Focused Ion Beam Scanning Electron Microscopy Research Articles

Synergistic Application of Machine Learning to Microstructural Characterization on Electrode Composites of Solid Oxide Fuel Cells

Solid oxide fuel cells (SOFCs) have been recognized as one of the most potent next-generation energy conversion systems, owing to their higher efficiency, better fuel flexibility, and smaller amount of pollution, unlike their counterpart fuel cells. SOFCs can be analyzed as a highly-complex multi-component materials system consisting of porous electrodes (cathodes and anodes), densified electrolytes, interconnects, and sealing materials, which are sequentially layered and characteristic of heterogeneous and multi-phase materials. The resultant power generation is achieved through the electrochemical reactions involving electronic carriers, ionic carries, and gaseous transports at anodes and cathodes, influencing their electrical, mechanical, and thermal properties. In particular, both cathodes and anodes are typically constructed based on three components: mixed ionic/electronic electrodes, electrolytes, and a porous section. Those three constituents should be optimized at both electrodes with the aim of maximizing the electrochemical reaction sites, i.e., triple-phase boundaries in association with the gaseous transport involved in oxygen reduction reactions at cathodes and hydrogen oxidation reactions at anodes, which leads to high cell performance and guaranteed durability. The electrochemical performances are crucially dependent on their complex microstructures, demanding for highly informative analyses on the electron microscopy images under investigation.This work reports quantitative microstructural analysis methodology incorporating machine learning-assisted microstructural analysis strategy. Quantitative microstructural interpretations were carried out without human involvement through an integrated combination of deep learning and focused ion beam-scanning electron microscopy (FIB-SEM) analytics on Ni/Y2O3-stabilized ZrO2 (Ni/YSZ) cermets. The Ni/YSZ/pore composites were analyzed for the automated extraction of microstructural parameters with the aim to preventing the subjective analysis problems and unavoidable artifacts frequently encountered in lengthy image processing tasks and eliminate biased evaluations. Considering the high volume of image data and future expectations for electron microscopy usage, FIB-SEM was efficiently combined with semantic segmentation targeted at detailed phase recognition on three constituents, i.e, Ni, YSZ, and pores. Traditional image processing analysis tools are in the synergistic manner combined with phase separation predictions by semantic segmentation algorithms, allowing for a quantitative evaluation of microstructural parameters. The combined strategy enables one to significantly enhance poor image quality originating from artifacts in electron microscopy, including charging effects, curtain effects, out-of-focus problems, and unclear phase boundaries encountered in searching for high-efficiency solid oxide fuel cells (SOFCs).

Microstructural Analysis of Solid Oxide Electrochemical Cells via 3D Reconstruction Using a FIB-SEM Dual Beam System

The 3D reconstruction based on tomography technology enables quantitative and qualitative microstructural analysis of complex multiphase oxide structures. This powerful approach is widely investigated in diverse areas, in particular, gaining more importance in solid oxide electrochemical cells (SOCs) fields. SOCs are promising energy conversion devices with high efficiency, however, they have complex and porous/dense multilayered microstructures, which are closely related to the electrochemical reaction in the electrodes, thus, one of the major factors determining overall output performance of SOCs. Therefore, it is necessary to quantify the microstructural parameters of the cell. A focused ion beam-scanning electron microscope (FIB-SEM) dual beam system is one well-established method to obtain tomographic images to reconstruct 3D microstructures. It has an appropriate scale of tenth of nm to μm-level with high spatial resolution to represent the microstructural characteristics of the SOC electrodes. This presentation is intended to introduce our progress on 3D reconstruction techniques to quantitatively analyse SOCs, obtaining microstructural features such as particle size, connectivity, tortuosity, contact area, and triple phase boundary density. These in-depth analyses are helpful in extensively understanding electrochemical behavior in SOC electrodes.

(Digital Presentation) Phase-Field Modeling of the Reduction Process in Solid Oxide Fuel Cell Anode

It is well-known that the reduction process of nickel oxide-yttria-stabilized zirconia (NiO-YSZ) composite anode influences the initial performances and durability of solid oxide fuel cell. In this work, phase field method is used to simulate the reduction process of nickel oxide (NiO) in anode-supporting solid oxide fuel cell (SOFC), which captures the competition effects among diffusion, crystal phase transition of NiO to Ni, and sintering. A real three-dimensional microstructure of NiO-YSZ composite anode reconstructed using focused ion beam-scanning electron microscopy (FIB-SEM) technique is used to initialize the simulation. The simulation results are qualitatively compared to experimental results under different reduction conditions. The results reveal that the stress distribution in SOFC anode can be largely influenced by the interactions between the residual stress in yttria-stabilized zirconia (YSZ) and the reduction process. The results explain the phenomena of mechanical damage formed in SOFC single cell during reduction. Figure 1

