Advanced Photon Source Beamline Research Articles

Characterizing Distribution and Morphology of ZnO Discharge Products in Commercial Alkaline Zn-MnO2 Batteries

During the discharge of alkaline Zn-MnO2 batteries, the dissolution of Zn particles in the anode saturate the electrolyte with zincate, prompting the formation of solid ZnO. Zincate is highly mobile in the electrolyte, giving rise to complex spatial distributions and morphologies of ZnO discharge products. The passivating behavior of ZnO is dependent on its distribution and morphology, as the active Zn particles within the anode must maintain a connection with the electronic network, while also having access to hydroxide ions from the electrolyte.1 Therefore, characterizing the factors that impact ZnO formation is critical to understanding how battery performance is impacted.2 Past attempts to model these batteries fail to adequately predict the behavior of Zn anodes under discharge conditions aimed at simulating real-world use cases.3 This work seeks to better characterize the behavior of Zn anodes in an effort to improve modeling capabilities based on experimental results.4 High resolution synchrotron CT was used to create in situ volumetric reconstructions of anodes from commercial AA and AAA batteries to determine ZnO morphology and radial distribution at various discharge conditions. Through a novel segmentation algorithm, quantitative data show a shift in ZnO radial distribution and microporosity depending on the rate and depth at which the anodes were discharged. High rate discharge leads to ZnO formation preferentially near the separator with a lower microporosity, increasing its passivating characteristics. Microporosity calculations show the discharge products form in two types, namely type I ZnO and ZnO hydrate. The latter type had only ever been reported on planar electrodes, yet it has a significant presence in commercial alkaline batteries discharged under certain conditions.4,5 In addition to a decreased microporosity, the morphology of ZnO also showed increased passivating characteristics when discharging using a continuous protocol. Shells of ZnO form around undischarged Zn cores during a continuous discharge, restricting hydroxide transport to the Zn surface and potentially isolating the core from the electronically conductive Zn network. When using a pulsed discharge protocol, ZnO formed distributed regions of microporous ZnO not adhered to undischarged Zn surfaces, leaving the remaining Zn in good contact with the electrolyte. Developing a more robust understanding of the factors that impact ZnO formation will enable more advanced models to be created. Acknowledgements This research was supported by funding from Energizer Holdings, Inc. We acknowledge collaborators Xiaotong Chadderdon, Matthew Wendling, Andrew Chihpin Chuang, and John Okasinski. This research also used resources of the Advanced Photon Source beamline 6-BM, a U.S. Department of Energy (DOE) Office of Science User Facility operated for the DOE Office of Science by Argonne National Laboratory under Contract No. DE-AC02-06CH11357.

Operando Measurement of Lithiation Gradients in NMC111-Argyrodite All-Solid-State Composite Cathodes

Achieving the high energy density targets in all-solid-state batteries (ASSBs) will require thick cathodes optimized for full utilization of active material. In composite cathodes with sulfide SSEs, the exclusion of carbon additives makes cathode design to balance ionic and electronic conductivities all the more important. Li-Ni1/3Mn1/3Co1/3O2 (NMC111) is a widely studied cathode material for its high energy density and high working voltage. The lattice parameters of this well-studied structure directly correlate to the amount of Li in the material, allowing for very accurate measurements of lithium-ion concentration gradients (lithiation gradients) throughout the cathode depth.Spatially resolved lithiation gradients in thick NMC111/ Li6PS5Cl composite cathodes were measured using operando energy dispersive X-ray diffraction (EDXRD) on sealed and pressurized ASSBs with varying relative amounts of cathode active mass (CAM) and SSE. Electrochemical impedance spectroscopy (EIS) and transmission line modeling were employed to test the ionic and electronic conductivities of composite cathodes with similar varied CAM and SSE ratios. The balance of ionic and electronic conductivities was found to influence not only the lithiation gradients and utilization of active material in the cell, but also the NMC structural change throughout the depth of the cell resulting in peak bifurcation in the NMC (003) diffraction pattern.Sulfide ASSBs suffer from a large capacity loss on the first cycle due to formation of the cathode electrolyte interface (CEI). To study this interface formation and capacity loss, in situ EIS was performed during the first charge and discharge of the full cell (Li/In| Li6PS5Cl| NMC111/Li6PS5Cl). This piecewise EIS allows us to analyze both time dependent and state-of-charge dependent interfacial processes while the battery cycles with no modifications to cell design. Acknowledgments We acknowledge financial support from the National Science Foundation under Award Number CBET-ES- 1924534. This research used resources of the Advanced Photon Source beamline 6-BM, a U.S. Department of Energy (DOE) Office of Science User Facility operated for the DOE Office of Science by Argonne National Laboratory under Contract No. DE-AC02-06CH11357.

