Meera Madhavi, University of California, Davis

Abstract:

Shock experiments give a unique insight into the behavior of matter subjected to extremely high temperatures and pressures. Understanding the behavior of materials under such extreme conditions is key to modeling material failure and deformation dynamics under ballistic impact [1–3]. While studies on pure silica are extensive, the shock behavior of other commercial silicates that contain additional oxides has not been systematically investigated. To better understand the role of composition in the dynamic response of silicates, we performed laser-driven shock compression experiments on soda-lime glass (SLG) and boro-silicate glass (BSG). Using the accurate pulse shaping offered by the long pulse laser system at the Matter in Extreme Condition (MEC) end-station at the Linac Coherent Light Source (LCLS), the silicate glasses were compressed steadily along the Hugoniot upto 250 GPa. Velocity Interferometer System for Any Reflector (VISAR) was used to measure the material particle velocity and determine the pressure inside the sample. In situ X-ray diffraction was used to track the structural transformation in the silicate glasses as a function of composition and pressure. It was observed that SLG upon shock compression transformed from its ambient 4-fold coordinated amorphous structure to a 6-fold coordinated high density amorphous structure above 40 GPa. The high density amorphous structure was observed upto 100 GPa with increase in the density with pressure. While crystallization has been observed in fused silica upon shock compression [3, 4], SLG with network modifying cations Na+ and Ca²⁺ did not crystallize and remained amorphous in the pressure range measured (40-250 GPa). In contrast, BSG with the added network forming cations B³⁺ and Al³⁺ was seen to crystallize at 40 GPa similar to the shock response of fused silica [3, 5]. This structure was observed from 40 GPa to 60 GPa. Above 60 GPa, the BSG was observed to undergo an amorphous transformation to a high density amorphous structure similar to that observed in SLG. This is one of the first studies to characterize the high pressure structural changes in SLG and BSG under shock compression using in situ x-ray diffraction techniques.

Poster Session Link: https://gather.town/invite?token=0pEoq7VP

If you have any questions for the presenter, please contact them via email: fmeera@ucdavis.edu