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The porous-cracked microstructure of plasma sprayed ceramics coatings directly influences their macroscopic mechanical response. A 3D micromechanical model based on the discrete element method (DEM) is developed to reproduce their behavior. 3D observations are conducted with FIB-SEM nano-tomography and image analysis is used to extract and discretize the microstructure. A modeling strategy is developed to incorporate both pores and cracks into the model while preserving the computation performance. The lattice nature of DEM is used for the modeling of crack thickness that are smaller than the discrete element size. A method to compute the crack thickness from gray level images is proposed. Virtual quasi-static tests are performed on a sample of yttria-stabilized-zirconia. The results are in accordance with the literature data, such as the anisotropy and the non-linear behavior. The model is helpful to precisely investigate the role of the microscopic components, and micro-cracking on the macroscopic failure. • Crack thickeness is computed by image analysis and modeled in a numerical model. • Non-linear behavior in compression is due to crack closure with increasing pressure. • Cracks are responsible for transverse isotropy. • A coupling effect between pores and cracks is identified. • A DEM tensile failure criterion allows modelling macroscopic failure in compression. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Titanium hydride is widely considered as an important hydrogen storage material due to its high capacity, stability and low cost. The microstructure of titanium hydride, which is usually induced by the hydrogenation of titanium, strongly influences its storage performance. However, the relationship between the hydrogenation conditions and the derived microstructure of titanium hydride is still unclear, limiting the development of its structure design strategy. In this work, the microstructure of titanium hydride is correlated with its hydrogenation conditions through the thermodynamics and kinetics. By evaluating the effects of the hydrogenation temperature, pressure and cooling rate, three classes of the hydrogenation processes were clarified: kinetic-limited, continuous and stepwise. Besides, according to the SEM and FIB-STEM results, these different processes are confirmed to greatly vary the bulk microstructure. It is concluded that a fast and continuous transition induces a broken bulk morphology, while a stepwise process leads to a larger bulk grain size. In summary, this study presents a framework for designing titanium hydride structures by modifying phase transition processes through careful adjustment of hydrogenation parameters, namely, a condition-process-structure relationship. This relationship offers crucial guidance in managing the grain refinement or coarsening of hydrides within hydrogen storage components and metallurgical applications. • Effect of hydrogenation conditions on the microstructure of TiD x was studied by electron microscopy. • Marked SEM shows the surface morphology of TiD x exhibited negligible change after hydrogenation. • FIB-STEM shows that the cross-section morphology of TiD x varies significantly according to the hydrogenation conditions. • Three classes of the hydrogenation processes were clarified as kinetic-limited, continuous and stepwise. • Fast and continuous phase transition fractures bulk, while a stepwise one induces relative larger grains. [ABSTRACT FROM AUTHOR]

• Reconstructed a high-precision three-dimensional structure of nanoporous materials. • Create a microstructure descriptor database of nanoporous materials. • Establish a quantitative correlation between microstructure descriptors and macroscopic thermal conductivity. • Propose three categories of structure descriptors with the greatest effect on thermal conductivity. The intricate interplay between microstructure and macroscopic transfer processes in porous materials has long been recognized, yet achieving a definitive link between them remains a formidable challenge. Herein, we propose an effective approach to address this challenge by introducing a high-precision 3D reconstruction and structure descriptor database analysis method of nanoporous aerogels, which enables deeper understanding and accurate predictions of structure-directed properties. By employing focused ion beam-scanning electron microscope (FIB-SEM) technique supplemented with image preprocessing and image segmentation, we successfully built a 3D reconstruction model that exhibits high consistency with experimental results. Then, a structure descriptor database from the view of original porous structure, structure connectivity, and topological information is established, and 10 descriptors are preliminarily filtered relevance with thermal conductivity. Consequently, the quantitative relationship between descriptor and thermal conductivity is evaluated via a back propagation (BP) neural network, and three categories structure descriptors which have the most significant impact are determined as (i) the description of gaseous heat transfer pathways, (ii) the description of three-dimensional connectivity, and (iii) the description of interface complexity. With the profound understanding of structure descriptor, the present work offers a novel, structure-focused strategy that closely link the microstructure to macroscopic properties of porous materials. [ABSTRACT FROM AUTHOR]

In the present study, solid oxide cells (SOCs) were operated in the electricity generation (solid oxide fuel cell, SOFC) mode and the hydrogen production (solid oxide electrolysis cell, SOEC) mode. The fuel electrodes fabricated with nickel-gadolinia doped ceria (Ni-GDC) and nickel-yttria stabilized zirconia (Ni-YSZ) composites were investigated. The correlations between changes in the microstructure and degradation of electrochemical performance are discussed. The degradation mechanisms correlated with Ni phase were found to be similar for Ni-GDC and Ni-YSZ electrodes. On the other hand, the stability of the ceramic phase differs significantly between the two electrode materials.

