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.

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.

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.

Preliminary Positron Lifetime Results on Free Volumes in Cyclodextrins

2010 ◽  
Vol 666 ◽  
pp. 99-102 ◽  
Author(s):  
Maria Fatima Ferreira Marques ◽  
A.M.G. Moreira Da Silva ◽  
P.M. Gordo ◽  
Z. Kajcsos
Keyword(s):  
Positron Annihilation ◽  
Free Volume ◽  
Positron Lifetime ◽  
Positron Annihilation Lifetime Spectroscopy ◽  
Positron Source ◽  
Lifetime Component ◽  
Positron Annihilation Lifetime ◽  
Long Lifetime

Positron annihilation lifetime spectroscopy was used to study the free-volume parameters in various pure -, - and -cyclodextrins samples and, in the case of β-cyclodextrin, with inclusion of S-carvone and thymoquinone. The results clearly indicate the presence of long lifetime components related to Ps-formation. The data show that the addition of S-carvone to β-cyclodextrin results in a decrease of o-Ps lifetime that we ascribe to a reduction of free volume holes from 81.8 to 63.7 Å3. The long lifetime component disappears when thymoquinone is added to -cyclodextrin, indicating this substance acts as an o-Ps quencher. For all samples studied, a decrease in the long lifetime component values was observed with increasing source in situ time, a result that might be attributed to the irradiation of the sample by the 22Na positron source.

Isochronal and Isothermal Annealing of Wrought Aluminum Alloy

2011 ◽  
Vol 319-320 ◽  
pp. 37-42
Author(s):  
M.A. Abdel-Rahman ◽  
N.A. Kamel ◽  
Abdullah A. Refeay ◽  
Yahia A. Lotfy ◽  
Emad A. Badawi
Keyword(s):  
Activation Energy ◽  
Aluminum Alloy ◽  
Positron Annihilation ◽  
Material Science ◽  
Isothermal Annealing ◽  
Electrical Measurements ◽  
Positron Annihilation Lifetime ◽  
Nuclear Techniques ◽  
7075 Alloy ◽  
Wrought Aluminum

Positron annihilation lifetime (PAL) is one of the most important nuclear techniques used in material science. Electrical measurements are also used in material science. Samples of 25 % deformation have been used for these studies. Both positron annihilation lifetime and electrical measurements were used to determined the activation energy of migration the dislocation in 7075 alloy. The isothermal annealing measurements were performed at 643, 663, 683 and 703 K. The activation energy of migration the dislocation are obtained as 1.35 ± 0.16 eV and 1.25 ± 0.05 eV for positron annihilation lifetime and electrical techniques respectively.

Positron Annihilation in Thermally Treated Co-Zr-V Metallic Glasses

2010 ◽  
Vol 666 ◽  
pp. 58-61
Author(s):  
Ewa Dryzek ◽  
Jacek Jaworski ◽  
Eric Fleury ◽  
Andrzej Budziak
Keyword(s):  
Heat Treatment ◽  
Magnetic Properties ◽  
Chemical Composition ◽  
Positron Annihilation ◽  
Metallic Glasses ◽  
Annealing Temperature ◽  
Positron Lifetime ◽  
Positron Annihilation Lifetime Spectroscopy ◽  
Positron Annihilation Lifetime ◽  
Microstructure Changes

Positron annihilation lifetime spectroscopy (PALS) has been applied to study if the microstructure changes in Co80Zr10V10 and Co65Zr10V25 metallic glasses after heat treatment. Samples in as-quenched state were isothermally annealed at chosen temperatures in the temperature range 100°C - 580°C for 1 hour. In spite of differences of chemical composition and magnetic properties the obtained dependencies of positron lifetime on annealing temperature do not differ significantly for lower temperatures. The higher increase of positron lifetime for Co65Zr10V25 than that for Co80Zr10V10 indicates differences in crystallization in the two metallic glasses studied.

scholarly journals Determining the positron lifetime of a material using Positron Annihilation Lifetime Spectroscopy

2019 ◽  
Vol 25 ◽  
pp. 245
Author(s):  
K. Triantou ◽  
K. Mergia ◽  
I. E. Stamatelatos ◽  
G. Apostolopoulos ◽  
S. Messoloras
Keyword(s):  
Positron Annihilation ◽  
Positron Lifetime ◽  
Positron Annihilation Lifetime Spectroscopy ◽  
Positron Annihilation Lifetime

N/A

Sealed 22Na Sources for Positron Annihilation Lifetime Spectroscopy

2012 ◽  
Vol 733 ◽  
pp. 310-313 ◽  
Author(s):  
Masato Yamawaki ◽  
Yoshinori Kobayashi ◽  
K. Ito ◽  
Mikio Matsumoto ◽  
Hidetake Ishizu ◽  
...  
Keyword(s):  
Positron Annihilation ◽  
Positron Lifetime ◽  
Positron Annihilation Lifetime Spectroscopy ◽  
Legal Regulations ◽  
High Quality ◽  
Positron Annihilation Lifetime ◽  
Lifetime Spectrum ◽  
Long Lifetime ◽  
Sealed Source ◽  
Sealing Materials

Sealed radioactive sources of 22Na for positron annihilation lifetime spectroscopy (PALS), free from the legal regulations, are commercially available from an American company. However, thick foils are used to seal 22Na in these sources and large fractions of the positrons annihilate in the sealing materials. Further, it is pointed out that a long lifetime component over 1 ns appears in the positron lifetime spectrum acquired with the Kapton sealed source (POSK-22, IPL Inc.). In this research, attempts were made to develop high quality sealed positron sources, potentially free from regulations, for ubiquitous application of PALS. The sources prepared in the present work are of high quality and applicable to our new PALS, which does not require sample cutting and is potentially applicable to truly nondestructive, onsite inspection of various materials

Epoxide Moisture Absorption Studied by Positron Lifetime Spectroscopy

2012 ◽  
Vol 730-732 ◽  
pp. 988-993
Author(s):  
J.M.M. Luís ◽  
Marco Duarte Naia ◽  
Maria Fatima Ferreira Marques ◽  
J.J.L. Morais ◽  
P.M. Gordo
Keyword(s):  
Positron Annihilation ◽  
Moisture Absorption ◽  
Positron Lifetime ◽  
Positron Annihilation Lifetime Spectroscopy ◽  
Positron Annihilation Lifetime ◽  
Physical Chemical ◽  
Molecular Scale ◽  
Macroscopic Properties ◽  
Positron Lifetime Spectroscopy

In the last years there have been made several studies, involving many materials, with the aim of trying to explain some physical, chemical and mechanical macroscopic properties of these materials, across the study of the free volumes at the atomic and molecular scale. The positron annihilation lifetime spectroscopy (PALS) is one of the most widely used in this type of studies, and it was here used to characterize the free volumes fraction of a commercial epoxy and trying to understand the mechanism associated with the process of moisture absorption which leads to an increase of mass and volume on this commercial epoxy.

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