Directional amorphization of boron carbide subjected to laser shock compression
Directional amorphization of boron carbide subjected to laser shock compression
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DOI：
10.1073/pnas.1604613113
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发表时间：
2016-10-25
影响因子：
11.1
通讯作者：
Meyers, Marc A.
中科院分区：
文献类型：
--
作者：
Zhao, Shiteng;Kad, Bimal;Meyers, Marc A.
固体激波传播在本质上是非平衡的，因此与速率有关。使用高功率脉冲激光驱动的冲击压缩，可以实现前所未有的高应变率；本文报道了碳化硼多晶的定向非晶化。在45 ~ 50 GPa的冲击压力下，在冲击面以下几百纳米处出现了与最大剪切方向略有偏离的多个平面断层。高分辨率透射电镜显示，这些平面断层是定向非晶化的前兆。有人提出，剪切应力导致非晶化和压力协助的过程中，确保试样的完整性。包括传热在内的热能转换计算表明，非晶化是一个固态过程。这种现象对B4C的弹道性能有显著影响。
Solid-state shock-wave propagation is strongly nonequilibrium in nature and hence rate dependent. Using high-power pulsed-laser-driven shock compression, unprecedented high strain rates can be achieved; here we report the directional amorphization in boron carbide polycrystals. At a shock pressure of 45 similar to 50 GPa, multiple planar faults, slightly deviated from maximum shear direction, occur a few hundred nanometers below the shock surface. High-resolution transmission electron microscopy reveals that these planar faults are precursors of directional amorphization. It is proposed that the shear stresses cause the amorphization and that pressure assists the process by ensuring the integrity of the specimen. Thermal energy conversion calculations including heat transfer suggest that amorphization is a solid-state process. Such a phenomenon has significant effect on the ballistic performance of B4C.