The Effects of Oxygen Potential Gradients on Mass Transfer in Polycrystalline Alumina Films Doped with Trace Elements

2021 ◽  
Author(s):  
Tsuneaki Matsudaira ◽  
Takafumi Ogawa ◽  
Miyuki Takeuchi ◽  
Naoya Shibata ◽  
Yuichi Ikuhara ◽  
...  
Keyword(s):  
Mass Transfer ◽  
Trace Elements ◽  
Oxygen Potential ◽  
Polycrystalline Alumina ◽  
Alumina Films ◽  
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 through a single grain boundary in alumina bicrystals under oxygen potential gradients

2010 ◽  
Vol 46 (12) ◽  
pp. 4407-4412 ◽  
Author(s):  
Tsuneaki Matsudaira ◽  
Satoshi Kitaoka ◽  
Naoya Shibata ◽  
Tsubasa Nakagawa ◽  
Yuichi Ikuhara
Keyword(s):  
Mass Transfer ◽  
Grain Boundary ◽  
Oxygen Potential ◽  
Potential Gradients ◽  
Single Grain

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

Mass Transfer in Yb Silicate Environmental Barrier Coatings at High Temperatures

2018 ◽  
Vol 941 ◽  
pp. 1898-1903
Author(s):  
Satoshi Kitaoka ◽  
Tsuneaki Matsudaira ◽  
Masashi Wada ◽  
Naoki Kawashima ◽  
Daisaku Yokoe ◽  
...  
Keyword(s):  
Mass Transfer ◽  
Oxygen Potential ◽  
Silicate Layer ◽  
Design Guideline ◽  
Barrier Coatings ◽  
Environmental Barrier Coatings ◽  
Environmental Barrier ◽  
Partial Pressures ◽  
Potential Gradients ◽  
Ytterbium Silicate

The oxygen permeabilities of polycrystalline Yb2Si2O7 wafers cut from sintered bodies to serve as models of environmental barrier coatings were determined at temperatures up to 1673 K under various oxygen potential gradients (dµO), produced by exposing the upper and lower surfaces of the wafer to atmospheres with different oxygen partial pressures (PO2). Oxygen permeation proceeded via grain boundary (GB) diffusion of oxygen from the higher PO2 surface to the lower PO2 surface, concurrently with GB diffusion of ytterbium in the opposite direction. Mass transfer analysis allowed for a design guideline for selectively enhancing the structural stability of the ytterbium silicate layer with applying a dµO.

Control of Polymorphism and Mass-Transfer in Al2O3 Scale on Alumina Forming Alloys

2010 ◽  
Vol 638-642 ◽  
pp. 888-893 ◽  
Author(s):  
Satoshi Kitaoka ◽  
Tsuneaki Matsudaira ◽  
Masashi Wada ◽  
Tomohiro Kuroyama
Keyword(s):  
Mass Transfer ◽  
Oxygen Partial Pressure ◽  
Partial Pressure ◽  
Oxygen Potential ◽  
Oxygen Permeability ◽  
Al2o3 Scale ◽  
Lower Oxygen Partial Pressure ◽  
Lower Oxygen ◽  
Potential Gradients ◽  
Conicraly Alloy

The transformation from metastable polymorphs to stable alpha-Al2O3 in the scale formed on a CoNiCrAlY alloy is accelerated under lower oxygen partial pressure (PO2), where both Al and Cr in the alloy are simultaneously oxidized, resulting in the formation of a dense and monolithic alpha-Al2O3 scale. Under higher PO2, where all components of the alloy are oxidized, the transformation is retarded and (Co,Ni)(Al,Cr)2O4 is also produced. The oxygen permeability in polycrystalline alpha-Al2O3 wafers exposed to steep oxygen potential gradients is evaluated at high temperatures to investigate the complicated mass-transfer phenomena through the scale formed on the alloy. The diffusion of Al and O species, which are responsible for the oxygen permeation along the grain boundaries of Al2O3, is dependent on the formation of an oxygen potential gradients. For Lu-doped Al2O3 polycrystals, it was found that Lu depressed the mobility of oxygen, but did not directly influence the migration of Al.

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
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