I13-1-Coherence
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Sebastian
Weber
,
Ken L.
Abel
,
Ronny T.
Zimmermann
,
Xiaohui
Huang
,
Jens
Bremer
,
Liisa K.
Rihko-struckmann
,
Darren
Batey
,
Silvia
Cipiccia
,
Juliane
Titus
,
David
Poppitz
,
Christian
Kübel
,
Kai
Sundmacher
,
Roger
Gläser
,
Thomas L.
Sheppard
Diamond Proposal Number(s):
[24079]
Open Access
Abstract: CO2 methanation is often performed on Ni/Al2O3 catalysts, which can suffer from mass transport limitations and, therefore, decreased efficiency. Here we show the application of a hierarchically porous Ni/Al2O3 catalyst for methanation of CO2. The material has a well-defined and connected meso- and macropore structure with a total porosity of 78%. The pore structure was thoroughly studied with conventional methods, i.e., N2 sorption, Hg porosimetry, and He pycnometry, and advanced imaging techniques, i.e., electron tomography and ptychographic X-ray computed tomography. Tomography can quantify the pore system in a manner that is not possible using conventional porosimetry. Macrokinetic simulations were performed based on the measures obtained by porosity analysis. These show the potential benefit of enhanced mass-transfer properties of the hierarchical pore system compared to a pure mesoporous catalyst at industrially relevant conditions. Besides the investigation of the pore system, the catalyst was studied by Rietveld refinement, diffuse reflectance ultraviolet-visible (DRUV/vis) spectroscopy, and H2-temperature programmed reduction (TPR), showing a high reduction temperature required for activation due to structural incorporation of Ni into the transition alumina. The reduced hierarchically porous Ni/Al2O3 catalyst is highly active in CO2 methanation, showing comparable conversion and selectivity for CH4 to an industrial reference catalyst.
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Dec 2020
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E01-JEM ARM 200CF
E02-JEM ARM 300CF
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Jian
Guo
,
Liqun
Kang
,
Xuekun
Lu
,
Siyu
Zhao
,
Jianwei
Li
,
Paul R.
Shearing
,
Ryan
Wang
,
Dan J. L.
Brett
,
Guanjie
He
,
Guoliang
Chai
,
Ivan P.
Parkin
Diamond Proposal Number(s):
[22572, 20847]
Abstract: Developing cost-effective and durable air-cathodes is crucial for improving metal-air batteries. Most reports of cathode formulation involve preparing bi-functional electrocatalysts from wet chemistry or solid-state synthesis, followed by pasting onto a substrate. In this work, the cathodes generated from electrochemical activation of normal carbon paper substrates were directly used in Zn-air batteries. The self-activated carbon paper substrate without any additional electrocatalysts exhibits an impressive cycling stability (more than 165 hours for 1,000 cycles) and a small discharge-charge voltage gap. After the activation, the maximum power density and electrochemical surface area were increased by over 40 and 1,920 times respectively. It is discovered that substrates after activation can be directly used as a cathode. The new method is scalable, inexpensive and produces near best in class performance. The mechanism behind this enhancement is due to the creation of oxygen functional groups within the cathode, which overcame slow kinetics, enhanced wettability and enabled optimum three-phase boundaries.
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Dec 2020
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I09-Surface and Interface Structural Analysis
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B. F.
Spencer
,
S.
Maniyarasu
,
B.
Reed
,
D. J. H.
Cant
,
R.
Ahumada-lazo
,
A. G.
Thomas
,
C. A.
Muryn
,
M.
Maschek
,
S. K.
Eriksson
,
T.
Wiell
,
T.-l.
Lee
,
S.
