E02-JEM ARM 300CF
|
Diamond Proposal Number(s):
[20198]
Open Access
Abstract: Intentionally disordered metal–organic frameworks (MOFs) display rich functional behaviour. However, the characterisation of their atomic structures remains incredibly challenging. X-ray pair distribution function techniques have been pivotal in determining their average local structure but are largely insensitive to spatial variations in the structure. Fe-BTC (BTC = 1,3,5-benzenetricarboxylate) is a nanocomposite MOF, known for its catalytic properties, comprising crystalline nanoparticles and an amorphous matrix. Here, we use scanning electron diffraction to first map the crystalline and amorphous components to evaluate domain size and then to carry out electron pair distribution function analysis to probe the spatially separated atomic structure of the amorphous matrix. Further Bragg scattering analysis reveals systematic orientational disorder within Fe-BTC’s nanocrystallites, showing over 10° of continuous lattice rotation across single particles. Finally, we identify candidate unit cells for the crystalline component. These independent structural analyses quantify disorder in Fe-BTC at the critical length scale for engineering composite MOF materials.
|
May 2023
|
|
B16-Test Beamline
DIAD-Dual Imaging and Diffraction Beamline
E01-JEM ARM 200CF
E02-JEM ARM 300CF
I08-Scanning X-ray Microscopy beamline (SXM)
I12-JEEP: Joint Engineering, Environmental and Processing
I13-1-Coherence
I13-2-Diamond Manchester Imaging
I14-Hard X-ray Nanoprobe
|
Open Access
Abstract: Hard dental tissues possess a complex hierarchical structure that is particularly evident in enamel, the most mineralised substance in the human body. Its complex and interlinked organisation at the Ångstrom (crystal lattice), nano-, micro-, and macro-scales is the result of evolutionary optimisation for mechanical and functional performance: hardness and stiffness, fracture toughness, thermal, and chemical resistance. Understanding the physical–chemical–structural relationships at each scale requires the application of appropriately sensitive and resolving probes. Synchrotron X-ray techniques offer the possibility to progress significantly beyond the capabilities of conventional laboratory instruments, i.e., X-ray diffractometers, and electron and atomic force microscopes. The last few decades have witnessed the accumulation of results obtained from X-ray scattering (diffraction), spectroscopy (including polarisation analysis), and imaging (including ptychography and tomography). The current article presents a multi-disciplinary review of nearly 40 years of discoveries and advancements, primarily pertaining to the study of enamel and its demineralisation (caries), but also linked to the investigations of other mineralised tissues such as dentine, bone, etc. The modelling approaches informed by these observations are also overviewed. The strategic aim of the present review was to identify and evaluate prospective avenues for analysing dental tissues and developing treatments and prophylaxis for improved dental health.
|
Apr 2023
|
|
E02-JEM ARM 300CF
|
Diamond Proposal Number(s):
[18770]
Open Access
Abstract: A Twinning Induced Plasticity (TWIP) steel with a nominal composition of Fe-16.4Mn-0.9C-0.5Si-0.05Nb-0.05V was deformed to an engineering strain of 6%. The strain around the deformation twins were mapped using the 4D-STEM technique. Strain mapping showed a large average elastic strain of approximately 6% in the directions parallel and perpendicular to the twinning direction. However, the large average strain comprised of several hot spots of even larger strains of up to 12%. These hot spots could be attributed to a high density of sessile Frank dislocations on the twin boundary and correspond to shear stresses of 1–1.5 GPa. The strain and therefore stress fields are significantly larger than other materials known to twin and are speculated to be responsible for the early thickness saturation of TWIP steel nanotwins. The ability to keep twins extremely thin helps improve grain fragmentation, i.e. the dynamic Hall-Petch effect, and underpins the large elongations and strain hardening rates in TWIP steels.
|
Apr 2023
|
|
E02-JEM ARM 300CF
|
William J.
Cull
,
Stephen T.
Skowron
,
Ruth
Hayter
,
Craig T.
Stoppiello
,
Graham A.
Rance
,
Johannes
Biskupek
,
Zakhar R.
Kudrynskyi
,
Zakhar D.
Kovalyuk
,
Christopher S.
Allen
,
Thomas J.
Slater
,
Ute
Kaiser
,
Amalia
Patanè
,
Andrei N.
Khlobystov
Diamond Proposal Number(s):
[25251]
Open Access
Abstract: Indium selenides (InxSey) have been shown to retain several desirable properties, such as ferroelectricity, tunable photoluminescence through temperature-controlled phase changes, and high electron mobility when confined to two dimensions (2D). In this work we synthesize single-layer, ultrathin, subnanometer-wide InxSey by templated growth inside single-walled carbon nanotubes (SWCNTs). Despite the complex polymorphism of InxSey we show that the phase of the encapsulated material can be identified through comparison of experimental aberration-corrected transmission electron microscopy (AC-TEM) images and AC-TEM simulations of known structures of InxSey. We show that, by altering synthesis conditions, one of two different stoichiometries of sub-nm InxSey, namely InSe or β-In2Se3, can be prepared. Additionally, in situ AC-TEM heating experiments reveal that encapsulated β-In2Se3 undergoes a phase change to γ-In2Se3 above 400 °C. Further analysis of the encapsulated species is performed using X-ray photoelectron spectroscopy (XPS), thermogravimetric analysis (TGA), energy dispersive X-ray analysis (EDX), and Raman spectroscopy, corroborating the identities of the encapsulated species. These materials could provide a platform for ultrathin, subnanometer-wide phase-change nanoribbons with applications as nanoelectronic components.
