E01-JEM ARM 200CF
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Ruoyu
Xu
,
Jingwei
Xiang
,
Junrun
Feng
,
Xuekun
Lu
,
Zhangxiang
Hao
,
Liqun
Kang
,
Ming
Li
,
Yunsong
Wu
,
Chun
Tan
,
Yiyun
Liu
,
Guanjie
He
,
Dan J. L.
Brett
,
Paul R.
Shearing
,
Lixia
Yuan
,
Yunhui
Huang
,
Feng Ryan
Wang
Diamond Proposal Number(s):
[17559, 19318, 19246, 20643]
Abstract: The lithium-sulfur (Li-S) batteries have high theoretical energy density, exceeding that of the lithium-ion batteries. However, their practical applications are hindered by the capacity decay due to lithium polysulfide shuttle effect and sulfur volume expansion. Here, we design a S@hollow carbon with porous shell/MnOx (S@HCS/MnOx) cathode to accommodate and immobilize sulfur and polysulfides, and develop a non-destructive technique X-ray computed tomography (X-ray CT) to in situ visualize the volume expansion of Li-S cathode. The designed cathode achieves a specific capacity of ~1100 mAh g-1 at 0.2 C with a fade rate of 0.18% per cycle over 300 cycles. The X-ray CT shows that only 16% volume expansion and 70% volume fraction of solid sulfur remaining in the S@HCS/MnOx cathode, superior to the commercial cathode with 40% volume expansion and 5% volume remaining of solid sulfur particles. This is the first reported visualization evidence for the effectiveness of hollow carbon structure in accommodating cathode volume expansion and immobilizing sulfur shuttling. X-ray CT can serve as a powerful in situ tool to trace the active materials and then feedback to the structure design, which helps develop efficient and reliable energy storage systems.
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Oct 2020
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I12-JEEP: Joint Engineering, Environmental and Processing
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Diamond Proposal Number(s):
[11204]
Abstract: The fracture resistance of load-bearing trabecular bone is adversely affected by diseases such as osteoporosis. However, there are few published measurements of trabecular bone fracture toughness due to the difficulty of conducting reliable tests in small specimens of this highly porous material. A new approach is demonstrated that uses digital volume correlation of X-ray computed tomographs to measure 3D displacement fields in which the crack shape and size can be objectively identified using a phase congruency analysis. The criteria for crack propagation, i.e. fracture toughness, can then be derived by finite element simulation, with knowledge of the elastic properties.
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Sep 2020
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I09-Surface and Interface Structural Analysis
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Diamond Proposal Number(s):
[21742]
Open Access
Abstract: Amorphous tin-gallium oxide (a-SGO) grown with atomic layer deposition was evaluated as a buffer layer in (Ag,Cu)(In,Ga)Se2 thin-film solar cells in search for a new material that is compatible with a variety of absorber band gaps. Hard and soft X-ray photoelectron spectroscopy on absorber/a-SGO stacks combined with J–V characterization of solar cells that were fabricated, showed that the conduction band alignment at the absorber/a-SGO interface can be tuned by varying the cation composition and/or growth temperature. Here, the surface band gap was 1.1 eV for the absorber. However, optical band gap data for a-SGO indicate that a suitable conduction band alignment can most likely be achieved even for wider absorber band gaps relevant for tandem top cells. A best efficiency of 17.0% was achieved for (Ag,Cu)(In,Ga)Se2/a-SGO devices, compared to η = 18.6% for the best corresponding CdS reference. Lower fill factor and open-circuit voltage values were responsible for lower cell efficiencies. The reduced fill factor is explained by a larger series resistance, seemingly related to interface properties, which are yet to be optimized. Some layer constellations resulted in degradation in fill factor during light soaking as well. This may partly be explained by light-induced changes in the electrical properties of a-SGO, according to analysis of Al/SGO/n-Si metal-oxide-semiconductor capacitors that were fabricated and characterized with J–V and C–V. Moreover, the introduction of a 1 nm thick Ga2O3 interlayer between the absorber and a-SGO improved the open-circuit voltage, which further indicates that the absorber/a-SGO interface can be improved.