Summary: Combined focused ion beam and scanning electron microscope (FIB‐SEM) tomography is a well‐established technique for high resolution imaging and reconstruction of the microstructure of a wide range of materials. Segmentation of FIB‐SEM data is complicated due to a number of factors; the most prominent is that for porous materials, the scanning electron microscope image slices contain information not only from the planar cross‐section of the material but also from underlying, exposed subsurface pores. In this work, we develop a segmentation method for FIB‐SEM data from ethyl cellulose porous films made from ethyl cellulose and hydroxypropyl cellulose (EC/HPC) polymer blends. These materials are used for coating pharmaceutical oral dosage forms (tablets or pellets) to control drug release. We study three samples of ethyl cellulose and hydroxypropyl cellulose with different volume fractions where the hydroxypropyl cellulose phase has been leached out, resulting in a porous material. The data are segmented using scale‐space features and a random forest classifier. We demonstrate good agreement with manual segmentations. The method enables quantitative characterization and subsequent optimization of material structure for controlled release applications. Although the methodology is demonstrated on porous polymer films, it is applicable to other soft porous materials imaged by FIB‐SEM. We make the data and software used publicly available to facilitate further development of FIB‐SEM segmentation methods. Lay Description: For imaging of very fine structures in materials, the resolution limits of, e.g. X‐ray computed tomography quickly become a bottleneck. Scanning electron microscopy (SEM) provides a way out, but it is essentially a two‐dimensional imaging technique. One manner in which to extend it to three dimensions is to use a focused ion beam (FIB) combined with a scanning electron microscopy and acquire tomography data. In FIB‐SEM tomography, ions are used to perform serial sectioning and the electron beam is used to image the cross section surface. This is a well‐established method for a wide range of materials. However, image analysis of FIB‐SEM data is complicated for a variety of reasons, in particular for porous media. In this work, we analyse FIB‐SEM data from ethyl cellulose porous films made from ethyl cellulose and hydroxypropyl cellulose (EC/HPC) polymer blends. These films are used as coatings for controlled drug release. The aim is to perform image segmentation, i.e. to identify which parts of the image data constitute the pores and the solid, respectively. Manual segmentation, i.e. when a trained operator manually identifies areas constituting pores and solid, is too time‐consuming to do in full for our very large data sets. However, by performing manual segmentation on a set of small, random regions of the data, we can train a machine learning algorithm to perform automatic segmentation on the entire data sets. The method yields good agreement with the manual segmentations and yields porosities of the entire data sets in very good agreement with expected values. The method facilitates understanding and quantitative characterization of the geometrical structure of the materials, and ultimately understanding of how to tailor the drug release. [ABSTRACT FROM AUTHOR]

A typical Longmaxi (LMX) shale sample from Sichuan basin, China, is investigated in three dimensional through multiscale tomography methods spanning pixel sizes from 3.25 μm to 10 nm, combining X-ray computed tomography and focused ion beam-scanning electron microscopy imaging techniques. Pores, organic matter (OM) and pyrite were segmented and reconstructed at multiple scales and the representative elementary volume (REV) of each phase at different scales based on the convergence of error bars in the volume fraction are determined. Results show that REVs at each scale varied between different phases. The determination of REV defined the applicable scale of different methods as well as the appropriate scales of specific structures. Porosity of LMX shale determined at different scales shows significant difference at two orders of magnitude. This difference likely was caused by structural heterogeneity together with the limitations of methods. This study confirms that REV is a feasible and powerful approach in modeling shale using multiscale 3D imaging. The application of multiscale 3D imaging techniques to worldwide shale gas reservoirs could allow for significant insights into the assessment of migration mechanisms within low-permeability systems. Image 1 • Longmaxi shale is visualized in 3-D across the mm to nm scale using complementary methods. • Integrated imaging illustrates microstructural complexities of increasing heterogeneity at higher resolutions. • REVs at multiscale are determined, which defines the applicable scale of different methods. • The porosity changes with the observing scale and is likely to peak at about 250 μm within the mm scale. [ABSTRACT FROM AUTHOR]

Highlights • DIR-SOFC time-dependent numerical model was developed. • Numerical solver verified analytically, with relative error below 5 × 10−3%. • Anode microstructural parameters determine the heat balance in DIR-SOFC cell. • Fuel starvation the most likely to occur in upstream of the DIR-SOFC cell. • Fuel starvation unable to prevent in DIR-SOFC, if methane and steam only are supplied. Abstract In this paper, a transient microstructure-oriented numerical simulation of a planar Direct Internal Reforming Solid Oxide Fuel Cell (DIR-SOFC) is delivered. The performance criteria in a direct steam reforming for a fuel starvation scenario are analyzed in order to optimize the underlying process. The proposed two-dimensional multiscale model takes into account mass and heat transport, electrochemistry, as well as the intrinsic steam-reforming kinetics. In the paper, the methane/steam reforming process over the Ni/YSZ catalyst is experimentally investigated to verify the used chemical reaction model. A three-dimensional digital microstructure representation of the commercial anode is analyzed using a Focused Ion Beam-Scanning Electron Microscope (FIB-SEM) and the nickel-pore contact surface is calculated to relate the reforming reaction rate to the catalyst's active area. Based on the complete DIR-SOFC model, a parametric study is carried out, to simulate the dynamic response of a fuel cell for different design and operating conditions. The results prove the dominant impact of inlet fluid temperature and methane content on the calculated distribution of hydrogen across the channel, while the collected current density was found to be a less important factor. The simulations indicate, that in the case of the direct reforming, fuel starvation is likely to occur in the upstream of the anode channel, where the reforming reaction does not keep up with producing hydrogen. The obtained results provide a significant insight into safe and efficient control strategies for Solid Oxide Fuel Cells. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • A new nanocomposite magnet (H c = 9.7 kOe and σ sat. = 171 emu/g) was developed. • High-pressure torsion was applied to nanocomposite magnets to induce texture. • The microstructures were investigated by TEM and FIB-SEM both in 2D and 3D. • The size and shape of the individual α-Fe phase particles were quantitatively analyzed. • The multi-phases microstructure was significantly distorted by HPT. Abstract A newly developed isotropic Nd 2 Fe 14 B/α-Fe nanocomposite magnet was subjected to a series of investigations of its microstructure and magnetic properties. The performance of the optimally annealed sample was found to be H c = 9.7 kOe and σ sat. = 171 emu/g. Moreover, an attempt was made to produce anisotropic nanocomposite magnets by a high-pressure torsion (HPT) experiment performed at room temperature. The microstructural analyses by TEM in 2D and by FIB-SEM serial sectioning in 3D elucidated that the two-phases microstructure is not distorted homogeneously but shear bands (SBs) are formed. It was found that both the hard magnetic Nd 2 Fe 14 B and soft magnetic α-Fe phases are distorted significantly near those SBs even though the crystallographic orientations of the Nd 2 Fe 14 B grains are randomized therein. The relationships between this microstructure developed by HPT and the corresponding magnetic properties are discussed. [ABSTRACT FROM AUTHOR]

