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JAN
31
Friday
NSLS-II Friday Lunchtime Seminar
"Tracing Processes Involving the Reactive Intermediates of To Better Understand the Role of Sulfur Cycling on the Fate of Arsenic and Iron in Sediments; Using Reactive Intermediates to Document Extensive Cryptic Sulfur Cycling Affecting Arsenic Levels"
Presented by BENJAMIN C. BOSTICK, Columbia University, Palisades, NY
12 pm, NSLS-II Bldg. 743 Room 156
Friday, January 31, 2020, 12:00 pm
Hosted by: Ignace Jarrige
Arsenic (As) groundwater contamination is thought to result from the reductive dissolution of As-bearing iron oxides by microorganisms. Our understanding of the how reactions occur commonly depends on observing the consumption and production of reactants and products respectively. This approach can be insufficient in environmental systems containing complex compositions and phases that can react through multiple and distinct coupled biological and chemical processes. We suggest it is more effective to study environmental processes by considering dissolved and mineral species as reactive intermediates in geochemical cycles where their concentration is controlled by the balance between their production, consumption and transport. Here, we apply this approach to elucidate a critical role of sulfur (S) cycling in iron reduction in sediments affected by As contamination. Arsenic (As) contamination in soil and groundwater is commonly associated with iron reduction because the concentration of dissolved As and Fe(II) increase together as Fe(III) minerals convert to Fe(II) minerals. In contrast, sulfate concentrations are usually low and stable in groundwaters affected by As. This stability is often interpreted as evidence for the minimal role of S cycling in Fe reduction; however, there is mounting biochemical and mineralogical evidence that sulfate reduction is active and critical to both Fe(III) reduction and As mobilization. Sediment iron mineralogies indicate that reactive Fe(III) minerals are present in most sediments and this Fe(III) is particularly susceptible to chemical and biological reduction. These Fe minerals were transformed to Fe(II) carbonate, green rusts, and, rarely, iron sulfides as the sediments became reduced. The microorganisms identified in sediments undergoing reduction were not iron reducers, and often were autotrophs involved in S cycling. This data suggests that sulfate reduction is active, and tightly coupled to the oxidation of sulfide and elem
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FEB
13
Thursday
NSLS-II Colloquium
"Subsurface Landscapes of Oxidation and Reaction in the Critical Zone"
Presented by Susan Brantley, Pennsylvania State University, PA
4 pm, Large Seminar Room, Bldg. 510
Thursday, February 13, 2020, 4:00 pm
Hosted by: John Hill
The globally ubiquitous mineral pyrite oxidizes even at low oxygen concentrations. As the most common crustal sulfide, pyrite reactivity impacts sulfur, iron, oxygen, and carbon budgets globally. We discovered that pyrite oxidizes completely at tens of meters depth even in low-porosity rocks in catchments in humid climates. As erosion exposes the pyrite to near-surface conditions in low porosity rocks, pore and fracture development is the main control on the rate of oxidative weathering. Between fractures, oxygen diffusion limits the weathering and oxidation is inferred to be largely abiotic because bacteria cannot enter rock matrix pores. Oxygen concentrations and erosion rates together can explain pyrite-derived sulfate fluxes in rivers to the ocean and may account for the presence or absence of pyrite in detrital sediments over Earth history.
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NSLS-II Friday Lunchtime Seminar
"Real-space Local Correlated Motion in Liquids studied by using Inelastic Scattering"
Presented by Yuya Shinohara, Oak Ridge National Laboratory
Friday, January 17, 2020, 12 pm
NSLS-II Bldg. 743 Room 156Hosted by: Ignace Jarrige
Liquids are critical to our daily life. A paramount example is water, which covers 70% of the Earth's surface and make up about 80% of our body. Liquids are also crucial to many current energy technologies. Despite their importance, our understanding of liquids at the atomic level is much poorer than that for crystalline solids. Particularly elusive is a detailed description of the correlated dynamics in liquids, which is the key to controlling the transport properties of liquids. Recent progress in inelastic X-ray/neutron scattering makes it possible to obtain inelastic scattering spectra over a wide energy transfer (E) and momentum transfer (Q) with a high E- and Q-resolution within a reasonable amount of time. This enables us to calculate the Van Hove correlation functions via Fourier transform. With this novel approach, we have determined spatial and temporal correlations of molecular motion of liquids. In this presentation, I will present our recent efforts in understanding the real-space local correlated motion in liquids.
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CSI Q Seminar
"Probing quantum entanglement at the Electron Ion Collider"
Presented by Dmitri Kharzeev, Stony Brook University and BNL
Wednesday, December 18, 2019, 1:30 pm
Training Room, Bldg 725Hosted by: Layla Hormozi
The structure functions measured in deep-inelastic scattering are related to the entropy of entanglement between the region probed by the virtual photon and the rest of the hadron. This opens new possibilities for experimental and theoretical studies using the Electron Ion Collider. The real-time evolution of the final state in deep-inelastic scattering can be addressed with quantum simulations using the duality between high energy QCD and the Heisenberg spin chain.
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NSLS-II Friday Lunchtime Seminar
"Operation at 500mA average current on the horizon"
Presented by Alexei Blednykh, NSLS-II
Friday, December 6, 2019, 12 pm
NSLS-II Bldg. 743 Room 156Hosted by: Igna
500mA average current achieved in NSLS-II. Limitations on the total average current will be discussed in details. Localized heating of the vacuum components was the major issue. Since the heating issues were resolved we were able to demonstrate 500mA during the beam study time. However, for the regular operation @500mA we need more power from the RF system to compensate the synchrotron radiation losses produced by the bending magnets, present and future insertion devices. To mitigate the heating issue and increase the beam stability, bunch lengthening will be beneficial for NSLS-II.
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NSLS-II Friday Lunchtime Seminar
"In Situ & ACERT - The LANL-BNL Cathode Collaboration"
Presented by John Smedley, Los Alamos National Laboratory
Friday, November 22, 2019, 12 pm
NSLS-II Bldg. 743 Room 156Hosted by: Ignace Jarrige
The Applied Cathode Enhancement and Robustness Technologies (ACERT) capability at LANL and the in-situ x-ray analysis growth chamber at BNL are two of the premier tools available for development of photocathode technologies. We are following a model of innovation and collaboration to move cathodes from lab to application, guided by theory, modeling, and experimental validation. This presentation will focus on two recent technology advances – cathodes with "atomic armor", single monolayers of coatings to the cathode surface and/or substrate to improve lifetime and enable operating in inferior vacuum, and highly crystalline CsTe, providing evidence that better crystallinity can improve QE while supporting an ultra-smooth surface. We hope to engender both technical discussion in these areas and open the door to future collaborations. LA-UR-19-28272
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NSLS-II Friday Lunchtime Seminar
"Underpinning the nuclear fuel cycle with synchrotron and laboratory based X-ray absorption spectroscopy"
Presented by Neil Hyatt, University of Sheffield, United Kingdom
Friday, November 8, 2019, 12 pm
NSLS-II Bldg. 743 Room 156Hosted by: Ignace Jarrige
Nuclear energy provides about 30% of the world's low carbon electricity supply, from more than 450 civil nuclear reactors. The supporting nuclear fuel cycle comprises a suite of industrial processes, which transform uranium ore into nuclear fuel, and support reactor operations, decommissioning, waste management, and geological disposal. This seminar will highlight three case studies in the application of X-ray absorption spectroscopy (XAS) in the nuclear fuel cycle, embracing environmental contamination, nuclear forensics, and radioactive waste management. In addition to exploitation of state of the art micro-focus multi-modal beamlines at synchrotron light sources, I will also show how we are using new developments in laboratory based XAS instrumentation, to probe element speciation in nuclear materials.
