MEASUREMENT OF PHYSICAL-PROPERTIES OF LUBRICANTS UNDER HIGH-PRESSURE BY BRILLOUIN-SCATTERING IN A DIAMOND-ANVIL CELL

Brillouin scattering spectra and their transverse mode were measured f or paraffinic and naphthenic synthetic lubricants, employing a high-pr essure diamond anvil cell (DAC). Sound velocity, density, refractive i ndex, and shear modulus under high pressure were obtained. The density obtained from the thermodynamic relation was compared with that from Lorentz-Lorenz's formula. The densities were also compared with Dowson 's density-pressure equation of lubricants. The sound velocity in the transverse mode and shear modulus were obtained for 5P4E up to 2.7 GPa . A slope change in the pressure-sound velocity diagram was confirmed at about 0.3 GPa, which may be associated with crystallizaton of 5P4E, observed through a diamond optical window in the DAC.