Charting the relationship between phase type-surface area-interactions between the constituent atoms and oxygen reduction activity of Pd–Cu nanocatalysts inside fuel cells by in operando high-energy X-ray diffraction

2017 ◽  
Vol 5 (16) ◽  
pp. 7355-7365 ◽  
Author(s):  
Yazan Maswadeh ◽  
Shiyao Shan ◽  
Binay Prasai ◽  
Yinguang Zhao ◽  
Zhi-Hui Xie ◽  
...  
Keyword(s):  
Oxygen Reduction ◽  
Surface Area ◽  
Structural Changes ◽  
High Energy ◽  
X Ray Diffraction ◽  
X Ray ◽  
Reduction Activity ◽  
Phase Type ◽  
In Operando ◽  
The Relationship

HE-XRD elucidates the link between structural changes of catalysts inside PEMFCs and the performance of PEMFCs.

Structural changes in titanium dioxide nanocrystals during plastic deformation

2005 ◽  
Vol 38 (5) ◽  
pp. 749-756 ◽  
Author(s):  
Ulrich Gesenhues
Keyword(s):  
Structural Changes ◽  
Crystal Size ◽  
Lower Layer ◽  
High Energy ◽  
Primary Crystal ◽  
X Ray Diffraction ◽  
X Ray ◽  
Transmission Electron ◽  
Hall Method ◽  
Means Of Transmission

The polygonization of 200 nm rutile crystals during dry ball-milling at 10gwas monitored in detail by means of transmission electron microscopy (TEM) and X-ray diffraction (XRD). The TEM results showed how to modify the Williamson–Hall method for a successful evaluation of crystal size and microstrain from XRD profiles. Macrostrain development was determined from the minute shift of the most intense reflection. In addition, changes in pycnometrical density were monitored. Accordingly, the primary crystal is disintegrated during milling into a mosaic of 12–35 nm pieces where the grain boundaries induce up to 1.2% microstrain in a lower layer of 6 nm thickness. Macrostrain in the interior of the crystals rises to 0.03%. The pycnometrical density, reflecting the packing density of atoms in the grain boundary, decreases steadily by 1.1%. The results bear relevance to our understanding of plastic flow and the mechanism of phase transitions of metal oxides during high-energy milling.

scholarly journals Structural Evolution in Wet Mechanically Alloyed Co-Fe-(Ta,W)-B Alloys

Metals ◽  
2021 ◽  
Vol 11 (5) ◽  
pp. 800
Author(s):  
Vladimír Girman ◽  
Maksym Lisnichuk ◽  
Daria Yudina ◽  
Miloš Matvija ◽  
Pavol Sovák ◽  
...  
Keyword(s):  
Structural Changes ◽  
Magnetic Measurements ◽  
Structural Evolution ◽  
High Energy ◽  
Control Agent ◽  
X Ray Diffraction ◽  
Mechanically Alloyed ◽  
X Ray ◽  
Transmission Electron ◽  
X Ray Absorption

In the present study, the effect of wet mechanical alloying (MA) on the glass-forming ability (GFA) of Co43Fe20X5.5B31.5 (X = Ta, W) alloys was studied. The structural evolution during MA was investigated using high-energy X-ray diffraction, X-ray absorption spectroscopy, high-resolution transmission electron microscopy and magnetic measurements. Pair distribution function and extended X-ray absorption fine structure spectroscopy were used to characterize local atomic structure at various stages of MA. Besides structural changes, the magnetic properties of both compositions were investigated employing a vibrating sample magnetometer and thermomagnetic measurements. It was shown that using hexane as a process control agent during wet MA resulted in the formation of fully amorphous Co-Fe-Ta-B powder material at a shorter milling time (100 h) as compared to dry MA. It has also been shown that substituting Ta with W effectively suppresses GFA. After 100 h of MA of Co-Fe-W-B mixture, a nanocomposite material consisting of amorphous and nanocrystalline bcc-W phase was synthesized.

ADSORPTION OF CYCLOHEXANE AND BENZENE ON MIXED HYDROXIDES AND OXIDES OF MAGNESIUM AND ALUMINIUM

1966 ◽  
Vol 44 (8) ◽  
pp. 877-884 ◽  
Author(s):  
R. I. Razouk ◽  
Sh. Nashed ◽  
F. N. Antonious
Keyword(s):  
Thermal Analysis ◽  
Differential Thermal Analysis ◽  
Thermogravimetric Analysis ◽  
Surface Area ◽  
Structural Changes ◽  
Mixed Oxides ◽  
X Ray Diffraction ◽  
Oxide Systems ◽  
X Ray ◽  
Characteristic Lines

