Defect Diffusion Models in NMR and Dielectric Relaxation

1978 ◽  
Vol 33 (11) ◽  
pp. 1294-1306 ◽  
Author(s):  
Rainer Kimmich ◽  
Gerhard Voigt
Keyword(s):  
Diffusion Process ◽  
Dielectric Relaxation ◽  
Diffusion Models ◽  
Defect Concentration ◽  
Relaxation Behaviour ◽  
Defect Diffusion ◽  
Rotational Isomers ◽  
Mean Lifetime ◽  
The Mean

The effect of diffusing defects such as vacancies, displacements, torsions, and rotational isomers on the nmr and dielectric relaxation behaviour is treated under various aspects. The influences of the dimensionality of the diffusion process, of the mutual hindrance, of the defect concentration, of the defect length and of the mean lifetime are derived and discussed.

DETECTING DEFECTS IN AIRCRAFT MATERIALS BY NUCLEAR TECHNIQUE (PAS)

2005 ◽  
Vol 19 (22) ◽  
pp. 3475-3482
Author(s):  
EMAD. A. BADAWI
Keyword(s):  
Aluminum Alloy ◽  
Dislocation Density ◽  
Material Science ◽  
Positron Annihilation Spectroscopy ◽  
Defect Concentration ◽  
Nuclear Technique ◽  
Nuclear Techniques ◽  
Mean Lifetime ◽  
The Mean ◽  
7075 Alloy

Positron annihilation spectroscopy (PAS) is one of the nuclear techniques used in material science. The present measurements are used to study the behavior of defect concentration in one of the most important materials — aluminum alloy — which is a 7075 alloy. It has been shown that positrons can become trapped in imperfect locations in solids and their mean lifetime can be influenced by changes in the concentration of such defects. No changes have been observed in the mean lifetime values after the saturation of defect concentration. The mean lifetime and trapping rates were studied for samples deformed up to 58.3%. The concentration of defect range varies (from 1015 to 1018 cm-3) at the thickness reduction, (from 2.3 to 58.3%). The range of the dislocation density varies (from 108 to 1011 cm/cm3).

DISLOCATION AND DEFECT DENSITIES BY PAT IN 2024 AIRCRAFT MATERIAL USING TWO DIFFERENT ACTIVITY SOURCES

2005 ◽  
Vol 12 (03) ◽  
pp. 463-468 ◽  
Author(s):  
M. A. ABDEL-RAHMAN ◽  
M. S. ABDALLAH ◽  
EMAD A. BADAWI
Keyword(s):  
Positron Annihilation ◽  
Material Science ◽  
Defect Concentration ◽  
2024 Aluminum Alloy ◽  
Nuclear Technique ◽  
Positron Annihilation Lifetime ◽  
Mean Lifetime ◽  
Aircraft Material ◽  
The Mean ◽  
Defect Densities

Positron annihilation lifetime spectroscopy (PALS) is a nuclear technique used in material science. Positron annihilation lifetime technique (PALT) measurements are used to study the behavior of defect concentration and dislocation density in a set of 2024 aluminum alloy. It has been shown that positrons can become trapped at imperfect locations in solids and their mean lifetime can be influenced by changes in the concentrations of such defects. No changes were observed in the mean lifetime after defect concentration became saturated. The mean lifetime and trapping rates for the samples deformed up to 36.4 percent. The concentration of defects range from 1.133 × 1016 to 2.061 × 1018 cm-3 at strains from 1.7 to 22.7%.

DETECTING DEFECTS IN AIRCRAFT MATERIALS BY NUCLEAR TECHNIQUE (PAS)

2005 ◽  
Vol 12 (01) ◽  
pp. 1-6 ◽  
Author(s):  
EMAD. A. BADAWI
Keyword(s):  
Aluminum Alloys ◽  
Dislocation Density ◽  
Material Science ◽  
Positron Annihilation Spectroscopy ◽  
Defect Concentration ◽  
Nuclear Technique ◽  
Nuclear Techniques ◽  
Mean Lifetime ◽  
The Mean ◽  
7075 Alloy

Positron annihilation spectroscopy (PAS) is one of the nuclear techniques used in material science. The present measurements are used to study the behavior of defect concentration in one of the most important materials aluminum alloys which is the 7075 alloy. It has been shown that positrons can become trapped at imperfect locations in solids and their mean lifetime can be influenced by changes in the concentration of such defects. No changes have been observed in the mean lifetime values after the saturation of defect concentration. The mean lifetime and trapping rates are studied for samples deformed up to 58.3%. The concentration of defect range vary from 1015 to 1018 cm -3 at the thickness reduction from 2.3 to 58.3%. The dislocation density varies from 108 to 1011 cm/cm 3.

