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A systematic study has been carried out to investigate the neutron transmission signal as a function of sample temperature. In particular, the experimentally determined wavelength-dependent neutron attenuation spectra for a martensitic steel at temperatures ranging from 21 to 700°C are compared with simulated data. A theoretical description that includes the Debye–Waller factor in order to describe the temperature influence on the neutron cross sections was implemented in the nxsPlotter software and used for the simulations. The analysis of the attenuation coefficients at varying temperatures shows that the missing contributions due to elastic and inelastic scattering can be clearly distinguished: while the elastically scattered intensities decrease with higher temperatures, the inelastically scattered intensities increase, and the two can be separated from each other by analysing unique sharp features in the form of Bragg edges. This study presents the first systematic approach to quantify this effect and can serve as a basis , for example, to correct measurements taken during in situ heat treatments, in many cases being a prerequisite for obtaining quantifiable results.

The hard X ray beamline BAMline at BESSY II Berlin, Germany has now been in service for 20 amp; 8201;years. Several improvements have been implemented in this time, and this review provides an overview of the imaging methods available at the BAMline. Besides classic full field synchrotron X ray computed tomography SXCT , also absorption edge CT, synchrotron X ray refraction radiography SXRR , and synchrotron X ray refraction tomography SXRCT are used for imaging. Moreover, virtually any of those techniques are currently coupled in amp; 8201;situ or operando with ancillary equipment such as load rigs, furnaces, or potentiostats. Each of the available techniques is explained and both the current and the potential usage are described with corresponding examples. The potential use is manifold, the examples cover organic materials, composite materials, energy related materials, biological samples, and materials related to additive manufacturing. The article includes published examples as well as some unpublished applications

Herein, we present a detailed investigation of the electrochemically triggered formation and dissolution processes of α- and β-sulfur crystals on a monolithic carbon cathode using operando high-res...

An experimental in situ study was performed to investigate the effects of the catalyst layer (CL) and cathode microporous layer (MPLc ) perforation on the water management and performance of polymer electrolyte membrane fuel cells (PEMFCs). Polymeric pore formers were utilized to produce perforated CL and MPL structures. High-resolution neutron tomography was employed to visualize the liquid water content and distribution within different components of the cell under channel and land regions. The results revealed that at humid conditions, the perforated layers enhanced the liquid water transport under the channel regions. Moreover, at high current densities, the performance was improved for the cells with perforated layers compared to a baseline cell with non-perforated layers, owing to reduced mass transport losses.

To conduct simulations of transport properties within fuel cell materials 3D-data are required as input. For a functional simulation of flow and thermal characteristics the morphological features of the gas diffusion layer (GDL) materials must be well-defined. In this regard, the distribution of the distinct substances in the GDL, each of which is represented by a different parameter set, plays a decisive role. By means of synchrotron X-Ray computed tomography a fuel cell equipped with SGL® 28BC GDL material is recorded in 3D. The segmentation of the solid structural components and the identification of water agglomerations in the components are fulfilled by image processing techniques. This step is often realized using a lot of simplifications, like the reduction to only one or two different materials or idealized structural characteristics. In the presented work 8 different phases are defined according to the cell materials, which are the catalyst layer, the carbon fibers, the Teflon (PTFE)-binder, the micro porous layer (MPL), the flow field ribs, the pore spaces as well as the water in pore spaces of the GDL substrate and in the MPL. The image processing steps used for the classification of each voxel into these phases are described in detail in this work. Benefiting from this classification methodology, the macroscopic properties of the GDL materials such as water saturation, diffusivity, thermal and electrical conductivity can be obtained in simulations.

Metal foam flow-fields have shown great potential in improving the uniformity of reactant distribution in polymer electrolyte fuel cells (PEFCs) by eliminating the ‘land/channel’ geometry of conventional designs. However, a detailed understanding of the water management in operational metal foam flow-field based PEFCs is limited. This study aims to provide the first clear evidence of how and where water is generated, accumulated and removed in the metal foam flow-field based PEFCs using in-operando neutron radiography, and correlate the water ‘maps’ with electrochemical performance and durability. Results show that the metal foam flow-field based PEFC has greater tolerance to dehydration at 1000 mA cm−2, exhibiting a ~50% increase in voltage, ~127% increase in total water mass and ~38% decrease in high frequency resistance (HFR) than serpentine flow-field design. Additionally, the metal foam flow-field promotes more uniform water distribution where the standard deviation of the liquid water thickness distribution across the entire cell active area is almost half that of the serpentine. These superior characteristics of metal foam flow-field result in greater than twice the maximum power density over serpentine flow-field. Results suggest that optimizing fuel cell operating condition and foam microstructure would partly mitigate flooding in the metal foam flow-field based PEFC.