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CSI Q Seminar
"Many-body physics with atoms and molecules under quantum control"
Presented by Sebastain Will, Columbia University
Thursday, November 7, 2019, 3 pm
Conference room 201, Bldg 734Hosted by: Layla Hormozi
Over the past decade, quantum simulators based on ultracold atoms have emerged as a powerful tool to address open questions in strongly interacting systems and nonequilibrium quantum dynamics that have relevance in all areas of physics, from strongly correlated materials to cosmology. Today, quantum simulators based on ultracold dipolar molecules are within experimental reach, which exploit long-range dipole-dipole interactions and will give access to new classes of strongly correlated many-body systems. In this talk, I will present our efforts towards quantum simulation with ultracold dipolar molecules. In trailblazing experiments we have demonstrated the creation of ultracold molecules via atom-by-atom assembly, which yields complete control over the molecular degrees of freedom, including electronic, vibrational, rotational, and nuclear spin states. Exploiting this control, we have observed long nuclear spin coherence times in molecular ensembles, which makes ultracold molecules an interesting candidate for the realization of a long-lived quantum memory. In addition, the dipole-dipole interactions between molecules can be flexibly tuned via external electrostatic and microwave fields. This motivates our current work towards two-dimensional systems of strongly interacting molecules, which promises access to novel quantum phases, will enable high-speed simulation of quantum magnetism, and points towards potential quantum computing schemes based on ultracold molecules. In the end, I will briefly present our new project on enhancing quantum coherence by dissipation in programmable atomic arrays. For this effort we will develop a novel nanophotonic platform that will enable trapping of individual atoms in optical tweezer arrays with unprecedented accuracy and high-speed tunability.
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NSLS-II Friday Lunchtime Seminar
"Disentangling the nematode-microbiome interactions underlying long-term different crop rotation systems"
Presented by Kaile Zhang, University of Florida
Friday, October 25, 2019, 12:30 pm
NSLS-II Bldg. 743 Room 156Hosted by: Ignace Jarrige
Integrating two years of bahiagrass (Paspalum notatum) into conventional peanut (Arachis hypogea L.) and cotton (Gossypium hirsutum L.) cropping systems (bahiagrass-bahiagrass- peanut-cotton) improves soil quality and crop production compared with the conventional peanut-cotton-cotton rotation (CR). However, it is unclear if this system, known as a sod-based rotation (SBR), affects interactions within soil biota and if such interactions affect nutrient cycling and soil fertility. In this study, we collected soils from long-term plots under CR and SBR (located in Quincy, FL), before cotton planting. Our results showed that the metabolic activities of relative low trophic groups (i.e., bacterivores and herbivores) were positively correlated with r-strategists irrespective of cropping systems, but negatively with k-strategists only under CR. These demonstrated that microbial communities under higher rotational diversity contributed larger to C, energy, and nutrient flows in soil food webs relative to CR. Compared with SBR, one or more functional nematodes groups were entirely missing or showed few abundances, and less evenness of the microbial community was exhibited under CR in spite of no significant differences between these twoKo systems. These results imply that SBR with greater rotational diversity induced higher soil community diversity and consequently sustains the distribution of soil biological community, with positive effects on soil nutrient availability and the control of plant parasites.
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NSLS-II Friday Lunchtime Seminar
"Plant-fungal symbiosis and their potential impacts on terrestrial biogeochemistry"
Presented by Ko-Hsuan (Koko) Chen, University of Florida
Friday, October 25, 2019, 12 pm
NSLS-II Bldg. 743 Room 156Hosted by: Ignace Jarrige
Fungi are associated with all lineages of land plants. While plant-fungal symbiosis is common, many of their interactions, ranging from mutualism, commensalism, to parasitism are yet to be determined. As plant-fungal symbiosis are tightly linked to nutrient cycling, different interaction types have substantial impacts on biogeochemistry. Here, we will use two plant-fungal symbiosis examples: 1) Pine and their ectomycorrhizal fungi, and 2) mosses and their associated fungi, to illustrate how considering plant-fungal interaction and biogeochemistry together can further our understanding toward a better understanding of plant-fungal biology.
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NSLS-II Friday Lunchtime Seminar
"Imaging antiferromagnetic domains using x-ray Bragg phase contrast at CSX beamline"
Presented by Valery Kiryukhin, Rutgers University, New Jersey
Friday, October 4, 2019, 10:30 am
NSLS-II Bldg. 743 Room 156Hosted by: Ignace Jarrige
We review our recent experiments on imaging antiphase antiferromgnetic domains at CSX-1. The technique utilizes interference effects revealing the domain boundaries. The measurements produce direct images, and are done in real time.
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NSLS-II Friday Lunchtime Seminar
"Crystal Engineering of Lanthanide Metal-Organic Frameworks (Ln-MOFs): A Rational pproach to Designing Materials with Targeted Applications"
Presented by Zeyar Min, Univ of the West Indies, Mona Campus, Jamaica
Friday, September 27, 2019, 12:30 pm
NSLS-II Bldg. 743 Room 156Hosted by: Ignace Jarrige
Metal-organic frameworks (MOFs) are hybrid organic/inorganic structures with well-defined topologies which feature metal ions or clusters bridged by rigid organic linkers and have attracted immense interest for their catalytic, sensing, magnetic and adsorption properties among others. Their high porosity (surface areas of up to 7000 m2/g) can be exploited to encapsulate a wide variety of guest molecules and numerous possibilities for tunable characteristics arise from careful manipulation of both the organic and inorganic components. One of the crystal engineering approaches of MOFs is reticular synthesis and enables rational design and assembly of novel porous materials by utilizing building blocks with varying structures and functionalities to attain certain desired physical and chemical properties. However, reticular synthesis using lanthanide metals ions as building blocks is disinclined due to their high coordination numbers and unpredictable coordination chemistry. Herein, a new approach to the crystal engineering of Ln-MOFs, their ratiometric tunable luminescence properties and ability to sense metal ions and components of nitroaromatic explosives is presented.
