Theoretical Evaluation of Oxidation Rate of Zr

2013 ◽  
Vol 1535 ◽  
Author(s):  
Yasunori Yamamoto ◽  
Kazunori Morishita ◽  
Hirotomo Iwakiri ◽  
Yasunori Kaneta
Keyword(s):  
Oxygen Vacancy ◽  
Diffusion Process ◽  
Oxidation Rate ◽  
Experimental Fact ◽  
Stress Effect ◽  
Theoretical Evaluation ◽  
Simple Diffusion ◽  
Calculation Results ◽  
And Migration ◽  
Diffusion Coefficient Of Oxygen

ABSTRACTFirst principle calculations were performed to evaluate stress effect on the diffusion process of oxygen vacancy in ZrO2 film, and oxidation rate of Zr was evaluated by solving simple diffusion equations. Our calculation results have indicated that both the vacancy formation and migration energies of ZrO2 increase with increasing compressive applied stress. The energy increase causes a decrease in the diffusion coefficient of oxygen vacancy in ZrO2, leading to a decrease in oxidation rate of Zr. The stress effect on diffusion process may explain the experimental fact that Zr is oxidized in proportion to the cubic root of time.

First principles analysis of oxygen vacancy formation and migration in Sr2BMoO6 (B = Mg, Co, Ni)

RSC Advances ◽  
2016 ◽  
Vol 6 (38) ◽  
pp. 31968-31975 ◽  
Author(s):  
Shuai Zhao ◽  
Liguo Gao ◽  
Chunfeng Lan ◽  
Shyam S. Pandey ◽  
Shuzi Hayase ◽  
...  
Keyword(s):  
Density Functional Theory ◽  
Oxygen Vacancy ◽  
First Principles ◽  
Density Functional ◽  
Dft Method ◽  
Double Perovskites ◽  
Functional Theory ◽  
Oxygen Vacancy Formation ◽  
The Density Functional Theory ◽  
And Migration

In this work, we present a detailed first-principles investigation on the stoichiometric and oxygen-deficient structures of double perovskites, Sr2BMoO6 (B = Mg, Co and Ni), using the density functional theory (DFT) method.

Oxygen vacancy-confined CoMoO4@CoNiO2 nanorod arrays for oxygen evolution with improved performance

2019 ◽  
Vol 48 (27) ◽  
pp. 10116-10121 ◽  
Author(s):  
Xiaoqiang Du ◽  
Guangyu Ma ◽  
Xiaoshuang Zhang
Keyword(s):  
Oxygen Vacancy ◽  
Oxygen Evolution ◽  
Adsorption Energy ◽  
Active Sites ◽  
Oxygen Vacancies ◽  
Dft Calculation ◽  
Catalytic Properties ◽  
Nanorod Arrays ◽  
Calculation Results ◽  
Improved Performance

Experimental and DFT calculation results show that the presence of oxygen vacancies can decrease the adsorption energy of intermediates at active sites and facilitate the adsorption of intermediates, thus improving the catalytic properties.

Ab Initio Studies of Nb Doping Effect on the Formation and Diffusion of Oxygen Vacancy and Ti Interstitial in Rutile TiO2

2011 ◽  
Vol 304 ◽  
pp. 142-147 ◽  
Author(s):  
Xu Wang ◽  
Fu He Wang
Keyword(s):  
Activation Energy ◽  
Oxygen Vacancy ◽  
Density Functional Calculations ◽  
Density Functional ◽  
Formation Energy ◽  
Suppressive Effect ◽  
Nb Doping ◽  
O Vacancy ◽  
And Migration ◽  
And Diffusion

The effect of Nb doping on the formation and diffusion of O vacancies and interstitial Ti in rutile TiO2 are studied by the use of ab initio density-functional calculations. Our calculation showed that the activation energy for the diffusion of O vacancy with Nb doping is higher than that of pure. That owing to suppressive effect of Nb doping on the formation of O vacancy. Different from the effect of Nb doping on O vacancy, both of the formation energy and migration barrier of interstitial Ti increase with the Nb doping. Our calculated results may be one of the reasons why Nb doping can improve oxidation resistance of γ-TiAl.

Some generalizations of Bailey's birth death and migration model

1970 ◽  
Vol 2 (01) ◽  
pp. 83-109 ◽  
Author(s):  
A. W. Davis
Keyword(s):  
Diffusion Process ◽  
Hypergeometric Functions ◽  
Spatial Location ◽  
Death Process ◽  
Birth And Death Process ◽  
Limiting Distributions ◽  
Migration Model ◽  
Branching Diffusion ◽  
And Migration ◽  
Natural Measures

Some results for a general Markov branching-diffusion process are presented, and applied to a model recently considered by Bailey. Moments of the limiting distributions of certain natural measures of the spatial location and dispersion of the population are shown to be expressible in terms of the LauricellaFD-type hypergeometric functions, when the population multiplies according to the simple birth and death process with λ > μ.