Li-Ion and Na-Ion Intercalation in Layered MnO2 Cathodes Enabled by Using Bismuth as a Cation Pillar

Rechargeability of low-cost MnO2 cathodes in aqueous cells has the potential to be an enabling technology for low-cost (<$50/kWh) grid-scale batteries. This rechargeability is imparted by modifying the MnO2 with Bi. In this talk we detail using Bi doping for structural stabilization of MnO2 cathodes for Li-ion and Na-ion batteries in dry, non-aqueous electrolyte. We do this by preparing a series of Bi-doped layered MnO2 compounds, which also contain K ions and crystal water. These phyllomanganates or birnessite-type compounds have the general formula KxBiy-MnO2 • nH2O. The materials are structurally characterized by synchrotron X-ray powder diffraction (XPD) and confocal Raman microscopy. It is found that incorporation of Bi in the structure increases the crystallinity of the material by ordering the interlayer cations. This ordering results in the emergence of a structural superlattice in the material, which has been reported previously for birnessite inserted with other heavy, multivalent cations such as as Sr2+, Ba2+, and Ca2+.We selected three Bi doping levels to study in Li-ion and Na-ion batteries: undoped (y = 0), low-doping (y = 0.013 or 1.3%), and high doping (y = 0.043 or 4.3%). Both doped materials had capacity over 200 mAh/g and allowed for far more stable cell cycling than the undoped Kx-MnO2. The cells made with 4.3% doping of Bi were by far more stable. These cycled at 175-190 mAh/g specific capacity through 100 cycles with a nominal voltage of 2.9 V. Operando XRD experiments to characterize the cathodes within sealed coin cells showed that high-level doping (4.3%) promoted dehydration of the KxBiy-MnO2 interlayer, which had a distance of 6.4 Å. This showed that loss of the crystal water from the interlayer was key to achieving maximum stability during cycling. Lower Bi doping (1.3%) did not cause loss of the crystal water once the cathode was wetted with electrolyte. Previous reports have suggested that Bi doping of 20% results in stabilized Li-ion cycling in layered MnO2. However, these reports involved largely amorphous active material. Our results showed that Bi doping of only 1.3% still provided a large stability benefit, and the high crystallinity of our material allowed it to be structurally characterized, both in the as-prepared state and operando during battery cycling. Results from Na-ion cells will also be presented.Stabilized MnO2-based cathodes that cycle with good capacity and somewhat lower cell voltage than traditional Li-ion cells are a promising strategy for low-cost batteries for the grid. The possibility of using Na as the working ion is also useful for large-scale deployment of batteries to balance renewable power. Acknowledgments This work was supported by the U.S. Department of Energy (DOE) Office of Electricity Delivery and Energy Reliability, Dr. Imre Gyuk, Energy Storage Program Manager. This research used resources of the Advanced Photon Source beamline 6-BM, a U.S. Department of Energy (DOE) Office of Science User Facility operated for the DOE Office of Science by Argonne National Laboratory under Contract No. DE-AC02-06CH11357. This research also used resources at beamlines 7-BM (QAS) and 28-ID-2 (XPD) of the National Synchrotron Light Source II, a U.S. Department of Energy (DOE) Office of Science User Facility operated for the DOE Office of Science by Brookhaven National Laboratory under Contract No. DE-SC0012704.

