Determination of the Activation Energy for Formation and Migration of Thermal Vacancies in 2024 Aircraft Material Using Different Techniques and Methods

Defect and Diffusion Forum ◽

10.4028/www.scientific.net/ddf.337-338.19 ◽

2013 ◽

Vol 337-338 ◽

pp. 19-27

Author(s):

N.A. Kamel

Keyword(s):

Formation Enthalpy ◽

Quenching Rate ◽

Positron Annihilation Lifetime ◽

Self Diffusion ◽

A Value ◽

2024 Alloy ◽

And Migration ◽

Induced Defects ◽

Irradiation Induced Defects

Positron annihilation lifetime (PAL) , electrical and mechanical techniques have been used to study the thermal vacancies in one of the most important engineering aluminum alloys which is 2024 alloy. Quenching experiments were usually performed on thin specimens to ensure a uniform quenching rate throughout the specimen. The specimens were prepared with dimensions of 0.15 × 1.5 × 1.5cm3. After grinding, polishing and etching, samples of 2024 were homogenized for 12 h at 673 K and annealed for 90-min., before quenched in water (277 K) and then subject to positron lifetime, electrical and mechanical for measurements. From such measurements it is possible to deduce the vacancy formation enthalpy, which in combination with the results of self-diffusion measurements, give a value for migration enthalpy of the vacancy. These are very important quantities in the study of the annealing of irradiation induced defects.

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Determination of the Activation Energy for Formation and Migration of Thermal Vacancies in 401.0 Casting Aluminum Alloy

Defect and Diffusion Forum ◽

10.4028/www.scientific.net/ddf.337-338.1 ◽

2013 ◽

Vol 337-338 ◽

pp. 1-4

Author(s):

N.A. Kamel ◽

S.A. Aly ◽

A.A. Ibrahim ◽

E.A. Badawi

Keyword(s):

Aluminum Alloy ◽

Formation Enthalpy ◽

Electrical Measurements ◽

Quenching Rate ◽

Self Diffusion ◽

A Value ◽

Casting Aluminum Alloy ◽

Casting Aluminum ◽

And Migration

Electrical techniques have been used to study the thermal vacancies in 401.0 casting aluminum alloy. Quenching experiments were usually performed on thin specimens to ensure a uniform quenching rate throughout the specimen. After grinding, polishing and etching, samples of 401.0 were homogenized for 12h at 673K and annealed for 90min., before quenched in water (277K) and then subjected to electrical measurements. From such measurements it is possible to deduce the vacancy formation enthalpy, which in combination with the results of self-diffusion measurements, give a value for the migration enthalpy of the vacancy.

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Estimating the Activation Enthalpy for Defect Formation in 5754 Alloys by Using Nuclear, Electrical and Mechanical Methods

Defect and Diffusion Forum ◽

10.4028/www.scientific.net/ddf.329.29 ◽

2012 ◽

Vol 329 ◽

pp. 29-33 ◽

Cited By ~ 1

Author(s):

Alaa M. Ibrahim ◽

E.M. Hassen ◽

M. A. Abdel-Rahman ◽

Emad A. Badawi

Keyword(s):

Positron Annihilation ◽

Defect Formation ◽

Activation Enthalpy ◽

Formation Enthalpy ◽

Quenching Rate ◽

Positron Annihilation Lifetime ◽

Self Diffusion ◽

Mechanical Methods ◽

Positron Annihilation Study ◽

Induced Defects

The Positron Annihilation Lifetime Technique (PALT) Is One of the Most Important Nuclear Non-Destructive Techniques. it Was Used to Study the Activation Enthalpy for Defect Formation in 5754 Alloy. Quenching Experiments Were Usually Performed on Thin Specimens to Ensure a Uniform Quenching Rate throughout the Specimen. from such Measurements, it Is Possible to Deduce the Vacancy Formation Enthalpy which, in Combination with the Results of Self-Diffusion Measurements, Gives a Value for the Migration Enthalpy of the Vacancy. these Are Very Important Quantities in the Study of the Annealing of Irradiation-Induced Defects. the Use of the Quenching Technique in the Positron Annihilation Study Has the Advantage that it Allows a Distinction to Be Made between Vacancies and Dislocations. Correlations between Nuclear, Electrical and Mechanical Methods Have Been Carried Out after Quenching.

