The microstructural formation of the semi-solid AlSi7Mg alloy stirred by electromagnetic field is investigated together withthe tempeatre field of the stirred melt at continuously cooling. A impoat kinetic factor for ...The microstructural formation of the semi-solid AlSi7Mg alloy stirred by electromagnetic field is investigated together withthe tempeatre field of the stirred melt at continuously cooling. A impoat kinetic factor for primny a-Al nucleation is proposed. It isfound that a low temperatUre gradient exists in the electromagnetic stirred melt. This is why the first dendritic arms and secondary de-ndritic arms are refmed. Experimefltal results also show that the root remelting of secontw dendritic arms is an twortat mechanismfor the primary α-Al refmement. Strong electromagnetic stirring greatly reduces the composition supercooling in the melt and eliminatesprefedrig growth of the first dendritic arms. Therefore, many rosettes or spherical Primary α-Al phase particles form finally.展开更多
Recently, we achieved atomic-resolution optical imaging with near-field scanning optical microscopy using photon-induced force detection. In this technique, the surface photovoltage of the silicon-tip apex induced by ...Recently, we achieved atomic-resolution optical imaging with near-field scanning optical microscopy using photon-induced force detection. In this technique, the surface photovoltage of the silicon-tip apex induced by the optical near field on the surface is measured as the electrostatic force. We demonstrated atomicresolution imaging of the near field on the α-Al2O3 （0001） surface of a prism. We investigated the spatial distribution of the near field by scanning at different tip-sample distances and found that the atomic corrugation of the near-field signal was observed at greater distances than that of the atomic force microscopy signal. As the tip-sample distance increased, the normalized signal-to-noise ratio of the near field is in a gradual decline almost twice that of the frequency shift （Δf）.展开更多
In this paper,a modified formula forβk^PRP is proposed for the conjugate gradient method of solving unconstrained optimization problems.The value ofβk^PRP keeps nonnegative independent of the line search.Under mild ...In this paper,a modified formula forβk^PRP is proposed for the conjugate gradient method of solving unconstrained optimization problems.The value ofβk^PRP keeps nonnegative independent of the line search.Under mild conditions,the global convergence of modified PRP method with the strong Wolfe-Powell line search is established.Preliminary numerical results show that the modified method is efficient.展开更多
Probing CO at a specific site on a metal oxide surface is essential for characterizing various applications such as CO oxidation,hydrogenation,and water–gas shift reaction.Herein,we use atomic force microscopy and Ke...Probing CO at a specific site on a metal oxide surface is essential for characterizing various applications such as CO oxidation,hydrogenation,and water–gas shift reaction.Herein,we use atomic force microscopy and Kelvin probe force microscopy to probe the CO on a rutile TiO_(2)(110)surface.Our results indicate that CO can be manipulated along the Ti row by the repulsive lateral force of“pushing”mode.Furthermore,the joint combination of precise manipulation and the distance dependence of local contact potential difference allow us to resolve the interatomic dipole moment and charge state of CO at atomic resolution.Therefore,we found that the negatively charged CO with the dipole moment of negative pole down on the rutile TiO_(2)(110)surface.Our results suppose that both the charge state as well as the on-surface dipole interaction are very effective for CO reaction on rutile TiO_(2)(110)surface.展开更多
The common ways to activate a chemical reaction are by heat,electric current,or light.However,mechanochemistry,where the chemical reaction is activated by applied mechanical force,is less common and only poorly unders...The common ways to activate a chemical reaction are by heat,electric current,or light.However,mechanochemistry,where the chemical reaction is activated by applied mechanical force,is less common and only poorly understood at the atomic scale.Here we report a tip-induced activation of chemical reaction of carbon monoxide to dioxide on oxidized rutile TiO_(2)(110)surface.The activation is studied by atomic force microscopy,Kelvin probe force microscopy under ultrahigh-vacuum and liquid nitrogen temperature conditions,and density functional theory(DFT)modeling.The reaction is inferred from hysteretic behavior of frequency shift signal further supported by vector force mapping of vertical and lateral forces needed to trigger the chemical reaction with torque motion of carbon monoxide towards an oxygen adatom.The reaction is found to proceed stochastically at very small tip-sample distances.Furthermore,the local contact potential difference reveals the atomic-scale charge redistribution in the reactants required to unlock the reaction.Our results open up new insights into the mechanochemistry on metal oxide surfaces at the atomic scale.展开更多
