Thallium is a heavy metal highly toxic to the biosphere. It can be determined by anodic stripping voltammetry after deposition on mercury film. The aim of this work is to study the conditions and mechanisms of deposit...Thallium is a heavy metal highly toxic to the biosphere. It can be determined by anodic stripping voltammetry after deposition on mercury film. The aim of this work is to study the conditions and mechanisms of deposition of Hg on glassy carbon electrode and Tl on Hg film by cyclic voltammetry, scanning electron microscopy, chronoamperometry and impedance techniques. The results showed a germination and growth of a 3D Hg phase on glassy carbon electrode. Similarly, the electrodeposition of Tl on Hg follows a 3D three-dimensional nucleation with diffusion controlled growth. The impedance measurements reveal an easier charge transfer on the Tl film.展开更多
We present a Scanning Electron Microscopy (SEM) technique for the characterisation of biological and non-biological samples at nano-scale level. Scanning Electron Microscopy has been around for a long while especially...We present a Scanning Electron Microscopy (SEM) technique for the characterisation of biological and non-biological samples at nano-scale level. Scanning Electron Microscopy has been around for a long while especially in material science laboratories in developed countries. The SEM has enabled scientist to have a better understanding of microstructure by providing unsurpassed optical magnifications of samples. In this introductory paper, we introduce the techniques of using SEM to capture highly magnified microstructure of a fly found on an African soybean (Glycine max) seed. We are able to estimate the number of lenses in each eye and zoom into features that could describe its life characteristics. Hexagonal lenses are estimated to have sizes ranging from 14 um to 19 um. This paper also presents a finding of a sea coral “pie like structure” on a single grain of sand used for water filtration.展开更多
We introduce voltage-contrast scanning electron microscopy(VC-SEM)for visual characterization of the electronic properties of single-walled carbon nanotubes.VC-SEM involves tuning the electronic band structure and ima...We introduce voltage-contrast scanning electron microscopy(VC-SEM)for visual characterization of the electronic properties of single-walled carbon nanotubes.VC-SEM involves tuning the electronic band structure and imaging the potential profi le along the length of the nanotube.The resultant secondary electron contrast allows to distinguish between metallic and semiconducting carbon nanotubes and to follow the switching of semiconducting nanotube devices,as confi rmed by in situ electrical transport measurements.We demonstrate that high-density arrays of individual nanotube devices can be rapidly and simultaneously characterized.A leakage current model in combination with fi nite element simulations of the device electrostatics is presented in order to explain the observed contrast evolution of the nanotube and surface electrodes.This work serves to fi ll a void in electronic characterization of molecular device architectures.展开更多
The combination of focused ion beam (FIB) with scanning electron microscopy (SEM), also known as FIB-SEM tomography, has become a powerful 3D imaging technique at the nanometer scale. This method uses an ion beam to m...The combination of focused ion beam (FIB) with scanning electron microscopy (SEM), also known as FIB-SEM tomography, has become a powerful 3D imaging technique at the nanometer scale. This method uses an ion beam to mill away a thin slice of material, which is then block-face imaged using an electron beam. With consecutive slicing along the z-axis and subsequent imaging, a volume of interest can be reconstructed from the images and further analyzed. Hierarchical nanoporous gold (HNPG) exhibits unique structural properties and has a ligament size of 15–110 nm and pore size of 5–20 nm. Accurate reconstruction of its image is crucial in determining its mechanical and other properties. Slice thickness is one of the most critical and uncertain parameters in FIB-SEM tomography. For HNPG, the slice thickness should be at least half as thin as the pore size and, in our approach, should not exceed 10 nm. Variations in slice thickness are caused by various microscope and sample parameters, e.g., converged ion milling beam shape, charging effects, beam drift, or sample surface roughness. Determining and optimizing the actual slice thickness variation appear challenging. In this work, we examine the influence of ion beam scan resolution and the dwell time on the mean and standard deviation of slice thickness. After optimizing the resolution and dwell time to achieve the target slice thickness and lowest possible standard deviation, we apply these parameters to analyze an actual HNPG sample. Our approach can determine the thickness of each slice along the z-axis and estimate the deviation of the milling process along the y-axis (slow imaging axis). For this function, we create a multi-ruler structure integrated with the HNPG sample.展开更多
Scanning transmission electron microscopy(STEM) has been shown as powerful tools for material characterization,especially after the appearance of aberration-corrector which greatly enhances the resolution of STEM. Hig...Scanning transmission electron microscopy(STEM) has been shown as powerful tools for material characterization,especially after the appearance of aberration-corrector which greatly enhances the resolution of STEM. High angle annular dark field(HAADF) and annular bright field(ABF) imaging of the aberration-corrected STEM are widely used due to their high-resolution capabilities and easily interpretable image contrasts. However, HAADF mode of the STEM is still limited in detecting light elements due to the weak electron-scattering power. ABF mode of the STEM could detect light and heavy elements simultaneously, providing unprecedented opportunities for probing unknown structures of materials. Atomiclevel structure investigation of materials has been achieved by means of these imaging modes, which is invaluable in many fields for either improving properties of materials or developing new materials. This paper aims to provide a introduction of HAADF and ABF imaging techniques and reviews their applications in characterization of cathode materials, study of electrochemical reaction mechanisms, and exploring the effective design of lithium-ion batteries(LIBs). The future prospects of the STEM are also discussed.展开更多