A large and increasing number of scientific domains pushes for high neutron imaging resolution achieved in reasonable times. Here we present the principle, design and performance of a detector based on infinity corrected optics combined with a crystalline Gd3Ga5O12 : Eu scintillator, which provides an isotropic sub-4 µm true resolution. The exposure times are only of a few minutes per image. This is made possible also by the uniquely intense cold neutron flux available at the imaging beamline NeXT-Grenoble. These comparatively rapid acquisitions are compatible with multiple high quality tomographic acquisitions, opening new venues for in-operando testing, as briefly exemplified here.

While laser powder-bed fusion has overcome some of the design constraints of conventional manufacturing meth-ods, it requires careful selection of process parameters and scan strategies to obtain favorable properties. Here we show that even simple scan strategies, complex ones being inevitable when printing intricate designs, can inadvertently produce local alterations of the microstructure and preferential grain orientation over small areas - which easily remain unnoticed across the macroscale. We describe how a combined usage of neutron imaging and electron backscatter diffraction can reveal these localized variations and explain their origin within cm-sized parts. We explain the observed contrast variations by linking the neutron images to simulated data, pole figures and EBSD, providing an invaluable reference for future studies and showing that presumably minor changes of the scan strategy can have detrimental effects on the mechanical properties. In-situ tensile tests reveal that fracture occurs in a region that was re-melted during the building process.

Advanced energy materials 13(2), 2203143 (2023). doi:10.1002/aenm.202203143, Copper sulfide shows some unique physico-chemical properties that make it appealing as a cathode active material (CAM) for solid-state batteries (SSBs). The most peculiar feature of the electrode reaction is the reversible formation of µm-sized Cu crystals during cycling, despite its large theoretical volume change (75%). Here, the dynamic microstructural evolution of CuS cathodes in SSBs is studied using in situ synchrotron X-ray tomography. The formation of µm-sized Cu within the CAM particles can be clearly followed. This process is accompanied by crack formation that can be prevented by increasing the stack pressure from 26 to 40 MPa. Both the Cu inclusions and cracks show a preferential orientation perpendicular to the cell stack pressure, which can be a result of a z-oriented expansion of the CAM particles during lithiation. In addition, cycling leads to a z-oriented reversible displacement of the cathode pellet, which is linked to the plating/stripping of the Li counter electrode. The pronounced structural changes cause pressure changes of up to 6 MPa within the cell, as determined by operando stack pressure measurements. Reasons for the reversibility of the electrode reaction are discussed and are attributed to the favorable combination of soft materials., Published by Wiley-VCH, Weinheim

Understanding the complicated interplay of the continuously evolving electrode materials in their inherent 3D states during the battery operating condition is of great importance for advancing rechargeable battery research. In this regard, the synchrotron X-ray tomography technique, which enables non-destructive, multi-scale, and 3D imaging of a variety of electrode components before/during/after battery operation, becomes an essential tool to deepen this understanding. The past few years have witnessed an increasingly growing interest in applying this technique in battery research. Hence, it is time to not only summarize the already obtained battery-related knowledge by using this technique, but also to present a fundamental elucidation of this technique to boost future studies in battery research. To this end, this review firstly introduces the fundamental principles and experimental setups of the synchrotron X-ray tomography technique. After that, a user guide to its application in battery research and examples of its applications in research of various types of batteries are presented. The current review ends with a discussion of the future opportunities of this technique for next-generation rechargeable batteries research. It is expected that this review can enhance the reader's understanding of the synchrotron X-ray tomography technique and stimulate new ideas and opportunities in battery research.