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Study of Compensation Defects and Electron Irradiation-Induced Defects in Undoped SI-InP by Positron Lifetime Spectroscopy

Materials Science Forum ◽

10.4028/www.scientific.net/msf.607.134 ◽

2008 ◽

Vol 607 ◽

pp. 134-136

Author(s):

Y.J. Zhang ◽

Ai Hong Deng ◽

You Wen Zhao ◽

J. Yu ◽

X.X. Yu ◽

...

Keyword(s):

Electron Irradiation ◽

Positron Lifetime ◽

Deep Level ◽

High Concentration ◽

Positron Annihilation Lifetime ◽

Donor Type ◽

Positron Lifetime Spectroscopy ◽

Transient Spectroscopy ◽

Induced Defects ◽

Irradiation Induced Defects

Positron annihilation lifetime (PAL) spectroscopy，photo-induced current transient spectroscopy (PICTS) and thermally stimulated current (TSC) have been employed to study the formation of compensation defects and their evolvement under iron phosphide (IP) ambience or pure phosphide (PP) ambience. In the formation of IP SI-InP, the diffusion of Fe atoms suppresses the formation of some open-volume defects. As to PP SI-InP, VInH4 complexes dissociate into acceptor vacancies VInHn(n-3)(n=0,1,2,3), which compensate residual donor type defects and make the sample semi-insulating. Electron irradiation-induced deep level defects have been studied by TSC in PP and IP SI-InP, respectively. In contrast to a high concentration of irradiation-induced defects in as-grown and PP annealed InP, IP SI-InP has a very low concentration of defects.

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Determination of Mobility and Charge Carriers Concentration from Ionic Conductivity in Sodium Germanate Glasses above and below Tg

ISRN Electrochemistry ◽

10.1155/2013/240571 ◽

2013 ◽

Vol 2013 ◽

pp. 1-10 ◽

Cited By ~ 3

Author(s):

Marcio Luis Ferreira Nascimento

Keyword(s):

Ionic Conductivity ◽

Charge Carrier ◽

Formation Enthalpy ◽

Large Temperature ◽

Complete Test ◽

Ionic Displacement ◽

The Difference ◽

And Migration ◽

Positively Charged

The ionic conductivity and viscous flow data of xNa2O·(1−x)GeO2, 0.05<x<0.296, have been collected in a large temperature range, below and above their glass transition temperatures (Tg). A microscopic model is proposed, assuming that the ionic displacement would result from the migration of interstitial positively charged cationic pairs whose concentration is an activated function of temperature. Below Tg, their migration is also an activated mechanism, but a “free volume” would prevail above this temperature. This discontinuity in the migration mechanism justifies a Dienes-Macedo-Litovitz (DML) relationship to be representative of conductivity data above Tg and an Arrhenius law below. According to this model, the enthalpy deduced by the fit of high temperature data using a DML equation would correspond to the charge carrier formation, whose migration enthalpy, below Tg, could be deduced by the difference between the activation energy measured in the Arrhenius domain and the charge carrier formation enthalpy. To reduce the number of adjustable parameters numerical values were physically justified. We also applied a complete test for conductivity below Tg, using the so-called weak electrolyte model, splitting activation enthalpy EσA into formation and migration enthalpies and also explaining the variation of pre-exponential term of conductivity with composition.

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Self-Diffusion, Conductivity and Transport Numbers in Alkali Halide Single Crystals

Zeitschrift für Naturforschung A ◽

10.1515/zna-1971-0521 ◽

1971 ◽

Vol 26 (5) ◽

pp. 915-921 ◽

Cited By ~ 2

Author(s):

Franqois Beniere ◽

Michelle Beniere ◽

Marius Chemla

Keyword(s):

Diffusion Coefficients ◽

Correlation Effect ◽

Einstein Relation ◽

Transport Numbers ◽

Self Diffusion ◽

Anion Vacancies ◽

Cation And Anion Vacancies ◽

Complete Set ◽

And Migration

Abstract The self-diffusion coefficients of the anions and cations have been measured in pure and doped NaCl and KCl crystals, together with the ionic conductivity. The experimental results give evidence for migration mechanisms via free cation and anion vacancies and vacancy pairs. Analysis of the complete set of diffusion data leads to the determination of the entropy and enthalpy of formation and migration of these defects. In a second part, the diffusion coefficients via free vacancies are compared with the conductivity data in order to investigate the validity of the Nernst-Einstein relation. This relation is found to be verified within 2%, in NaCl as well as in KCl, no appreciable correlation effect being detected.