To gain further understanding of the luminescence properties of multiquantum wells and the factors affecting them on a microscopic level,cathodoluminescence combined with scanning transmission electron microscopy and ...To gain further understanding of the luminescence properties of multiquantum wells and the factors affecting them on a microscopic level,cathodoluminescence combined with scanning transmission electron microscopy and spectroscopy was used to measure the luminescence of In_(0.15)Ga_(0.85)N five-period multiquantum wells.The lattice-composition-energy relationship was established with the help of energy-dispersive x-ray spectroscopy,and the bandgaps of In_(0.15)Ga_(0.85)N and GaN in multiple quantum wells were extracted by electron energy loss spectroscopy to understand the features of cathodoluminescence spectra.The luminescence differences between different periods of multiquantum wells and the effects of defects such as composition fluctuation and dislocations on the luminescence of multiple quantum wells were revealed.Our study establishing the direct relationship between the atomic structure of In_(x)Ga_(1-x)N multiquantum wells and photoelectric properties provides useful information for nitride applications.展开更多
Halide perovskites are strategically important in the field of energy materials. Along with the rapid development of the materials and related devices, there is an urgent need to understand the structure–property rel...Halide perovskites are strategically important in the field of energy materials. Along with the rapid development of the materials and related devices, there is an urgent need to understand the structure–property relationship from nanoscale to atomic scale. Much effort has been made in the past few years to overcome the difficulty of imaging limited by electron dose,and to further extend the investigation towards operando conditions. This review is dedicated to recent studies of advanced transmission electron microscopy(TEM) characterizations for halide perovskites. The irradiation damage caused by the interaction of electron beams and perovskites under conventional imaging conditions are first summarized and discussed. Low-dose TEM is then discussed, including electron diffraction and emerging techniques for high-resolution TEM(HRTEM) imaging. Atomic-resolution imaging, defects identification and chemical mapping on halide perovskites are reviewed. Cryo-TEM for halide perovskites is discussed, since it can readily suppress irradiation damage and has been rapidly developed in the past few years. Finally, the applications of in-situ TEM in the degradation study of perovskites under environmental conditions such as heating,biasing, light illumination and humidity are reviewed. More applications of emerging TEM characterizations are foreseen in the coming future, unveiling the structural origin of halide perovskite’s unique properties and degradation mechanism under operando conditions, so to assist the design of a more efficient and robust energy material.展开更多
The line width(often synonymously used for critical dimension,CD)is a crucial parameter in integrated circuits.To accurately control CD values in manufacturing,a reasonable CD reference material is required to calibra...The line width(often synonymously used for critical dimension,CD)is a crucial parameter in integrated circuits.To accurately control CD values in manufacturing,a reasonable CD reference material is required to calibrate the corresponding instruments.We develop a new reference material with nominal CDs of 160 nm,80 nm,and 40 nm.The line features are investigated based on the metrological scanning electron microscope which is developed by the National Institute of Metrology(NIM)in China.Also,we propose a new characterization method for the precise measurement of CD values.After filtering and leveling the intensity profiles,the line features are characterized by the combination model of the Gaussian and Lorentz functions.The left and right edges of CD are automatically extracted with the profile decomposition and k-means algorithm.Then the width of the two edges at the half intensity position is regarded as the standard CD value.Finally,the measurement results are evaluated in terms of the sample,instrument,algorithm,and repeatability.The experiments indicate efficiency of the proposed method which can be easily applied in practice to accurately characterize CDs.展开更多
Electron microscopy has long been used in research in the fields of life sciences and materials sciences.Transmission and scanning electron microscopy and energy-dispersive X-ray spectroscopy(EDX)analyses have also be...Electron microscopy has long been used in research in the fields of life sciences and materials sciences.Transmission and scanning electron microscopy and energy-dispersive X-ray spectroscopy(EDX)analyses have also been performed in the field of gastroenterology.Electron microscopy and EDX enable(1)Observation of ultrastructural differences in esophageal epithelial cells in patients with gastroesophageal reflux and eosinophilic esophagitis;(2)Detection of lanthanum deposition in the stomach and duodenum;(3)Ultrastructural and elemental analyses of enteroliths and bezoars;(4)Detection and characterization of microorganisms in the gastrointestinal tract;(5)Diagnosis of gastrointestinal tumors with neuroendocrine differentiation;and(6)Analysis of gold nanoparticles potentially used in endoscopic photodynamic therapy.This review aims to foster a better understanding of electron microscopy applications by reviewing relevant clinical studies,basic research findings,and the state of current research carried out in gastroenterology science.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
We investigated the parametric optimization on incremental sheet forming of stainless steel using Grey Relational Analysis(GRA) coupled with Principal Component Analysis(PCA). AISI 316L stainless steel sheets were use...We investigated the parametric optimization on incremental sheet forming of stainless steel using Grey Relational Analysis(GRA) coupled with Principal Component Analysis(PCA). AISI 316L stainless steel sheets were used to develop double wall angle pyramid with aid of tungsten carbide tool. GRA coupled with PCA was used to plan the experiment conditions. Control factors such as Tool Diameter(TD), Step Depth(SD), Bottom Wall Angle(BWA), Feed Rate(FR) and Spindle Speed(SS) on Top Wall Angle(TWA) and Top Wall Angle Surface Roughness(TWASR) have been studied. Wall angle increases with increasing tool diameter due to large contact area between tool and workpiece. As the step depth, feed rate and spindle speed increase,TWASR decreases with increasing tool diameter. As the step depth increasing, the hydrostatic stress is raised causing severe cracks in the deformed surface. Hence it was concluded that the proposed hybrid method was suitable for optimizing the factors and response.展开更多
