from water.The water desalination ability of such nanoporous membranes critically depends on the pore diameter,permitting water molecule permeatration while salt ion obstruction.On the basis of the systematical analysis on the interaction among water permeability,salt concentration limit and pressure on the membranes,an empirical formula is developed to describe the relationship between pressure and concentration limit.In the meantime,the nonlinear relationship between pressure and water permeability is examined.Hence,by controlling pressure,optimal plan can be easily made to efficiently filter the saltwater.Moreover,steered molecular dynamics(MD)method uncovers bending and local buckling of SS CNT network that leads to salt ions passing through membranes.These important mechanical behaviours are neglected in most MD simulations,which may overestimate the filtration ability.Overall,water permeability of such material is several orders of magnitude higher than the conventional reverse osmosis membranes and several times higher than nanoporous graphene membranes.SS CNT networks may act as a new kind of membrane developed for water desalination with excellent filtration ability.展开更多
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11772294 and 11621062)the Fundamental Research Funds for the Central Universities(Grant No.2017QNA4031)。
文摘The thermal conductivity of GaN nanofilm is simulated by using the molecular dynamics(MD)method to explore the influence of the nanofilm thickness and the pre-strain field under different temperatures.It is demonstrated that the thermal conductivity of GaN nanofilm increases with the increase of nanofilm thickness,while decreases with the increase of temperature.Meanwhile,the thermal conductivity of strained GaN nanofilms is weakened with increasing the tensile strain.The film thickness and environment temperature can affect the strain effect on the thermal conductivity of GaN nanofilms.In addition,the analysis of phonon properties of GaN nanofilm shows that the phonon dispersion and density of states of GaN nanofilms can be significantly modified by the film thickness and strain.The results in this work can provide the theoretical supports for regulating the thermal properties of GaN nanofilm through tailoring the geometric size and strain engineering.
基金J.L.acknowledges the supports from the National Key R&D Program of China(Project No.2017YFA0204403)Research Grants Council of the Hong Kong Special Administrative Region(Grant No.CityU-11247516)+3 种基金the Hong Kong Collaborative Research Fund(CRF)Scheme(C4028-14G)Guangdong Science and Technology Department(Ref:2014B050504003)SZSTI(Ref:ZDSYS201602291653165)X.H.is grateful for the support from the Research Grants Council of the Hong Kong Special Administrative Region(Grant No.CityU-11204414).
文摘The recent studies on nanotwinned(NT)and hierarchical nanotwinned(HNT)face-centered cubic(FCC)metals are presented in this review.The HNT structures have been supposed as a kind of novel structure to bring about higher strength/ductility than NT counterparts in crystalline materials.We primarily focus on the recent developments of the experimental,atomistic and theoretical studies on the NT and HNT structures in the metallic materials.Some advanced bottom-up and top-down techniques for the fabrication of NT and HNT structures are introduced.The deformation induced HNT structures are available by virtue of severe plastic deformation(SPD)based techniques while the synthesis of growth HNT structures is so far almost unavailable.In addition,some representative molecular dynamics(MD)studies on the NT and HNT FCC metals unveil that the nanoscale effects such as twin spacing,grain size and plastic anisotropy greatly alter the performance of NT and HNT metals.The HNT structures may initiate unique phenomena in comparison with the NT ones.Furthermore,based on the phenomena and mechanisms revealed by experimental and MD simulation observations,a series of theoretical models have been proposed.They are effective to describe the mechanical behaviors of NT and HNT metals within the applicable scope.So far the development of manufacturing technologies of HNT structures,as well as the studies on the effects of HNT structures on the properties of metals are still in its infancy.Further exploration is required to promote the design of advanced materials.
基金supported by Shenzhen-Hong Kong Science and Technology Innovation Cooperation Zone Shenzhen Park Project:HZQB-KCZYB-2020030the National Key R&D Program of China(Project No.2017YFA0204403)Hong Kong Innovation and Technology Commission via the Hong Kong Branch of National Precious Metals Material Engineering Research Center.
文摘The construction of electrode materials for lithium-ion batteries(LIBs)and sodium-ion batteries(SIBs)has gradually been an appealing and attractive technology in energy storage research field.In the present work,a facile strategy of synthesizing ultrathin amorphous/nanocrystal dual-phase P-doped Bi_(2)MoO_(6)(denoted as P-BiMO)nanosheets via a one-step wet-chemical synthesis approach is explored.Quite distinct from conventional two-dimensional(2D)nanosheets,our newly developed ultrathin P-BiMO nanosheets exhibit a unique tunable amorphous/nanocrystalline dual-phase structure with several compelling advantages including fast ion exchange ability and superb volume change buffer capability.The experimental results reveal that our prepared P-BiMO-6 electrode delivers an excellent reversible capacity of 509.6 mA·g^(−1) after continuous 1,500 cycles at the current densities of 1,500 mA·g^(−1) and improved rate performance for LIBs.In the meanwhile,the P-BiMO-6 electrode also shows a reversible capacity of 300.6 mA·g^(−1) after 100 cycles at 50 mA·g^(−1) when being used as the SIBs electrodes.This present work uncovers an effective dual-phase nanosheet structure to improve the performance of batteries,providing an attractive paradigm to develop superior electrode materials.
基金the Research Grants Council of the Hong Kong Special Administrative Region of China under grants(CityU-114111)the financial supports provided by the Grant 2012CB932203the National Key Basic Research Program of the Chinese Ministry of Science and Technology and from the Croucher Foundation CityU9500006.
文摘Super square(SS)carbon nanotube(CNT)networks,acting as a new kind of nanoporous membrane,manifest excellent water desalination performance.Nanopores in SS CNT network can efficiently filter NaCl from water.The water desalination ability of such nanoporous membranes critically depends on the pore diameter,permitting water molecule permeatration while salt ion obstruction.On the basis of the systematical analysis on the interaction among water permeability,salt concentration limit and pressure on the membranes,an empirical formula is developed to describe the relationship between pressure and concentration limit.In the meantime,the nonlinear relationship between pressure and water permeability is examined.Hence,by controlling pressure,optimal plan can be easily made to efficiently filter the saltwater.Moreover,steered molecular dynamics(MD)method uncovers bending and local buckling of SS CNT network that leads to salt ions passing through membranes.These important mechanical behaviours are neglected in most MD simulations,which may overestimate the filtration ability.Overall,water permeability of such material is several orders of magnitude higher than the conventional reverse osmosis membranes and several times higher than nanoporous graphene membranes.SS CNT networks may act as a new kind of membrane developed for water desalination with excellent filtration ability.