Microstructural properties such as relative density, triple phase boundary length, specific surface area, tortuosity factors are often calculated for microstructure-based analysis and modeling of solid oxide fuel cells (SOFCs). A realistic representation of the microstructure is a challenging and important issue for both experiments and modeling. In the present study, statistical correlation functions and a volume expansion method are used to determine the representative volume element size for the analyses of La 0.6 Sr 0.4 Co 0.2 Fe 0.8 O 3-δ cathode microstructures in SOFCs. [ABSTRACT FROM AUTHOR]

It is known that an overnitridation process significantly improves the coercivity of coarse Sm-(Fe,M)-N magnet powder (M = Cr, Mn, Ti, V) and also introduces a unique microstructure in the particles wherein nanocrystalline cells are separated by amorphous walls (=frequently called nano-cell like structure). It has however been reported that those nanocrystalline cells rotate spontaneously during overnitridation and thus the final powder product becomes unfortunately isotropic. The phenomena have widely been known for more than two decades but the formation/rotation mechanism of the nano-cell like structure is not well understood yet. In this study, the evolutions of the magnetic properties and the microstructure during overnitridation were investigated in greater detail. The multi-scale microstructural observation technique that combines the recent electron microscopic machines disclosed what was occurring in the particles during overnitridation; it was found that the local nitrogen content and the microstructure in a particle are highly heterogeneous and the spontaneous rotation, surprisingly, do not occur. [ABSTRACT FROM AUTHOR]

The size, shape and distribution of different phases in thermoplastic polyolefin (TPO) blends and composites are critical to the properties of the materials, but can be difficult to characterise. Here we report the combination of heavy metal staining and focused ion beam - scanning electron microscopy (FIB-SEM) to reveal the three-dimensional (3D) structure of an elastomer-modified poly(propylene) and a talc filled elastomer-modified poly(propylene). High-quality, high-resolution serial images were collected and the 3D structures were characterised quantitatively. [ABSTRACT FROM AUTHOR]

Pore-scale simulations using a nanoscale FIB-SEM three dimensional microstructure have been used to estimate the absolute permeability and diffusive tortuosity of a representative limestone sample collected from the Arab Formation (Jurassic) carbonate gas reservoir of Abu Dhabi, United Arab Emirates. Estimated absolute permeability (k) values are in excellent agreement with reported experimental permeability values. However, estimated diffusive tortuosity (τ d ) values required to calculate effective diffusivity (D eff ) values of multiple species involved in thermochemical sulfate reduction (TSR) are unrealistically larger than hydraulic tortuosity (τ h ) values. Widely employed empirical correlations (e.g. τ d = φ D m /D eff ) which include only porosity as the factor affecting τ d of natural porous media yield unrealistically smaller values than 1.0. Realistic τ d values were only obtained if a constrictivity factor (δ) was included in the estimation of τ d . Given the difficulty in estimating both δ and τ d values simultaneously, it is proposed that D eff values for reactive transport simulations of TSR, which are commonly calculated as function of φ and τ d (e.g. D eff = (φ/τ d )D m ), should be instead estimated as function of a formation factor (F) (D eff = FD m ). In the proposed expression F accounts for the combined effect of porosity, tortuosity and constrictivity (F = δφ/τ d ). Our pore-scale simulation results shows that F can be accurately estimated from pore-scale simulations using FIB-SEM 3D images. [ABSTRACT FROM AUTHOR]

An accurate method for three-dimensional reconstruction of microstructures is developed to analyse mass transport phenomena in microporous layers (MPLs). The proposed method involves the use of focused ion beam–scanning electron microscope tomography. Numerical calculations of the structural and mass transport properties of MPLs are conducted using the reconstruction results and these results are found to be in good agreement with experimental results, demonstrating the accuracy of the new method. [ABSTRACT FROM AUTHOR]