The mechanical properties of cementitious sand and gravel damming material have been experimentally determined by means of microscopic SEM(Scanning Electron Microscopy)image analysis.The results show that the combinat...The mechanical properties of cementitious sand and gravel damming material have been experimentally determined by means of microscopic SEM(Scanning Electron Microscopy)image analysis.The results show that the combination of fly ash and water can fill the voids in cemented sand and gravel test blocks because of the presence of hydrated calcium silicate and other substances;thereby,the compactness and mechanical properties of these materials can be greatly improved.For every 10 kg/m^(3) increase in the amount of cementitious material,the density increases by about 2%,and the water content decreases by 0.2%.The amount of cementitious material used in the sand and gravel in these tests was 80-110 kg/m^(3),the water-binder ratio was 1-1.50.Moreover,the splitting tensile strength was 1/10 of the compressive strength,and the maximum strength was 7.42 MPa at 90 d.The optimal mix ratio has been found to be 50 kg of cement,60 kg of fly ash and 120 kg of water(C50F60W120).The related dry density was 2.6 g/cm^(3),the water content was 6%,and the water-binder ratio was 1.09.展开更多
The influence of sodium silicate on the corrosion behaviour of aluminium alloy 7075-T6 in 0.1 M sodium chloride solution was studied by open circuit potential (OCP) and electrochemical impedance spectroscopy (EIS) tec...The influence of sodium silicate on the corrosion behaviour of aluminium alloy 7075-T6 in 0.1 M sodium chloride solution was studied by open circuit potential (OCP) and electrochemical impedance spectroscopy (EIS) techniques. Scanning electron microscopy (SEM) was used to characterize the AA7075-T6 surface. Silicate can significantly reduce corrosion deterioration and the inhibition efficiency increases with the concentration of Na<sub>2</sub>SiO<sub>3</sub>. The corrosion inhibition mechanism involves the formation of a protective film over the alloy surface by adsorption of aluminosilicate anions from solution, as has also been suggested by others in literature.展开更多
The Turin Shroud, recently accessible for hands-on scientific research, is now extensively investigated. Its pinkish red blood stains that seem anomalous ones are studied by modern techniques (notably by resolute opti...The Turin Shroud, recently accessible for hands-on scientific research, is now extensively investigated. Its pinkish red blood stains that seem anomalous ones are studied by modern techniques (notably by resolute optical microscopy and scanning electron microscopy coupled with energy dispersive X-ray). Exploration by these techniques of a blood stain located on the face permits us to discover some red-colour particles (hematite, biotite and cinnabar) of exogenous material in this stain. We finally characterize these red-colour particles and try to explain their presences in the blood stain. Globally, all these red-colour particles cannot explain all of the reddish appearance of the area under study.展开更多
Organic matter(OM)hosted pores are crucial for the storage and migration of petroleum in shale reservoirs.Thermal maturity and macerals type are important factors controlling the development of pores therein.In this s...Organic matter(OM)hosted pores are crucial for the storage and migration of petroleum in shale reservoirs.Thermal maturity and macerals type are important factors controlling the development of pores therein.In this study,six lacustrine shale samples with different thermal maturities from the first member of the Qingshankou Formation in the Songliao Basin,of which vitrinite reflectance(R_(o))ranging from 0.58% to 1.43%,were selected for a comparative analysis.Scanning electron microscopy(SEM)and reflected light microscopy were combined to investigate the development of organic pores in different macerals during thermal maturation.The results show that alginite and liptodetrinite are the dominant primary macerals,followed by bituminite.Only a few primary organic pores developed in the alginite at the lowest maturity(R_(o)=0.58%).As a result of petroleum generation,oil-prone macerals began to transform to initial-oil solid bitumen at the early oil window(R_(o)=0.73%)and shrinkage cracks were observed.Initial-oil solid bitumen cracked to oil,gas and post-oil bitumen by primary cracking(R_(o)=0.98%).Moreover,solid bitumen(SB)was found to be the dominant OM when R_(o)>0.98%,which indicates that SB is the product of oil-prone macerals transformation.Many secondary bubble pores were observed on SB,which formed by gas release,while devolatilization cracks developed on migrated SB.Additionally,at the late oil window(Ro?1.16%),migrated SB filled the interparticle pore spaces.With further increase in temperature,the liquid oil underwent secondary cracking into pyrobitumen and gas,and spongy pores developed on the pyrobitumen at higher levels of maturity(Ro=1.43%),which formed when pyrobitumen cracked into gas.Vitrinite and inertinite are stable without any visible pores over the range of maturities,verifying their low petroleum generation potential.In addition,it was concluded that clay minerals could have a catalytic effect on the petroleum generation,which may explain why organicclay mixtures had more abundant pores than single OM particles.However,after R_(o)>0.98%,authigenic minerals occupied the organic pore spaces on the organic-clay mixtures,resulting in fewer pores compared to those observed in samples at the early to peak oil window.展开更多
The engineering characteristics of the soil,soil-fly ash and fly ash-lime,were examined to utilize as base layer material in civil construction.The influence of fly ash percentage and the effect of curing on Californi...The engineering characteristics of the soil,soil-fly ash and fly ash-lime,were examined to utilize as base layer material in civil construction.The influence of fly ash percentage and the effect of curing on California bearing ratio(CBR)and unconfined compressive strength(UCS),of soil and soil-fly ash mixing and layered system were examined to estimate the optimum quantity.The volumetric swelling of the optimal mixture was estimated to be within the allowable limits.Scanning microscope analysis and X-ray diffraction tests were performed.A model test analyses with three layers were conducted by finite element method and stress-strain behavior was observed.展开更多
