For present solid oxide fuel cells(SOFCs),rapid performance degradation is observed in the initial aging process,and the dis-cussion of the degradation mechanism necessitates quantitative analysis.Herein,focused ion b...For present solid oxide fuel cells(SOFCs),rapid performance degradation is observed in the initial aging process,and the dis-cussion of the degradation mechanism necessitates quantitative analysis.Herein,focused ion beam-scanning electron microscopy was em-ployed to characterize and reconstruct the ceramic microstructures of SOFC anodes.The lattice Boltzmann method(LBM)simulation of multiphysical and electrochemical processes in the reconstructed models was performed.Two samples collected from industrial-size cells were characterized,including a reduced reference cell and a cell with an initial aging process.Statistical parameters of the reconstructed microstructures revealed a significant decrease in the active triple-phase boundary and Ni connectivity in the aged cell compared with the reference cell.The LBM simulation revealed that activity degradation is dominant compared with microstructural degradation during the initial aging process,and the electrochemical reactions spread to the support layer in the aged cell.The microstructural and activity de-gradations are attributed to Ni migration and coarsening.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
The three-dimensional(3D)pore structures and permeability of shale are critical for forecasting gas production capacity and guiding pressure differential control in practical reservoir extraction.However,few investiga...The three-dimensional(3D)pore structures and permeability of shale are critical for forecasting gas production capacity and guiding pressure differential control in practical reservoir extraction.However,few investigations have analyzed the effects of microscopic organic matter(OM)morphology and 3D pore nanostructures on the stress sensitivity,which are precisely the most unique and controlling factors of reservoir quality in shales.In this study,ultra-high nanoscale-resolution imaging experiments,i.e.focused ion beam-scanning electron microscopy(FIB-SEMs),were conducted on two organic-rich shale samples from Longmaxi and Wufeng Formations in northern Guizhou Depression,China.Pore morphology,porosity of 3D pore nanostructures,pore size distribution,and connectivity of the six selected regions of interest(including clump-shaped OMs,interstitial OMs,framboidal pyrite,and microfractures)were qualitatively and quantitatively characterized.Pulse decay permeability(PDP)measurement was used to investigate the variation patterns of stress-dependent permeability and stress sensitivity of shales under different confining pressures and pore pressures,and the results were then used to calculate the Biot coefficients for the two shale formations.The results showed that the samples have high OM porosity and 85%of the OM pores have the radius of less than 40 nm.The OM morphology and pore structure characteristics of the Longmaxi and Wufeng Formations were distinctly different.In particular,the OM in the Wufeng Formation samples developed some OM pores with radius larger than500 nm,which significantly improved the connectivity.The macroscopic permeability strongly depends on the permeability of OM pores.The stress sensitivity of permeability of Wufeng Formation was significantly lower than that of Longmaxi Formation,due to the differences in OM morphology and pore structures.The Biot coefficients of 0.729 and 0.697 were obtained for the Longmaxi and Wufeng Formations,respectively.展开更多
The sealing performance of a bentonite barrier is highly dependent on its seepage characteristics, which are directly related to the characteristics of its pore structure. Based on scanning electron microscopy(SEM) an...The sealing performance of a bentonite barrier is highly dependent on its seepage characteristics, which are directly related to the characteristics of its pore structure. Based on scanning electron microscopy(SEM) and focused ion beam-SEM(FIB-SEM), the pore structure of bentonite was characterized at different scales. First, a reasonable gray threshold was determined through back analysis, and the image was binarized based on the threshold. In addition, binary images were used to analyze bentonite’s pore structure(porosity and pore size distribution). Furthermore, the effects of different algorithms on the pore structure characterization were evaluated. Then, permeability calculations were performed based on the previous pore structure characteristics and a modified permeability prediction model. For permeability prediction based on the three-dimensional model, the effect of pore tortuosity was also considered. Finally, the accuracy of numerical calculations was verified by conducting macroscopic gas and alcohol permeability experiments. This approach provides a better understanding of the microscale mechanism of gas transport in bentonite and the importance of pore structures at different scales in determining its seepage characteristics.展开更多
