Shock induced phase transition of different TiO$_{2}$ precursors*

To investigate the effects of phase composition and particle size on shock-induced phase transition of TiO$_{2}$, different TiO$_{2 }$precursors including MC-150 TiO$_{2}$(pure anatase,5nm), P25 TiO$_{2}$(85{\%} anatase/15{\%} rutile,15nm), T2 TiO$_{2}$(pure anatase,35nm) and T1 TiO$_{2}$(pure rutile, 24nm) were impacted by detonation-driven high velocity flyers. Powder X-ray diffraction(XRD) was used to characterize the phase composition of recovered samples. Two types of phase transition were observed, including anatase to rutile transition and anatase to high pressure phase of srilankite transition. The phase transition mechanisms and effects of shock conditions, initial phase composition and particle size were analyzed. Complete transition from anatase to srilankite can be obtained by adjusting the shock conditions. In the case of impacting pure P25 TiO$_{2}$, anatase to srilankite transition was hardly observed, which may be due to the restraint of initial phase of thermodynamically stable rutile. However, in the case of impacting a mixture of P25 TiO$_{2}$ and dicyandiamide(C$_{2}$N$_{4}$H$_{4})$, it is interesting to observe anatase to srilankite transition and the mechanisms was analyzed.