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Sep 2020
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I15-1-X-ray Pair Distribution Function (XPDF)
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Diamond Proposal Number(s):
[22774]
Abstract: To understand the importance of the crystallite size on the stabilization of metastable tetragonal ZrO2, ultra-fine ZrO2 nanocrystallites were synthesized via: (i) the precipitation method in supercritical water using nitrate precursors, (ii) the sol-gel method in a supercritical ethanol-water mixture and (iii) the borderline non-hydrolytic sol-gel route in supercritical ethanol using propoxide precursors. The obtained nanocrystals displayed a variation of the monoclinic versus tetragonal molar frac-tions from 100 wt. % down to ≈ 10 wt. % of monoclinic. This variation was concomitant with an overall size decrease of the nanocrystals, ranging from 7 to 2 nm depending on the synthesis procedures. Phase contents were quantified by refinement analysis of X-ray scattering datasets, and crosschecked with Raman spectroscopy. Our results suggest that an upper limit of ≈ 90 wt. %, of tetragonal ZrO2 phase is possible, even for ultra-fine nanoparticles (2 nm). These findings thus question the exist-ence of any critical size limit below which stabilization of pure t-ZrO2 is attainable at low temperatures.
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Sep 2020
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I09-Surface and Interface Structural Analysis
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Jack E. N.
Swallow
,
Christian
Vorwerk
,
Piero
Mazzolini
,
Patrick
Vogt
,
Oliver
Bierwagen
,
Alexander
Karg
,
Martin
Eickhoff
,
Jörg
Schörmann
,
Markus R.
Wagner
,
Joseph William
Roberts
,
Paul R.
Chalker
,
Matthew J.
Smiles
,
Philip
Murgatroyd
,
Sara
Mohamed
,
Zachary W.
Lebens-higgins
,
Louis F. J.
Piper
,
Leanne A. H.
Jones
,
Pardeep K.
Thakur
,
Tien-lin
Lee
,
Joel B.
Varley
,
Juergen
Furthmüller
,
Claudia
Draxl
,
Tim D.
Veal
,
Anna
Regoutz
Diamond Proposal Number(s):
[21430, 24670]
Abstract: The search for new wide band gap materials is intensifying to satisfy the need for more advanced and energy effcient power electronic devices. Ga2O3 has emerged as an alternative to SiC and GaN, sparking a renewed interest in its fundamental properties beyond the main β-phase. Here, three polymorphs of Ga2O3, α, β, and ε, are investigated using X-ray diffraction, X-ray photoelectron and absorption spectroscopy, and ab initio theoretical approaches to gain insights into their structure - electronic structure relationships. Valence and conduction electronic structure as well as semi-core and core states are probed, providing a complete picture of the influence of local coordination environments on the electronic structure. State-of-the-art electronic structure theory, including all-electron density functional theory and many-body perturbation theory, provide detailed understanding of the spectroscopic results. The calculated spectra provide very accurate descriptions of all experimental spectra and additionally illuminate the origin of observed spectral features. This work provides a strong basis for the exploration of the Ga2O3 polymorphs as materials at the heart of future electronic device generations.
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Sep 2020
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I15-1-X-ray Pair Distribution Function (XPDF)
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Diamond Proposal Number(s):
[2257]
Open Access
Abstract: The use of silica as a lithium‐ion battery anode material requires a pretreatment step to induce electrochemical activity. The partially reversible electrochemical reduction reaction between silica and lithium has been postulated to produce silicon, which can subsequently reversibly react with lithium, providing stable capacities higher than graphite materials. Up to now, the electrochemical reduction pathway and the nature of the products were unknown, thereby hampering the design, optimization, and wider uptake of silica‐based anodes. Here, the electrochemical reduction pathway is uncovered and, for the first time, elemental silicon is identified as a reduction product. These insights, gleaned from analysis of the current response and capacity increase during reduction, conclusively demonstrated that silica must be reduced to introduce reversible capacity and the highest capacities of 600 mAh g−1 are achieved by using a constant load discharge at elevated temperature. Characterization via total scattering X‐ray pair distribution function analysis reveal the reduction products are amorphous in nature, highlighting the need for local structural methods to uncover vital information often inaccessible by traditional diffraction. These insights contribute toward understanding the electrochemical reduction of silica and can inform the development of pretreatment processes to enable their incorporation into next‐generation lithium‐ion batteries.
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Sep 2020
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I15-Extreme Conditions
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Diamond Proposal Number(s):
[18643]
Abstract: Alkali-silica reaction (ASR) causes severe degradation of concrete. The mechanical property of the ASR product is fundamental to the multiscale modeling of concrete behavior over the long term. Despite years of study, there is a lack of consensus regarding the structure and elastic modulus of the ASR product. Here, ASR products from both degraded field infrastructures and laboratory synthesis were investigated using high-pressure X-ray diffraction. The results unveiled the multiphase and metastable nature of ASR products from the field. The dominant phase undergoes permanent phase change via collapsing of the interlayer region and in-planar glide of the main layer, under pressure >2 GPa. The bulk moduli of the low- and high-pressure polymorphs are 27±3 and 46±3 GPa, respectively. The laboratory-synthesized sample and the minor phase in the field samples undergo no changes of phase during compression. Their bulk moduli are 35±2 and 76±4 GPa, respectively. The results provide the first atomistic-scale measurement of the mechanical property of crystalline ASR products.
