FIB-SEM Images Research Articles

Correction to: A quantified study of segmentation techniques on synthetic geological XRM and FIB-SEM images

The original version of this article unfortunately contained mistakes introduced during the production process. The corrections are given in the following list: (1) Figure 6 was missing.

A quantified study of segmentation techniques on synthetic geological XRM and FIB-SEM images

Three sets of synthetic images were created from two original datasets. A suite exhibiting greyscale contrast was produced from an 8.96-μm voxel size 3D X-ray microscopy image of a sandstone rock and a two suites (one showing greyscale contrast and one showing both greyscale and textural contrast) were produced from a 5 × 5 × 5 nm voxel size FIB-SEM image of a shale rock. The performance of three image segmentation algorithms (global multi-Otsu thresholding, seeded watershed region growing, and machine learning-based multivariant classification) was then assessed by their ability to recover their respective original segmented 3D images. While all algorithms performed well at low noise levels, machine learning-based classification proved significantly more noise tolerant than either of the traditional algorithms. It was also able to segment the non-greyscale (textural based) contrast, something the traditional completely failed to do, with voxel misclassification rates for the traditional techniques above 50% at a 0 noise level within the textural contrast regions. Machine learning-based classification, in contrast, achieved misclassification rates of less than 5% in the same regions.

Navigating the Fog: A Correlated XRM and FIB-SEM Imaging Pipeline for the Rapid and Precise Spatial Targeting of Rare Structures in Biological Samples

Navigating the Fog: A Correlated XRM and FIB-SEM Imaging Pipeline for the Rapid and Precise Spatial Targeting of Rare Structures in Biological Samples

Modeling and Experimental Studies of Mesoscopic Morphologies and Proton Conductivities of Cathode Catalyst Layers with Different Carbon Supports

Introduction Polymer electrolyte fuel cells (PEFCs) are considered to be promising for automotive and stationary power applications. One of the most important issues for PEFCs is the reduction of the Pt loading in the cathode catalyst layers (CCLs), which generally consist of carbon-supported Pt catalysts and ionomers. Carbon blacks are widely used as the support materials. It is well known that the performance of the CCL is greatly influenced by the type of carbon black. We need to deeply understand the relationships between the microstructure and the transport properties in order to improve the performance of the low-Pt-loaded CCL. Uchida et al. investigated the relationships between the microscopic (< 10 nm) morphologies of CCLs with different carbon blacks and their performances [1]. They revealed that the existence of Pt particles on the exterior surfaces of the carbon black particles and the uniform coverage of the ionomer on the carbon surfaces had a great impact on the performance at high current density. In the present study, we investigated the mesoscopic (10–200 nm) morphologies and the proton conductivities of the CCLs with different carbon blacks using experimental and modeling approaches. Experimental We used 30 wt% Pt on Ketjen black (surface area ca. 800 m2 g−1, Pt/CB800), graphitized Ketjen black (surface area ca. 150 m2 g−1, Pt/GCB150), an acetylene black (surface area ca. 800 m2 g−1, Pt/AB800), and a second acetylene black (surface area ca. 250 m2 g−1, Pt/AB250) as cathode catalysts. CCLs were fabricated by spraying inks with the cathode catalysts and ionomers (equivalent weight = 909 g eq−1) on 30-μm thick membranes. The Pt loading and the ionomer/carbon (I/C) weight ratio were controlled to be 0.4 mgPt cm−2 and 0.8, respectively. The pore size distributions (PSDs) of the CCLs were evaluated by mercury intrusion porosimetry. Anode catalyst layers with 0.1 mgPt cm−2 Pt loading and 0.8 I/C weight ratio were fabricated by spraying inks with 50 wt% Pt on Ketjen black catalysts and the ionomers. AC impedance measurements were performed at 0.5 V with a perturbation of 2 mV from 100 kHz to 0.1 Hz at 80°C and a 100% RH hydrogen feed to the anode (reference, counter electrode) and nitrogen to the cathode (working electrode). The proton conductivities of the CCLs were calculated from the 45° line of Nyquist plots, according to the literature [2]. Modeling The mesoscopic structure models of the CCLs were generated by the following two steps. First, the porous structures were reconstructed from the FIB-SEM images with a resolution of 4 nm. Then, the solid surfaces were uniformly coated with ionomer. The amount of the coated ionomer was determined by converting the I/C weight ratio to the I/C volume ratio, assuming that the apparent volume of the carbon black was the total volume of the solid phase and nanopores less than 10 nm. The PSDs were calculated from the volume of a non-wetting fluid which was pressed into the medium. The proton conductivities were calculated by Ohm’s Law, assuming that the protons transport through the ionomer regions with a proton conductivity of 10 S m−1, which is the bulk proton conductivity of the ionomer at 80°C and 100% RH. Results and Discussion Figure 1 shows the experimental and modeling results of the PSDs. The modeling results for the Pt/CB800 and the Pt/AB800 corresponded well with the experimental results. These results suggest that the uniform-ionomer-coating model is a good approximation for the CCLs using Pt/CB800 and Pt/AB800, while there were differences between the modeling results and the experimental results for Pt/GCB150 and Pt/AB250. It is considered that the ionomer was unevenly distributed in the CCLs using Pt/GCB150 and Pt/AB250. Figure 2 shows the experimental and modeling results of the proton conductivities. The modeling results for the Ketjen black-supported catalysts underestimated the proton conductivities, while those for the acetylene black-supported catalysts were overestimated. In particular, the deviations for Pt/CB800 and Pt/AB800 were large, in spite of the correspondences in these PSDs. It was suggested that the proton conductivities were influenced not only by the mesoscopic morphologies of the CCLs but also other factors, such as the microscopic (< 10 nm) morphologies and the chemical properties of the carbon surfaces. Acknowledgements This work was partially supported by funds for the SPer-FC Project from the New Energy and Industrial Technology Development Organization (NEDO) of Japan. References Y. C. Park, H. Tokiwa, K. Kakinuma, M. Watanabe, M. Uchida, J. Power Sources, 315 (2016) 179.R. Makharia, M. F. Mathias, D. R. Baker, J. Electrochem. Soc., 152 (5) (2005) A970. Figure 1

