Engineering topics

Hicks, D. G.

Publications and source records attributed to Hicks, D. G..

2 records

DOE OSTI2024

Evidence for dissociation in shock-compressed methane

Theory and experiments show that with increasing pressure, the chemical bonds of methane rearrange, leading to the formation of complex polymers and then to dissociation. However, there is disagreement on the exact conditions where these changes take place. In this study, methane samples were precompressed in diamond-anvil cells and then shock compressed to pressures reaching 400 GPa, the highest pressures yet explored in methane. Furthermore, the results reveal a qualitative change in the Hugoniot curve at 80-150 GPa, which is interpreted as a signature of dissociation based on thermodynamic calculations and theoretical predictions.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗

DOE OSTI2021

Melting of magnesium oxide up to two terapascals using double-shock compression

Constraining the melting behavior of magnesium oxide, a major constituent of gaseous and rocky planets, is key to benchmarking their evolutionary models. Using a double-shock technique, we extended the MgO melt curve measurements to 2 TPa; this is twice the pressure achieved by previous melting experiments on any material. A temperature plateau is observed between 1218 and 1950 GPa in the second shock states, which is attributed to latent heat of melting. At 1950 GPa, the measured melting temperature is 17,600 K, 17% lower than recent theoretical predictions. Furthermore, the melting curve is steeper than that of MgSiO 3 , indicating that MgO is likely solid in the interior of Saturn-sized gas giants and extra-solar super-Earth planets.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