Inherently uncontrollable Li electrodeposition has significantly hindered the practical application of Li metal batteries largely due to a dendritic deposition which can initiate an internal short circuit and gives rise to severe safety issues. The understanding of the fundamental electrodeposition mechanism is, however, elusive and limited due to a lack of feasible in situ characterization techniques. Here synchrotron X-ray tomography was employed to noninvasively visualize Li deposition at the lithium/separator and lithium/carbon matrix interregion. A higher concentration of widely distributed deposition sites was observed under an increased current density. The 3D morphology and distribution of deposited Li within the widely used Celgard® 2325 polyolefin separator are, for the first time, visualized in situ, thus promoting the understanding of the short-circuiting process of Li metal batteries. In addition, we also visualized and quantified the spatial distribution of Li depositions inside a porous carbon host to unravel the deposition behavior that can hardly be probed by surface imaging techniques. The Li electrodeposition behavior found here could help to promote the understanding and development of surface modifications related to Li anodes, separators as well as novel 3D geometry electrode designs for accommodation of Li depositions and alleviation of volumetric changes.

The influence of porosity modification of both the cathode microporous layer (MPL) and catalyst layer (CL) of a low temperature polymer electrolyte membrane fuel cell (PEMFC) is studied with a neutron radiography technique to determine the water distribution and transport inside the cell. Three types of cathode MPLs with varying porosity distributions are made by introducing Chemisnow® monodisperse spherical polymer particles with 1.5 μm and 30 μm diameters inside the MPL slurry. CLs with three different porosities are manufactured by incorporation of 0 to 10 wt.% polystyrene particles with 0.5 μm diameters. Water thicknesses are measured inside the cell components at relative humidity of 120% with an increasing current density up to 1 A/cm². The results indicate that introducing micro pores into the structure of the MPL and CL may lead to the extraction of the excess water through these pores, leaving smaller pores accessible for the reaction gases and better cell performance.

An important step in the analysis of liquid water distributions in high resolution tomographies of PEMFCs is the segmentation of water and cell materials. This is conducted via subtraction of the dry from the operated state of the cells. The morphology of the gas diffusion layer (GDL) slightly changes due to membrane swelling at high humidification that makes quantification of water amounts hardly possible and leads to artifacts and false water detection. Here we present a computational algorithm identifying the changes in GDL morphology via local shift detection of the tomographic data sets that allows for an optimal quantification of water amounts. We compare the technique with typical global alignment methods. The results reveal huge errors in water quantification of up to 50% for the global alignment method that can be mostly avoided by using the presented technique. The morphology correction algorithm can basically be applied to many research fields, where operando measurements are important. This applies for a wide variety of materials employed in most types of fuel cells, electrolyzer cells, batteries and hydrogen storage systems.

In-depth understanding of water management is essential for the optimization of the performance and durability of polymer electrolyte fuel cells (PEFCs). Neutron imaging of liquid water has proven to be a powerful diagnostic technique, but it cannot distinguish between ‘legacy’ water that has accumulated in the system over time and ‘nascent’ water recently generated by reaction. Here, a novel technique is introduced to investigate the spatially resolved water exchange characteristics inside PEFCs. Hydro-electrochemical impedance imaging (HECII) involves making a small AC-sinusoidal perturbation to a cell and measuring the consequential water generated, using neutron radiographs, associated with the stimulus frequency. Subsequently, a least-squares estimation (LSE) analysis is applied to derive the spatial amplitude ratio and phase shift. This technique provides a complementary view to conventional neutron imaging and provides information on the source and ‘history’ of water in the system. By selecting a suitable perturbation frequency, HECII can be used to achieve an alternative image ‘contrast’ and identify different features involved in the water dynamics of operational fuel cells.

