Layered double hydroxides(LDHs) have attracted considerable attention as a cost effective alternative to the precious iridium-and ruthenium-based electrocatalysts for an oxygen evolution reaction(OER),a bottleneck of ...Layered double hydroxides(LDHs) have attracted considerable attention as a cost effective alternative to the precious iridium-and ruthenium-based electrocatalysts for an oxygen evolution reaction(OER),a bottleneck of water electrolysis for sustainable hydrogen production.Despite their excellent OER performance,the structural and electronic properties of LDHs,particularly during the OER process,remain to be poorly understood.In this study,a series of LDH catalysts is investigated through in situ X-ray absorption fine structure analyses and density functional theory(DFT) calculations.Our experimental results reveal that the LDH catalyst with equal amounts of Ni and Fe(NF-LDH) exhibits the highest OER activity and catalytic life span when compared with its counterparts having equal amounts of Ni and Co(NC-LDH)and Ni only(Ni-LDH).The NF-LDH shows a markedly enhanced OER kinetics compared to the NC-LDH and the Ni-LDH,as proven by the lower overpotentials of 180,240,and 310 mV,respectively,and the Tafel slopes of 35.1,43.4,and 62.7 mV dec^(-1),respectively.The DFT calculations demonstrate that the lowest overpotential of the NF-LDH is associated with the active sites located at the edge planes of NF-LDH in contrast to those located at the basal planes of Ni-LDH and NC-LDH.The current study pinpoints the active sites on various LDHs and presents strategies for optimizing the OER performance of the LDH catalysts.展开更多
The real contact area(RCA)of randomly rough contacts has received a great deal of attention because it correlates strongly with friction,lubrication,sealing,and conductivity.Simulations have revealed that the RCA asso...The real contact area(RCA)of randomly rough contacts has received a great deal of attention because it correlates strongly with friction,lubrication,sealing,and conductivity.Simulations have revealed that the RCA associated with deterministic normal squeezing loads increases when tangential loads are also applied,in a phenomenon called junction growth.However,experimental investigations of the junction growth of randomly rough contacts are rare.Here,we used X-ray computed tomography(CT)to measure junction growth when two aluminum alloy surfaces were in contact.A high-resolution experimental setup was used to apply loads and observe contact behaviors at a resolution of 4μm.The RCA and average contact gaps were computed using a three-dimensional(3D)geometric model constructed from gray CT images using the Otsu thresholding method.The results showed that the RCA increased as the normal load increased.The RCA increased by 22.67%after a tangential load was applied(junction growth),and the average gap decreased by 14.01%after a tangential load was applied.Thus,X-ray CT accurately measured the junction growth as a novel quantitative method.展开更多
Eight surface sabkha soils samples were collected from Ismailia—Suez roadbed, southwestern of Suez Canal district. Sedimentological and mineralogical analyses were conducted using grain size;X-ray diffraction and Sca...Eight surface sabkha soils samples were collected from Ismailia—Suez roadbed, southwestern of Suez Canal district. Sedimentological and mineralogical analyses were conducted using grain size;X-ray diffraction and Scanning Electron Microscopy (SEM). Grain size analysis indicates high contents of fine sand and mud as well as presence of salts. X-ray diffraction;Scanning Electron Microscopy (SEM) and EDAX tool clarified that the sabkha soils are enriched by quartz, sulfate minerals (gypsum, anhydrite), carbonate minerals (calcite-dolomite-aragonite), chlorides (halite and bischofite), and clay minerals. The results elucidate that the appearance of sabkha deposits and their distribution in the study area are controlled mainly by the content of water soluble salts through parent materials;ground water table;subsurface structural;and physiographic features for instance surface relief or topography;and human activity.展开更多
This paper discusses some preliminary results regarding raw materials used in ancient glass mosaic tesserae. The studied glass tesserae were recovered during the archeological excavation of the mosaics at the Christia...This paper discusses some preliminary results regarding raw materials used in ancient glass mosaic tesserae. The studied glass tesserae were recovered during the archeological excavation of the mosaics at the Christian basilicas in Byllis, Lin and Elbasan, which according to the archeologists were built between the end of Vth and beginning of VIth century AD. In the recent years, several studies are performed on opaque coloured glass but in Albania only few studies are performed in this field. These samples are analyzed using optical microscopy and micro X-ray fluorescence. Optical microscopy is used to analyse the microstructure of the glass tesserae. The main elements and trace elements are determined qualitatively from measurements performed with micro X-ray fluorescence. The glass matrix resulted to be very heterogeneous with too many inclusions dispersed on it. Several elements which are responsible for the color and opacity of glass tesserae are determined. Comparisons are made between the same colors of glass tesserae from different archaeological sites.展开更多
