Ni self-diffusion in glass forming Pd–Ni–S melts

Abstract

The Ni self-diffusion in glass forming Pd40Ni40S20, Pd37Ni37S26 and Pd31Ni42S27 melts was probed by incoherent, quasielastic neutron scattering over a temperature range between 773 and 1023 K. The Ni self-diffusion coefficients are on a 10−10 m2 s−1–10−9 m2 s−1 scale and barely change with composition. Each composition exhibits an Arrhenius-type temperature dependence of the Ni self-diffusion coefficients, which results in activation energies ranging from E A = 348 ± 16 meV for Pd40Ni40S20 to E A = 387 ± 6 meV for Pd37Ni37S26. The structural relaxation shows a stretched exponential behavior even far above the liquidus temperatures. In addition, the viscosity of the Pd37Ni37S26 melt was measured under reduced gravity conditions. The diffusion calculated from the viscosity reveals a significant deviation from the measured Ni self-diffusion by a factor between 4 and 8. This may indicate a dynamic decoupling between the atoms within the Pd–Ni–S equilibrium melts.

Impact of sulfur addition on the structure and dynamics of Ni–Nb alloy melts

“…% has indeed been observed, whereas in the Pd-Ni-S alloy melts, where the sulfur content is considerably higher, the diffusive dynamics of Ni depends only very weakly on the sulfur concentration. 14,15 This indicates that the mechanisms of improved GFA upon sulfur addition can be different in different alloy systems.…”