Oxygen Diffusion in Alumina. Application to Synthetic and Thermally Grown Al&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;3&lt;/sub&gt;

Chevalier, Sébastien; Lesage, B.; Legros, C.; Borchardt, Günter; Strehl, G.; Kilo, Martin

doi:10.4028/www.scientific.net/ddf.237-240.899

Cited by 18 publications

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“…17) and 18) was presumed to be P O2 ðIIÞ/ P O2 ðIÞ = 10 5 Pa/10 ¹23 Pa. The activation energy for oxygen GB diffusion determined by the oxygen permeation technique in this study approached those of the scales 17), 18) and Ni-dispersed polycrystalline Al 2 O 3 19) rather than the obtained values 14)16) for annealing in homogeneous, high-P O2 environments, as shown in Table 1. Therefore, the circumstances of the oxygen diffusion field during O 2 permeation may be analogous to those of the actual scales.…”

Section: Mutual Gb Transport Of Aluminum and Oxygenmentioning

confidence: 76%

“…D Ogb ¤ increased from the P O2 ðIIÞ surface to the P O2 ðIÞ surface, while D Algb ¤ decreased. The flux of both aluminum and oxygen Scale (ODS-MA956, Y-doped) [17] Scale (Imphy, Zr-doped) [17] Scale (Fe-20Cr-5Al) [18] Scale (Fe-20Cr-5Al-0.1Y) [18] 17) used to determine the oxygen GB diffusion coefficients from 18 O depth profiles of the scale using SIMS. The arrows correspond to data at x/L = 1.…”

Section: Discussionmentioning

confidence: 99%

“…17) was determined at an x/L of about 0.870.95, but there was no description of the measurement range of the alumina scale in the paper. 18) If the measurement range of the scale on FeCrAl 18) is assumed to be equal to those of the Y-doped (ODS-MA956) or Zr-doped alloys (Imphy), 17) the D Ogb ¤ estimated from the oxygen permeation coincides with that of the scale, which did not contain these dopants. Because the doped ions were probably segregated at the GBs in the scales, 2) the dopants presumably inhibited the mobility of oxygen, resulting in GB strengthening due to the bonding strength between the dopant and oxygen, and to site blocking due to ionic-size mismatch.…”

Section: Mutual Gb Transport Of Aluminum and Oxygenmentioning

confidence: 99%

“…Furthermore, aluminum and oxygen were concluded to interdiffuse along the GBs without any synergistic effects, satisfying the GibbsDuhem equation. The ratios of aluminum and oxygen Non-doped Bicrystal [15] Non-doped polycrystal [14] Scale (ODS-MA956, Y-doped) [17] Non-doped Polycrystal [16] Scale (Imphy, Zr-doped) [17] 10 Scale (Fe-20Cr-5Al) [18] Scale (Fe-20Cr-5Al-0.1Y) [18] Diffusion species Figure 7 shows the distributions of chemical potentials, GB diffusion coefficients, and charged flux of aluminum and oxygen in the depth direction of a polycrystalline Al 2 O 3 wafer exposed at 1923 K at P O2 ðIIÞ/P O2 ðIÞ = 10 5 Pa/10 ¹8 Pa. ® O decreased with decreasing x/L in an inverse relationship to ® Al , in accordance with the GibbsDuhem equation. D Ogb ¤ increased with decreasing x/L, while D Algb ¤ decreased.…”

Section: Mutual Gb Transport Of Aluminum and Oxygenmentioning

confidence: 99%

“…But, D Algb ¤ showed the opposite distribution of D Ogb ¤, resulting in 1/10 10 of the D Ogb ¤ at the P O2 ðIÞ subsurface. The oxygen diffusion coefficients of the scales were generally determined from 18 O depth profiles of the scales using secondary ion mass spectroscopy (SIMS) or nuclear reaction analysis (NRA). Thus, it was important to consider which position in the scale was measured, because the GB diffusion coefficients varied strongly in the scale, as shown in Fig.…”

Section: Mutual Gb Transport Of Aluminum and Oxygenmentioning

confidence: 99%

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Mutual grain-boundary transport of aluminum and oxygen in polycrystalline Al2O3 under oxygen potential gradients at high temperatures

Wada

Matsudaira

Kitaoka

2011

J. Ceram. Soc. Japan

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The oxygen permeability of non-doped polycrystalline Al 2 O 3 wafers under steep oxygen potential gradients (ÁP O2 ) was evaluated at temperatures of up to 1973 K. The oxygen permeation occurred by grain boundary (GB) diffusion of oxygen from the higher oxygen partial pressure (P O2 ) side to the lower P O2 side and by the simultaneous GB diffusion of aluminum in the opposite direction. The exposed Al 2 O 3 was an electronic conductor, and both the aluminum and oxygen ions migrated without any acceleration or inhibition due to the interdiffusion. The ratios of the aluminum and oxygen flux to the oxygen permeation under ÁP O2 conditions at which mutual GB transport of the ions occurred depended strongly on ÁP O2 . The chemical potentials, GB diffusion coefficients, and the flux of aluminum and oxygen were estimated as functions of position in the depth direction of the wafers.

