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Nakahara, Kaito*; Kawada, Rio*; Irisawa, Eriko; Ueda, Mitsutoshi*; Kawamura, Kenichi*
no journal, ,
In order to develop oxygen sensor using oxide scales formed on the surface of zirconium alloy, we focused on zirconium and copper alloy system. It was expected that the oxide scale of Zr oxide on the alloy is thin and elaborate compared with that on the pure Zr because the activity of Zr in the alloy is reduced and the oxidation rate of alloy become slow. Therefore the oxidation behavior and mechanism of two phase alloy, Zr-35Cu which is composed of Zr
Cu and Zr
Cu
, was studied. The results showed the oxidation rate of the alloy was same with that of the pure Zr.
Hayashi, Yusaku*; Ueda, Mitsutoshi*; Kawamura, Kenichi*; Irisawa, Eriko; Komatsu, Atsushi; Kato, Chiaki; Okubo, Nariaki
no journal, ,
It is necessary to form a protective oxide film on the surface in order to protect stainless steel from corrosion by liquid LBE at high temperatures. A resistance change type sensor using the reduction/oxidation phenomenon of metal oxides was devised for the oxygen concentration in liquid LBE decreases and the protective oxide film disappears from the stainless steel surface. In this paper, the principle of operation of the sensor was experimentally confirmed and its response was evaluated.
Ohigashi, Jun*; Ueda, Mitsutoshi*; Kawamura, Kenichi*; Irisawa, Eriko; Komatsu, Atsushi; Kato, Chiaki
no journal, ,
In order to develop an oxygen sensor using high temperature oxide film of zirconium alloy as a solid electrolyte, an alloy of zirconium with nickel was investigated to suppress the growth rate of zirconia oxide film on the alloy. In this study, the high temperature oxidation behavior of zirconium-nickel alloy was evaluated. The alloy was oxidized at 873 K in a mixture of argon and 1% oxygen. The relationship between the difference in oxidation rate and in the properties of the oxide film were compared and discussed with the cross-sectional images of the oxide film. The oxidation rate was the same or slightly higher than that of pure zirconium. In addition, the oxide film became thicker and voids were formed in some areas, and some cracks were also observed. The results did not show any tendency to reduce the activity of zirconium in the alloy and to decrease the oxidation rate.
Irisawa, Eriko; Utami, L.*; Kato, Chiaki; Ueda, Mitsutoshi*
no journal, ,
Ohigashi, Jun*; Ueda, Mitsutoshi*; Kawamura, Kenichi*; Irisawa, Eriko; Komatsu, Atsushi; Kato, Chiaki
no journal, ,
As a development of oxygen sensors using high-temperature oxide layer of zirconium alloys as solid electrolytes, an alloy of zirconium with nickel was investigated to control the growth rate of zirconia oxide layer on the alloy. In this study, the oxidation behavior of zirconium-nickel alloys at high-temperatures was evaluated. As a result, it was found that when the oxygen potential in the gas atmosphere was decreased, the oxidation rate increased significantly, completely different from the case of pure zirconium. In the case of zirconium-nickel alloys, it was considered that this is because the electronic conduction in the oxide film is large due to the presence of metallic Ni in the oxide film, and oxygen ion conduction is the rate-limiting factor even in an atmosphere with a low oxygen partial pressure.
Ohigashi, Jun*; Kawamura, Kenichi*; Ueda, Mitsutoshi*; Irisawa, Eriko; Komatsu, Atsushi
no journal, ,
In order to apply zirconium alloys and their oxide films to oxygen sensors, high temperature oxidation experiments were conducted on Zr-63 at.%Al, Zr-39 at.%Al, and Zr-31 at.%Y alloys. The oxidation behavior of these alloys was observed, and the oxide ion conductivity was examined by measuring the electromotive force of the oxide films of the alloys whose oxidation inhibition was confirmed. Zr-39 at.% Al and Zr-31 at.% Y alloys. On the other hand, a thin, uniform, dense zirconium oxide film was formed for the Zr-63 at.%Al alloy. The electromotive force (EMF) of this oxide film was measured in a gas of known oxygen concentration, but it was smaller than the expected EMF, and the oxide ion conductivity was not sufficient.