Density and Volume Fraction Distribution of ZnO Discharge Products in Cylindrical Alkaline Battery Anodes after Intermittent Use

The discharge of an alkaline Zn anode involves the conversion of active material to aqueous zincate ions and solid ZnO. With the mobility of zincate in the electrolyte, complex ZnO morphologies and radial distributions have been observed to occur when using different discharge protocols. An apparent continuum of ZnO densities can be seen in an intermittently discharged anode, and can be appropriately binned into two forms, namely type I and type II, which differ in density and passivating character.1 Not only are the relative amounts of these two types impacted by the discharge protocol, but their morphologies and volume distributions are also affected. This has implications for both primary cells, where undesirable ZnO formation near the separator can lead to cell failure, and secondary cells, where redistribution of active material inhibits cyclability. Previously reported models of Zn anodes poorly describe the behavior seen when using an intermittent discharge protocol meant to simulate typical real-world applications, and therefore require further development.2 Additionally, prior literature reported that ZnO forms passivating shells around undischarged Zn cores, restricting hydroxide transport, and thus resulting in reduced cell performance.3 In this work, we characterize the ZnO morphology and radial distribution for an array of discharge conditions that simulate both intermittent and continuous use. We then use these results to identify the impact of discharge protocol on ZnO formation within alkaline Zn anodes.This work paired high resolution synchrotron tomography with a novel segmentation algorithm to observe phase morphology and quantify radial distributions in situ. The results obtained when using a continuous discharge protocol matched that of previous literature.3 However, the results when using an intermittent discharge protocol were vastly different than that seen with a continuous protocol. The discharge products in a cell simulating intermittent use formed two distinct phases of varying densities, both of which preferentially formed in the inner portion of the anode. This is radically different than ZnO formation in continuously discharged cells, wherein an apparent single ZnO phase is concentrated at the outer portions of the anode near the separator, creating a dense crust around the remaining Zn. This outer crust can be detrimental to cell performance due to poor hydroxide transport from the cathode to the remaining undischarged Zn, suggesting superior cell performance with intermittent use. Acknowledgements This research was supported by funding from Energizer Holdings, Inc. This research also used resources of the Advanced Photon Source beamline 6-BM, a U.S. Department of Energy (DOE) Office of Science User Facility operated for the DOE Office of Science by Argonne National Laboratory under Contract No. DE-AC02-06CH11357.

Wire-coil insert optimization for high-heat-load/flux synchrotron components

Many synchrotron components require high levels of internal-flow, forced-convection heat transfer to minimize surface temperatures, thermal gradients, and thermally induced stress on high-power beam-interacting surfaces. Wire-coil inserts, physically similar to a common spring, are mechanically fitted inside of component cooling passages to optimize heat transfer performance. They are routinely used in Advanced Photon Source (APS) front end and beamline high-heat-load/flux components to significantly enhance convection heat transfer—up to 400% compared to plain open passages. This has the additional benefit of greatly reducing coolant flow requirements for these components. Using several cooling passage sizes, five different wire sizes, and a range of pitch values, an experimental investigation conducted at the APS has determined the average heat transfer coefficient and resulting pressure loss as a function of water flow rate for 65 different wire-coil inserts. Data from this study have been non-dimensionalized and generalized to yield relationships that can be used to determine the heat transfer performance and resulting pressure loss for any given wire-coil insert that may be used at the APS. Through data reduction, the wire-coil insert characteristic dimensions have also been optimized to yield the highest heat transfer enhancement while minimizing the coolant flow requirements. These generalized expressions for wire-coil inserts will be presented, and they can be used by scientists and engineers during the component design process to evaluate achievable heat transfer performance and associated pressure loss, aiding in the establishment of optimized operating parameters and cooling passage flow distribution schemes.

3D In-situ Stop Action Study of Recrystallization in Additively Manufactured 316L Stainless Steel: Reconstruction Optimization and Observations

A volume of an additively manufactured 316L stainless steel sample has been tracked during its recrystallization using near- and far-field High Energy Diffraction Microscopy (HEDM) and absorption tomography at Advanced Photon Source beamline 1-ID. A near-field compatible in situ furnace allows monitoring of Bragg diffraction signals as they evolve out of a weak and diffuse background while the sample temperature is ≈ 1250° C. The sample is rapidly cooled to room temperature after observation of significant signal evolution and ∼ 0.035 mm3 is mapped by the near-field method. Four cycles of heat treatment follow the structure from a state of small, isolated grains through impingement of domains to near completion of recyrstallization. Here, the experiment and reconstructions are described, and recrystallized fractions, twin domains, and distributions of grain boundary types are discussed.

