Advances in positron studies of age hardening in light alloys

Somoza, A.; Dupasquier, A.; Ferragut, R.

doi:10.1002/pssc.200982103

Cited by 11 publications

(3 citation statements)

References 25 publications

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“…But longer lifetime 2 of this second component slightly rises in thick films. So the positrons are trapped more strongly in thick films due to glass additives near grain boundaries in these materials and void agglomeration [33][34][35][36] during technological process.…”

Section: Resultsmentioning

confidence: 99%

Multilayer thick-film structures based on spinel ceramics

et al. 2014

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Temperature-sensitive thick films based on spinel-type semiconducting ceramics of different chemical composition Cu 0.1 Ni 0.1 Co 1.6 Mn 1.2 O 4 (with p + -types of electrical conductivity), Cu 0.1 Ni 0.8 Co 0.2 Mn 1.9 O 4 (with p-types of electrical conductivity), and their multilayers of p + -p and p-p + -p structures were fabricated and studied. These thick-film elements possess good electrophysical characteristics before and after long-term ageing test at 170°C. It is shown that degradation processes connected with diffusion of metallic Ag into grain boundaries occur in one-layer p-and p + -conductive thick films. The p + -p structures were of high stability, the relative electrical drift being no more than 1%. Positron trapping processes in so-called "free" thick-film structures based on spinel-type Cu 0.1 Ni 0.8 Co 0.2 Mn 1.9 O 4 ceramics are studied. It is shown that two-state positron trapping model is appropriate for an adequate description of changes caused by additional glass phase in these materials. The observed behaviour of defect-related component in the fit of the experimentally measured positron lifetime spectra for thick films in comparison with bulk ceramics testifies in favour of agglomeration of free volume entities during technological process. PACS Nos.: 68.65.Ac, 85.40.Xx, 81.05.Mh.Résumé : Nous avons fabriqué et étudié des films épais et sensibles à la température, de semi-conducteurs céramiques de type spinelle de différentes compositions chimiques : Cu 0.1 Ni 0.1 Co 1.6 Mn 1.2 O 4 (avec conductivité électrique de type p + ), Cu 0.1 Ni 0.8 Co 0.2 Mn 1.9 O 4 (avec conductivité électrique de type p) ainsi que leurs structures multicouches p + -p et p-p + -p. Ces films épais possèdent de bonnes caractéristiques électro-physiques avant et après un processus de vieillissement à 170°C. Nous montrons que la dégradation associée à la diffusion de Ag dans les joints de grain apparaît dans les films épais à une couche de type p + ou p. Les structures p + -p sont très stables, la dérive électrique ne dépassant pas 1 %. Nous étudions le mécanisme de piégeage de positron dans les films épais libres de type céramique spinelle Cu 0.1 Ni 0.8 Co 0.2 Mn 1.9 O 4 . Nous montrons que le modèle à deux états de piégeage de positron est approprié pour une description adéquate des changements causés par l'ajout d'une phase verre dans ces matériaux. Le comportement observé de la composante défaut dans le lissage des spectres expérimentaux de temps de vie mesurés des positrons dans les films épais comparés à des céramiques en volume, suggère l'agglomération de volumes libres dans le processus de formation. [Traduit par la Rédaction]

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Section: Resultsmentioning

confidence: 99%

Multilayer thick-film structures based on spinel ceramics

et al. 2014

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“…Lifetime of positrons depends on the local electron density of the medium: it increases in the presence of a defect, characterized by a lower electron density with respect to the bulk. Therefore, the positron is a useful probe to investigate subnanometric defects in solids, such as vacancies in metals 3 or defects in semiconductors, 4 as well as to follow structural transformations those materials undergo. Sensitivity is very high in a metal, ppm concentrations are sufficient to produce a clearly detectable signal.…”

Section: Introductionmentioning

confidence: 99%

Mesoporous materials for antihydrogen production

et al. 2013

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Antimatter is barely known by the chemist community and this article has the vocation to explain how antimatter, in particular antihydrogen, can be obtained, as well as to show how mesoporous materials could be used as a further improvement for the production of antimatter at very low temperatures (below 1 K). The first experiments with mesoporous materials highlighted in this review show very promising and exciting results. Mesoporous materials such as mesoporous silicon, mesoporous material films, pellets of MCM-41 and silica aerogel show remarkable features for antihydrogen formation. Yet, the characteristics for the best future mesoporous materials (e.g. pore sizes, pore connectivity, shape, surface chemistry) remain to be clearly identified. For now among the best candidates are pellets of MCM-41 and aerogel with pore sizes between 10 and 30 nm, possessing hydrophobic patches on their surface to avoid ice formation at low temperature. From a fundamental standpoint, antimatter experiments could help to shed light on open issues, such as the apparent asymmetry between matter and antimatter in our universe and the gravitational behaviour of antimatter. To this purpose, basic studies on antimatter are necessary and a convenient production of antimatter is required. It is exactly where mesoporous materials could be very useful.

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“…Owing to a significant role of free volume in a structural relaxation, not only atomic-sensitive, but also void-sensitive techniques should be used to obtain complementary parts of information. In this view, the positron annihilation lifetime (PAL) spectroscopy is known to be one of the most promising techniques for characterization of free volumes (open-volume holes, inner pores, vacancies and vacancy-like agglomerations) in crystals, liquids, polymers and glasses on a subnanometer scale [6][7][8]. Thus, PAL investigations of ageing phenomena in metallic light alloys and organic polymers [6][7][8][9][10][11][12][13] allowed significant progress in the models of natural structural relaxation in these materials [6][7][8][9][10][11][12][13].…”

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confidence: 99%

PAL signature of physical ageing in chalcogenide glasses

Ingram

Kozdraś

Shpotyuk

et al. 2012

Physica Status Solidi (b)

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Kinetics of physical ageing (PhA) far below the glass transition temperature (T g ) is studied by positron annihilation lifetime and differential scanning calorimetry techniques for vitreous As 20 Se 80 as typical representative of network glasses. The increased density fluctuations are shown to be responsible for the initial stage of PhA in this glass at below-T g temperatures. These fluctuations are correlated with changes in thermodynamic parameters of structural relaxation through the glassto-supercooled liquid transition interval. General shrinkage, occurred during the next stage of PhA, is shown to be determined by the ability of system to release these redundant open volumes from the glass bulk through densification process of glass network.

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Advances in positron studies of age hardening in light alloys

Cited by 11 publications

References 25 publications

Multilayer thick-film structures based on spinel ceramics

Multilayer thick-film structures based on spinel ceramics

Mesoporous materials for antihydrogen production

PAL signature of physical ageing in chalcogenide glasses

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