Focused Ion Beam Scanning Electron Microscopy Research Articles

Microstructural Analysis of Organic-Rich Shales: Insights from an Electron Microscopic Study by Application of FIBSEM and TEM

Matrix-related pores play a significant role in controlling hydrocarbon production in organic-rich shales. Multiple matrix-related pore types of typical marine shales in the Sichuan Basin have been visually investigated and identified by transmission electron microscopy (TEM) on ultra-thin sections and by focused ion beam-scanning electron microscopy (FIBSEM) on polished sections. OM-hosted pores seem universal and range in sizes from below 1 nm to hundreds of nanometers and they are not homogeneously developed and distributed, which is mainly determined by thermal maturity and OM composition. Mineral-hosted pores are defined by mineral frameworks and occur in open spaces related to ductile or rigid grain fabric. The four porous mineral types that occur are clay intrapores, carbonate solvopores, pyrite interpores, and quartz interpores, and they range in size from less than 1 nm to more than several microns. Aggregate-hosted pores are predominantly associated with clay-organic aggregates, pyrite-organic aggregates, clay-pyrite aggregates, and clay-organic-pyrite aggregates. The most common aggregate-hosted pore networks are defined by clay-organic aggregates, and the pores are largely developed between the clay and organic layers and may be the important adsorption spaces for methane. Fracture-related pores include microchannels and microfractures of various sizes and shapes and they could play a key role in providing hydrocarbon migration pathways. FIBSEM and TEM show direct evidence that OM-hosted pores and fracture-related pores contribute more to the effective pore network and the excellent reservoir quality, whereas poor reservoir quality may come from aggregate-hosted pores.

Cortical synapses of the world's smallest mammal: An FIB/SEM study in the Etruscan shrew.

The main aim of the present study was to determine if synapses from the exceptionally small brain of the Etruscan shrew show any peculiarities compared to the much larger human brain. We analyzed the cortical synaptic density and a variety of structural characteristics of 7,239 3D reconstructed synapses, using using Focused Ion Beam/Scanning Electron Microscopy (FIB/SEM). We found that someof the general synaptic characteristics are remarkably similar to those found in the human cerebral cortex. However, the cortical volume of the human brain is about 50,000 times larger than the cortical volume of the Etruscan shrew, while the total number of cortical synapses in human is only 20,000 times the number of synapses in the shrew, and synaptic junctions are 35% smaller in the Etruscan shrew. Thus, the differences in the number and size of synapses cannot be attributed to a brain size scaling effect but rather to adaptations of synaptic circuits to particular functions.

FIB-SEM analysis on three-dimensional structures of growing organelles in wild Chlorella pyrenoidosa cells.

To clarify dynamic changes of organelle microstructures in Chlorella pyrenoidosa cells during photosynthetic growth with CO2 fixation, three-dimensional (3D) organelle microstructures in three growth periods of meristem, elongation, and maturity were quantitatively determined and comprehensively reconstructed with focused ion beam scanning electron microscopy (FIB-SEM). The single round-pancake mitochondria in each cell split into a dumbbell and then into a circular ring, while the barycenter distance of mitochondria to chloroplast and nucleus was reduced to 45.5% and 88.3% to strengthen energy transfer, respectively. The single pyrenoid consisting of a large part and another small part in each chloroplast gradually developed to a mature state in which the two parts were nearly equal in size. The nucleolus progressively became larger with euchromatin replication. The number of starch grains gradually increased, but the mean grain volume remained nearly unchanged.