Hydrogen interaction with metals is well known to have severe detrimental effects on their mechanical properties. The use of modern high-strength steels, which are attractive to improve fuel economy by reducing weight as well as candidates for H storage cylinders and other components, is currently being severely limited by the fact that the presence of H can cause embrittlement of the material. In addition to steel, several other metals and alloys used in the nuclear industry, like Ti and Zr, are susceptible to H degradation through hydride formation and subsequent cracking. Microstructure-specific H mapping has been recognized as the most important challenge on the pathway towards a better understanding of the nature of H embrittlement in metallic alloys [1,2] as well as the development of H storage solutions based on metal hydrides [3]. Unfortunately, the characterization of H interactions with metals is an extremely challenging task and neutron-based techniques are of exceptional importance in this matter because - contrary to X-rays and electrons - thermal and cold neutrons interact strongly with the H nuclei [4], while the neutron beam is only weakly attenuated by the relevant metallic materials. Therefore, hydrogen distributions can be measured and quantified even in 3D by tomographic methods [5]. Here we present several neutron imaging investigations of embrittlement and cracking in Fe and Zr based metal alloys and optimization studies of hydrogen storage systems containing metal hydrides as an active substance. The advantages and the limitations of the experimental methods as well as the attempts for hydrogen quantification will be discussed in detail.

The gap between the successful application and perspective promise of lithium–oxygen battery (LOB) technology should be filled by an in-depth and comprehensive understanding of the underlying working and degradation mechanisms. Herein, the correlation between the morphological evolution of the Li anode and the overall cell electrochemical performance of cycled LOBs has been revealed for the first time by complementary X-ray and neutron tomography, together with further postmortem scanning electron microscopy, X-ray diffraction, and Fourier transfrom infrared spectroscopy characterizations. It has been disclosed with solid evidence that the irreversible transformation of anode Li associated with chemical/electrochemical side reactions does link intimately to the observed electrochemical performance decay. The current discoveries not only fundamentally enrich our knowledge of the underlying degradation and failure mechanisms of LOBs but also provide direction for future promising research activities aimed at further enhancing their performance.

Acta biomaterialia 136, 582 - 591 (2021). doi:10.1016/j.actbio.2021.09.047, Extensive research is being conducted on magnesium (Mg) alloys for bone implant manufacturing, due to their biocompatibility, biodegradability and mechanical properties. Gadolinium (Gd) is among the most promising alloying elements for property control in Mg alloy implants; however, its toxicity is controversial. Investigating Gd behavior during implant corrosion is thus of utmost importance. In this study, we analyzed the degradation byproducts at the implant site of biodegradable Mg-5Gd and Mg-10Gd implants after 12 weeks healing time, using a combination of different imaging techniques: histology, energy-dispersive x-ray spectroscopy (EDX), x-ray microcomputed tomography (��CT) and neutron ��CT. The main finding has been that, at the healing time in exam, the corrosion appears to have involved only the Mg component, which has been substituted by calcium and phosphorus, while the Gd remains localized at the implant site. This was observed in 2D by means of EDX maps and extended to 3D with a novel application of neutron tomography. X-ray fluorescence analysis of the main excretory organs also did not reveal any measurable accumulation of Gd, further reinforcing the conclusion that very limited or no removal at all of Gd-alloy happened during degradation., Published by Elsevier, [Amsterdam]

Electrochemical impedance spectroscopy (EIS) is a well-established method to analyze a polymer electrolyte membrane fuel cell (PEMFC). However, without further data processing, the impedance spectrum yields only qualitative insight into the mechanism and individual contribution of transport, kinetics, and ohmic losses to the overall fuel cell limitations. The distribution of relaxation times (DRT) method allows quantifying each of these polarization losses and evaluates their contribution to a given electrocatalyst's depreciated performances. We coupled this method with a detailed morphology study to investigate the impact of the 3D-structure on the processes occurring inside a high-temperature polymer electrolyte membrane fuel cell (HT-PEMFC). We tested a platinum catalyst (Pt/C), a platinum-cobalt alloy catalyst (Pt3Co/C), and a platinum group metal-free iron-nitrogen-carbon (Fe–N–C) catalyst. We found that the hampered mass transport in the latter is mainly responsible for its low performance in the MEA (along with its decreased intrinsic performances for the ORR reaction). The better performance of the alloy catalyst can be explained by both improved mass transport and a lower ORR resistance. Furthermore, single-cell tests show that the catalyst layer morphology influences the distribution of phosphoric acid during conditioning.