Human dental hard tissues are dentine, cementum, and enamel. These are hydrated mineralised composite tissues with a hierarchical structure and versatile thermo-mechanical properties. The hierarchical structure of den...Human dental hard tissues are dentine, cementum, and enamel. These are hydrated mineralised composite tissues with a hierarchical structure and versatile thermo-mechanical properties. The hierarchical structure of dentine and enamel was imaged by transmission electron microscopy （TEM） of samples prepared by focused ion beam （FIB） milling. High resolution TEM was carried out in the vicinity of a crack tip in dentine. An intricate ＂random weave＂ pattern of hydroxyapatile crystallites was observed and this provided a possible explanation for toughening of the mineralized dentine tissue at the nano-scale. The results reported here provide the basis for improved understanding of the rela- tionship between the multi-scale nature and the mechanical properties of hierarchically structured biomaterials, and will also be useful for the development of better prosthetic and dental restorative materials.展开更多
将聚焦离子束和扫描电子显微镜相整合而形成的双束系统——聚焦离子束扫描电子显微镜(Focused Ion Beam-Scanning Electron Microscopy,FIB-SEM)已成为对生物样品的超微结构进行成像和定量分析的有力工具。该系统既能对硬质生物材料进...将聚焦离子束和扫描电子显微镜相整合而形成的双束系统——聚焦离子束扫描电子显微镜(Focused Ion Beam-Scanning Electron Microscopy,FIB-SEM)已成为对生物样品的超微结构进行成像和定量分析的有力工具。该系统既能对硬质生物材料进行铣削,又能在纳米尺度完成对其三维结构的重建。更为重要的是,它还能将组织或器官的宏观形态与组成细胞的内部结构直接关联。本文介绍了FIB-SEM的工作原理和设备组成,对FIB-SEM三维成像在肿瘤及肿瘤干细胞模型、生物打印系统的铣削、成像和超微结构分析,以及癌细胞对纳米颗粒的摄入等肿瘤生物学领域的典型应用进行了概述,并对利用FIB-SEM三维定量和超微结构分析的方法研究线粒体和其他亚细胞结构与癌症发生的关系提出了展望。目的是强化FIB-SEM在肿瘤生物学领域的应用,以揭示肿瘤细胞超微形态和结构变化对肿瘤演进所起的作用,为肿瘤治疗提供新靶标。展开更多
聚焦离子束连续切片扫描电镜(focused ion beam serial block face scanning electron microscopy,FIB-SEM)技术,目前已被广泛应用于小体积细胞或组织样品的三维重构,具有自动化程度高、Z轴分辨高等优点。本文从包埋块样品准备与处理、...聚焦离子束连续切片扫描电镜(focused ion beam serial block face scanning electron microscopy,FIB-SEM)技术,目前已被广泛应用于小体积细胞或组织样品的三维重构,具有自动化程度高、Z轴分辨高等优点。本文从包埋块样品准备与处理、样品区域选定、软件设置前准备、软件参数(离子束加工和电子束扫描)设置、软件运行与图像采集和图像处理等多个方面,详细介绍应用FIB-SEM技术对常温生物包埋块样品进行三维重构的流程和细节,并对某些关键性参数展开讨论。展开更多
体电子显微成像技术(volume electron microscopy)可以在更大三维空间中对样品进行纳米分辨率三维结构分析,获取样品内部结构的三维模型和各结构之间的位置关系、体积比例等信息,更加全面地反映样品的超微结构与功能的关系。本文利用基...体电子显微成像技术(volume electron microscopy)可以在更大三维空间中对样品进行纳米分辨率三维结构分析,获取样品内部结构的三维模型和各结构之间的位置关系、体积比例等信息,更加全面地反映样品的超微结构与功能的关系。本文利用基于聚焦离子束扫描电镜的体电子显微成像技术对人源肝癌细胞的三维超微结构进行分析,获得了多种细胞器包括细胞核、线粒体、内质网和高尔基体等的高分辨率三维结构模型。展开更多
The combined use of focused ion beam(FIB)milling and field-emission scanning electron microscopy inspection(FESEM)is a unique and successful approach for assessment of near-surface phenomena at specific and selected l...The combined use of focused ion beam(FIB)milling and field-emission scanning electron microscopy inspection(FESEM)is a unique and successful approach for assessment of near-surface phenomena at specific and selected locations.In this study,a FIB/FESEM dual-beam platform was implemented to docment and analyze the wear micromechanisms on a laser-surface textured(LST)hardmetal(HM)tool.In particular,changes in surface and microstructural integrity of the laser-sculptured pyramids(effective cutting microfeatures)were characterized after testing the LST-HM tool against a steel workpiece in a workbench designed to simulate an external honing process.It was demonstrated that:(1)laser-surface texturing does not degrade the intrinsic surface integrity and tool effectiveness of HM pyramids;and(2)there exists a correlation between the wear and loading of shaped pyramids at the local level.Hence,the enhanced performance of the laser-textured tool should consider the pyramid geometry aspects rather than the microstructure assemblage of the HM grade used,at least for attempted abrasive applications.展开更多
基金the National Key R&D Program of China(No.2018YFB1502201)the Guangdong Basic and Applied Basic Research Foundation,China(No.2020A1515010551).
