Ni-Cu合金およびNi-Co合金中の水素の拡散係数

Abstract

The diffusion of hydrogen in nickel and copper, and in fcc nickel-copper and nickel-cobalt alloys has been investigated within the wide temperature range from 260 K to 1000 K by a technique of electrochemical permeation and a technique of gas phase permeation. The temperature dependence of the diffusion coefficient of hydrogen (D) in Ni and Cu is described as follows: In Ni, D (m2/s)=9.2×10−7exp(−41.4 (kJ/mol)/RT), and in Cu, D (m2/s)=9.2×10−7 exp(−43.5 (kJ/mol)/RT). Plots of the experimentaly observed logD versus 1/T in Ni-Cu and Ni-Co alloys can be represented by straight lines. The activation energy for diffusion of hydrogen changes with the concentration of alloying element. It has a maximum at 70 at%Cu in Ni-Cu alloys, and increases with increasing concentration of Co in Ni-Co alloys.The solubility of hydrogen (S) in Ni, Cu, Ni-Cu alloys and Ni-Co alloys has been measured by a gas phase permeation method at temperatures between 560 K and 1000 K. The temperature dependence of S in Ni and Cu is given by S (mol H2/(mol Ni·Pa1⁄2))=2.2×10−6exp(−10.8 (kJ/mol)/RT) in nickel and S (mol H2/(mol Cu·Pa1⁄2))=1.4×10−5exp(−37.6 (kJ/mol)/RT) in copper. Arrhenius plots of S in Ni-Cu and Ni-Co alloys can be represented by straight lines. The solution enthalpy of hydrogen has a minimum at 30 at%Cu in Ni-Cu alloys, and increases with increasing concentration of Co in Ni-Co alloys.