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NSLS-II Friday Lunchtime Seminar
"Quantum Computing on crystalline beams of ions: the concept and proof-of-principle experiments"
Presented by Timur Shaftan, NSLS-II
Friday, September 27, 2019, 12 pm
NSLS-II Bldg. 743 Room 156Hosted by: Ignace Jarrige
One of the promising directions in Quantum Computers (QC) is based on using ion traps. In a modern QC, several tens of ions are collected in an electromagnetic trap of a cm in size, with their motion cooled down to micro K temperature level, leading to entanglement of their quantum states, controlled by laser and RF fields. These ions = qubits then used to run quantum computations at unprecedent rate using specialized codes (check, for example, QuTip, Quantum Toolbox in Python). I will discuss a concept of a QC, which holds a promise to support 105 of qubits in contrast to the state-of-the-art devices. The idea is to use crystalline beams of ions in an accelerator as the medium for qubits. The crystalline beams were demonstrated in storage rings in 1980s when many protons, being cooled with electron beam formed a revolving ring with crystalline-like structure inside. Marrying this concept with that of the QC on a conventional ion trap, one might consider expansion of the QC to a large particle accelerator with high qubit capacity. The latter is important for expansion of QC capabilities, including the processing power and robustness against errors due to decoherence. In this presentation I will go over the concept and my analysis of a few challenges that require proof-of-principal experiments so that the some basic aspects of this interesting concept are validated.
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NSLS-II Friday Lunchtime Seminar
"Towards Real Time Characterization of Grain Growth from the Melt"
Presented by Christopher Wright, Department of Applied Physics and Applied Mathematics, Columbia University
Friday, September 20, 2019, 12 pm
NSLS-II Bldg. 743 Room 156Hosted by: Ignace Jarrige
Single crystal materials have unique properties which are endowed by their long ranging atomic order. Growing these crystalline materials can be difficult, as entropy favors disordered grains and the growth dynamics are poorly understood, leaving the process of making crystals prone to trial and error and limiting its application in the broader research community. In my talk I will discuss our work elucidating the microstructural dynamics of floating zone growth using x-ray scattering techniques. One focus of this work is building the computational infrastructure to process the large stream of heterogeneous data which results from these techniques. These pieces of infrastructure are then used to characterize the growth of Rutile crystals via a float zone furnace. Particular attention is paid to the competition amongst the grains, and how certain grains are selected from the plethora which are created at the beginning of the growth.
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NSLS-II Friday Lunchtime Seminar
"Coherent X-ray Scattering Studies of Surface Processes: Self-Organized Ion Beam Nanopatterning"
Presented by Karl Ludwig, Boston University, MA
Friday, August 23, 2019, 12 pm
NSLS-II Bldg. 743 Room 156Hosted by: Ignace Jarrige
Karl Ludwig*, Mahsa Mokhtarzadeh*, Jeffrey Ulbrandt#, Peco Myint*, Suresh Narayanan+, and Randall Headrick# *Boston University / #University of Vermont +Advanced Photon Source, Argonne National Laboratory Enabled by the continued increases in brilliance available from synchrotron x-ray sources, our goal is to develop coherent x-ray scattering as a powerful new tool for the investigation of surface dynamics during growth and patterning processes. In particular, our research has been developed new approaches in X-ray Photon Correlation Spectroscopy (XPCS), using it to examine the dynamics of kinetic roughening in amorphous thin film growth, the step structure evolution in polycrystalline epitaxial growth and self-organized ion beam nanopatterning. Broad-beam low-energy ion bombardment can lead to the spontaneous formation of nanoscale surface structures, but the dominant mechanisms driving evolution remain controversial. Here I will describe our studies of the classic case of ion-beam rippling of SiO2 surfaces, in which we examine the relationship between the average kinetics of ripple formation and the underlying ?uctuation dynamics. In the early stage growth of ?uctuations we find a novel behavior with memory stretching back to the beginning of the bombardment. For a given length scale, correlation times do not grow signi?cantly beyond the characteristic time associated with the early-stage ripple growth. In the late stages of patterning, when the average surface structure on a given length scale is no longer evolving, dynamical processes continue on the surface. Nonlinear processes dominate at long length scales, leading to compressed exponential decay of the speckle correlation functions, while at short length scales the dynamics appears to approach a linear behavior consistent with viscous ?ow relaxation. This behavior is found to be consistent with simulations of a recent nonlinear growth model. In addition
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NSLS-II Friday Lunchtime Seminar
"Quantum materials based on metamorphic InAsSb superlattices"
Presented by Sergey Suchalkin, Stony Brook University, Stony Brook, NY
Friday, June 28, 2019, 12 pm
NSLS-II Bldg. 743 Room 156Hosted by: Ignace Jarrige
Recently proposed metamorphic InSbxAs1-x/InSbyAs1-y superlattices (SLs) manifest a new class of bulk materials where the bandgap can be tuned down to negative values [1,2]. Application of the virtual substrate approach relieves the limitation dictated by the substrate lattice constant and makes possible to grow materials with high crystalline quality in the entire range of alloy compositions. While remaining viable candidates to compete with the state-of-the-art mercury-cadmium-telluride (MCT) compound materials in the field of infrared detection and imaging, the new low-bandgap InAsSb SLs are new platform for investigation of intriguing physical phenomena such as the quantum spin Hall effect, and Majorana zero modes which has recently appeared in the searchlight of solid-state physics. I will present the latest results on experimental and theoretical analysis of carrier dispersion and band structure of short period metamorphic InSbxAs1-x/InSbyAs1-y superlattices, obtained in the Optoelectronics group of Stony Brook University. We demonstrate that the Dirac dispersion is realized in short period InAs1-x Sbx/InAs1-ySby metamorphic superlattices with the bandgap tuned to zero by adjusting the superlattice period and layer strain [3,4]. It was shown that the new material has anisotropic carrier dispersion: the carrier energy associated with the in-plane motion is proportional to the wave vector and characterized by the Fermi velocity vF, the dispersion corresponding to the motion in the growth direction is quadratic. Remarkably, the Fermi velocity in this system can be controlled by varying the overlap between electron and hole states in the superlattice [3]. We present a picture of modification of the energy spectrum due to variation of layer thicknesses, strain and composition of the SLs. The effects of dimensional quantization, tunneling and interface scattering on the SL band structure will be discussed. 1 - G. Belenky, D. Wang, Y. Lin, D. Donetsk
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NSLS-II Friday Lunchtime Seminar
"Recent progress on the electronic structure study of the heavy-fermion Ce-115 compounds"
Presented by Qiuyun Chen, Science and Technology on Surface Physics and Chemistry Laboratory, China
Friday, June 21, 2019, 12 pm
NSLS-II Bldg. 743 Room 156Hosted by: Ignace Jarrige
