X-ray CT Measurements Research Articles

Operando X-Ray CT Analysis of Silicon/Solid Electrolyte Mechanical Interface of All-Solid-State Battery during Charging and Discharging Reaction

Silicon has a theoretical capacity about 10 times that of graphite, so it is expected to be one of the next-generation anode materials to further increase the capacity of batteries. However, silicon has a large volume change during charging and discharging, which result in poor cyclability. Although morphological change of silicon has been shown in a lot of previous studies, most of them are ex-situ observations using electron microscopes such as SEM and are two-dimensional observations1). Moreover, many previous studies target liquid battery. It is necessary to understand the expansion and shrinkage mechanism of silicon to improve all-solid-state battery performance using silicon anode. Synchrotron X-ray computed tomography (X-ray CT) is a technique that can measure the internal structure of a battery in three dimensions with micrometer-order spatial resolution in a short time. In addition, operando X-ray CT measurement is possible under charging and discharging in an all-solid-state battery2). In this study, we analyzed that morphological changes of silicon during charging and discharging by operando X-ray CT measurements.We used LiNi1/3Co1/3Mn1/3O2 (NCM), Li6PS5Cl (LPSCl) and acetylene black (AB), which were mortar-mixed in a mass ratio of 1:1:0.1 as the cathode composite material, and Si, LPSCl and AB in a mass ratio of 1:2.78:0.42 as anode composite material. Si｜LPSCl｜NCM all-solid-state cells were assembled. X-ray CT measurements at SPring-8 BL20XU using 20 keV X-rays while performing constant current charge/discharge measurement at 2.3×10-3 A cm-2. The pixel resolution was 0.5 µm. A silicon particle was extracted from the X-ray CT images obtained from X-ray CT measurements to observe the morphological changes of silicon during charging and discharging reaction. Then, change of the silicon volume and the contact area fraction of silicon particle and LPSCl solid electrolyte were calculated.Volume expansion was observed with lithiation of silicon and volume shrinkage with delithiation of silicon. As the lithiation process, silicon density decreased, and silicon was observed to be darker. As the delithiation process, cracks appeared in the silicon particle as the expanded silicon shrank. In addition, the silicon/solid electrolyte interface changed so that the silicon formed shell voids at the surface of silicon particles. This indicates that the plasticity of the LPSCl solid electrolyte cannot follow the form change of the interface. However, shell voids in the interface were formed for all directions, but some parts remained in contact area between the silicon particle and the solid electrolyte. After the second cycle of lithiation, cracks in the particle and the voids in the interface between the silicon particle and the solid electrolyte that had been formed due to the shrinkage of silicon as the delithiation disappeared by the re-lithiation. However, the re-delithiation caused cracks in the particle in the same area and formed shell voids in the interface again. Moreover, as the second delithiation process, the number of cracks in the particle increased compared with that as the first delithiation. This suggests that the number of cracks in the particle increases as silicon repeated lithiation and delithiation, and so silicon is miniaturized. In addition, a correlation was confirmed between the silicon volume change and the contact area fraction change. After the first cycle, the volume didn’t return to pristine silicon volume and the contact area fraction was reduced compared to pristine silicon. The isolation of the silicon particle from the solid electrolyte interface is suggested to be one of the factors causing the poor cycle performance because of the lithium ion reaction path is limited.1) T. Li, J. Y. Yang, S.G. Lu, H. Wang and H. Y. Ding, Rare Metals, 32, 299-304 (2013).2) Y. Sakka, H. Yamashige, A. Watanabe, A. Takeuchi, M. Uesugi, K. Uesugi and Y. Orikasa, J. Mater. Chem. A, 10, 16602–16609 (2022).

Effects of solid electrolyte particle size and silver-carbon interlayer on lithium deposition in all-solid-state lithium-metal batteries

All-solid-state batteries with lithium-metal anodes are expected to exhibit high performance. For practical application, the growth of lithium dendrites must be suppressed. One method to suppress dendrite growth is to insert a carbon interlayer at the interface between the anode and solid electrolyte (SE). Dendrite growth is related to the anode interface properties and depends on the SE particle size used in the SE layer. Appropriate control of the SE particle size used at the anode interface can improve battery performance. In this study, the effects of SE particle size and carbon interlayer type on lithium-metal deposition morphology are investigated by X-ray CT measurement. The results show that dendrite growth is suppressed when the small-particle SE is used owing to the smaller pores between the SE layer and carbon interlayer. In addition, by controlling the SE particle size distribution using a double SE layer, both high ionic conductivity and dendrite suppression can be achieved. Furthermore, dendrite growth can be suppressed using a silver particle-added carbon interlayer, even with the large-particle SE where dendrites are prone to grow more easily.