Tougaard
,
A. G.
Shard
,
W. R.
Flavell
Diamond Proposal Number(s):
[20059]
Abstract: Hard X-ray Photoelectron Spectroscopy (HAXPES) provides minimally destructive depth profiling into the bulk, extending the photoelectron sampling depth. Detection of deeply buried layers beyond the elastic limit is enabled through inelastic background analysis. To test the robustness of this technique, we present results on a thin (18 nm) layer of buried metal-organic complex buried below up to 200 nm of organic material. Overlayers with thicknesses 25-140 nm were measured using photon energies ranging 6-10 keV at the I09 end station at Diamond Light Source, and a new fixed energy Ga Kα (9.25 keV) laboratory-based HAXPES spectrometer was also used to measure samples with overlayers up to 200 nm thick. The sampling depth was varied: at Diamond Light Source by changing the photon energy, and in the lab system by performing angle-resolved measurements. For all the different overlayers and sampling depths, inelastic background modelling consistently provided thicknesses which agreed, within reasonable error, with the ellipsometric thickness. Relative sensitivity factors were calculated, and these factors consistently provided reasonable agreement with the expected nominal stoichiometry, suggesting the calculation method can be extended to any element. These results demonstrate the potential for the characterisation of deeply buried layers using synchrotron and laboratory-based HAXPES.
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Dec 2020
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I13-2-Diamond Manchester Imaging
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Diamond Proposal Number(s):
[23490]
Open Access
Abstract: The transient nature of the internal pore structure of particulate wall flow filters, caused by the continuous deposition of particulate matter, makes studying their flow and filtration characteristics challenging. In this article we present a new methodology and first experimental demonstration of time resolved in-situ synchrotron micro X-ray computed tomography (micro-CT) to study aerosol filtration. We directly imaged in 4D (3D plus time) pore scale deposits of TiO2
nanoparticles (nominal mean primary diameter of 25 nm) with a pixel resolution of 1.6 μ
m. We obtained 3D tomograms at a rate of ∼1 per minute. The combined spatial and temporal resolution allows us to observe pore blocking and filling phenomena as they occur in the filter’s pore space. We quantified the reduction in filter porosity over time, from an initial porosity of 0.60 to a final porosity of 0.56 after 20 min. Furthermore, the penetration depth of particulate deposits and filtration rate was quantified. This novel image-based method offers valuable and statistically relevant insights into how the pore structure and function evolves during particulate filtration. Our data set will allow validation of simulations of automotive wall flow filters. Evolutions of this experimental design have potential for the study of a wide range of dry aerosol filters and could be directly applied to catalysed automotive wall flow filters.
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Dec 2020
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B16-Test Beamline
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M.
Borri
,
C.
Cohen
,
O.
Fox
,
J.
Groves
,
W.
Helsby
,
O.
Mathon
,
L.
Mcnicholl
,
S.
Pascarelli
,
K.
Sawhney
,
R.
Torchio
,
M.
Zuvic
Diamond Proposal Number(s):
[24637]
Open Access
Abstract: Germanium micro-strip sensors were selected as the sensor technology to take data in energy dispersive X-ray spectroscopy experiments at the Extremely Brilliant Source (EBS) in Grenoble (FR). It is important for this experimental technique to use sensors with a large uniform area and a fine pitch. The former determines the range of energy detectable with a single sensor. The latter improves spectral resolution. A high stopping power is also important to perform studies with hard X-rays.
The device under test in this measurement was a germanium micro-strip sensor made of 1024 strips with
pitch. The bulk was 1.5 mm thick. The sensor was assembled into a prototype cryostat part of the XH detector system. The device was tested at the B16 beamline at the Diamond Light Source (DLS) in Didcot (UK). The objective of the test-beam was to characterise charge-sharing between strips. In fact, this effect limits the spectral resolution of the device.
To carry out this test, the sensor was scanned over a subset of strips with micro-focused X-rays under different settings. These were beam energy and intensity, sensor temperature and bias voltage. Results are presented in this paper. It was measured that the full width half maximum of the charge-sharing profile across different strips was
for settings which were indicative of the experimental conditions at the EBS. This was a signal current per unit area on the sensor of
10−8 A/
, a bias voltage of -180 V and a temperature of -159
C.
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Dec 2020
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Abstract: Electron microscopy is a powerful tool to study viral infection in the cellular context. A vast majority of our ultrastructural understanding of cellular infection has been acquired through imaging of chemically fixed, plastic embedded samples using traditional electron microscopy. Application of electron tomography to such specimens enables ultrastructural analysis of virus infection in three-dimensions. Advances in cryo-fixation and cryo-electron microscopy and tomography have allowed investigation of viruses in the cellular context under near-native frozen-hydrated conditions, pushing structural analysis to higher resolutions, especially when combined with sub-tomogram averaging of multiple copies of the repeating unit.