Here we performed a combined bulk-sensitive soft x-ray angle-resolved photoemission spectroscopy (ARPES) and Ce 4d-4f resonant ARPES studies of the three parent compounds of the Ce-115 system: CeCoIn5, CeRhIn5, and CeIrIn5. In CeCoIn5, we spectroscopically resolved the development of band hybridization and the Fermi surface expansion over a wide temperature region. Unexpectedly, the localized-to-itinerant transition occurs at surprisingly high temperatures, yet f electrons are still largely localized even at the lowest temperature. These findings point to an unanticipated role played by crystal field excitations in the strange metal behavior of CeCoIn5. In CeRhIn5, we have directly observed a weakly dispersive heavy quasiparticle band in this heavy fermion compound, whose f-electrons are considered most fully localized. Two of the three crystal-electric-field (CEF) split levels of the Ce 4f5/21 states have been observed at 2.5 and 10 meV above the Fermi energy, with distinctive symmetries. The hybridization mainly happens between these states and Rh 4d band near the Brillouin zone center, on the most three-dimensional Fermi pocket. Remarkably, the f electrons start to turn itinerant at the highest sampling temperature, 180 K, a high temperature scale that is known to be consistent with the CEF splitting. In this important heavy fermion compound with antiferromagnetic state, we paint a comprehensive picture of the dual nature of the f electrons. In CeIrIn5, we find similar behaviors of the f electrons with that of CeCoIn5, and the hybridization also starts at much higher temperature than Tk. We also provide the first experimental evidence for 4f7/21 splittings which, in CeIrIn5, split the octet into four doublets. Our results offer a comprehensive and in part, unanticipated experimental picture of the heavy fermion formation, setting the stage for understanding the emergent properties, including unconventional superconductivity, in this and related material
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NSLS-II Friday Lunchtime Seminar
"High resolution strain measurements and phase discrimination in solid solutions using X-Ray Diffuse Multiple Scattering (DMS)"
Presented by Gareth Nisbet, Diamond Light Source, United Kingdom
Friday, June 14, 2019, 12 pm
NSLS-II Bldg. 743 Room 156Hosted by: Ignace Jarrige
DMS is a new high resolution scattering technique which manifests as diffraction lines impinging on the detector plane, similar to Kikuchi lines or Kossel lines. I will explain how multiple intersections from coplanar and non-coplanar reflections can be used for phase discrimination in multi-phasic systems by following a simple reductive procedure. The methods will be demonstrated using data from complex PMN-PT and PIN-PMN-PT ferroelectric solid solutions. I will also show how convolutional neural networks are being applied to DMS data for phase discrimination.
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NSLS-II Friday Lunchtime Seminar
"Status and perspective of high-energy automotive batteries"
Presented by Richard Schmuch, University of Munster, Germany
Friday, June 7, 2019, 12:30 pm
NSLS-II Bldg. 743 Room 156Hosted by: Ignace Jarrige
This presentation gives an overview of the materials, performance requirements and cost of current automotive traction batteries based on Li-ion technology. It also includes important aspects related to electromobility, such as its sustainability and energy efficiency. As current Li-Ion batteries with intercalation-type active materials are approaching their physicochemical energy density limit of roughly 300 Wh/kg or 800 Wh/L, alternative technologies such as lithium-metal based all-solid-state batteries (ASSBs) currently intensively studied, which promise an energy density of up to 1000 Wh/L. The potential and challenges of this and other post Li-ion batteries (e.g. Dual-Ion, Mg-Ion, Li-Sulphur) are discussed and also compared by systematic bottom-up energy density calculations. Through a step-by-step analysis from theoretical energy content at the material level to practical energies at the cell level, the individual advantages and shortcomings of the studied battery types are elucidated. Literature: (1) Schmuch, R.; Wagner, R.; Hörpel, G.; Placke, T.; Winter, M. Performance and Cost of Materials for Lithium-Based Rechargeable Automotive Batteries. Nat. Energy 2018, 3 (4), 267–278. (2) Betz, J.; Bieker, G.; Meister, P.; Placke, T.; Winter, M.; Schmuch, R. Theoretical versus Practical Energy: A Plea for More Transparency in the Energy Calculation of Different Rechargeable Battery Systems. Adv. Energy Mater. 2018, 1803170, 1803170. (3) Placke, T.; Kloepsch, R.; Dühnen, S.; Winter, M. Lithium Ion, Lithium Metal, and Alternative Rechargeable Battery Technologies: The Odyssey for High Energy Density. J. Solid State Electrochem. 2017, 1–26. (4) Meister, P.; Jia, H.; Li, J.; Kloepsch, R.; Winter, M.; Placke, T. Best Practice: Performance and Cost Evaluation of Lithium Ion Battery Active Materials with Special Emphasis on Energy Efficiency. Chem. Mater. 2016, 28 (20), 7203-7217
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NSLS-II Friday Lunchtime Seminar
"Longitudinal Coupling Impedance and Single-Bunch Instability"
Presented by Alexei Blednykh, NSLS-II
Friday, June 7, 2019, 12 pm
NSLS-II Bldg. 743 Room 156Hosted by: Ignace Jarrige
Several instability thresholds and special waveform beam pattern have been observed during measurements of the electron beam energy spread σ_δ versus single-bunch current I_0 in NSLS-II. The experimental data have been collected from: the synchrotron light monitor (SLM) camera installed in a low dispersion area of the NSLS-II storage ring, the Full-Width Half-Maximum size of the In-Vacuum Undulator harmonic, the stripline kicker as a part of the bunch-by-bunch transverse feedback system and the large gap dipole chamber of Optical Extraction Beamline in NSLS-II. With mentioned measurement techniques we were able to confirm, that the microwave beam pattern behavior as a current dependent effect. The numerical simulations of the Vlasov-Fokker-Planck (VFP) equation with the longitudinal impedance budget simulated by the GdfidL code for a 0.3mm bunch length and the total longitudinal wakepotential W_(||,tot)(s), allowed us to reproduce the energy spread dependence on the single bunch current numerically for different lattices, bare lattice and regular operational lattice with all insertion devices magnet gap closed, including 3 damping wigglers. The present talk will be based on the results published in the Scientific Reports, 2018: A. Blednykh, B. Bacha, G. Bassi, W. Cheng, O. Chubar, A. Derbenev, R. Lindberg, M. Rakitin, V. Smaluk, M. Zhernenkov, Yu-chen Karen Chen-Wiegart and L. Wiegart, "New aspects of longitudinal instabilities in electron storage rings", Scientific Reports volume 8, Article number: 11918 (2018).
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NSLS-II Friday Lunchtime Seminar
"Microspectroscopy of Extraterrestrial Materials, or, The Universe Viewed Through a Microscope"
Presented by Paul Northrup, Stony Brook University
Friday, May 31, 2019, 12 pm
NSLS-II Bldg. 743 Room 156Hosted by: Ignace Jarrige
Synchrotron X-ray absorption fluorescence spectromicroscopy is an essential tool for characterization of heterogeneous (and often very small) extraterrestrial materials. A NASA-funded research program utilizes the TES (8-BM) and XFM (4-BM) to study composition and chemistry of extraterrestrial materials, especially focusing on return-mission samples. Of particular interest are Phosphorus and Sulfur compounds that may be either a) organic evidence of life, or b) precursors or critical raw materials for development of life, on early Earth or elsewhere. Initial samples include meteorites, interplanetary dust particles, and Lunar materials. Current sample-return missions (NASA OSIRIS REx and Japan's Hayabusa2) will retrieve material from distant asteroids in a few years. Future missions will return samples from Mars.
