Self-diffusion of Co2+ ions in CoSO4 in agar gel medium: Concentration dependence of obstruction effect and activation energy

1985 ◽  
Vol 96 (4) ◽  
pp. 435-441 ◽  
Author(s):  
S. F. Patil ◽  
N. G. Adhyapak ◽  
S. N. Patel
Keyword(s):  
Activation Energy ◽  
Concentration Dependence ◽  
Agar Gel ◽  
Self Diffusion ◽  
Medium Concentration

The contribution of friction stress to the creep behaviour of the nickel-base in situ composite, γ—γ'-Cr 3 C 2

1980 ◽  
Vol 373 (1752) ◽  
pp. 93-109 ◽  
Keyword(s):  
Activation Energy ◽  
Creep Behaviour ◽  
Friction Stress ◽  
Matrix Alloy ◽  
Dislocation Motion ◽  
Self Diffusion ◽  
The Matrix ◽  
Nickel Base ◽  
Distribution Of Stress

Transient creep following stress reductions has been analysed by the method described by McLean (1980) to determine the friction stress σ 0 as a function of temperature and directional solidification conditions for the γ-γ'-Cr 3 Cr 2 in-situ composite and for the γ-γ' matrix alloy. These values of σ 0 are identical to the flow stresses at creep strain rates and can be identified with the sums of the barriers to dislocation motion through the matrix by climb around γ'-particles and Orowan bowing between the carbide fibres. The friction stress and the kinetics of deformation of the composite are determined by the matrix behaviour, whereas its creep strength depends on the distribution of stress between fibre and matrix. When the steady-state creep behaviour of γ-γ'-Cr 3 C 2 is analysed by using the usual power law description in terms of the effective stress σ — σ 0 , rather than the applied stress σ, the stress exponent is ca 4 and the activation energy is similar to the activation energy of self-diffusion for nickel. The results provide strong evidence for the operation of recovery-creep in both the composite and matrix alloys.

Doping Effect in Nickel Oxide

2009 ◽  
Vol 289-292 ◽  
pp. 775-782 ◽  
Author(s):  
Zbigniew Jurasz ◽  
Krzysztof Adamaszek ◽  
Romuald Janik ◽  
Zbigniew Grzesik ◽  
Stanisław Mrowec
Keyword(s):  
Activation Energy ◽  
Nickel Oxide ◽  
High Temperatures ◽  
Oxygen Pressure ◽  
Pressure Dependence ◽  
Oxidation Rate ◽  
Doping Effect ◽  
Self Diffusion ◽  
Electron Holes ◽  
Influence Of Impurities

Detailed investigations of nonstoichiometry as well as chemical and self-diffusion in nickel oxide have shown that doubly ionised cation vacancies and electron holes are the predominant defects in this material. The present work is an attempt to demonstrate that aliovalent impurities (Cr, Al, Na and Li) may considerably influence the concentration of these defects and, consequently, the oxidation rate of nickel at high temperatures. It has been shown that small amounts of tri-valent impurities (Cr, Al) bring about an increase of the oxidation rate, while mono-valent ones (Li, Na) decrease the rate of oxidation. These phenomena may satisfactorily be explained in terms of a doping effect. All experiments have been carried out as a function of temperature (1373-1673 K) and oxygen pressure (1-105 Pa) and consequently, it was possible to determine the influence of impurities not only on the oxidation rate but also on the activation energy of reaction and its pressure dependence. The results of these investigations could again be elucidated in terms of doping effect.