文摘For present solid oxide fuel cells(SOFCs),rapid performance degradation is observed in the initial aging process,and the dis-cussion of the degradation mechanism necessitates quantitative analysis.Herein,focused ion beam-scanning electron microscopy was em-ployed to characterize and reconstruct the ceramic microstructures of SOFC anodes.The lattice Boltzmann method(LBM)simulation of multiphysical and electrochemical processes in the reconstructed models was performed.Two samples collected from industrial-size cells were characterized,including a reduced reference cell and a cell with an initial aging process.Statistical parameters of the reconstructed microstructures revealed a significant decrease in the active triple-phase boundary and Ni connectivity in the aged cell compared with the reference cell.The LBM simulation revealed that activity degradation is dominant compared with microstructural degradation during the initial aging process,and the electrochemical reactions spread to the support layer in the aged cell.The microstructural and activity de-gradations are attributed to Ni migration and coarsening.
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 Key R&D Program of China(Grant No.2020YFA0711802)the Strategic Program of Chinese Academy of Sciences(Grant No.XDB10030400)。
文摘The three-dimensional(3D)pore structures and permeability of shale are critical for forecasting gas production capacity and guiding pressure differential control in practical reservoir extraction.However,few investigations have analyzed the effects of microscopic organic matter(OM)morphology and 3D pore nanostructures on the stress sensitivity,which are precisely the most unique and controlling factors of reservoir quality in shales.In this study,ultra-high nanoscale-resolution imaging experiments,i.e.focused ion beam-scanning electron microscopy(FIB-SEMs),were conducted on two organic-rich shale samples from Longmaxi and Wufeng Formations in northern Guizhou Depression,China.Pore morphology,porosity of 3D pore nanostructures,pore size distribution,and connectivity of the six selected regions of interest(including clump-shaped OMs,interstitial OMs,framboidal pyrite,and microfractures)were qualitatively and quantitatively characterized.Pulse decay permeability(PDP)measurement was used to investigate the variation patterns of stress-dependent permeability and stress sensitivity of shales under different confining pressures and pore pressures,and the results were then used to calculate the Biot coefficients for the two shale formations.The results showed that the samples have high OM porosity and 85%of the OM pores have the radius of less than 40 nm.The OM morphology and pore structure characteristics of the Longmaxi and Wufeng Formations were distinctly different.In particular,the OM in the Wufeng Formation samples developed some OM pores with radius larger than500 nm,which significantly improved the connectivity.The macroscopic permeability strongly depends on the permeability of OM pores.The stress sensitivity of permeability of Wufeng Formation was significantly lower than that of Longmaxi Formation,due to the differences in OM morphology and pore structures.The Biot coefficients of 0.729 and 0.697 were obtained for the Longmaxi and Wufeng Formations,respectively.
基金support of the National Natural Science Foundation of China (Grant Nos. 52174133 and 51809263)China Atomic Energy Authority。
文摘The sealing performance of a bentonite barrier is highly dependent on its seepage characteristics, which are directly related to the characteristics of its pore structure. Based on scanning electron microscopy(SEM) and focused ion beam-SEM(FIB-SEM), the pore structure of bentonite was characterized at different scales. First, a reasonable gray threshold was determined through back analysis, and the image was binarized based on the threshold. In addition, binary images were used to analyze bentonite’s pore structure(porosity and pore size distribution). Furthermore, the effects of different algorithms on the pore structure characterization were evaluated. Then, permeability calculations were performed based on the previous pore structure characteristics and a modified permeability prediction model. For permeability prediction based on the three-dimensional model, the effect of pore tortuosity was also considered. Finally, the accuracy of numerical calculations was verified by conducting macroscopic gas and alcohol permeability experiments. This approach provides a better understanding of the microscale mechanism of gas transport in bentonite and the importance of pore structures at different scales in determining its seepage characteristics.