Droplet Imbibition into Paper Coating Layer: Pore-Network Modeling Simulation

Liquid penetration into thin porous media such as paper is often simulated using continuum-scale single-phase Darcy’s law. The underlying assumption was that a sharp invasion front percolates through the layer. To explore this ambiguous assumption and to understand the controlling pore-scale mechanisms, we have developed a dynamic pore-network model to simulate imbibition of a wetting phase from a droplet into a paper coating layer. The realistic pore structures are obtained using the FIB-SEM imaging of the coating material with a minimum resolution of 3.5 nm. Pore network was extracted from FIB-SEM images using Avizo software. Data of extracted pore network are used for statistically generating pore network. Droplet sizes are chosen in the range of those applicable in inkjet printing. Our simulations show no sharp invasion front exists and there is the presence of residual non-wetting phase. In addition, penetration of different sizes of droplets of different material properties into the pore network with different pore body and pore throat sizes are performed. We have found an approximately linear decrease in droplet volume with time. This contradicts the expected sqrt{t}-behavior in vertical imbibition that is obtained using macroscopic single-phase Darcy’s law. With increase in flow rate, transition of imbibition invasion front from percolation-like pattern to a more sharper one with less trapping of non-wetting phase is also reported. Our simulations suggest that the single-phase Darcy’s law does not adequately describe liquid penetration into materials such as paper coating layer. Instead Richards equation would be a better choice.

Enhanced mechanical stability of Ni-YSZ scaffold demonstrated by nanoindentation and Electrochemical Impedance Spectroscopy

The electrochemical performance of Ni-YSZ SOFC anodes can quickly degrade during redox cycling. Mechanical damage at interfaces significantly decreases the number of active triple phase boundaries. This study firstly focuses on the sintering temperature impact on YSZ scaffold mechanical properties. The YSZ scaffold sintered at 1200 °C exhibited 56% porosity, 28.3 GPa elastic modulus and 0.97 GPa hardness and was selected for further redox cycling study. The Ni infiltrated YSZ scaffold operated at 550 °C had an initial stabilized polarisation resistance equal to 0.62 Ω cm2 and only degraded to 2.85 Ω cm2 after 15 redox cycles. The active triple phase boundary density was evaluated by FIB-SEM tomography, and degraded from 28.54 μm−2 to 19.36 μm−2. The YSZ scaffold structure was robust after 15 redox cycles, as there was no observation of the framework fracturing in both SEM and FIB-SEM images, which indicated that the mechanical stability of YSZ scaffold improves the anode stability during redox cycling. Nonetheless, Ni agglomeration could not be prevented within Ni-YSZ scaffolds and this needs further consideration.

