Corrosion chemistry of vanadium in liquid lithium containing dissolved nitrogen

The mechanism and kinetics of the reaction of nitrogen dissolved in liquid lithium with solid vanadium have been studied using a dynamic electrical resistivity technique. Equilibrium resistivity-composition data at 750 K indicate that VN is formed initially at aLi3N<0.0025 and that further reaction affords Li7VN4 at aLi3N = 0.03780: V(s)+N(Li) → VN(s) (1); VN(s)+3N(Li)+7Li(l) → Li7VN4(s) (2). The former observation is consistent with the nitrogen activity required for VN formation aLi3N = 3.4x10-7, calculated from literature free energy data for VN; the latter observation can be used to derive novel free energy data for Li7VN4. Dynamic resistivity-time data at 750 K show that the rate of reaction (1) is at least an order of magnitude greater than that of reaction (2). The kinetics of the former can be understood in terms of a heterogeneous mechanism in which the product is formed at the solid vanadium-solution interface by attack of dissolved nitrogen. (orig.)