Seven mixed hydroxides of magnesium and aluminium were prepared, and phase and structural changes accompanying their dehydration were investigated by differential thermal analysis, thermogravimetric analysis, and X-ray diffraction techniques. The differential thermal analysis curves possess 2 peaks corresponding to those of parent hydroxides together with a new peak, and the thermogravimetric analysis curves show slight inflections. X-ray diffraction patterns of the mixed hydroxides possess the characteristic lines of the parent hydroxides together with three to five new intense lines which might indicate the formation of a double hydroxide. When the mixed hydroxides are progressively heated they give rise to products possessing patterns which first become diffuse and ultimately pass mainly into the spinel pattern.Adsorption isotherms of cyclohexane and benzene were measured on the mixed hydroxides and their dehydration products. Specific surface areas calculated by the application of the Brunauer, Emmett, Teller (B.E.T.) equation are in general in good agreement for the two adsorbates. The surface area increases with rise of dehydration temperature to a maximum at 500–600 °C and then decreases with further rise in temperature. This behavior is common to crystalline oxide systems and may be ascribed to the intermingling of decomposition, re-crystallization, and sintering processes. Variations in the molecular ratio of the mixed oxides (as much as 20-fold), and in the method of preparation, do not much alter the surface area.

Synthesis of Nanocrystalline Fe25Al57.5Ni17.5 by Mechanical Alloying

2012 ◽  
Vol 476-478 ◽  
pp. 1318-1321
Author(s):  
Qi Zhi Cao ◽  
Jing Zhang
Keyword(s):  
Thermal Analysis ◽  
Solid Solution ◽  
Differential Thermal Analysis ◽  
Mechanical Alloying ◽  
Ball Mill ◽  
Structural Changes ◽  
Early Stage ◽  
High Energy ◽  
X Ray Diffraction ◽  
X Ray

Nanostructured Fe25Al57.5Ni17.5intermetallics was prepared directly by mechanical alloying (MA) in a high-energy planetary ball-mill. The phase transformations and structural changes occurring in the studied material during mechanical alloying were investigated by X-ray diffraction (XRD). Thermal behavior of the milled powders was examined by differential thermal analysis (DTA). Disordered Al(Fe,Ni) solid solution was formed at the early stage. After 50 h of milling, Al(Fe,Ni) solid solution transformed into Al3Ni2，AlFe3，AlFe0.23Ni0.77 phase. The power annealed at temperature 500 results in forming of intermetallics AlFe3 and FeNi3 after 5h milling. The nanocrystalline intermetallic compound was obtained after 500h milling.

In situ high-energy synchrotron X-ray diffraction studies and first principles modeling of α-MnO2 electrodes in Li–O2 and Li-ion coin cells

2015 ◽  
Vol 3 (14) ◽  
pp. 7389-7398 ◽  
Author(s):  
Zhenzhen Yang ◽  
Lynn Trahey ◽  
Yang Ren ◽  
Maria K. Y. Chan ◽  
Chikai Lin ◽  
...  
Keyword(s):  
First Principles ◽  
Structural Changes ◽  
High Energy ◽  
X Ray Diffraction ◽  
Synchrotron Diffraction ◽  
X Ray ◽  
Li Ion ◽  
Battery Cells

In situ synchrotron diffraction and first principles modeling shows structural changes in α-MnO2 during cycling in Li–O2 battery cells, as lithium and oxygen are incorporated into and removed from tunnels in the structure.

In situelectrochemical high-energy X-ray diffraction using a capillary working electrode cell geometry

2017 ◽  
Vol 24 (4) ◽  
pp. 787-795 ◽  
Author(s):  
Matthias J. Young ◽  
Nicholas M. Bedford ◽  
Naisheng Jiang ◽  
Deqing Lin ◽  
Liming Dai
Keyword(s):  
Structural Changes ◽  
Active Material ◽  
High Energy ◽  
Distribution Functions ◽  
Atomic Scale ◽  
X Ray Diffraction ◽  
Active Materials ◽  
X Ray ◽  
Working Electrode ◽  
Electrochemically Active

The ability to generate new electrochemically active materials for energy generation and storage with improved properties will likely be derived from an understanding of atomic-scale structure/function relationships during electrochemical events. Here, the design and implementation of a new capillary electrochemical cell designed specifically forin situhigh-energy X-ray diffraction measurements is described. By increasing the amount of electrochemically active material in the X-ray path while implementing low-Zcell materials with anisotropic scattering profiles, an order of magnitude enhancement in diffracted X-ray signal over traditional cell geometries for multiple electrochemically active materials is demonstrated. This signal improvement is crucial for high-energy X-ray diffraction measurements and subsequent Fourier transformation into atomic pair distribution functions for atomic-scale structural analysis. As an example, clear structural changes in LiCoO2under reductive and oxidative conditions using the capillary cell are demonstrated, which agree with prior studies. Accurate modeling of the LiCoO2diffraction data using reverse Monte Carlo simulations further verifies accurate background subtraction and strong signal from the electrochemically active material, enabled by the capillary working electrode geometry.