In the present study, the polarization characteristics of La 0.6 Sr 0.4 Co 0.2 Fe 0.8 O 3 (LSCF) - Gd 0.1 Ce 0.9 O 1.95 (GDC) composite cathodes with different volume ratios were investigated. Samples with volume ratios of 20:80, 30:70, 50:50, 70:30 and 100:0 vol % were tested. The electrochemical impedance spectroscopy tests and current voltage curve measurements were carried out for the current densities from 0 to 0.2 Acm −2 with an interval of 0.05 Acm −2 . The results showed that a volume ratio of LSCF:GDC = 30:70 composite cathode led to the lowest overpotential, and the overpotential increased in the order of 30:70, 50:50, 70:30, 100:0, 20:80 vol %. Three dimensional microstructures of composite cathodes were reconstructed and quantified by dual beam focused ion beam-scanning electron microscope (FIB-SEM). The results showed that neither LSCF surface area nor triple phase boundary (TPB) alone could explain the dependence of polarization characteristics on volume ratios. Current and electrochemical potential distributions were simulated by the Lattice Boltzmann method, in which both surface and TPB reactions were considered. Prediction considering both surface and TPB reactions could predict qualitatively the dependence of overpotentials on LSCF - GDC cathode composition. [ABSTRACT FROM AUTHOR]

Ammonia decomposition rate on a conventional porous Ni-YSZ anode of solid oxide fuel cells (SOFCs) is experimentally investigated under various temperatures and gas compositions to formulate a reaction rate equation. It is confirmed that the decomposition rate depends not only on the partial pressure of ammonia but also on that of hydrogen at the common operating conditions of SOFCs, with larger hydrogen concentration significantly reducing the decomposition rate. 3D microstructure of the tested Ni-YSZ anode is analyzed using the focused ion beam and scanning electron microscope (FIB-SEM), and microstructural parameters are quantified. By using the quantified Ni–Pore interface area density, a reaction rate model for a unit reaction area in Ni-YSZ anodes is obtained. The proposed model is then applied to a simple computational fluid dynamics (CFD) model for validation. The proposed reaction rate model can be applied to a variety of numerical analysis of ammonia decomposition on Ni-YSZ anodes having different microstructures, and expected to be useful for the analysis of ammonia-fed SOFCs. [ABSTRACT FROM AUTHOR]

The electrochemical performance of the lithium-ion battery (LIB) is intimately linked to the electrodes' microstructure dictated by the arrangement of the different constituents. The conductive binder domain (CBD) is of critical importance to battery performance; however, the impact of CBD content on electrode performance is not uniquely identified without altering its morphology. Herein, we use realistic digital cathode microstructures reconstructed from focused ion beam scanning electron microscopy (FIB-SEM) tomography with multiple magnification levels for two NMC111 cathodes to assess the sensitivity of the effective electronic conductivity to the intrinsic conductivity of the CBD and active material (AM), deconvolute the impact of CBD content from morphology on effective transport properties, and highlight the impact of CBD nanoporosity on the pore phase tortuosity. The effective electronic conductivity is more sensitive to changes in the bulk conductivity of the conductive additives where increasing their conductivity by one order of magnitude results in a 10-fold increase in the effective conductivity. Additionally, while the CBD content alone with fixed morphology brings about a nonlinear change in the effective conductivity, the CBD morphology is critical even though it becomes less significant at high CBD contents. Finally, the CBD nanoporosity can lower the tortuosity by ∼ 17 %. [Display omitted] • Transport properties of NMC111 electrodes were studied using FIB-SEM and modeling. • The conductive binder domain (CBD) was placed using two stochastic algorithms. • The relation between the amount of CBD and the effective conductivity is nonlinear. • CBD morphology becomes less significant at high CBD contents. • CBD reconstruction algorithms must preserve AM/CBD and pore/CBD interfacial areas. [ABSTRACT FROM AUTHOR]

Keywords: Dentin; microstructure; FIB-SEM; biomechanics; micro-sample machining and testing EN Dentin microstructure FIB-SEM biomechanics micro-sample machining and testing S90 S92 3 01/29/21 20191002 NES 191002 1. FIB-SEM machining A sample for microtensile test has been successfully machined using FIB-SEM (Figure 3). The complexity of dentin hierarchical structure can be revealed using FIB-SEM "Slice and View" technique in addition to TEM examination that can be done on a FIB-SEM milled sample. [Extracted from the article]

In this study, the diffusion induced stress of LiCoO 2 half cell with a realistic 3D microstructure has been studied using finite element method. The electrochemical properties under various C rates were studied. The discharged curves under various C rates were simulated. Results show that the potential drops significantly with the increase of C rates. The lithium ion concentration distribution under high discharging rates shows strong inhomogeneity. At high C rates, the small LiCoO2 particles near the separator have higher lithium ion concentration because of the shorter lithium migration and diffusion paths. The diffusion induced stress inside LiCoO2 particles was calculated coupled with lithium diffusion. The results show that the stress near the concave and convex regions is the highest. The neck regions of the connected particles will break first and form several isolated particles. For isolated particles, cracks are more likely to form on the surface rather than inside the particle. Failure may occur in large grains ahead of small grains. [ABSTRACT FROM AUTHOR]

Self-made conventional nickel-yttria-stabilized zirconia composite anodes after reduction and 500 h operation were analyzed by three-dimensional microstructure reconstruction based on focused ion beam-scanning electron microscopy technique. Interfacial area, three-phases-boundary density and phase volume fraction were measured based on the three-dimensional microstructure reconstruction to quantitatively study the statistical characterization of solid oxide fuel cell nickel-yttria-stabilized-zirconia anode microstructure before and after operation. It is found that for anode operated with long time, it is necessary to increase the corresponding three-dimensional reconstruction size to suppress the influence of microstructure variation caused by Ni agglomeration in order to obtain more accurate microstructural quantification information. [ABSTRACT FROM AUTHOR]