Chemical and Mechanical Degradation of the Interface between Li7La3Zr2O12 Electrolyte and LiNi0.6Mn0.2Co0.2O2 Cathode as a Result of Electrochemistry

All solid-state Li-ion cells promises high energy density and high safety standards over conventional Li-ion cells based on liquid electrolytes. The first principle calculations shows that the most of the potential candidates for solid electrolytes for Li-ion cells have small electrochemical stability window. The limited electrochemical stability window leads to electrochemical reactivity with the cathode when cycled beyond the voltage limit. The reactions products are often leads to increased overpotential, hence rapid capacity fade during continuous cell operation. In addition to the electrochemical reactions, mechanical incompatibility further makes the cathode-solid-electrolyte interfaces prone to cracking, as cathodes undergoes structural changes during lithiation/delithiation. Indeed many experimental works have also showed limited cyclability of all-solid-state Li-ion cells owing to interfacial side reactions and mechanical cracking. Therefore, electrochemistry induced mechanical failure and electrochemical side reactions at the interface remains the bottleneck for the development of all-soli-state Li-ion cells. This paramount challenge invites us to systematically investigate the aforementioned problem by probing non-destructively near the cathode-solid-electrolyte interface. We introduce a model system that utilizes very thin layer of LiNi0.6Mn0.2Co0.2O2 (NMC622) cathode (60-600 nm) on top of bulk Al-doped-Li7La3Zr2O12 (Al-LLZO) solid-electrolyte pellet. This unique system allows us to non-destructively probe the electrochemical reaction by combined in-operando and ex-situ X-ray absorption spectroscopy (XAS), with probing depth beyond the cathode-solid-electrolyte interfaces.In this work, we elucidate the mechanism of electrochemical failure of NMC622 cathode and Al-LLZO solid-electrolyte interface at different temperature, through combined ex-situ and in-operando characterization techniques. The study revealed that the electrochemical reactivity is dependent on cell operation temperature. For the ex-situ samples that was cycled at higher temperature (80 ⁰C), the reduction of transition metals in cathode, i.e., nickel and cobalt was evident by soft X-ray absorption spectroscopy (XAS) of their respective L-edges. The results match closely with DFT prediction for the interfaces at high voltage. On the other hand, the in-operando XAS experiment, where characterization was done at room temperature, the reduction of transition metals in cathode, and hence electrochemical reactivity, was not observed. These results remarkably outline that electrochemical reactivity of solid-electrolyte and cathode interfaces at high voltage is kinetically inhibited at low or near room temperature, and hence very sensitive to cell operating condition. Nonetheless, it was found that irrespective of operating conditions i.e., temperature, the cell capacity rapidly decays as number of cycles continue. The focused ion beam scanning electron microscopy (FIB-SEM) revealed that this can be mostly attributed to intergranular cracks in NMC622 cathode films as well as to delamination of the cathode-solid-electrolyte interfaces during cell operation. As these cracks, in cathode films and at the interfaces, grows, the overpotential/impedance increases due to limited contacts for effective Li+ migration.The current work contributes to the field by showcasing interfacial degradation pathways in cell operation by novel design of experiments that allows for both in-operando and non-destructive characterization. The findings of this work will guide towards engineering cells of practical use. Figure 1

