蓝宝石冲击压缩到400 GPa（4 Mbar）时的熵主导耗散
Entropy-Dominated Dissipation in Sapphire Shock-Compressed up to 400 GPa (4 Mbar)
摘要：
蓝宝石（单晶Al 2 O3）是一种代表性的地球材料，在冲击实验中用作窗口和/或砧。例如，核幔边界的压力约为130吉帕斯卡（GPa）。由100 GPa冲击波引起的缺陷导致蓝宝石变得不透明，这妨碍了用热辐射测量温度。我们已经测量了在冲击压力为16，23，和86 GPa的蓝宝石晶体与几个结晶取向的波形。在23 GPa的塑性冲击上升时间通常是相当长的（~100纳秒），其值敏感地依赖于冲击在晶格中传播的方向。较长的上升时间可能是由有序三维蓝宝石晶格中原子间相互作用的高强度引起的。我们的波的轮廓和最近的理论和激光驱动的实验结果表明，蓝宝石的障碍没有显着的冲击加热到约400 GPa，高于此Al 2 O3是非晶的，必须加热。这幅图表明，许多地球物质在100 GPa压力下的冲击压缩曲线的特征形状是由熵和温度的组合引起的。
英文摘要：
Sapphire (single-crystal Al2O3) is a representative Earth material and is used as a window and/or anvil in shock experiments. Pressure, for example, at the core-mantle boundary is about 130 gigapascals (GPa). Defects induced by 100-GPa shock waves cause sapphire to become opaque, which precludes measuring temperature with thermal radiance. We have measured wave profiles of sapphire crystals with several crystallographic orientations at shock pressures of 16, 23, and 86 GPa. At 23 GPa plastic-shock rise times are generally quite long (~100 ns) and their values depend sensitively on the direction of shock propagation in the crystal lattice. The long rise times are probably caused by the high strength of inter-atomic interactions in the ordered three-dimensional sapphire lattice. Our wave profiles and recent theoretical and laser-driven experimental results imply that sapphire disorders without significant shock heating up to about 400 GPa, above which Al2O3 is amorphous and must heat. This picture suggests that the characteristic shape of shock compression curves of many Earth materials at 100 GPa pressures is caused by a combination of entropy and temperature.
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