Deep learning approaches to semantic segmentation of fatigue cracking within cyclically loaded nickel superalloy

Improvements to synchrotron-based micro-computed tomography scanning capabilities have gifted researchers the ability to characterize 4D material thermomechanical responses more thoroughly than ever before. These advancements, however, have brought about new challenges in analyzing the resulting deluge of data. We report on a nickel-based superalloy specimen imaged 26 times in-situ during cyclic loading at Argonne National Laboratory Advanced Photon Source beamline 1ID, in order to monitor crack growth within the microstructure. Several deep learning approaches which utilize convolutional neural networks are implemented to segment crack features from reconstructed tomography scans. U-Net architecture implementations are found to be especially effective, achieving IoU=0.995±0.004 and Matthews correlation coefficient scores of ϕ=0.826±0.085. These advancements broaden possibilities for scientists seeking to automate segmentation analyses of similar large datasets.

Hard X-ray Fluorescence measurements with TESs at the Advanced Photon Source

Transition Edge Sensor (TES) spectrometers for hard X-ray beamline science will enable improved X-ray emission and absorption spectroscopy in the information-rich 2 to 20 keV energy range. We are building a TES-based instrument for the Advanced Photon Source (APS) synchrotron, to be made available to beamline users. 24-pixel prototype arrays have recently been fabricated and tested. The first spectroscopy measurements using these arrays are promising, with a best single-pixel energy resolution of 11.2 eV and saturation energy > 20 keV. We present a series of recent X-ray Fluorescence measurements involving transition metal elements and multi-element samples with closely spaced emission lines, in particular a Cu-Ni-Co thin film and a foil of Cu and Hf. The TES-measured spectra are directly compared to spectra measured with silicon drift detectors at an APS beamline, demonstrating the improved X-ray science made possible by TES spectrometers.

Evaluation of contact angle between asphalt binders and aggregates using Molecular Dynamics (MD) method

Abstract The objectives of this study are to explore the mechanism of the self-healing or flow of asphalt binder on the surface of the aggregates and evaluate the contact angle between the asphalt binder and aggregates. The mastic samples (small size) were prepared with asphalt binder and fine aggregates of a small size (below 0.3 mm). The microscale dynamic X-ray tomography was used to observe the flow of asphalt binder in the mastic sample at 353.15 K (80 °C) using the Advanced Photon Source (APS) beamline 2-BM at Argonne National Laboratory. The activation energy for flow of the asphalt binder and the contact angle between the asphalt binder and aggregates were analyzed to explain the self-healing characteristics of the asphalt binder materials. The Molecular Dynamics (MD) method was employed to simulate the flow process of the molecules of asphalt binder at different temperatures and mimic the contact angle difference between the asphalt binder and aggregate models. Simultaneously, in the laboratory, the contact angle goniometer was selected to measure the contact angle between the asphalt binder droplet and aggregates at different temperatures. The results of tests and MD simulations show that (1) asphalt binder diffused after heating from the X-ray images, and the stages and mechanism of the flow process of asphalt binder on aggregates were investigated; (2) low contact angle was observed in the interface model of asphalt binder and aggregates at high temperatures using the MD method. The wetting condition changed from partial non-wetting to wetting after heating in the interface model; (3) contact angle results between the asphalt binder and aggregates demonstrated flow steps of the asphalt binder material. The test data was also compared with the MD simulation results at different temperatures.

Quantifying X-Ray Fluorescence Data Using MAPS.