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Aug 2020
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I06-Nanoscience
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Weiwei
Li
,
Bonan
Zhu
,
Ruixue
Zhu
,
Qiang
Wang
,
Ping
Lu
,
Yuanwei
Sun
,
Clodomiro
Cafolla
,
Zhimin
Qi
,
Aiping
Chen
,
Peng
Gao
,
Haiyan
Wang
,
Qing
He
,
Kelvin H. L.
Zhang
,
Judith L.
Macmanus‐driscoll
Diamond Proposal Number(s):
[17284]
Open Access
Abstract: Control of BO6 octahedral rotations at the heterointerfaces of dissimilar ABO3 perovskites has emerged as a powerful route for engineering novel physical properties. However, its impact length scale is constrained at 2–6 unit cells close to the interface and the octahedral rotations relax quickly into bulk tilt angles away from interface. Here, a long‐range (up to 12 unit cells) suppression of MnO6 octahedral rotations in La0.9Ba0.1MnO3 through the formation of superlattices with SrTiO3 can be achieved. The suppressed MnO6 octahedral rotations strongly modify the magnetic and electronic properties of La0.9Ba0.1MnO3 and hence create a new ferromagnetic insulating state with enhanced Curie temperature of 235 K. The emergent properties in La0.9Ba0.1MnO3 arise from a preferential occupation of the out‐of‐plane Mn d 3z 2−r 2 orbital and a reduced Mn eg bandwidth, induced by the suppressed octahedral rotations. The realization of long‐range tuning of BO6 octahedra via superlattices can be applicable to other strongly correlated perovskites for exploring new emergent quantum phenomena.
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Aug 2020
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I22-Small angle scattering & Diffraction
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Open Access
Abstract: Bicontinuous cubic liquid crystalline phases of π‐conjugated molecules, representing self‐assembled 3D‐ordered interpenetrating networks with cubic symmetry, are receiving increasing attention due to their capacity for charge transport in all three dimensions and their inherent spontaneous helicity. Herein, a robust general design concept for creating bicontinuous cubic phases is reported. It is based on a nonsymmetric‐substituted π‐conjugated 5,5′‐diphenyl‐2,2′‐bithiophene platform with one end containing three out‐fanning flexible chains and with a range of substituents at the other end (the apex). The cubic phases are stable over broad temperature ranges, often down to ambient temperature, and tolerate a wide range of apex substitution patterns, allowing structural diversity and tailoring of the cubic phase type and application‐relevant properties. With an increasing number and size of apex substituents, a sequence of three different modes of cubic self‐assembly is observed, following an increasing helical twist. Thus, two ranges of the achiral double network Ia 3⎯⎯
3
¯
d phase range can be distinguished, a long pitch and a short pitch, with the chiral triple network I23 cubic phase in the intermediate pitch range. The findings provide a new prospect for the directed design of cubic phase‐forming functional materials based on spontaneously formed helical network liquid crystals with tunable application specific properties.
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Aug 2020
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I11-High Resolution Powder Diffraction
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Diamond Proposal Number(s):
[14809]
Abstract: Potassium-ion batteries (KIB) are a promising complementary technology to lithium-ion batteries because of the comparative abundance and affordability of potassium. Currently, the most promising KIB chemistry consists of a potassium manganese hexacyanoferrate (KMF) cathode, a Prussian blue analog, and a graphite anode (723Whl−1 and 359Whkg−1 at 3.6V). No electrolyte has yet been formulated that is concurrently stable at the high operating potential of KMF (4.02V vs K+/K) and compatible with K+ intercalation into graphite, currently the most critical hurdle to adoption. Here we combine a KMF cathode and a graphite anode with a KFSI in Pyr1,3FSI ionic liquid electrolyte for the first time and show unprecedented performance. We use high-throughput techniques to optimize the KMF morphology for operation in this electrolyte system, achieving 119 mA h g−1 at 4 V vs K+/K and a coulombic efficiency >99.3%. In the same ionic liquid electrolyte graphite shows excellent electrochemical performance and we demonstrate reversible cycling by operando XRD. These results are a significant and essential step forward towards viable potassium-ion batteries.
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Aug 2020
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