Tensile and shear fractures are significant mechanisms for rock failure.Understanding the fractures that occur in rock can reveal rock failure mechanisms.Scanning electron microscopy(SEM)has been widely used to analyz...Tensile and shear fractures are significant mechanisms for rock failure.Understanding the fractures that occur in rock can reveal rock failure mechanisms.Scanning electron microscopy(SEM)has been widely used to analyze tensile and shear fractures of rock on a mesoscopic scale.To quantify tensile and shear fractures,this study proposed an innovative method composed of SEM images and deep learning techniques to identify tensile and shear fractures in red sandstone.First,direct tensile and preset angle shear tests were performed for red sandstone to produce representative tensile and shear fracture surfaces,which were then observed by SEM.Second,these obtained SEM images were applied to develop deep learning models(AlexNet,VGG13,and SqueezeNet).Model evaluation showed that VGG13 was the best model,with a testing accuracy of 0.985.Third,the features of tensile and shear fractures of red sandstone learned by VGG13 were analyzed by the integrated gradient algorithm.VGG13 was then implemented to identify the distribution and proportion of tensile and shear fractures on the failure surfaces of rock fragments caused by uniaxial compression and Brazilian splitting tests.Results demonstrated the model feasibility and suggested that the proposed method can reveal rock failure mechanisms.展开更多
Background Plant pollen has diverse morphological characteristics that can be consistently passed down from generation to generation.Information on pollen morphology is thus immensely important for plant classificatio...Background Plant pollen has diverse morphological characteristics that can be consistently passed down from generation to generation.Information on pollen morphology is thus immensely important for plant classification and identification.In the genus Gossypium,however,in-depth research on pollen morphology is lacking,with only few reports on limited cotton species.To evaluate the diversity of pollen in Gossypium,we therefore conducted a comprehensive analysis of the pollen morphology of 33 cotton species and varieties using scanning electron microscopy.Results The 33 analyzed cotton samples exhibited common pollen morphological features,including spherical shapes,radial symmetry,echination,panporation,and operculation,while the pollen size,spine shape,spine density and length showed distinctive features.Pollen size varied significantly among species,with diameters ranging from62.43 μm in G.harknessii to 103.41 μm in G.barbadense.The exine had an echinate sculptural texture,and spines were mostly conical or sharply conical but occasionally rod-like.Spine density varied from 173 in G.incanum to 54 in G.gossypioides,while spine length ranged from 3.53 μm in G.herbaceum to 9.47 μm in G.barbadense.In addition,the 33cotton species and varieties were grouped at a genetic distance of 3.83 into three clusters.Cluster Ⅰ comprised five allotetraploid AD-genome cotton species,four D-genome species,and one K-genome species.Cluster Ⅱ included 13diploid species from A,B,D,E,and G genomes,whereas Cluster Ⅲ only consisted one E-genome species G.incanum.Conclusions Although pollen characteristics alone are not enough to resolve taxonomic and systematic relationships within the genus Gossypium,our results add to knowledge on palynomorphology and contribute to phenological information on these taxa.Our findings should aid future systematic and phylogenetic studies of the Gossypium genus.展开更多
The aim was to develop films with a new mixture of collagen fiber plus polyvinyl alcohol added of oregano or rosemary essential oils at different levels (0%, 2%, 4% and 6%), as well as to assess the antimicrobial acti...The aim was to develop films with a new mixture of collagen fiber plus polyvinyl alcohol added of oregano or rosemary essential oils at different levels (0%, 2%, 4% and 6%), as well as to assess the antimicrobial activity, physical, optical, microstructure and molecular properties in the films. An interaction between the ingredients was observed at the molecular level by FTIR. The amide II and amide III bands, which are important to verify collagen conformation, showed intense peaks in the films. The formation of a network through collagen fibers was produced, acting as a reinforcement in matrix. The films with essential oil had an expressive antimicrobial activity by the steam contact method (micro-atmosphere), mainly for Escherichia coli and Staphylococcus aureus. The mixture of collagen fiber plus polyvinyl alcohol added of essential oils is a promising matrix for application in food as active packaging.展开更多
The objective of the study was to characterize the clays of the Lama depression in Benin. Macroscopic examination of hand soundings, dynamic penetration test and stratigraphic correlation of water borehole logs, as we...The objective of the study was to characterize the clays of the Lama depression in Benin. Macroscopic examination of hand soundings, dynamic penetration test and stratigraphic correlation of water borehole logs, as well as scanning electron microscopy (SEM) combined with energy-dispersive X-ray microanalysis (EDX) method were made on compact or stratified clays. The large grains are embedded in a sintered matrix. The texture is heterogeneous and open, including quartz, carbonates and organic matter. The fine fraction is dominated by mineral paragenesis characterizing Kaolinite-Quartz-Calcite-Gypsum dioctahedral smectites composed of: Oxygen, Silica, Carbon, Aluminum, Iron, Zinc, Titanium and Magnesium. This smectic and regular structure includes coarse grains of the order of 800 μm. The pore diameters vary from 130 μm to 1.14 μm. The inter-particle porosity is poorly developed unlike the inter-aggregate pores larger than 0.05 μm. The texture is laminar and shows elongated turbo static particles with more or less rounded edges and honeycomb particles. Quartz and carbonates induce an increase in heterogeneities which develop mechanical sensitivity and hydraulic conductivity. High contents of silica, iron or aluminum and low contents of calcium and magnesium, as well as the presence of other trace elements suggest an alumino-ferriferous clay resulting from the hydrothermal alteration of the acid granite massif. These heterogeneities promote less tortuous pores or paths, making these clays more permeable. Finally, other stabilization studies and improvements to hydraulic products and binders should favor the use of the studied clay as improved backfill or drilling muds.展开更多
文摘Thallium is a heavy metal highly toxic to the biosphere. It can be determined by anodic stripping voltammetry after deposition on mercury film. The aim of this work is to study the conditions and mechanisms of deposition of Hg on glassy carbon electrode and Tl on Hg film by cyclic voltammetry, scanning electron microscopy, chronoamperometry and impedance techniques. The results showed a germination and growth of a 3D Hg phase on glassy carbon electrode. Similarly, the electrodeposition of Tl on Hg follows a 3D three-dimensional nucleation with diffusion controlled growth. The impedance measurements reveal an easier charge transfer on the Tl film.
