Oxide particles in Ag-Mg alloys formed by internal oxidation

Charrin, L.; Combe, A.; Cabané, J.

doi:10.1007/bf00665631

Cited by 25 publications

(7 citation statements)

References 12 publications

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“…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. A comparison between these results and data obtained by gravimetric measurements 11 shows that sub-stoichiometric clusters (with magnesium excess) are formed, in a first step, without expansion. Matrix distortion occurs, in a second step, according to the evolution of the earliest clusters by the fixation of an oxygen excess (hyper-stoichiometric clusters) during a coalescence process.…”

Section: Introductionmentioning

confidence: 63%

“…The evolution from hypo-to hyper-stoechiometric clusters needs a significant trapping of oxygen atom s. 11,20,21 The oxidized-silver-layer expansion depends on the oxygen atom-to-magnesium atom ratio. The oxygen excess may be evaluated from the relation given by Rikel and Goldacker 20 :…”

Section: Oxygen Excessmentioning

confidence: 99%

“…This velocity V is inversely proportional to the solute concentration. 1,11 During internal oxidation of silver-magnesium alloys, velocity is expressed by the first derivative with time of Eq.1, i.e. : V = C o D o /C Mg gf 11 , where C Mg is the magnesium concentration in silver.…”

Section: Peak-intensity Variationsmentioning

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: Introductionmentioning

confidence: 63%

Section: Oxygen Excessmentioning

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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“…The gravimetric data show that all the features typical of the low-temperature oxidation behavior in more dilute alloys (the slow early stage, the more rapid intermediate stage, and oxygen release at the late stage, 17,18 ) are also observed in more concentrated Ag-2 and 4% Mg alloys (Figs. 1 and 2), and there is a fairly good quantitative correspondence between our data and the data of other studies (Table I).…”

Section: A Kinetics Of Internal Oxidationmentioning

confidence: 88%

“…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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