The Mechanism of the Niobium Reaction with Water Vapor and with Oxygen

Abstract

The low‐temperature oxidation of niobium in water vapor and in oxygen occurs by diffusion of oxygen into the metal and formation of and on the surface. forms a porous scale on , growing linearly from the oxide‐oxide interface. Solution of oxygen in the metal and the growth of on niobium are believed to be diffusion controlled. The so‐called breakaway oxidation occurring between 400° and 500°C in oxygen and between 750° and 950°C in water vapor is shown to be caused by nucleation and growth of on .