(Digital Presentation) Operando X-Ray CT Analysis of Silicon-Solid Electrolyte Mechanical Interface of All-Solid-State Battery

Silicon has a theoretical capacity about 10 times that of graphite is expected to be one of the next-generation anode materials to further increase the capacity of batteries. However, silicon has a large volume change during charging and discharging, which result in poor cyclability. Although morphological change of silicon has been shown in a lot of previous studies, most of them are ex-situ observations using electron microscopes such as SEM and are two-dimensional observations1). Previous studies have shown that silicon may fulfill its potential as an all-solid-state battery anode material with the garnet oxide-based solid electrolyte2). Further understanding of the expansion and shrinkage mechanism of silicon is needed to improve battery performance using silicon anode. Synchrotron X-ray computed tomography (X-ray CT) is a technique that can measure the internal structure of a battery in three dimensions with micrometer-order spatial resolution in a short time. In addition, operando X-ray CT measurement is possible under charging and discharging in an all-solid-state battery3). In this study, we analyzed that morphological changes of silicon during charging and discharging by operando X-ray CT measurements. We used LiNi1/3Co1/3Mn1/3O2 (NCM), Li6PS5Cl (LPSCl) and acetylene black (AB), which were mortar-mixed in a mass ratio of 1:1:0.1 as the cathode composite material, and Si, LPSCl and AB in a mass ratio of 1:2.78:0.42 as anode composite material. Si｜LPSCl｜NCM all-solid-state cells were assembled. X-ray CT measurements at SPring-8 BL20XU using 20 keV X-rays while performing constant current charge/discharge measurement at 2.3×10-3 A cm-2. The pixel resolution was 0.5 µm. A silicon particle was extracted from the X-ray CT images obtained from X-ray CT measurements to observe the morphological changes of silicon during the charging and discharging reaction. Cracks were observed in the silicon particle due to silicon shrinkage during the delithiation process. In addition, the silicon/solid electrolyte interface changed so that the silicon formed shell voids at the surface of silicon particles. This indicates that the plasticity of the LPSCl solid electrolyte cannot follow the form change of the interface. However, shell voids in the interface were formed for all directions, but some parts remained in contact area between the silicon particles and the solid electrolyte. The isolation of silicon particles from the solid electrolyte interface is suggested to be one of the factors causing the poor cycle performance because of the lithium ion reaction path is limited.1) T. Li, J. Y. Yang, S.G. Lu, H. Wang and H. Y. Ding, Rare Metals, 32, 299-304 (2013).2) W. Ping, C. Yang, Y. Bao, C. Wang, H. Xie, E. Hitz, J. Cheng, T. Li and L. Hu, Energy Storage Materials, 21, 246-252 (2019).3) Y. Sakka, H. Yamashige, A. Watanabe, A. Takeuchi, M. Uesugi, K. Uesugi and Y. Orikasa, J. Mater. Chem. A, 10, 16602–16609 (2022).

Analysis of Structural Changes in Practical Batteries during Overcharging Using Synchrotron X-Ray CT Imaging

