Spatially-resolved X-ray Research Articles

Spatially-resolved in-situ/operando structural study of screen-printed BaTiO3/P(VDF-TrFE) flexible piezoelectric device

The incorporation of lead-free BaTiO3 particles into P(VDF-TrFE) provides a versatile way for tuning dielectric and piezoelectric properties. Screen-printing enables the easy production of flexible capacitors. To prevent particle aggregation, the BaTiO3 particles are functionalized with a surfactant. Initially, 60 % vol. BaTiO3 particles are deposited in the second layer out of three layers. After annealing and cooling, the particle distribution is successfully homogeneous in the whole film. After poling at 80 °C, the relative permittivity and the piezoelectric coefficient d33 significantly increase up to 159 and 8 pC/N respectively. In situ/operando spatially-resolved X-ray techniques allow exploring the structural evolution of the composite device during annealing and during an applied electric field. The application of an electric field leads to the quasi-disappearance of the P(VDF-TrFE) ferroelectric state. As a matter of fact, the interactions between the P(VDF-TrFE) and the surfactant may limit the rotation of P(VDF-TrFE) chains near the particles. Hence, paraelectric polymers could be chosen on a mechanical or economic basis for the matrix in piezoelectric composite devices. Regarding BaTiO3, the lattice strain evolves from an extrinsic strain at RT to an intrinsic strain after annealing and cooling. At the cooled state, the tetragonality c/a is higher than 1.01, leading to improved piezoelectric properties. The increase of the average domain size leads to the increase of the composite permittivity. Finally this knowledge facilitates the development of tailored flexible piezoelectric composite devices.

Laboratory-based correlated X-ray imaging and scattering of inhomogeneous glass-ceramics

Nuclear waste glasses often contain complex microstructures, and understanding these are key to predicting and engineering glass durability, since heterogeneity may exist over multiple length scales. Here we use laboratory-based, spatially-resolved X-ray characterization methods that span length scales (10-10-10-2 m): Wide angle X-ray Scattering (WAXS) provides atomic-scale crystallography; Small Angle X-ray Scattering (SAXS) provides nanoscale phase data; X-ray Computed Tomography and projection X-ray radiography map the materials structure over the micrometer and millimeter scales. The pairing of X-ray radiography with SAXS/WAXS in the same instrument enables specific regions on the sample to be characterized with precise spatial resolution. Two molybdenum- and lanthanum-containing simulated nuclear waste glasses were examined, enabling exploration of hierarchal glassy phase separation and spatial partitioning of crystals of powellite and zircon of different morphologies and sizes 10 nm to 1 mm. The tools described in this study offer means of broadly understanding multi-scale structural attributes of multi-phase materials.

Ultra-clean high-mobility graphene on technologically relevant substrates.

Graphene grown via chemical vapour deposition (CVD) on copper foil has emerged as a high-quality, scalable material, that can be easily integrated on technologically relevant platforms to develop promising applications in the fields of optoelectronics and photonics. Most of these applications require low-contaminated high-mobility graphene (i.e., approaching 10 000 cm2 V-1 s-1 at room temperature) to reduce device losses and implement compact device design. To date, these mobility values are only obtained when suspending or encapsulating graphene. Here, we demonstrate a rapid, facile, and scalable cleaning process, that yields high-mobility graphene directly on the most common technologically relevant substrate: silicon dioxide on silicon (SiO2/Si). Atomic force microscopy (AFM) and spatially-resolved X-ray photoelectron spectroscopy (XPS) demonstrate that this approach is instrumental to rapidly eliminate most of the polymeric residues which remain on graphene after transfer and fabrication and that have adverse effects on its electrical properties. Raman measurements show a significant reduction of graphene doping and strain. Transport measurements of 50 Hall bars (HBs) yield hole mobility μh up to ∼9000 cm2 V-1 s-1 and electron mobility μe up to ∼8000 cm2 V-1 s-1, with average values μh ∼ 7500 cm2 V-1 s-1 and μe ∼ 6300 cm2 V-1 s-1. The carrier mobility of ultraclean graphene reaches values nearly double than those measured in graphene processed with acetone cleaning, which is the method widely adopted in the field. Notably, these mobility values are obtained over large-scale and without encapsulation, thus paving the way to the adoption of graphene in optoelectronics and photonics.