|
Mar 2023
|
|
E01-JEM ARM 200CF
E02-JEM ARM 300CF
I20-Scanning-X-ray spectroscopy (XAS/XES)
|
Runjia
Lin
,
Liqun
Kang
,
Karolina
Lisowska
,
Weiying
He
,
Siyu
Zhao
,
Shusaku
Hayama
,
Dan
Brett
,
Graham
Hutchings
,
Furio
Corà
,
Ivan
Parkin
,
Guanjie
He
Diamond Proposal Number(s):
[29254, 29207]
Open Access
Abstract: Electrocatalytic oxygen reduction reaction (ORR) has been intensively studied for efficient and environmentally benign energy conversion processes. However, insufficient understanding of ORR 2e--pathway mechanism at the atomic level inhibits rational design of electrocatalysts with both high activity and selectivity, causing concerns including catalyst degradation due to Fenton reaction or poor efficiency of H2O2 electrosynthesis. Herein we show that the generally accepted ORR electrocatalyst design based on a Sabatier volcano plot argument optimises activity but is unable to account for the 2e--pathway selectivity; an extended “dynamic active site saturation” model that examines in addition the hydrogenation kinetics linked to the OOH* adsorption energy enables us to resolve the activity-selectivity compromise. Through electrochemical and operando spectroscopic studies on the ORR process governed by a series of Co-N x /carbon nanotube hybrids, a construction-driven approach that aims to create the maximum number of 2e- ORR sites by directing the secondary ORR electron transfer step towards the 2e- intermediate is proven to be attainable by manipulating O2 hydrogenation kinetics. Control experiments reveal the O2 hydrogenation chemistry is related to a catalyst reconstruction with lower symmetry around the Co active centre induced by the application of a cathodic potential. The optimised catalyst exhibits a ~100% H2O2 selectivity and an outstanding activity with an ORR potential of 0.82 V versus the reversible hydrogen electrode to reach the ring current density of 1 mA cm-2 by using rotating ring-disk electrode measurement, which is the best-performing 2e- ORR electrocatalyst reported to date, and approaches the thermodynamic limit.
|
Mar 2023
|
|
E02-JEM ARM 300CF
|
Diamond Proposal Number(s):
[23285]
Abstract: The ability to control the in-plane magnetic anisotropy of a thin film is important for magnetic device applications. One way of accomplishing this task is by glancing angle deposition (GLAD). In this study, thin Co layers have been deposited using GLAD magnetron sputtering on MgO(001) and MgO(110) substrates. For Co films on MgO(001), the in-plane anisotropy direction can be directly controlled via the deposition angle. In contrast, for Co on MgO(110), the anisotropy due to the deposition angle is competing with the anisotropy induced by the substrate, while the growth parameters determine which contribution dominates. On the other hand, while on MgO(001) the deposition angle as well as the film thickness affect the strength of the Co in-plane anisotropy, no influence of these parameters on the magnetic properties is found for films on MgO(110).
|
Mar 2023
|
|
B07-B-Versatile Soft X-ray beamline: High Throughput
E02-JEM ARM 300CF
|
Longxiang
Liu
,
Liqun
Kang
,
Arunabhiram
Chutia
,
Jianrui
Feng
,
Martyna
Michalska
,
Pilar
Ferrer
,
David
Grinter
,
Georg
Held
,
Yeshu
Tan
,
Fangjia
Zhao
,
Fei
Guo
,
David
Hopkinson
,
Christopher
Allen
,
Yanbei
Hou
,
Junwen
Gu
,
Ioannis
Papakonstantinou
,
Paul
Shearing
,
Dan
Brett
,
Ivan P.
Parkin
,
Guanjie
He
Diamond Proposal Number(s):
[29340, 32501, 30614, 29809, 32058]
Open Access
Abstract: The electrochemical synthesis of hydrogen peroxide (H2O2) via a two-electron (2e-) oxygen reduction reaction (ORR) process provides a promising alternative to replace the energy-intensive anthraquinone process. However, the development of efficient electrocatalysts is still facing lots of challenges like insufficient understanding of active sites. Herein, we develop a facile template-protected strategy to synthesize a highly active quinone-rich porous carbon catalyst (PCC) for H2O2 electrochemical production. The optimized PCC900 exhibits unprecedented activity and selectivity, of which the onset potential reaches 0.83 V vs. reversible hydrogen electrode in 0.1 M KOH and the H2O2 selectivity is over 95 % in a wide potential range. Comprehensive synchrotron-based near-edge X-ray absorption fine structure (NEXAFS) spectroscopy combined with electrocatalytic characterizations reveals the positive correlation between quinone content and 2e- ORR performance. The effectiveness of chair-form quinone groups as the most efficient active sites is highlighted by the molecule-mimic strategy and theoretical analysis.
