1,072,848 research outputs found
Oxidation of graphite surface: the role of water
Based on density functional calculations, we demonstrate a significant
difference in oxidation patterns between graphene and graphite and the
formation of defects after oxidation. Step-by-step modeling demonstrates that
oxidation of 80% of the graphite surface is favorable. Oxidation above half of
the graphite surface significantly decreases the energy costs of vacancy
formation with CO2 production. The presence of water is crucial in the
transformation of epoxy groups to hydroxyl, the intercalation with further
bundle and exfoliation. In water-rich conditions, water intercalates graphite
at the initial stages of oxidation and oxidation, which is similar to the
oxidation process of free-standing graphene; in contrast, in water-free
conditions, large molecules intercalate graphite only after oxidation occurs on
more than half of the surface.Comment: 10 pages, 3 figures, accepted to J. Phys. Chem.
Chemical Bonding Analysis on Amphoteric Hydrogen - Alkaline Earth Ammine Borohydrides
Usually the ions in solid are in the positive oxidation states or in the
negative oxidation state depending upon the chemical environment. It is highly
unusual for an ion having both positive as well as negative oxidation state in
a particular compound. Structural analysis suggest that the alkaline earth
ammine borohydrides (AABH) with the chemical formula M (BH4)2(NH3)2 (M = Mg,
Ca, or Sr) where hydrogen is present in +1 and -1 oxidation states. In order to
understand the oxidation states of hydrogen and also the character of chemical
bond present in AABH we have made charge density, electron localization
function, Born effective charge, Bader effective charge, and density of states
analyses using result from the density functional calculations. Our detailed
analyses show that hydrogen is in amphoteric behavior with hydrogen closer to
boron is in negative oxidation state and that closer to nitrogen is in the
positive oxidation state. Due to the presence of finite covalent bonding
between the consitutents in AABH the oxidation state of hydrogen is
non-interger value. The confirmation of the presence of amphtoric behavior of
hydrogen in AABH has implication in hydrogen storage applications
Proteome-wide analysis of cysteine oxidation reveals metabolic sensitivity to redox stress
Reactive oxygen species (ROS) are increasingly recognised as important signalling molecules through oxidation of protein cysteine residues. Comprehensive identification of redox-regulated proteins and pathways is crucial to understand ROS-mediated events. Here, we present stable isotope cysteine labelling with iodoacetamide (SICyLIA), a mass spectrometry-based workflow to assess proteome-scale cysteine oxidation. SICyLIA does not require enrichment steps and achieves unbiased proteome-wide sensitivity. Applying SICyLIA to diverse cellular models and primary tissues provides detailed insights into thiol oxidation proteomes. Our results demonstrate that acute and chronic oxidative stress causes oxidation of distinct metabolic proteins, indicating that cysteine oxidation plays a key role in the metabolic adaptation to redox stress. Analysis of mouse kidneys identifies oxidation of proteins circulating in biofluids, through which cellular redox stress can affect whole-body physiology. Obtaining accurate peptide oxidation profiles from complex organs using SICyLIA holds promise for future analysis of patient-derived samples to study human pathologies
Beneficial Effect of Pt and of Pre-Oxidation on the Oxidation Behaviour of an NiCoCrAlYTa Bond-Coating for Thermal Barrier Coating Systems
The oxidation behaviour of a thermal barrier coating (TBC) system is a major concern as the growth of the thermally grown oxide (TGO) layer on the bondcoating creates stresses that greatly favour the thermal barrier spallation. To delay the loss of the thermal protection provided, research has focused on the bondcoating composition and microstructure as well as on the parameters required for a suitable pre-oxidation treatment before the deposition of the ceramic top coat. Platinum is known to enhance the oxidation/corrosion resistance of MCrAlY coatings. The effect of Pt on the oxidation behaviour of a NiCoCrAlYTa coating was assessed in this study. In addition, pre-oxidation treatments were conducted to
determine if the oxidation behaviour of the modified NiCoCrAlYTa coating could be further improved
Understanding of the Retarded Oxidation Effects in Silicon Nanostructures
In-depth understanding of the retarded oxidation phenomenon observed during
the oxidation of silicon nanostructures is proposed. The wet thermal oxidation
of various silicon nanostructures such as nanobeams, concave/convex nanorings
and nanowires exhibits an extremely different and complex behavior. Such
effects have been investigated by the modeling of the mechanical stress
generated during the oxidation process explaining the retarded regime. The
model describes the oxidation kinetics of silicon nanowires down to a few
nanometers while predicting reasonable and physical stress levels at the
Si/SiO interface by correctly taking into account the relaxation effects
in silicon oxide through plastic flow
A transformative route to nanoporous manganese oxides of controlled oxidation states with identical textural properties
Nanoporous nanocrystalline metal oxides with tunable oxidation states are crucial for controlling their catalytic, electronic, and optical properties. However, previous approaches to modulate oxidation states in nanoporous metal oxides commonly lead to the breakdown of the nanoporous structure as well as involve concomitant changes in their morphology, pore size, surface area, and nanocrystalline size. Herein, we present a transformative route to nanoporous metal oxides with various oxidation states using manganese oxides as model systems. Thermal conversion of Mn-based metal-organic frameworks (Mn-MOFs) at controlled temperature and atmosphere yielded a series of nanoporous manganese oxides with continuously tuned oxidation states: MnO, Mn3O 4, Mn5O8, and Mn2O3. This transformation enabled the preparation of low-oxidation phase MnO and metastable intermediate phase Mn5O8 with nanoporous architectures, which were previously rarely accessible. Significantly, nanoporous MnO, Mn3O4, and Mn5O8 had a very similar morphology, surface area, and crystalline size. We investigated the electrocatalytic activity of nanoporous manganese oxides for oxygen reduction reaction (ORR) to identify the role of oxidation states, and observed oxidation state-dependent activity and kinetics for the ORR.close5
Studies in zirconium oxidation
Study provides insight into the oxidation mechanism of zirconium by combining electrical measurements with oxidation data. The measurement of electrical potential across growing scale on zirconium and the determination of conventional weight-change oxidation data were carried out at 550, 700, and 800 degrees C
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