Positron annihilation studies on the nature and thermal behaviour of irradiation induced defects in tungsten

Lhuillier, Pierre-Emile; Barthe, M.F.; Desgardin, P.; Egger, Werner; Sperr, P.

doi:10.1002/pssc.200982114

Cited by 51 publications

(35 citation statements)

References 9 publications

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“…• [253,256,259], and Fe and ferritic-martensitic steels [257,260,262]. For this area, nuclear reaction analysis reveals itself to be a very powerful tool because specific reactions exist for almost every isotope 2 H(D), 3 H(T) and 3 He namely: (1) D(d, p0) 3 He or D( 3 He, p0) 4 He, (2) T(d, n) 4 He, and (3) 3 He(d, p0) 4 He.…”

Section: Discussionmentioning

confidence: 99%

Helium mobility in advanced nuclear ceramics

Agarwal

Trocellier

Serruys

et al. 2014

Nuclear Instruments and Methods in Physics Research Section B:

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Section: Discussionmentioning

confidence: 99%

Helium mobility in advanced nuclear ceramics

Agarwal

Trocellier

Serruys

et al. 2014

Nuclear Instruments and Methods in Physics Research Section B:

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“…Before moving on to the investigation of vacancies in W-Ta and W-V alloys, we evaluate the energies of formation of small vacancy clusters in bcc-W, which are important for modeling kinetics of nucleation and growth of voids in tungsten under irradiation. [57][58][59] Table III shows the calculated formation and binding energies of small clusters of vacancies (N v = 2-6) calculated for pure tungsten using the PBE-GGA exchange-correlation functional 43 with semicore electrons included in the PAW potential implemented within the VASP code. The calculated formation energies for the first-nearestneighbor and second-nearest-neighbor divacancies are 6.624 and 6.989 eV, respectively, in agreement with values found previously (6.71 and 6.93 eV) using the PLATO code and atomiclike orbital basis sets.…”

Section: Point Defect Propertiesmentioning

confidence: 99%

Phase stability, point defects, and elastic properties of W-V and W-Ta alloys

et al. 2011

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The structure and phase stability of binary tungsten-vanadium and tungsten-tantalum alloys are investigated over a broad range of alloy compositions using ab initio and cluster expansion methods. The alloys are characterized by the negative enthalpy of mixing across the entire composition range. Complex intermetallic compounds are predicted by ab initio calculations as the lowest energy structures for both alloys. The effect of atomic relaxation on the enthalpy of mixing is almost negligible in W-V, but is substantial in W-Ta alloys. Canonical Monte Carlo simulations are used for predicting the order-disorder transition temperatures for both alloys. Differences in the short-range order between the two alloys are explained by the opposite signs of the second nearest-neighbour cluster interaction coefficients for W-V and W-Ta. Using the predicted ground-state structures, we evaluate the monovacancy formation energies and show that in W-Ta alloys they are highly sensitive to the alloy composition and the local environment of a vacancy site, varying from 3 to 5 eV. In the dilute tungsten alloy limit, a 111 self-interstitial atom crowdion defect forms a configuration strongly bound to a vanadium solute atom, whereas interaction between the same defect and a tantalum solute atom is repulsive. Values of elastic constants computed for all the ground-state structures and several metastable cubic alloy structures are used for assessing the effect of alloying on mechanical properties. Values of the Young modulus and the Poisson ratio, as well as the empirical Rice-Thompson criterion, are applied to screening the alloys, to assess the effect of chemical composition on ductility.

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“…In order to better understand its swelling and embrittlement observed in special irradiation conditions, we use PAS to study the vacancy defects properties in this material. We have first shown the migration and agglomeration of single vacancy in the temperature range from 473 to 600K [9] and its interaction with helium [10]. More recently we have observed the formation of vacancy clusters in self ion irradiated W and the effect of the temperature on the size of these clusters.…”

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Positron Annihilation Spectroscopy to Characterize Irradiation Induced Vacancy Type Defects in Materials for Nuclear Fission and Fusion

Barthe

2016

EPJ Web of Conferences

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In nuclear reactors, materials are submitted to irradiations and modification of their macroscopic properties such as swelling or hardening is observed… It is of first importance to understand the origin of these evolutions and how damage at the atomic scale such as vacancy and interstitials type defects can interact with each other or with solutes and impurities to make the microstructure evolved. So the properties of defects have to be determined.Positron annihilation spectroscopy (PAS) is a well-established technique to characterize materials [1]. Due to its positive charge, positron is sensitive to the local variations of the Coulomb potential in solids. As the anti-particle of the electron, both particles can annihilate leading to the emission of gamma rays with energy depending on the momentum of the electron positron annihilated pair. The detection of these gamma rays arises original information on the defects because positron can be trapped and annihilate in localized state such as vacancies. Two different and complementary annihilation characteristics can be measured. Firstly Positron Annihilation Lifetime Spectrometer (PALS) allows to measure the positron lifetime which depends on the local electron density at the annihilation site. The second characteristic is the momentum distribution of the electron positron annihilated pairs and is obtained by measuring the energy spectrum of the gamma annihilation rays using a Doppler Broadening Spectrometer (DBS). Both characteristics give the signature of the defects and allow determining some of their properties such as their nature, concentration, chemical environment... By using slow positron accelerators which produce monokinetic positrons beams with energy varying from 0.1 to 30 keV it is possible to study the depth profile of defects in thin layers from 0.1 to about 5 µm depending on the density of materials with a resolution of the order of 0.1xdepth. 22Na source based beams [2] or user facilities taking advantages of high positrons flux available around nuclear reactor (FRMII, Garching [3]) or LINAC( as in AIST in Japan [4]) are now available to study defects in materials. PAS has numerous advantages among them, it is non-destructive and can be used for conducting as well as insulating materials crystalline or amorphous. This technique is especially useful to probe vacancy defects in metals for which it is one of the only direct characterization. The annihilation characteristics can be predicted by first principle calculations and these data when available can help to identify defects. Sensitive to the single vacancy, PAS can allow to determine the size of the vacancy clusters up to a maximum of 1 nm approximately in the concentration range from 10 15 to a few 10 18 cm -3 .In nuclear science this technique is very powerful to characterize not only damage induced by irradiation but also to determine some fundamental properties of defects that are required for modeling of the microstructural evolution of materials such as formation, migration, agglomeratio...

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Positron annihilation studies on the nature and thermal behaviour of irradiation induced defects in tungsten

Cited by 51 publications

References 9 publications

Helium mobility in advanced nuclear ceramics

Helium mobility in advanced nuclear ceramics

Phase stability, point defects, and elastic properties of W-V and W-Ta alloys

Positron Annihilation Spectroscopy to Characterize Irradiation Induced Vacancy Type Defects in Materials for Nuclear Fission and Fusion

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