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NSLS-II Friday Lunchtime Seminar
"THz vortex beam as a spectroscopic probe of magnetic excitations"
Presented by Andrei A. Sirenko, New Jersey Institute of Technology, NJ
Friday, May 24, 2019, 12 pm
NSLS-II Bldg. 743 Room 156Hosted by: Ignace Jarrige
Circularly polarized light with spin angular momentum (SAM) is one of the most valuable probes of magnetism. We demonstrate that light beams with orbital angular momentum (OAM), or vortex beams, can also couple to magnetic excitations exhibiting dichroisms in a magnetized medium. In our recent experiments with coherent THz beams we observed that resonant optical absorption in a ferrimagnetic crystal of Dy3Fe5O12 depends strongly on both the handedness of the vortex and direction of the beam propagation with respect to the sample magnetization. This effect exceeds the conventional dichroism for conventional circularly polarized light. Our results demonstrate the potential of the vortex beams with OAM as a new spectroscopic probe of magnetism in matter. A possibility to convert synchrotron radiation at the 22-IR-2 MET beamline into a vortex beam and use it for materials spectroscopy will be also discussed in this talk. In collaboration with T. N. Stanislavchuk1, P. Marsik2, C. Bernhard2, V. Kiryukhin3, S-W. Cheong3, and G. L. Carr4 1 Department of Physics, New Jersey Institute of Technology, Newark, New Jersey 2 Department of Physics, University of Fribourg, Switzerland. 3 Rutgers Center for Emergent Materials and Department of Physics and Astronomy, Rutgers University 4 NSLS-II, Brookhaven National Lab
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NSLS-II Friday Lunchtime Seminar
"MAXPD: Multi-Anvil X-ray Powder Diffraction — COMPRES Partner User Program for High Pressure Studies at 28-ID-2-D"
Presented by Matthew L. Whitaker, Stony Brook University
Friday, May 17, 2019, 12 pm
NSLS-II Bldg. 743 Room 156Hosted by: Ignace Jarrige
MAXPD is the downstream endstation of XPD, an insertion device beamline at Sector 28 (28-ID-2-D) of NSLS-II. The MAXPD endstation and General User Program are sponsored by the COnsortium for Materials Properties Research in Earth Sciences (COMPRES). MAXPD has an 1100-ton hydraulic press installed, which is equipped with a unique DT-25 pressure module that can be swapped out for a more standard D-DIA module as desired. MAXPD makes use of the world-class monochromatic beam available at XPD (usually ~67 keV), with which we collect both angular dispersive X-ray diffraction data and X-radiographic imaging. The first General User experiments took place in March 2018. Final Science Commissioning beamtime took place in August of last year, and the full General User program for MAXPD began in the 2018-3 cycle. In this seminar, I will give an overview of the science drivers behind the development of the endstation, some of its unique capabilities, some representative results from recent experiments conducted over the last two cycles at MAXPD, and where we are looking to go as we look to the future.
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NSLS-II Friday Lunchtime Seminar
"Self-assembly of anisotropic nanocrystals from crystalline to quasicrystalline structures"
Presented by Ou Chen, Brown University, Rhode Island
Friday, May 10, 2019, 12 pm
NSLS-II Bldg. 743 Room 156Hosted by: Ignace Jarrige
Anisotropic nanocrystals with defined composition, shape and surface patchiness represent a unique class of building objects for constructing high-order architectural nanomaterials. When utilized in assembly, anisotropic nanocrystals can display strong asymmetric interactions induced by the patchiness that may complicate the formation of ordered structures compared to the assemblies of isotropic building blocks. In this talk, I will use several types of anisotropic 'patchy' nanocrystals as examples to demonstrate how they assemble into the unprecedented superstructures through the directional interactions among the building blocks under an enthalpy-driven condition. Both translational periodicities and orientational ordering of the final superstructural materials will be discussed. The dominating driving forces lead to the obtained architectures will be identified through molecular dynamics computer simulations and experimental results.
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NSLS-II Friday Lunchtime Seminar
"In situ studies of Zr-based MOFs for nerve-agents capture and decomposition"
Presented by Anna M. Plonka, Stony Brook University, Dept. of Mat. Sci. & Chem. Eng.
Friday, May 3, 2019, 12 pm
NSLS-II Bldg. 743 Room 156Hosted by: Ignace Jarrige
Effective filters for the rapid decomposition of chemical warfare agents (CWAs) are in high demand for protecting military and civilian populations. Although many new materials, such as metal-organic frameworks (MOFs), have been proposed to use as CWA filtration media, their eventual transition requires a detailed understanding of the atomic-scale reaction mechanisms. Zr-based MOFs were recently shown to be among the fastest catalysts of nerve-agent hydrolysis reaction in solution. We show the results of a detailed study of the adsorption and decomposition of a nerve-agent simulant, dimethyl methylphosphonate (DMMP), on Zr-based MOFs, that have different pore sizes and connectivities, using synchrotron-based X-ray powder diffraction, X-ray absorption and infrared spectroscopy, which reveals key aspects of the reaction mechanism. Further, we evaluate how battle-field contaminants such as CO2 can influence effective detoxification of CWAs by Zr-based MOF-808.
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NSLS-II Friday Lunchtime Seminar
"Coherent X-ray measurement of local step-flow propagation during growth of polycrystalline organic semiconductor thin films"
Presented by Randall Headrick, University of Vermont
Friday, April 26, 2019, 12 pm
NSLS-II Bldg. 743 Room 156Hosted by: Ignace Jarrige
Vacuum deposition of C60 on a graphene-coated surface is investigated with X-ray Photon Correlation Spectroscopy in surface-sensitive conditions. Local step-flow is observed through the observation of oscillatory correlations in the later stages of growth after crystalline mounds have formed. An important aspect of the work is that coherent X-rays do not average over complex structures, and this allows us to monitor the growth on polycrystalline surfaces without loss of information. The experimental results show that the step-flow velocity must be nonuniform, and we model the velocity of each step-edge as being a simple function of the lengths of the terraces above and below it. This model predicts that the steps become almost stationary near the edges of the mounds where the local terrace length is very small, and the average slope of the surface is large. It was not previously known that such nonuniform and disordered step arrays as we have observed would follow such a simple growth law. This work shows that the use of coherent X-ray scattering provides an approach to better understand surface dynamics and fluctuations during crystal growth.