Consequences of Restricted Defect Diffusion on NMR and Dielectric Relaxation

1976 ◽  
Vol 31 (7) ◽  
pp. 693-696 ◽  
Author(s):  
R. Kimmich
Keyword(s):  
Diffusion Process ◽  
Dielectric Relaxation ◽  
Finite Length ◽  
Defect Diffusion ◽  
One Dimensional ◽  
Limited Diffusion ◽  
Reflecting Barriers ◽  
Nuclear Magnetic

Abstract Nuclear magnetic and dielectric relaxation formulas are given for a model of limited diffusion of defects. The limitation is introduced by the assumption of fixed reflecting barriers on both sides of the defect. The diffusion process is assumed to be one-dimensional and continuous. The effect of the finite length of the defects is included in the presented treatment.

STUDY OF TRAPPING RATE AND DEFECT DENSITY IN AlSi11.35Mg0.23 BY POSITRON ANNIHILATION TECHNIQUE

2004 ◽  
Vol 11 (04n05) ◽  
pp. 427-432 ◽  
Author(s):  
M. A. ABDEL-RAHMAN ◽  
M. S. ABDALLAH ◽  
EMAD A. BADAWI
Keyword(s):  
Positron Annihilation ◽  
Defect Density ◽  
Defect Concentration ◽  
Thickness Reduction ◽  
Trapping Rate ◽  
Positron Annihilation Lifetime ◽  
Maximum Value ◽  
Mean Lifetime ◽  
The Mean

The measurements of Positron Annihilation Lifetime Technique (PALT) have been performed on AlSi 11.35 Mg 0.23 Alloys. It has been shown that positrons can become trapped at imperfect locations in solids and their mean lifetime can be influenced by changes in the concentration of such defects. No change has been observed in the mean lifetime values at the saturation of defect concentration. The trapping rates of positrons can be determined for thickness reduction up to 11% for dislocation. The concentration of defect (ρ') range varies from 8.65×1015 to 2.35×1018 cm -3 up to the maximum value of strain (ε) 0.23.

Positron Lifetime in Deformed AlSi10.9Mg0.17Sr0.06 Alloys

2007 ◽  
Vol 261-262 ◽  
pp. 55-60 ◽  
Author(s):  
M.A. Abdel-Rahman ◽  
M.S. Abdallah ◽  
Emad A. Badawi
Keyword(s):  
Dislocation Density ◽  
Positron Annihilation ◽  
Material Science ◽  
Positron Lifetime ◽  
Defect Concentration ◽  
Positron Annihilation Lifetime Spectroscopy ◽  
Positron Annihilation Lifetime ◽  
Nuclear Techniques ◽  
Mean Lifetime ◽  
The Mean

Positron annihilation lifetime spectroscopy (PALS) is one of the nuclear techniques used in material science. (PALT) measurements are used to study the behaviour of the defect concentration in a set of AlSi10.9Mg0.17Sr0.06 alloys. It has been shown that positrons can become trapped at imperfect locations in solids, and that their mean lifetime can be influenced by changes in the concentration of such defects. No changes have been observed in the mean lifetime values following saturation of the defect concentration. The mean lifetime and trapping rates were studied for samples deformed up to 34.9 %. The concentrations of defects range vary from 5.194x1015 to 1.934x1018 cm-3 for thickness reductions of 2.2 to 34.9 %. The range of the dislocation density varies from 1.465x 108 to 5.454x1010 cm/cm3 over the same range of deformations.

Temperature Dependences in the O + OH → O2 + H Reaction. Quasiclassical Trajectory Calculation

1993 ◽  
Vol 58 (2) ◽  
pp. 234-243 ◽  
Author(s):  
Viliam Klimo ◽  
Martina Bittererová ◽  
Stanislav Biskupič ◽  
Ján Urban ◽  
Miroslav Micov
Keyword(s):  
Temperature Dependence ◽  
Energy Surface ◽  
Analytical Form ◽  
Mean Values ◽  
Quantum Numbers ◽  
Mean Lifetime ◽  
Temperature Dependences ◽  
Quasiclassical Trajectory Calculation ◽  
The Mean ◽  
Combustion Processes

The reaction O + OH → O2 + H in conditions of combustion of hydrocarbons and polymers was modelled by using the method of quasiclassical trajectories. The potential energy surface was determined by the multiconfiguration interaction method and fitted with the analytical form of the extended LEPS function. Attention was paid to the mean values of the vibrational and rotational quantum numbers of O2 molecules and their temperature dependence. The temperature dependence of the mean lifetime of the OOH collision complex was also examined. The calculated rate constants were analyzed and compared with the experimental data over the temperature region of the combustion processes.

Solitons, defect diffusion, and dielectric relaxation of polymers

1980 ◽  
Vol 73 (8) ◽  
pp. 4022-4025 ◽  
Author(s):  
James L. Skinner ◽  
Peter G. Wolynes
Keyword(s):  
Dielectric Relaxation ◽  
Defect Diffusion
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