文摘We present a Scanning Electron Microscopy (SEM) technique for the characterisation of biological and non-biological samples at nano-scale level. Scanning Electron Microscopy has been around for a long while especially in material science laboratories in developed countries. The SEM has enabled scientist to have a better understanding of microstructure by providing unsurpassed optical magnifications of samples. In this introductory paper, we introduce the techniques of using SEM to capture highly magnified microstructure of a fly found on an African soybean (Glycine max) seed. We are able to estimate the number of lenses in each eye and zoom into features that could describe its life characteristics. Hexagonal lenses are estimated to have sizes ranging from 14 um to 19 um. This paper also presents a finding of a sea coral “pie like structure” on a single grain of sand used for water filtration.
基金The research was funded by the Initiative and Networking Fund of the Helmholtz Gemeinschaft Deutscher Forschungszentren and equipment grant from Agilent Technologies.
文摘We introduce voltage-contrast scanning electron microscopy(VC-SEM)for visual characterization of the electronic properties of single-walled carbon nanotubes.VC-SEM involves tuning the electronic band structure and imaging the potential profi le along the length of the nanotube.The resultant secondary electron contrast allows to distinguish between metallic and semiconducting carbon nanotubes and to follow the switching of semiconducting nanotube devices,as confi rmed by in situ electrical transport measurements.We demonstrate that high-density arrays of individual nanotube devices can be rapidly and simultaneously characterized.A leakage current model in combination with fi nite element simulations of the device electrostatics is presented in order to explain the observed contrast evolution of the nanotube and surface electrodes.This work serves to fi ll a void in electronic characterization of molecular device architectures.
基金funded by the Deutsche Forschungsgemeinschaft(DFG,German Research Foundation)—Project SFB 986—Tailor-Made Multiscale Materials Systems,subproject B9—Microstructure-based classification and mechanical analysis of nanoporous metals by machine learningOpen Access funding enabled and organized by Projekt DEAL.
文摘The combination of focused ion beam (FIB) with scanning electron microscopy (SEM), also known as FIB-SEM tomography, has become a powerful 3D imaging technique at the nanometer scale. This method uses an ion beam to mill away a thin slice of material, which is then block-face imaged using an electron beam. With consecutive slicing along the z-axis and subsequent imaging, a volume of interest can be reconstructed from the images and further analyzed. Hierarchical nanoporous gold (HNPG) exhibits unique structural properties and has a ligament size of 15–110 nm and pore size of 5–20 nm. Accurate reconstruction of its image is crucial in determining its mechanical and other properties. Slice thickness is one of the most critical and uncertain parameters in FIB-SEM tomography. For HNPG, the slice thickness should be at least half as thin as the pore size and, in our approach, should not exceed 10 nm. Variations in slice thickness are caused by various microscope and sample parameters, e.g., converged ion milling beam shape, charging effects, beam drift, or sample surface roughness. Determining and optimizing the actual slice thickness variation appear challenging. In this work, we examine the influence of ion beam scan resolution and the dwell time on the mean and standard deviation of slice thickness. After optimizing the resolution and dwell time to achieve the target slice thickness and lowest possible standard deviation, we apply these parameters to analyze an actual HNPG sample. Our approach can determine the thickness of each slice along the z-axis and estimate the deviation of the milling process along the y-axis (slow imaging axis). For this function, we create a multi-ruler structure integrated with the HNPG sample.
基金supported by the National Basic Research Program of China(Grant No.2014CB921002)the Strategic Priority Research Program of Chinese Academy of Sciences(Grant No.XDB07030200)the National Natural Science Foundation of China(Grant Nos.51522212,51421002,and 51672307)
文摘Scanning transmission electron microscopy(STEM) has been shown as powerful tools for material characterization,especially after the appearance of aberration-corrector which greatly enhances the resolution of STEM. High angle annular dark field(HAADF) and annular bright field(ABF) imaging of the aberration-corrected STEM are widely used due to their high-resolution capabilities and easily interpretable image contrasts. However, HAADF mode of the STEM is still limited in detecting light elements due to the weak electron-scattering power. ABF mode of the STEM could detect light and heavy elements simultaneously, providing unprecedented opportunities for probing unknown structures of materials. Atomiclevel structure investigation of materials has been achieved by means of these imaging modes, which is invaluable in many fields for either improving properties of materials or developing new materials. This paper aims to provide a introduction of HAADF and ABF imaging techniques and reviews their applications in characterization of cathode materials, study of electrochemical reaction mechanisms, and exploring the effective design of lithium-ion batteries(LIBs). The future prospects of the STEM are also discussed.
