Determining the dynamics of adsorbed liquids on nanoporous materials is crucial for a detailed understanding of interactions and processes on the solid-liquid interface in many materials and porous systems.Knowledge o...Determining the dynamics of adsorbed liquids on nanoporous materials is crucial for a detailed understanding of interactions and processes on the solid-liquid interface in many materials and porous systems.Knowledge of the influence of the presence of paramagnetic species on the surface or within the porous matrices is essential for fundamental studies and industrial processes such as catalysts.Magnetic resonance methods,such as electron paramagnetic resonance(EPR),nuclear magnetic resonance(NMR)and dynamic nuclear polarization(DNP),are powerful tools to address these questions and to quantify dy-namics,electron-nuclear interaction features and their relation to the physical-chemical parameters of the system.This paper presents an NMR study of the dynamics of polar and nonpolar adsorbed liquids,represented by water,n-decane,deuterated water and nonane-d20,on the native silica surface as well as silica modified with vanadyl porphyrins.The analysis of the frequency dependence of the nuclear spin-lattice relaxation time is carried out by separating the intra-and intermolecular contributions,which were analyzed using reorientations mediated by translational displacements(RMTD)and force-free-hard-sphere(FFHS)models,respectively.展开更多
The micro structure and properties of as-cast Zr-2.5Nb-1X(X=Ru,Mo,Ta and Si) alloy are screened to explore novel biomedical zirconium alloys for magnetic resonance applications.Corresponding micro structure and phase ...The micro structure and properties of as-cast Zr-2.5Nb-1X(X=Ru,Mo,Ta and Si) alloy are screened to explore novel biomedical zirconium alloys for magnetic resonance applications.Corresponding micro structure and phase transformation were characterized using X-ray diffraction(XRD),scanning electron microscope(SEM)and transmission electron microscope(TEM).Hardness test,magnetic detection and electrochemical corrosion measurements are taken to present properties.The results show that all alloys consist of α-Zr,β-Zr and ω-Zr.α-Zr and β-Zr mainly exist in the form of parallel and intersecting plates,and nanoscale ω-Zr is dispersed in β-Zr plate.Especially,blocky ω-Zr with needle-like α-Zr is only found in plate-free blocks of Zr-2.5Nb-1Mo/Ru alloy.The orientation relationship(OR) between α-Zr and ω-Zr follows [1120]_α//[1101]_ω and(0001)_α//([1011]_ω 011)_ω.Combining this OR with the OR between β-Zr and ω-Zr,the transformation relationship between β-Zr/ω-Zr and α-Zr is also discussed.Zr-2.5Nb-1Ru alloy with high corrosion potential(-0.500 V),low corrosion rate(0.949 μm·year^(-1)) and low magnetic susceptibility(92×10^(-6)) shows great potential to be a novel biomedical implant with magnetic resonance imaging compatibility.Based on the experimental results,the possible relationship among alloying elements,micro structure and properties has been established in these Zr-2.5Nb-1X alloys.展开更多
The fatigue damage behavior of the nanocrystalline Au films on polyimide substrates was investigated.It was found that the very high-cycle fatigue damage resistance of the Au film was significantly enhanced by at leas...The fatigue damage behavior of the nanocrystalline Au films on polyimide substrates was investigated.It was found that the very high-cycle fatigue damage resistance of the Au film was significantly enhanced by at least a factor of~2 in supported loading through adding an ultrathin Ti interlayer at the Au film/polyimide interface.Such a better fatigue damage resistance is mainly ascribed to the effective suppression of voiding at the Au film/polyimide interface through modulation of the Au/Ti interface,and thus the propensity of the cyclic strain localization and grain boundary cracking is reduced.The finding may provide a potential strategy for the design of flexible devices with ultra-long fatigue life.展开更多
Observing the motion of electrons on their natural nanometer length and femtosecond time scales is a fundamental goal of and an open challenge for contemporary ultrafast science1–5.At present,optical techniques and e...Observing the motion of electrons on their natural nanometer length and femtosecond time scales is a fundamental goal of and an open challenge for contemporary ultrafast science1–5.At present,optical techniques and electron microscopy mostly provide either ultrahigh temporal or spatial resolution,and microscopy techniques with combined space-time resolution require further development6–11.In this study,we create an ultrafast electron source via plasmon nanofocusing on a sharp gold taper and implement this source in an ultrafast point-projection electron microscope.This source is used in an optical pump—electron probe experiment to study ultrafast photoemissions from a nanometer-sized plasmonic antenna12–15.We probe the real space motion of the photoemitted electrons with a 20-nm spatial resolution and a 25-fs time resolution and reveal the deflection of probe electrons by residual holes in the metal.This is a step toward time-resolved microscopy of electronic motion in nanostructures.展开更多
基金the Deutsche Forschungsgemeinschaft(STA 511/15e1 and-2)is gratefully acknowledged.