Advanced Nanoscale Characterizations of Solid Oxide Cell Electrodes

The growing interest in the transition towards a fossil-free energy system has accelerated research and development on hydrogen-based energy conversion technologies. In this context, solid oxide cells (SOCs) have attracted attention as they can be operated in both electrolysis (SOEC) and fuel cell (SOFC) modes providing a clean and sustainable way of producing both green hydrogen and electricity at high efficiency. Despite their great potential, the current SOC technology faces some challenges due to the significant cell degradation upon operation. The performance loss has been attributed to several factors, such as microstructural evolution in the electrodes [1], and inter-diffusion of elements between the cell layers associated to material decomposition and reactivity [2–4]. Despite several efforts, all these degradation phenomena are still not precisely understood as they involve complex and intricate processes arising at different length scales. To address this issue, durability tests have been performed in representative operating conditions at high current density and humidity at the air side for both SOFC and SOEC modes. In addition, the tested cells were analyzed with advanced characterization techniques to study the material degradation down to the nanometer and the atomic scales.In this work, standard fuel electrode supported cells have been studied. They are composed of a La0.6Sr0.4Co0.2Fe0.8O3-δ (LSCF) current collecting layer (CCL) and a LSCF/Ce0.8Gd0.2O2-δ (LSCF/GDC) composite functional layer (FL) for the air electrode, GDC for the barrier layer, (Y2O3)0.08(ZrO2)0.92 (YSZ) for the electrolyte and Ni-YSZ for the fuel electrode. The samples were aged for 2000 h in various operating conditions: temperature (750, 800, 850 °C), humidity in the air flow (0%, 3% and 8%) and operating mode (SOEC and SOFC at ±1 A cm-2). The electrochemical behaviour of the cells has been characterized using electrochemical impedance spectroscopy (EIS) and polarization curves. The advanced post-mortem characterizations include techniques such as synchrotron X-ray nano-diffraction and nano-fluorescence (nano-XRD and nano-XRF) spectroscopy performed at the European Synchrotron Radiation Facility (ESRF, ID16B), scanning transmission electron microscopy (STEM) coupled with energy dispersive X-ray spectroscopy (EDX), and atom probe tomography (APT). A larger range of information was acquired by using complementary techniques, including focused ion beam scanning electron microscopy (FIB-SEM), X-ray photoelectron spectroscopy (XPS), and high-resolution secondary ion mass spectroscopy (SIMS) imaging.The electrochemical characterizations (Fig. 1a) have shown that the degradation was aggravated by increasing the operating temperature, the presence of humidity at the air side and the operation in electrolysis mode. The impedance spectra have been interpreted using a physically-based multiscale model [5]. The analysis has revealed that the performance loss was mainly due to the fuel electrode degradation, while the air electrode degradation remained limited, except when operated under humid conditions in the SOEC mode. The post-mortem characterizations have shown that such degradation in the SOEC mode was mainly related to a strong Ni depletion, which became more pronounced with increasing operating temperature. For the cell operated under humid air in the SOEC mode, a significant amount of SrCO3 phase was observed on top of the air electrode. On the contrary, the cell operated under humid air in the SOFC mode did not show such phase formation. Advanced characterization techniques (nano-XRD, nano-XRF, STEM-EDX, and APT) put in evidence an intermixing of elements in the air electrode (LSCF/GDC) at the atomic scale (Fig. 1b). Moreover, the presence of an inter-diffusion layer (IDL) between GDC and YSZ phases was observed (Fig. 1c) for all samples, including the freshly prepared sample. Nevertheless, neither the mixing of elements in the air electrode nor the presence of the IDL seem to have a major influence on the cell degradation. It can be speculated that these phenomena make the air electrode more stable against phase decomposition by inhibiting the formation of commonly observed insulating phases such as SrZrO3 and SrO.