基金Project supported by the National Key R&D Program of China (Grant No. 2019YFA0708202)the National Natural Science Foundation of China (Grant Nos. 11974023, 52021006, 61974139, 12074369, and 12104017)+1 种基金the “2011 Program” from the Peking–Tsinghua–IOP Collaborative Innovation Center of Quantum Matterthe Youth Supporting Program of Institute of Semiconductors
文摘To gain further understanding of the luminescence properties of multiquantum wells and the factors affecting them on a microscopic level,cathodoluminescence combined with scanning transmission electron microscopy and spectroscopy was used to measure the luminescence of In_(0.15)Ga_(0.85)N five-period multiquantum wells.The lattice-composition-energy relationship was established with the help of energy-dispersive x-ray spectroscopy,and the bandgaps of In_(0.15)Ga_(0.85)N and GaN in multiple quantum wells were extracted by electron energy loss spectroscopy to understand the features of cathodoluminescence spectra.The luminescence differences between different periods of multiquantum wells and the effects of defects such as composition fluctuation and dislocations on the luminescence of multiple quantum wells were revealed.Our study establishing the direct relationship between the atomic structure of In_(x)Ga_(1-x)N multiquantum wells and photoelectric properties provides useful information for nitride applications.
基金the Beijing Municipal High Level Innovative Team Building Program (IDHT20190503)the National Natural Science Fund for Innovative Research Groups of China (51621003)the National Natural Science Foundation of China (12074017)。
文摘Halide perovskites are strategically important in the field of energy materials. Along with the rapid development of the materials and related devices, there is an urgent need to understand the structure–property relationship from nanoscale to atomic scale. Much effort has been made in the past few years to overcome the difficulty of imaging limited by electron dose,and to further extend the investigation towards operando conditions. This review is dedicated to recent studies of advanced transmission electron microscopy(TEM) characterizations for halide perovskites. The irradiation damage caused by the interaction of electron beams and perovskites under conventional imaging conditions are first summarized and discussed. Low-dose TEM is then discussed, including electron diffraction and emerging techniques for high-resolution TEM(HRTEM) imaging. Atomic-resolution imaging, defects identification and chemical mapping on halide perovskites are reviewed. Cryo-TEM for halide perovskites is discussed, since it can readily suppress irradiation damage and has been rapidly developed in the past few years. Finally, the applications of in-situ TEM in the degradation study of perovskites under environmental conditions such as heating,biasing, light illumination and humidity are reviewed. More applications of emerging TEM characterizations are foreseen in the coming future, unveiling the structural origin of halide perovskite’s unique properties and degradation mechanism under operando conditions, so to assist the design of a more efficient and robust energy material.
基金supported by the National Key Research and Development Program of China(Grant No.2020YFF0218403)the Basic Scientific Research Operating Fund of NIM(Grant No.AKYZD2007-1)。
文摘The line width(often synonymously used for critical dimension,CD)is a crucial parameter in integrated circuits.To accurately control CD values in manufacturing,a reasonable CD reference material is required to calibrate the corresponding instruments.We develop a new reference material with nominal CDs of 160 nm,80 nm,and 40 nm.The line features are investigated based on the metrological scanning electron microscope which is developed by the National Institute of Metrology(NIM)in China.Also,we propose a new characterization method for the precise measurement of CD values.After filtering and leveling the intensity profiles,the line features are characterized by the combination model of the Gaussian and Lorentz functions.The left and right edges of CD are automatically extracted with the profile decomposition and k-means algorithm.Then the width of the two edges at the half intensity position is regarded as the standard CD value.Finally,the measurement results are evaluated in terms of the sample,instrument,algorithm,and repeatability.The experiments indicate efficiency of the proposed method which can be easily applied in practice to accurately characterize CDs.
文摘Electron microscopy has long been used in research in the fields of life sciences and materials sciences.Transmission and scanning electron microscopy and energy-dispersive X-ray spectroscopy(EDX)analyses have also been performed in the field of gastroenterology.Electron microscopy and EDX enable(1)Observation of ultrastructural differences in esophageal epithelial cells in patients with gastroesophageal reflux and eosinophilic esophagitis;(2)Detection of lanthanum deposition in the stomach and duodenum;(3)Ultrastructural and elemental analyses of enteroliths and bezoars;(4)Detection and characterization of microorganisms in the gastrointestinal tract;(5)Diagnosis of gastrointestinal tumors with neuroendocrine differentiation;and(6)Analysis of gold nanoparticles potentially used in endoscopic photodynamic therapy.This review aims to foster a better understanding of electron microscopy applications by reviewing relevant clinical studies,basic research findings,and the state of current research carried out in gastroenterology science.
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.
文摘We investigated the parametric optimization on incremental sheet forming of stainless steel using Grey Relational Analysis(GRA) coupled with Principal Component Analysis(PCA). AISI 316L stainless steel sheets were used to develop double wall angle pyramid with aid of tungsten carbide tool. GRA coupled with PCA was used to plan the experiment conditions. Control factors such as Tool Diameter(TD), Step Depth(SD), Bottom Wall Angle(BWA), Feed Rate(FR) and Spindle Speed(SS) on Top Wall Angle(TWA) and Top Wall Angle Surface Roughness(TWASR) have been studied. Wall angle increases with increasing tool diameter due to large contact area between tool and workpiece. As the step depth, feed rate and spindle speed increase,TWASR decreases with increasing tool diameter. As the step depth increasing, the hydrostatic stress is raised causing severe cracks in the deformed surface. Hence it was concluded that the proposed hybrid method was suitable for optimizing the factors and response.
