Nickel Sulphide Inclusions In Glass: An Example Of Microcracking Induced By A Volumetric Expanding Phase Change

Microcracking about inclusions of nickel sulphide in soda-lime glass has been studied. These cracks are nucleated by the volumetric expansion that accompanies the alpha-beta phase transformation in nickel sulphide. The a-phase is metastable and, upon transofrmation to the b-phase, is accompanied by a volumetric expansion of about 4%. The critical dimensions of the inclusion to initiate microcracking in an annealed specimen and to cause spontaneous fracture of a tempered plate are predicted.