One of the main goals in lithium ion battery electrode design is to increase the power density. This requires insight in the relation between the complex heterogeneous microstructure existing of active material, conductive additive and electrolyte providing the required electronic and Li-ion transport. FIB-SEM is used to determine the three phase 3D morphology, and Li-ion concentration profiles obtained with Neutron Depth Profiling (NDP) are compared for two cases, conventional LiFePO 4 electrodes and better performing carbonate templated LiFePO 4 electrodes. This provides detailed understanding of the impact of key parameters such as the tortuosity for electron and Li-ion transport though the electrodes. The created hierarchical pore network of the templated electrodes, containing micron sized pores, appears to be effective only at high rate charge where electrolyte depletion is hindering fast discharge. Surprisingly the carbonate templating method results in a better electronic conductive CB network, enhancing the activity of LiFePO 4 near the electrolyte-electrode interface as directly observed with NDP, which in a large part is responsible for the improved rate performance both during charge and discharge. The results demonstrate that standard electrodes have a far from optimal charge transport network and that significantly improved electrode performance should be possible by engineering the microstructure. [ABSTRACT FROM AUTHOR]

The effects of the morphology and the distribution of secondary phases on the bio-corrosion properties of magnesium (Mg) alloys are significant. Focused Ion Beam (FIB) tomography and Micro X-Ray computed tomography (Micro-CT) have been used to characterise the morphology and distribution of (α-Mg + MgZn) and (α-Mg + Ca 2 + Mg 6 + Zn 3 ) eutectic phase mixtures in as-cast Mg–3Zn and Mg–3Zn–0.3Ca alloys, respectively. There were two different 3D distributions: (i) an interconnected network and (ii) individual spheres. The tomography informed our understanding of the relationship between the distribution of secondary phases and the development of localized corrosion in magnesium alloys. [ABSTRACT FROM AUTHOR]

A one-dimensional numerical model of a nickel-infiltrated gadolinium-doped ceria (Ni-GDC) electrode has been developed to investigate the effects of electrode microstructure on performance. Electrode microstructural information was obtained with focused ion beam tomography and microstructural parameters were quantified, such as tortuosity factor, surface area and particle/pore sizes. These have been used to estimate the effective transport coefficients and the electrochemical reaction rate in the electrodes. GDC was considered as a mixed ionic and electronic conductor and hence the electrochemical reaction is assumed to occur on the GDC-pore contact surface, i.e. double-phase boundaries (DPBs). Sensitivity analysis was conducted to investigate the effect of electrode microstructure on both transport properties and electrochemical activity, including the effect of DPB density, GDC tortuosity factor and pore size. The developed model offers a basis to understand the microstructure-performance relationships and to further optimize the electrode microstructures. [ABSTRACT FROM AUTHOR]

The surface treatment of aluminium alloys under steam containing KMnO 4 and HNO 3 resulted in the formation of an oxide layer having a thickness of up to 825 nm. The use of KMnO 4 and HNO 3 in the steam resulted in incorporation of the respective chemical species into the oxide layer. Steam treatment with solution containing HNO 3 caused dissolution of Cu and Si from the intermetallic particles in the aluminium substrate. The growth rate of oxide layer was observed to be a function of MnO 4 − and NO 3 − ions present in the aqueous solution. The NO 3 − ions exhibit higher affinity towards the intermetallic particles resulting in poor coverage by the steam generated oxide layer compared to the coating formed using MnO 4 − ions. Further, increase in the concentration of NO 3 − ions in the solution retards precipitation of the steam generated aluminium hydroxide layer. [ABSTRACT FROM AUTHOR]

In this research a cell stack with standard power output of 100 [W] was tested over a period of 3700 h. After the long-term operation a subsequent post-test analysis of the anode microstructure was conducted using a combination of focused ion beam and scanning electron microscopy. Obtained data was reconstructed into three-dimensional images, based on which the microstructure parameters were obtained. The microstructure parameters were quantified at three different locations in the selected cell; the inlet, the middle and the outlet. This is the first paper in the open literature, known to the authors, that uses the three dimensional microstructure reconstruction technique to evaluate the local evolution of a SOFC anode's microstructure. The obtained results indicate strong non-homogeneous microstructure morphology changes after long-term operation. [ABSTRACT FROM AUTHOR]

In this research a 100 W solid oxide fuel cells (SOFCs) stack was tested. After 3,700 hours of continuous operation a subsequent post-test analysis of the anodes' microstructure was conducted using a combination of focused ion beam and scanning electron microscopy. The obtained data was reconstructed into three-dimensional images, based on which the microstructure parameters were obtained. The microstructure parameters were quantified at nine different locations in the stack. The discussion focuses on tripe phase boundaries as the most important microstructure parameter strongly affecting the anode performance and degradation. The obtained results indicate strong non-homogeneous microstructure morphology changes after long-term operation. [ABSTRACT FROM AUTHOR]

Since sintering of sub-micron-sized particles is a critical phenomenon affecting the electrochemical performance and reliability of solid oxide fuel cell systems, a better understanding of this microstructure-related process is of great importance. In this study, we show that kinetic Potts Monte Carlo modeling is capable of quantitatively predicting the three-dimensional (3D) microstructure evolution over an entire stage of nickel sintering at the sub-micron scale. This is achieved through direct comparison of simulation results and 3D microstructural analysis using focused ion beam–scanning electron microscopy. We show that grain boundary diffusion is the dominant mechanism on densification, while surface diffusion has an impact on the coarsening during sub-micron scale sintering, only acting as one of the multiple mechanisms of sintering. [ABSTRACT FROM AUTHOR]

