Nitrogen Diffusion in Zirconium Nitride

Abstract

Diffusion of nitrogen in ZnNo.93 plates obtained by direct nitridation of 99.995 weight per cent zirconium sheets at 1150~ was studied using the ~SN gas-solid exchange technique. These specimens were characterized by chemical analyses, density, lattice parameter, and structural measurements. The diffusion anneals were performed at a nitrogen pressure of 220 Torr and at temperatures in the range 1000~176The tracer diffusion coefficient can be expressed as D* (cm2/sec) ----4.08 • 10 -6 exp --36,600/RT. These results when compared to determinations of the chemical diffusion coefficients obtained from Zr nitriding kinetics demonstrate that nitrogen transport in the polycrystalline solid at temperatures less than 1200~ is associated with a short-circuit diffusion mechanism.Diffusion studies on metal ni~rides have been a subject of limited interest. Indeed, diffusion coefficients have been reported for only a few transition metal nitrides which are chemical coefficients for nitrogen diffusion except for uranium mononitride where tracer diffusion coefficients are available for both nitrogen and the metal species. The purpose of this investigation, accordingly, was to determine the nitrogen tracer diffusion coefficient in zirconium mononitride and to compare this determination to diffusivities obtained from models for the nitridation of zirconium (1-6) and the sintering of this nonstoichiometric compound (7).

Radiation Damage and Fission Product Release in Zirconium Nitride

“…The diffusion coefficient for nitrogen is about 100 times greater than that of zirconium [144,145]. This will have an effect during both processing and the cool-down period.…”

“…The self-diffusion of the nitrogen has been observed to be 100 times faster than that of the zirconium, and zirconium diffusion is considered negligible [144,145]. The nitrogen sublattice can accommodate 15% loss of nitrogen before complete loss of cubic structure.…”