Quantitative analysis of an ECR Ar plasma structure by X-ray spectroscopy at high spatial resolution

In the frame of the PANDORA_Gr3 project, aiming at measuring for the first time in-plasma nuclear β-decays of astrophysical interest, an innovative multi-diagnostic approach to correlate plasma parameters to nuclear activity has been proposed [1–3]. This is based on several detectors and techniques (optical emission spectroscopy, RF systems, interferopolarimetry) and here we focus on high resolution spatially-resolved X-ray spectroscopy, performed by means of a X-ray pin-hole camera setup sensitive in the 0.5–20 keV energy domain. We present measurements on an Ar plasma heated by Electron Cyclotron Resonance at the ECR-plasma lab of ATOMKI-Debrecen. The achieved spatial and energy resolution were 0.5 mm and 300 eV at 8 keV, respectively [4]. The new algorithm of analysis for single-photon-counted images has been developed allowing an investigation in High-Dynamic-Range (HDR) mode. Hence a spatially resolved quantitative characterization of plasma vs. plasma walls emitted spectra was done; the investigated electrons are the ones crucial for in-plasma ionization. Both stable and turbulent plasma regimes can be investigated.

(Invited) Direct Observation of the Sulfur-Based Chemical Species in Li-S Batteries By Spatially-Resolved X-Ray Fluorescence Microscopy and X-Ray Absorption Spectroscopy

The demands on low cost and high energy density rechargeable batteries for both transportation and large-scale stationary energy storage are attracting more and more research attention toward new battery systems such as metal, metal-sulfur, metal-air, and multivalent batteries. Since sulfur is an earth-abundant material with low cost and has a high theoretical capacity, Li-S battery chemistry has attracted significant interest during the past decade.The Li-S battery utilizes electrochemical conversion of sulfur (S8) to lithium sulfide (Li2S), going through multiple electron transfer processes associated with long- and short-chain polysulfide (Li2Sx) intermediates. It is well known that the long-chain polysulfides can be dissolved into electrolyte with aprotic organic solvents and migrated to the Li anode side. This so-called “shuttle effect” is considered as the main reason for the capacity loss and low coulombic efficiency of the Li-S system. A lot of efforts have been made on suppressing the polysulfide dissolution through new sulfur-based material and electrolyte, as well as cell engineering. Although the Li-S battery performance has been improved over the past decades, the long‐term cycling stability is still one of the major barriers for the practical application of Li–S batteries. More in‐depth studies on the fundamental understanding of the sulfur reaction mechanism and interactions among the different polysulfide species, the electrolyte, and the electrodes are still greatly needed.In this study, we utilize the spatially-resolved X-ray fluorescence (XRF) microscopy combined with X-ray absorption spectroscopy (XAS) to directly probe the inhomogeneous electrochemical/chemical reactions of the sulfur cathode, and chemical reactions of sulfur contained chemical species. The morphology changes and the redistribution of sulfur and polysulfides in both the S cathode and lithium metal anode were monitored through the XRF images, while the oxidation state of sulfur and changes of the sulfur-containing interfacial layer (i.e., SEI) were characterized through the XAS spectra. Our characterization studies on the sulfur-based cathode materials in Li-S batteries using spatially resolved XRF/XAS techniques provides critical information enabling us to understand the reaction processes and their correlation to cell cycling behavior and failure mechanisms. More details of the result will be discussed at the meeting. Acknowledgement The work done at Brookhaven National Laboratory was supported by Assistant Secretary for Energy Efficiency and Renewable Energy, Vehicle Technology Office of the U.S. DOE, through the Advanced Battery Materials Research (BMR) Program, including Battery500 Consortium under contract DE-SC0012704. This research used beamline 8-BM (TES) of the National Synchrotron Light Source II, U.S. DOE Office of Science User Facilities operated for the DOE Office of Science by Brookhaven National Laboratory under Contract No. DE-SC0012704.