In the present study, correlation between solid oxide fuel cell anode microstructure and electrochemical performance during redox cycles was investigated. Electrolyte-support cell with nickel/yttria stabilized zirconia composite anode was prepared and tested under discharge process with redox cycles. Redox treatment was basically conducted every 20 h during discharge process. Polarization resistance decreased just after redox treatment and increased during discharge process. Enhancement of cell performance after every redox cycles and faster degradation in the following discharge process were observed. Polarization resistance gradually increased as redox cycles were repeated. Focused ion beam-scanning electron microscopy (FIB-SEM) observation was conducted for reconstructing the three dimensional microstructures of the tested samples. From the three dimensional microstructure reconstruction, it is found that the shape of nickel particle got thinner and complicated after redox cycles. Triple phase boundary (TPB) length increased after redox treatment and decreased after discharge process. This TPB change was highly associated with Ni connectivity and Ni specific surface area. These microstructure changes are consistent with the change of cell performance enhancement after redox treatment and degradation after discharge process. However, TPB length density kept on increasing as redox cycles are repeated, which is inconsistent with the gradual degradation of anode performance. [ABSTRACT FROM AUTHOR]

This paper reports the evaluation of the electrochemically active region in solid oxide fuel cell (SOFC) electrodes through experimental, numerical and semi-analytical approaches. In the experiment, anodes with several different thicknesses were fabricated and their performance was measured to find its dependence on the anode thickness, microstructure and operating conditions. The three-dimensional (3D) microstructure of the anodes was imaged using focused ion beam scanning electron microscopy (FIB-SEM) and the microstructural parameters were quantified. One-dimensional (1D) and 3D numerical simulations based on the actual 3D microstructures were carried out to investigate the active thickness in the anodes. The validity of the numerical models was confirmed by comparing the results with the experiment. The active thickness, i.e., the electrochemically active region within the anode, is discussed using the verified simulation models to find its dependence on various conditions. The active thickness was found to depend on the microstructure and the operating conditions. We then attempted to find a simple expression for the active thickness useful for practical applications with semi-analytical discussion. The developed descriptions expressed the quantitative dependence of the active thickness on the effective ionic conductivity, exchange current density and area-specific current density. [ABSTRACT FROM AUTHOR]

Abstract: This paper, for the first time, demonstrates the three-dimensional imaging of nano-particle infiltrated Ni–GDC (gadolinia-doped ceria) electrodes using focused ion beam tomography. Microstructural parameters of the actual electrode microstructure are quantified, such as volume fraction, TPB density and mean particle/pore sizes. These microstructural parameters reveal that the infiltrated electrodes have eight times larger TPB density than conventional electrodes fabricated by powder mixing and sintering methods. Comparison between the infiltrated electrodes and conventional electrodes indicates that the infiltrated electrodes have a greater potential to independently control metal particle size, porosity and TPB density, which is a significant advantage in developing design optimized electrode microstructures. [Copyright &y& Elsevier]

This work provides discussion on the subject of deriving tortuosity from a saturation current and a mass transport model. In the conducted research an anode-supported solid oxide fuel cell (SOFC) with Nickel/Yttria-Stabilized Zirconia (Ni/YSZ) anode, Yttria-Stabilized Zirconia (YSZ) electrolyte, and Lanthanum Strontium Cobalt Ferrite oxide (LSCF) cathode was tested. Current densities under concentration polarization were measured for different hydrogen partial pressure on the anodic side. Mass transport through a porous anode was analyzed for the H 2 –N 2 –H 2 O ternary system. Cell performances were measured at 700 [°C] and 800 [°C] with air as an oxidant. Obtained saturation current densities were used for the tortuosity calculations. The presented calculation methodology was based on the Stefan–Maxwell equation and Kundsen diffusion. After the power generation experiment, a three dimensional structure was reconstructed using a combination of scanning electron microscope and focus ion beam milling (FIB–SEM). Finally, tortuosity values derived from the transport limitation and structure analysis were juxtaposed. [ABSTRACT FROM AUTHOR]

The performance degradation of Ni–yttria-stabilized zirconia (Ni–YSZ) cermet anode was measured by impedance spectroscopy at 1000–1200 °C and humidity atmospheres under the open circuit condition in SOFCs. More significant crack formation can be observed at 1200 °C under 40% H2O–60% H2 atmosphere. This crack formation gave rise to interruption of the ionic and electronic conduction path in the in-plane direction of anode layer, resulting in performance deterioration of anode. Focused ion beam-scanning electron microscopy (FIB–SEM) analyses were conducted for the anode layers, and then the 3D microstructures of Ni–YSZ anode were reconstructed. According to analysis of these data, the particle size of Ni was grown to the larger under higher temperature and humidity condition, accompanying with increase of isolated Ni-phase and the reduction of triple phase boundary (TPB) length. [ABSTRACT FROM AUTHOR]

Abstract: Current methods of image segmentation and reconstructions from scanning electron micrographs can be inadequate for resolving nanoscale gaps in composite materials (1–20nm). Such information is critical to both accurate material characterizations and models of piezoresistive response. The current work proposes the use of crystallographic orientation data and machine learning for enhancing this process. It is first shown how a machine learning algorithm can be used to predict the connectivity of nanoscale grains in a Nickel nanostrand/epoxy composite. This results in 71.9% accuracy for a 2D algorithm and 62.4% accuracy in 3D. Finally, it is demonstrated how these algorithms can be used to predict the location of gaps between distinct nanostrands — gaps which would otherwise not be detected with the sole use of a scanning electron microscope. [Copyright &y& Elsevier]

