Evidence for the formation of substoichiometric species during internal oxidation of Ag-Mg alloys

Charrin, L.; Combe, A.; Cabané, F.; Cabané, J.

doi:10.1007/bf00666388

Cited by 15 publications

(10 citation statements)

References 13 publications

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“…Furthermore, at high-temperature and for high-concentration alloys (% 2 at.% or more), it has been shown that in silver alloys containing reactive solutes (Sn, Zn, Mg, Cu) there is an important lattice expansion during internal oxidation. [5][6][7][8] At low-temperature ( < 420°C), we presented analogous results in dilute Ag-Mg alloys 9,10 . The change with time of the (022) silver diffraction peak was determined and the development of an extra peak (characteristic of an expanded phase) was followed, whose intensity increases as the matrix-peak intensity decreases.…”

Section: Introductionsupporting

confidence: 70%

“…From our model 8,9 , the undistorted-matrix peak remains unchanged as elementary MgO * species and hypo-stoichiometric clusters form; the extra distorted diffraction peak is due to the formation of hyper-stoichiometric clusters. Figures 1 and 2 show the evolution versus time of the (022) diffraction peak obtained during internal oxidation at 300°C, respectively, on dilute (0.29 at.%) and concentrated (2.89 at.%) silver-magnesium alloys.…”

Section: Peak-intensity Variationsmentioning

confidence: 97%

“…Ex-situ X-ray measurements realized in a previous study, 9 (on Ag-0.5 and 1 at.%), lead to the conclusion that the thickness of the expanded layer varies as t n with n > 1; so the experimental growth rate is initially very low (about 0, for t = 0); in this last case, it is expected that experimental and theoretical growth rate curves cross each other for a higher value of t.…”

Section: Kinetics: Oxidation Front and Expanded Layermentioning

confidence: 99%

“…At the end of such a process, clusters organize themselves towards the stoichiometric oxide, giving rise to an oxygen release and a relaxation of the silver lattice. 9 The observation of the first steps of internal oxidation (with hypo-and hyper-stoichiometric cluster formation) is related to the experimental conditions, especially the temperature which must be low enough. Elsewhere, it has been also reported that the solute content and the temperature determine the formation, morphology and size of clusters.…”

Section: Introductionmentioning

confidence: 99%

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First Stages of Internal Oxidation in Ag-0.29 and 2.89 at. % Mg Single-Crystal Alloys

et al. 2006

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Internal oxidation of Ag-0.29 and 2.89 at.% Mg alloys was studied by in-situ X-ray measurements at 300°C. The kinetics and lattice-parameter changes as a function of time are discussed in terms of the formation of elementary MgO* species and non-stoichiometric clusters, during the first stages of oxidation. Studies were made using synchrotron radiation on single-crystal samples. The distorted zone, formed near the surface, was detected by measuring the position and the intensity of the (022) silver peak in the solid-solution alloy. From the diffraction-peak changes, information is deduced on the growth kinetics of the expanded layer. Oxygen diffusivity in silver, C 0 D 0 , is calculated on the basis of Wagner's law. At an early stage, the oxygen diffusivity is slightly lower than the theoretical value. During a second stage, accelerated kinetics give a very high C 0 D 0 value. We determined the O/Mg ratios at different stages during oxidation.

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Section: Introductionsupporting

confidence: 70%

Section: Peak-intensity Variationsmentioning

confidence: 97%

Section: Kinetics: Oxidation Front and Expanded Layermentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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First Stages of Internal Oxidation in Ag-0.29 and 2.89 at. % Mg Single-Crystal Alloys

et al. 2006

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“…13,[16][17][18] For a uniform oxidation and unchanged oxidation zone, the gain in weight is linearly proportional to the oxidation depth j. The importance of such representation follows from the fact that in Ag-Mg alloys this ratio may significantly exceed unity.…”

Section: A Gravimetric Data On Internal Oxidation In Airmentioning

confidence: 99%

Kinetics and mechanism of low-temperature internal oxidation of Ag–2 and 4 at.% Mg alloys

Rikel

Goldacker

1999

J. Mater. Res.

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Gravimetry and x-ray diffraction were used to study the kinetics and mechanism of internal oxidation in air at 300-600 ± C of Ag-2 and 4 at.% Mg alloys. All the features typical of the non-Wagnerian behavior in more dilute alloys (the slower initial and faster intermediate kinetics, oxygen release from the samples at the late stages, and stabilization of highly hyperstoichiometric oxides with O͞Mg up to 1.74 6 0.02) are also observed in these more concentrated alloys. A linear correlation between the lattice parameter of oxidized alloys, magnesium content, and amount of excess oxygen is found and used for analyzing the published data on the lattice parameters in other oxidized Ag-Mg alloys. Such analysis suggests that, at early stages of low-temperature oxidation, O͞Mg ratios could be higher than 4 6 0.8, which is interpreted as evidence that O-Mg interaction at these stages is the trapping of mobile O atoms by immobile Mg atoms, so that oxidation of Ag-Mg alloys can be considered as formation and subsequent decomposition of Ag-Mg-O solid solutions, and it is the decomposition stage that significantly affects the oxidation kinetics. Possible impact of these findings on optimization of alloy-sheath composition and microstructure in Bi2223͞AgMg superconducting tapes is discussed.

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An analysis of the internal oxidation of binary M-Nb alloys under low oxygen pressures at 600?800�C

et al. 1996

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Evidence for the formation of substoichiometric species during internal oxidation of Ag-Mg alloys

Cited by 15 publications

References 13 publications

First Stages of Internal Oxidation in Ag-0.29 and 2.89 at. % Mg Single-Crystal Alloys

First Stages of Internal Oxidation in Ag-0.29 and 2.89 at. % Mg Single-Crystal Alloys

Kinetics and mechanism of low-temperature internal oxidation of Ag–2 and 4 at.% Mg alloys

An analysis of the internal oxidation of binary M-Nb alloys under low oxygen pressures at 600?800�C

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