A Concept of Local Coordination Number for the Characterization of Solute Clusters within Atom Probe Tomography Data.

Identifying clusters of solute atoms in a matrix of solvent atoms helps to understand precipitation phenomena in alloys, for example, during the age hardening of certain aluminum alloys. Atom probe tomography datasets can deliver such information, provided that appropriate cluster identification routines are available. We investigate algorithms based on the local composition of the neighborhood of solute atoms and compare them with traditional approaches based on the local solute number density, such as the maximum separation distance method.

Tem-per-ature dependence in Bragg edge neutron transmission measurements.

A systematic study has been carried out to investigate the neutron transmission signal as a function of sample tem-per-ature. In particular, the experimentally de-ter-mined wavelength-dependent neutron attenuation spectra for a martensitic steel at tem-per-atures ranging from 21 to 700°C are com-pared with simulated data. A theoretical description that includes the Debye-Waller factor in order to describe the tem-per-ature influence on the neutron cross sections was im-plemented in the software and used for the simulations.

Tomoscopy: Time-Resolved Tomography for Dynamic Processes in Materials.

The structure and constitution of opaque materials can be studied with X-ray imaging methods such as 3D tomography. To observe the dynamic evolution of their structure and the distribution of constituents, for example, during processing, heating, mechanical loading, etc., 3D imaging has to be fast enough.

The Neutron Imaging Instrument CONRAD-Post-Operational Review.

The neutron imaging instrument CONRAD was operated as a part of the user program of the research reactor BER-II at Helmholtz-Zentrum Berlin (HZB) from 2005 to 2020. The instrument was designed to use the neutron flux from the cold source of the reactor, transported by a curved neutron guide. The pure cold neutron spectrum provided a great advantage in the use of different neutron optical components such as focusing lenses and guides, solid-state polarizers, monochromators and phase gratings.

Hardness data related to pre-ageing, natural secondary ageing, and paint bake hardening in Al-Mg-Si alloys.

The effect of pre-ageing (PA) time and temperature on subsequent natural secondary ageing (NSA) and paint bake (PB) hardening of an AA6014 Al-Mg-Si alloy was systematically investigated, especially when both parameters change. A wide range of PA conditions was covered with temperatures ranging from 80 °C to 160 °C and times from several minutes to several days depending on the PA temperature. Hardness data for such pre-treatments measured by Brinell method are given.

Using X-ray tomoscopy to explore the dynamics of foaming metal.

The complex flow of liquid metal in evolving metallic foams is still poorly understood due to difficulties in studying hot and opaque systems. We apply X-ray tomoscopy -the continuous acquisition of tomographic (3D) images- to clarify key dynamic phenomena in liquid aluminium foam such as nucleation and growth, bubble rearrangements, liquid retraction, coalescence and the rupture of films. Each phenomenon takes place on a typical timescale which we cover by obtaining 208 full tomograms per second over a period of up to one minute.

Simultaneous X-ray radioscopy/tomography and energy-dispersive diffraction applied to liquid aluminium alloy foams.

High-speed X-ray imaging in two dimensions (radioscopy) and three dimensions (tomography) is combined with fast X-ray diffraction in a new experimental setup at the synchrotron radiation source BESSY II. It allows for in situ studies of time-dependent phenomena in complex systems. As a first application, the foaming process of an aluminium alloy was studied in three different experiments.

In situ and Operando Tracking of Microstructure and Volume Evolution of Silicon Electrodes by using Synchrotron X-ray Imaging.

The internal microstructure of a silicon electrode in a lithium ion battery was visualized by operando synchrotron X-ray radioscopy during battery cycling. The silicon particles were found to change their sizes upon lithiation and delithiation and the changes could be quantified. It was found that volume change of a particle is related to its initial size and is also largely determined by the changing surrounding electron-conductive network and internal interface chemical environment (e.

Time-resolved in situ tomography for the analysis of evolving metal-foam granulates.

An experimental setup has been developed that allows for capturing up to 25 tomograms s using the white X-ray beam at the experimental station EDDI of BESSY II, Berlin, Germany. The key points are the use of a newly developed, precise and fast rotation stage, a very efficient scintillator and a fast CMOS camera. As a first application, the foaming of aluminium alloy granules at 923 K was investigated in situ.

An X-ray Tomographic Study of Rechargeable Zn/MnO₂ Batteries.

We present non-destructive and non-invasive in operando X-ray tomographic investigations of the charge and discharge behavior of rechargeable alkaline-manganese (RAM) batteries (Zn-MnO₂ batteries). Changes in the three-dimensional structure of the zinc anode and the MnO₂ cathode material after several charge/discharge cycles were analyzed. Battery discharge leads to a decrease in the zinc particle sizes, revealing a layer-by-layer dissolving behavior.