Lithium-ion rechargeable batteries are desired for applications such as power sources for electric vehicles, which require increased energy density to extend cruising range. In the cathode, increasing the nickel content makes it possible to increase the energy density, but this is problematic due to a decrease in safety. To solve this problem, it is necessary to clarify the phenomena leading to structural breakdown by operando observation[1]. We have developed a system for operando non-destructive observation of the internal structure of all batteries under transient conditions using 100 keV collimated light of SPring-8 beamline. In this study, the difference in the behavior of LiCoO2 (LCO), LiNi0.6Mn0.2Co0.2O2 (NMC622) and LiNi0.8Mn0.1Co0.1O2 (NMC811) during overcharging was discussed in combination with the measurement of the electronic structure of the cathode active materials from the surface to the bulk.A 40-layer laminated battery (1 Ah) was used, with LCO, NMC622 and NMC811 as the cathodes and natural graphite as the anode. After charging to 100% SOC at 1C (1C=160 mAh/g) rate at room temperature, the overcharge process performed under 3C and/or 6C rate from 100% SOC while measuring voltage and temperature. Overcharge behavior inside the battery was observed simultaneously by operando X-ray CT during overcharge process.During the overcharge test at 6C rate, the maximum temperature of the LCO laminated battery was 390 ℃, while NMC811 laminated battery reached over 600 ℃ (Fig. 1). Point 1 in Fig. 1 is the point where changes in the electrode structure begin to be observed by the operando X-ray CT measurements. The point 1 of NMC811 occurred earlier (203 s) than LCO (542 s). From the O-K XAS result (Fig. 1d), the pre-edge (located at 519 ev) of NMC811 was much higher than LCO and NMC622 when overcharging to 200% SOC, meanwhile the O-Ni bond in NMC is more unstable than O in LCO in the overcharged state. The unstable electronic structure of oxygen on the surface of NMC811 is the starting point for the rapid structural change of the battery during overcharging. Reference s : [1] Donal P. Finegan; Mario Scheel; James. Robinson; Bernhard T.; Marco Di M.; Gareth H. Phys.Chem.Chem.Phys. (2016), 18, 30912. Figure 1

Matrix decomposition methods for accurate water saturation prediction in Canadian oil-sands by LF-NMR T2 measurements

This article presents a novel method for quantifying water saturation in oil-sand reservoirs by employing 1D low-field nuclear magnetic resonance (LF-NMR) spin-spin relaxation and bulk density measurements as indicators of pore volume variations. One of the challenges in accurately determining the volumes of bitumen and water in oil-sands is the effective separation of their overlapping T2 signals, attributed to similar spin-spin relaxation decay times and diffusive coupling. Conventional methods require deconvolution of T2 peaks and or experimentation to determine T2 cutoff values, differentiating between bitumen and water signals, notably capillary and clay-bound water. In contrast, our approach predicts the proportion of water by utilizing matrix decomposition methods to compress the T2 relaxation distribution and extract significant components. These components subsequently train the regression model, facilitating the accurate estimation of relative water saturation percentages.The NMR dataset was obtained by benchtop LF-NMR T2 measurements from 82 oil-sand samples, with preserved bitumen and water saturations at both reservoir and ambient temperatures (6 °C and 25 °C), yielding 164 observations. We examined four matrix decomposition methods, including principal component analysis, its variation integrating a kernel function, canonical correlation analysis, and partial least squares regression. X-ray CT measurements and Dean-Stark extraction ascertained the respective sample bulk densities and fluid-solid volume proportions.The PCA model prediction statistics (RMSE = 0.86%, R2 = 0.84), indicate its application can be extended for saturation prediction from NMR and bulk density well logs. Moreover, we underscore the importance of incorporating bulk density measurements and establish the statistical and physical correlations between these measurements and NMR T2 relaxation, providing insights into the approach's efficacy and causality.

Operando X-Ray CT Analysis of Composite Electrode in All-Solid-State Battery Using Silicon Anode

As a next-generation rechargeable battery, all-solid-state battery is expected for used in practical applications, in which electrolyte solution of the current lithium-ion battery is replaced with a solid electrolyte. To further increase the capacity of all-solid-state batteries, silicon is used as the anode active material forming an alloy with lithium. However, in the charge and discharge reaction using silicon anode, poor cycle capability due to the volume change of the silicon alloying reaction has been known. Many reports are limited to the analysis of the volume change of the whole electrode, and there are few reports on the quantitative analysis of the volume change of the silicon active material itself. In this study, X-ray computed tomography (X-ray CT) was used to analyze the expansion and contraction of silicon-active materials in all-solid-state battery. X-ray CT analysis can provide the contacted state information between electrode active materials and solid electrolytes [1]. By operando X-ray CT analysis, the expansion and contraction behavior of silicon particles during charging and discharging on the electrode was studied.Nb-coated LiNi1/3Co1/3Mn1/3O2(NCM), Li10GeP2S12(LGPS), acetylene black (AB) mixed at a weight ratio of 1:1:0.2 were used as the cathode composite. Silicon, LGPS, AB mixed at a weight ratio of 1:1:0.1 were used as the anode composite. All-solid-state battery, Si | LGPS | NCM was assembled in a cylinder with an inner diameter 1 mm. The cell was brought into SPring-8 BL20XU beamline, and the operando X-ray CT measurement was carried out. From the obtained X-ray CT images, the three-dimensional analysis of silicon particles was performed.Mean expansion coefficients of silicon‐particles traced during charging and discharging were calculated. The expansion of silicon particles by charging (lithiation) and the contraction of silicon particles by discharging (delithiation) are confirmed. Furthermore, the volume expansion rate of the silicon particles after the charging is average exceeded 300%. After discharge, silicon shrinkage is observed with delithiation, but the solid electrolyte cannot follow the volume change, and the silicon/solid electrolyte interface is broken. However, the contact is not completely failed, maintaining the partial contact between silicon and the electrolyte.[1] Y. Sakka, H. Yamashige, A. Watanabe, A. Takeuchi, M. Uesugi, K. Uesugi and Y. Orikasa, J. Mater. Chem. A, 10 16602–16609 (2022).Acknowledgement: This work was partially supported by the New Energy and Industrial Technology Development Organization (NEDO), JPNP20004.