Pore structure characteristics of marine Silurian shales in the Sichuan Basin, China: Insights to reserve assessment and production design

Due to shortage of conventional resources, tight/shale oil/gas reservoirs have become increasingly important in balancing the energy consumption in China. As the most important shale reservoirs in China, marine Silurian shales in the Sichuan Basin have received intensive investigation during recent years in the area of pore structure characterization and reserve assessment. However, no work has been conducted to compare the China shale plays with other mature shale plays in the North America using multiple experimental methods based on the mineralogy analysis and organic geochemistry. In this paper, pore structure, formation porosity, total organic carbon (TOC), thermal maturity, and mineralogy of 36 samples in Longmaxi shale and 7 samples in Qiongzhusi shale have been investigated using multiple experimental methods. FIB-SEM imaging results show that Longmaxi shale gas reservoir include primary pores, residual intergranular pores, dissolution pores, and intergranular pores. The majority of the pores are distributed in residual intergranular pores, secondary dissolution pores, and intercrystalline pores, but less in primary intergranular pores. X-ray diffraction analysis shows that the clay minerals of Longmaxi shale reservoir mainly consist of illite and kaolinite, then followed by chlorite. The content of kaolinite is from 7.2% to 16.87%, and the average is 12.21%. The content of illite is from 8.03% to 26.8%, with the average of 16.1%. TOC tests show that most of the samples have their TOC more than 0.5%, which means Longmaxi formation has a potential to produce shale gas. Clay minerals mainly include quartz, K-feldspar, calcite, dolomite, anorthose, and pyrite. The quartz has the highest content value, followed by calcite, which are 29% and 22% average respectively. The content of pyrite and anorthose are less than 10%. The average content of brittle minerals of Longmaxi formation samples is 66% (>50%), which is suitable for hydraulic fracturing. Thermal maturity tests show that Vitrinite reflectance of each sample is more than 2.0%, which indicates that it is high enough to generate shale gas in the formation. Comparing with other mature shale plays, the Longmaxi and Qiongzhusi shale plays have lower porosity and lower TOC than that of the U.S. shale plays, and the quartz content and thermal maturity are similar. The Qiongzhusi shale and Longmaxi shale are over-mature (Ro>2.5%) compared with U.S. shale plays. The results of this study will contribute to the formation characteristics understanding and reserve assessment of China shale plays. Also, it will facilitate the development of suitable and efficient production plan for China shale plays.

Prediction of Effective Properties of Porous Carbon Electrodes from a Parametric 3D Random Morphological Model

Pore structures have a major impact on the transport and electrical properties of electrochemical devices, such as batteries and electric double-layer capacitors (EDLCs). In this work we are concerned with the prediction of the electrical conductivity, ion diffusivity and volumetric capacitance of EDLC electrodes, manufactured from hierarchically porous carbons. To investigate the dependence of the effective properties on the pore structures, we use a structurally resolved parametric model of a random medium. Our approach starts from 3D FIB-SEM imaging, combined with automatic segmentation. Then, a random set model is fitted to the segmented structures and the effective transport properties are predicted using full field simulations by iterations of FFT on 3D pore space images and calculations based on the geometric properties of the structure model. A parameter study of the model is used to investigate the sensitivity of the effective conductivity and diffusivity to changes in the model parameters. Finally, we investigate the volumetric capacitance of the EDLC electrodes with a geometric model, make a comparison with experimental measurements and do a parameter study to suggest improved microstructures.