基金supported by the Scientific Research Fund of Yunnan Provincial Department of Education(2022Y286)15th Student Science and Technology Innovation and Entrepreneurship Action Fund Project of Yunnan Agricultural University(2022ZKX098)+1 种基金the Yunnan University Professional Degree Graduate Student Practical Innovation Fund Project(Grant Number ZC-22222374)the Scientific Research Fund Project of Yunnan Education Department(Grant Numbers 2023J1974 and 2023J1976).
文摘The mechanical properties of cementitious sand and gravel damming material have been experimentally determined by means of microscopic SEM(Scanning Electron Microscopy)image analysis.The results show that the combination of fly ash and water can fill the voids in cemented sand and gravel test blocks because of the presence of hydrated calcium silicate and other substances;thereby,the compactness and mechanical properties of these materials can be greatly improved.For every 10 kg/m^(3) increase in the amount of cementitious material,the density increases by about 2%,and the water content decreases by 0.2%.The amount of cementitious material used in the sand and gravel in these tests was 80-110 kg/m^(3),the water-binder ratio was 1-1.50.Moreover,the splitting tensile strength was 1/10 of the compressive strength,and the maximum strength was 7.42 MPa at 90 d.The optimal mix ratio has been found to be 50 kg of cement,60 kg of fly ash and 120 kg of water(C50F60W120).The related dry density was 2.6 g/cm^(3),the water content was 6%,and the water-binder ratio was 1.09.
文摘The influence of sodium silicate on the corrosion behaviour of aluminium alloy 7075-T6 in 0.1 M sodium chloride solution was studied by open circuit potential (OCP) and electrochemical impedance spectroscopy (EIS) techniques. Scanning electron microscopy (SEM) was used to characterize the AA7075-T6 surface. Silicate can significantly reduce corrosion deterioration and the inhibition efficiency increases with the concentration of Na<sub>2</sub>SiO<sub>3</sub>. The corrosion inhibition mechanism involves the formation of a protective film over the alloy surface by adsorption of aluminosilicate anions from solution, as has also been suggested by others in literature.
文摘The Turin Shroud, recently accessible for hands-on scientific research, is now extensively investigated. Its pinkish red blood stains that seem anomalous ones are studied by modern techniques (notably by resolute optical microscopy and scanning electron microscopy coupled with energy dispersive X-ray). Exploration by these techniques of a blood stain located on the face permits us to discover some red-colour particles (hematite, biotite and cinnabar) of exogenous material in this stain. We finally characterize these red-colour particles and try to explain their presences in the blood stain. Globally, all these red-colour particles cannot explain all of the reddish appearance of the area under study.
基金financially supported by the National Natural Science Foundation of China(41972156)the Natural Science Foundation of Heilongjiang Province(TD 2021D001).
文摘Organic matter(OM)hosted pores are crucial for the storage and migration of petroleum in shale reservoirs.Thermal maturity and macerals type are important factors controlling the development of pores therein.In this study,six lacustrine shale samples with different thermal maturities from the first member of the Qingshankou Formation in the Songliao Basin,of which vitrinite reflectance(R_(o))ranging from 0.58% to 1.43%,were selected for a comparative analysis.Scanning electron microscopy(SEM)and reflected light microscopy were combined to investigate the development of organic pores in different macerals during thermal maturation.The results show that alginite and liptodetrinite are the dominant primary macerals,followed by bituminite.Only a few primary organic pores developed in the alginite at the lowest maturity(R_(o)=0.58%).As a result of petroleum generation,oil-prone macerals began to transform to initial-oil solid bitumen at the early oil window(R_(o)=0.73%)and shrinkage cracks were observed.Initial-oil solid bitumen cracked to oil,gas and post-oil bitumen by primary cracking(R_(o)=0.98%).Moreover,solid bitumen(SB)was found to be the dominant OM when R_(o)>0.98%,which indicates that SB is the product of oil-prone macerals transformation.Many secondary bubble pores were observed on SB,which formed by gas release,while devolatilization cracks developed on migrated SB.Additionally,at the late oil window(Ro?1.16%),migrated SB filled the interparticle pore spaces.With further increase in temperature,the liquid oil underwent secondary cracking into pyrobitumen and gas,and spongy pores developed on the pyrobitumen at higher levels of maturity(Ro=1.43%),which formed when pyrobitumen cracked into gas.Vitrinite and inertinite are stable without any visible pores over the range of maturities,verifying their low petroleum generation potential.In addition,it was concluded that clay minerals could have a catalytic effect on the petroleum generation,which may explain why organicclay mixtures had more abundant pores than single OM particles.However,after R_(o)>0.98%,authigenic minerals occupied the organic pore spaces on the organic-clay mixtures,resulting in fewer pores compared to those observed in samples at the early to peak oil window.
文摘The engineering characteristics of the soil,soil-fly ash and fly ash-lime,were examined to utilize as base layer material in civil construction.The influence of fly ash percentage and the effect of curing on California bearing ratio(CBR)and unconfined compressive strength(UCS),of soil and soil-fly ash mixing and layered system were examined to estimate the optimum quantity.The volumetric swelling of the optimal mixture was estimated to be within the allowable limits.Scanning microscope analysis and X-ray diffraction tests were performed.A model test analyses with three layers were conducted by finite element method and stress-strain behavior was observed.