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Vitamin A Value of Plant Food Provitamin A - Evaluated by the Stable Isotope Technologies

International Journal for Vitamin and Nutrition Research ◽

10.1024/0300-9831/a000183 ◽

2014 ◽

Vol 84 (Supplement 1) ◽

pp. 25-29 ◽

Cited By ~ 7

Author(s):

Guangwen Tang

Keyword(s):

Stable Isotope ◽

Vitamin A ◽

Provitamin A ◽

Animal Origin ◽

Plant Food ◽

Plant Foods ◽

A Value ◽

Provitamin A Carotenoids ◽

Β Carotene

Humans need vitamin A and obtain essential vitamin A by conversion of plant foods rich in provitamin A and/or absorption of preformed vitamin A from foods of animal origin. The determination of the vitamin A value of plant foods rich in provitamin A is important but has challenges. The aim of this paper is to review the progress over last 80 years following the discovery on the conversion of β-carotene to vitamin A and the various techniques including stable isotope technologies that have been developed to determine vitamin A values of plant provitamin A (mainly β-carotene). These include applications from using radioactive β-carotene and vitamin A, depletion-repletion with vitamin A and β-carotene, and measuring postprandial chylomicron fractions after feeding a β-carotene rich diet, to using stable isotopes as tracers to follow the absorption and conversion of plant food provitamin A carotenoids (mainly β-carotene) in humans. These approaches have greatly promoted our understanding of the absorption and conversion of β-carotene to vitamin A. Stable isotope labeled plant foods are useful for determining the overall bioavailability of provitamin A carotenoids from specific foods. Locally obtained plant foods can provide vitamin A and prevent deficiency of vitamin A, a remaining worldwide concern.

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Self-diffusion study of bile salt-monoolein micelles determination of the intermicellar bile salt concentration

Journal de Chimie Physique ◽

10.1051/jcp/1983800315 ◽

1983 ◽

Vol 80 ◽

pp. 315-323 ◽

Cited By ~ 6

Author(s):

Marc Lindheimer ◽

Jean-Claude Montet ◽

Roselyne Bontemps ◽

Jacques Rouviere ◽

Bernard Brun

Keyword(s):

Bile Salt ◽

Salt Concentration ◽

Diffusion Study ◽

Bile Salt Concentration ◽

Self Diffusion

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Temperature Dependence of G and D’ Phonons in Monolayer to Few-Layer Graphene with Vacancies

Nanoscale Research Letters ◽

10.1186/s11671-020-03414-w ◽

2020 ◽

Vol 15 (1) ◽

Author(s):

Mingming Yang ◽

Longlong Wang ◽

Xiaofen Qiao ◽

Yi Liu ◽

Yufan Liu ◽

...

Keyword(s):

Negative Temperature Coefficient ◽

Negative Temperature ◽

Intrinsic Properties ◽

Temperature Dependent ◽

Phonon Interaction ◽

Electron Phonon Interaction ◽

Layer Graphene ◽

A Value ◽

Few Layer Graphene

Abstract The defects into the hexagonal network of a sp2-hybridized carbon atom have been demonstrated to have a significant influence on intrinsic properties of graphene systems. In this paper, we presented a study of temperature-dependent Raman spectra of G peak and D’ band at low temperatures from 78 to 318 K in defective monolayer to few-layer graphene induced by ion C+ bombardment under the determination of vacancy uniformity. Defects lead to the increase of the negative temperature coefficient of G peak, with a value almost identical to that of D’ band. However, the variation of frequency and linewidth of G peak with layer number is contrary to D’ band. It derives from the related electron-phonon interaction in G and D’ phonon in the disorder-induced Raman scattering process. Our results are helpful to understand the mechanism of temperature-dependent phonons in graphene-based materials and provide valuable information on thermal properties of defects for the application of graphene-based devices.

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