scholarly journals Beyond sixfold coordinated Si in SiO2glass at ultrahigh pressures

2017 ◽  
Vol 114 (38) ◽  
pp. 10041-10046 ◽  
Author(s):  
Clemens Prescher ◽  
Vitali B. Prakapenka ◽  
Johannes Stefanski ◽  
Sandro Jahn ◽  
Lawrie B. Skinner ◽  
...  
Keyword(s):  
Coordination Number ◽  
Structural Changes ◽  
Packing Fraction ◽  
High Energy ◽  
Silicate Melts ◽  
X Ray Diffraction ◽  
X Ray ◽  
Diamond Anvil ◽  
Coordination Change ◽  
Insight Into

We investigated the structure of SiO2glass up to 172 GPa using high-energy X-ray diffraction. The combination of a multichannel collimator with diamond anvil cells enabled the measurement of structural changes in silica glass with total X-ray diffraction to previously unachievable pressures. We show that SiO2first undergoes a change in Si–O coordination number from fourfold to sixfold between 15 and 50 GPa, in agreement with previous investigations. Above 50 GPa, the estimated coordination number continuously increases from 6 to 6.8 at 172 GPa. Si–O bond length shows first an increase due to the fourfold to sixfold coordination change and then a smaller linear decrease up to 172 GPa. We reconcile the changes in relation to the oxygen-packing fraction, showing that oxygen packing decreases at ultrahigh pressures to accommodate the higher than sixfold Si–O coordination. These results give experimental insight into the structural changes of silicate glasses as analogue materials for silicate melts at ultrahigh pressures.

Effects of High Energy Ion Irradiation on Crystallization of Amorphous Germanium Films Deposited on Calcium Fluoride Substrates

1995 ◽  
Vol 396 ◽  
Author(s):  
Setsuo Nakao ◽  
Kazuo Saitoh ◽  
Masami Ikeyama ◽  
Hiroaki Niwa ◽  
Seita Tanemura ◽  
...  
Keyword(s):  
Thin Film ◽  
Calcium Fluoride ◽  
Structural Changes ◽  
Rutherford Backscattering Spectrometry ◽  
Ion Irradiation ◽  
High Energy ◽  
The Other ◽  
Ion Current ◽  
X Ray Diffraction ◽  
X Ray

AbstractAmorphous (a-) Ge films were deposited on air-cleaved CaF2 (111) substrates at different deposition temperatures (Td). The films were irradiated with 0.9 MeV Ge or Si ions at low ion current intensity (1c) l00nA/cm2. Their structural changes were studied by Rutherford backscattering spectrometry (RBS) -channeling technique and thin film x-ray diffraction (XRD) measurement. It was found that the films were epitaxially crystallized by Ge and Si ion irradiation although they included randomly oriented grains. Ge ion irradiation was more effective for the crystallization than Si ion irradiation. However, the amount of the randomly oriented grains was slightly higher when using Ge ions. On the other hand, ion irradiation to the films prepared at high Td also exhibited higher incidence of randomly oriented grains.

Interfacial Layer - A New Mechanism for Electromechanical Response

2004 ◽  
Vol 856 ◽  
Author(s):  
Zhimin Li ◽  
Z.-Y. Cheng
Keyword(s):  
Interfacial Layer ◽  
High Performance ◽  
High Strain ◽  
Interface Layer ◽  
Interface State ◽  
High Energy ◽  
Strain Response ◽  
X Ray Diffraction ◽  
X Ray ◽  
The Relationship

ABSTRACTElectric field induced phase transition has been used to explain the high strain response in some PVDF-based EAP. However, it is hard to understand some features (such as the relationship between the strain and the preload) of elastomers - an important type of EAPs. In this paper, we reported the study of recrystallization on high-energy-electron irradiated P(VDF-TrFE) copolymer. The morphology and structure as well as the structural transformation in the recrystallized copolymers were studied by means of X-ray diffraction, DSC, FTIR, and polarization measurements. The effect of crosslinking induced by the irradiation is discussed. The results suggest that a new interface layer existed in the recrystallized polymers. The partially ordered interfacial layer is a novel micro-origin of a high polarization obtained in an EAP. Based on this concept, the effect of preload on the E-M performance of the elastomers can be well explained. A new method to develop high performance electroactive polymer is outlined by using the interface state.

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