基金financially supported by the National Natural Science Foundation of China(No.52074349)the Fundamental Research Funds for the Central Universities of Central South University(No.2023zzts0726)。
文摘Tensile and shear fractures are significant mechanisms for rock failure.Understanding the fractures that occur in rock can reveal rock failure mechanisms.Scanning electron microscopy(SEM)has been widely used to analyze tensile and shear fractures of rock on a mesoscopic scale.To quantify tensile and shear fractures,this study proposed an innovative method composed of SEM images and deep learning techniques to identify tensile and shear fractures in red sandstone.First,direct tensile and preset angle shear tests were performed for red sandstone to produce representative tensile and shear fracture surfaces,which were then observed by SEM.Second,these obtained SEM images were applied to develop deep learning models(AlexNet,VGG13,and SqueezeNet).Model evaluation showed that VGG13 was the best model,with a testing accuracy of 0.985.Third,the features of tensile and shear fractures of red sandstone learned by VGG13 were analyzed by the integrated gradient algorithm.VGG13 was then implemented to identify the distribution and proportion of tensile and shear fractures on the failure surfaces of rock fragments caused by uniaxial compression and Brazilian splitting tests.Results demonstrated the model feasibility and suggested that the proposed method can reveal rock failure mechanisms.
基金This research was supported by the grants from the National Natural Science Foundation of China(32072023)the Project of Sanya Yazhou Bay Science and Technology City(SCKJ-JYRC-2022-88).
文摘Background Plant pollen has diverse morphological characteristics that can be consistently passed down from generation to generation.Information on pollen morphology is thus immensely important for plant classification and identification.In the genus Gossypium,however,in-depth research on pollen morphology is lacking,with only few reports on limited cotton species.To evaluate the diversity of pollen in Gossypium,we therefore conducted a comprehensive analysis of the pollen morphology of 33 cotton species and varieties using scanning electron microscopy.Results The 33 analyzed cotton samples exhibited common pollen morphological features,including spherical shapes,radial symmetry,echination,panporation,and operculation,while the pollen size,spine shape,spine density and length showed distinctive features.Pollen size varied significantly among species,with diameters ranging from62.43 μm in G.harknessii to 103.41 μm in G.barbadense.The exine had an echinate sculptural texture,and spines were mostly conical or sharply conical but occasionally rod-like.Spine density varied from 173 in G.incanum to 54 in G.gossypioides,while spine length ranged from 3.53 μm in G.herbaceum to 9.47 μm in G.barbadense.In addition,the 33cotton species and varieties were grouped at a genetic distance of 3.83 into three clusters.Cluster Ⅰ comprised five allotetraploid AD-genome cotton species,four D-genome species,and one K-genome species.Cluster Ⅱ included 13diploid species from A,B,D,E,and G genomes,whereas Cluster Ⅲ only consisted one E-genome species G.incanum.Conclusions Although pollen characteristics alone are not enough to resolve taxonomic and systematic relationships within the genus Gossypium,our results add to knowledge on palynomorphology and contribute to phenological information on these taxa.Our findings should aid future systematic and phylogenetic studies of the Gossypium genus.
文摘The aim was to develop films with a new mixture of collagen fiber plus polyvinyl alcohol added of oregano or rosemary essential oils at different levels (0%, 2%, 4% and 6%), as well as to assess the antimicrobial activity, physical, optical, microstructure and molecular properties in the films. An interaction between the ingredients was observed at the molecular level by FTIR. The amide II and amide III bands, which are important to verify collagen conformation, showed intense peaks in the films. The formation of a network through collagen fibers was produced, acting as a reinforcement in matrix. The films with essential oil had an expressive antimicrobial activity by the steam contact method (micro-atmosphere), mainly for Escherichia coli and Staphylococcus aureus. The mixture of collagen fiber plus polyvinyl alcohol added of essential oils is a promising matrix for application in food as active packaging.
文摘The objective of the study was to characterize the clays of the Lama depression in Benin. Macroscopic examination of hand soundings, dynamic penetration test and stratigraphic correlation of water borehole logs, as well as scanning electron microscopy (SEM) combined with energy-dispersive X-ray microanalysis (EDX) method were made on compact or stratified clays. The large grains are embedded in a sintered matrix. The texture is heterogeneous and open, including quartz, carbonates and organic matter. The fine fraction is dominated by mineral paragenesis characterizing Kaolinite-Quartz-Calcite-Gypsum dioctahedral smectites composed of: Oxygen, Silica, Carbon, Aluminum, Iron, Zinc, Titanium and Magnesium. This smectic and regular structure includes coarse grains of the order of 800 μm. The pore diameters vary from 130 μm to 1.14 μm. The inter-particle porosity is poorly developed unlike the inter-aggregate pores larger than 0.05 μm. The texture is laminar and shows elongated turbo static particles with more or less rounded edges and honeycomb particles. Quartz and carbonates induce an increase in heterogeneities which develop mechanical sensitivity and hydraulic conductivity. High contents of silica, iron or aluminum and low contents of calcium and magnesium, as well as the presence of other trace elements suggest an alumino-ferriferous clay resulting from the hydrothermal alteration of the acid granite massif. These heterogeneities promote less tortuous pores or paths, making these clays more permeable. Finally, other stabilization studies and improvements to hydraulic products and binders should favor the use of the studied clay as improved backfill or drilling muds.
