PNNL

Abstract

Understanding the early stages of interactions between oxygen and material surfaces—especially at very high spatial resolutions—is highly beneficial for fields ranging from materials degradation, corrosion, geological sciences, forensics, and catalysis. We demonstrate the ability of in situ atom probe tomography (APT) to track the diffusion of oxygen and metal ions at nanoscale spatial resolution during the early stages of oxidation of a model Fe–Cr–Ni alloy. Using 18O isotope tracers in these in situ APT experiments and complementary ex situ transmission electron microscopy, x-ray photoelectron spectroscopy depth profiling, synchrotron based x-ray near edge spectroscopy and mesoscale model based on coupled Poisson-Nernst-Planck transport kinetics model and classical density functional theory allowed us to precisely analyze the kinetics of oxidation and determine that outward cation diffusion is the primary mechanism for intragranular oxide growth in this alloy at 300 °C. This unique in situ isotopic tracer atom probe tomography approach and the insights gained can be highly beneficial for studying gas–surface reactions in a broad array of materials.