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Dec 2020
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I11-High Resolution Powder Diffraction
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Diamond Proposal Number(s):
[25186]
Abstract: We present a structural and magnetic study of two batches of polycrystalline LiNi0.8Mn0.1Co0.1O2 (commonly known as Li NMC 811), a Ni-rich Li ion battery cathode material, using elemental analysis, X-ray and neutron diffraction, magnetometry, and polarized neutron scattering measurements. We find that the samples, labeled S1 and S2, have the composition Li1–xNi0.9+x–yMnyCo0.1O2, with x = 0.025(2), y = 0.120(2) for S1 and x = 0.002(2), y = 0.094(2) for S2, corresponding to different concentrations of magnetic ions and excess Ni2+ in the Li+ layers. Both samples show a peak in the zero-field-cooled (ZFC) dc susceptibility at 8.0(2) K, but the temperature at which the ZFC and FC (field-cooled) curves deviate is substantially different: 64(2) K for S1 and 122(2) K for S2. The ac susceptibility measurements show that the transition for S1 shifts with frequency whereas no such shift is observed for S2 within the resolution of our measurements. Our results demonstrate the sample dependence of magnetic properties in Li NMC 811, consistent with previous reports on the parent material LiNiO2. We further establish that a combination of experimental techniques is necessary to accurately determine the chemical composition of next-generation battery materials with multiple cations.
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Dec 2020
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B23-Circular Dichroism
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Diamond Proposal Number(s):
[23955, 20441, 26447]
Open Access
Abstract: The first example of uniformly chiral thin films of silicon phthalocyanines (SiPcs) are reported. The local domains of the films are mapped using circular dichroism (CD) imaging (CDi) technique available at the Diamond B23 beamline. The CDi allowed us to increase the spatial resolution up to 525× when compared with benchtop spectrometers. The results indicate formation on-surface of chiral and stable supramolecular assemblies with homogenous distribution. Chemical functionalization and solvent choice for deposition allow controllable chiroptical properties to be obtained. The method and technique reported in this work could be applied to prepare and characterize a wide variety of chiral thin films.
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Dec 2020
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I15-Extreme Conditions
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Diamond Proposal Number(s):
[4631, 6707]
Abstract: High-pressure studies have been performed on the ε-form of the powerful explosive CL-20. Hydrostatic compression over the pressure range 0–12 GPa has been monitored using synchrotron X-ray powder diffraction. The potential effects of X-ray radiation damage were observed and circumvented through a follow-up compression study over the pressure range 0–7 GPa using neutron powder diffraction. This second study revealed smooth compression behavior, and the absence of any phase transitions. Intermolecular interaction energies as obtained using PIXEL calculations did not show any discontinuity upon the application of pressure. An isothermal equation of state has been determined, and the high-pressure response is supported by dispersion-corrected density functional theory calculations. Inelastic neutron scattering (experimental and simulated) spectra for the ε-form are in excellent agreement.
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Dec 2020
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I16-Materials and Magnetism
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Stephan
Geprags
,
Bjorn Erik
Skovdal
,
Monika
Scheufele
,
Matthias
Opel
,
Didier
Wermeille
,
Paul
Thompson
,
Alessandro
Bombardi
,
Virginie
Simonet
,
Stephane
Grenier
,
Pascal
Lejay
,
Gilbert Andre
Chahine
,
Diana Lucia
Quintero-castro
,
Rudolf
Gross
,
Danny
Mannix
Diamond Proposal Number(s):
[12770]
Abstract: We report on a comprehensive investigation of the effects of strain and film thickness on the structural and magnetic properties of epitaxial thin films of the prototypal
J
eff
=
1
/
2
compound
Sr
2
IrO
4
by advanced x-ray scattering. We find that the
Sr
2
IrO
4
thin films can be grown fully strained up to a thickness of 108 nm. By using x-ray resonant scattering, we show that the out-of-plane magnetic correlation length is strongly dependent on the thin film thickness, but independent of the strain state of the thin films. This can be used as a finely tuned dial to adjust the out-of-plane magnetic correlation length and transform the magnetic anisotropy from two-dimensional to three-dimensional behavior by incrementing film thickness. These results provide a clearer picture for the systematic control of the magnetic degrees of freedom in epitaxial thin films of
Sr
2
IrO
4
and bring to light the potential for a rich playground to explore the physics of
5
d
transition-metal compounds.
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Dec 2020
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