Authors:D. Bishop, P. Thomas, A. Ray, and P. Šimon
Toughened glass panels used as a glazing material in multistorey buildings are known to fracture prematurely when they contain
nickel sulfide inclusions as a result of the α-β phase recrystallisation in nickel sulfide. The kinetics of this recrystallisation
were studied by differential scanning calorimetry (DSC) under isothermal and non-isothermal conditions. The recrystallisation
was observed to be a two-step process with an induction period followed by the phase change. A two-stage kinetic model was
used to estimate the recrystallisation time under ambient conditions. These values were found to correlate well with the observed
time to failure for glass panels installed in multistorey buildings.
Nickel sulphide (NiS) was characterised using X-ray diffraction, thermal gravimetric analysis (TG) and differential scanning
calorimetry (DSC). The 'as received' Millerite, stoichiometric NiS, observed to be slightly nickel deficient, was found to
readily decompose in a nitrogen atmosphere at elevated temperatures (450C max.) to the sulphur deficient Godlevskite, Ni7S6. DSC and X-ray measurements demonstrated that the high temperature form of the Godlevskite was readily stabilised at room
temperature. The kinetics of the α-β re-transformation in Godlevskite were then investigated using DSC and were observed to
be first order.