Herein, we present a detailed investigation of the electrochemically triggered formation and dissolution processes of α- and β-sulfur crystals on a monolithic carbon cathode using

The temporally and spatially resolved tracking of lithium intercalation and electrode degradation processes are crucial for detecting and understanding performance losses during the operation of lithium-batteries. Here, high-throughput X-ray computed tomography has enabled the identification of mechanical degradation processes in a commercial Li/MnO2 primary battery and the indirect tracking of lithium diffusion; furthermore, complementary neutron computed tomography has identified the direct lithium diffusion process and the electrode wetting by the electrolyte. Virtual electrode unrolling techniques provide a deeper view inside the electrode layers and are used to detect minor fluctuations which are difficult to observe using conventional three dimensional rendering tools. Moreover, the ‘unrolling’ provides a platform for correlating multi-modal image data which is expected to find wider application in battery science and engineering to study diverse effects e.g. electrode degradation or lithium diffusion blocking during battery cycling., The combination of X-ray and neutron CT enables 4D studies, i.e. to explore the evolution of 3D structures with time. Here the authors apply this approach to a Li-ion primary cell, revealing elsewhere unseen trends in the spatial distribution of performance aided by a new ‘unrolling’ methodology.

In various kinds of radiography, deficient transmission imaging may occur due to backlighting inside the detector itself arising from light or radiation scattering. The related intensity mismatches barely disturb the high resolution contrast, but its long range nature results in reduced attenuation levels which are often disregarded. Based on X-ray observations and an empirical formalism, a procedure is developed for a first order correction of detector backlighting. A backlighting factor is modeled as a function of the relative detector coverage by the sample projection. Different cases of sample transmission are regarded at different backlight factors and detector coverage. The additional intensity of backlighting may strongly affect the values of materials’ attenuation up to a few 10%. The presented scenario provides a comfortable procedure for corrections of X-ray or neutron transmission imaging data.

Although a great variety of strategies to suppress Li dendrite have been proposed for lithium metal batteries (LMBs), a deeper understanding of the factors playing a crucial role during extended el...

24th International Symposium on Metastable, Amorphous and Nanostructured Materials (ISMANAM), San Sebastian, SPAIN, JUN 18-23, 2017; The effect of impurities, Sr additions and cooling rate on the microstructural evolution of high-purity Al-10Si-0.3Fe and corresponding impure commercial alloys is examined by optical microscopy and in situ by X-ray synchrotron 3D tomography. At fast cooling rate (similar to 470 K min(-1)) the presence of impurities decreases the growth rate of primary Al dendrites and enables formation of the beta phase. Besides a modification of the eutectic Si, the addition of Sr prevents the formation of the beta phase and increases the growth rate of Al dendrites. A low cooling rate (similar to 1 K min(-1)) leads to the formation of alpha, gamma, delta and beta intermetallic phases. In all four alloys, the dominant phase is the delta phase, regardless of commercial impurities or the Sr level. Intermetallic phases formed during slow cooling rates are much coarser than those formed during fast cooling and they have different morphologies. Our results suggest that the velocity of growth and the final morphology and size of the intermetallic phases are mainly determined by diffusional processes which in turn are controlled by the cooling rate. (c) 2018 Elsevier B.V. All rights reserved.

The water management in proton exchange membrane fuel cells (PEMFC) is strongly influenced by the design of the gas diffusion layers (GDL). Limiting current measurements in small-scale cells operating at high stoichiometries are useful to determine the oxygen transport resistance. The oxygen transport resistance increases, once water condenses inside the GDL. In this study a new electrochemical method for voltage loss estimation of GDL induced oxygen transport losses are presented. This new method, referred to as “transient limiting current” (TLC), is compared with the literature method. TLC allows a direct estimation of oxygen transport resistance at an arbitrarily conditioned state. This study also presents a case study of liquid water visualization of a PEM fuel cell with varying GDLs types. With the help of quasi in-situ synchrotron X-ray computed tomography and time resolved radiography measurements we investigate appearance and distribution of liquid water inside the GDLs under limiting current conditions.

Knowing the distribution of a magnetic field in bulk materials is important for understanding basic phenomena and developing functional magnetic materials. Microscopic imaging techniques employing X-rays, light, electrons, or scanning probe methods have been used to quantify magnetic fields within planar thin magnetic films in 2D or magnetic vector fields within comparable thin volumes in 3D. Some years ago, neutron imaging has been demonstrated to be a unique tool to detect magnetic fields and magnetic domain structures within bulk materials. Here, we show how arbitrary magnetic vector fields within bulk materials can be visualized and quantified in 3D using a set of nine spin-polarized neutron imaging measurements and a novel tensorial multiplicative algebraic reconstruction technique (TMART). We first verify the method by measuring the known magnetic field of an electric coil and then investigate the unknown trapped magnetic flux within the type-I superconductor lead., Mapping the distribution of magnetic fields inside bulk materials is challenging but crucial to understand and develop functional magnetic materials. Here the authors demonstrate the capability to visualize 3D vector magnetic fields inside materials using spin-polarized neutron tomography and tensorial reconstruction techniques.