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NSLS-II Friday Lunchtime Seminar
"Wireless Sensors, and updates to areaDetector with Computer Vision"
Presented by Kazimierz Gofron, NSLS-II
Friday, April 12, 2019, 12 pm
NSLS-II Bldg. 743 Room 156Hosted by: Ignace Jarrige
by K. Gofron, M. Rolland, J. Wlodek, The series of brief talks that concentrate on EPICS controls 1. Wireless sensors controlled from EPICS 2. Improvements to Area Detector at NSLS2 A. Low Energy, Low Cost: The Nordic Thingy:52 Sensor Suite 1. Wireless technologies 2. EPICS controls of wireless sensors 3. ioc components 4. Integrated into CSS, and clients B. Improvements to Area Detector deployment and features at NSLS2 1. ADPluginBar/Dmtx – QR Code and data matrix code readers for EPICS Area Detector 2. ADLambda – Adding new features to an existing driver, and updating to build on newer OS 3. ADCompVision – Bringing Computer Vision to Area Detector 4. ADUVC – An area detector driver for USB Video Class devices 5. ADEmergentVision – An area detector driver for Emergent Vision Technologies 10 GigE and 25 GigE cameras
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NSLS-II Colloquium
"NASA's Mars 2020 Mission – First Steps Towards Mars Sample Return"
Presented by Kenneth Farley, Caltech
Thursday, April 11, 2019, 4 pm
Large Seminar Room, Bldg. 510Hosted by: John Hill
Scientists have advocated for the return of samples from Mars for decades. The quest has finally begun in earnest: the Jet Propulsion Laboratory is in the final stages of construction of the Mars 2020 mission. Mars 2020 builds on the highly successful design of the Mars Science Laboratory (Curiosity Rover) and is updated with new landing capabilities, scientific instruments, and a very sophisticated rock sample collection system. Mars 2020's chief goals are to unravel the geology of its landing site, seek evidence of potential Martian biosignatures, and prepare a cache of several dozen samples for possible return to Earth by a future element of a notional Mars Sample Return campaign. NASA recently selected the mission's destination: Jezero Crater. This crater once held a very deep lake comparable in size to Lake Tahoe. Key geologic targets at the site include ancient Martian bedrock, lake sediments and especially a remarkably preserved river delta, and unusual carbonate-bearing rocks possibly precipitated from lake-water. Mars 2020 will launch in the summer of 2020, land on February 18, 2021, and rove the surface for at least two years. I am Project Scientist for Mars 2020 and will describe the goals and development of this mission, and of Mars sample return.
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NSLS-II Friday Lunchtime Seminar
"Towards studying dynamics over 18 decades with correlation spectroscopy – first XPCS results from European XFEL"
Presented by Felix Lehmkuehler, Coherent X-ray Scattering Group, DESY, Germany
Friday, April 5, 2019, 12 pm
NSLS-II Bldg. 743 Room 156Hosted by: Ignace Jarrige
Many phenomena in soft matter physics and biology happen on microsecond timescales, e.g., folding kinetics of proteins, where the time scale is basically defined by the protein size. Despite of the importance of such processes, μs time scales are very difficult to access in X-ray scattering experiments at storage rings as well as in quasi-elastic neutron scattering. The time structure of the European XFEL with MHz pulse repetition rate in a bunch train enables for the first time structural studies of dynamics and kinetics at such time scales. A method to investigate such phenomena is X-ray photon correlation spectroscopy (XPCS), tracking changes of the coherent diffraction pattern, the so-called speckle pattern, over time. XPCS has become a well-established technique at modern storage ring sources studying timescales ranging from several 1000 s down to milliseconds. At FEL sources, the higher average flux and superior degree of coherence allow the access to shorter timescales down to femtoseconds using split-pulse techniques. On the other hand, sequential-pulse XPCS is limited by the repetition rate of the FEL pulses, i.e. about 8 to 50 ms at normal-conducting hard X-ray FEL sources such as LCLS (USA) and SACLA (Japan). The high repetition rate of the European XFEL enables dynamics measurement on sub-μs time scales, which is otherwise difficult to achieve at storage ring, neutron, pump-probe or lab-based experiments. In this talk, first dynamics measurements at FEL sources using correlation techniques will be introduced and recent results on prototypical soft matter samples as well as fs dynamics of liquid water will be discussed. Afterwards, results from our recent XPCS experiment at European XFEL will be discussed, where we successfully performed measurements of (sub-)µs dynamics of soft matter samples. Furthermore, special attention is paid on shot-to-shot and train-to-train fluctuations of coherence and beam pointing obtained by c
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NSLS-II Friday Lunchtime Seminar
"X-ray holography correlation spectroscopy: How to probe stochastic dynamics on the nanoscale"
Presented by Christopher Klose, Max Born Institute, Berlin, Germany
Friday, March 29, 2019, 12:30 pm
NSLS-II Bldg 744 Rm 156Hosted by: Ignace Jarrige
Nanometer-scale spin configurations such as magnetic domains walls (DW) or skyrmions are attractive as information entities for spintronic applications as they can be generated and manipulated by electrical spin-polarized currents. Naturally, the function of such devices is crucially determined by the thermal stability of the magnetic configuration used for encoding the information. In our study, we have investigated thermally activated magnetic DW dynamics on timescales ranging from sub-seconds to hours under equilibrium conditions in a thin-film magnetic multilayer material based on 15 repetitions of Pt/CoFeB/MgO trilayers. Such multilayers were already successfully used to demonstrate the basic operation of a skyrmion-based racetrack memory [1]. For our investigations, we developed a new experimental approach combining real-space imaging via Fourier-transform holography [2] and x-ray photon correlation spectroscopy [3]. Both methods rely on detecting coherent far-field diffraction from a disordered sample —a pattern of magnetic up and down domains in our case. Magnetic contrast is achieved by tuning the wavelength of circularly polarized x-rays to the Co L3 absorption edge (1.6 nm). For slow timescales (> 3 min), the analysis is based on the difference of scattering patterns recorded with opposite x-ray helicity (Fig. 1a). On one hand, the Fourier inversion of this difference results in a real-space image of the domains in the field of view (FOV) defined by a circular optics mask on the sample (Fig. 1b). On the other hand, we use the difference as input for an adapted temporal correlation analysis. Already at slightly elevated temperatures (310 K), the resulting two-time correlation function of the magnetic configuration at times t1 and t2 (Fig. 1c) reveals time periods of high correlation, i.e., high stability interrupted by sudden extensive domain rearrangements as witnessed by the related images.
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NSLS-II Friday Lunchtime Seminar
"Can We Make X-ray CT More Universal?"
Presented by Jun Lim, Pohang Light Source-II, Korea, Republic of (South)
Friday, March 29, 2019, 12 pm
NSLS-II Bldg 744 Rm 156Hosted by: Ignace Jarrige
Full-field transmission x-ray microscope (TXM) based on Fresnel zone plate is a promising and intuitive manner to take high quality phase contrast images with spatial resolution of tens of nanometers, applicable to both synchrotron radiation and laboratory source. In particular, computed tomography (CT) using hard x-rays of high penetration depth provides a high-resolution 3D image. However, the small field of view (FOV) of ~10 microns provides only a very limited volume (~10-5 mm3) of information. It primarily limits the application area of TXM. In this talk, I present a new type of TXM for CT that enlarge the FOV as large as diameter of the objective zone plate. With this method, sub-millimeter FOV can be realized while maintaining the nano-scale spatial resolution. Through experiment, we obtain more than 1000 times more volume (~10-2 mm3) of information than a typical TXM, at ~200 nm resolution. Its general applicability is demonstrated with integrated chips and Artemia cysts. We believe that this type of TXM can be particularly useful for industrial sample analysis where bulk properties are important.