The quantification of X-ray fluorescence (XRF) microscopy maps by fitting the raw spectra to a known standard is crucial for evaluating chemical composition and elemental distribution within a material. Synchrotron-based XRF has become an integral characterization technique for a variety of research topics, particularly due to its non-destructive nature and its high sensitivity. Today, synchrotrons can acquire fluorescence data at spatial resolutions well below a micron, allowing for the evaluation of compositional variations at the nanoscale. Through proper quantification, it is then possible to obtain an in-depth, high-resolution understanding of elemental segregation, stoichiometric relationships, and clustering behavior. This article explains how to use the MAPS fitting software developed by Argonne National Laboratory for the quantification of full 2-D XRF maps. We use as an example results from a Cu(In,Ga)Se2 solar cell, taken at the Advanced Photon Source beamline 2-ID-D at Argonne National Laboratory. We show the standard procedure for fitting raw data, demonstrate how to evaluate the quality of a fit and present the typical outputs generated by the program. In addition, we discuss in this manuscript certain software limitations and offer suggestions for how to further correct the data to be numerically accurate and representative of spatially resolved, elemental concentrations.

Quantifying X-Ray Fluorescence Data Using MAPS

The quantification of X-ray fluorescence (XRF) microscopy maps by fitting the raw spectra to a known standard is crucial for evaluating chemical composition and elemental distribution within a material. Synchrotron-based XRF has become an integral characterization technique for a variety of research topics, particularly due to its non-destructive nature and its high sensitivity. Today, synchrotrons can acquire fluorescence data at spatial resolutions well below a micron, allowing for the evaluation of compositional variations at the nanoscale. Through proper quantification, it is then possible to obtain an in-depth, high-resolution understanding of elemental segregation, stoichiometric relationships, and clustering behavior. This article explains how to use the MAPS fitting software developed by Argonne National Laboratory for the quantification of full 2-D XRF maps. We use as an example results from a Cu(In,Ga)Se2 solar cell, taken at the Advanced Photon Source beamline 2-ID-D at Argonne National Laboratory. We show the standard procedure for fitting raw data, demonstrate how to evaluate the quality of a fit and present the typical outputs generated by the program. In addition, we discuss in this manuscript certain software limitations and offer suggestions for how to further correct the data to be numerically accurate and representative of spatially resolved, elemental concentrations.

Catalyst Dissolution Rates during PEM Fuel Cell Operation

Improved catalyst performance and durability are critical to the successful deployment of proton exchange membrane fuel cells (PEMFCs) in automotive applications. In recent years advances have been made in developing highly active Pt-alloy (e.g PtCo, PtNi etc.) catalysts that have specific activity 5-10 times higher than state-of- art Pt catalysts. Dealloyed catalysts, PtCo and PtNi in particular, are interesting cathode catalyst candidates due to their high activity for oxygen reduction reaction (ORR) and relatively high stability.1,2 Even though the catalyst has experienced extensive oxidative treatment during the catalyst synthesis and break-in procedure, the dissolution process continues under fuel cell operating conditions due to exposure to an acidic environment and high electrode potentials. This results in the transition metal of the platinum alloy dissolving into the electrolyte phase. In turn, this causes losses in catalytic activity and subsequent reductions in proton, water and O2transport properties of the fuel cell electrodes. Due to these durability issues, high activity at Beginning of Life (BOL) can be compromised during operation. This talk will outline the quantitative understanding of the Pt and Co dissolution of PtCo electrodes under both simulated and actual fuel cell operating conditions. Studies were performed to quantify the amount of leached Co and Pt ions during potentiostatic (Figure 1) and potentiodynamic (Figure 2) conditions in an electrochemical cell with aqueous acid electrolyte. The amount of metal ions released into the solution were monitored with on-line ICP-MS in a flow-through an electrochemical cell and using ICP on the solution samples that were extracted during the cycling. While the amount of Pt dissolved during voltage cycling has been well studied, the impact of potential cycling on Co leaching is not well understood. Initial measurements show that the amount of Co leached is a strong function of upper potential limit (UPL) and less impacted by the lower potential limits (LPL) (Figure 2), however Pt dissolved is a strong function of both UPL and LPL. In addition to quantifying leached Pt and Co, changes in the particle characteristics and metal compositions of the particles were also quantified using SAXS3and STEM analysis. Voltage cycling was also performed in an MEA environment with DOE protocol recommended for catalyst stability. Changes in activity and performance during cycling was tracked, and post-mortem analysis of the cycled samples was performed to determine changes in particle characteristics. Fundamental models were developed to explain the mechanisms of the degradation process under potential cycling. Models show that the dissolution process is strongly related to the type and growth of Pt oxides4on the catalysts. The dissolution rates are correlated to activity changes during the fuel cell operation. Using the rate parameters determined from ex-situ dissolution studies, degradation rates in an MEA that underwent DOE voltage cycling can be estimated. This work was partially supported by the U.S. Department of Energy, Office of Energy Efficiency and Renewable Energy under grant DE-EE0007271. This research used resources of the Advanced Photon Source (beamline 9ID) at Argonne National Laboratory under Contract No. DE-AC02-06CH11357.