Evidence for Solution-Mediated Phase Transitions in Kidney Stones: Phase Transition Exacerbates Kidney Stone Disease

In this study, we investigated calcium oxalate (CaOx) kidney stones and showed direct evidence of the solution-mediated phase transition of calcium oxalate dihydrate (COD; the metastable phase) to calcium oxalate monohydrate (COM; the stable phase). We examined the crystal phases, crystal textures, and protein distributions within thin sections of calcium oxalate kidney stones. Observation with a polarized-light microscope showed that the outline of the mosaic texture, in which COM crystals are assembled in a mosaic pattern, roughly coincides with COD’s crystallographically stable face angles. Microfocus X-ray CT measurement captured the intermediate process of the phase transition, starting inside the COD single crystal and gradually transforming to COM crystals. In addition, the distribution of osteopontin and prothrombin fragment-1, common proteins contained in urine and visualized by multicolor fluorescence immunostaining, showed no apparent striations inside the COM single crystals with the mosaic texture, although the striation is apparent inside the COD single crystals. This is probably because the phase transition of mosaic-like COM occurred in a semiclosed system inside the COD single crystal, so the effect of periodic (day–night, seasonal, etc.) urinary protein concentration changes was small. On the other hand, striations were visible in concentrically laminated COM. This indicated that concentrically laminated COM formed in response to the changes in urinary protein concentrations. From the above, we conclude that the COD single crystals and the concentrically laminated COM seen in CaOx stones are primary structures, and the mosaic COM is a secondary structure that is a pseudomorph formed by the solution-mediated phase transition from COD single crystals.

Laboratory characterization of induced seismicity

Subsurface fluid injection causes an increase in seismic activity near injection sites. To ensure public safety and improve public acceptance of subsurface fluid injection, it is important to understand the underlying mechanisms giving rise to these behaviors and characterize the factors affecting induced seismicity. The work reported here aims to better understand induced seismicity in faulted/fractured subsurface rock formations. A series of experiments are conducted in core flooding and triaxial configurations on test samples with a preexisting fracture/fault to study frictional slipping at small and large scales respectively. The geometries of both surfaces on either side of the fault are characterized using x-ray CT. The extent of fault gouging in a specimen after slipping is quantified by defining a cumulative gouging parameter using x-ray CT measurements before and after the experiment. Acoustic emission (AE) events emanating from the specimens in both configurations are monitored. The results demonstrate that (1) the orientation of fault relative to the major principal stress direction affects the slip characteristics, (2) frictional slipping at a fault can occur at different length scales, (3) with an increase in the scale of slipping, the spectral ratio of low-frequency bins increases while high-frequency bins reduces, and (4) locations on the fault surface that exhibit a sudden change in surface normal are most susceptible to gouging/damage during frictional slipping.