Structure and Mineralogy of Hydrophilic and Biwettable Sub-2 µm Clay Aggregates in Oil Sands Bitumen Froth

A primary concern of commercial mined oil sands operations is the extent to which one can minimize the content of water and solids contaminants in the solvent-diluted bitumen products resulting from the bitumen production processes. During bitumen production, particles of about 2 µm or less may be responsible for the stabilization of water-in-bitumen emulsions that form during aqueous extraction of bitumen and purification of bitumen froth subsequently during the froth treatment processes, thus leading to the presence of those contaminants in solvent-diluted bitumen products. In this study, we separate and analyze sub-2 µm clay solids isolated from typical bitumen froth fed to a froth treatment plant at a commercial mined oil sands operation. Analytical transmission electron microscopy (TEM) with spatially-resolved energy-dispersive X-ray spectroscopy (EDX) and electron energy-loss spectroscopy (EELS) demonstrate key differences in morphology and composition between sub-2 µm clay aggregates with two distinct wettability characteristics: hydrophilic vs. biwettable particle surfaces. In particular, clay platelets with <200 nm lateral dimensions and thicknesses of a few atomic layers, which are intermixed within coarser sub-2 µm clay aggregates, are found to confer clear differences in morphological characteristics and wettability behaviors to the sub-2 µm clay aggregates. The <200 nm clay platelets found within sub-2 µm biwettable clays tend to arrange themselves with random orientations, whereas <200 nm clay platelets within sub-2 µm hydrophilic clays typically form well-ordered face-to-face stacks. Moreover, in biwettable sub-2 µm clay aggregates, <200 nm clay platelets often cover the surfaces of ~1–2 µm sized mineral particles, whereas similarly sized mineral particles in hydrophilic sub-2 µm clay aggregates, in contrast, generally have exposed surfaces without clay platelet coverage. These biwettable vs. hydrophilic behaviors are attributed to a difference in the surface characteristics of the <200 nm clay platelets caused by toluene-unextractable organic carbon coatings. Nanometer-scale carbon mapping reveals an inhomogeneous toluene-unextractable organic carbon coating on the surfaces of <200 nm platelets in biwettable clays. In contrast, hydrophilic clays have a significantly lower amount of toluene-unextractable organic carbon, which tends to be concentrated at steps or near metal oxide nanoparticles on clay particle surfaces. Mixing surface-active organic species, such as asphaltene, resin, or carboxylic organic acids of various types with inorganic solids can lead to a dramatically enhanced emulsion stability. Consequently, understanding the origin and characteristics of sub-2 µm clay solids in bitumen froth is important to (i) clarify their potential role in the formation of stable water-in-oil emulsions during bitumen production and (ii) improve froth treatment process performance to further reduce contaminant solids in solvent-diluted bitumen products. We discuss the implications of our results from these two perspectives.

Study of surface oxidation of polycrystalline rhodium using multivariate analysis based on combined optical microscopy and X-ray photoelectron spectroscopy data

When relatively large areas of the surface are analysed using surface-sensitive compositional techniques like spatially-resolved X-ray Photoelectron Spectroscopy (XPS), the large number of spectra makes traditional quantitative analysis a complex and time-consuming procedure. In turn, “mapping“ a heterogeneous surface using optical microscopy can be very helpful in rapid localization of different surface structures. Thus, developing a procedure to obtain reliable information on the composition of heterogeneous samples that combines the XPS signals with image data is an interesting option in surface analysis. This paper proposes the use of multivariate statistical analysis (MVA) to provide deeper understanding of the observed behaviour and to investigate the relationship between two independent data sets. As a feasibility study, the oxide formation at the polycrystalline rhodium surface, which is a complex system, has been analysed. Unlike existing local models, the pattern of the crystallographically different domains for their role in the oxidation process has been examined on the large scale. The MVA results of this study are consistent with previous research on this topic and may open a supporting approach towards heterogeneous samples analysis.

Analyzing x-ray emission of target impurities to determine the parameters of recombining laser plasma

In this work, the possibility of the implementation of impurities in the compositions of solid thick targets irradiated by intense lasers is discussed in order to solve problems of optically-thick plasma diagnostics. Calculations were conducted for relative intensities of oxygen resonance lines (H-like—3p–1s, 4p–1s, 5p–1s, 6p–1s, 7p–1s transitions) in a recombination quasi-stationary model to obtain plasma parameters. In the experiment with 0.6 ns, 40 J laser pulses focused to 600 μm focal spot at solid polyvinylidene chloride target the parameters of plasma jet stopped by solid oxidized Teflon obstacle were studied by means of spatially-resolved x-ray spectroscopy.