Validation of and Simulations using a High-Temperature Electrolysis Model

Efforts for increasing the share of renewable power generation are dramatically boosted since electrical power from fossil fuels has been used as weapon [1]. Therefore, efficient conversion systems are of great importance to conserve most of the delivered power by nature. High-temperature electrolysis is such an efficient type of energy conversion system compared to similar technologies [2-4]. To bridge the gap to an industrial scale application, the electrochemical and chemical processes have to be understood in detail which is enlightened by some publications from our group [5-8]. In this contribution, a multiphysics model for three types of electrolysis processes (steam, CO2 and co-electrolysis) is presented and evaluated. Relevant parameters like the exchange current density or the anodic / cathodic transfer coefficient including parameter variations for the inlet gas stream, flow rate of the gas, temperature and applied current are investigated. For the microscale properties in the functional layer, Focused Ion Beam Scanning Electron Microscopy (FIB-SEM) is used with the “Slice and View” technique [9,10]. Extracting information like the Triple Phase Boundary Length (TPBL), the fraction of electronic and ionic phase in mixed ionic-electronic conducting (MIEC) materials or the porosity and tortuosity of the (La,Sr)CoO3-δ (LSC) air electrode and the Ni / 8 mol% yttria stabilized zirconia (Ni-8YSZ) fuel electrode help in enhancing the modeling quality of high-temperature SOC model. A conversion from the TPBL (s. Figure 1) to an active area to volume ratio for the computation is needed.Calculated iV-characteristics and experimental curves are compared and serve as a validation for (I,V) data points at higher currents. Depending on the degree of agreement, the (missing) main contributions to loss mechanisms can be identified and initiate a feedback loop for material optimization. Sensitivity analyses are carried out for parameters that are difficult to vary in experiments (e.g. porosity). Porosity and tortuosity parametrize the porous structure for a homogeneously distributed property assumption across the material layers. The ratio between electronic and ionic phase fine-tunes the positioning of iV-characteristics within the potential regime of Ohmic and polarization losses. Calculated electrochemical impedance spectra (EIS) enhance the insight into the theoretical system and may be compared to experimental spectroscopy data via Equivalent Circuit Models (ECM). Calculated data from the model are acquired as in the used experimental setup. As an example, calculated EIS data from steam electrolysis show good agreement with a R-(RQ)4 ECM which as well describes most of the corresponding experimental data in our group. Effects of degradation are envisioned to be incorporated into the model as well.[1] Hosp, G.; Höltschi, R.; Keusch, N.; Schürpf, T.: https://www.nzz.ch/wirtschaft/rohstoffe-als-waffen-die-neusten-entwicklungen-ld.1681268 (28th October 2022, 2.13 pm)[2] Foit, S.R.; Dittrich, L.; Duyster, T.; Vinke, I.; Eichel, R.-A.; de Haart, L.G.J. (2020): Direct Solid Oxide Electrolysis of Carbon Dioxide: Analysis of Performance and Processes. In: Processes 8 (11), 1390[3] Foit, S.R.; Vinke, I.C.; de Haart, L.G.J.; Eichel, R.-A. (2017): Power-to-Syngas: An Enabling Technology for the Transition of the Energy System? In: Angew. Chem. Int. Edit. 56 (20), 5402–5411[4] Tanaka, Y.; Hoerlein, M.P.; Schiller, G. (2016): Numerical simulation of steam electrolysis with a solid oxide cell for proper evaluation of cell performances. In: Int. J. Hydrogen Energ. 41, 752–763[5] Wolf, S.E.; Dittrich, L.; Nohl, M.; Duyster, T.; Vinke, I.C.; Eichel, R.-A.; de Haart, L.G.J. (2022): Boundary Investigation of High-Temperature Co-Electrolysis Towards Direct CO2 Electrolysis. In: J. Electrochem. Soc. 169, 034531[6] Unachukwu, I.D.; Vibhu, V.; Vinke, I.C.; Eichel, R.-A.; de Haart, L.G.J. (2022): Sr Substituted La2-xSrxNi0.8Co0.2O4+ d (0 ≤ x ≤ 0.8): Impact on Oxygen Stoichiometry and Electrochemical Properties.In: Energies 15, 2136[7] Mebrahtu, C.+; Nohl, M.+; Dittrich, L.; Foit, S.R.; de Haart, L.G.J.; Eichel, R.-A.; Palkovits, R. (2021): Integrated Co-Electrolysis and Syngas Methanation for the Direct Production of Synthetic Natural Gas from CO2 and H2O. In: ChemSusChem 14, 2295 – 2302[8] Dittrich, L.; Nohl, M.; Jaekel, E.E.; Foit, S.R.; de Haart, L.G.J. (Bert), Eichel, R.-A. (2019): High-Temperature Co-Electrolysis: A Versatile Method to Sustainably Produce Tailored Syngas Compositions. In: J. Electrochem. Soc. 166 (13), F971 – F975[9] Wilson, J.R.; Kobsiriphat, W.; Mendoza, R.; Chen, H.; Hiller, J.M.; Miller, D.J.; Thornton, K.; Voorhees, P.W.; Adler, S.B.; Barnett, S.A. (2006): Three-dimensional reconstruction of a solid-oxide fuel-cell anode. In: Nat. Mater. 5, 541–544[10] Gostovic, D.; Smith, J.R.; Kundinger, D.P.; Jones, K.S.; Wachsman, E.D. (2007): Three-Dimensional Reconstruction of Porous LSCF Cathodes. In: Electrochem. Solid St. 10 (12), B214–B217Figure 1: Histogram of the TPBL from a 400 image sample set of a FIB-SEM cut of a Ni-8YSZ electrode. Figure 1

Interfacial Dynamics of Carbon Interlayers at Anode-Free Solid Electrolyte/Lithium Interfaces