Optimizing X-ray Tomography for Turbine Blade Inspection

Taking pride in developing the most optimal scanning technique for x-ray CT measurement applications

Mapping 3D grain and precipitate structure during in situ mechanical testing of open-cell metal foam using micro-computed tomography and high-energy X-ray diffraction microscopy

• 3D grain structure is mapped and tracked during loading of open-cell metal foam. • Challenges included sample size relative to beam size and large ligament motions. • X-ray CT and far-field HEDM measurements collected at incremental displacements. • New scanning and stitching methodology established for far-field HEDM measurements. • Ligament-tracking code used to express crystal orientation in local reference frame. Open-cell metal foams are ultra-low-density cellular metals with complex hierarchical structures that span bulk, cell, ligament, and sub-ligament scales and give rise to desirable properties such as high strength-to-weight ratio and excellent energy absorption. Although literature suggests that intrinsic material structures at sub-ligament length scales (e.g., grains and precipitates) play an important role in mechanical behavior of open-cell metal foams, there are very few experimental measurements of such structures in three dimensions and for meaningful volumes of foam. This study seeks to map and track the three-dimensional (3D) grain and precipitate structures of an intact volume of open-cell aluminum foam by advancing microstructural characterization techniques that leverage X-ray micro-computed tomography ( μ CT ) and far-field high-energy X-ray diffraction microscopy (FF-HEDM). A 6%-relative-density aluminum foam sample was mechanically tested in compression while μ CT and FF-HEDM measurements were collected at interrupted loading states at beamline 1-ID of the Advanced Photon Source. A new scanning strategy and reconstruction algorithm were established to enable characterization of a foam volume with diameter approximately four times wider than the nominal width of the X-ray beam. The result is a set of maps that detail both the 3D grain and precipitate structures throughout the foam volume at successive strain steps. A novel grain tracking procedure was developed to track individual grains within the foam volume by accounting for the large rigid-body motions that individual ligaments can undergo during mechanical loading. The ability to track grains and precipitate structures in three dimensions throughout large bulk deformation of ultra-low-density polycrystalline materials enables new possibilities for validating numerical models and investigating local failure mechanisms. Furthermore, the methods and procedures developed in this study could be applied to other ultra-low-density structures, such as additively manufactured lattices.

High Resolution Observation of Liquid Water in Polymer Electrolyte Fuel Cell Using X-Ray Nano Computed Tomography

Polymer electrolyte fuel cells (PEFCs) are attracting attention as energy device of low environmental impact because of their high generation efficiency and their emitting only water. The gas supplied to the PEFC is humidified, and water is produced at the cathode catalytic layer by the electrochemical reaction between oxygen and protons. The gas diffusion layer (GDL) and micro porous layer (MPL) in PEFC plays an important role in the transport of oxygen and water. When liquid water accumulates in the GDL, the supply of oxygen to the cathode is inhibited, resulting in poor generation performance. In order to maintain the performance of PEFCs, it is important to manage the water in the cell.Attempts have been made to visualize the liquid water in GDLs and MPLs for better GDL and MPL design; X-ray micro computed tomography (micro-CT) is one powerful tool for this. Visualization of liquid water in GDLs and MPLs using micro-CT has so far revealed the behavior of the produced water[1,2]. However, in previous studies, it has been difficult to visualize liquid water in the catalyst layer, which is the reaction field where the water is produced. This is because the spatial resolution of micro-CT is larger than a µm, which is insufficient for analyzing liquid water in the catalytic layer. X-ray CT measurements with a resolution of at least 150 nm are needed to measure the distribution of liquid water in the cross section of the catalyst layer. In this study, a measurement system to reveal the distribution of liquid water in the catalyst layer was developed using a 150 nm-spatial-resolution X-ray CT with a synchrotron radiation x-ray microscope called X-ray nano-CT.A GDL specimen prepared cut to a disk shape with 1 mm diameter. The GDL specimen mounted on a copper stage with high thermal conductivity connected Peltier element module. The micro-CT and nano-CT measurements were carried out in BL20XU beamline at SPring-8, Japan. An X-ray beam energy was 30 keV with a double crystal monochromator. The nano-CT measurements were performed using Zernike phase contrast with voxel size of 38.4 nm. We measured the micro-CT and nano-CT of the dry condition of the GDL specimen. Then, the GDL specimen injected liquid water was scanned. Injection of liquid water into the GDL specimen is not easy because of water-repellent of GDLs. Helium gas saturated water vapor at 40 °C was sprayed to the GDL at 30 ml/min, then the GDL cooled to 10 °C using a Peltier element module and the vapor was condensed inside of the GDL. The measurement setup is shown in Figure 1. This water injection in GDL method was based on the method reported by Kato et al [2].Figure 2 shows the optical system of the nano-CT used in this study. The optical system of this nano-CT provides a condenser zone plate for sample illumination, a Fresnel zone plate for enlarged image, and phase ring for Zernike phase contrast. These optics allow CT with a high spatial resolution of 150 nm to be measured even for materials with low X-ray absorption.A three-dimensional structure of GDL was revealed by CT measurements in each scale order. The distribution of liquid water in GDL were visualized with nanoscale spatial resolution (Figure 3). We have successfully visualized the three-dimension distribution of liquid water in the GDL with nm order scale using nano-CT. The newly established nano-CT with a spatial resolution of 150 nm order is extremely useful for elucidating liquid-water behavior in PEFCs containing catalyst layers, which was not clear before. Acknowledgements This work is based on results obtained from a NEDO FC-Platform project commissioned by the New Energy and Industrial Technology Development Organization (NEDO). This study was partially supported by the Synchrotron radiation experiments performed at BL20XU of SPring-8 with the approval of the Japan Synchrotron Radiation Research Institute (JASRI) (Proposal numbers 2021A2009, 2021B1015).

