In situ X-Ray Diffraction of Shock-Compressed Fused Silica.
In situ X-Ray Diffraction of Shock-Compressed Fused Silica.
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DOI：
10.1103/physrevlett.120.135702
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发表时间：
2018-03
影响因子：
8.6
通讯作者：
S. Tracy;S. Turneaure;T. Duffy
中科院分区：
文献类型：
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作者：
S. Tracy;S. Turneaure;T. Duffy
由于在材料科学和地球物理中的广泛应用，SiO_2}在冲击压缩下得到了广泛的研究。石英和熔融二氧化硅都通过所谓的“混合相区”转变为密度高、可压缩性低的高压相。几十年来，这一阶段的性质一直是争论的主题。所提出的结构包括晶态辉石、另一高压晶相或致密的非晶相。在这里，我们使用平板碰撞实验和脉冲同步X射线衍射法研究了压缩到63 Gpa的熔融二氧化硅冲击的结构。与最近的激光压缩实验相比，我们发现在34 Gpa及以下，熔融二氧化硅采用致密的非晶态结构。当压缩压力超过34 Gpa时，熔融二氧化硅转变为未织构的多晶辉石。我们的结果可以解释先前熔融二氧化硅冲击压缩行为的模糊特征，并与最近的分子动力学模拟相一致。据估计，在几百纳秒的时间尺度上，辉石的颗粒尺寸为∼5-30 nm。
Because of its widespread applications in materials science and geophysics, SiO_{2} has been extensively examined under shock compression. Both quartz and fused silica transform through a so-called "mixed-phase region" to a dense, low compressibility high-pressure phase. For decades, the nature of this phase has been a subject of debate. Proposed structures include crystalline stishovite, another high-pressure crystalline phase, or a dense amorphous phase. Here we use plate-impact experiments and pulsed synchrotron x-ray diffraction to examine the structure of fused silica shock compressed to 63 GPa. In contrast to recent laser-driven compression experiments, we find that fused silica adopts a dense amorphous structure at 34 GPa and below. When compressed above 34 GPa, fused silica transforms to untextured polycrystalline stishovite. Our results can explain previously ambiguous features of the shock-compression behavior of fused silica and are consistent with recent molecular dynamics simulations. Stishovite grain sizes are estimated to be ∼5-30 nm for compression over a few hundred nanosecond time scale.