Solid electrolytes (SEs) that incorporate lithium (Li) metal anodes provide a promising pathway to improve battery energy density and safety. However, Li metal anodes still suffer from multiple challenges, including 1) uniform Li deposition and dissolution, 2) continual formation of a solid-electrolyte interphase (SEI), and 3) limited rate capability. To control the interfaces, predefined interlayers such as gold, ZnO, carbon, and other coatings have been used tune the Li metal and SE interface. However, there is a need for improved fundamental understanding of the mechanistic role of these interlayers on performance and stability. In this work, we explore the application of an amorphous carbon interlayer in an argyrodite SE system, which is used for in situ Li metal formation in an “anode-free” configuration.The incorporation of a carbon interlayer has been previously shown to act as a physical barrier between the SE and in situ formed Li metal, improve the uniform contact and current distribution across the SE/anode interface, and potentially suppress dendrite propagation [1]. However, the mechanism of this improved performance is not fully understood. Therefore, to study the influence of the carbon interlayer on interfacial performance, a detailed electrochemical analysis was performed.First, the transition in reaction pathway from carbon lithiation to Li nucleation and growth was observed to change as a function of charging rates. To probe the lithiation effects of the carbon interlayer on subsequent Li deposition, incremental electrochemical impedance spectroscopy (EIS) and current-interrupt analysis was performed to study the dynamic changes of the carbon interlayer during the charging process prior to Li nucleation. To confirm the mode of metallic Li nucleation and growth, operando video microscopy and post-mortem focused ion-beam/scanning electron microscopy (FIB-SEM) was utilized. The preferential location of Li deposition and growth at the current collector and carbon interface confirms the transport of Li-ion through the lithiated carbon interlayer. Moreover, the Li metal deposition behavior was observed to depend on the electrochemical properties of the carbon interlayer during the lithiation process. These fundamental electrochemical studies will further our understanding of the design requirements for interlayers that can enable Li metal anodes in solid-state battery systems.[1] Y.G. Lee, S. Fujiki, C. Jung, N. Suzuki, N. Yashiro, R. Omoda, D. S. Ko, T. Shiratsuchi, T. Sugimoto, S. Ryu, J. H. Ku, T. Watanabe, Y. Park, Y. Aihara, D. Im, I. T. Han, Nat. Ener. 5, 299-308 (2020)

High performance composite Pr4Ni3O—Ce0.75Gd0.1Pr0.15O solid oxide cell air electrode

A composite electrode composed of Pr4Ni3O—Ce0.75Gd0.1Pr0.15O (50 wt.%–50 wt.%) was thoroughly investigated in terms of the electrochemical performance as a function of microstructure. The electrochemical performance was characterized by electrochemical impedance spectroscopy and the microstructures, characterized by focused ion beam-scanning electron microscopy and 3D reconstructions, were modified by changing the particle size of Pr4Ni3O and the electrode thickness. The distribution of relaxation time method was applied to help resolve electrochemical processes occurring in the electrodes. It was found that an appropriate increase in electrode thickness and an appropriate decrease in particle size enhanced the oxygen reduction reaction (ORR) kinetics. The lowest area specific resistance obtained in this study at 670 ∘C under pO 2 of 0.21 atm was 0.055 Ω cm2. Finally, a comparison to the Adler-Lane-Steele (ALS) model was made and the main active site for the ORR was concluded to be triple phase boundaries. A fuel cell made of the composite material as the cathode was fabricated and tested. The peak power density was 1 W cm−2 at 800 ∘C, which demonstrates that this composite material is promising for solid oxide fuel cell cathodes.

Characterization of the pore structure in Chinese anthracite coal using FIB-SEM tomography and deep learning-based segmentation

Coalbed methane (CBM) is an unconventional natural gas that possesses significant impacts on energy supply, mining safety, and environmental conservation. CBM is primarily stored within the pores of coal, highlighting the significance of pore structures for both methane storage and migration. However, comprehensively understanding the intricate pore structures in coal pose challenges. This study employed focused ion beam-scanning electron microscopy (FIB-SEM) tomography and deep learning-based segmentation to characterize the pore structures within a Chinese anthracite sample. The obtained pore structures exhibited a considerable degree of disconnection, comprising numerous separate pore components. Isolated pores prevailed in number, while connected pores dominated in surface area and pore volume. Mesopores (100–1000 nm) contributed the most to pore number, surface area, and pore volume. Pore size distribution analysis revealed distinct patterns among different pore structure properties, with pore number exhibiting an intensive distribution while surface area and pore volume displaying dispersed distributions. Pore structure connectivities exhibited a hierarchical nature and held distinct meanings at the levels of pore, pore component, and pore network. The pore structure characteristics observed in this study have implications for primary CBM recovery, emphasizing the necessity to improve connectivity between pore components and fractures to enhance production rates and recoverability.

Three-Dimensional Reconstruction of Nb3Sn Films by Focused Ion Beam Cross Sectional Microscopy

Niobium has been the material of choice for SRF cavities for several decades due to its formability and superconducting properties. The accelerating gradient of niobium cavities is, however, rapidly approaching a theoretical limit. To achieve higher accelerating gradients a new material is needed that can sustain high fields. Nb <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> Sn is a promising competitor with a higher superconducting transition temperature and a higher critical field than pure niobium. However, Nb <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> Sn is very brittle and cannot be formed readily into a cavity. The main method for creating Nb <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> Sn cavities is to form a Nb <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> Sn film into a niobium surface using a tin vapor-diffusion method. This technique creates a microcrystalline Nb <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> Sn thin film on the inner surface of the cavity. Tin depleted regions are known to form in the film during this process. Previous studies have analyzed these regions using transmission electron microscopy on cross-sectional lamellae prepared by focused ion beam/scanning electron microscope (FIB/SEM). This method does not provide any three-dimensional (3-D) information about the distribution of tin-deficient regions. In this study we employ a focused ion beam tomographic technique to analyze the 3-D structure of the film. Electron dispersive X-ray spectroscopy is used to image the tin concentration of the film in 3-D. Tin-deficient regions are discovered close to the surface of the Nb <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> Sn film.