|
Mar 2023
|
|
E02-JEM ARM 300CF
|
Diamond Proposal Number(s):
[25427, 23814]
Open Access
Abstract: We describe nNPipe for the automated analysis of morphologically diverse catalyst materials. Automated imaging routines and direct-electron detectors have enabled the collection of large data stacks over a wide range of sample positions at high temporal resolution. Simultaneously, traditional image analysis approaches are slow and hence unsuitable for large data stacks and consequently, researchers have progressively turned towards machine learning and deep learning approaches. Previous studies often detail work on morphologically uniform material systems with clearly discernible features, limited workable image sizes and training data that may be biased due to manual labelling. The nNPipe data-processing method consists of two standalone convolutional neural networks that were exclusively trained on multislice image simulations and enables fast analysis of 2048 × 2048 pixel images. Inference performance compared between idealised and real industrial catalytic samples and insights derived from subsequent data analysis are placed into the context of an automated imaging scenario.
|
Feb 2023
|
|
E01-JEM ARM 200CF
E02-JEM ARM 300CF
|
Diamond Proposal Number(s):
[31082]
Abstract: Despite extensive efforts to develop high-performance H2 evolution catalysts, this remains a major challenge. Here, we demonstrate the use of Cd/Pt precursor solutions for significant photocatalytic H2 production (154.7 mmol g-1 h-1), removing the need for a pre-synthesized photocatalyst. In addition, we also report simultaneous in-situ synthesis of Pt single-atoms anchored CdS nanoparticles (PtSA-CdSIS) during photoirradiation. The highly dispersed in-situ incorporation of extensive Pt single atoms on CdSIS enables the enhancement of active sites and suppresses charge recombination, which results in exceptionally high solar-to-hydrogen conversion efficiency of ~1% and an apparent quantum yield of over 91% (365 nm) for H2 production. Our work not only provides a promising strategy for maximising H2 production efficiency but also provides a green process for H2 production and the synthesis of highly photoactive PtSA-CdSIS nanoparticles.
|
Feb 2023
|
|
E01-JEM ARM 200CF
E02-JEM ARM 300CF
I14-Hard X-ray Nanoprobe
I18-Microfocus Spectroscopy
|
Open Access
Abstract: Phyllosilicate minerals in the carbonaceous chondrites provide insights into processes in primitive parent bodies of the early Solar System. It is widely agreed that the CM- and CI-type carbonaceous chondrites underwent aqueous alteration on their parent bodies, resulting in phyllosilicate-rich matrices, where the dominant mineral phase is serpentine. There are many previous studies investigating phyllosilicate structure in carbonaceous chondrites, however, the presence of sulfur in these minerals and its effect on crystal lattice structure has not been studied in detail. We are investigating how the presence of sulfur (up to ≃9-10 wt% SO3) in serpentine phyllosilicate regions effects basal lattice spacing measurements of serpentine-like minerals in CM- and CI-type chondritic and related asteroidal material.
Four specimens are being studied for this work: Winchcombe and Aguas Zarcas (CM-type), and Ryugu samples (A0058-C2001-08, A0104-00200502 and A0104-01700602) from Hayabusa2 and Ivuna (CI-type). All samples are TEM wafers. We have used a multi-technique approach to study the samples, with the E01 JEOL ARM200CF and E02 JEOL ARM300CF electron microscopes at the ePSIC facility at Diamond Light Source in Harwell, UK. EDS compositional data has been collected using the E01 microscope, whilst HRTEM and HAADF imaging data has been collected at E02. At E02 we are also applying a new 4D-STEM nano-diffraction technique in order to collect lattice spacing data to correlate with our other HRTEM results. Fe-K XANES analyses on Winchcombe and Ryugu have been carried out using the I18 microprobe and I14 hard x-ray nanoprobe respectively, also at Diamond Light Source, to constrain Fe3+/ΣFe. By combining these techniques we aim to better understand the physical and chemical structure of serpentine-like minerals in carbonaceous chondrites.
Initial analyses have shown that sulfur presence in carbonaceous chondrite phyllosilicates reduces the basal lattice spacings of serpentine-like minerals. In these sulfur-bearing regions, we have been finding lattice spacings in the range ~0.60-0.74nm for the CM-type chondrites. For the CI-type, these range between ~0.65-0.76nm. Differences in the reduced lattice spacing ranges are likely related to the redox state of the sulfur. In Ryugu and other carbonaceous chondrites the sulfur appears reduced; its content in serpentine is low and we see FeS grains. Comparatively, in Winchcombe (and others) more of the sulfur seems to be in the serpentine structure.
We can conclude that in serpentine-like minerals, the presence of sulfur appears to reduce basal lattice spacing values compared to the expected d-spacing value of 0.70nm for serpentine. Possible reasons for this include further investigations into the valency of the sulfur ions, the bonding environment within serpentine layers, and the location of sulfur in either the octa- or tetrahedral lattice sites.
|
Feb 2023
|
|