Tempered glass contains nickel sulfide crystals

Nickel sulfide inclusions generally exist as crystalline small spheres with a diameter of 0.1-2 mm. The appearance is metallic, and these impurities are Ni3S2, Ni7S6, and Ni-XS, with X=0-0. 07. Only Ni1-XS phase is the main cause of spontaneous fragmentation of tempered glass.
The theoretical NIS is known to be at 379. There is a phase transition process at C, starting from the high-temperature state α- Transition of NiS hexagonal crystal system to low-temperature state β- During the process of NiS cubic crystal system, a volume expansion of 2.38% occurs. This structure is preserved at room temperature. If the glass is heated in the future, it may quickly appear α-β State transition. If these debris are inside the tempered glass under tensile stress, volume expansion will cause spontaneous cracking. If there is a-NIS at room temperature, it will gradually transition to β During this phase transition, a slow increase in volume may not necessarily cause internal rupture.