Revealing the inhomogeneous surface chemistry on the spherical layered oxide polycrystalline cathode particles

The hierarchical structure of the composite cathodes brings in significant chemical complexity related to the interfaces, such as cathode electrolyte interphase. These interfaces account for only a small fraction of the volume and mass, they could, however, have profound impacts on the cell-level electrochemistry. As the investigation of these interfaces becomes a crucial topic in the battery research, there is a need to properly study the surface chemistry, particularly to eliminate the biased, incomplete characterization provided by techniques that assume the homogeneous surface chemistry. Herein, we utilize nano-resolution spatially-resolved x-ray spectroscopic tools to probe the heterogeneity of the surface chemistry on LiNi0.8Mn0.1Co0.1O2 layered cathode secondary particles. Informed by the nano-resolution mapping of the Ni valance state, which serves as a measurement of the local surface chemistry, we construct a conceptual model to elucidate the electrochemical consequence of the inhomogeneous local impedance over the particle surface. Going beyond the implication in battery science, our work highlights a balance between the high-resolution probing the local chemistry and the statistical representativeness, which is particularly vital in the study of the highly complex material systems.

Spatially-Resolved Multiple Metallopolymer Surfaces by Photolithography.

A tetrazole-based photoligation protocol for the spatially-resolved encoding of various defined metallopolymers onto solid surfaces is introduced. By using this approach, fabrication of bi- and trifunctional metallopolymer surfaces with different metal combinations were achieved. Specifically, α-ω-functional copolymers containing bipyridine as well as triphenylphosphine ligands were synthesized through reversible addition-fragmentation chain transfer (RAFT) polymerization, and subsequently metal loaded to afford metallopolymers of the widely-used metals gold, palladium, and platinum. Spatially-resolved surface attachment was achieved by means of a nitrile imine-mediated tetrazole-ene cycloaddition (NITEC) based photoligation protocol, exploiting tethered tetrazoles and metallopolymers equipped with a maleimide chain terminus. Metallopolymer coated surfaces with three different metals were prepared and characterized by time-of-flight secondary ion mass spectrometry (ToF-SIMS) and spatially-resolved X-ray photoelectron spectroscopy (XPS) mapping, supporting the preserved chemical composition of the surface-bound metallopolymers. The established photochemical technology platform for arbitrary spatially-resolved metallopolymer surface designs enables the patterning of multiple metallopolymers onto solid substrates. This allows for the assembly of designer metallopolymer substrates.

X-ray diffraction tomography with limited projection information

X-ray diffraction tomography (XDT) records the spatially-resolved X-ray diffraction profile of an extended object. Compared to conventional transmission-based tomography, XDT displays high intrinsic contrast among materials of similar electron density and improves the accuracy in material identification thanks to the molecular structural information carried by diffracted photons. However, due to the weak diffraction signal, a tomographic scan covering the entire object typically requires a synchrotron facility to make the acquisition time more manageable. Imaging applications in medical and industrial settings usually do not require the examination of the entire object. Therefore, a diffraction tomography modality covering only the region of interest (ROI) and subsequent image reconstruction techniques with truncated projections are highly desirable. Here we propose a table-top diffraction tomography system that can resolve the spatially-variant diffraction form factor from internal regions within extended samples. We demonstrate that the interior reconstruction maintains the material contrast while reducing the imaging time by 6 folds. The presented method could accelerate the acquisition of XDT and be applied in portable imaging applications with a reduced radiation dose.

Demonstration of One-shot Spatially-resolved X-ray Absorption Spectroscopy Using Wavelength-dispersed Soft X-rays

A one-shot recording technique for spatially-resolved X-ray absorption spectroscopy has been developed by combining wavelength-dispersed soft X-rays with a photoelectron emission microscope. The wavelength-dispersed soft X-rays, whose wavelength depends on the position, illuminate the sample, and a two-dimensional image of emitted electrons is obtained. Therefore, one can obtain spatial and spectroscopic information simultaneously, without scanning the monochromator. The technique opens the route to quantitative investigation for inhomogeneous and irreversible surface chemical reactions.