Unsteady Three-Dimensional Simulation of Water Condensation in Gas Diffusion Layer

Liquid water accumulates inside polymer electrolyte fuel cells (PEFCs) prevents gas transport and degrades the cell performance. In this study, we performed an unsteady numerical simulation of water condensation and accumulation in the gas diffusion layer (GDL) of PEFCs using the three-dimensional structure of the GDL obtained by X-ray CT measurement. The temperature and gas concentration fields were solved to obtain the amount of condensation, and the volume of fluid (VOF) method was used for the transport of the gas-liquid interface. As a result of the simulation, the region where condensation occurs was identified and the formation mechanisms of the liquid-water structure is observed.

Visualization and evaluation of concrete damage in-service headworks by X-ray CT and non-destructive inspection methods

The durability of concrete irrigation infrastructures decreases easily due to environmental effects, such as the freeze-thawed process. The degree of damage in concrete is, in most cases, evaluated by an unconfined compression test or ultrasonic test. The limiting states of structures are the result of a gradual accumulation of microdefects during the in-service period, which leads to the initiation and development of macroscopic cracks, loss of performance, and Failure. Therefore, to maintain such structures, it is necessary to properly determine the degree of damage by non-destructive testing. For effective maintenance and management of in-service structures, it is necessary to evaluate not only such mechanical properties as strength but also the degree of damage. Quantitative damage evaluation of concrete is proposed by applying the X-ray CT method and related non-destructive inspection, which is based on estimating cracking damage effects. In this study, the damage evaluation of concrete-core samples is investigated by X-ray CT parameters and the non-destructive parameters. The samples tested were taken from the damaged concrete headwork in Niigata, Japan, about 50 years after its construction. The geometric properties of the concrete matrix were calculated by the analysis of X-ray CT images. After X-ray CT measurement, an ultrasonic test and a resonant frequency test were performed. The dynamic modulus of elasticity was calculated by using ultrasonic pulse velocity and resonant frequency. As a result, based on the relationship between the geometric properties of the concrete matrix and the non-destructive parameters, the accumulation of damage in the samples tested was correlated with the ratio of the total area of cracks to the observation area. In damaged conditions, the high value of its ratio is demonstrated under low ultrasonic pulse velocity. These results suggest that the most sensitive components in a concrete body to the degree of damage are cracks in mortar and the ratio of the total area of cracks to the observation area. These values are affected by the internal actual cracks. Thus, the damage of concrete could be quantitatively evaluated by the geometric properties of the concrete matrix and its physical properties.

Characterization of a small-scale crystallizer using CFD simulations and X-ray CT measurements

• Single and multiphase CFD of a small-scale crystallizer with two stirrer types. • Indications when each stirrer is preferably used based on hydrodynamics. • X-ray CT applied in mixing studies used for the validation of the CFD simulations. Although small-scale crystallizers have gained increasing importance in recent years, their hydrodynamic properties have not yet been thoroughly studied. The purpose of this work is to characterize an intensively stirred small-scale crystallizer and to analyze whether its fluid mechanics behavior deviates from being homogeneously well-mixed. To this aim, single and multiphase computational fluid dynamics (CFD) simulations have been conducted. Two types of stirrers, including one overhead stirrer (OS) and one magnetic stirrer (MS), were compared. The single-phase CFD simulations showed that the mixing characteristics of the two stirrers differ significantly, thereby leading to variations in the distribution of solids. The MS is an axial flow type impeller, which is better at handling solid suspensions than the OS. The simulations were complemented by X-ray computed tomography measurements, which confirmed that spatial variations in solid distribution occur and that assuming a homogeneous suspension might lead to errors when modeling crystallization processes.

