Xenon solubility and formation of supercritical xenon precipitates in glasses under non-equilibrium conditions

Anamul H Mir,Jean-Marc Delaye,Sylvain Peuget,J A Hinks,S E Donnelly

doi:10.1038/s41598-018-33556-y

Abstract

Estimates of noble gas solubility in glasses and minerals are important to understand the origin of these gases, particularly xenon, in the atmosphere. However, technical difficulties and ambiguities in quantifying the dissolved gases introduce large uncertainties in the solubility estimates. We present here the use of transmission electron microscopy (TEM) with in-situ noble gas ion implantation as a non-equilibrium approach for noble gas solubility estimates. Using a suitable Xe equation of state and Monte-Carlo simulations of TEM images, a clear distinction between Xe filled precipitates and empty voids is made. Furthermore, implantation-induced changes in the solubility are estimated using molecular dynamics simulations. These studies allow us to evaluate the xenon solubility of irradiated and pristine silica glasses and monitor in-situ the diffusion-mediated dynamics between the precipitates and voids — otherwise impossible to capture. On exceeding the solubility limit, supercritical xenon precipitates, stable at least up to 1155 K, are formed. The results highlight the high capacity of silicates to store xenon and, predict higher solubility of radiogenic xenon due to the accompanying radiation damage.

Highlights

Studies on the solubility and diffusion of noble gases in glasses and minerals are crucial to help understand the noble gas fractionation and to trace the origin of the noble gases, Xe, in the atmosphere
This study demonstrates that a clear distinction between dense supercritical Xe precipitates and voids can be made and that the dynamics of their inter-conversion during annealing and implantation can be tracked using in-situ transmission electron microscopy (TEM)
It highlights the potential of using Monte Carlo simulations and equation of state to provide a qualitative and quantitative validation of the TEM images of the precipitates and voids

Summary

Introduction

Studies on the solubility and diffusion of noble gases in glasses and minerals are crucial to help understand the noble gas fractionation and to trace the origin of the noble gases, Xe, in the atmosphere. Precise quantification of the maximum solubility sites from gas infusion experiments is often marred by uncertainties arising from difficulties in clearly differentiating the following: surface adsorption and desorption; gas release from nano and micro bubbles; the presence of multiple phases; and actual physical and/or chemical solubility within the network of the host matrix Such uncertainties can often lead to solubility values that differ significantly between the experiments (at times by more than an order of magnitude)[3] or by up to a factor of four within a given experiment — depending on the characterisation method[1,4,5,6,7]. Using molecular dynamics (MD) simulations, the effect of irradiation damage on the Xe solubility limit is quantified and used to evaluate the solubility limit of implanted amorphous silica (a-SiO2), virgin a-SiO2 and of a complex alkali borosilicate glass

Objectives

Methods

Results

Conclusion