| The thermal stability of nanocrystalline materials has been studied extensively in recent years for a wide spectrum of materials. Specifically, electrodeposited nanocrystalline nickels has shown dramatic sensitivity in its growth behaviour to sulphur impurity concentrations in the range of hundred parts per million. In the current study, a novel approach to eleetrodeposition utilizing strong mechanical agitation and unusually high pulse deposition current densities was developed to produce nanocrystalline nickel with low sulphur content from an additive-free electrolyte. Inductively coupled plasma analysis showed that the sulphur impurity content was less than 10 ppm. Isothermal heat treatments of this material at three annealing temperatures of 285°C, 350°C and 450°C showed no strong evidence of abnormal grain growth, a growth form observed in many past studies on sulphur-containing nanocrystalline nickel. The microstructure evolution was classified via the introduction of log-time distribution histograms, and cumulative volume fraction diagrams. The activation energy and kinetics for grain growth was determined. |
