| AVS 60th International Symposium and Exhibition | |
| Atom Probe Tomography Focus Topic | Wednesday Sessions |
| Session AP+AS+MI+NS+SS-WeA |
| Session: | APT and FIM Analysis of Catalysts and Nanoscale Materials |
| Presenter: | S. Dumpala, Iowa State University |
| Authors: | S. Dumpala, Iowa State University S.R. Broderick, Iowa State University P.A.J. Bagot, University of Oxford, UK K. Rajan, Iowa State University |
| Correspondent: | Click to Email |
The diffusion couples of in-situ metal-oxygen reactions are analyzed through laser pulsed atom probe tomography (APT) reactions and experiments. Using ternary metal compounds, the relative diffusion and segregation of the different species with oxidation is assessed. This provides a further level of information beyond typical diffusion profiles by considering relative changes in metallic species, providing basic material descriptions at a higher resolution then ever previously measured.
The oxidation experiments were performed in-situ and at temperatures of ~450 OC and at 10-3 torr pressures. Given atom probe’s atomic scale spatial resolution, chemical diffusion over a nanometers wide range across the chemical interface is assessed with exceptional accuracy, and the identification of compound formation is quantified. By performing all reactions within an in-situ APT reaction cell along with initial (in-situ) cleaning of the samples, any effects due to native oxidation or contamination are eliminated, which is particularly important when considering atomic scale spatial resolution and femto-scale chemical resolution. The challenges associated with performing in-situ reactions and the potential of this new experimental set-up to study a far wider range of treatment conditions, particularly when coupled with a laser-pulsed APT are discussed.
3D results of binary and ternary catalytic alloys are presented and the advancements in studying catalytic reactions are discussed. Aluminum and silicon samples were also oxidized and chemically-mapped atomic scale imaging of the material were processed to identify the preferred stoichiometry of aluminum oxides as a function of the distance from the aluminum-oxygen interface. This demonstrated ability of the APT to simultaneously image and chemically quantify gas-metal interactions at the atomic level enables us to systematically quantify these interactions as a function of material chemistries, crystallographic orientations and important microstructural features.
Acknowledgments : The authors acknowledge the support from Air Force Office of Scientific Research grants: FA9550-10-1-0256, FA9550-11-1-0158 and FA9550-12-0496; NSF grants: ARI Program CMMI-09-389018 and PHY CDI-09-41576; and Defense Advanced Research Projects Agency grant N66001-10-1-4004.