Equation-of-state from SiO2 aerogel Hugoniot data

The significance of the new aerogel data for the equation-of-state of SiO2 is discussed. On this basis the use of SiO2 aerogels as a standard witness material for Hugoniot release wave measurements is advocated. We compare the Hugoniot data of Holmes on aerogel samples of density 0.128 gm/cm3 with a multiphase EOS for quartz developed by F. Ree some 15 years ago. His tabular EOS includes compositional changes arising from both chemical and ionization equilibrium, and is found to be in excellent agreement with the Hugoniot data and its extension to higher pressures. The roles of phase and compositional changes along the aerogel Hugoniot and the close agreement with the measured linear shock velocity relation are discussed. In this connection a useful simple Grueneisen EOS model for quartz with an energy dependent gamma is derived from the linear velocity relation and is supported by the Ree EOS