Solubility of nitrogen in tantalum

Abstract

The solubility of nitrogen in a vigorously degassed atomically clean tantalum wire was studied using ultra-high vacuum techniques. Over the pressure-temperature-concentration ranges 10^–8–10^–3torr, 1600–2300°K and 0.0044–1 atomic % respectively, ideal solution behaviour of nitrogen in tantalum is exhibited, the following expression describing the solution data, [graphic omitted] where C is in atomic %P_e is the equilibrium pressure in torr, and T the temperature in °K. The standard partial molar entropy of solution is –(15.5±3) cal deg.^–1 g atom^–1. This value is in good agreement with a theoretical entropy calculated from disorder and vibrational contributions. The model used to calculate the vibrational entropy is an isotropic three-dimensional Einstein linear oscillator.