Abstract:
The crystallization kinetics of stoichiometric nickel sulphide (NiS) have been
investigated using non-isothermal cooling. DSC was used to characterize the
crystallization process which was observed to be complex thus excluding direct
methods of characterization. Indirect methods were therefore applied. The
temperature dependence was characterized by measurement of the onset
temperature of crystallization. As the high temperature form of NiS (u-NiS) is
quenchable, the degree of conversion for a particular cooling rate was measured
from the proportion of a-NiS stabilized at ambient temperatures. A transition in the
cooling rate dependence of the crystallization process was observed from both onset
temperature and degree of conversion measurement. The data were fitted to a nonisothermal
form of the Avrami equation which indicated that the change in
crystallization mechanism was from three dimension crystal growth to one
dimensional crystal growth. Bulk nucleation was indicated in both cases.