Surface film formation on Mg electrode containing magnesium polysulfides in TFSI-based electrolytes

A rechargeable magnesium sulfur battery is an attractive redox couple due to the natural abundance of electrode active components and the possibility to offer a suitable energy density at a low price. The sulfur conversion mechanism in the magnesium battery is well known, however, several issues such as the large overpotential, fast capacity fading, and slow reaction kinetics are still under debate and should be properly addressed. At least partially, these problems are related to the passivation of the magnesium surface, due to the interaction with electrolyte/catholyte. Here, we explore the Mg2+ deposition/dissolution process on the Mg metal electrode in the presence of Mg(TFSI)2/MgCl2 in TEGDME:DOL and MgS8/Mg(TFSI)2/MgCl2 in TEGDME:DOL electrolytes. We show that an interfacial layer in the presence of polysulfides is less resistive, due to the joint corrosion nature of chlorides and sulfides. This has been confirmed in a combined study using conventional electrochemical experimental techniques supported by modeling of EIS spectra, X-ray photoelectron spectroscopy (XPS), and focused ion beam-scanning electron microscopy (FIB-SEM).

Restructuring in high burn-up pressurized water reactor UO2 fuel central parts: Experimental 3D characterization by focused ion beam—scanning electron microscopy

Focussed ion beam - scanning electron microscope (FIB-SEM) 3D examination was conducted on three standard UO2 and one Cr doped UO2 high burn-up pressurized water reactor (PWR) fuel samples. This work complemented other microanalysis examination, including an electron backscattered diffraction (EBSD) work on the polished surface. A parallel article giving the EBSD results was submitted simultaneously. Together, they found, in all the central area of these high burn-up samples: (i) a restructuring of the initial grains into smaller sub-grains forming low angle boundaries and with crystal orientations around that of their parent grains; and (ii) intragranular bubbles mostly situated on these low angle boundaries. The FIB-SEM 3D examination showed how such inter-sub-grain bubbles start as small compact but also small lenticular bubbles, similar to typical small intergranular lenticular bubbles. With increasing burn-up, these lenticular bubbles get thicker and locally interlink to form more complex bubbles. However, no long distance networks, between the sub-grains or between the original grains, were found. Such networks could have been a path for part of the fission gases to reach the grain boundaries, the grain edges (the intersection line of three grain boundaries), and the rod free volumes. These FIB-SEM 3D examinations brought details on the intragranular and intergranular bubbles situation for each studied volume. The distribution of the intragranular bubbles according to their sizes and shapes was exposed. The central restructuring, studied in this work, is likely to play a role in the increase of the fission gas release fractions at high burn-up. This work is an incentive to study further this restructuring and the bubbles formed, combining different approaches.

Focused ion beam-scanning electron microscopy links pathological myelin outfoldings to axonal changes in mice lacking Plp1 or Mag.

Healthy myelin sheaths consist of multiple compacted membrane layers closely encasing the underlying axon. The ultrastructure of CNS myelin requires specialized structural myelin proteins, including the transmembrane-tetraspan proteolipid protein (PLP) and the Ig-CAM myelin-associated glycoprotein (MAG). To better understand their functional relevance, we asked to what extent the axon/myelin-units display similar morphological changes if PLP or MAG are lacking. We thus used focused ion beam-scanning electron microscopy (FIB-SEM) to re-investigate axon/myelin-units side-by-side in Plp- and Mag-null mutant mice. By three-dimensional reconstruction and morphometric analyses, pathological myelin outfoldings extend up to 10μm longitudinally along myelinated axons in both models. More than half of all assessed outfoldings emerge from internodal myelin. Unexpectedly, three-dimensional reconstructions demonstrated that both models displayed complex axonal pathology underneath the myelin outfoldings, including axonal sprouting. Axonal anastomosing was additionally observed in Plp-null mutant mice. Importantly, normal-appearing axon/myelin-units displayed significantly increased axonal diameters in both models according to quantitative assessment of electron micrographs. These results imply that healthy CNS myelin sheaths facilitate normal axonal diameters and shape, a function that is impaired when structural myelin proteins PLP or MAG are lacking.

