Study of low-hydrostatic pressure dependent elasticity of porous alumina saturated with various gas media

Abstract

Poroelasticity describes how the elasticity of porous materials depend on the material properties: porosity, pore saturation medium and its pressure, nature of pore arrangement, and the skeleton material. The primary goal of this study is to investigate the low-hydrostatic pressure dependent elastic properties of porous alumina saturated with different gas media using resonant ultrasound spectroscopy (RUS). RUS is a precise experimental approach for investigating the elastic properties of solid materials which is capable of measurements at different temperatures and hydrostatic pressures. In RUS, the elastic stiffness tensor of crystalline and polycrystalline solids is determined from the vibrational resonance spectra. In this study, we have used commercially available porous alumina ceramic material which has ~40% of porosity and 2 μm of pore diameter. Here we are reporting the variation of elasticity and acoustic attenuation of porous alumina during the low-hydrostatic pressure cycles from 760 torr (1 atm) to 0.1 torr. An experimentally observed discontinuity of elastic stiffness and acoustic attenuation during the pressure region ~150 torr to 0.1 torr will be described by the transition from viscous to molecular flows, quantified by Knudsen number. The effects of saturated gas medium to the elasticity will also be discussed based on the RUS measurements taken during the air, He, and Ar gas saturation.