Defect Structures during Incubation Period of Void Swelling in Austenitic and Ferritic Alloys Studied by Positron Annihilation Spectroscopy

2013 ◽  
Vol 1526 ◽  
Author(s):  
S. Huang ◽  
K. Miyawaki ◽  
K. Tsujikawa ◽  
M. Horiki ◽  
T. Yoshiie ◽  
...  
Keyword(s):  
Stainless Steel ◽  
Positron Annihilation ◽  
Incubation Period ◽  
Positron Annihilation Spectroscopy ◽  
Defect Structures ◽  
Lifetime Measurements ◽  
Ferritic Alloys ◽  
Positron Annihilation Lifetime ◽  
Annealing Temperatures ◽  
Void Swelling

ABSTRACTIn order to understand the vacancy behavior during incubation period before steady state void swelling, positron annihilation lifetime measurements was performed after isochronal annealing of austenitic stainless steel (Ti added modified SUS316SS) and ferritic stainless steel (F82H) irradiated by neutrons and electrons to a dose of 0.2 dpa. By electron and neutron irradiations below 363 K, vacancies and nano-voids containing of few vacancies were formed in both alloys. By increasing annealing temperatures, the lifetime decreased without forming nano-voids. The change of lifetime during the annealing indicated the formation and growth of staking fault tetrahedra (Ti added modified SUS316SS) and the annihilation of vacancies at precipitates (F82H).

Positron Annihilation Lifetime Measurements in Collagen Biopolymer

1998 ◽  
Vol 530 ◽  
Author(s):  
S. Siles ◽  
G. Moya ◽  
X.H. Li ◽  
J. Kansy ◽  
P. Moser
Keyword(s):  
Positron Annihilation ◽  
Amorphous Region ◽  
Positron Annihilation Spectroscopy ◽  
Lifetime Data ◽  
Spectroscopy Technique ◽  
Lifetime Measurements ◽  
Lifetime Distributions ◽  
Positron Annihilation Lifetime ◽  
Coincidence System ◽  
Three Components

AbstractLifetime measurement in Positron Annihilation Spectroscopy (PAS) is applied to the study of free-volume collagen characteristics as a function of concentration. The lifetimes of positrons were obtained by a conventional fast-fast coincidence system. All lifetime data are fitted in three components by using the computer program POSITRON FIT and resolved. For each concentration, lifetime distributions were analyzed in order to obtain the different components, thus we have observed three components of which a long component τ3. This long lived component can be associated with a pick-off annihilation of ortho-positronium (o-Ps) trapped in free volumes of amorphous region. This investigation shows the potential of the positron annihilation spectroscopy technique in the study of biopolymer microstructures.

Seeking the Good Fitting Procedure of PALS Polymer Spectra

2008 ◽  
Vol 607 ◽  
pp. 64-66
Author(s):  
Nicolas Laforest ◽  
Jérémie De Baerdemaeker ◽  
Corine Bas ◽  
Charles Dauwe
Keyword(s):  
Experimental Data ◽  
Low Temperature ◽  
Positron Annihilation ◽  
Physical Meaning ◽  
Lifetime Measurements ◽  
Positron Annihilation Lifetime ◽  
Fitting Procedure ◽  
Fitting Procedures ◽  
Blob Model

Positron annihilation lifetime measurements on polymethylmethacrylate (PMMA) at low temperature were performed. Different discrete fitting procedures have been used to analyze the experimental data. It shows that the extracted parameters depend strongly on the fitting procedure. The physical meaning of the results is discussed. The blob model seems to give the best annihilation parameters.

Annihilation Lifetime Spectroscopy Using Positrons from Bremsstrahlung Production

2012 ◽  
Vol 331 ◽  
pp. 41-52 ◽  
Author(s):  
Andreas Wagner ◽  
Wolfgang Anwand ◽  
Maik Butterling ◽  
Thomas E. Cowan ◽  
Fine Fiedler ◽  
...  
Keyword(s):  
Positron Annihilation ◽  
Linear Accelerator ◽  
Electron Accelerator ◽  
Positron Annihilation Spectroscopy ◽  
Doppler Broadening ◽  
Electron Linear Accelerator ◽  
Positron Annihilation Lifetime ◽  
Electron Bremsstrahlung ◽  
New Type ◽  
Set Up

A new type of a positron annihilation lifetime spectroscopy (PALS) system has been set up at the superconducting electron accelerator ELBE [ at Helmholtz-Zentrum Dresden-Rossendorf. In contrast to existing source-based PALS systems, the approach described here makes use of an intense photon beam from electron bremsstrahlung which converts through pair production into positrons inside the sample under study. The article focusses on the production of intense bremsstrahlung using a superconducting electron linear accelerator, the production of positrons inside the sample under study, the efficient detector setup which allows for annihilation lifetime and Doppler-broadening spectroscopy simultaneously. Selected examples of positron annihilation spectroscopy are presented.

Effects of Helium Production and Displacement Damage on Microstructural Evolution and Mechanical Properties in Helium-Implanted Austenitic Stainless Steel and Ferritic/Martensitic Steel

2021 ◽  
Vol 1024 ◽  
pp. 53-69
Author(s):  
Eiichi Wakai ◽  
Shuhei Nogami ◽  
Akira Hasegawa ◽  
Nariaki Okubo ◽  
Shigeru Takaya ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Stainless Steel ◽  
Austenitic Stainless Steel ◽  
Microstructural Evolution ◽  
Martensitic Steel ◽  
Microstructural Development ◽  
Displacement Damage ◽  
Lifetime Measurements ◽  
Helium Concentration ◽  
Positron Annihilation Lifetime

