In Situ Observations of Early Stage Oxidation of Ni-Cr and Ni-Cr-Mo Alloys

CORROSION ◽  
10.5006/2807 ◽  
2018 ◽  
Vol 74 (9) ◽  
pp. 939-946 ◽  
Author(s):  
Xiao-xiang Yu ◽  
Ahmet Gulec ◽  
Christopher M. Andolina ◽  
Evan J. Zeitchick ◽  
Kateryna Gusieva ◽  
...  
Keyword(s):  
Metal Oxide ◽  
Rock Salt ◽  
Density Functional ◽  
Early Stage ◽  
Density Functional Theory Calculations ◽  
Layer By Layer ◽  
Oxide Interface ◽  
Corundum Structure ◽  
Kirkendall Voids

Results of in situ transmission electron microscopy experiments on the early stage oxidation of Ni-Cr and Ni-Cr-Mo alloys are reported. An epitaxial rock-salt oxide with compositions outside the conventional solubility limits initiated at the surface of both alloys, progressing by a layer-by-layer mode. Kirkendall voids were found in Ni-Cr alloys near the metal/oxide interface, but were not seen in the Ni-Cr-Mo. The voids initiated in the oxide then diffused to the metal/oxide interface, driven by the misfit stresses in the oxide. A sequential oxide initiation was observed in NiCr alloys: rock-salt → spinel → corundum; however, for NiCrMo alloys, the metastable Ni2-xCrxO3 (corundum structure) phase formed shortly after the growth of the rock-salt phase. Chemical analysis shows that solute atoms were captured in the initial oxide before diffusing and transforming to more thermodynamically stable phases. The results indicate that Mo doping inhibits the formation of Kirkendall voids via an increase in the nucleation rate of corundum, which was verified by density functional theory calculations.

In Situ Exsolved Au Nanoparticles from Perovskite Oxide for Efficient Epoxidation of Styrene

2021 ◽  
Author(s):  
Yang Gao ◽  
Xing Chen ◽  
Shuqi Hu ◽  
Shiguo Zhang
Keyword(s):  
Density Functional Theory ◽  
Thermodynamic Analysis ◽  
Density Functional ◽  
Au Nanoparticles ◽  
Oxide Catalyst ◽  
Density Functional Theory Calculations ◽  
Average Diameter ◽  
Perovskite Oxide ◽  
Functional Theory

Au-doped SrTiO3 perovskite oxide catalyst (Sr0.995Au0.005TiO3-δ) has been designed and synthesized based on thermodynamic analysis and density functional theory calculations. During reduction, Au nanoparticles with an average diameter of 2...

scholarly journals Elucidating the Drug Release from Metal-Organic Framework Nanocomposites via in Situ Synchrotron Microspectroscopy and Theoretical Modelling

2019 ◽  
Author(s):  
Barbara Souza ◽  
Lorenzo Dona ◽  
Kirill Titov ◽  
Paolo Bruzzese ◽  
Zhixin Zeng ◽  
...  
Keyword(s):  
Drug Delivery ◽  
Drug Release ◽  
Density Functional ◽  
Metal Organic Framework ◽  
Density Functional Theory Calculations ◽  
Theoretical Modelling ◽  
Time Resolved ◽  
Drug Molecules ◽  
Metal Organic

Nanocomposites comprising metal-organic frameworks (MOFs) embedded in a polymeric matrix are promising carriers for drug delivery applications. While understanding the chemical and physical transformations of MOFs during the release of confined drug molecules is challenging, this is central to devising better ways for controlled release of therapeutic agents. Herein we demonstrate the efficacy of synchrotron microspectroscopy to track the in situ release of 5-fluorouracil (5-FU) anticancer drug molecules from a drug@MOF/polymer composite (5-FU@HKUST-1/polyurethane). Using experimental time-resolved infrared spectra jointly with newly developed density functional theory calculations, we reveal the detailed dynamics of vibrational motions underpinning the dissociation of 5-FU bound to the framework of HKUST-1 upon water exposure. We discover that HKUST-1 creates hydrophilic channels within the hydrophobic polyurethane matrix hence helping to tune drug release rate. The synergy between a hydrophilic MOF with a hydrophobic polymer can be harnessed to engineer a tunable nanocomposite that alleviates the unwanted burst effect commonly encountered in drug delivery.<br>

scholarly journals Elucidating the Drug Release from Metal-Organic Framework Nanocomposites via in Situ Synchrotron Microspectroscopy and Theoretical Modelling

