Here,we study the hydride formation in a metastable Ti-33Zr-22Hf-11Ta(at.%)refractory high entropy alloy(RHEA).Deviating to non-equiatomic compositions of RHEAs promotes the formation of transformation-induced plastic...Here,we study the hydride formation in a metastable Ti-33Zr-22Hf-11Ta(at.%)refractory high entropy alloy(RHEA).Deviating to non-equiatomic compositions of RHEAs promotes the formation of transformation-induced plasticity where the body-centered cubic phase transforms to hexagonal close-packed(HCP)phase.It is found that the phase transformation capability assists the hydride formation due to the low solubility of hydrogen within the HCP phase.In this study,hydrogen is charged via electrochemical polishing and the corresponding phase transformation is activated in the metastable RHEAs.The newly formed HCP phase interacts with hydrogen to form a face-centered cubic hydride verified by electron energy loss spectroscopy.This work provides a primary exploration of the formation of compositionally complex metal hydrides in the metastable RHEAs,which are potential candidates for future hydrogen storage material design.展开更多
Magnesium-lithium alloys with high lithium content have been attracting significant attention because of their low density,high formability and corrosion resistance.These properties are dependent on the distribution o...Magnesium-lithium alloys with high lithium content have been attracting significant attention because of their low density,high formability and corrosion resistance.These properties are dependent on the distribution of lithium,which is difficult to map in the presence of magnesium.In this work,a ratio spectrum-imaging method with electron energy-loss spectroscopy(EELS)is demonstrated,which enables the mapping of lithium.In application to LAZ941(Mg-9Li-4Al-1Zn in wt.%),this technique revealed that a key precipitate in the microstructure,previously thought by some to be Mg_(17)Al_(12),is in fact rich in lithium.This result was corroborated with a structural investigation by high-angle annular dark-field scanning transmission electron microscopy(HAADF-STEM),showing this phase to be Al_(1-x)Zn_(x)Li,with x<<1.This work indicates the potential offered by this technique for mapping lithium in materials.展开更多
Clean energy innovation has triggered the development of single-atom catalysts(SACs)due to their excellent catalytic activity,high tunability and low cost.The success of SACs for many catalytic reactions has opened a ...Clean energy innovation has triggered the development of single-atom catalysts(SACs)due to their excellent catalytic activity,high tunability and low cost.The success of SACs for many catalytic reactions has opened a new field,where the fundamentals of catalytic property-structure relationship at atomic level await exploration,and thus raises challenges for structural characterization.Among the characterization techniques for SACs,aberration-corrected transmission electron microscopy(TEM)has become an essential tool for direct visualization of single atoms.In this review,we briefly summarize recent studies on SACs using advanced TEM.We first introduce TEM methods,which are particularly important for SACs characterization,and then discuss the applications of advanced TEM for SAC characterization,where not only atomic dispersion of single atoms can be studied,but also the distribution of elements and the valence state with local coordination can be resolved.We further extend our review towards in-situ TEM,which has increasing importance for the fundamental understanding of catalytic mechanism.Perspectives of TEM for SACs are finally discussed.展开更多
A novel instrument that integrates reflection high energy electron diffraction(RHEED),electron energy loss spectroscopy(EELS),and imaging is designed and simulated.Since it can correlate the structural,elemental,and s...A novel instrument that integrates reflection high energy electron diffraction(RHEED),electron energy loss spectroscopy(EELS),and imaging is designed and simulated.Since it can correlate the structural,elemental,and spatial information of the same surface region via the simultaneously acquired patterns of RHEED,EELS,and energy-filtered electron microscopy,it is named correlative reflection electron microscopy(c-REM).Our simulation demonstrates that the spatial resolution of this c-REM is lower than 50 nm,which meets the requirements for in-situ monitoring the structural and chemical evolution of surface in advanced material.展开更多
Nanoscale plasmonic systems combine the advantages of optical frequencies with those of small spatial scales, circumventing the limitations of conventional photonic systems by exploiting the strong field confinement o...Nanoscale plasmonic systems combine the advantages of optical frequencies with those of small spatial scales, circumventing the limitations of conventional photonic systems by exploiting the strong field confinement of surface plasmons. As a result of this miniaturization to the nanoscale, electron microscopy techniques are the natural investigative methods of choice. Recent years have seen the development of a number of electron microscopy techniques that combine the use of electrons and photons to enable unprecedented views of surface plasmons in terms of combined spatial, energy, and time resolution. This review aims to provide a comparative survey of these different approaches from an experimental viewpoint by outlining their respective experimental domains of suitability and highlighting their complementary strengths and limitations as applied to plasmonics in particular.展开更多