The effects of helium concentration and displacement damage on microstructural evolution at low dpa and low helium concentration were mainly investigated in specimens of austenitic stainless steel 316FR or SUS304 and a high chromium martensitic steel (HCM12A). The 316FR and HCM12A specimens were implanted uniformly with helium at 823 K up to 30 appm-He or 50 appm-He by 50 MeV cyclotron accelerator using energy degraders. After the helium implantation, the microstructures were examined by a transmission electron microscopy and positron annihilation lifetime measurements. Irradiation hardening behaviors were analyzed using SUS304 and HCM12A steels at 823 K implanted with He ion up to 100 appm with different He/dpa ratios in the HIT ion irradiation experiments and the hardening behaviors were examined by nano indentation method. In the irradiation and annealing specimens, these mechanical properties and microstructures were examined to understand the effects of helium production, displacement damage and annealing on microstructural development, and kinetic Monte Carlo (kMC) simulations were also performed to understand the microstructural development, and the results were compared with the results of TEM observation and positron annihilation lifetime measurements. Important some differences in the microstructural developments such as cavity formation and growth between austenitic stainless steel and martensitic steel were observed in low dpa and low helium concentration conditions.

Study of PRIMAVERA steel samples by positron annihilation spectroscopy technique II – Lifetime measurements

2012 ◽  
Vol 421 (1-3) ◽  
pp. 97-103 ◽  
Author(s):  
V. Krsjak ◽  
V. Grafutin ◽  
O. Ilyukhina ◽  
R. Burcl ◽  
A. Ballesteros ◽  
...  
Keyword(s):  
Positron Annihilation ◽  
Positron Annihilation Spectroscopy ◽  
Spectroscopy Technique ◽  
Lifetime Measurements

POSITRON INTERACTION IN POLYMERS

2004 ◽  
Vol 19 (23) ◽  
pp. 3951-3959 ◽  
Author(s):  
CORINE BAS ◽  
N. DOMINIQUE ALBÉROLA ◽  
MARIE-FRANCE BARTHE ◽  
JÉRÉMIE De BAERDEMAEKER ◽  
CHARLES DAUWE
Keyword(s):  
Positron Annihilation ◽  
Chemical Structure ◽  
Positron Beam ◽  
Positron Annihilation Spectroscopy ◽  
Hole Size ◽  
Doppler Broadening ◽  
Positron Source ◽  
Positron Annihilation Lifetime ◽  
Doppler Broadening Spectra ◽  
Variable Energy

A series of dense copolyimide membranes was characterized using positron annihilation spectroscopy. The positron annihilation lifetime spectroscopy performed on film with a classical positron source gives informations on the positronium fraction formed and also on the hole size within the film. The Doppler broadening spectra (DBS) of the gamma annihilation rays coupled with a variable energy positron beam allow the microstructural analyses as a function of the film depth. Experimental data were also linked to the chemical structure of the polyimides. It was found that the presence of the fluorine atoms strongly affects the positron annihilitation process and especially the DBS responses.

Micro Structural Changes in Welded AlCuLi-Alloys by Positron Annihilation Spectroscopy, SAXS and DSC

2016 ◽  
Vol 877 ◽  
pp. 387-392
Author(s):  
Danny Petschke ◽  
Torsten E.M. Staab
Keyword(s):  
Positron Annihilation ◽  
Structural Changes ◽  
Base Material ◽  
Positron Annihilation Spectroscopy ◽  
Weld Nugget ◽  
Scanning Calorimetry ◽  
Positron Annihilation Lifetime ◽  
Friction Stir ◽  
X Ray Scattering ◽  
Type Size

We follow changes in the micro structure at several distances from the weld nugget of friction stir welded AlCuLi-alloy (AA2198) plates occurring due to the tool movement and the created heat by employing different methods: Small Angle X-ray Scattering (SAXS), giving information on type, size and density of precipitates, Differential Scanning Calorimetry (DSC), giving information on formed precipitates by their dissolution signal, and positron annihilation lifetime spectroscopy (PALS), being sensitive to vacancies and dislocations as well as to the formation and growth of precipitates. We start by characterizing the base material as a reference and proceed via the heat-affected zone to the weld nugget. By the use of complementary methods, we obtain information on structure, kind and distribution of precipitates and correlate this with hardness measurements.

scholarly journals Study of multiblock polyamide-6/Poly-(isoprene) copolymers by positron annihilation spectroscopy

2008 ◽  
Vol 6 (4) ◽  
pp. 575-580 ◽  
Author(s):  
R. Bryaskova ◽  
R. Mateva ◽  
N. Djourelov ◽  
M. Krasteva
Keyword(s):  
Positron Annihilation ◽  
Free Volume ◽  
Main Chain ◽  
Positron Annihilation Spectroscopy ◽  
Polyamide 6 ◽  
Positron Annihilation Lifetime Spectroscopy ◽  
Degree Of Crystallinity ◽  
Doppler Broadening ◽  
Annihilation Line ◽  
Positron Annihilation Lifetime

AbstractPositron annihilation lifetime spectroscopy (PALS) has been used to determine the free volume in multiblock polyamide-6/poly-(isoprene) copolymers (PA-6/PI), synthesized via activated anionic bulk copolymerization. The diisocyanate functionalized telechelic PI, blocked with caprolactam (CL) has been used as a commoner and an activator at the same time. The elastic PI block incorporated into the main chain of PA-6 affects the amorphous and crystal phase of the copolymer leading to changing in degree of crystallinity. The positron annihilation lifetime spectroscopy (PAL) and Doppler broadening of annihilation line (DBAL) technique in a set of pure PA-6 and PA-6/PI copolymers with two different compositions have been applied and evaluation of the size of free-volume holes (pores), localized mainly in the disordered regions of the PA-6/PI copolymer by measuring the o-Ps lifetime (τ3) and o-Ps intensity (I3) has been performed.

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