Assessing the Quality of Oxygen Plasma Focused Ion Beam (O-PFIB) Etching on Polypropylene Surfaces Using Secondary Electron Hyperspectral Imaging.

The development of Focused Ion Beam-Scanning Electron Microscopy (FIB-SEM) systems has provided significant advances in the processing and characterization of polymers. A fundamental understanding of ion-sample interactions is still missing despite FIB-SEM being routinely applied in microstructural analyses of polymers. This study applies Secondary Electron Hyperspectral Imaging to reveal oxygen and xenon plasma FIB interactions on the surface of a polymer (in this instance, polypropylene). Secondary Electron Hyperspectral Imaging (SEHI) is a technique housed within the SEM chamber that exhibits multiscale surface sensitivity with a high spatial resolution and the ability to identify carbon bonding present using low beam energies without requiring an Ultra High Vacuum (UHV). SEHI is made possible through the use of through-the-lens detectors (TLDs) to provide a low-pass SE collection of low primary electron beam energies and currents. SE images acquired over the same region of interest from different energy ranges are plotted to produce an SE spectrum. The data provided in this study provide evidence of SEHI's ability to be a valuable tool in the characterization of polymer surfaces post-PFIB etching, allowing for insights into both tailoring polymer processing FIB parameters and SEHI's ability to be used to monitor serial FIB polymer surfaces in situ.

Effect of cell pressure on the electrochemical performance of all‐solid‐state lithium batteries with zero‐excess Li metal anode

AbstractAll‐solid‐state cells (ASSCs) typically operate at a specific pressure to ensure good contact between the solid electrolyte and the electrode‐active materials. However, establishing the ideal cell pressure is challenging because of the various cell structures, the mechanical characteristics of solid electrolytes, and the extent to which the volume of the electrodes changes during cycling. In this study, we propose a specially designed cell assembly that adjusts to the changes in volume that occur during cycling while maintaining a constant cell pressure. The evaluations indicate that the spring in the cell assembly effectively reduces the stress incurred from the volume expansion that occurs in the electrode during charging (lithiation) and the volume contraction that occurs during discharging (delithiation) while maintaining the prescribed cell pressure. The capacity fading—as a function of the cycle number—decreases when operating ASSCs comprising a cell assembly that include a spring, compared with those that exclude a spring. Focused ion beam–scanning electron microscope reveals no cracks and delamination in the LiNi0.8Co0.1Mn0.1O3 (NCM811) composite cathode of the ASSCs, operated at 25 MPa, with a spring‐equipped assembly. The Ag nanolayer that deposits on the Cu foil is an effective collector metal, forming a dense lithium plating layer on the Ag/Cu foil anode.

Characterization of Flow Parameters in Shale Nano-Porous Media Using Pore Network Model: A Field Example from Shale Oil Reservoir in Songliao Basin, China

The pore-throat radius of the shale oil reservoir is extremely small, and it is difficult to accurately obtain the absolute permeability and oil–water two-phase relative permeability of the actual oil reservoir through conventional core experiments. However, these parameters are very important for reservoir numerical simulation. In this paper, a method for characterizing flow parameters based on a pore network model that considers differential pressure flow and diffusion flow is proposed. Firstly, a digital core was reconstructed using focused ion beam scanning electron microscopy (FIB-SEM) from the Gulong shale reservoir in the Songliao Basin, China, and a pore network model was extracted. Secondly, quasi-static single-phase flow and two-phase flow equations considering diffusion were established in the pore network model. Finally, pore-throat parameters, absolute permeability, and oil–water two-phase permeability curves were calculated, respectively. The results show that the pore-throat distribution of the Gulong shale reservoir is mainly concentrated in the nanometer scale; the mean pore radius is 87 nm, the mean throat radius is 41 nm, and the mean coordination number is 3.97. The calculated permeability considering diffusion is 0.000124 mD, which is approximately twice the permeability calculated without considering diffusion. The irreducible water saturation of the Gulong shale reservoir is approximately 0.4, and the residual oil saturation is approximately 0.35. The method proposed in this paper can provide an important approach for characterizing the flow parameters of similar shale oil reservoirs.