Deep learning based sinogram interpolation applied to X-ray CT measurements of polymer additive manufacturing parts

Large acquisition times are required to achieve high-quality XCT scans, because of the need for high exposure times and a large number of X-ray projections. Reducing the number of projections results in an increase in noise, artefacts in the reconstruction domain and measurement errors. To enhance those low-quality XCT scans, while keeping acquisition times low, we investigated the possibilities of deep learning sinogram interpolation, by using a conditional generative adversarial network (cGAN) to artificially increase the number of X-ray projections before reconstruction. The method is evaluated on simulated XCT scans from real objects using the ASTRA toolbox. First, the hyperparameters of the loss functions were altered to determine the optimal combination. Second, we experimented with different acquisition schemes and finally the number of X-ray projections is gradually reduced to quantify the minimum required X-ray projections and acquisition time.

X-Ray CT Measurement and Performance Evaluation of All Solid-State Lithium-Ion Battery with Sn Anode

Stannum (Sn) is investigated as a high-capacity anode for all-solid-state Lithium-Ion batteries. It is focused much attention because of its high theoretical capacity (990 mAh/g), which is much higher lithium storage capacity than that of graphite (372 mAh/g). However, poor cycling stability and coulombic efficiency hinder their practical use in Li-ion batteries. These drawbacks mainly result from the huge volume change of Sn (255% when 4.25 Li is inserted per a Sn), leading to a loss of electric contact, pulverization, and cracking. Therefore, it can be considered that there is a deep relationship between electrode structure and performance.In this study, to elucidate the relationship between electrode structure and performance of all-solid-state battery using Sn as the anode active material we compare the Sn anode with Sn weight ratio of 50wt% and 70wt%. The Sn anode structure is measured with in-situ X-ray CT measurement and the three-dimensional structure is compared to the electrode performance.To prepare the composite electrode, 5:5 and 7:3 (Sn : SE) weight ratio of Sn powder (38 um) and Li6PS5Cl were mixed by agate mortar and pestle. Anode half cells were then assembled and within 1 mm diameter polyetheretherketone (PEEK) cell dies at 400 MPa, and cells were cycled at a constant stress of 100 MPa In-situ X-ray CT with Molybdenum (Mo) target X-ray（nano3DX, Rigaku）was used to determine the structure of the composite electrode at a voxel size of 1.24 µm. And electrode performances were evaluated by potentiogalvanostat in the current of 0.05C.Figure 1 shows the X-ray CT images of the Sn anode with different Sn weight ratio ((a) 50 wt%, (b) 70 wt%). Sn regions are shown by blue and solid electrolyte (SE) regions are shown by yellow. Table.1 shows the electrode structure parameters calculated from the X-ray CT images shown in fig.1. The discharge capacity of Sn anode is dramatically increased by increasing in the Sn weight ratio (95 to 403 mAh/g). The tortuosity of SE network is increased with the increase in Sn weight ratio (1.43 to 2.15), which has a negative influence on the lithium-ion transportation in anode. It is considered that resistance of the SE network is increased with the increase of Sn weight ratio. Moreover, the contact specific surface area between SE and Sn is increased with the increase of Sn weight ratio (94.9×103 to 117×103 m2/m3). This increase of specific surface area of contact is corresponding to the decrease of interface resistance between SE and Sn in anode. The growth of discharge capacity can be derived from the decrease of interface resistance with the increase in specific surface area of contact between SE and Sn. Moreover, we also measured the expansion and contraction of the active material during charging and discharging, but the structural changes were not enough to explain the above performance differences.From the mentioned above, it can be said that as the Sn weight ratio increases, the resistance of the SE network is increased with the increase of tortuosity, but the interface resistance decreases due to the increase in the specific surface area of contact between SE and Sn, which leads to increase of electrode performance.This work is supported by JKA foundation (2020-1155). Figure 1