Sub‐Micrometre Resolution FIB‐SEM‐based ToF‐SIMS Used to Map Geochemical Zoning in Four Zircon Reference Materials

Zircon geochemistry can vary over micrometre scales; therefore, natural reference materials need to be well characterised before being used to calculate trace element mass fractions in unmeasured samples. Moreover, reference material homogeneity needs to be ensured with the accelerating rate of geoanalytical developments to map mineral chemistry at increasingly finer scales. Here, we investigate trace element zoning in four widely used zircon reference materials: 91500, Mud Tank, Temora and Plešovice, as well as zircon crystals from the Mount Dromedary/Gulaga Igneous Complex, Australia. Sub‐micrometre resolution focused ion beam scanning electron microscope (FIB‐SEM) based time‐of‐flight secondary ion mass spectrometry (ToF‐SIMS) and 5 μm resolution LA‐ICP‐MS mapping show that trace elements are zoned in all reference materials, though 91500 exhibited the least zonation. We demonstrate that FIB‐SEM‐based ToF‐SIMS can rapidly resolve variations in trace elements (e.g., U, Th, Sc, Y, Gd, Dy, Yb and Li) at sensitivities down to the μg g‐1 level with a spatial resolution of 195 nm for areas 100 × 85 μm to 959 × 828 μm. Zircon 91500 is recommended for future quantitative analyses provided that (1) the spatial distribution of elements is imaged before analysis of unknown samples and (2) it is used in conjunction with a doped glass as the primary reference material.

AGR-2 irradiated TRISO particle IPyC/SiC interface analysis using FIB-SEM tomography

The morphology in the interface region between the inner pyrolytic carbon layer (IPyC) and silicon carbide (SiC) layers in tristructural-isotropic (TRISO) particle fuel from the AGR-2 irradiation experiment were studied using focused ion beam-scanning electron microscopy tomography. This work quantitatively described the interface and corresponding relevant metrics to understand how the microstructural features at the IPyC/SiC interface may influence actinide and fission product interactions with the SiC layer. Particles were selected with varied 110mAg retention rates, and their volumes were reconstructed and analyzed for distributions of pores, fission product/actinide features, SiC, and IPyC. It was found that porosity accommodates fission products in the interface and SiC layers. The largest fission product/actinide precipitates were found in the interface region. This was also where the largest number fraction of fission products/actinides was found, consistent with SEM showing fission product/actinide pileup along selected areas of the interface region.

Failure mechanisms investigation of ultra-thin composite polymer electrolyte-based solid-state lithium metal batteries

Solid-state lithium metal batteries (SSLBs) using solid polymer electrolytes (SPEs) still suffer from the risk of lithium dendrites, and the filling of porous framework can effectively alleviate the short-circuit problem. However, the interfacial failure mechanism of SPE with lithium metal anode and the action of porous framework filler are not fully understood. Herein, thin polyethylene (PE) separator is used as filler of poly(ethylene oxide) (PEO) to prepare ultra-thin composite polymer electrolyte (PE-CPE). Although the PE framework can greatly extend the cycling life of PE-CPE with lithium metal anode, the focused ion beam-scanning electron microscopy (FIB-SEM) results reveal that the uneven deposition and pulverization of lithium at the Li/PEO interface. Nanoparticulate lithium dendrites grow through the SPE resulting in a short-circuit, while the PE framework with small pores restricts the ingress of lithium nanoparticles through physical barrier. This work provides the growth mode of lithium dendrites in PEO-based SPE systems, and simultaneously demonstrates the role of porous framework to block lithium dendrites in SSLBs.

Nanoscale correlative X-ray spectroscopy and ptychography of carious dental enamel

This study reports the characterisation of human dental enamel caries using synchrotron nanoscale correlative ptychography and spectroscopic mapping in combination with scanning electron microscopy. A lamella ̴2.4 µm thick was extracted from a carious enamel region of a tooth using focused ion beam-scanning electron microscopy and transferred to two synchrotron beamlines to perform hard X-ray nano-fluorescence spectroscopy simultaneously with differential phase contrast mapping at a beam size of 55 × 45 nm. Soft X-ray ptychography data was then reconstructed with a pixel size of 8 nm. The two dimensional variation in chemistry and structure of carious enamel was revealed at the nanoscale, namely, the organisation of hydroxyapatite nano-crystals within enamel rods was imaged together with the inter-rod region. Correlative use of electron and X-ray scanning microscopies for the same sample allowed visualisation of the connection between structure and composition as presented in a compound image where colour indicates the relative calcium concentration in the sample, as indicated by the calcium Kα fluorescence intensity and grey scale shows the nanostructure. This highlights the importance of advanced correlative imaging to investigate the complex structure-composition relationships in nanomaterials of natural or artificial origin.

