Reactions in the Niobium-Hydrogen System

Abstract

Equil ibria and elevated-temperature x-ray studies show that a solid solu-tion of hydrogen in niobium is produced throughout most of the system. A miscibility gap was found at low temperatures and pressures with a critical point at about 140 ~ 0.01 mm of mercury hydrogen pressure, and 0.3 H/Nb. Sorption rates at 300~176 were initially linear. At higher temperatures, sorption rates were controlled by diffusion in the metal matrix. Diffusion co-efficients at 600~176 can be expressed by: D ~ 0.0215 exp [(--9370 • 600)/RT] Desorption rates were slower than those predicted by diffusion. In a previous study (1), the authors invest igated the equi l ibr ia in the n iob ium-hydrogen system in the ranges 100~176 10-1000 mm of mercury hy-drogen pressure, and at atomic ratios of hydrogen to niobium, H/Nb, of 0.01-0.85. A s ingle-phase solid