Shock-induced Amorphization in Covalently Bonded Solids

Abstract

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.

Switchable Phase Transition from Crystalline to Amorphous States of Cadmium Sulfate Octahydrate Single Crystals by Shock Waves

“…[1][2][3][4][5] In recent years, there have been several research articles published in this area especially in phase transitions such as crystalline to crystalline and crystalline to amorphous and amorphous to crystalline. [6][7][8][9] As far as it is known from the literature, attainment of the reversible phase transition behavior is comprehensively a critical task when compared to the irreversible transition influenced by shock waves. [10][11][12][13] Moreover, it could be noted that so far several research articles have been published based on the shock-wave-induced phase transitions whereas the reversible phase transition of materials enforced by shock waves is not yet well understood.…”