Noble metallic nanostructures exhibit special optical properties resulting from excitation of surface plasmons. Among the various metallic nanostructures, nanorods have attracted particular attention because of their ...Noble metallic nanostructures exhibit special optical properties resulting from excitation of surface plasmons. Among the various metallic nanostructures, nanorods have attracted particular attention because of their unique and intriguing shape-dependent plasmonic properties. Nanorods can sup- port transverse and longitudinal plasmon modes, the latter ones depending strongly on the aspect ratio of the nanorod. These modes can be routinely tuned from the visible to the near-infrared spectral regions. Although nanorods have been investigated extensively, there are few studies de- voted to nanostructures deviating from the nanorod shape. This review provides an overview of recent progress in the development of two kinds of novel quasi-one-dimensional silver nanostruc- tures, nanorice and nanocarrot, including their syntheses, crystalline characterizations, plasmonic property analyses, and performance in plasmonic sensing applications.展开更多
In the present work, the synthesis of micro- and nano-sized spheres of metallic bismuth by microwave-assisted solvothermal method is reported. The synthesis method was carried out at different power levels and at a un...In the present work, the synthesis of micro- and nano-sized spheres of metallic bismuth by microwave-assisted solvothermal method is reported. The synthesis method was carried out at different power levels and at a unique frequency of microwave irradiation. The sphere sizes were controlled by the microwave power level and the concentration of dissolved precursor. Structural and morphological characterization was performed by SEM, HRTEM, EELS and XRD. The results demonstrated that rhombohedral zero valent Bi spheres were synthesized after microwave radiation at 600 and 1200 W. However, if the power level is decreased to 120 W, a monoclinic phase of Bi203 is obtained with a flake-like morphology. In comparison with a conventional hydrothermal process, the microwave-assisted solvothermal approach provides many advantages such as shorter reaction time, optimum manipulation of morphologies and provides a specific chemical phase and avoids the mixture of structural phases and morphologies which is essential for further applications such as drug delivery or functionalization with organic materials, thanks to its biocompatibility.展开更多
In this work the electronic structure and the impurity excess of the basal and rhombohedral twin grain boundaries are investigated, using electron energy loss spectroscopy (EELS) and energy dispersive X-ray spectrosco...In this work the electronic structure and the impurity excess of the basal and rhombohedral twin grain boundaries are investigated, using electron energy loss spectroscopy (EELS) and energy dispersive X-ray spectroscopy (EDXS). The measurability of electronic structures of the twin grain boundaries are discussed by comparing theoretical density of states (DOS) from bulk material with interfacial DOS, obtained from local density functional theory (LDFT) calculations.展开更多
基金W.J.Lu is grateful for financial support from the open research fund of Songshan Lake Materials Laboratory(No.2021SLABFK05)the Shenzhen Science and Technology Program(No.JCYJ20210324104404012).
文摘Here,we study the hydride formation in a metastable Ti-33Zr-22Hf-11Ta(at.%)refractory high entropy alloy(RHEA).Deviating to non-equiatomic compositions of RHEAs promotes the formation of transformation-induced plasticity where the body-centered cubic phase transforms to hexagonal close-packed(HCP)phase.It is found that the phase transformation capability assists the hydride formation due to the low solubility of hydrogen within the HCP phase.In this study,hydrogen is charged via electrochemical polishing and the corresponding phase transformation is activated in the metastable RHEAs.The newly formed HCP phase interacts with hydrogen to form a face-centered cubic hydride verified by electron energy loss spectroscopy.This work provides a primary exploration of the formation of compositionally complex metal hydrides in the metastable RHEAs,which are potential candidates for future hydrogen storage material design.
基金the Australian Research Council (ARC) for funding this work[Grant no.DP190103592]the use of instruments and scientific and technical assistance at the Monash Centre for Electron Microscopy,a Node of Microscopy Australiafunded by ARC grants LE110100223(F20),LE0454166(Titan)and LE170100118(Spectra-φ)。
文摘Magnesium-lithium alloys with high lithium content have been attracting significant attention because of their low density,high formability and corrosion resistance.These properties are dependent on the distribution of lithium,which is difficult to map in the presence of magnesium.In this work,a ratio spectrum-imaging method with electron energy-loss spectroscopy(EELS)is demonstrated,which enables the mapping of lithium.In application to LAZ941(Mg-9Li-4Al-1Zn in wt.%),this technique revealed that a key precipitate in the microstructure,previously thought by some to be Mg_(17)Al_(12),is in fact rich in lithium.This result was corroborated with a structural investigation by high-angle annular dark-field scanning transmission electron microscopy(HAADF-STEM),showing this phase to be Al_(1-x)Zn_(x)Li,with x<<1.This work indicates the potential offered by this technique for mapping lithium in materials.