Three-dimensional images reveal the impact of the endosymbiont Midichloria mitochondrii on the host mitochondria

The hard tick, Ixodes ricinus, a main Lyme disease vector, harbors an intracellular bacterial endosymbiont. Midichloria mitochondrii is maternally inherited and resides in the mitochondria of I. ricinus oocytes, but the consequences of this endosymbiosis are not well understood. Here, we provide 3D images of wild-type and aposymbiotic I. ricinus oocytes generated with focused ion beam-scanning electron microscopy. Quantitative image analyses of endosymbionts and oocyte mitochondria at different maturation stages show that the populations of both mitochondrion-associated bacteria and bacterium-hosting mitochondria increase upon vitellogenisation, and that mitochondria can host multiple bacteria in later stages. Three-dimensional reconstructions show symbiosis-dependent morphologies of mitochondria and demonstrate complete M. mitochondrii inclusion inside a mitochondrion. Cytoplasmic endosymbiont located close to mitochondria are not oriented towards the mitochondria, suggesting that bacterial recolonization is unlikely. We further demonstrate individual globular-shaped mitochondria in the wild type oocytes, while aposymbiotic oocytes only contain a mitochondrial network. In summary, our study suggests that M. mitochondrii modulates mitochondrial fragmentation in oogenesis possibly affecting organelle function and ensuring its presence over generations.

Three dimensional structures of the inner and outer pig petrous bone using FIB-SEM: Implications for development and ancient DNA preservation

We report on the 3D ultrastructure of the mineralized petrous bone of mature pig using focused ion beam – scanning electron microscopy (FIB-SEM). We divide the petrous bone into two zones based on the degree of mineralization; one zone close to the otic chamber has higher mineral density than the second zone further away from the otic chamber. The hypermineralization of the petrous bone results in the collagen D-banding being poorly revealed in the lower mineral density zone (LMD), and absent in the high mineral density zone (HMD). We therefore could not use D-banding to decipher the 3D structure of the collagen assembly. Instead we exploited the anisotropy option in the Dragonfly image processing software to visualize the less mineralized collagen fibrils and/or nanopores that surround the more mineralized zones known as tesselles. This approach therefore indirectly tracks the orientations of the collagen fibrils in the matrix itself. We show that the HMD bone has a structure similar to that of woven bone, and the LMD is composed of lamellar bone with a plywood-like structural motif. This agrees with the fact that the bone close to the otic chamber is fetal bone and is not remodeled. The lamellar structure of the bone further away from the otic chamber is consistent with modeling/remodeling. The absence of the less mineralized collagen fibrils and nanopores resulting from the confluence of the mineral tesselles may contribute to shielding DNA during diagenesis. We show that anisotropy evaluation of the less mineralized collagen fibrils could be a useful tool to analyze bone ultrastructures and in particular the directionality of collagen fibril bundles that make up the bone matrix.

Interactive Machine Learning Improves Accuracy of Coal Porosity Segmentation in Focused Ion Beam–Scanning Electron Microscopy Images

Interactive Machine Learning Improves Accuracy of Coal Porosity Segmentation in Focused Ion Beam–Scanning Electron Microscopy Images

3D-reconstructions of zygospores in Zygnema vaginatum (Charophyta) reveal details of cell wall formation, suggesting adaptations to extreme habitats.

The streptophyte green algal class Zygnematophyceae is the immediate sister lineage to land plants. Their special form of sexual reproduction via conjugation might have played a key role during terrestrialization. Thus, studying Zygnematophyceae and conjugation is crucial for understanding the conquest of land. Moreover, sexual reproduction features are important for species determination. We present a phylogenetic analysis of a field-sampled Zygnema strain and analyze its conjugation process and zygospore morphology, both at the micro- and nanoscale, including 3D-reconstructions of the zygospore architecture. Vegetative filament size (26.18 ± 1.07 μm) and reproductive features allowed morphological determination of Zygnema vaginatum, which was combined with molecular analyses based on rbcL sequencing. Transmission electron microscopy (TEM) depicted a thin cell wall in young zygospores, while mature cells exhibited a tripartite wall, including a massive and sculptured mesospore. During development, cytological reorganizations were visualized by focused ion beam scanning electron microscopy (FIB-SEM). Pyrenoids were reorganized, and the gyroid cubic central thylakoid membranes, as well as the surrounding starch granules, degraded (starch granule volume: 3.58 ± 2.35 μm3 in young cells; 0.68 ± 0.74 μm3 at an intermediate stage of zygospore maturation). Additionally, lipid droplets (LDs) changed drastically in shape and abundance during zygospore maturation (LD/cell volume: 11.77% in young cells; 8.79% in intermediate cells, 19.45% in old cells). In summary, we provide the first TEM images and 3D-reconstructions of Zygnema zygospores, giving insights into the physiological processes involved in their maturation. These observations help to understand mechanisms that facilitated the transition from water to land in Zygnematophyceae.