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NSLS-II Friday Lunchtime Seminar
"Selective Catalytic Olefin Epoxidation with MnII-exchanged MOF-5"
Presented by Amanda Stubbs, MIT, Functional Inorganic & Organic Materials
Friday, March 22, 2019, 9:30 am
NSLS-II Bldg. 743 Room 156Hosted by: Ignace Jarrige
Partial substitution of ZnII by MnII in Zn4O-(terephthalate)3 (MOF-5) leads to a distorted all-oxygen ligand field supporting a single MnII site, whose structure was confirmed by Mn K-edge X-ray absorption spectroscopy. The MnII ion at the MOF-5 node engages in redox chemistry with a variety of oxidants. With tBuSO2PhIO, it produces a putative MnIV-oxo intermediate, which upon further reaction with adventitious hydrogen is trapped as a MnIII−OH species. Most intriguingly, the intermediacy of the high-spin MnIV−oxo species is likely responsible for catalytic activity of the MnII-MOF-5 precatalyst, which in the presence of tBuSO2PhIO catalyzes oxygen atom transfer reactivity to form epoxides from cyclic alkenes with >99% selectivity. These results demonstrate that MOF secondary building units serve as competent platforms for accessing terminal high-valent metal−oxo species that consequently engage in catalytic oxygen atom transfer chemistry owing to the relatively weak ligand fields provided by the SBU.
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NSLS-II Friday Lunchtime Seminar
"Results to date on the elimination of Insertion Device Motion control problems by the NSLS-II Insertion device working group"
Presented by John Escallier, NSLS-II
Friday, March 15, 2019, 12 pm
NSLS-II Bldg. 744 Room 156Hosted by: Ignace Jarrige
Control of Insertion Device gap motion by the use of the Delta Tau control platform requires a good understanding of several disciplines simultaneously. Physics, magnetics, mechanics, electronics, software, and control theory are all specialties needed to establish full control of the gaps. The ID working group is comprised of individuals who specialize in one or more of these disciplines, and have been quite successful at attacking and solving multiple issues related to the IVU devices. Improvements in accuracy and control have exceeded close to two orders of magnitude, while simultaneously keeping focus towards the eventual use of step and fly scanning of the gap in synchronous motion with other devices. As work on the first vendor's devices begins to ramp to completion, the group effort is being directed towards work on EPU's. This seminar will detail several of the problems encountered, how they were solved, and where the future lies.
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NSLS-II Colloquium
"Challenges of Future Very Short Wavelength X-ray Free-Electron Lasers"
Presented by Bruce Eric Carlsten, Los Alamos National Laboratory
Thursday, March 14, 2019, 4 pm
Large Seminar Room, Bldg. 510Hosted by: John Hill
Future X-ray Free-Electron Lasers (XFELs) will produce coherent X-rays with energies greater than 20 keV, which will require electron beams with lower laboratory emittances and relative energy spreads than those in current XFELs such as LCLS or the European XFEL. To satisfy this requirement, electron beam energies will need to be higher than in current XFEL designs if conventional accelerator architectures are used, leading to increased construction and operation costs. To provide design margin for these future XFELs at the lowest possible electron beam energies, novel schemes may be employed to suppress or eliminate the present limitations in XFEL performance. This talk will describe the dominant electron-beam instabilities and other effects (coherent synchrotron radiation, undulator resistive wall wakes, microbunch instability, and intrabeam scattering) and will describe a novel accelerator architecture to suppress the worst effects from them. Design trades to improve performance at lower beam energies will also be described. The baseline parameters for the proposed XFEL at Los Alamos (the MaRIE XFEL, designed to have an X-ray energy of 42 keV) will be used to illustrate these effects.
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NSLS-II Friday Lunchtime Seminar
"Dynamic Investigations of functional proteins using synchrotron radiation and gold nano-crystals at SPring-8"
Presented by Hiroshi Sekiguchi, SPring8, Japan
Friday, March 8, 2019, 12:30 pm
NSLS-II Bldg. 743 Room 156Hosted by: Ignace Jarrige
In addition to the static crystallographic information regarding a 3D structure of proteins, dynamic information regarding a protein's conformational changes would be helpful in elucidating the molecular mechanisms that regulate protein functions, such as ion channel gating and ligand-induced receptor activation. Such local and dynamic information can be obtained using optical microscopy with recently developed single molecule techniques, and we think that the technique with synchrotron X-rays would be more powerful technique because of its brilliance, its short wavelength of light, and its transparency. Small-angle X-ray scattering (SAXS) is one of well-established technique to investigate the nanoscale structure of protein under physiological conditions and structural changes in response to various external conditions and we have probed a compact intermediate state of calmodulin in the process of target binding [1,2] etc. And we have proposed a single molecule technique that utilizes synchrotron X-rays to monitor the internal motions of a single protein. We call it diffracted X-ray tracking (DXT) and it can detect atomic-scale dynamic motion of the protein at the single molecular level with several tens of microseconds time resolution [3]. In DXT, a target protein is labeled with a nanocrystal with a size of several tens of nanometers and the motions of the nanocrystal coupled with the protein's motions are recorded as the trajectories of diffraction spots from the nanocrystal [4-6]. At the seminar, we will present recent progress of such investigation for biomolecules at SPring-8 [7].
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NSLS-II Friday Lunchtime Seminar
"A "coherent" picture of (some) Quantum Materials"
Presented by Claudio Mazzoli, BNL / NSLS-II
Friday, March 8, 2019, 12 pm
NSLS-II Bldg. 743 Room 156Hosted by: Ignace Jarrige
Quantum Materials are attracting an increasing level of attention in order to understand and fully exploit their peculiar properties for innovative potential applications. The investigation of their relevant electronic phases, their dynamics and their coherence length scales is key to produce a consistent microscopic picture of their functionalities and response to external stimuli. In my talk, I will present some recent investigation on quantum materials performed at CSX (23-ID-1), focusing on their electronic order parameters and interactions, inhomogeneity and time evolution. Examples will include charge ordering in cuprate HTSC, magnetic ordering in artificial patterned samples and nickelates, exotic magnetic phases in multilayers.