Micro-CT and FIB–SEM imaging and pore structure characterization of dolomite rock at multiple scales

With improvements of imaging techniques and computational power, Digital Rock Physics (DRP) has been increasingly used to determine transport and elastic properties of reservoir core plugs. Since numerical computations highly rely on accurate 3D representations of the porous microstructure of the rocks, the imaging technique and the scale at which the imaging is performed is a critical parameter. In this paper, we introduce a multiscale imaging workflow that uses both micro-X-ray tomography (micro-XCT) and focused ion beam combined with scanning electron microscope (FIB–SEM) to characterize a dolomite rock from the microscale to the nanoscale. This allows for the accurate capture of the different heterogeneities that exist in the carbonate (texture, mineralogy, pore size). The reconstructed microporous structures were then used to successfully predict elastic and permeability properties of selected carbonate.

Improving FIB-SEM Reconstructions by Using Epoxy Resin Embedding

Segmentation of FIB-SEM data remains a major challenge to achieving accurate reconstructions. Epoxy embedding is used in this article to eliminate background data from SEM images in order to aid in segmentation and generate 3D reconstructions of conventional high surface area CLs from FIB-SEM images. Two CL samples with the same composition but different hours of operation, namely, beginning of life (BOL), i.e. post conditioning, and end of life (EOL), i.e., post failure, were used. The samples were imaged with and without epoxy embedding to characterize the difference in the structure of the sample due to sample preparation. Further, the use of two CL samples allowed the quantification of the differences in the structure of the CL due to degradation and ensure validity of the sample preparation across multiple CL samples. Image analysis showed that a simple thresholding algorithm, such as Otsu, was sufficient to accurately segment the images for the sample with epoxy embedding due to the lack of background features. Statistical descriptors, such as porosity, two-point correlation function, chord length function, specific interface area and pore size distribution, and effective diffusion coefficient are used to quantify the differences in the reconstructed structures of the CLs with different sample preparation. Results showed that the CL reconstructions of the epoxy embedded samples had a higher porosity, larger pore sizes and lower specific interface area due to the more accurate segmentation and removal of background features.

Analysis of Void Volume in Composite Electrode of All-solid-state Lithium-ion Battery Employing FIB-SEM and Union Operation Image Processing

Analysis of Void Volume in Composite Electrode of All-solid-state Lithium-ion Battery Employing FIB-SEM and Union Operation Image Processing

Microstructure and spatial distribution of corrosion products anodically grown on zinc in chloride solutions

Zinc substrates were electrochemically oxidized in NaCl solution to produce corrosion patinas. XRD, XPS and Raman analyses enabled the identification of simonkolleite and zinc oxide as the patina constituents. FIB-SEM imaging shows that the upper part of the patinas is a network of simonkolleite nanosheets with an open microstructure that is unlikely to act as a significant barrier for corrosion processes. STEM investigations and Raman mapping measurements reveal the presence of a ca. 20–400nm thin nanoporous ZnO-rich film below the simonkolleite and covering the zinc substrate. Under potentiostatic conditions, the reduced cathodic activity of the patina-covered zinc electrodes is assigned to this nanoporous ZnO layer.

A 3D coupled model of organic matter and inorganic matrix for calculating the permeability of shale

Microstructure-based quantitative computation of the shale permeability is challenging due to the presence of organic matter with nanoporous features. In this study, a new three-dimensional (3D) coupled model is proposed to investigate the micro-scale permeability of organic-rich-shale matrix. The coupled model consists of two subdomains, organic matter and inorganic matrix. They are described by the pore network model (PNM) and continuum model to capture the non-Darcy and Darcy flow, respectively, and the gas flow in the two subdomains are coupled by finite element mortars (Mortar). The convergence error, grid discretization and parallel scheme are also investigated to get the optimal computing parameters for this model. Then, the effects of the total organic content (TOC), kerogen distribution and pore-size distribution on the apparent permeability (AP) of shale matrix are studied using the coupled model with computer-generated PNMs. And on the basis of FIB-SEM images, a Longmaxi shale sample from the Sichuan Basin, China is introduced to build a real shale model. Results show that AP is more sensitive to TOC and pore-size distribution than kerogen distribution. Additionally, in order to analyze the necessity of 3D model, a comparison of 3D and two-dimensional (2D) model is made and the error of 2D model is pointed out. The 3D couple model affords a foundation for further upscaling of shale permeability to REV scale and reservoir scale.