Rapid Freezing and Cryo CT Imaging of Liquid Water inside PEFCs

Liquid water in the gas diffusion layer (GDL) of polymer electrolyte fuel cells (PEFCs) prevents the gas transport and reduces the cell performance. Therefore, it is important to understand the actual structure of the liquid water in order to improve the GDL structure and the cell performance. X-ray measurement is one of the methods to understand the state of the liquid water inside the fuel cell. In the past, transmission imaging and in-situ computed tomography have been performed, but those methods provide spatial or temporal averaged images, and do not observe the actual instant three-dimensional structure. In this study, we observed the three-dimensional structure of the liquid water inside PEFCs by flash freezing and X-ray CT measurement. The operation was performed at 40 cell temperature. The relative humidity of the anode (H2)/cathode (air) gas was set at 80%, and the gas pressure was set at 101kPa. After rapid freezing using liquid nitrogen, CT imaging was performed in a low-temperature environment of -50. Figure(left) shows the liquid water structure on the cathode side at 0.1 V and 1.7 A/cm2. Liquid water accumulates widely inside the substrate, and it was also found to have a large structure connected between each neighborhood pores. Also, numerical simulations of oxygen transport were performed and showed that the accumulation of liquid water directly reduced the concentration of oxygen in the catalyst layer (right figure). Figure 1 Figure 2 Figure 3

Calibration of a Coil Array Geometry Using an X-Ray Computed Tomography

Sensor layout of biomagnetic measurement systems is measured using a multiple coil array that generates a magnetic signal. However, the results of the sensor array measurement included the error of the coil array because the coil array was not calibrated. In this paper, we proposed a calibration method to obtain the effective geometry and uncertainty of the coil array. The calibration was performed based on the X-ray CT measurements and numerical analysis of the position and shape of the coils. The differences between the designed and calibrated coil array geometries were 0.6 mm, 0.7°, and 0.3 mm with respect to the center position, orientation of the normal vector, and radius of the coils, respectively. The uncertainty of the calibration was 0.3 mm and 1.70 in terms of the dimension and orientation, respectively. We measured the sensor array layout of a magnetoencephalography (MEG) system using a calibrated coil array geometry. The source localization accuracy of the MEG system was improved compared with that of the sensor array layout obtained using the designed coil array geometry. We revealed the necessity of calibrating the coil array, regardless of the precision of the fabrication.

Passive Thermography Measurement of Damage Depth During Composites Load Testing

Passive thermography is commonly used for composites load testing to detect damage formation as a function of the applied load. The advantages of passive thermography are real time implementation, large area coverage, and noncontact measurement. Passive thermography is able to detect the damage location and size, however, damage depth has been a challenge for quasistatic loading. Recent work has shown that damage formation during loading produces heating that is composed of two heat generation components. The first component is an instantaneous thermal response due to an irreversible thermoelastic strain release due to rapid damage formation. The second component observed is mechanical heating, at the interface of failure, due to fracture damage that produces a transient rise in surface temperature as a function of damage depth. The first component defines the thermal start time for the transient response. A one-dimensional thermal model, that is independent of delamination damage gap spacing, is presented and fitted to the data pixel by pixel, to produce imagery of the damage depth. The percent difference between thermal results, as compared to the ultrasonic measurements of damage length and width, was on average 15%. The percent difference between the thermal results, as compared to the X-ray CT measurements for damage depth was on average 7%. This same processing technique was applied for detection of damage depth during cyclic loading as well.

Coupled nonlinear stress and electric field numerical simulation for all-solid-state lithium-ion batteries

An accurate analysis of ion transportation in an all-solid-state battery is crucial to improve and estimate performance. For an all-solid-state battery using sulfide solid electrolytes, coupling the stress and electric field simulations is required because the battery is pressurized, this affects the void space, which then affects ion transportation. In this paper, we propose a new method to analyze the ionic conductivity in a pressurized all-solid-state battery by coupling nonlinear stress analysis and electric field analysis. The nonlinear stress analysis can estimate the stress distribution of solid electrolyte and it was found that nonlinear stress-strain characteristics that originate from the voids diminished with increased pressure. The numerical results based on a model-electrode were nearly identical to the experimental results. • Numerical simulation method with nonlinear FEM and FVM are proposed. • Nonlinear mechanical characteristics of SE are simulated with nonlinear FEM. • The numerical results are validated with EIS and X-ray CT measurements. • The numerical and experimental results are in good agreement.