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NSLS-II Friday Lunchtime Seminar
"Non-magnetic gap in the topological insulators"
Presented by Turgut Yilmaz, NSLS-II
Friday, March 1, 2019, 12 pm
NSLS-II Bldg. 743 Room 156Hosted by: Ignace Jarrige
In this talk, I will introduce the electronic structure of Cr-doped Bi2Se3 / pristine Bi2Se3 heterostructure grown by molecular beam epitaxial method. We realized that such heterostructure provides sharper electronic states in angle resolved photoemission experiments. This promotes a new strategy to study the impact of impurities on the surface states of topological insulators. Furthermore, I will show that the apparent gap at the Dirac point of topological insulators in the non-magnetic state is indeed formed by the resonant states. We confirm this by performing the first principle band structure calculation and angle resolved photoemission spectroscopy with on and off-resonant photon energies.
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NSLS-II Friday Lunchtime Seminar
"Formation and dynamics of organo-mineral associations in redoximorphic soils"
Presented by Selina Tenzer, University of Hohenheim, Germany
Friday, February 22, 2019, 12 pm
NSLS-II Bldg. 743 Room 156Hosted by: Ignace Jarrige
Dissolved soil organic matter (SOM) hinders the crystal growth of Fe and Mn oxides but promotes the formation of metal-OM complexes. The strength of the interactions between SOM and the Fe(O,OH)6-octahedra depends, besides pH and ionic strength, on the available functional groups. We investigate the formation of oxides under alternating redox conditions in the presence of two isotopically labelled organic model substances: vanillin (lignin component with a reactive phenol group) and alanine (amino acid with a carboxyl and an amino group). Combining XRF, µXANES and µXRD at 5-ID will allow to identify Fe and Mn oxides, describe their crystallinity and estimate the importance of organic forms of Fe and Mn. Later, we will study the spatial distribution of vanillin and alanine across mineral surfaces by NanoSIMS.
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NSLS-II Friday Lunchtime Seminar
"Magneto-electric waves in f-electron magnets"
Presented by Nicolas Gauthier, Stanford University & SLAC
Friday, February 15, 2019, 12 pm
NSLS-II Bldg. 743 Room 156Hosted by: Ignace Jarrige
The intertwining of electric, magnetic and structural degrees of freedom in materials is at the heart of novel strongly correlated phases such as magnetoelectric multiferoicity, superconductivity and heavy fermion ground states. Isolating the contributions of di erent degrees of freedom and characterizing their interplay are fundamental aspects to understand such unconventional phases. The multipolar expansion of the electronic conguration provides a powerful framework to attain this objective. As an example, I will present how we can reveal the role of electric quadrupole moments by measuring magnetic dipolar waves with neutron scattering in the frustrated magnet SrDy2O4. Our results indicate that electric e ects of the 4f-electrons can dominate over the magnetism in insulators and this encourages a reassessment of the description of rare-earth based magnets with unconventional properties.
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NSLS-II Collquium
"Resonant x-ray scattering from soft materials as a probe of molecular orientation fluctuations at the nanoscale"
Presented by Noel A. Clark, University of Colorado, Boulder
Thursday, February 14, 2019, 4 pm
Large Seminar Room, Bldg. 510Hosted by: John Hill
Orientation fluctuations are ubiquitous features of soft materials on length scales ranging from nanometers in the rotational dynamics of single molecules, to the macroscopic deformation of local orientational order in liquid crystals, polymers, and biomaterials. Here we present the application of depolarized resonant soft x-ray scattering (DRSoXS) as a selective probe of molecular orientation fluctuations at the nanoscale. This technique is demonstrated by determination of the wavevector spectrum of thermally generated collective reorientations in a nematic liquid crystal using Carbon K??-edge resonant scattering (incident wavelength = 4.4nm). DRSOXS uniquely reveals transient, short-range heliconical molecular assemblies and their pretransitional development, as ordering into a chiral three-dimensional helical state is approached.
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NSLS-II Friday Lunchtime Seminar
"Rechargeable Sodium-Ion Batteries"
Presented by Kyung-Wan Nam, Dongguk University, Seoul, Korea, Republic of (South)
Friday, February 8, 2019, 12 pm
NSLS-II Bldg. 743 Room 156Hosted by: Ignace Jarrige
Rechargeable sodium-ion batteries (SIBs) are now attracting special attention with a great cost advantage over rechargeable lithium-ion batteries (LIBs) especially in the field of large-scale applications. For the successful development of the SIBs, it is imperative to find new cathode and anode materials with high capacity, high power, and long cycle life. With this perspective, we have examined the electrochemical properties of O3-layer structured oxides, Na3M(II)2M(V)O6, with a honeycomb ordering of M(II) and M(V) in the metal layer for the cathode material in SIBs.[1] One of this class materials, Na3Ni2BiO6, can reversibly deliver specific discharge capacities of up to 109 mAh/g with very flat voltage plateaus ~3.5V vs. Na/Na+. Structural changes occurring during charging/discharging investigated by using in situ X-ray diffraction (XRD) are correlated with its long cycle life. Long and short-range structure changes at various state of (dis)charge have been also probed ex-situ using combined synchrotron-based high-resolution X-ray powder diffraction (HRPD) and extended X-ray absorption fine structure (EXAFS). Some of its derivatives with increased redox voltages will also be presented. For the anode materials, various compositions of transition metal oxides including Ti and Fe elements having tunnel based structures (single- and double- tunnels) are explored as rechargeable SIBs.[2] Detailed electrochemical results combined with structural characterization will be presented in the seminar. References: [1] D.S. Bhange, G. Ali, D.-H. Kim, D.A. Anang, T.J. Shin, M.G. Kim, Y.-M. Kang, K.Y. Chung, K.-W. Nam, J. Mat. Chem. A 5 (2017) 1300-1310. [2] D.S. Bhange, G. Ali, J.-Y. Kim, K. Y. Chung, K.-W. Nam, J. Power Sources 366 (2017) 115-122.
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NSLS-II Friday Lunchtime Seminar
"Phase Transition Kinetics of Close-Packed Block Copolymer Micelles"
Presented by Sangwoo Lee, Rensselaer Polytechnic Institute, Troy, NY
Friday, February 1, 2019, 12 pm
NSLS-II Bldg. 743 Room 156Hosted by: Ignace Jarrige
In the past decades, the structures of spherical particle packing have been intensively investigated to understand the origin of materials structures and associated properties. However, despite its equal importance, the phase transformation kinetics of spherical particles has been relatively poorly understood. We investigated close-packed structures of spherical block copolymer micelles induced by rapid cooling of disordered micelles using small angle X-ray scattering experiments conducted at the 11-CMS and 12-SMI lines. We found that depending on the depth of quenching, disordered block copolymer micelles self-assemble into three different close-packed structures: face-centered cubic (fcc), random stacking of hexagonal-close packed layers (rhcp), and hexagonal-close-packed (hcp) structures as the depth of temperature quenching increases. Cooling and heating of these close-packed micelle solutions reveal that the hcp and rhcp structures are long-lasting metastable structures that eventually transform to stable fcc. Close-inspection of the 2D small angle X-ray scattering patterns shows that the formation of these metastable structures is correlated with the size of crystallites. The Laplace pressure is attributed to the origin of the formation of the metastable structures.
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