Liquid water saturation of pores in the gas diffusion layer (GDL) and the catalyst layer (CL) of polymer electrolyte membrane fuel cells (PEMFC) hinders the transport of the reactant gases, leading to inhomogeneous current density distribution, reduced overall cell performance, and accelerated material degradation. This effect restricts the PEMFC operation, specifically at high current densities. In this study, the simulation results illustrate how the interplay of wettability and pore sizes influences the water distribution within the CL, microporous layer (MPL) of the GDL, and specifically their interface. The liquid water distribution within the porous material is studied employing a voxel-based Monte Carlo (MC) model reflecting the effect of local thermodynamic boundary conditions and inner surface characteristics. Real material structures obtained with a focused ion beam - scanning electron microscope (FIB-SEM) are employed. Local temperature and relative humidity values required as inputs are obtained from sophisticated computational fluid dynamics (CFD) simulations comprising all relevant effects, including the electrochemical reactions. The results show that avoiding drastic changes in wettability at the CL-MPL interface can help to mitigate the possible detrimental water accumulations. Further developing and exploiting this study will contribute to facilitate the systematic material development for better PEMFC performance and durability.

It is well known that the microstructure of electrodes in lithium-ion batteries has an immense impact on their overall performance. The compaction load during the calendering process mainly determines the resulting morphology of the electrode. Therefore, NCM-based cathode films from uncompacted (0 MPa) to most highly compacted (1000 MPa) were manufactured, which corresponds to global porosities ranging from about 50% to 18%. All samples have been imaged using synchrotron tomography. These image data allow an extensive analysis of the 3D cathode microstructure with respect to increasing compaction. In addition, the numerous microstructural changes can be quantified using several characteristics describing the morphology of cathode samples. Three characteristics, namely global porosity, global volume fraction of active material and mean cathode thickness, are compared to experimental results. In addition, the microstructural analysis by means of 3D image data and image processing techniques allows the investigation of characteristics which are hard or impossible to ascertain by experiments, for example the continuous pore size distribution and the sphericity distribution of NCM-particles. Finally, the dependency of microstructural characteristics on compaction load is described by the help of parametric probability distributions. This approach can be used, for example, to predict the distribution of a certain characteristic for an 'unknown' compaction load, which is a valuable information with regard to the optimization and development process of NCM-cathodes in lithium-ion batteries. Lay description It is well known that the microstructure of electrodes in lithium-ion batteries has an immense impact on their overall performance. The manufacturing of the batteries includes the so-called calendering, where the electrodes are compressed with a certain pressure, which is called compaction load. This process step mainly determines the resulting morphology of the electrode and thus the properties of the battery. Therefore, eight cathodes with different compaction loads were manufactured and imaged by synchrotron tomography, which leads to 3D images containing detailed information about the inner structure of the cathode. This image data allows an extensive analysis of the 3D cathode microstructure with respect to increasing compaction. In order to quantify the microstructural changes we use several characteristics describing diverse properties of the morphology. Furthermore, the 3D image data can be used for the computation of characteristics which can not be determined by experiments. Therefore, 3D image data allows us to understand how the microstructure of cathodes is influenced by the compaction load. Finally, we are able to predict the distribution of a certain characteristic for arbitrary compaction loads. This information is valuable with regard to the development of improved lithium-ion batteries.

