A Model of CoO Oxidation

1993 ◽  
Vol 58 (12) ◽  
pp. 2853-2866
Author(s):  
Marcela Tkadlecová
Keyword(s):  
Experimental Data ◽  
Temperature Dependence ◽  
Mole Fraction ◽  
Rate Constant ◽  
Surface Reaction ◽  
Energy Of Activation ◽  
The Given ◽  
Oxygen Mole Fraction

A model of CoO oxidation was proposed which assumes the diffusion of cobalt atoms from the bulk of crystalline to its surface and the surface reaction of these atoms with surrounding oxygen. It depends on the comparison of expressions D/a20 and kxox/a0 to what extent these two processes will manifest themselves for the given temperature and oxygen mole fraction xox. The value of diffusivity D and its temperature dependence were estimated from the data in literature and the size of crystallites a0 from roentgenographic measurements. The value of rate constant of surface reaction k and its energy of activation were evaluated from experimental data for CoO oxidation.

scholarly journals Surface tension of liquid Ti with adsorbed oxygen and a simple associate model for its prediction

2020 ◽  
Vol 49 (1-2) ◽  
pp. 89-105 ◽  
Author(s):  
J. BRILLO ◽  
J. WESSING ◽  
H. KOBATAKE ◽  
H. FUKUYAMA
Keyword(s):  
Experimental Data ◽  
Surface Tension ◽  
Simple Model ◽  
Chemical Analysis ◽  
Mole Fraction ◽  
Tio2 Powder ◽  
Bulk Oxygen ◽  
Electromagnetically Levitated ◽  
Oxygen Mole Fraction ◽  
Good Agreement

Surface tensions of electromagnetically levitated liquid Ti-samples were measured under the influence of oxygen. For this purpose, Ti-O samples were prepared by adding different amounts of TiO2 powder to pure Ti. The surface tension was found to strongly depend on the bulk oxygen mole fraction determined by chemical analysis. The results could be described by a simple model presented in the present work. In this model the Butler equation is applied and the formation of TiO2 – associates are taken into account. Non-ideal interactions ΔH≠0 between titanium and the associates also need to be taken into account. Good agreement with the experimental data is evident and also with a different model developed earlier by us.

Recombination of iodine atoms in dilute solutions of argon

1970 ◽  
Vol 316 (1524) ◽  
pp. 81-96 ◽  
Keyword(s):  
Experimental Data ◽  
Temperature Dependence ◽  
Rate Constant ◽  
Flash Photolysis ◽  
Quantitative Agreement ◽  
A Value ◽  
Electronically Excited ◽  
Recombination Rate Constant ◽  
Equilibrium Separation ◽  
Combined Data

The reaction 2I + Ar→ I 2 + Ar was studied at 298, 323 and 423 K by flash photolysis. The overall rate constant, k obs , for this reaction is a linear function of [I 2 ]/[Ar], but below [I 2 ]/[Ar] ~ 10 -4 , the relation becomes non-linear and k obs falls below extrapolated values. The fall-off is explained in terms of a mechanism involving an IAr intermediate: I + Ar ⇌ IAr IAr + I → I 2 + Ar. The equilibrium separation in such an IAr complex is 0.55 nm and the binding energy is 6.3 kJ mol -1 (1.5 kcal mol -1 ). This mechanism predicts the onset of the fall-off in agreement with the available experimental data. Moreover, the temperature dependence of this onset and the temperature dependence of the recombination rate constant from 298 to 1500 K are also satisfactorily explained. In addition to the above, the new mechanism yields quantitative agreement between our new rate constants and those reported previously. These combined data for 298 K yield a value of 3.00 (± 0.16) x 10 9 l 2 mol -2 s -1 for the rate constant for the reaction 2I + Ar → I 2 + Ar, and one of 1.00(± 0.09) х 10 12 I 2 mol -2 s -1 for 2I + I 2 → 2I 2 . Several other mechanisms are also considered, including some previously suggested in the literature. It is shown that none of these explains satisfactorily all the experimental data. However, most of the available experimental data could be explained, if it were assumed that the recombination proceeds via an unobserved electronically excited I 2 , formed from two 2 P 3/2 atoms, with a potential well 21 to 29 kJ mol -1 deep (5 to 7 kcal mol -1 ).

TEMPERATURE DEPENDENCE BEHAVIOR OF ELECTRICAL RESISTIVITY IN NOBLE METALS AT LOW TEMPERATURES

2014 ◽  
Vol 5 (3) ◽  
pp. 982-992 ◽  
Author(s):  
M AL-Jalali
Keyword(s):  
Experimental Data ◽  
Electrical Resistivity ◽  
Temperature Dependence ◽  
Concentration Dependence ◽  
Low Temperatures ◽  
Noble Metals ◽  
Phonon Scattering ◽  
Theoretical Models ◽  
Residual Resistivity ◽  
Electron Phonon Scattering

Resistivity temperature – dependence and residual resistivity concentration-dependence in pure noble metals(Cu, Ag, Au) have been studied at low temperatures. Dominations of electron – dislocation and impurity, electron-electron, and electron-phonon scattering were analyzed, contribution of these mechanisms to resistivity were discussed, taking into consideration existing theoretical models and available experimental data, where some new results and ideas were investigated.

