posted on 2024-03-13, 12:38authored bySang T. Pham, Anh Kiet Tieu, Chao Sun, Shanhong Wan, Sean M. Collins
Systematic control
and design of solid-state chemical reactions
are required for modifying materials properties and in novel synthesis.
Understanding chemical dynamics at the nanoscale is therefore essential
to revealing the key reactive pathways. Herein, we combine focused
ion beam–scanning electron microscopy (FIB-SEM) and time-of-flight
secondary ion mass spectrometry (TOF-SIMS) to track the migration
of sodium from a borate coating to the oxide scale during in situ hot corrosion testing. We map the changing distribution
of chemical elements and compounds from 50 to 850 °C to reveal
how sodium diffusion induces corrosion. The results are validated
by in situ X-ray diffraction and post-mortem TOF-SIMS.
We additionally retrieve the through-solid sodium diffusion rate by
fitting measurements to a Fickian diffusion model. This study presents
a step change in analyzing microscopic diffusion mechanics with high
chemical sensitivity and selectivity, a widespread analytical challenge
that underpins the defining rates and mechanisms of solid-state reactions.