Project Details
Projekt
Diffusion of H bearing species in silicate glasses at low temperatures - development of a new experimental technique
Subject Area
Mineralogy, Petrology and Geochemistry
Term
from 2017 to 2024
Project identifier
Deutsche Forschungsgemeinschaft (DFG) - Project number 342185776
The transport of H in glasses at relatively low temperatures (below 200 °C) is relevant for a number of applications such as obisidian dating of archaeological artefacts, palaeoclimate studies, storage of high level nuclear waste, production of volcanic ash, biogeochemical weathering of basalts and its implications for various geochemical cycles, engineering the mechanical properties of glasses, understanding the behaviour of glass electrodes in chemical analysis, and the understanding of some optical data storage devices.Experimental measurement of diffusion coefficients of H-bearing species has been difficult to impossible at these conditions because water, the most commonly used source of H, reacts with glass by dissolution - precipitation reactions and it is difficult to isolate the process of diffusion. Sluggish diffusion rates at low temperatures add further complications. Yet, extrapolation of diffusion coefficients measured at higher temperatures is shown to be inadequate for describing the observed shapes of concentration gradients produced by low temperature processes. We have developed several new experimental aspects, and in particular (a) the ability to produce H-bearing amorphous thin films to act as a source of H without the presence of free H2O, and (b) the ability to measure low concentrations of H, independent of the speciation, with a high spatial resolution on the nanometer scale. In this project it is intended to use these developments to explore the diffusion of H-bearing species at conditions that have been inaccessible so far. A specific goal is to characterize the compositional dependence of H-diffusion at these conditions and understand the change of diffusion mechanism that leads to a different behaviour from those observed at higher temperatures.
DFG Programme
Research Grants
Co-Investigator
Dr. Detlef Rogalla
Cooperation Partners
Dr. Christopher Beyer; Dr. Ralf Dohmen; Dr. Sara Fanara, Ph.D.; Dr. Thomas Fockenberg