基金National Natural Science Foundation of China(No.12074017)Beijing Municipal High Level Innovative Team Building Program,China(No.IDHT20190503)National Natural Science Fund for Innovative Research Groups of China(No.51621003).
文摘Clean energy innovation has triggered the development of single-atom catalysts(SACs)due to their excellent catalytic activity,high tunability and low cost.The success of SACs for many catalytic reactions has opened a new field,where the fundamentals of catalytic property-structure relationship at atomic level await exploration,and thus raises challenges for structural characterization.Among the characterization techniques for SACs,aberration-corrected transmission electron microscopy(TEM)has become an essential tool for direct visualization of single atoms.In this review,we briefly summarize recent studies on SACs using advanced TEM.We first introduce TEM methods,which are particularly important for SACs characterization,and then discuss the applications of advanced TEM for SAC characterization,where not only atomic dispersion of single atoms can be studied,but also the distribution of elements and the valence state with local coordination can be resolved.We further extend our review towards in-situ TEM,which has increasing importance for the fundamental understanding of catalytic mechanism.Perspectives of TEM for SACs are finally discussed.
基金Project supported by the Shanghai Tech University and the National Natural Science Foundation of China(Grant No.11774039)。
文摘A novel instrument that integrates reflection high energy electron diffraction(RHEED),electron energy loss spectroscopy(EELS),and imaging is designed and simulated.Since it can correlate the structural,elemental,and spatial information of the same surface region via the simultaneously acquired patterns of RHEED,EELS,and energy-filtered electron microscopy,it is named correlative reflection electron microscopy(c-REM).Our simulation demonstrates that the spatial resolution of this c-REM is lower than 50 nm,which meets the requirements for in-situ monitoring the structural and chemical evolution of surface in advanced material.
文摘Nanoscale plasmonic systems combine the advantages of optical frequencies with those of small spatial scales, circumventing the limitations of conventional photonic systems by exploiting the strong field confinement of surface plasmons. As a result of this miniaturization to the nanoscale, electron microscopy techniques are the natural investigative methods of choice. Recent years have seen the development of a number of electron microscopy techniques that combine the use of electrons and photons to enable unprecedented views of surface plasmons in terms of combined spatial, energy, and time resolution. This review aims to provide a comparative survey of these different approaches from an experimental viewpoint by outlining their respective experimental domains of suitability and highlighting their complementary strengths and limitations as applied to plasmonics in particular.
文摘Noble metallic nanostructures exhibit special optical properties resulting from excitation of surface plasmons. Among the various metallic nanostructures, nanorods have attracted particular attention because of their unique and intriguing shape-dependent plasmonic properties. Nanorods can sup- port transverse and longitudinal plasmon modes, the latter ones depending strongly on the aspect ratio of the nanorod. These modes can be routinely tuned from the visible to the near-infrared spectral regions. Although nanorods have been investigated extensively, there are few studies de- voted to nanostructures deviating from the nanorod shape. This review provides an overview of recent progress in the development of two kinds of novel quasi-one-dimensional silver nanostruc- tures, nanorice and nanocarrot, including their syntheses, crystalline characterizations, plasmonic property analyses, and performance in plasmonic sensing applications.
文摘In the present work, the synthesis of micro- and nano-sized spheres of metallic bismuth by microwave-assisted solvothermal method is reported. The synthesis method was carried out at different power levels and at a unique frequency of microwave irradiation. The sphere sizes were controlled by the microwave power level and the concentration of dissolved precursor. Structural and morphological characterization was performed by SEM, HRTEM, EELS and XRD. The results demonstrated that rhombohedral zero valent Bi spheres were synthesized after microwave radiation at 600 and 1200 W. However, if the power level is decreased to 120 W, a monoclinic phase of Bi203 is obtained with a flake-like morphology. In comparison with a conventional hydrothermal process, the microwave-assisted solvothermal approach provides many advantages such as shorter reaction time, optimum manipulation of morphologies and provides a specific chemical phase and avoids the mixture of structural phases and morphologies which is essential for further applications such as drug delivery or functionalization with organic materials, thanks to its biocompatibility.
文摘In this work the electronic structure and the impurity excess of the basal and rhombohedral twin grain boundaries are investigated, using electron energy loss spectroscopy (EELS) and energy dispersive X-ray spectroscopy (EDXS). The measurability of electronic structures of the twin grain boundaries are discussed by comparing theoretical density of states (DOS) from bulk material with interfacial DOS, obtained from local density functional theory (LDFT) calculations.