Multi-scale structural analysis of gas diffusion layers

Abstract The macroscopic properties of materials are strongly determined by their micro structure. Here, transport properties of gas diffusion layers (GDL) for fuel cells are considered. In order to simulate flow and thermal properties, detailed micro structural information is essential. 3D images obtained by high-resolution computed tomography using synchrotron radiation and scanning electron microscopy (SEM) combined with focused ion beam (FIB) serial slicing were used. A recent method for reconstruction of porous structures from FIB-SEM images and sophisticated morphological image transformations were applied to segment the solid structural components. The essential algorithmic steps for segmenting the different components in the tomographic data-sets are described and discussed. In this paper, two types of GDL, based on a non-woven substrate layer and a paper substrate layer were considered, respectively. More than three components are separated within the synchrotron radiation computed tomography data. That is, fiber system, polytetrafluoroethylene (PTFE) binder/impregnation, micro porous layer (MPL), inclusions within the latter, and pore space are segmented. The usage of the thus derived 3D structure data in different simulation applications can be demonstrated. Simulations of macroscopic properties such as thermal conductivity, depending on the flooding state of the GDL are possible.

Characterizing the hydraulic properties of paper coating layer using FIB-SEM tomography and 3D pore-scale modeling

Paper used in the printing industry generally contains a relatively thin porous coating covering a thicker fibrous base layer. The three-dimensional pore structure of coatings has a major effect on fluid flow patterns inside the paper medium. Understanding and quantifying the flow properties of thin coating layers is hence crucial. Pore spaces within the coating have an average size of about 180nm. We used scanning electron microscopy combined with focused ion beam (FIB-SEM) to visualize the nano-scale pore structure of the paper coating layer. Post-processing of the FIB-SEM images allowed us to reconstruct the three-dimensional pore space of the coating. The 3D FIB-SEM images were analyzed in detail to obtain pore size distribution and porosity value. The permeability was estimated using the GeoDict software, based on solutions of the Stokes equation. By determining the porosity and permeability of increasingly larger domain sizes, we estimated the size of a representative elementary volume (REV) for the coating layer to be 60µm3, which is well within the volume analyzed using FIB-SEM. The estimated porosity and permeability of the REV domain were 0.34 and 0.09 mDarcy, respectively. Using the pore morphology method, capillary pressure-saturation (Pc-S) and relative permeability curves of the REV domain could be constructed next. The Pc-S curves showed that the coating had a high air entry suction, which is very favorable for printing in that ink will invade the coating as soon as it is applied to the coating. Our results are essential for macroscale modelling of ink penetration into a coating layer during inkjet printing. Macroscopic models can be valuable tools for optimization of the penetration depth and the spreading of ink on and within paper substrates.

Submicron size-scale mapping of carbonate effective elastic properties from FIB-SEM images and finite element method

In this paper, an automatic unstructured focused ion beam (FIB) and scanning electron microscopy (SEM) images induced representative volume element (RVE) finite element (FE) method is developed to predict submicron scale carbonate rock effective Young’s and bulk moduli and Poisson’s ratio on parallel CPU-GPU platform. Based on high resolution-contrast surface morphology and internal fabric-texture structure images from carbonate rock specimen (covered 0.12–64 μm2 area and 8000 μm3 domain), the cubic RVE FE models are constructed from different sites through Avizo with user-defined parameters Matlab coding. The effective Young’s and bulk moduli and Poisson’s ratio of the different RVEs and porosity and pore size are computed by using periodic boundary condition in the well-known FE software Abaqus. FE mesh sensitivity analysis has been conducted where all moduli converge to a certain constant value at larger FE mesh density. The effect of fabric-texture (pore size, shape, and distribution) on the elastic properties is discussed. The correlations between the computed effective elastic properties and pore size, porosity, RVE size have been established. The simulation results show that the effective Young’s and bulk moduli and Poisson’s ratio have strong anisotropic behavior and depend on RVE size, porosity and pore size. The RVE size, porosity and pore size are three independent factors in affecting of the effective elastic moduli, the effect mechanism of porosity and pore size is same while the effect mechanism of RVE size is difference.

