The main raw material of Smart Glass is tempered glass. Reasons for uncontrolled explosion of tempered glass-Nickel sulfide (NiS) and heterogeneous phase particles The source of uncontrolled explosion of tempered glass is not only NiS particles in traditional understanding, but also many other heterogeneous phase particles. The crack initiation and propagation in the glass is mainly due to the residual stress generated near the particles.

This type of stress can be divided into two categories, one is the phase change stress during the phase expansion and the other is the residual stress caused by the mismatch of the thermal expansion coefficients. Nickel sulfide (NiS) and heterogeneous particles. The glass contains nickel sulfide impurities and exists in the state of small crystals. Under normal circumstances, it will not cause glass damage. However, the reheated tempered glass of Smart Glass changes the phase state of nickel sulfide impurities. The high temperature alpha state of nickel sulfide is The glass is frozen when it is quenched, and it takes time for them to return to the beta state. Due to the low temperature beta state nickel sulfide impurities, the volume will increase, and local stress concentration will occur inside the glass. At this time, the tempered glass will explode. However, only relatively large impurities will cause self-detonation, and the self-detonation of tempered glass can only occur when the impurities are at the core of the tensile stress. It can be seen from the scanning electron micrograph of the NiS stones extracted from the fragments of the Smart Glass glass after self-detonation that the surface is undulating and very rough. The heterogeneous particles cause the tempered glass to explode. It can be seen in the cross-sectional photos of the glass fragments at the source of the fracture.