Combined Focused Ion Beam – Scanning Electron Microscope and Synchrotron X-ray Fluorescence analysis of multi-solid and melt inclusions from the super-giant Grasberg Cu[sbnd]Au deposit, Indonesia

Previous studies of the mineralised quartz veins from the Grasberg CuAu deposit in Indonesia have shown that they contain multi-solid inclusions and silicate melt inclusions. The multi-solid inclusions exhibit salinities up to 75 wt% NaCl equiv. and ultrahigh homogenisation (Vapour + Liquid + Solid → Liquid) temperatures, up to 1281 °C, but the processes leading to their formation are poorly understood. To determine the composition of these inclusions they were analysed by Focused Ion Beam – Scanning Electron Microscope (FIB-SEM) and Synchrotron X-ray Fluorescence (SXRF) techniques. FIB-SEM analysis of two representative multi-solid inclusions (MSI) showed that they contain a large halite and a smaller sylvite crystal and mixed KFe chloride crystals. K-feldspar crystals occurring inside and outside the multi-solid inclusions indicate that they were trapped from a melt phase. The ore-mineral chalcopyrite was also identified in one inclusion. Opening the multi-solid inclusions under vacuum resulted in a coating enriched in Na, K, Fe and Cl that precipitated on the crystals and walls of the inclusions. FIB-SEM analysis of a coexisting silicate melt inclusion showed that it consisted mainly of a devitrified glass with approximately K-feldspar composition that also contained small crystals of iron oxide. Further milling of the melt inclusion exposed a CuFe-rich silicate mineral. SXRF analysis of another multi-solid inclusion indicated that Br and Zn occur in the aqueous phase whereas K, Ca, Fe, Pb and Mn are hosted by solid phases within the inclusion.Modelling of mineralisation processes demonstrate that a supercritical, intermediate density fluid (with ~5 wt% NaCl) underwent an initial pressure drop causing phase separation and the formation of a vapour-rich fluid and a small fraction of brine, which led to the formation of salt hydrates, salt melts or both within the MSI. The coexistence of silicate melt inclusions and the occurrence of hematite and, K-feldspar in MSI suggest that a coeval silicate melt is also associated with mineralisation at the Grasberg deposit. The high salinity, multi-solid inclusions and melt inclusions form early in the vein paragenesis and record the origin and initial processes of ore deposition. Furthermore, the high metal-bearing capacity of salt melts suggests that the observation of coexisting silicate and salt melts may indicate the presence of a fertile mineral system.

Evaluating Electrolyte-Anode Interface Stability in Sodium All-Solid-State Batteries.

All-solid-state batteries have recently gained considerable attention due to their potential improvements in safety, energy density, and cycle-life compared to conventional liquid electrolyte batteries. Sodium all-solid-state batteries also offer the potential to eliminate costly materials containing lithium, nickel, and cobalt, making them ideal for emerging grid energy storage applications. However, significant work is required to understand the persisting limitations and long-term cyclability of Na all-solid-state-based batteries. In this work, we demonstrate the importance of careful solid electrolyte selection for use against an alloy anode in Na all-solid-state batteries. Three emerging solid electrolyte material classes were chosen for this study: the chloride Na2.25Y0.25Zr0.75Cl6, sulfide Na3PS4, and borohydride Na2(B10H10)0.5(B12H12)0.5. Focused ion beam scanning electron microscopy (FIB-SEM) imaging, X-ray photoelectron spectroscopy (XPS), and electrochemical impedance spectroscopy (EIS) were utilized to characterize the evolution of the anode–electrolyte interface upon electrochemical cycling. The obtained results revealed that the interface stability is determined by both the intrinsic electrochemical stability of the solid electrolyte and the passivating properties of the formed interfacial products. With appropriate material selection for stability at the respective anode and cathode interfaces, stable cycling performance can be achieved for Na all-solid-state batteries.