Transition-metal chalcogenides(TMCs)materials have attracted increasing interest both for fundamental research and industrial applications.Among all these materials,two-dimensional(2D)compounds with honeycomb-like str...Transition-metal chalcogenides(TMCs)materials have attracted increasing interest both for fundamental research and industrial applications.Among all these materials,two-dimensional(2D)compounds with honeycomb-like structure possess exotic electronic structures.Here,we report a systematic study of TMC monolayer AgTe fabricated by direct depositing Te on the surface of Ag(111)and annealing.Few intrinsic defects are observed and studied by scanning tunneling microscopy,indicating that there are two kinds of AgTe domains and they can form gliding twin-boundary.Then,the monolayer AgTe can serve as the template for the following growth of Te film.Meanwhile,some Te atoms are observed in the form of chains on the top of the bottom Te film.Our findings in this work might provide insightful guide for the epitaxial growth of 2D materials for study of novel physical properties and for future quantum devices.展开更多
Nanocontact properties of two-dimensional(2D)materials are closely dependent on their unique nanomechanical systems,such as the number of atomic layers and the supporting substrate.Here,we report a direct observation ...Nanocontact properties of two-dimensional(2D)materials are closely dependent on their unique nanomechanical systems,such as the number of atomic layers and the supporting substrate.Here,we report a direct observation of toplayer-dependent crystallographic orientation imaging of 2D materials with the transverse shear microscopy(TSM).Three typical nanomechanical systems,MoS_(2) on the amorphous SiO_(2)/Si,graphene on the amorphous SiO_(2)/Si,and MoS_(2) on the crystallized Al_(2)O_(3),have been investigated in detail.This experimental observation reveals that puckering behaviour mainly occurs on the top layer of 2D materials,which is attributed to its direct contact adhesion with the AFM tip.Furthermore,the result of crystallographic orientation imaging of MoS_(2)/SiO_(2)/Si and MoS_(2)/Al_(2)O_(3) indicated that the underlying crystalline substrates almost do not contribute to the puckering effect of 2D materials.Our work directly revealed the top layer dependent puckering properties of 2D material,and demonstrate the general applications of TSM in the bilayer 2D systems.展开更多
文摘The microstructural formation of the semi-solid AlSi7Mg alloy stirred by electromagnetic field is investigated together withthe tempeatre field of the stirred melt at continuously cooling. A impoat kinetic factor for primny a-Al nucleation is proposed. It isfound that a low temperatUre gradient exists in the electromagnetic stirred melt. This is why the first dendritic arms and secondary de-ndritic arms are refmed. Experimefltal results also show that the root remelting of secontw dendritic arms is an twortat mechanismfor the primary α-Al refmement. Strong electromagnetic stirring greatly reduces the composition supercooling in the melt and eliminatesprefedrig growth of the first dendritic arms. Therefore, many rosettes or spherical Primary α-Al phase particles form finally.
文摘Recently, we achieved atomic-resolution optical imaging with near-field scanning optical microscopy using photon-induced force detection. In this technique, the surface photovoltage of the silicon-tip apex induced by the optical near field on the surface is measured as the electrostatic force. We demonstrated atomicresolution imaging of the near field on the α-Al2O3 （0001） surface of a prism. We investigated the spatial distribution of the near field by scanning at different tip-sample distances and found that the atomic corrugation of the near-field signal was observed at greater distances than that of the atomic force microscopy signal. As the tip-sample distance increased, the normalized signal-to-noise ratio of the near field is in a gradual decline almost twice that of the frequency shift （Δf）.
基金Supported by the National Natural Science Foundation of China(Grant No.10761001)
文摘In this paper,a modified formula forβk^PRP is proposed for the conjugate gradient method of solving unconstrained optimization problems.The value ofβk^PRP keeps nonnegative independent of the line search.Under mild conditions,the global convergence of modified PRP method with the strong Wolfe-Powell line search is established.Preliminary numerical results show that the modified method is efficient.
基金a Grant-in-Aid for Scientific Research from Japan Society for the Promotion of Science(JSPS)from the Ministry of Education,Culture,Sports,Science,and Technology of Japan(JP16H06327,JP16H06504,and JP17H01061)This work was also supported by the International Joint Research Promotion Program of Osaka University(J171013014,J171013007,and Ja19990011)This project was supported by the National Natural Science Foundation of China(NSFC)JSPS-NSFC(No.J191053055).
文摘Probing CO at a specific site on a metal oxide surface is essential for characterizing various applications such as CO oxidation,hydrogenation,and water–gas shift reaction.Herein,we use atomic force microscopy and Kelvin probe force microscopy to probe the CO on a rutile TiO_(2)(110)surface.Our results indicate that CO can be manipulated along the Ti row by the repulsive lateral force of“pushing”mode.Furthermore,the joint combination of precise manipulation and the distance dependence of local contact potential difference allow us to resolve the interatomic dipole moment and charge state of CO at atomic resolution.Therefore,we found that the negatively charged CO with the dipole moment of negative pole down on the rutile TiO_(2)(110)surface.Our results suppose that both the charge state as well as the on-surface dipole interaction are very effective for CO reaction on rutile TiO_(2)(110)surface.