Investigation of the asphalt–aggregate interaction using molecular dynamics

ABSTRACTThe objective of this study is to explore the self-healing process or diffusion of the asphalt materials on aggregates through the experiments and molecular dynamics (MD) simulations. The asphalt mastic samples were prepared with binders and fine aggregates. The microscale dynamic X-ray computed tomography was conducted to capture the self-diffusion process of the binder in the asphalt mastic controlled at 353.15 K using Advanced Photon Source beamline 2-BM. The Mean Square Displacements were analyzed to describe the self-healing behaviors of binders by an MD method. The results of tests and MD simulations show that the molecules of the asphalt model on the nanoscale at high temperatures move faster those at low temperatures. The asphalt molecules move forward to aggregate layer and expand contact area to reduce the system energy.

Correlation of Thermally Induced Pores with Microstructural Features Using High Energy X-rays

Combined application of a near-field High Energy Diffraction Microscopy measurement of crystal lattice orientation fields and a tomographic measurement of pore distributions in a sintered nickel-based superalloy sample allows pore locations to be correlated with microstructural features. Measurements were carried out at the Advanced Photon Source beamline 1-ID using an X-ray energy of 65 keV for each of the measurement modes. The nickel superalloy sample was prepared in such a way as to generate significant thermally induced porosity. A three-dimensionally resolved orientation map is directly overlaid with the tomographically determined pore map through a careful registration procedure. The data are shown to reliably reproduce the expected correlations between specific microstructural features (triple lines and quadruple nodes) and pore positions. With the statistics afforded by the 3D data set, we conclude that within statistical limits, pore formation does not depend on the relative orientations of the grains. The experimental procedures and analysis tools illustrated are being applied to a variety of materials problems in which local heterogeneities can affect materials properties.

Compressional behavior of omphacite to 47 GPa

Omphacite is an important mineral component of eclogite. Single-crystal synchrotron X-ray diffraction data on natural (Ca, Na) (Mg, Fe, Al)Si2O6 omphacite have been collected at the Advanced Photon Source beamlines 13-BM-C and 13-ID-D up to 47 GPa at ambient temperature. Unit cell parameter and crystal structure refinements were carried out to constrain the isothermal equation of state and compression mechanism. The third-order Birch–Murnaghan equation of state (BM3) fit of all data gives V 0 = 423.9(3) A3, K T0 = 116(2) GPa and K T0′ = 4.3(2). These elastic parameters are consistent with the general trend of the diopside–jadeite join. The eight-coordinated polyhedra (M2 and M21) are the most compressible and contribute to majority of the unit cell compression, while the SiO4 tetrahedra (Si1 and Si2) behave as rigid structural units and are the most incompressible. Axial compressibilities are determined by fitting linearized BM3 equation of state to pressure dependences of unit cell parameters. Throughout the investigated pressure range, the b-axis is more compressible than the c-axis. The axial compressibility of the a-axis is the largest among the three axes at 0 GPa, yet it quickly drops to the smallest at pressures above 5 GPa, which is explained by the rotation of the stiffest major compression axis toward the a-axis with the increase in pressure.

Development and implementation of a portable grating interferometer system as a standard tool for testing optics at the Advanced Photon Source beamline 1-BM.