The Combined Action of Organic Inhibitors on Copper and Aluminium Metals and Aluminium Alloy Containing Copper

The approach used in the present work involves investigating the corrosion protection properties of mixed inhibitors for copper and aluminium substrates in chloride-containing solutions, which serve as a benchmark for studies of the alloy AA2024, with Cu and Al being the main culprits for localized corrosion. A synergistic mixture of inhibitors could find potential applications in novel blending combinations, such as in cooling water as an inhibitor in closed systems or incorporated in various protective coatings as additives, nano-containers, etc. If possible, the protective inhibitor film should show irreversibility of inhibition which can be defined as the ability to, once formed, retains its protective properties when the concentration of the corrosion inhibitor decreases. This irreversibility of the protective properties is essential for long-term protection.Inhibitory action of organic molecules, 2-mercaptobenzimidazole (MBI) and octylphosphonic acid (OPA) and their binary combinations on aluminium, copper and aluminium alloy 2024-T3 was investigated in chloride environments by conventional electrochemical methods and surface-analytical techniques [1,2]. In addition, the influence of pre-treatment of the metal surface and the choice of solvent for liquid-phase deposition on adsorption of MBI and OPA was studied on individual metals, Al and Cu [3]. Although OPA is not an inhibitor for Cu, it can synergistically boost corrosion inhibition of copper when added to MBI. In contrast, a synergistic effect between MBI and OPA as corrosion inhibitors was not observed for AA2024-T3. The mechanism was proposed where the thickness and structure of the surface layer are dependent on the pH. For the sample exposed to MBI at pH 5.5, where the Cu2O is stable, a thin Cu(I)MBI film is formed.In contrast, when exposed to the mixture of MBI and OPA at a pH of 4, the amount of produced Cu+ ions is boosted, and a much thicker Cu(I)MBI film forms by dissolution-precipitation mechanism. This layer exhibits high inhibitory effectiveness on copper substrate. At even lower pH, the thick compact Cu(I)MBI film does not form due to intensive dissolution of the Cu2O underlayer, resulting in a voluminous product. The postulated mechanism is confirmed by electrochemical data and composition of the layer by X-ray photoelectron spectroscopy, time-of-flight secondary ion mass spectroscopy and focused-ion beam scanning electron microscopy with chemical analysis.Immersion of AA2024 in an OPA-containing solution caused significant localized corrosion, while no local electrochemical activity on AA2024 was detected in an MBI-containing solution, indicating that the MBI inhibitor was very effective against pitting corrosion. Figure shows FIB/SEM (cross-section) analysis of local corrosion induced by Al2CuMg phase after 24 h immersion of AA2024 in 3 wt.% NaCl containing 1 mM MBI. The chemical analysis employed at the cross-section (yellow rectangles) of the Al2CuMg revealed that the MBI layer reduces the dissolution rate of dealloying of this phase and the rate of oxygen reduction on the copper remnant sites.This study shows that the behaviour of each combination of inhibitor and metal substrate is unique and cannot be translated to the more complex system such as alloy. Therefore, a profound understanding of the inhibition mechanism of individual metals is a prerequisite for further investigation of the corrosion inhibition of aluminium alloys. Acknowledgements: The financial support of the project by the Slovenian Research Agency is acknowledged (grants No. P1-0134, P2-0393 and BI-US/22-24-140) is acknowledged. Barbara Kapun, BSc, is acknowledged for FIB-SEM-EDS analysis.

