Monitoring the acoustic response of nanoporous materials upon gas adsorption

Diagnostics on acoustic methods are routinely used in materials science but they are often assumed to be unsuited to probe nanoscale phenomena due to their large wavelength (λ= 10-4 - 10-2 m). Yet, the adsorption/permeation footprint in nanoporous solids is all included – albeit in an average way – in the acoustic signal emitted by the system subjected to pressure gradients or its response to acoustic wave stimulation. Our goal is to provide a multi-scale description of the acoustic response of a nanoporous material, enabling to fully understand the response usually monitored at the macroscopic scale. Molecular dynamics simulations show a coupling between the vibrational features of the nanoporous zeolite (silicalite-1) matrix and those of the CO2 adsorbed inside, that would be responsible for the averaged acoustic response. In order to probe these vibrational features over the q-range of dispersion, we request 4 days of of beamtime on MARI spectrometer.