scholarly journals Effect of chemical composition on mass transfer in Y2Ti2O7 under oxygen potential gradient at high temperatures

2021 ◽  
Vol 129 (1) ◽  
pp. 22-31
Author(s):  
Makoto TANAKA ◽  
Tsuneaki MATSUDAIRA ◽  
Emi KAWAI ◽  
Naoki KAWASHIMA ◽  
Ushio MATSUMOTO ◽  
...  
Keyword(s):  
Mass Transfer ◽  
Chemical Composition ◽  
High Temperatures ◽  
Oxygen Potential ◽  
Potential Gradient

Effects of an oxygen potential gradient and water vapor on mass transfer in polycrystalline alumina at high temperatures

2018 ◽  
Vol 151 ◽  
pp. 21-30 ◽  
Author(s):  
Tsuneaki Matsudaira ◽  
Satoshi Kitaoka ◽  
Naoya Shibata ◽  
Yuichi Ikuhara ◽  
Miyuki Takeuchi ◽  
...  
Keyword(s):  
Mass Transfer ◽  
Water Vapor ◽  
High Temperatures ◽  
Oxygen Potential ◽  
Potential Gradient ◽  
Polycrystalline Alumina

Effect of Oxygen Potential Gradient on Mass Transfer in Polycrystalline α-Alumina at High Temperature

2016 ◽  
Vol 879 ◽  
pp. 966-971 ◽  
Author(s):  
Satoshi Kitaoka ◽  
Tsuneaki Matsudaira ◽  
Tsubasa Nakagawa ◽  
Naoya Shibata ◽  
Yuichi Ikuhara
Keyword(s):  
Mass Transfer ◽  
Diffusion Coefficients ◽  
Oxygen Potential ◽  
Oxygen Permeability ◽  
Electronic Conductivity ◽  
Potential Gradient ◽  
High Oxygen Partial Pressure ◽  
Self Diffusion ◽  
Permeability Constants ◽  
Effect Of Oxygen

The oxygen permeability of polycrystalline α-alumina wafers, which served as model alumina scales formed on heat-resistant alloys, was evaluated at a temperature of 1873 K. Mass transfer along grain boundaries (GBs) in an alumina wafer exposed to a large oxygen potential gradient (dμO), where both oxygen and aluminum mutually diffuse along GBs, was analyzed using 18O2 and SIMS. 18O was concentrated at GB ridges on the high oxygen partial pressure (PO2(hi)) surface and along the GBs near the PO2(hi) surface. 18O adsorbed on the surface diffused almost immediately to surface GBs, resulting in the formation of new alumina by reaction with aluminum diffusing outward along the GBs. Oxygen GB diffusion coefficients in the vicinity of the PO2(hi) surface were determined from the 18O depth profile along each GB for the 18O map of the cross section of the exposed alumina wafer. The oxygen GB diffusion coefficients were comparable to the values calculated from the oxygen permeability constants assuming an electronic conductivity and were obviously lower than those of oxygen GB self-diffusion without an oxygen potential gradient.

Mass transfer in polycrystalline ytterbium monosilicate under oxygen potential gradients at high temperatures

2020 ◽  
Author(s):  
Tsuneaki Matsudaira ◽  
Masashi Wada ◽  
Naoki Kawashima ◽  
Miyuki Takeuchi ◽  
Daisaku Yokoe ◽  
...  
Keyword(s):  
Mass Transfer ◽  
High Temperatures ◽  
Oxygen Potential ◽  
Potential Gradients

scholarly journals Mass Transfer in Polycrystalline Alumina under Oxygen Potential Gradients at High Temperatures

Materia Japan ◽  
2009 ◽  
Vol 48 (6) ◽  
pp. 317-320 ◽  
Author(s):  
Satoshi Kitaoka ◽  
Tsuneaki Matsudaira ◽  
Masashi Wada
Keyword(s):  
Mass Transfer ◽  
High Temperatures ◽  
Oxygen Potential ◽  
Polycrystalline Alumina ◽  
Potential Gradients

Mass transfer in polycrystalline ytterbium disilicate under oxygen potential gradients at high temperatures

2017 ◽  
Vol 135 ◽  
pp. 372-381 ◽  
Author(s):  
Masashi Wada ◽  
Tsuneaki Matsudaira ◽  
Naoki Kawashima ◽  
Satoshi Kitaoka ◽  
Masasuke Takata
Keyword(s):  
Mass Transfer ◽  
High Temperatures ◽  
Oxygen Potential ◽  
Potential Gradients

Effect of Dopant Configuration on Oxygen Shielding Properties of Polycrystalline Alumina

2014 ◽  
Vol 783-786 ◽  
pp. 1452-1457
Author(s):  
Tsuneaki Matsudaira ◽  
Masashi Wada ◽  
Makoto Tanaka ◽  
Yutaka Kagawa ◽  
Satoshi Kitaoka
Keyword(s):  
Grain Boundary ◽  
High Temperatures ◽  
Oxygen Pressure ◽  
Oxygen Potential ◽  
Oxygen Permeability ◽  
Potential Gradient ◽  
Bilayer Structure ◽  
Polycrystalline Alumina ◽  
Shielding Properties ◽  
Partial Oxygen

The oxygen permeability of polycrystalline α-alumina wafers, which served as model alumina layers, under an oxygen potential gradient ΔPO2 was evaluated at a temperature of 1873 K. When mutual grain boundary (GB) diffusion of oxygen and aluminum occurred in wafers subjected to a steep ΔPO2, the oxygen and aluminum fluxes at the inflow side of the wafer were significantly smaller than those at the outflow side. It was noteworthy that Lu and Hf segregation at the GBs selectively reduced the mobility of oxygen and aluminum, respectively. It was found that a wafer with a bilayer structure, in which a Lu-doped layer was exposed to a low partial oxygen pressure (PO2) and a Hf-doped layer was exposed to a high PO2, exhibited excellent oxygen shielding properties at high temperatures.

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