Juergen Thieme

Early science commissioning results of the sub-micron resolution X-ray spectroscopy beamline (SRX) in the field of materials science and engineering

Beamline commissioning activities at the Sub-micron Resolution Spectroscopy Beamline, SRX, one of the project beamlines of the National Synchrotron Light Source II, began in December 2014. SRX is a hard x-ray micro-probe beamline. The technical capabilities presented in this paper include scanning micro-fluorescence microscopy (µ-XRF) and x-ray absorption near-edge structure (µ-XANES) spectroscopy. The high flux KBs station with sub-micron resolution in the step-scanning mode has been commissioned with results presented in this paper. Capabilities under commissioning/planning include XRF-XANES stack imaging, a high resolution station (sub-100 nm), x-ray fluorescence tomography, integration of Maia detector, and fly-scan mode. Early science commissioning results from SRX in the materials science field are presented in this paper. Topics being studied include nanoporous materials for energy conversion/storage, thin film materials for electronics, degradation of paint materials for art conservation, and grai...

Simulation and optimization of the NSLS-II SRX beamline combining ray-tracing and wavefront propagation

The Sub-micron Resolution X-ray spectroscopy (SRX) beamline will benefit from the ultralow emittance of the National Synchrotron Light Source II to address a wide variety of scientific applications studying heterogeneous systems at the sub-micrometer scale. This work focuses on the KB branch (ΔE: 4.65-28 keV). Its main optical components include a horizontally focusing mirror forming an adjustable secondary source, a horizontally deflecting monochromator and two sets of Kirkpatrick-Baez mirrors as focusing optics of two distinct inline stations for operations requiring either high flux or high resolution. In the first approach, the beamline layout was optimized with ray-tracing calculations involving Shadowvui computer codes. As a result, the location and characteristics of optics were specified for achieving either the most intense or the smallest monochromatic beam possible on the target (1013 ph/s or 1012 ph/s respectively in a 500 nm or 65 nm focal spot). At the nanoprobe station, the diffraction limited focusing of X-rays is governed by the beam coherence. Hence, a classical geometric approach is not anymore adapted. To get reliable estimates of the Nanoprobe performances, a wavefront propagation study was performed using Synchrotron Radiation Workshop (SRW) code. At 7.2 keV, calculations show an intense (1012 ph/s) 67 nm wide diffraction limited spot achieved with actual metrological data of mirrors.

Elemental and Molecular Segregation in Oil Paintings due to Lead Soap Degradation

The formation of Pb, Zn, and Cu carboxylates (soaps) has caused visible deterioration in hundreds of oil paintings dating from the 15th century to the present. Through transport phenomena not yet understood, free fatty acids in the oil binding medium migrate through the paint and react with pigments containing heavy metals to form soaps. To investigate the complex correlation among the elemental segregation, types of chemical compounds formed, and possible mechanisms of the reactions, a paint sample cross-section from a 15th century oil painting was examined by synchrotron X-ray techniques. X-ray fluorescence (XRF) microscopy, quantified with elemental correlation density distribution, showed Pb and Sn segregation in the soap-affected areas. X-ray absorption near edge structure (XANES) around the Pb-L3 absorption edge showed that Pb pigments and Pb soaps can be distinguished while micro-XANES gave further information on the chemical heterogeneity in the paint film. The advantages and limitations of these synchrotron-based techniques are discussed and compared to those of methods routinely used to analyze paint samples. The results presented set the stage for improving the information extracted from samples removed from works of art and for correlating observations in model paint samples to those in the naturally aged samples, to shed light onto the mechanism of soap formation.

Three-Dimensional Morphological and Chemical Evolution of Nanoporous Stainless Steel by Liquid Metal Dealloying

Nanoporous materials, especially those fabricated by liquid metal dealloying processes, possess great potential in a wide range of applications due to their high surface area, bicontinuous structure with both open pores for transport and solid phase for conductivity or support, and low material cost. Here, we used X-ray nanotomography and X-ray fluorescence microscopy to reveal the three-dimensional (3D) morphology and elemental distribution within materials. Focusing on nanoporous stainless steel, we evaluated the 3D morphology of the dealloying front and established a quantitative processing-structure-property relationship at a later stage of dealloying. The morphological differences of samples created by liquid metal dealloying and aqueous dealloying methods were also discussed. We concluded that it is particularly important to consider the dealloying, coarsening, and densification mechanisms in influencing the performance-determining, critical 3D parameters, such as tortuosity, pore size, porosity, curvature, and interfacial shape.

Environmentally induced chemical and morphological heterogeneity of zinc oxide thin films

Zinc oxide (ZnO) thin films have been reported to suffer from degradation in electrical properties, when exposed to elevated heat and humidity, often leading to failures of electronic devices containing ZnO films. This degradation appears to be linked to water and oxygen penetration into the ZnO film. However, a direct observation in the ZnO film morphological evolution detailing structural and chemical changes has been lacking. Here, we systematically investigated the chemical and morphological heterogeneities of ZnO thin films caused by elevated heat and humidity, simulating an environmental aging. X-ray fluorescence microscopy, X-ray absorption spectroscopy, grazing incidence small angle and wide angle X-ray scattering, scanning electron microscopy (SEM), ultra-high-resolution SEM, and optical microscopy were carried out to examine ZnO and Al-doped ZnO thin films on two different substrates—silicon wafers and flexible polyethylene terephthalate (PET) films. In the un-doped ZnO thin film, the simulated ...