Diffusion of Radionuclides in Compacted Bentonite : Results from Combined Glass Dissolution and Migration Tests

1994 ◽  
Vol 353 ◽  
Author(s):  
Masaki Tsukamoto ◽  
T. Ohe ◽  
T. Fujita ◽  
R. HesbÖl ◽  
H-P. Hermansson
Keyword(s):  
Dry Density ◽  
Apparent Diffusion Coefficients ◽  
Glass Dissolution ◽  
Glass Corrosion ◽  
Gas Atmosphere ◽  
Apparent Diffusion ◽  
Calculation Results ◽  
The Difference ◽  
And Migration ◽  
Elemental Mass

AbstractDiffusion experiments of radionuclides in compacted sodium bentonite with a dry density of 1.0 g/cm3 were performed in nitrogen gas atmosphere at 90 °C for 208 d and 375 d. The corrosion experiments of crushed radioactive glass, JSS-A, carried out simultaneously to provide the source of the radionuclides for the diffusion experiments. The normalized elemental mass losses of cesium isotopes and 238Pu were lower than those of boron (ca. 10 g/m2) probably because of the difference of sorption and/or precipitation. The apparent diffusion coefficients of 238Pu, 234U and 125Sb were determined to be 2x 10-14 m2/s, 5x 10-12 m2/s and 2x 10-12 m2/s, respectively. The distribution coefficient of Pu estimated from the diffusion data was of the same order as that from batch sorption experiments. The glass corrosion and the plutonium diffusion were described by the geochemical codes PHREEQE, STRAG4 and GESPER. The calculation results well fitted the observed data.

scholarly journals Microstructures of SiO2 Scales Formed on MoSi2

2006 ◽  
Vol 522-523 ◽  
pp. 595-602 ◽  
Author(s):  
Kazuya Kurokawa ◽  
Daichi Goto ◽  
Jyunichi Kuchino ◽  
Akira Yamauchi ◽  
Tamaki Shibayama ◽  
...  
Keyword(s):  
Growth Rate ◽  
Diffusion Coefficient ◽  
Oxide Scale ◽  
Oxidation Rate ◽  
Diffusion Mechanism ◽  
Lattice Diffusion ◽  
Oxide Scales ◽  
Amorphous Sio2 ◽  
O2 Diffusion ◽  
Diffusion Coefficient Of Oxygen

The microstructures of oxide scales formed on MoSi2 at medium-high temperatures in air were observed by TEM. Based on the observation, relationships between oxidation temperature and formation of MoO3 and crystallization of amorphous SiO2 scales were investigated. At 1273 K and 1373 K, the oxide scales had a structure consisting of amorphous SiO2 with small amounts of fine MoO3 particles. The oxide scales at 1573 K and 1773 K had a structure consisting of amorphous and crystalline SiO2. Growth rate of the oxide scale formed at 1773 K appreciably increased due to crystallization of amorphous SiO2. It was thought that the increase in the oxidation rate at 1773 K was caused by a change in the diffusion mechanism from O2 diffusion to lattice diffusion of O2- through SiO2. In addition, the diffusion coefficient of oxygen was estimated from the growth rate of SiO2 scale.

Theoretical Analysis of Oxygen Diffusion in monoclinic HfO2

2003 ◽  
Vol 786 ◽  
Author(s):  
Minoru Ikeda ◽  
Georg Kresse ◽  
Toshihide Nabatame ◽  
Akira Toriumi
Keyword(s):  
Oxygen Vacancy ◽  
Oxygen Atom ◽  
Diffusion Process ◽  
Nearest Neighbor ◽  
Chemical Potential ◽  
Annihilation Process ◽  
Interstitial Oxygen ◽  
Middle Range ◽  
Pair Annihilation ◽  
Charge States

ABSTRACTIn this report, we present the detailed analysis of the interstitial oxygen (O2+, O0, O2-) diffusion in monoclinic HfO2 (hafnia) using the first principles calculations. The interstitial oxygen atom kicks out the oxygen atom at the 3-fold-site and occupies the 3-fold-site. And then the newly kicked-out interstitial oxygen atom jumps to the nearest neighbor site and couples again with the atoms at the crystal sites. This kick-out- mechanism is valid for all charge states of the interstitial oxygen in monoclinic HfO2. In hafnia, the interstitial oxygen atom can take 3 charge states (+2, 0, -2) depending on the chemical potential (Ef), whereas the oxygen-vacancy in hafnia can get +2 or 0 charge state being dependent on Ef. In the lower range of Ef, O2+ and O0 might contribute. In the middle range of Ef, the O2- does not contribute to the diffusion process in hafnia because of the pair annihilation process between O2- and oxygen vacancy (V2+) defect pair. We can simulate such a pair annihilation process in hafnia. In the higher range, O2- might contribute the diffusion process.

Equations and Verification of New Diffusion Parameters

2008 ◽  
Vol 589 ◽  
pp. 293-297
Author(s):  
Zoltán Dudás
Keyword(s):  
Diffusion Processes ◽  
Diffusion Equations ◽  
Diffusion Parameter ◽  
Temperature Dependent ◽  
Simple Diffusion ◽  
Diffusion Parameters ◽  
Calculation Results ◽  
Equivalent Diffusion

This document shows the equations and some calculation results of two new Diffusion parameters. The Diffusion parameters assist the calculation of different temperature or time values for equivalent diffusion processes. The Diffusion parameters include temperature dependent and temperature independent factors. The document shows that the introduced Diffusion parameter is suitable for the accurate calculations of the temperature and time values for equal simple diffusion processes. The document shows, that the frequently used Larson-Miller parameter (LMP) does not give accurate results if we use the temperature and time values of equal simple diffusion equations for the LMP calculations.

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