Cobalt chromium alloys in fixed prosthodontics: Investigations of mechanical properties and microstructure

Statement of problemCobalt chromium (Co-Cr) alloys possess beneficial mechanical properties because alloys, even in thin sections, can resist high mastication forces and exhibit an acceptable bond to the surface porcelain layer. Traditional manufacturing techniques of Co-Cr alloys such as casting have been replaced with newer fabrication techniques, such as milling, laser melting, and presintered milling. Despite scarce documentation, these new manufacturing techniques are being used to fabricate dental and implant constructions. PurposeThis in vitro study investigates the hardness, yield strength, elastic modulus, and microstructure of the most commonly used Co-Cr alloys for fixed prosthodontics based on manufacturing technique. In addition, this study investigates the effect of heat treatment on the mechanical properties and microstructure of these materials. Material and methodsFive Co-Cr alloys were included (dumbbell and rectangular shaped) based on four manufacturing techniques: cast, milled, laser melted, and presintered milled. Commercially pure titanium grade 4 and titanium-6 aluminum-4 vanadium ELI (extra low interstitial) were included for comparison, and yield strength and elongation after fracture were evaluated. The specimens were tested for hardness using the Vickers test and for elastic modulus using a nondestructive impulse excitation technique. The microstructure of selected specimens was analyzed using focused ion beam-scanning electron microscopy (FIB-SEM) and energy dispersive X-ray spectroscopy (EDS). ResultsThe mechanical properties depend on the manufacturing technique used; the laser-melted and presintered Co-Cr specimens demonstrated the highest mechanical properties, followed by the milled and cast groups. Both the laser-melted and the presintered milled Co-Cr specimens showed smaller grain size compared with the cast and milled Co-Cr specimens. The titanium-6 aluminum-4 vanadium ELI demonstrated higher hardness and yield strength compared to commercially pure titanium grade 4. No major differences were observed for the selected materials regarding the mechanical properties and microstructural appearance after heat treatment. ConclusionsThe laser melting and presintered milling techniques produced higher mechanical properties compared with the cast and milled Co-Cr. These findings were confirmed through microstructural analysis with respect to the grain size, precipitation, and number of pores.

Three-Dimensional Ultrastructural Analysis of the Head-Most Mitochondrial Roots of Mice Spermatozoa Using Focused Ion Beam/Scanning Electron Microscopy (FIB/SEM) Tomography.

This study aimed to clarify the three-dimensional ultrastructure of head-side mice spermatozoa mitochondria. Six 13-week-old male C57BL/6 mice were deeply anesthetized, perfused with 2% paraformaldehyde, and placed in 2.5% glutaraldehyde in 0.1 M cacodylate buffer (pH 7.3) for electron microscopy. After perfusion, the vas deferens was removed, and the specimens were cut into small cubes and subjected to postfixation and en bloc staining. Three-dimensional ultrastructural analysis was performed on five mitochondria on the spermatozoa head using conventional transmission electron microscopy (TEM) and focused ion beam/scanning electron microscopy (FIB/SEM) tomography. Conventional TEM analysis showed that head-side mitochondria were not spiral in morphology but clearly horizontal to the sperm axis. However, this was difficult to evaluate further using conventional TEM. In the FIB/SEM analysis, the first and second head-most mitochondria were flat and straight, with no helix, and shaped as an attachment plug with two electrodes, and their tail side contacted the third mitochondrion. The third mitochondrion was shorter than the fourth and fifth and had a semicircular arching structure. The fourth and fifth mitochondria were spiral-shaped and intertwined. The redundant nuclear envelope encircled the head-most mitochondria. This ultrastructural analysis clarified that the head-most mitochondria have a unique morphology.

Kinetic Monte Carlo (KMC) simulation of sintering of nickel oxide-yttria stabilized zirconia composites: Model, parameter calibration and validation

This study proposes a kinetic Monte Carlo (KMC) model for the sintering of two-phase composites using nickel oxide-yttria stabilized zirconia (NiO-YSZ) as a case study. An artificial neural network (ANN) assisted method is used to calibrate the KMC model parameters by comparing the simulated microstructures and the real microstructure reconstructed by focused ion beam scanning electron microscopy (FIB-SEM). It is demonstrated that the ANN calibrated KMC model can predict quantitatively the microstructure evolution of NiO-YSZ composite. The microstructural parameters such as volume fraction, specific surface area, and triple-phase boundary length density of sintered NiO-YSZ are well predicted within acceptable errors. The proposed framework can be adapted for the simulation of the microstructure evolution of any other composite electrodes for solid oxide fuel cells and other composites fabricated by sintering.