文摘Determining the dynamics of adsorbed liquids on nanoporous materials is crucial for a detailed understanding of interactions and processes on the solid-liquid interface in many materials and porous systems.Knowledge of the influence of the presence of paramagnetic species on the surface or within the porous matrices is essential for fundamental studies and industrial processes such as catalysts.Magnetic resonance methods,such as electron paramagnetic resonance(EPR),nuclear magnetic resonance(NMR)and dynamic nuclear polarization(DNP),are powerful tools to address these questions and to quantify dy-namics,electron-nuclear interaction features and their relation to the physical-chemical parameters of the system.This paper presents an NMR study of the dynamics of polar and nonpolar adsorbed liquids,represented by water,n-decane,deuterated water and nonane-d20,on the native silica surface as well as silica modified with vanadyl porphyrins.The analysis of the frequency dependence of the nuclear spin-lattice relaxation time is carried out by separating the intra-and intermolecular contributions,which were analyzed using reorientations mediated by translational displacements(RMTD)and force-free-hard-sphere(FFHS)models,respectively.
基金financially supported by the National Natural Science Foundation of China (No. 51421001)the Program of the Ministry of Education of China for Introducing Talents of Discipline to Universities (No. B16007)。
文摘The micro structure and properties of as-cast Zr-2.5Nb-1X(X=Ru,Mo,Ta and Si) alloy are screened to explore novel biomedical zirconium alloys for magnetic resonance applications.Corresponding micro structure and phase transformation were characterized using X-ray diffraction(XRD),scanning electron microscope(SEM)and transmission electron microscope(TEM).Hardness test,magnetic detection and electrochemical corrosion measurements are taken to present properties.The results show that all alloys consist of α-Zr,β-Zr and ω-Zr.α-Zr and β-Zr mainly exist in the form of parallel and intersecting plates,and nanoscale ω-Zr is dispersed in β-Zr plate.Especially,blocky ω-Zr with needle-like α-Zr is only found in plate-free blocks of Zr-2.5Nb-1Mo/Ru alloy.The orientation relationship(OR) between α-Zr and ω-Zr follows [1120]_α//[1101]_ω and(0001)_α//([1011]_ω 011)_ω.Combining this OR with the OR between β-Zr and ω-Zr,the transformation relationship between β-Zr/ω-Zr and α-Zr is also discussed.Zr-2.5Nb-1Ru alloy with high corrosion potential(-0.500 V),low corrosion rate(0.949 μm·year^(-1)) and low magnetic susceptibility(92×10^(-6)) shows great potential to be a novel biomedical implant with magnetic resonance imaging compatibility.Based on the experimental results,the possible relationship among alloying elements,micro structure and properties has been established in these Zr-2.5Nb-1X alloys.
基金supported by the National Natural Science Foundation of China(NSFC,Grant Nos.52071319,51601198 and 51771207)Foundation for Outstanding Young Scholar sponsored by Institute of Metal Research(IMR),Natural Science Foundation of Liaoning Province of China(20180510025)Foundation for Outstanding Young Scholar sponsored by the Shenyang National Laboratory for Materials Science(L2019F23)。
文摘The fatigue damage behavior of the nanocrystalline Au films on polyimide substrates was investigated.It was found that the very high-cycle fatigue damage resistance of the Au film was significantly enhanced by at least a factor of~2 in supported loading through adding an ultrathin Ti interlayer at the Au film/polyimide interface.Such a better fatigue damage resistance is mainly ascribed to the effective suppression of voiding at the Au film/polyimide interface through modulation of the Au/Ti interface,and thus the propensity of the cyclic strain localization and grain boundary cracking is reduced.The finding may provide a potential strategy for the design of flexible devices with ultra-long fatigue life.
基金the Deutsche Forschungsgemeinschaft for support within the priority program QUTIF(SPP1840)support from SPP1839,the German-Israeli Foundation(GIF grant no.1256)+2 种基金the Korea Foundation for International Cooperation of Science and Technology(Global Research Laboratory project,K20815000003)is acknowledgedthe HPC Cluster CARL in Oldenburg(DFG INST 184/157-1 FUGG)the Studienstiftung des Deutschen Volkes for the personal grant.
文摘Observing the motion of electrons on their natural nanometer length and femtosecond time scales is a fundamental goal of and an open challenge for contemporary ultrafast science1–5.At present,optical techniques and electron microscopy mostly provide either ultrahigh temporal or spatial resolution,and microscopy techniques with combined space-time resolution require further development6–11.In this study,we create an ultrafast electron source via plasmon nanofocusing on a sharp gold taper and implement this source in an ultrafast point-projection electron microscope.This source is used in an optical pump—electron probe experiment to study ultrafast photoemissions from a nanometer-sized plasmonic antenna12–15.We probe the real space motion of the photoemitted electrons with a 20-nm spatial resolution and a 25-fs time resolution and reveal the deflection of probe electrons by residual holes in the metal.This is a step toward time-resolved microscopy of electronic motion in nanostructures.
