Gleason A E, Bolme C A, Lee H J, Nagler B, Galtier E, Milathianaki D, Hawreliak J, Kraus R G, Eggert J H, Fratanduono D E, Collins G W, Sandberg R, Yang W, Mao W L
Shock and Detonation Physics, Los Alamos National Laboratory, PO Box 1663, Los Alamos, New Mexico 87545, USA.
Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, California 94025, USA.
Nat Commun. 2015 Sep 4;6:8191. doi: 10.1038/ncomms9191.
Pressure- and temperature-induced phase transitions have been studied for more than a century but very little is known about the non-equilibrium processes by which the atoms rearrange. Shock compression generates a nearly instantaneous propagating high-pressure/temperature condition while in situ X-ray diffraction (XRD) probes the time-dependent atomic arrangement. Here we present in situ pump-probe XRD measurements on shock-compressed fused silica, revealing an amorphous to crystalline high-pressure stishovite phase transition. Using the size broadening of the diffraction peaks, the growth of nanocrystalline stishovite grains is resolved on the nanosecond timescale just after shock compression. At applied pressures above 18 GPa the nuclueation of stishovite appears to be kinetically limited to 1.4±0.4 ns. The functional form of this grain growth suggests homogeneous nucleation and attachment as the growth mechanism. These are the first observations of crystalline grain growth in the shock front between low- and high-pressure states via XRD.
压力和温度诱导的相变已经被研究了一个多世纪，但对于原子重新排列的非平衡过程却知之甚少。冲击压缩产生近乎瞬间传播的高压/高温条件，而原位X射线衍射（XRD）则探测随时间变化的原子排列。在此，我们展示了对冲击压缩熔融石英的原位泵浦-探测XRD测量，揭示了从非晶态到结晶态的高压斯石英相变。利用衍射峰的尺寸展宽，在冲击压缩后仅纳秒时间尺度上就解析出了纳米晶斯石英颗粒的生长。在施加压力高于18 GPa时，斯石英的成核似乎在动力学上限制在1.4±0.4 ns。这种晶粒生长的函数形式表明，均匀成核和附着是生长机制。这些是通过XRD首次观察到的在高低压状态之间的冲击前沿的晶粒生长。
