In situ observation of a phase transition in silicon carbide under shock compression using pulsed X-ray diffraction, Physical Review
In situ observation of a phase transition in silicon carbide under shock compression using pulsed X-ray diffraction, Physical Review
复制标题
使用脉冲 X 射线衍射原位观察冲击压缩下碳化硅的相变，《物理评论》
DOI：
10.1103/physrevb.99.214106
复制
发表时间：
2019
期刊：
影响因子：
--
通讯作者：
Tracy, S. J.
中科院分区：
文献类型：
--
作者：
Tracy, S. J.
碳化硅（SiC）在冲击压缩下的行为由于其作为高强度陶瓷的应用和对冲击诱导多态性的一般理解而引起了人们的兴趣。本文利用直线相干光源的物质在极端条件下的光束线，对高达206gpa的SiC激光冲击进行了一系列时间分辨泵浦探针x射线衍射测量。对不同多型的单晶和多晶进行的实验表明，该材料由低压四面体相转变为高压岩盐型（B1）结构。我们直接观察到混合相区低压相和高压相共存，并在200 GPa以上完全转变为B1相。x射线衍射测量的密度与连续气枪研究和从静态压缩数据得出的理论B1 Hugoniot一致。在冲击加载和释放过程中的时间分辨测量显示，卸载时存在较大的滞后，B1相保持低至5 GPa。样品最终在后期恢复为低压相的多型混合物。我们的研究表明，x射线衍射是表征在兆巴压力下发生冲击相变的材料随时间变化的结构响应的有效手段。
The behavior of silicon carbide (SiC) under shock compression is of interest due to its applications as a high-strength ceramic and for general understanding of shock-induced polymorphism. Here we use the Matter in Extreme Conditions beamline of the Linac Coherent Light Source to carry out a series of time-resolved pump-probe x-ray diffraction measurements on SiC laser-shocked to as high as 206 GPa. Experiments on single crystals and polycrystals of different polytypes show a transformation from a low-pressure tetrahedral phase to the high-pressure rocksalt-type (B1) structure. We directly observe coexistence of the low- and high-pressure phases in a mixed-phase region and complete transformation to the B1 phase above 200 GPa. The densities measured by x-ray diffraction are in agreement with both continuum gas-gun studies and a theoretical B1 Hugoniot derived from static-compression data. Time-resolved measurements during shock loading and release reveal a large hysteresis upon unloading, with the B1 phase retained to as low as 5 GPa. The sample eventually reverts to a mixture of polytypes of the low-pressure phase at late times. Our study demonstrates that x-ray diffraction is an effective means to characterize the time-dependent structural response of materials undergoing shock-induced phase transformations at megabar pressures.