2019 ◽  
Author(s):  
Barbara Souza ◽  
Lorenzo Dona ◽  
Kirill Titov ◽  
Paolo Bruzzese ◽  
Zhixin Zeng ◽  
...  
Keyword(s):  
Drug Delivery ◽  
Drug Release ◽  
Density Functional ◽  
Metal Organic Framework ◽  
Density Functional Theory Calculations ◽  
Theoretical Modelling ◽  
Time Resolved ◽  
Drug Molecules ◽  
Metal Organic

Nanocomposites comprising metal-organic frameworks (MOFs) embedded in a polymeric matrix are promising carriers for drug delivery applications. While understanding the chemical and physical transformations of MOFs during the release of confined drug molecules is challenging, this is central to devising better ways for controlled release of therapeutic agents. Herein we demonstrate the efficacy of synchrotron microspectroscopy to track the in situ release of 5-fluorouracil (5-FU) anticancer drug molecules from a drug@MOF/polymer composite (5-FU@HKUST-1/polyurethane). Using experimental time-resolved infrared spectra jointly with newly developed density functional theory calculations, we reveal the detailed dynamics of vibrational motions underpinning the dissociation of 5-FU bound to the framework of HKUST-1 upon water exposure. We discover that HKUST-1 creates hydrophilic channels within the hydrophobic polyurethane matrix hence helping to tune drug release rate. The synergy between a hydrophilic MOF with a hydrophobic polymer can be harnessed to engineer a tunable nanocomposite that alleviates the unwanted burst effect commonly encountered in drug delivery.<br>

scholarly journals Reversible spin storage in metal oxide—fullerene heterojunctions

2020 ◽  
Vol 6 (12) ◽  
pp. eaax1085 ◽  
Author(s):  
T. Moorsom ◽  
M. Rogers ◽  
I. Scivetti ◽  
S. Bandaru ◽  
G. Teobaldi ◽  
...  
Keyword(s):  
Metal Oxide ◽  
Density Functional ◽  
Muon Spin ◽  
Magnetic Ordering ◽  
Charge Trapping ◽  
Energy Shift ◽  
Storage Device ◽  
Oxide Interface ◽  
Independent Evidence ◽  
Spin Polarized

We show that hybrid MnOx/C60 heterojunctions can be used to design a storage device for spin-polarized charge: a spin capacitor. Hybridization at the carbon-metal oxide interface leads to spin-polarized charge trapping after an applied voltage or photocurrent. Strong electronic structure changes, including a 1-eV energy shift and spin polarization in the C60 lowest unoccupied molecular orbital, are then revealed by x-ray absorption spectroscopy, in agreement with density functional theory simulations. Muon spin spectroscopy measurements give further independent evidence of local spin ordering and magnetic moments optically/electronically stored at the heterojunctions. These spin-polarized states dissipate when shorting the electrodes. The spin storage decay time is controlled by magnetic ordering at the interface, leading to coherence times of seconds to hours even at room temperature.

Investigation of Structural Evolution of Li1.1V3O8 by In Situ X-ray Diffraction and Density Functional Theory Calculations

2017 ◽  
Vol 29 (5) ◽  
pp. 2364-2373 ◽  
Author(s):  
Qing Zhang ◽  
Alexander B. Brady ◽  
Christopher J. Pelliccione ◽  
David C. Bock ◽  
Andrea M. Bruck ◽  
...  
Keyword(s):  
Density Functional Theory ◽  
Density Functional ◽  
Structural Evolution ◽  
Density Functional Theory Calculations ◽  
X Ray Diffraction ◽  
Functional Theory ◽  
X Ray

Metal-Support Interactions and C1 Chemistry: Transforming Pt-CeO2 into a Highly Active and Stable Catalyst for the Conversion of Carbon Dioxide and Methane

2020 ◽  
Author(s):  
Feng Zhang ◽  
Ramón A. Gutiérrez ◽  
Pablo Lustemberg ◽  
Zongyuan Liu ◽  
Ning Rui ◽  
...  
Keyword(s):  
Carbon Dioxide ◽  
Metal Oxide ◽  
Elevated Temperatures ◽  
Chemical Properties ◽  
Oxide Interface ◽  
Highly Active ◽  
Metal Support ◽  
Metal Support Interactions ◽  
Methane Dissociation