Characterization of x-ray imaging crystal spectrometer for high-resolution spatially-resolved x-ray Thomson scattering measurements in shock-compressed experiments

We have proposed, designed and built a dual-channel x-ray imaging crystal spectrometer (XICS) for spectrally- and spatially-resolved x-ray Thomson scattering (XRTS) measurements in the Matter in Extreme Conditions (MEC) end station at the Linac Coherent Light Source (LCLS). This spectrometer employs two spherically-bent germanium (Ge) 220 crystals, which are combined to form a large aperture dispersive element with a spectral bandwidth of ~300eV that enables both the elastic and inelastic x-ray scattering peaks to be simultaneously measured. The apparatus and its characterization are described. A resolving power of ~1900 was demonstrated and a spatial resolution of ~12μm was achieved in calibration tests. For XRTS measurements, a narrow-bandwidth (ΔE/E<0.003) LCLS x-ray free electron laser (XFEL) beam at 5.07keV was used to probe a dense carbon plasma produced in shock-compressed samples of different forms of carbon. Preliminary results of the scattering experiments from Pyrolytic Graphite samples that illustrate the utility of the instrument are presented.

Characterization of a sustainable sulfur polymer concrete using activated fillers

Sulfur polymer concrete (SPC) is a thermoplastic composite concrete consisting of chemically modified sulfur polymer and aggregates. This study focused on the characterization of a new SPC that has been developed as a sustainable construction material. It is made from industrial by-product sulfur that is modified with activated fillers of fly ash, petroleum refinery residual oil, and sand. Unlike conventional sulfur polymer cements made using dicyclopentadiene as a chemical modifier, the use of inexpensive industrial by-products enables the new SPC to cost-effectively produce sustainable, low-carbon, thermoplastic binder that can compete with conventional hydraulic cement concretes. A series of characterization analyses was conducted including thermal analysis, X-ray diffraction, and spatially-resolved X-ray absorption spectroscopy to confirm the polymerization of sulfur induced from the presence of the oil. In addition, mechanical testing, internal pore structure analysis, and scanning electron microscope studies evaluate the performance of this new SPC as a sustainable construction material with a reduced environmental impact.

空間分解 XAFS による不均一系固体触媒のイメージング解析

In this paper, we present our recent results of 2D or 3D imaging of heterogeneous solid catalysts by spatially-resolved X-ray absorption fine structure (XAFS) techniques. These state-of-art XAFS imaging techniques show heterogeneous behaviors of solid catalysts. XAFS imaging of an automobile exhausting catalyst and electrocatalyst for polymer electrolyte fuel cell was presented.

MPCVD growth of 13C-enriched diamond single crystals with nitrogen addition

This study describes the growth of 13C-enriched (100)-oriented diamond single crystals by the MPCVD (microwave plasma chemical vapour deposition) process. All crystals are at least 6×6mm2 in area and 0.5–1.0mm in thickness. The samples with nominal 13C percentages (R=[13C]/[13C+12C]) of 0.011 (natural abundance), 0.10, 0.21, 0.24 and 0.34 were obtained by controlling the flow of the carbon-13 and carbon-12 methane feed gases. To obtain thicker and near-colourless quality 13C-enriched diamond, 190ppm of nitrogen was added into the gas mixture. The shift towards lower frequency in the Raman peak positions and decrease in the thermal conductivities of the near-colourless crystals with increasing 13C percentages are similar to previous studies of isotopically-controlled diamond grown with no nitrogen additive. The images of the structural defects associated with 13C-enrichment obtained by spatially-resolved X-ray rocking curve measurement show distinct patterned structures that runs parallel to the <100> direction. Moreover, the broadening in the line width of the nuclear magnetic resonance (NMR) peak from sp313C correlates with increasing R. We also expand the study by injecting 500ppm of nitrogen. Higher nitrogen concentration leads to the formation of brown crystals. The brown crystals show far greater 13C NMR peak intensity than the near-colourless. This suggests that paramagnetic nitrogen impurities in the brown crystals hasten the spin-lattice relaxation time of the 13C nuclear spin that resulted in higher intensity. The isotopic splitting observed for the localized vibrational mode of the NVH0 defect in brown crystals is attributed to the co-existence of both the 13C (3114.2cm−1) and 12C (3123.5cm−1). Unlike the isotopic splitting observed for NVH0 defect, the peak position of the Ns+ defect shifts towards lower frequency as R increases. Not only have we demonstrate the growth of bigger isotopically-controlled diamond single crystals, the results shown here have provided a framework to further investigate the interplay between 13C atoms and nitrogen impurity.