基金supported by the National Research Foundation of Korea (NRF-2022R1C1C1004171)supported by the National Science Foundation (Grant number ACI1548562)。
文摘Layered double hydroxides(LDHs) have attracted considerable attention as a cost effective alternative to the precious iridium-and ruthenium-based electrocatalysts for an oxygen evolution reaction(OER),a bottleneck of water electrolysis for sustainable hydrogen production.Despite their excellent OER performance,the structural and electronic properties of LDHs,particularly during the OER process,remain to be poorly understood.In this study,a series of LDH catalysts is investigated through in situ X-ray absorption fine structure analyses and density functional theory(DFT) calculations.Our experimental results reveal that the LDH catalyst with equal amounts of Ni and Fe(NF-LDH) exhibits the highest OER activity and catalytic life span when compared with its counterparts having equal amounts of Ni and Co(NC-LDH)and Ni only(Ni-LDH).The NF-LDH shows a markedly enhanced OER kinetics compared to the NC-LDH and the Ni-LDH,as proven by the lower overpotentials of 180,240,and 310 mV,respectively,and the Tafel slopes of 35.1,43.4,and 62.7 mV dec^(-1),respectively.The DFT calculations demonstrate that the lowest overpotential of the NF-LDH is associated with the active sites located at the edge planes of NF-LDH in contrast to those located at the basal planes of Ni-LDH and NC-LDH.The current study pinpoints the active sites on various LDHs and presents strategies for optimizing the OER performance of the LDH catalysts.
基金supported by the National Natural Science Foundation of China(Nos.U2141217 and 51935003)。
文摘The real contact area(RCA)of randomly rough contacts has received a great deal of attention because it correlates strongly with friction,lubrication,sealing,and conductivity.Simulations have revealed that the RCA associated with deterministic normal squeezing loads increases when tangential loads are also applied,in a phenomenon called junction growth.However,experimental investigations of the junction growth of randomly rough contacts are rare.Here,we used X-ray computed tomography(CT)to measure junction growth when two aluminum alloy surfaces were in contact.A high-resolution experimental setup was used to apply loads and observe contact behaviors at a resolution of 4μm.The RCA and average contact gaps were computed using a three-dimensional(3D)geometric model constructed from gray CT images using the Otsu thresholding method.The results showed that the RCA increased as the normal load increased.The RCA increased by 22.67%after a tangential load was applied(junction growth),and the average gap decreased by 14.01%after a tangential load was applied.Thus,X-ray CT accurately measured the junction growth as a novel quantitative method.
文摘Eight surface sabkha soils samples were collected from Ismailia—Suez roadbed, southwestern of Suez Canal district. Sedimentological and mineralogical analyses were conducted using grain size;X-ray diffraction and Scanning Electron Microscopy (SEM). Grain size analysis indicates high contents of fine sand and mud as well as presence of salts. X-ray diffraction;Scanning Electron Microscopy (SEM) and EDAX tool clarified that the sabkha soils are enriched by quartz, sulfate minerals (gypsum, anhydrite), carbonate minerals (calcite-dolomite-aragonite), chlorides (halite and bischofite), and clay minerals. The results elucidate that the appearance of sabkha deposits and their distribution in the study area are controlled mainly by the content of water soluble salts through parent materials;ground water table;subsurface structural;and physiographic features for instance surface relief or topography;and human activity.
文摘This paper discusses some preliminary results regarding raw materials used in ancient glass mosaic tesserae. The studied glass tesserae were recovered during the archeological excavation of the mosaics at the Christian basilicas in Byllis, Lin and Elbasan, which according to the archeologists were built between the end of Vth and beginning of VIth century AD. In the recent years, several studies are performed on opaque coloured glass but in Albania only few studies are performed in this field. These samples are analyzed using optical microscopy and micro X-ray fluorescence. Optical microscopy is used to analyse the microstructure of the glass tesserae. The main elements and trace elements are determined qualitatively from measurements performed with micro X-ray fluorescence. The glass matrix resulted to be very heterogeneous with too many inclusions dispersed on it. Several elements which are responsible for the color and opacity of glass tesserae are determined. Comparisons are made between the same colors of glass tesserae from different archaeological sites.