基金supported by EPSRC through grants"Multi-disciplinary Centre for In-situ Processing Studies(CIPS)"(EP/I020691),"Micromechanical Modelling and Experimentation"(EP/G004676),and "New Dimensions of Engineering Science at Large Facilities"(EP/H003215)
文摘Human dental hard tissues are dentine, cementum, and enamel. These are hydrated mineralised composite tissues with a hierarchical structure and versatile thermo-mechanical properties. The hierarchical structure of dentine and enamel was imaged by transmission electron microscopy （TEM） of samples prepared by focused ion beam （FIB） milling. High resolution TEM was carried out in the vicinity of a crack tip in dentine. An intricate ＂random weave＂ pattern of hydroxyapatile crystallites was observed and this provided a possible explanation for toughening of the mineralized dentine tissue at the nano-scale. The results reported here provide the basis for improved understanding of the rela- tionship between the multi-scale nature and the mechanical properties of hierarchically structured biomaterials, and will also be useful for the development of better prosthetic and dental restorative materials.
文摘将聚焦离子束和扫描电子显微镜相整合而形成的双束系统——聚焦离子束扫描电子显微镜(Focused Ion Beam-Scanning Electron Microscopy,FIB-SEM)已成为对生物样品的超微结构进行成像和定量分析的有力工具。该系统既能对硬质生物材料进行铣削,又能在纳米尺度完成对其三维结构的重建。更为重要的是,它还能将组织或器官的宏观形态与组成细胞的内部结构直接关联。本文介绍了FIB-SEM的工作原理和设备组成,对FIB-SEM三维成像在肿瘤及肿瘤干细胞模型、生物打印系统的铣削、成像和超微结构分析,以及癌细胞对纳米颗粒的摄入等肿瘤生物学领域的典型应用进行了概述,并对利用FIB-SEM三维定量和超微结构分析的方法研究线粒体和其他亚细胞结构与癌症发生的关系提出了展望。目的是强化FIB-SEM在肿瘤生物学领域的应用,以揭示肿瘤细胞超微形态和结构变化对肿瘤演进所起的作用,为肿瘤治疗提供新靶标。
文摘聚焦离子束连续切片扫描电镜(focused ion beam serial block face scanning electron microscopy,FIB-SEM)技术,目前已被广泛应用于小体积细胞或组织样品的三维重构,具有自动化程度高、Z轴分辨高等优点。本文从包埋块样品准备与处理、样品区域选定、软件设置前准备、软件参数(离子束加工和电子束扫描)设置、软件运行与图像采集和图像处理等多个方面,详细介绍应用FIB-SEM技术对常温生物包埋块样品进行三维重构的流程和细节,并对某些关键性参数展开讨论。
文摘体电子显微成像技术(volume electron microscopy)可以在更大三维空间中对样品进行纳米分辨率三维结构分析,获取样品内部结构的三维模型和各结构之间的位置关系、体积比例等信息,更加全面地反映样品的超微结构与功能的关系。本文利用基于聚焦离子束扫描电镜的体电子显微成像技术对人源肝癌细胞的三维超微结构进行分析,获得了多种细胞器包括细胞核、线粒体、内质网和高尔基体等的高分辨率三维结构模型。
基金supported by the German Research Foundation(DFG)within the Individual Research Grant(425923019)“Laser Surface Textured Cemented Carbides for Application in Abrasive Machining Processes”.
文摘The combined use of focused ion beam(FIB)milling and field-emission scanning electron microscopy inspection(FESEM)is a unique and successful approach for assessment of near-surface phenomena at specific and selected locations.In this study,a FIB/FESEM dual-beam platform was implemented to docment and analyze the wear micromechanisms on a laser-surface textured(LST)hardmetal(HM)tool.In particular,changes in surface and microstructural integrity of the laser-sculptured pyramids(effective cutting microfeatures)were characterized after testing the LST-HM tool against a steel workpiece in a workbench designed to simulate an external honing process.It was demonstrated that:(1)laser-surface texturing does not degrade the intrinsic surface integrity and tool effectiveness of HM pyramids;and(2)there exists a correlation between the wear and loading of shaped pyramids at the local level.Hence,the enhanced performance of the laser-textured tool should consider the pyramid geometry aspects rather than the microstructure assemblage of the HM grade used,at least for attempted abrasive applications.