Solubility and Thermodynamic Transfer Functions of Cesium Dianilinetetraisothiocyanatochromate(III)

1998 ◽  
Vol 63 (3) ◽  
pp. 293-298
Author(s):  
Vladislav Holba
Keyword(s):  
Experimental Data ◽  
Isopropyl Alcohol ◽  
Transfer Functions ◽  
Butyl Alcohol ◽  
Aqueous Methanol ◽  
Gibbs Energies ◽  
Gibbs Energy Of Transfer ◽  
Energy Of Transfer ◽  
The Given ◽  
Reference Electrolyte

The solubilities of cesium dianilinetetraisothiocyanatochromate(III) in water as well as in aqueous methanol, isopropyl alcohol, tert-butyl alcohol and acetonitrile were measured as a function of temperature and solvent composition. The Gibbs energies, enthalpies and entropies of transfer of the salt from water to the given solvents have been evaluated from experimental data. The contribution of [Cr(C6H5NH2)2(NCS)4]- ion to the Gibbs energy of transfer of the investigated salt has been calculated using the tetraphenylarsonium tetraphenylborate (TATB) reference electrolyte assumption.

Radiolysis studies on the corrosion inhibitors 1 -hexyn-3-ol, cinnamonitrile, and 1,3-diethyl-2-thiourea

1995 ◽  
Vol 73 (12) ◽  
pp. 2137-2142 ◽  
Author(s):  
A.J. Elliot ◽  
M.P. Chenier ◽  
D.C. Ouellette
Keyword(s):  
Hydrogen Atom ◽  
Hydroxyl Radical ◽  
Temperature Dependence ◽  
Rate Constant ◽  
Rate Constants ◽  
Corrosion Inhibitors ◽  
Hydrated Electron

In this publication we report: (i) the rate constants for reaction of the hydrated electron with 1-hexyn-3-ol ((8.6 ± 0.3) × 108 dm3 mol−1 s−1 at 18 °C), cinnamonitrile ((2.3 ± 0.2) × 1010 dm3 mol−1 s−1 at 20 °C), and 1,3-diethyl-2-thiourea ((3.5 ± 0.3) × 108 dm3 mol−1 s−1 at 22 °C). For cinnamonitrile and diethylthiourea, the temperature dependence up to 200 °C and 150 °C, respectively, is also reported; (ii) the rate constants for the reaction of the hydroxyl radical with 1-hexyn-3-ol ((5.5 ± 0.5) × 109 dm3 mol−1 s−1 at 20 °C), cinnamonitrile ((9.2 ± 0.3) × 109 dm3 mol−1 s−1 at 21 °C), and diethylthiourea ((8.0 ± 0.8) × 108 dm3 mol−1 s−1 at 22 °C). For cinnamonitrile, the temperature dependence up to 200 °C is also reported; (iii) the rate constant for the hydrogen atom reacting with 1-hexyn-3-ol ((4.3 ± 0.4) × 109 dm3 mol−1 s−1 at 20 °C). Keywords: radiolysis, corrosion inhibitors, rate constants.

scholarly journals Ability of Constitutive Models to Characterize the Temperature Dependence of Rubber Hyperelasticity and to Predict the Stress-Strain Behavior of Filled Rubber under Different Defor Mation States

Polymers ◽  
2021 ◽  
Vol 13 (3) ◽  
pp. 369
Author(s):  
Xintao Fu ◽  
Zepeng Wang ◽  
Lianxiang Ma
Keyword(s):  
Experimental Data ◽  
Temperature Dependence ◽  
Mechanical Response ◽  
Constitutive Models ◽  
Uniaxial Tensile ◽  
Uniaxial Tensile Test ◽  
Chain Model ◽  
Stress Strain ◽  
Filled Rubber ◽  
Yeoh Model

In this paper, some representative hyperelastic constitutive models of rubber materials were reviewed from the perspectives of molecular chain network statistical mechanics and continuum mechanics. Based on the advantages of existing models, an improved constitutive model was developed, and the stress–strain relationship was derived. Uniaxial tensile tests were performed on two types of filled tire compounds at different temperatures. The physical phenomena related to rubber deformation were analyzed, and the temperature dependence of the mechanical behavior of filled rubber in a larger deformation range (150% strain) was revealed from multiple angles. Based on the experimental data, the ability of several models to describe the stress–strain mechanical response of carbon black filled compound was studied, and the application limitations of some constitutive models were revealed. Combined with the experimental data, the ability of Yeoh model, Ogden model (n = 3), and improved eight-chain model to characterize the temperature dependence was studied, and the laws of temperature dependence of their parameters were revealed. By fitting the uniaxial tensile test data and comparing it with the Yeoh model, the improved eight-chain model was proved to have a better ability to predict the hyperelastic behavior of rubber materials under different deformation states. Finally, the improved eight-chain model was successfully applied to finite element analysis (FEA) and compared with the experimental data. It was found that the improved eight-chain model can accurately describe the stress–strain characteristics of filled rubber.

Interaction of Point Defects in Ice

1978 ◽  
Vol 21 (85) ◽  
pp. 115-122
Author(s):  
J. H. Bilgram ◽  
H. Gränicher
Keyword(s):  
Experimental Data ◽  
Dielectric Properties ◽  
Temperature Dependence ◽  
Point Defects ◽  
Low Frequency ◽  
Defect Concentration ◽  
Dielectric Measurements ◽  
Long Time ◽  
Nmr Techniques ◽  
Bjerrum Defect

AbstractThe interaction of point detects in ice has been neglected for a long time. Experimental data obtained from dielectric measurements on HF-doped crystals stimulated a new evaluation of the possibility of an interaction between Bjerrum defects and ions. In a previous paper it has been shown that this leads us to assume the existence of aggregates of Bjerrum defects and ions. In this paper these aggregates and Bjerrum defects are used to explain the dielectric properties of ice, especially the temperature dependence of the product of the high and low frequency conductivity σ0σ∞.The interaction of Bjerrum defects and impurity molecules leads to a dependence of the concentration of frenkel pairs on Bjerrum-defect concentration. At HF concentrations above the native Bjerrum-defect concentration the formation of a Frenkel pair is enhanced. This leads to the fast out-diffusion which has been studied in highly doped crystals by means of NMR techniques.

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