Ag-Cd-Sn合金の内部酸化の速度論

Abstract

Ag-Cd-Sn alloy wires containing 9.9∼17 mass%Cd and 0.5∼1.5 mass%Sn were oxidized at 873 to 1023 K under an oxygen pressure of 2.1×104 Pa (in air). The depth of the internally oxidized layer, ξ, and an amount of Cd diffused into the oxidized layer from the unoxidized region, JCd, were measured in order to investigate the behavior of solute elements and oxygen during internal oxidation.The results obtained are as follows:(1) The relationship between the depth of the internally oxidized layer and the oxidation time was expressed by the following equation:(This article is not displayable. Please see full text pdf.) \ oindentwhere R and r are radii of the wire and the unoxidized region after oxidation for t, respectively.(2) k was increased by addition of Sn of NSn0=0.4×10−2 and decreased with increasing content of Sn of NSn0≥0.4×10−2 at over 973 K. But k was increased by adding Sn of 0.4×10−2≤NSn0≤1.4×10−2 at the total content of solute elements that an amount of oxygen required to oxidize are the same. k was decreased by addition of Sn of every content at 873 K.(3) Counter diffusion of Cd was promoted by adding Sn of NSn0>0.4×10−2. Sn of NSn0≤0.4×10−2 did not affect the diffusion of Cd.(4) Sn changed the shape of oxides into needle-like ones and increased the interface between the Ag matrix and oxide phases along the oxidation direction.Acceleration of the growth rate of the oxidized layer can be considered to be due to the accelerated diffusion of oxygen brought about by increasing the interface diffusion.