Fueling the Simulation Machine: Considerations for High-Resolution 3D Microscopy to Support Computational Modeling in Battery Research

To meet the rapidly evolving energy needs of a growing population, energy storage and conversion devices such as batteries must rapidly evolve as well. Battery materials and other functional energy materials derive their properties not from their static state, but from how they interact with other materials in their service environment. Furthermore, the microstructure of these materials strongly dictates their performance and how they interact with other components (like electrolytes, binders, etc). In order to accelerate this development cycle, researchers are increasingly integrating computational modeling into their materials and device development efforts.Computational analysis is progressing to the point where simulations can incorporate real material microstructures, simulate statistically equivalent structures, and predict performance changes based on changes to these microstructures. At the same time experimental techniques have emerged that can deliver representative volumes of high-quality, high-resolution 3D microstructural images from real devices and materials. The interplay between advanced computational analysis and evolving characterization capabilities means we are rapidly approaching the realization of the “materials by design” paradigm where new materials are designed and tested digitally with input and validation provided by advanced materials characterization techniques. Within this paradigm, however, it is critical that the experimental techniques provide accurate, realistic, and representative input to the computational models. In the case of microstructural information, this means generating 3-dimensional images that accurately represents the materials in question.One key example of this is for materials, like battery materials and electrodes, which contain micro- and nano-scale porosity. Acquiring image data that can reproduce real material properties and feed accurate simulations is challenging and relies on satisfying several conditions. For example, the volume must be representative of the “bulk” material microstructure. The (2D) image resolution must capture the relevant scope of material features, and the 3D image must accurately represent the material in all 3 dimensions and at appropriate length scales. The focused-ion beam scanning electron microscope (FIB-SEM) is capable of imaging these micro- and nano-scale pore networks in 3D but care must be taken when considering these experiments, especially when the intent is to use the images to feed computational models.We present here a review of the factors researchers must consider when tackling these demanding tasks and highlight experimental recommendations for leveraging FIB-SEM tomography to produce the most relevant imaging data in this context. We use a lithium-ion battery cathode as a test case to demonstrate this approach, but the outcome and methods can be leveraged across the materials research space and beyond.

Reactive Spray Deposition Technology As an Alternative Method for Precious Metals Deposition on Sintered Titanium Porous Transport Layers for Application in Advanced Proton Exchange Membrane Water Electrolyzers

The metal layer deposition technologies have been revolutionized throughout the years. One of the most common forms of thin metal film deposition techniques is Physical Vapor Deposition (PVD). Within the category of PVD, there are many modifications based on the source of deposition. Among all PVD variations, the Electron Beam Physical Vapor Deposition (EB-PVD) has the advantages of higher deposition rates, the ability to deposit a wide range of high purity metals for high purity films, and the creation of continuous film layers. [1,3]. EB-PVD is better known as a thermal vaporization technique. Thermal Vaporization focuses on a source, in this case an Electron Beam (EB), which bombards the desired source material with electrons. The electron beam increases the temperature of the porous metal source until it reaches its vapor phase. The metal vapor is then condensed onto the surface of the substrate holder perpendicular to the source material. While EB-PVD is known for its advantages of higher material utilization efficiency, higher deposition rates, and better step coverage [1], it lacks in its ability to penetrate into the volume of Porous Transport Layer (PTL) or coat surfaces that are not perpendicular to the source. This is important as the PTL is in contact with a corrosive environment, which causes metal corrosion and degradation of the PTL at the surfaces that are not protected by the coating.A key aspect plaguing the thin film deposition techniques is the ability to penetrate deep into the volume of a PTL and provide full coating of the porous material, including surfaces not perpendicular to the source. In an attempt to find a solution to this challenging task, we explored the capability of the Reactive Spray Deposition Technology (RSDT) to deposit precious metal nanoclusters directly onto all surfaces in the volume of the sintered titanium material [2]. The studied metal coating of interest is Gold (Au). In this work, we have deposited Au coatings of various thicknesses onto the Ti-PTLs by using both EB-PVD and RSDT techniques. The Au thin film deposits are characterized by scanning electron microscopy (SEM), digital optical microscopy, inductively coupled plasma (ICP), and focused ion beam scanning electron microscopy (FIB-SEM) [2]. The optimal deposition parameters for thin and continuous Au films with precisely controlled thicknesses have been identified. In addition, the depth of penetration of the deposits in the volume of the PTL as a function of the deposition parameters have been studied in detail, and the results will be reported at the ECS 242 meeting.

