一种高密度玻璃的多形性高压相变和物态方程研究

在二级轻气炮上用无氧铜飞片直接撞击重玻璃平板样品(密度为4.817 g/cm³,材料牌号:ZF6)开展了冲击压缩实验研究,压力范围为52.1—167.8 GPa,并采用多通道瞬态辐射高温计和光分析技术测量了其雨贡纽线、高压声速和冲击波温度等动态特性.实验结果显示,上述性质在三个不同压力区间出现不连续性变化,表明冲击压缩下该样品材料存在多形性高压相变,相变起始压力分别为23,78和120 GPa.实测声速先是随冲击压力的增高而增加,并在78 GPa附近出现急剧下降,之后又随压力增长,并在120 GPa之后下降到体波声速,表明材料进入高压熔化相.温度数据同样在78和120 GPa处出现明显的不连续变化,并在120 GPa之后变化趋于平缓与计算的Lindeman熔化线相符,进一步印证了上述相变行为.实测雨贡纽数据与LASL数据库中的重玻璃数据相符,结果显示除23 GPa附近有一明显的突变外,高压区数据几近线性变化,表明重玻璃的两个高压相变均为二级相变.本文报道的重玻璃材料高压物性数据和序列相变认识对于发展反向加载技术、提高材料声速测量精度和适用压力范围具有实用价值. 关键词： 重玻璃 冲击温度 卸载声速 冲击相变

Shock induced polymorphism phase transitions in high density glass

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.