Characterization of gas transport behaviors in shale gas and tight gas reservoirs by digital rock analysis

Due to the extremely tiny pore size of tight gas and shale gas reservoir, the modified Darcy’s law in which the intrinsic permeability is replaced by the apparent permeability that can be obtained by a function of three transport parameters (intrinsic permeability, porosity and tortuosity), is used to describe the combined mechanisms of viscous flow, Knudsen diffusion, the effect of the adsorbed layer thickness and surface diffusion through the adsorbed layer. A new apparent permeability estimation method based on digital rock was proposed in this paper. The digital rock with nanopores could be constructed by 3D pore structure images obtained from micro/nano CT and FIB-SEM images directly or reconstructed with Markov Chain Monte Carlo (MCMC) method from the 2D SEM images of pore structure; then Lattice Boltzmann method can be applied to calculate the intrinsic permeability, porosity and tortuosity of 3D digital rock. These parameters are used to calculate the apparent permeability under consideration of different combined gas transport mechanisms. This method is applied to samples from the shale gas reservoir in Silurian Longmaxi Formation of Sichuan Basin and from the tight gas reservoir in the Wenchang Formation of Huizhou Sag. The results show that all considered transport mechanisms greatly impact the shale apparent permeability and cannot be ignored in shale samples. In tight gas reservoirs, Knudsen diffusion is an important mechanism at low pressures of less than 1MPa. However, Knudsen diffusion could be ignored when pressure is greater than 1MPa due to its smaller impact.

Three dimensional characterization and quantitative connectivity analysis of micro/nano pore space

Abstract Evaluation is performed on pore connectivity of unconventional reservoirs using 3-D FIB-SEM imaging characterization and digital rock techniques. 3-D images are first obtained by FIB-SEM device and then transformed into digital pore structure model through shape correction, brightness correction, depth-of-field correction and phase distinguishing. Based on this model, a new connectivity evaluation method for micro/nano pores in unconventional reservoirs is proposed. This method differentiates dead and live pore space, grades live connected domains (1-grade is the worst and 3-grade is the best) and calculates the connectivity rates of all grades. Selected connected domains can be quantitatively characterized through statistical analysis of connected domain distribution, volume and shape. The applications on nano material, shale and carbonate get distinctive connectivity rates (96%, 22% and 82%) and characteristic differences on connected domain distribution, volume and shape. Through these statistical parameters (connectivity rate, connected domain distribution, volume and shape), the three demonstrated materials and reservoirs are quantitatively characterized and differentiated. Thus, validity of the proposed connectivity method in this paper is proved.

3-D Analysis of a Copper Flip-Chip Interconnection Using FIB-SEM Slice and View

Abstract A detailed analysis based on FIB etching and SEM image capture was conducted on a flip-chip solder joint deep inside a tablet PC. 3D views reconstructed from SEM images show what appears to be a copper pillar with a solder cap connected to a copper trace on the substrate. The investigators believe the joint was formed by thermal compression bonding with a preapplied underfill. The analysis also revealed the presence of voids and intermetallic compounds along with signs of filler entrapment.

Petrophysical properties characterization of Ordovician Utica gas shale in Quebec, Canada

Abstract With multiple techniques, the following measurements and analysis were made to characterize the Ordovician Utica shale samples: mineralogy, porosity, microstructure, and surface wettability etc. The test of mercury injection apparatus showed that the pore size of Utica shale is 15−200 nm. X-ray diffraction (XRD) mineralogy analysis and Energy-Dispersive X-ray Spectroscopy (EDS) indicated that in Utica shale non-clay minerals are dominated by calcite and quartz, while clay minerals by illite and chlorite. With the images from scanning electron microscope (SEM), the surface microstructure examination showed various types of pores exist in Utica shale, such as intragranular, intergranular, organic etc. And the pores in organic matter (kerogen) were found in nanometer size (10 to 50 nm). A three-dimensional tomography model and a geometry model of the pores space using FIB-SEM imaging tomography were reconstructed with 250 SEM images. It provides visual insights into the petrophysical properties of Utica shale. Finally, the wettability tests displayed that Utica shale has weak-water wet to intermediate wettability.