Characterizing the Pore Network of Diffusion Media at the Pore Size Scale

Water management by gas diffusion media and electrodes is a fundamental aspect of the performance of electrochemical cells including proton exchange membrane (PEM) fuel cells. In these devices, product liquid water blocks part of the available space for reactants flow, leading to mass transport losses and lowering of the performance1. Pores saturation has been observed with different experimental techniques for GDL substrates, however a detailed saturation process at the pore size scale of the microporous layer (MPL) is necessary. Previously, it was suggested that large pore network domains are responsible for an enhanced water evacuation2, however, possible existence of narrow size constrictions could still limit water evacuation. In this work, we detail the benefits of three-dimensional imaging of the pore network at the typical MPL pore size scale, i.e. the sub-micrometre scale, which is achieved by focused ion beam scanning electron microscope (FIB-SEM) nanotomography.Two different MPL designs were analysed: an acetylene black based MPL, named Li100, and a vapor grown carbon fiber (VGCF) based MPL, the latter showing better performance under high relative humidity conditions2, 3. FIB-SEM tomography volumes in Fig. 1a-b were used to observe the relative distribution of larger pore domains and narrower pore constrictions. By removing narrower sized pores from the network and analysing the connections of large pore domains, we show the existence of a characteristic size for pore constrictions below which the pore network is well connected. This characteristic size is depicted by the red line in Fig. 1c-d, which plots the fraction of connected pores as a function of their minimum size. Constrictions size values for the two MPL designs were further validated with mercury intrusion experiments, since constrictions affect all the intrusions by capillary pressure, such as water flow in hydrophobic MPLs.The calculated parameters, which are representative of the connections between large pore domains, open up new perspectives on the prediction of gas diffusion under realistic conditions. The approach allows evaluation of the effects of alternatively removing larger and narrower pore domains, to understand the saturation-driven tortuosity in different MPL structures. J. Shen, L. Xu, H. Chang, Z. Tu, and S. H. Chan, Energy Conversion and Management, 207, 112537 (2020).C. Simon, D. Kartouzian, D. Müller, F. Wilhelm, and H. A. Gasteiger, Journal of The Electrochemical Society, 164, F1697–F1711 (2017).C. Simon, J. Endres, B. Nefzger-Loders, F. Wilhelm, and H. A. Gasteiger, Journal of The Electrochemical Society, 166, F1022–F1035 (2019). Figure 1

Elucidating the Sectioning Fragmentation Mechanism in Silica‐Supported Olefin Polymerization Catalysts with Laboratory‐Based X‐Ray and Electron Microscopy

AbstractStrict morphological control over growing polymer particles is an indispensable requirement in many catalytic olefin polymerization processes. In catalysts with mechanically stronger supports, e. g., polymerization‐grade silicas, the emergence of extensive cracks via the sectioning fragmentation mechanism requires severe stress build‐up in the polymerizing catalyst particle. Here, we report on three factors that influence the degree of sectioning in silica‐supported olefin polymerization catalysts. Laboratory‐based X‐ray nano‐computed tomography (nanoCT) and focused ion beam‐scanning electron microscopy (FIB‐SEM) were employed to study catalyst particle morphology and crack propagation in two showcase catalyst systems, i.e., a zirconocene‐based catalyst (i.e., Zr/MAO/SiO2, with Zr=2,2’‐biphenylene‐bis‐2‐indenyl zirconium dichloride and MAO=methylaluminoxane) and a Ziegler‐Natta catalyst (i.e., TiCl4/MgCl2/SiO2), during slurry‐phase ethylene polymerization. The absence of extensive macropores in some of the catalysts’ larger constituent silica granulates, a sufficient accessibility of the catalyst particle interior at reaction onset, and a high initial polymerization rate were found to favor the occurrence of the sectioning pathway at different length scales. While sectioning is beneficial for reducing diffusion limitations, its appearance in mechanically stronger catalyst supports can indicate a suboptimal support structure or unfavourable reaction conditions.

