SIMULTANEOUS DETERMINATION OF INERT-GAS SOLUBILITY AND DIFFUSIVITY IN GLASSES AT ELEVATED-TEMPERATURES AND PRESSURES

Use of microanalytical techniques and simple experimental methods allows simultaneous determination of gas solubility and diffusivity in glass samples synthesized over a wide range of pressure and temperatures (to ∼ 1500 ° C and 10 kbar). The basic approach is to expose glass rods or prisms to a gas (e.g. Ar) in a metal autoclave; the gas of interest is used as the pressure medium and the autoclave is heated to high temperatures by an external furnace. After sufficient time has passed for the gas to diffuse from 50 to several hundred micrometers in to the glass sample, the sample is quenched. The sample is sectioned perpendicular to the outer surfaces exposed to the gas pressure medium and the gas diffusion profile is measured using the electron microprobe or other microanalytical technique. Use of the appropriate diffusion equation allows calculation of the gas diffusivity and the gas concentration at the sample surface, which equals the gas solubility at the pressure and temperature of the experiment. © 1990.