Abstract: In this work, the effect of porous interlayer on the microstructural change of LSM cathodes and yttria-stabilized zirconia (YSZ) electrolyte was investigated under a current-accelerated condition at 1000 °C. The polarization resistance of LSM cathode on bare yttria-stabilized zirconia (YSZ) electrolyte decreased significantly after discharge at 1.2 A cm−2 for 5 h, and then started to increase gradually. However, when a porous YSZ interlayer was employed between LSM cathode and YSZ electrolyte, the polarization resistance did not increased even after discharge at the same condition for 40 h. The performance changes of the two kinds of cathodes were related with the microstructural change of the interface between LSM cathode and YSZ interlayer. Quantitative analysis for the microstructural change of LSM cathode on YSZ interlayer revealed that even after discharge at 1.2 A cm−2 for 40 h, 90% of the triple phase boundary of LSM, YSZ and gas phase remained active for oxygen reduction reaction. On the other hand, the LSM cathode on YSZ electrolyte with a porous Sm-doped ceria interlayer showed remarkable long-term stability even after discharge at 1.2 A cm−2 for 160 h. [Copyright &y& Elsevier]

Ni-YSZ anode of solid oxide fuel cells (SOFCs) with three different compositions are examined and compared through electrochemical measurement, microstructural analysis, and numerical simulation. Three-dimensional (3D) microstructure of the porous anodes is directly observed using focused ion beam and scanning electron microscope (FIB-SEM), and microstructural parameters such as phase connectivity and three-phase boundary (TPB) density are quantified to correlate the microstructure to the performance. 3D numerical simulation using the obtained microstructure is conducted considering the various transport phenomena and the electrochemical reaction in the anodes to predict their overall electrochemical performance. The performance of the Ni:YSZ = 30:70 anode is measured significantly lower than those of the Ni:YSZ = 50:50 and 70:30 anodes, which is attributed to the elongation of the ionic transport pathways. The poor connectivity of the Ni phase in the Ni:YSZ = 30:70 anode shifts the electrochemically active region far from the anode-electrolyte interface, resulting in higher Ohmic loss. The amount and distribution of the effective TPB associated with the phase connectivity are essentially important to explain the anode performance. The 3D numerical simulation qualitatively reproduces the anode performance and gives detailed information about the internal states of the anodes such as the distribution of the charge-transfer current. [ABSTRACT FROM AUTHOR]

Abstract: Improving the accuracy of the sub-grid-scale (SGS) model designed for three-dimensional (3D) numerical simulation of solid oxide fuel cell (SOFC) electrodes is accomplished by introducing an adaptive power index, which is determined by the length ratio between the grid size and the characteristic scale of the original porous structure. The main function of the SGS model is to maintain the quality of the voxel-based structural information in a resampled structure used as the calculation grid system by considering a structure with a characteristic scale that is smaller than the grid size. Improvement of the simulation accuracy and reduction of the computational load can be expected with the SGS models. In this study, four types of SGS models are investigated to clarify their effect and applicability. They are featured by (1) volume conservation, (2) interfacial connectivity, (3) power law with a constant power index, and (4) power law with an adaptive power index, respectively. The latter two models are based on a power-law expression of the local tortuosity factor and are newly proposed in this study. Although the first three models have a positive contribution to maintain the structural information in the resampled structure, their applicability is not completely assured in a wide range of grid sizes. In the last model, we introduce a length ratio between the grid size and the characteristic scale of the original porous structure in order to let the model exert its effect preferably in accordance with the grid size. The model successfully represents the original structural information in a wide range of grid sizes and improves the simulation accuracy within the given computational resources. [Copyright &y& Elsevier]

Abstract: Cathode-supported tubular-type cells fabricated by TOTO Ltd. degraded gradually during long-term operation, and a dissection analysis of cells revealed a microstructural change in the anode. In this study, then, the direct observation of the degraded anode was conducted to clarify the influence of this structural change on the performance by using a dual-beam focused ion beam–scanning electron microscopy (FIB–SEM). The microstructural parameters of Ni–(Sc2O3)0.10(CeO2)0.01(ZrO2)0.89 cermet anode were quantitatively evaluated. The significant reduction in triple phase boundary (TPB) length was confirmed, accompanied with the migration and sintering of nickel particles especially in the vicinity of anode/electrolyte interface. [Copyright &y& Elsevier]

Abstract: In this work, discharge operation at a large current density was conducted for strontium-doped lanthanum manganite (LSM) cathodes, and the change in performance and microstructure of the interface between LSM cathode and YSZ electrolyte was investigated. For (La0.8Sr0.2)0.97MnO3 (LSM97) with A-site deficiency, the performance was improved in the initial stage of discharge and then started to deteriorate continuously. The microstructural change in the interface between LSM97 and YSZ was quantitatively analyzed by using a dual-beam focused ion beam-scanning electron microscope. It was found that after discharge at 1.2Acm−2 for 60h, the surface of YSZ electrolyte was covered by a dense layer of LSM, accompanied with the formation of closed nanopores in the internal interface between LSM97 and YSZ. For (La0.8Sr0.2)1.03MnO3 (LSM103) with a slight A-site excess, neither apparent formation of dense LSM103 layer along the LSM103/YSZ interface nor performance deterioration was observed during discharge. The mechanism for the structural change of LSM97 cathode was discussed based on the obtained results. [Copyright &y& Elsevier]

