Shock induced polymorphism phase transitions in high density glass

Abstract

Plate impact experiments are conducted on high density glass (HDG) with an initial density of ～4.817g/cm3 (Brand ZF6) at a two-stage light gas gun facility. A copper flyer plate is used as a standard sample. Experimental shock pressure is between 52.1GPa and 167.8GPa. A multi-wavelength pyrometer and optical analyzer technique are used to determine the Hugoniot curve, sound velocity and shock temperature of HDG. The experiment results reveal that polymorphism phase transitions occur in HDG under compression, and the onset pressures are ～23, ～78 and ～120GPa, respectively. The measured sound velocity first increases and arrives at about 78GPa, then decreases rapidly, and increases again with pressure increasing. Beyond ～120 GPa, the longitudinal sound velocity turns in to bulk sound velocity, indicating the melting of HDG. Measured shock temperatures also show discontinuities at ～78 and ～120GPa, after which its increase rate becomes small and consistent with the calculated Lindemann melting line, confirming the above HDG phase transformation behaviors. Our Hugoniot data are consistent well with LASL shock Hugoniot data of HDG, which shows discontinuity only at about 23GPa, indicating that the phase transitions at 78 and 120GPa are not first-order ones. Our shock data and the gained knowledge of dynamic response behavior of HDG are valuable for improving the accuracies in sound velocity measurements for metals and non-metals at pressures over a megabar range.