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

Wada, M.; Matsudaira, Tsuneaki; Kitaoka, Satoshi

doi:10.2109/jcersj2.119.832

Cited by 38 publications

(89 citation statements)

References 27 publications

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“…7. SEM micrograph of the P O2 (hi) surface and cross-section of the non-doped alumina exposed to P O2 (hi)/P O2 (lo) = 10 5 Pa/8 © 10 ¹8 Pa at 1923 K for 10 h. 27) Fig. 8.…”

Section: Mass-transfer In Polycrystalline Alumina Scalementioning

confidence: 99%

“…6. 27) Because the P O2 (hi) surface shown in Fig. 7 was exposed under the same P O2 (hi) value in Fig.…”

Section: Mutual Gb Diffusion Of Both Oxygen and Aluminummentioning

confidence: 99%

“…27)29) The oxygen permeabil- (7)(9) and (12). The arrow corresponds to the exposure condition from Fig.…”

Section: Mutual Gb Diffusion Of Both Oxygen and Aluminummentioning

confidence: 99%

“…In this study, the equilibrium P O2 corresponding to ® O at the junction interface between the scale and alloy, such as Fe0.17Cr0.2Al (in atomic%), was estimated thermodynamically using the FactSage free energy minimization computer code, in a similar fashion to estimations of the interface between an alumina scale and CoNiCrAlY. 27),39) The calculated equilibrium P O2 at the interface was 10 ¹24 Pa at 1373 K. Figure 11 shows flux distributions for oxygen and aluminum in the scale exposed to P O2 (hi)/P O2 (lo) = , respectively. For the non-doped scale, as shown in Fig.…”

Section: ¹13mentioning

confidence: 99%

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Mass transfer in polycrystalline alumina under oxygen potential gradients at high temperatures

Kitaoka

2016

J. Ceram. Soc. Japan

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The mass-transfer mechanisms of polycrystalline alumina with and without oxygen reactive elements (REs) such as Ln (Y and Lu) and Hf were investigated by evaluation of the oxygen permeability through alumina wafers, which served as a model for alumina scale, at accelerated temperatures up to 1923 K. Oxygen permeation proceeded via grain boundary (GB) diffusion of oxygen from the higher oxygen partial pressure [P O2 (hi)] surface side to the lower P O2 [P O2 (lo)] surface side, along with the simultaneous GB diffusion of aluminum in the opposite direction, maintaining the GibbsDuhem relationship. The chemical potentials, GB diffusion coefficients, and fluxes of oxygen and aluminum in alumina wafers with applied oxygen potential gradients (d® O ) were calculated from the oxygen permeability constants. The fluxes of oxygen and aluminum at the outflow side of the wafer were significantly larger than those at the inflow side. Ln and Hf segregation at the GBs selectively reduced the diffusivity of oxygen and aluminum, respectively. Thus, the mesoscopic dopant arrangements, which were selected by taking into consideration the behavior of the diffusion species and the role of dopants, enabled the alumina layers to have enhanced oxygen shielding capability 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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“…7. SEM micrograph of the P O2 (hi) surface and cross-section of the non-doped alumina exposed to P O2 (hi)/P O2 (lo) = 10 5 Pa/8 © 10 ¹8 Pa at 1923 K for 10 h. 27) Fig. 8.…”

Section: Mass-transfer In Polycrystalline Alumina Scalementioning

confidence: 99%

“…6. 27) Because the P O2 (hi) surface shown in Fig. 7 was exposed under the same P O2 (hi) value in Fig.…”

Section: Mutual Gb Diffusion Of Both Oxygen and Aluminummentioning

confidence: 99%

“…27)29) The oxygen permeabil- (7)(9) and (12). The arrow corresponds to the exposure condition from Fig.…”

Section: Mutual Gb Diffusion Of Both Oxygen and Aluminummentioning

confidence: 99%

Section: ¹13mentioning

confidence: 99%

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Mass transfer in polycrystalline alumina under oxygen potential gradients at high temperatures

Kitaoka

2016

J. Ceram. Soc. Japan

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“…Therefore, it is extremely difficult to quantitatively determine the degree of influence for individual factors that influence the movement of each diffusion species. The oxygen permeability technique with polycrystalline α-alumina wafer, which served as a model scale, is thus expected to be very useful to accurately evaluate mass-transfer through the wafers because the dµ O applied to the wafers and the diffusion length are constant [16][17][18][19][20][21][22][23][24].…”

Section: +mentioning

confidence: 99%

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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Control of Mass‐Transfer Through Grain Boundaries in a Protective Alumina Layer by Dopant Configuration in Advanced EBCS

Kitaoka

Matsudaira

Wada

et al. 2014

Ceramic Transactions Series

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

Cited by 38 publications

References 27 publications

Mass transfer in polycrystalline alumina under oxygen potential gradients at high temperatures

Mass transfer in polycrystalline alumina under oxygen potential gradients at high temperatures

Grain Boundary Engineering of Alumina Ceramics

Control of Mass‐Transfer Through Grain Boundaries in a Protective Alumina Layer by Dopant Configuration in Advanced EBCS

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