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Section: Mutual Gb Transport Of Aluminum and Oxygenmentioning

confidence: 76%

Section: Discussionmentioning

confidence: 99%

Section: Mutual Gb Transport Of Aluminum and Oxygenmentioning

confidence: 99%

Section: Mutual Gb Transport Of Aluminum and Oxygenmentioning

confidence: 99%

Section: Mutual Gb Transport Of Aluminum and Oxygenmentioning

confidence: 99%

See 3 more Smart Citations

Mutual grain-boundary transport of aluminum and oxygen in polycrystalline Al2O3 under oxygen potential gradients at high temperatures

Wada

Matsudaira

Kitaoka

2011

J. Ceram. Soc. Japan

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Grain Boundary Engineering of Alumina Ceramics

et al. 2018

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Oxygen permeability through alumina wafers was evaluated at high temperatures up to 1923 K to elucidate the mass-transfer mechanisms of polycrystalline alumina and serve as a model for protective alumina film formed on heat-resistant alloys. Oxygen permeation proceeded via grain boundary (GB) diffusion of oxygen from the higher oxygen partial pressure (P O2 ) surface side to the lower P O2 surface side, along with the simultaneous GB diffusion of aluminum in the opposite direction to maintain the Gibbs-Duhem relationship. Oxygen GB diffusion coefficients in the vicinity of the P O2 (hi) surface were lower than those of oxygen GB self-diffusion without an oxygen potential gradient (dµ O ). When dµ O was applied to the wafer, the oxygen and aluminum fluxes at the outflow side of the wafer were significantly larger than those at the inflow side. Ln (Y and Lu) and Hf segregation at the GBs selectively reduced the diffusivity of oxygen and aluminum, respectively. Thus, the mesoscopic arrangements of segregating dopants, which were selected by taking into consideration the behavior of the diffusion species and the role of dopants, enabled the alumina film to have enhanced oxygen shielding capability and structural stability at high temperatures. Furthermore, the GB diffusion data derived from the oxygen permeation experiments were compared to those for alumina scale formed by the so-called two-stage oxidation of alumina-forming alloys.

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High-Temperature Oxidation of Fe3Al and Fe3Al–Zr Intermetallics

et al. 2009

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The oxidation behavior of Fe 3 Al and Fe 3 Al-Zr intermetallic compounds was tested in synthetic air in the temperature range 900-1200°C. The addition of Zr showed a significant effect on the high-temperature oxidation behavior. The total weight gain after 100 h oxidation of Fe 3 Al at 1200°C was around three times more than that for Fe 3 Al-Zr materials. Zr-containing intermetallics exhibited abnormal kinetics between 900 and 1100°C, due to the presence and transformation of transient alumina into stable a-Al 2 O 3 . Zr-doped Fe 3 Al oxidation behavior under cyclic tests at 1100°C was improved by delaying the breakaway oxidation to 80 cycles, in comparison to 5 cycles on the undoped Fe 3 Al alloys. The oxidation improvements could be related to the segregation of Zr at alumina grain boundaries and to the presence of Zr oxide second-phase particles at the metal-oxide interface and in the external part of the alumina scale. The change of oxidation mechanisms, observed using oxygen-isotope experiments followed by secondary-ion mass spectrometry, was ascribed to Zr segregation at alumina grain boundaries.

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Oxygen Diffusion in Alumina. Application to Synthetic and Thermally Grown Al<sub>2</sub>O<sub>3</sub>

Cited by 18 publications

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Mutual grain-boundary transport of aluminum and oxygen in polycrystalline Al2O3 under oxygen potential gradients at high temperatures

Mutual grain-boundary transport of aluminum and oxygen in polycrystalline Al2O3 under oxygen potential gradients at high temperatures

Grain Boundary Engineering of Alumina Ceramics

High-Temperature Oxidation of Fe3Al and Fe3Al–Zr Intermetallics

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