We developed a portable X-ray grating interferometer setup as a standard tool for testing optics at the Advanced Photon Source (APS) beamline 1-BM. The interferometer can be operated in phase-stepping, Moiré, or single-grating harmonic imaging mode with 1-D or 2-D gratings. All of the interferometer motions are motorized; hence, it is much easier and quicker to switch between the different modes of operation. A novel aspect of this new instrument is its designed portability. While the setup is designed to be primarily used as a standard tool for testing optics at 1-BM, it could be potentially deployed at other APS beamlines for beam coherence and wavefront characterization or imaging. The design of the interferometer system is described in detail and coherence measurements obtained at the APS 34-ID-E beamline are presented. The coherence was probed in two directions using a 2-D checkerboard, a linear, and a circular grating at X-ray energies of 8 keV, 11 keV, and 18 keV.

On the influence of monochromator thermal deformations on X-ray focusing

A cooled double crystal monochromator system is used on many high heat load X-ray synchrotron radiation beamlines in order to select, by diffraction, a narrow spectrum of the beam. Thermal deformation of the first crystal monochromator – and the potential loss of beam brightness – is often a concern. However, if downstream beam focusing is planned, the lensing effect of the monochromator must be considered even if thermal deformations are small. In this paper we report on recent experiments at an Advanced Photon Source (APS) beamline that focuses the X-ray beam using compound refractive lenses downstream of an X-ray monochromator system. Increasing the X-ray beam power by increasing the storage ring current from 100mA to 130mA resulted in an effective doubling of the focal distance. We show quantitatively that this is due to a lensing effect of the distorted monochromator that results in the creation of a virtual source downstream of the actual source. An analysis of the defocusing and options to mitigate this effect are explored.

Transient x-ray diffraction with simultaneous imaging under high strain-rate loading.

Real time, in situ, multiframe, diffraction, and imaging measurements on bulk samples under high and ultrahigh strain-rate loading are highly desirable for micro- and mesoscale sciences. We present an experimental demonstration of multiframe transient x-ray diffraction (TXD) along with simultaneous imaging under high strain-rate loading at the Advanced Photon Source beamline 32ID. The feasibility study utilizes high strain-rate Hopkinson bar loading on a Mg alloy. The exposure time in TXD is 2-3 μs, and the frame interval is 26.7-62.5 μs. Various dynamic deformation mechanisms are revealed by TXD, including lattice expansion or compression, crystal plasticity, grain or lattice rotation, and likely grain refinement, as well as considerable anisotropy in deformation. Dynamic strain fields are mapped via x-ray digital image correlation, and are consistent with the diffraction measurements and loading histories.

Note: Dynamic strain field mapping with synchrotron X-ray digital image correlation.

We present a dynamic strain field mapping method based on synchrotron X-ray digital image correlation (XDIC). Synchrotron X-ray sources are advantageous for imaging with exceptional spatial and temporal resolutions, and X-ray speckles can be produced either from surface roughness or internal inhomogeneities. Combining speckled X-ray imaging with DIC allows one to map strain fields with high resolutions. Based on experiments on void growth in Al and deformation of a granular material during Kolsky bar/gas gun loading at the Advanced Photon Source beamline 32ID, we demonstrate the feasibility of dynamic XDIC. XDIC is particularly useful for dynamic, in-volume, measurements on opaque materials under high strain-rate, large, deformation.

Lithographically-fabricated channel arrays for confocal x-ray fluorescence microscopy and XAFS

Confocal X-ray Fluorescence Microscopy (CXRF) employs overlapping focal regions of two x-ray optics—a condenser and collector—to directly probe a 3D volume. The minimum-achievable size of this probe volume is limited by the collector, for which polycapillaries are generally the optic of choice. Recently, we demonstrated an alternative collection optic for CXRF, consisting of an array of micron-scale collimating channels, etched in silicon, and arranged like spokes of a wheel directed towards a single source position. The optic, while successful, had a working distance of only 0.2 mm and exhibited relatively low total collection efficiency, limiting its practical application. Here, we describe a new design in which the collimating channels are formed by a staggered array of pillars whose side-walls taper away from the channel axis. This approach improves both collection efficiency and working distance, while maintaining excellent spatial resolution. We illustrate these improvements with confocal XRF data obtained at the Cornell High Energy Synchrotron Source (CHESS) and the Advanced Photon Source (APS) beamline 20-ID-B.