In Operando Quantification of Three-Dimensional Water Distribution in Nanoporous Carbon-Based Layers in Polymer Electrolyte Membrane Fuel Cells.

Understanding the function of nanoporous materials employed in polymer electrolyte membrane fuel cells (PEMFCs) is crucial to improve their performance, durability, and cost efficiency. Up to now, the water distribution in the nm-sized pore structures was hardly accessible during operation of the cells. Here we demonstrate that phase contrast synchrotron X-ray tomography allows for an in operando quantification of the three-dimensional water distribution within the nm-sized pores of carbon-based microporous layers (MPLs).

Morphological Evolution of Electrochemically Plated/Stripped Lithium Microstructures Investigated by Synchrotron X-ray Phase Contrast Tomography.

Due to its low redox potential and high theoretical specific capacity, Li metal has drawn worldwide research attention because of its potential use in next-generation battery technologies such as Li-S and Li-O2. Unfortunately, uncontrollable growth of Li microstructures (LmSs, e.g.

In Situ Radiographic Investigation of (De)Lithiation Mechanisms in a Tin-Electrode Lithium-Ion Battery.

The lithiation and delithiation mechanisms of multiple-Sn particles in a customized flat radiography cell were investigated by in situ synchrotron radiography. For the first time, four (de)lithiation phenomena in a Sn-electrode battery system are highlighted: 1) the (de)lithiation behavior varies between different Sn particles, 2) the time required to lithiate individual Sn particles is markedly different from the time needed to discharge the complete battery, 3) electrochemical deactivation of originally electrochemically active particles is reported, and 4) a change of electrochemical behavior of individual particles during cycling is found and explained by dynamic changes of (de)lithiation pathways amongst particles within the electrode. These unexpected findings fundamentaly expand the understanding of the underlying (de)lithiation mechanisms inside commercial lithium-ion batteries (LIBs) and would open new design principles for high-performance next-generation LIBs.

Three-Dimensional Visualization of Gas Evolution and Channel Formation inside a Lithium-Ion Battery.

Gas generation within lithium ion batteries (LIBs) gives rise to safety concerns that question their applicability. By employing synchrotron X-ray imaging, the gas and channel evolution occurring in an operating LIB have been directly visualized in their inherent 3D state as a function of discharge and charge. Using the spatial 3D distribution of gas bubbles and channels, the active particles that dictate the performance of a functional LIB were identified and visualized in 3D.

Slow crystallisation of a monodisperse foam stabilised against coarsening.

The evolution of a three-dimensional monodisperse foam was investigated using X-ray tomography over the course of seven days. The coarsening of the sample was inhibited through the use of perfluorohexane gas. The internal configuration of bubbles is seen to change markedly, evolving from a disordered arrangement towards a more ordered state.

3D mapping of crystallographic phase distribution using energy-selective neutron tomography.

Nondestructive 3D mapping of crystallographic phases is introduced providing distribution of phase fractions within the bulk (centimeter range) of samples with micrometer-scale resolution. The novel neutron tomography based technique overcomes critical limitations of existing techniques and offers a wide range of potential applications. It is demonstrated for steel samples exhibiting phase transformation after being subjected to tensile and torsional deformation.

Hierarchical radioscopy using polychromatic and partially coherent hard synchrotron radiation.

Pushing synchrotron x-ray radiography to increasingly higher image-acquisition rates (currently up to 100,000 fps) while maintaining spatial resolutions in the micrometer range implies drastically reduced fields of view. As a consequence, either imaging a small subregion of the sample with high spatial resolution or only the complete specimen with moderate resolution is applicable. We introduce a concept to overcome this limitation by making use of a semi-transparent x-ray detector positioned close to the investigated sample.

Mapping the evolution of hierarchical microstructures in a Ni-based superalloy.

Phase separation of γ' precipitates determines the microstructure and mechanical properties of nickel-based superalloys. In the course of ageing, disordered γ spheres form inside ordered (L12) γ' precipitates, undergo a morphological change to plates and finally split the γ' precipitates. The presence of γ particles inside γ' affects coarsening kinetics and increases alloy hardness.

Automated quantitative 3D analysis of faceting of particles in tomographic datasets.

Characterization of facets of particles is a common problem. In this paper an algorithm is presented which allows automated quantitative 3D analysis of facets of many particles within tomographic datasets. The algorithm is based on the analysis of probability distributions of the orientations of triangle normals of mesh representations.

Quantitative structural assessment of heterogeneous catalysts by electron tomography.

We present transmission electron microscope (TEM) tomography investigations of ruthenium-based fuel cell catalyst materials as employed in direct methanol fuel cells (DMFC). The digital three-dimensional representation of the samples not only enables detailed studies on number, size, and shape but also on the local orientation of the ruthenium particles to their support and their freely accessible surface area. The shape analysis shows the ruthenium particles deviate significantly from spherical symmetry which increases their surface to volume ratio.