There is an ongoing search for materials which can accomplish the activation of two dangerous greenhouse gases like carbon dioxide and methane. In the area of C1 chemistry, the reaction between CO2 and CH4 to produce syngas, known as methane dry reforming (MDR), is attracting a lot of interest due to its green nature. On Pt(111), elevated temperatures are necessary to activate the reactants and massive deposition of carbon makes this metal surface ineffective for the MDR process. In this study, we show that strong metal-support interactions present in Pt/CeO2(111) and Pt/CeO2 powders lead to systems which can bind well CO2 and CH4 at room temperature and are excellent and stable catalysts for the MDR process at moderate temperature (500 ºC). The behaviour of these systems was studied using a combination of in-situ/operando methods which pointed to an active Pt-CeO2-x interface. In this interface, the oxide is far from being a passive spectator. It modifies the chemical properties of Pt, facilitating improved methane dissociation, and is directly involved in the adsorption and dissociation of CO2 making the MDR catalytic cycle possible. A comparison of the benefits gained by the use of an effective metal-oxide interface and those obtained by plain bimetallic bonding indicates that the former is much more important when optimizing the C1 chemistry associated with CO2 and CH4 conversion. The presence of elements with a different chemical nature at the metal-oxide interface opens the possibility for truly cooperative interactions in the activation of C-O and C-H bonds.

CO adsorption on graphite-like ZnO bilayers supported on Cu(111), Ag(111) and Au(111) surfaces

2017 ◽  
Author(s):  
Sergio Tosoni ◽  
Cequn Li ◽  
Philomena Schlexer ◽  
Gianfranco Pacchioni
Keyword(s):  
Density Functional ◽  
Chemical Interaction ◽  
Co Adsorption ◽  
Density Functional Theory Calculations ◽  
Dispersion Interactions ◽  
Oxide Interface ◽  
Functional Theory ◽  
Bilayer Films ◽  
Coinage Metals ◽  
Co Probe

<div> <div> <div> <p>Graphitic-like ZnO bilayer films deposited on coinage metals, Cu(111), Ag(111), and Au(111) have been studied by density functional theory calculations including dispersion corrections. The scope is to compare on an equal footing the properties of the three systems and in particular the nature of the metal/oxide interface. To this end we have considered the adsorption of a CO probe molecule and the vibrational shifts induced by adsorption on ZnO/Cu(111), ZnO/Ag(111), and ZnO/Au(111) compared to adsorption on the unsupported ZnO bilayer and on the wurtzite ZnO surface. We find that while the interaction of ZnO with Ag and Au supports is dominated by dispersion interactions with little or no charge transfer at the interface, in the case of Cu a moderate electron transfer occurs towards the ZnO bilayer. As a consequence, while the stretching frequency of CO on ZnO/Au is blue-shifted, that on ZnO/Cu is red- shifted compared to free CO. CO on ZnO/Ag is intermediate. In all three cases, however, the ZnO bilayer is almost flat, with a modest rumpling found in the case of Cu as a consequence of the stronger chemical interaction. The results fully explain the CO vibrational shifts of CO on ZnO/Cu(111) [Schott, V. et al. Angew. Chem. Int. Ed. 2013, 52, 1-6] without implying major distortions in the supported film. </p> </div> </div> </div>

scholarly journals Partially ordered state of ice XV

2016 ◽  
Vol 6 (1) ◽  
Author(s):  
K. Komatsu ◽  
F. Noritake ◽  
S. Machida ◽  
A. Sano-Furukawa ◽  
T. Hattori ◽  
...  
Keyword(s):  
Neutron Diffraction ◽  
Density Functional ◽  
Density Functional Theory Calculations ◽  
Dielectric Measurement ◽  
Functional Theory ◽  
Ordered Structures ◽  
Partially Ordered ◽  
The Rich ◽  
Ordered State

Abstract Most ice polymorphs have order–disorder “pairs” in terms of hydrogen positions, which contributes to the rich variety of ice polymorphs; in fact, three recently discovered polymorphs— ices XIII, XIV, and XV—are ordered counter forms to already identified disordered phases. Despite the considerable effort to understand order–disorder transition in ice crystals, there is an inconsistency among the various experiments and calculations for ice XV, the ordered counter form of ice VI, i.e., neutron diffraction observations suggest antiferroelectrically ordered structures, which disagree with dielectric measurement and theoretical studies, implying ferroelectrically ordered structures. Here we investigate in-situ neutron diffraction measurements and density functional theory calculations to revisit the structure and stability of ice XV. We find that none of the completely ordered configurations are particular favored; instead, partially ordered states are established as a mixture of ordered domains in disordered ice VI. This scenario in which several kinds of ordered configuration coexist dispels the contradictions in previous studies. It means that the order–disorder pairs in ice polymorphs are not one-to-one correspondent pairs but rather have one-to-n correspondence, where there are n possible configurations at finite temperature.

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