基金supported by a Grant-in-Aid for Scientific Research from Japan Society for the Promotion of Science(JSPS)from the Ministry of Education,Culture,Sports,Science,and Technology of Japan(Nos.JP16H06327,JP17H01061,A21J103560,and JP22H00282)supported by the International Joint Research Promotion Program of Osaka University(Nos.J171013014,J171013007,J181013004,J181013006,Ja1999001,Ja19990011,and A21J103560)+1 种基金JSPSthe National Natural Science Foundation of China(No.J191053055)supported by APVV-21-0272,VEGA-2/0070/21,VEGA-2/0125/20,VEGA-2/0131/23,and H2020 TREX GA No.952165 projects。
文摘The common ways to activate a chemical reaction are by heat,electric current,or light.However,mechanochemistry,where the chemical reaction is activated by applied mechanical force,is less common and only poorly understood at the atomic scale.Here we report a tip-induced activation of chemical reaction of carbon monoxide to dioxide on oxidized rutile TiO_(2)(110)surface.The activation is studied by atomic force microscopy,Kelvin probe force microscopy under ultrahigh-vacuum and liquid nitrogen temperature conditions,and density functional theory(DFT)modeling.The reaction is inferred from hysteretic behavior of frequency shift signal further supported by vector force mapping of vertical and lateral forces needed to trigger the chemical reaction with torque motion of carbon monoxide towards an oxygen adatom.The reaction is found to proceed stochastically at very small tip-sample distances.Furthermore,the local contact potential difference reveals the atomic-scale charge redistribution in the reactants required to unlock the reaction.Our results open up new insights into the mechanochemistry on metal oxide surfaces at the atomic scale.
基金This project was supported by the Ministry of Science and Technology(MOST)of China(No.2016YFA0200700)the National Natural Science Foundation of China(NSFC)(Nos.61674045 and 61911540074)+2 种基金the Strategic Priority Research Program and Key Research Program of Frontier Sciences(Chinese Academy of Sciences,CAS)(Nos.XDB30000000 and QYZDB-SSW-SYS031)Grant-in-Aid for Scientific Research from Japan Society for the Promotion of Science(JSPS)from the Ministry of Education,Culture,Sports,Science,and Technology of Japan(Nos.JP16H06327,JP16H06504,JP17H01061,and JP17H010610)Osaka University’s International Joint Research Promotion Program(Nos.J171013014,J171013007,J181013006,and Ja19990011).Z.H.C.was supported by the Fundamental Research Funds for the Central Universities and the Research Funds of Renmin University of China(No.21XNLG27).
文摘Transition-metal chalcogenides(TMCs)materials have attracted increasing interest both for fundamental research and industrial applications.Among all these materials,two-dimensional(2D)compounds with honeycomb-like structure possess exotic electronic structures.Here,we report a systematic study of TMC monolayer AgTe fabricated by direct depositing Te on the surface of Ag(111)and annealing.Few intrinsic defects are observed and studied by scanning tunneling microscopy,indicating that there are two kinds of AgTe domains and they can form gliding twin-boundary.Then,the monolayer AgTe can serve as the template for the following growth of Te film.Meanwhile,some Te atoms are observed in the form of chains on the top of the bottom Te film.Our findings in this work might provide insightful guide for the epitaxial growth of 2D materials for study of novel physical properties and for future quantum devices.
基金This work was supported by the National Natural Science Foundation of China(NSFC,Grant Nos.21622304,61674045,and 11604063)Ministry of Science and Technology(MOST)of China(Grant No.2016YFA0200700)+5 种基金Strategic Priority Research Program,Key Research Program of Frontier Sciences and Instrument Developing Project of Chinese Academy of Sciences(CASGrant Nos.XDB30000000,QYZDB-SSW-SYS031,and YZ201418)Grant-in-Aid for Scientific Research from Japan Society for the Promotion of Science(JSPS)from the Ministry of Education,Culture,Sports,Science,and Technology of Japan(Grant Nos.JP16H06327,JP16H06504,JP17H01061,and JP17H010610)Osaka University’s International Joint Research Promotion Program(Grant Nos.J171013014,J171013007,J181013006,and Ja19990011)Z.H.Cheng was supported by Distinguished Technical Talents Project and Youth Innovation Promotion Association CAS,the Fundamental Research Funds for the Central Universities,and the Research Funds of Renmin University of China(Grant No.18XNLG01)S.Chen appreciate the support from Beijing Natural Science Foundation(Grant No.2192024).
文摘Nanocontact properties of two-dimensional(2D)materials are closely dependent on their unique nanomechanical systems,such as the number of atomic layers and the supporting substrate.Here,we report a direct observation of toplayer-dependent crystallographic orientation imaging of 2D materials with the transverse shear microscopy(TSM).Three typical nanomechanical systems,MoS_(2) on the amorphous SiO_(2)/Si,graphene on the amorphous SiO_(2)/Si,and MoS_(2) on the crystallized Al_(2)O_(3),have been investigated in detail.This experimental observation reveals that puckering behaviour mainly occurs on the top layer of 2D materials,which is attributed to its direct contact adhesion with the AFM tip.Furthermore,the result of crystallographic orientation imaging of MoS_(2)/SiO_(2)/Si and MoS_(2)/Al_(2)O_(3) indicated that the underlying crystalline substrates almost do not contribute to the puckering effect of 2D materials.Our work directly revealed the top layer dependent puckering properties of 2D material,and demonstrate the general applications of TSM in the bilayer 2D systems.
