Synchrotron X-ray Nano-tomography Research Articles

Degradation study by 3D reconstruction of a nickel–yttria stabilized zirconia cathode after high temperature steam electrolysis operation

Microstructural evolution of a Solid Oxide Electrolyser Cell (SOEC) Ni–YSZ cermet cathode is investigated using three dimensional electrode characterisations. 3D reconstructions are obtained on a reference and two long-term tested cells, which were maintained at −0.5 and −0.8 A cm−2 for 1000 h at 800 °C. During the long term tests, air was fed at the anode and a mixture of 10% H2–90% H2O was fed at the cathode. In this framework, reconstructions have been obtained from synchrotron X-ray nano-tomography technique. Microstructural properties extracted from the 3D reconstructions exhibit an evolution during the tests. Triple Phase Boundary length is decreasing from 10.49 ± 1.18 μm−2 for the reference cell to 6.18 ± 0.6 μm−2 for the long term tested cell at −0.8 A cm−2. Evolutions of morphological parameters were introduced in an in-house multi-scale model to evaluate their impacts on the electrode degradation, and hence, on the global SOEC performance.

In Situ Three‐Dimensional Synchrotron X‐Ray Nanotomography of the (De)lithiation Processes in Tin Anodes

The three-dimensional quantitative analysis and nanometer-scale visualization of the microstructural evolutions of a tin electrode in a lithium-ion battery during cycling is described. Newly developed synchrotron X-ray nanotomography provided an invaluable tool. Severe microstructural changes occur during the first delithiation and the subsequent second lithiation, after which the particles reach a structural equilibrium with no further significant morphological changes. This reveals that initial delithiation and subsequent lithiation play a dominant role in the structural instability that yields mechanical degradation. This in situ 3D quantitative analysis and visualization of the microstructural evolution on the nanometer scale by synchrotron X-ray nanotomography should contribute to our understanding of energy materials and improve their synthetic processing.

X-ray nanotomography of a nanofiber: Quantitative measurement of diameter fluctuations

Imaging nanostructures in three-dimension is beneficial for understanding their formation and interactions. This paper presents application of X-ray imaging as a tool for visualizing the shape fluctuation in polymer nanofibers. Synchrotron X-ray nanotomography is a non-destructive technique that can reveal material internal and surface features at the nanoscale. Diameter fluctuations as a result of processing the polymer nanofiber obtained through forcespinning were imaged using monochromatic synchrotron hard X-rays of 8keV energy. Reconstructed binary images containing geometric information of the fiber surface were visualized and meshed in 3D. A new approach for processing of the reconstructed data to achieve a quantitative interpretation of 3D results was developed. A local 3D regression approach was developed for tracing the fiber center line, and to determine the minimum distance between triangular surface elements from the center line (radius). Fiber diameter fluctuations measured were presented qualitatively by applying surface coloring to the local fiber diameter information. Nanotomography revealed that the fiber has upto 19% (±43nm) deviation in fiber radius over the average radius of 221nm.

Degradation Study of the La0.6Sr0.4Co0.2Fe0.8O3 Solid Oxide Electrolysis Cell (SOEC) Anode after High Temperature Electrolysis Operation

Microstructural evolution of a Solid Oxide Electrolyser Cell (SOEC) La0.6Sr0.4Co0.2Fe0.8O3 (LSCF) anode is investigated using 3D reconstruction techniques both on a reference and a long-term tested cell. In this framework, reconstructions have been obtained from focused ion beam-scanning electron microscopy and synchrotron X-ray nano-tomography techniques. Microstructural properties extracted from the 3D reconstructions exhibit a slight evolution during the test. Synchrotron X-ray Absorption Spectroscopy (XAS) was also performed, and a modification of the cobalt oxidation state is found. LSCF conductivity decrease due to the change in Co mixed valence has been discussed. Evolutions of both morphological parameters and electrical conductivity were introduced in an in-house micro model to evaluate their impacts on the electrode degradation.

Synchrotron x-ray nano-tomography characterization of the sintering of multilayered systems

Synchrotron x-ray nano-tomography was used to characterize the microstructures of multi-layer ceramic capacitors before and after sintering. 3D microstructures of the same sample were reconstructed and quantitatively analyzed. The discontinuities observed in inner electrodes were found to originate from initial heterogeneities of nickel powders in the electrodes. They are supposed to grow due to the constraint of adjacent dielectric layers. Dielectric layers show anisotropic shrinkage with a decrease in density as function of layer position in the multilayer.

3D morphological evolution of Li-ion battery negative electrode LiVO2 during oxidation using X-ray nano-tomography

Lithium vanadium oxide (LiVO211More precisely, it is “Li1+xV1−xO2 (x>0)”. But “LiVO2” is used throughout the text for brevity [1].) holds the potential promise to replace graphite as an anode material in commercial Li-ion batteries as it doubles the volumetric energy density compared to graphite but can still operate at low voltage (~0.1V vs. Li/Li+). Its degradation mechanism was investigated using a synchrotron X-ray nano-tomography technique to image the LiVO2 in three dimensions (3D). In particular an oxidation effect is discussed by a direct visualization and quantification of the 3D microstructure of the LiVO2 before and after being exposed to the air, which results in the oxidation of the LiVO2. After being exposed to air, an oxidation layer with thickness ~120–240nm was observed at the interface of the LiVO2 particles and the binders/pores. While the total volume of LiVO2 remains relatively constant before and after oxidation, the particle size reduces, which is consistent with crack growth possibly due to the local exothermal oxidation reactions, accompanied by phase transition at an elevated temperature. The findings confirm the air-sensitivity of LiVO2 observed indirectly in the literature.

Characterisation of Solid Oxide Fuel Cell Ni–8YSZ substrate by synchrotron X-ray nano-tomography: from 3D reconstruction to microstructure quantification

A methodology, based on synchrotron X-ray nano-tomography measurements, is proposed to obtain 3D reconstructions of porous supports for Solid Oxide Fuel Cell (SOFC). The methodology has been applied to investigate the microstructure of a typical Ni–8YSZ cermet substrate of an Anode Supported Cell (ASC). Experimental conditions have been optimised so that a 3D reconstruction of 42 μm × 42 μm × 105 μm has been computed with a voxel size of 60 nm. The 3D reconstruction has been numerically analysed showing a quasi isotropy over the medium. A special attention has been paid to compute the morphological properties controlling the gas diffusion through the support. In this frame, it has been found that a volume as large as 35 μm × 35 μm × 35 μm is required to be statistically representative for the whole substrate. More particularly, the tortuosity factor τ has been calculated on the basis of finite element simulations. The effect of the boundary conditions taken for these simulations has been investigated. In the direction perpendicular to the anode/electrolyte interface, the tortuosity factor has been determined to τ z = 2.8 − 0.2 + 0.3 .