Morphological classification and three-dimensional pore structure reconstruction of shale oil reservoirs: A case from the second member of Paleogene Kongdian Formation in the Cangdong Sag, Bohai Bay Basin, East China

This study combines large volume three-dimensional reconstruction via focused ion beam scanning electron microscopy (FIB-SEM) with conventional scanning electron microscope (SEM) observation, automatic mineral identification and characterization system (AMICS) and large-area splicing of SEM images to characterize and classify the microscopic storage space distribution patterns and 3D pore structures of shales in the second member of the Paleogene Kongdian Formation (Kong 2) in the Cangdong Sag of the Bohai Bay Basin. It is shown that: (1) The Kong 2 Member can be divided into seven types according to the distribution patterns of reservoir spaces: felsic shale with intergranular micron pores, felsic shale with intergranular fissures, felsic shale with intergranular pores, hybrid shale with intergranular pores and fissures, hybrid shale with intergranular pores, clay-bearing dolomitic shale with intergranular pores, and clay-free dolomitic shale with intergranular pores. (2) The reservoir of the intergranular fracture type has better storage capacity than that of intergranular pore type. For reservoirs with storage space of intergranular pore type, the dolomitic shale reservoir has the best storage capacity, the hybrid shale comes second, followed by the felsic shale. (3) The felsic shale with intergranular fissures has the best storage capacity and percolation structure, making it the first target in shale oil exploration. (4) The large volume FIB-SEM 3D reconstruction method is able to characterize a large shale volume while maintaining relatively high spatial resolution, and has been demonstrated an effective method in characterizing the 3D storage space in strongly heterogeneous continental shales.

Quantitative two/three-dimensional spatial characterization and fluid transport prediction of macro/micropores in Gaomiaozi bentonite

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. • The influence of image magnification on the quantitative characterization of the pore structure and the prediction of permeability is discussed. • The influence of different algorithms on the characterization of pore size distribution is discussed. • An improved permeability prediction model that can consider the effect of different pore sizes on seepage characteristics is proposed.

THE ROLE OF CLAY MINERALS IN HYDROCARBON GENERATION, MIGRATION AND ACCUMULATION

This study focuses on the understanding of the role of clay minerals in hydrocarbon generation, migration and accumulation. Clay minerals are involved in the formation of kerogen, catalytic cracking of kerogen into petroleum, migration of crude oil, and the continued change to hydrocarbon composition in petroleum reservoirs. In kerogen formation, clay minerals act as catalysts and sorbents to immobilize organic matter through ligand exchange, hydrophobic interactions and cation bridges by the mechanisms of Maillard reactions, polyphenol theory, selective preservation and adsorptive protection. Clay minerals also serve as catalysts in acid-catalyzed cracking of kerogen into petroleum hydrocarbon through Lewis and Bronsted acid sites on the clay surfaces. The amount and type of clay mineral affect the composition of the petroleum. Bronsted acidity of clay minerals is affected by the presence and state of interlayer water, and displacement of this water is a probable driver in crude oil migration from source rocks. During crude oil migration and accumulation in reservoirs, the composition of petroleum is continually modified by interaction with clay minerals. Clay minerals remain the most difficult of all earth materials to study and characterize. Their sheet structure results in features that can only be resolved at the sub-micron scale. They are also subtly variable in chemical composition (Fe, Mg, K, Al, et cetera) and can be confused with each other and other silicates. The recent innovative analytical tools and modern analysis techniques, example., micro- and nano-X-ray Computed Tomography (XCT), QEMSCAN (Automated Mineralogy and Petrography), FIB/SEM (Focused Ion Beam/Scanning Electron Microscope), EDS (Energy-dispersive X-ray spectroscopy), etc., have the capability of quantitative and qualitative characterizing nano-pore features and mineralogy of fine grained shale rocks, which create new era of studying clay minerals for facilitating unconventional (shale) reservoir exploration. Even though there have been reports about the application of clay minerals in the oil and gas exploration, surprisingly little work has been documented. Keyword: clay mineral, organic matter, generation, vitrinite, kerogen, montmorillonite.