Spatially-resolved X-ray scattering measurements of a planar blast wave

We present X-ray scattering measurements characterizing the spatial temperature and ionization profile of a blast wave driven in a near-solid density foam. Several-keV X-rays scattered from a laser-driven blast wave in a carbon foam. We resolved the scattering in high resolution in space and wavelength to extract the plasma conditions along the propagation direction of the blast wave. We infer temperatures of 20–40 eV and ionizations of 2–4 in the shock and rarefaction regions of the blast wave. This range of measured ionization states allows for a detailed comparison between different models for the bound–free scattering. FLYCHK simulations of the temperature-ionization balance generally agree with the experimental values in the shocked region while consistently underestimating the ionization in the rarefaction.

Orientation of a Dispersion of Kaolinite Flowing in a Jet

Orientational alignment in a dilute dispersion of kaolinite particles has been investigated in a flow pattern that combines both shear and elongational stress, namely flow at a jet created by a 2 mm diameter nozzle inserted in a 6 mm diameter pipe. Spatially-resolved X-ray diffraction with synchrotron radiation permits detailed maps of the alignment to be deduced and compared with fluid mechanics calculations of the flow. The angular distribution of diffracted intensity from a given position in the pipe provides information about the orientation distribution of the particles. This is quantified and presented in terms of order parameters. The cone-shaped nozzle provides a jet of liquid giving a high degree of alignment of the particles that is uniform along lines across the conical section and constant in the small straight-sided region at the exit of the nozzle. The vortex motion that arises from the flow with a modest Reynolds number could be determined as well as the tendency for some particles to align with their large faces perpendicular to the overall flow direction at the flat surface of the nozzle outlet.

X-RAY EMISSION FROM HESS J1731-347/SNR G353.6-0.7 AND CENTRAL COMPACT SOURCE XMMS J173203-344518

We present new results of the HESS J1731-347/SNR G353.6-0.7 system from XMM-NEWTOM and Suzaku X-ray observations, and Delinha CO observations. We discover extended hard X-rays coincident with the bright, extended TeV source HESS J1731-347 and the shell of the radio SNR. We find that spatially-resolved X-ray spectra can generally be characterized by an absorbed power-law model, with photon-index of ~ 2, typical of non-thermal emission. A bright X-ray compact source, XMMS J173203-344518, is also detected near the center of the SNR. We find no evidence of a radio counterpart or an extended X-ray morphology for this source, making it unlikely to be a pulsar wind nebular (PWN). The spectrum of the source can be well fitted by an absorbed blackbody with a temperature of ~ 0.5 keV plus a power-law tail with a photon-index of ~ 5, reminiscent of the X-ray emission of a magnetar. CO observations toward the inner part of the HESS source reveal a bright cloud component at -20+/-4 km s^{-1}, which is likely located at the same distance of ~ 3.2 kpc as the SNR. Based on the probable association between the X-ray and $\gamma$-ray emissions and likely association between the CO cloud and the SNR, we argue that the extended TeV emission originates from the interaction between the SNR shock and the adjacent CO clouds rather than from a PWN.

A DEEPCHANDRAOBSERVATION OF THE OXYGEN-RICH SUPERNOVA REMNANT 0540-69.3 IN THE LARGE MAGELLANIC CLOUD

Using our deep ~120 ks Chandra observation, we report on the results from our spatially-resolved X-ray spectral analysis of the "oxygen-rich" supernova remnant (SNR) 0540-69.3 in the Large Magellanic Cloud. We conclusively establish the nonthermal nature of the "arcs" in the east and west boundaries of the SNR, which confirms the cosmic-ray electron acceleration in the supernova shock (B ~ 20-140 microG). We report tentative evidence for Fe overabundance in the southern region close to the outer boundary of the SNR. While such a detection would be intriguing, the existence of Fe ejecta is not conclusive with the current data because of poor photon statistics and limited plasma models. If it is verified using deeper X-ray observations and improved plasma models, the presence of Fe ejecta, which was produced in the core of the supernova, near the SNR's outer boundary would provide an intriguing opportunity to study the explosive nucleosynthesis and the ejecta mixing in this young core-collapse SNR. There is no evidence of X-ray counterparts for the optical O-rich ejecta in the central regions of the SNR.