Stishovite nucleation at low shock pressures in soda-lime glass

Highly dense and ultra-hard Stishovite phase is the most stable form of SiO2. It is formed when fused silica is subjected to extreme pressures (>34 GPa). In this communication, we report nucleation of the Stishovite phase in shock-loaded soda-lime glass (SLG) samples at a remarkably low compressive stress of 7 GPa. Although it falls within the reported Hugoniot Elastic Limit of SLG between 2.5 and 7 GPa, it is significantly below the crystallization threshold of 34 GPa observed for fused silica. SLG plates were shock loaded by impacting them at 1-2.5 km/s using a table-top experimental setup in which 1 mm-dia Al micro flyer plates of 25-50 mu m thickness were generated and propelled using a top-hat Nd:YAG laser pulse of 8 ns duration. The shocked samples were imaged using High Resolution Transmission Electron Microscopy (HRTEM) and further analyzed using Selected Area Electron Diffraction and FFT analyses. All samples showed nucleation of 4 nm Stishovite crystals distributed within the amorphous SLG matrix. The stress state was determined by directly measuring the flyer speed, particle velocity, and shockwave speed by using a state-of-the-art Photonic Doppler Velocimeter (PDV). (C) 2021 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.