Concentration dependence of the self-diffusion coefficients of water in electrolyte solutions

1974 ◽  
Vol 14 (6) ◽  
pp. 915-918
Author(s):  
A. M. Sazonov ◽  
V. M. Olevskii ◽  
A. B. Porai-Koshits ◽  
V. N. Skobolev ◽  
G. A. Shmuilovich
Keyword(s):  
Concentration Dependence ◽  
Diffusion Coefficients ◽  
Electrolyte Solutions ◽  
The Self ◽  
Self Diffusion

Generalized concentration dependence of globular protein self-diffusion coefficients in aqueous solutions

Biopolymers ◽  
2002 ◽  
Vol 63 (2) ◽  
pp. 132-140 ◽  
Author(s):  
Irina V. Nesmelova ◽  
Vladimir D. Skirda ◽  
Vladimir D. Fedotov
Keyword(s):  
Aqueous Solutions ◽  
Concentration Dependence ◽  
Diffusion Coefficients ◽  
Globular Protein ◽  
Self Diffusion

High Temperature Creep Behavior and Effects of Stacking Fault Energy in Mg-Y and Mg-Y-Zn Dilute Solid Solution Alloys

2014 ◽  
Vol 783-786 ◽  
pp. 491-496
Author(s):  
Mayumi Suzuki ◽  
Yasuyuki Murata ◽  
Kyosuke Yoshimi
Keyword(s):  
Activation Energy ◽  
Solid Solution ◽  
Creep Behavior ◽  
Ternary Alloys ◽  
Dislocation Creep ◽  
Prismatic Slip ◽  
Dislocation Slip ◽  
Self Diffusion ◽  
Controlling Mechanism ◽  
Hot Rolled

Compressive creep behavior of hot-rolled (40%) Mg-Y binary and Mg-Y-Zn ternary dilute solid solution alloys are investigated in this study. Creep strength is substantially improved by the addition of zinc. Activation Energy for creep in Mg-Y and Mg-Y-Zn alloys are around 200 kJ/mol at the temperature range from 480 to 570 K. These values are higher than the activation energy for self-diffusion coefficient in magnesium (135 kJ/mol). Many stacking faults, which are planar type defects are observed on the basal planes of the magnesium matrix in Mg-Y-Zn ternary alloys. TEM observation has been revealed that the non-basal a-dislocation slip is significantly activated by these alloys. The rate controlling mechanism of Mg-Y and Mg-Y-Zn dilute alloys are considered to the cross-slip or prismatic-slip controlled dislocation creep with high activation energy for creep, more than 1.5 times higher than the activation energy for creep controlled dislocation climb.

TEMPERATURE COEFFICIENTS FOR SELF-DIFFUSION IN SOLUTION

1954 ◽  
Vol 32 (2) ◽  
pp. 71-78 ◽  
Author(s):  
C. J. Krauss ◽  
J. W. T. Spinks
Keyword(s):  
Activation Energy ◽  
Aqueous Solutions ◽  
Infinite Dilution ◽  
Kcal Mole ◽  
Self Diffusion ◽  
Temperature Coefficients ◽  
Sodium Dihydrogen

Coefficients of self-diffusion have been measured for aqueous solutions of sodium dihydrogen phosphates from 1 molar to 10−4 molar and at temperatures of 15, 25, 35, and 45 °C. The activation energy of self-diffusion has been calculated for various concentrations. It decreases from 5.4 kcal./mole at 0.9 M to 4.3 kcal./mole. at infinite dilution.

c , T-Dependence of the Self Diffusion in Concentrated Aqueous Sucrose Solutions

1994 ◽  
Vol 49 (3-4) ◽  
pp. 258-264 ◽  
Author(s):  
D. Girlich ◽  
H.-D. Lüdemann ◽  
C. Buttersack ◽  
K. Buchholz
Keyword(s):  
Field Gradient ◽  
Concentration Dependence ◽  
Diffusion Coefficients ◽  
The Self ◽  
Water Molecules ◽  
Pulsed Field Gradient Nmr ◽  
Pulsed Field ◽  
Self Diffusion ◽  
Sucrose Solutions ◽  
Wide Range

The self diffusion coefficients D of the water molecules and of sucrose have been determined by the pulsed field gradient NMR technique over a wide range of temperatures and concentrations (cmax: 70% w/w suc.). All temperature dependencies can be fitted to a Vogel- Tammann-Fulcher equation. The isothermic concentration dependence of D for the sucrose is given by a simple exponential concentration dependence

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