Search results for "kinetics"
showing 10 items of 2224 documents
Role ofH2Oin the thermal annealing of theEγ′center in amorphous silicon dioxide
2009
The model for the annealing of a radiation-induced point defect in silica, the ${\text{E}}_{\ensuremath{\gamma}}^{\ensuremath{'}}$ center, is identified in the temperature range $(150--550)\ifmmode^\circ\else\textdegree\fi{}\text{C}$. Thermal treatments in controlled atmospheres of water vapor, oxygen, or helium of irradiated amorphous silicon dioxide are carried out. Direct experimental evidences that the annealing of the ${\text{E}}_{\ensuremath{\gamma}}^{\ensuremath{'}}$ center is caused by a reaction with diffusing water molecules are found. A rate equation system describing this annealing process is inferred, and its solutions are compared with experimental data to obtain quantitative …
Photoelectrochemical removal of chlorfenvinphos by using WO3 nanorods: Influence of annealing temperature and operation pH
2019
[EN] A visible-light driven photoelectrochemical degradation process has been applied to a solution polluted with the organophosphate insecticide chlorfenvinphos. Different WO3 nanosheets/nanorods have been used as photoanodes. These nanostructured electrodes have been fabricated by anodization of tungsten and, subsequently, they have been subjected to a thermal treatment (annealing). The combined influence of annealing temperature (400¿°C and 600¿°C) and operation pH (1 and 3) on the photoelectrocatalytic behavior of these nanorods has been examined through a statistical analysis. Morphological, structural and photoelectrochemical characterizations have also been carried out. The chlorfenv…
Chitosan-coated mesoporous MIL-100(Fe) nanoparticles as improved bio-compatible oral nanocarriers
2017
Nanometric biocompatible Metal-Organic Frameworks (nanoMOFs) are promising candidates for drug delivery. Up to now, most studies have targeted the intravenous route, related to pain and severe complications; whereas nanoMOFs for oral administration, a commonly used non-invasive and simpler route, remains however unexplored. We propose here the biofriendly preparation of a suitable oral nanocarrier based on the benchmarked biocompatible mesoporous iron(III) trimesate nanoparticles coated with the bioadhesive polysaccharide chitosan (CS). This method does not hamper the textural/structural properties and the sorption/release abilities of the nanoMOFs upon surface engineering. The interaction …
First principles calculations of oxygen reduction reaction at fuel cell cathodes
2020
This study was partly supported by M-ERA-NET project SunToChem (EK, YM). The computer resources were provided by Stuttgart Super-computing Center (Project DEFTD 12939). Authors thank E. Heifets, M. M. Kuklja, M. Arrigoni, D. Morgan, R. Evarestov, and D. Gryaznov for fruitful discussions.
Preformulation: Effect of Moisture Content on Microcrystalline Cellulose (Avicel PH-302) and Its Consequences on Packing Performances
1999
This study evaluates the influence of moisture content on the packing performances of a new grade of microcrystalline cellulose (MCC) (Avicel PH-302) either by classical method or by an unconventional compression technique (constant volume reduction of powder bed). An increase in moisture content decreases the apparent density of the powder bed, resulting from interparticulate friction enhancement. This modification of apparent density seems to be the main effect caused by the presence of humidity, which explains the variations of compression properties, like an increase of powder plasticity generally observed in the experimental conditions.
Effect of Organic Tin Compounds on Electric Properties of Model Membranes
2006
The objective of the present work was to investigate the effect of selected organic tin compounds and potassium chloride (used as a reference substance) on the trans-membrane electric voltage and electric resistance of model membranes, the latter being nitrocellulose filters impregnated with butylene ester of lauric acid. The increasing KCl concentration (in the measurement chambers) caused a rapid rise of the negative trans-membrane voltage, whose value stabilized afterwards. In the case of (C3H7)3SnCl an abrupt maximum of the negative voltage was observed followed by a monotonic drop to zero. In the case of highest concentrations of this compound the voltages, after having reached zero, c…
Melting Process of the Sn-45 wt.% In and Sn-77 wt.% In Alloys as Viewed by Positron Annihilation
2006
The temperature dependences of the positron annihilation parameters F and R were determined for Sn–45 wt.% In and Sn–77 wt.% In alloys. The obtained results enabled to verify the vacancy and the quasicrystalline models of the melting process. It was found that for metals transforming into the liquid state from the structures different than the close packed structure, the melting transition are hardly explainable in terms of the vacancy model of melting. The strong trapping of positrons in metallic liquids is an indication of the presence of microvoids (vacancy clusters) or microcrystals containing defects more immense than vacancies. The share of these positron trapping centers in the volum…
Study of stress effects in the oxidation of Zircaloy-4
2001
Abstract The oxidation of zirconium alloy Zy-4 is due to an anionic diffusion of oxygen leading to the formation of an oxide layer of zirconia. According to the Pilling and Bedworth ratio of the Zr/ZrO 2 system, the oxide scale is under compressive stresses. This stress state may play an important role during the corrosion process, from the phases as well as from the kinetics point of view. In order to better understand the eventual relationship between oxide phases, oxidation kinetics and stresses, an experimental apparatus was developed in our laboratory. It allows the application of external tensile stresses, in situ oxidation of the sample in controlled environment and X-ray diffraction…
Exact solution of ‘‘hot dimer’’ adsorption in one-dimensional lattices
1993
An analytical solution for the kinetics of the ``hot-dimer'' adsorption in a one-dimensional lattice is reported. Hot dimers are molecules that dissociate after deposition, and each of the remaining monomers fly apart up to a maximum distance R from the original adsorption sites. The kinetics of this process is strongly dependent on the flying distance R. We find a particular behavior of the jamming coverage as a function of R. Monte Carlo simulation results are in agreement with such a calculation.
Ester-Ester Exchange Reactions of Aliphatic Polyesters
1979
Abstract The kinetics of ester-ester exchange reactions of poly(ethylene adipate) and poly(trimethylene adipate) at 312°C and in the absence of a solvent and catalysts has been reported previously. Independent investigations of the thermal degradation reactions of these polyesters under high vacuum have shown that pyrolysis already starts above 270°C. An ester-ester exchange mechanism via a reversible thermal degradation reaction is proposed.