Operando Multi-modal Synchrotron Investigation for Structural and Chemical Evolution of Cupric Sulfide (CuS) Additive in Li-S battery

Conductive metal sulfides are promising multi-functional additives for future lithium-sulfur (Li-S) batteries. These can increase the sulfur cathode’s electrical conductivity to improve the battery’s power capability, as well as contribute to the overall cell-discharge capacity. This multi-functional electrode design showed initial promise; however, complicated interactions at the system level are accompanied by some detrimental side effects. The metal sulfide additives with a chemical conversion as the reaction mechanism, e.g., CuS and FeS2, can increase the theoretical capacity of the Li-S system. However, these additives may cause undesired parasitic reactions, such as the dissolution of the additive in the electrolyte. Studying such complex reactions presents a challenge because it requires experimental methods that can track the chemical and structural evolution of the system during an electrochemical process. To address the fundamental mechanisms in these systems, we employed an operando multimodal x-ray characterization approach to study the structural and chemical evolution of the metal sulfide—utilizing powder diffraction and fluorescence imaging to resolve the former and absorption spectroscopy the latter—during lithiation and de-lithiation of a Li-S battery with CuS as the multi-functional cathode additive. The resulting elucidation of the structural and chemical evolution of the system leads to a new description of the reaction mechanism.

Speciation of Soil Phosphorus Assessed by XANES Spectroscopy at Different Spatial Scales

Precise management of soil phosphorus (P) to meet competing demands of agriculture and environmental protection can benefit from more comprehensive characterization of P speciation in soils. Our objectives were to provide spatial context for spectroscopic analyses of soil P speciation in relation to molecular-scale species and landscape-scale management of P, and to compare soil P-species diversity from spectroscopic measurements at submicron and millimeter scales. The spatial range of ∼26 orders of magnitude between atomic and field scales presents a challenge to upscaling and downscaling information from spectroscopic analyses of soils. Scanning fluorescence X-ray microscopy images of a 50-μm × 45-μm area of an organic soil sample showed heterogeneous distributions of P, Al, and Si. Microscale X-ray absorption near edge structure (μ-XANES) spectra collected at the P K-edge from 12 spots on the soil sample exhibited diverse features that indicated variations in highly localized P speciation. Linear combination fitting analysis of the μ-XANES spectra included various proportions of three standards that appeared in fits for most spots and five standards that appeared in fits for one spot each. The fit to a bulk-soil spectrum was dominated by two of the common standards in the μ-XANES fits, and a fit to the sum of μ-XANES spectra included four of the standards. These results illustrate a gain in P species sensitivity from spatially resolved XANES analysis. Integrating spectroscopic analyses from multiple scales determines soil P species diversity and will ultimately help connect speciation to the chemical reactivity and mobility of P in soils.

Initial performances of first undulator-based hard x-ray beamlines of NSLS-II compared to simulations

Commissioning of the first X-ray beamlines of NSLS-II included detailed measurements of spectral and spatial distributions of the radiation at different locations of the beamlines, from front-ends to sample positions. Comparison of some of these measurement results with high-accuracy calculations of synchrotron (undulator) emission and wavefront propagation through X-ray transport optics, performed using SRW code, is presented.

Characterizing Working Catalysts with Correlated Electron and Photon Probes

1. Center for Functional Nanomaterials, Brookhaven National Laboratory, New York, NY 11973 2. Department of Physics, Yeshiva University, New York, NY 10016 3. Department of Chemistry, University of Illinois at Urbana-Champaign, Illinois 61820 4. National Synchrotron Light Source II, Brookhaven National Laboratory, New York, NY 11973 5. Materials Science and Engineering Department, Stony Brook University, Stony Brook 11794 6. Department of Chemical Engineering, Columbia University, New York, NY 10027

Cationic Ordering Coupled to Reconstruction of Basic Building Units during Synthesis of High-Ni Layered Oxides

Metal (M) oxides are one of the most interesting and widely used solids, and many of their properties can be directly correlated to the local structural ordering within basic building units (BBUs). One particular example is the high-Ni transition metal layered oxides, potential cathode materials for Li-ion batteries whose electrochemical activity is largely determined by the cationic ordering in octahedra (e.g., the BBUs in such systems). Yet to be firmly established is how the BBUs are inherited from precursors and subsequently evolve into the desired ordering during synthesis. Herein, a multimodal in situ X-ray characterization approach is employed to investigate the synthesis process in preparing LiNi0.77Mn0.13Co0.10O2 from its hydroxide counterpart, at scales varying from the long-range to local individual octahedral units. Real-time observation corroborated by first-principles calculations reveals a topotactic transformation throughout the entire process, during which the layered framework is retained; however, due to preferential oxidation of Co and Mn over Ni, significant changes happen locally within NiO6 octahedra. Specifically, oxygen loss and the associated symmetry breaking occur in NiO6; as a consequence, Ni2+ ions become highly mobile and tend to mix with Li, causing high cationic disordering upon formation of the layered oxides. Only through high-temperature heat treatment, Ni is further oxidized, thereby inducing symmetry reconstruction and, concomitantly, cationic ordering within NiO6 octahedra. Findings from this study shed light on designing high-Ni layered oxide cathodes and, more broadly, various functional materials through synthetic control of the constituent BBUs.