Tensile stress in selective laser melted (SLM) stainless steel 316 (SS316) bars was studied with neutron imaging methods for measurement of attenuation, scattering, and diffraction. The hypotheses for stress failure includes modifications to both the grain structure and residual porosity. Neutron Bragg edge imaging showed a change in crystallographic structure and/or texture at a pre-existing fracture, but did not provide evidence for presumptive crack formation. A Talbot-Lau grating-based neutron interferometer yielded better than 100 μm spatial resolution for the attenuation images and was tuned to an autocorrelation scattering length of 1.97 μm for the dark-field (scattering) images. The interferometry imaging was performed with samples parallel and perpendicular to the linear grating, allowing assessment of scattering along and perpendicular to the additive manufacturing build direction. In the 3D tomography dark-field volume of a tensile stressed bar, features were observed that suggested possible sites of crack formation. The features were quantified with line probes and found to be reproducible over three tomography experiments. After imaging, the half-stressed bar was pulled to failure; the fracture point is correlated with a feature in the line probe having enhanced neutron scattering. Neutron interferometry, particularly the dark-field imaging modality, emerges as a powerful non-destructive method for detecting early crack formation in additive manufactured components.

Neutron tomography is used to visualize the effect of hydrophobicity variations within the micro porous layer (MPL) and membrane electrode assembly (MEA) of a low-temperature polymer electrolyte fuel cell (PEMFC) on the detailed distribution of water in an operating cell. MEAs and MPLs manufactured in-house with different degrees of wettability are implemented in miniature fuel cells featuring an active area of 8 cm², which are specifically designed for neutron imaging experiments. The tomographies are obtained with a pixel size of 13 µm while maintaining the same operating conditions for all cells for comparability. The quantitative analysis of the water content in two of these cells next to the lands and the channels of the flow field is shown in Figure 1. It can be clearly observed that the implementation of a hydrophobic MEA significantly changes the overall water distribution within the cell. In contrast to the reference MEA, where more water is found in the catalyst layers compared to the membrane, the hydrophobic MEA has a higher water content inside its membrane. Implementing a GDL with a more hydrophobic MPL on the cathode side shows a higher water content inside the GDL substrate under the lands compared to the channels. This information can significantly help the optimization of material designs and can also provide valuable data for modeling and simulations of water distributions inside PEMFCs. We will show a detailed analysis of hydrophobicity changes on the water distribution inside the cell components, characterization results of various MPLs and MEAs regarding wettability and porosity analysis as well as performance results at different operating conditions Figure 1

Several pretreatment strategies focus on the removal of a significant part of lignin from plant cell walls, as it is considered the main barrier to the process of deconstructing biomass to simple sugars by hydrolytic enzymes. The ability to chemically differentiate and spatially locate lignins across cell walls provides an important contribution to the effort to improve these processes. Here, we present a novel approach using synchrotron phase-contrast tomography to probe the physicochemical features of plant cell walls. In addition to the 3D cellular architecture, the distribution of dense packed lignin–carbohydrate complexes (or, simply dense lignin) over larger regions and within cell walls has been successfully provided. We examined in particular the effect of the sequential H2SO4 and NaOH pretreatment on sugacane bagasse. Our results revealed that aggregates of dense lignin form elongated 3D structures in cell corners (CC) following the orientation of the sclerenchyma fibers; a remarkable result in the light of the conventional perception that lignin particles are discrete and roughly spherical. After the acid pretreatment, a considerable fraction of the dense lignin primarily located in CCs was removed; and it was further dissolved with the subsequent alkali treatment. Unexpectedly, the two-step pretreatment did not contribute to the cellulose accessibility in terms of available surface area and porosity. This study provides new insights into the underlying mechanisms of biomass deconstruction by pretreatments; and the approach established here can be extended to other systems relevant to the bioenergy and biotechnology arenas.

Efficient Li utilization is generally considered to be a prerequisite for developing next-generation energy storage systems (ESSs). However, uncontrolled growth of Li microstructures (LmSs) during electrochemical cycling has prevented its practical commercialization. Herein, we attempt to understand the correlation of morphological evolution of Li electrodes with degrading electrochemical performances of Li/LiCoO2 and Li/S systems by synchrotron X-ray phase contrast tomography technique. It was found that the continuous transformation of the initial dense Li bulk to a porous lithium interface (PLI) structure intimately correlates with the gradually degrading overall cell performance of these two systems. Additionally, the formation mechanism of the PLI and its correlation with previously reported inwardly growing LmS and the lithium-reacted region have been intensively discussed. The information that we gain herein is complementary to previous investigations and may provide general insights into understan...