Shock-induced Amorphization in Covalently Bonded Solids
University of California,
La Jolla, CA
2 Oxford University, Oxford, OX1 2JD, UK
3 Nevada National Security Site, Livermore, CA 94550, USA
4 Oak Ridge National Laboratory, Oak Ridge, TN 21005, USA
5 Lawrence Livermore National Laboratory, Livermore, CA 94550, USA
6 U.S. Army Research Laboratory, MD 21005, USA
* Corresponding author: firstname.lastname@example.org
Published online: 7 September 2018
Deposition of powerful pulsed laser energy onto a material, ablates its surface and drives a compressive shock wave propagating through it. Using this technique, unprecedented states of matter with extremely high pressures, temperatures, and strain rates can be experimentally studied. Here we report on laser-shock induced amorphization in four covalently bonded solids, namely silicon (Si), germanium (Ge), boron carbide (B4C) and silicon carbide (SiC). Post shock transmission electron microscopy reveals that the newly formed amorphous materials exhibit a shear band alike morphology, suggesting that shear stress play a dominant role in this process. The density of these amorphous band decreases as a function of the distance to the surface and eventually disappeared at certain depth, which is coincident with the decay of the shock wave and indicates that there might be a critical stress for the onset of amorphization. Synchrotron XRay tomography of a recovered silicon target shows that large amounts of cracks are formed within the materials and the density also decrease with depth. Unlike amorphous bands, these cracks can propagate through the target, albeit without shattering the entire material. It is proposed that shock-induced amorphization is a new deformation mechanism of matter under extremely high rate deformation.
© The Authors, published by EDP Sciences, 2018
This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.