Sedimentary carbonate rocks are one of the principal porous structures in natural reservoirs of hydrocarbons such as crude oil and natural gas. Efficient hydrocarbon recovery requires an understanding of the carbonate pore structure, but the nature of sedimentary carbonate rock formation and the toughness of the material make proper analysis difficult. In this study, a novel preparation method was used on a dolomitic carbonate sample, and selected regions were then serially sectioned and imaged by focused ion beam–scanning electron microscopy. The resulting series of images were used to construct detailed three-dimensional representations of the microscopic pore spaces and analyze them quantitatively. We show for the first time the presence of nanometer-scale pores (50–300 nm) inside the solid dolomite matrix. We also show the degree of connectivity of these pores with micron-scale pores (2–5 μm) that were observed to further link with bulk pores outside the matrix. [ABSTRACT FROM AUTHOR]

Abstract: Berea sandstone is the building block for reservoirs containing precious hydrocarbon fuel. In this study, we comprehensively reveal the microstructure of Berea sandstone, which is often treated as a porous material with interconnected micro-pores of 2–5μm. This has been possible due to the combined application of micro-computed tomography (CT) and focused ion beam (FIB)-scanning electron microscopy (SEM) on a Berea sample. While the use of micro-CT images are common for geological materials, the clubbing and comparison of tomography on Berea with state-of-the-art microstructure imaging techniques like FIB-SEM reveals some unforeseen features of Berea microstructure. In particular, for the first time FIB-SEM has been used to understand the micro-structure of reservoir rock material like Berea sandstone. By using these characterization tools, we are able to show that the micro-pores (less than 30μm) are absent below the solid material matrix, and that it has small interconnected pores (30–40μm) and large crater-like voids (100–250μm) throughout the bulk material. Three-dimensional pore space reconstructions have been prepared from the CT images. Accordingly, characterization of Berea sandstone specimen is performed by calculation of pore-structure volumes and determination of porosity values. [Copyright &y& Elsevier]

Abstract: In this work we demonstrate the utility of three-dimensional focused ion beam–scanning electron microscopy nanotomography for understanding composite electrode performance and degradation. Phase connectivity, electrochemically active triple-phase boundary density and phase tortuosity are calculated for a series of anodes with varying Ni-YSZ composition. These structural characteristics, achievable only through three-dimensional interrogation, are shown to play a vital role in determining electrode polarization resistance. Additionally, Ni-YSZ samples are experimentally annealed in hydrogen and reconstructed to quantitatively assess degradation as a function of reduced triple-phase boundary density. [Copyright &y& Elsevier]

Abstract: The percolated or active triple phase boundary (TPB) length per unit volume of Ni–YSZ anode hollow fibers (HFs) containing 60wt.% initial NiO and a spatially varying microstructure were measured using a focused ion beam (FIB)-SEM technique. The measured values of contiguous TPB density were interfaced with a 2-D distributed finite element model of a hollow fiber solid oxide fuel cell. The model was applied to simultaneously solve the ionic and electronic charge balances in the electrodes, which were modelled as overlying continuum materials with effective electronic and ionic conductivities. The model was used to predict the effects of anode microstructure on the distribution of current density, and anode activation polarization. Active TPB lengths of 2.63–8.63µm−2 were measured for the anode depending on location in the fiber wall and local microstructure. The effective anode ionic conductivity was predicted to be crucial to spreading the reaction zone from the anode/electrolyte interface toward the anode current collector. For equal TPB distributions, faster electrochemical kinetics was predicted to constrain anode reaction current generation to within a few micrometers of the anode/electrolyte interface. [Copyright &y& Elsevier]

Abstract: A three-dimensional microstructure of a solid oxide fuel cell (SOFC) anode is directly observed by a focused ion beam and scanning electron microscope (FIB–SEM) technique. Microstructural parameters, which are closely related to transport phenomena and electrochemical reaction in a porous anode, are quantitatively evaluated, such as volume fraction, percolation probability, tortuosity factor, surface-to-volume ratio, and three-phase boundary density. A random-walk-based diffusion simulation is effectively used for quantification. As an application of the quantified parameters, 1D numerical simulation of a SOFC anode is conducted. The predicted anode overpotential agrees well with the experimental counterparts in the condition of 3.0% H2O–97% H2, 1273K, while it is overestimated at high humidified and low temperature conditions. [Copyright &y& Elsevier]

Abstract: Temperature induced degradation in Solid Oxide Fuel Cell (SOFC) Ni-YSZ anodes was studied using both impedance spectroscopy and three-dimensional tomography via Focused Ion Beam–Scanning Electron Microscopy. A 100h anneal at 1100°C caused a 90% increase in cell polarization resistance, which correlated with the observed factor of ∼2 reduction in the electrochemically active three-phase boundary (TPB) density. The TPB decrease was caused by a significant decrease in pore percolation, and a reduction in pore interfacial area due to pores becoming larger and more equiaxed. The anneal caused no measurable change in average Ni particle size; Ni coarsening was apparently highly constrained in these anodes due to the relatively large YSZ volume fraction and low pore volume. [Copyright &y& Elsevier]