Van Tuyl Lecture, April 15, 2024, Berthoud 204, 12-1pm

Kevin Rosso, Pacific Northwest National Laboratory

Probing Ion Relaxation Dynamics at Mineral-Water Interfaces for Advances in Understanding Electrical Geophysical Signatures of the Subsurface

Abstract: Electrical geophysical sensing techniques such as resistivity tomography and spectral induced polarization hold promise for real-time monitoring of distributions of strain, porosity, permeability, and chemical phenomena in the subsurface.  But measured signals such as the complex conductivity depend in part on knowledge about relaxation timescales of polarized electrical double layer ion distributions at mineral-water interfaces. Current models of electrokinetic phenomena are not sufficiently robust to accurately predict collective ion dynamics at structurally and chemically specific mineral-water interfaces. This talk will focus on advances in experimental and computational characterization of these properties from molecular-to-microscales. In particular, I will show how electrostatic force microscopy (EFM) can be used to investigate the dynamics of ion relaxation in thin water films at various hydrated mineral surfaces under controlled relative humidity. Polarization kinetics are tracked by monitoring the tip-sample force gradient during application of a field at the tip, and subsequent EFM imaging is used to characterize the spatial relaxation dynamics after the field is released. Electrostatic finite element modeling of the sample/probe system enables multiscale connectivity from ion diffusivities to the observed stretched exponential charging response at the microscale. Complementary molecular dynamics simulations provide a predictive basis for mobile ion drift mobilities at specific mineral-water interfaces.  Building on these approaches may ultimately enable bottom-up predictions of parameters essential for accurate geophysical signal interpretation.

This lecture is scheduled in a hybrid format. If you would like to join the meeting please:

Join from PC, Mac, Linux, iOS or Android: https://mines.zoom.us/j/91807556890?pwd=K2ZBN01hRlJQMXFQK2FuNE40eWJ6UT09
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Food/ Refreshments will be served.