Presentation on theme: "ISU Updates Rupa Dumpala, Scott Broderick, Joaquin Peralta and Krishna Rajan."— Presentation transcript:
ISU Updates Rupa Dumpala, Scott Broderick, Joaquin Peralta and Krishna Rajan
Summary of Previous Results Atom probe experimentation -Atomic scale measurement of gas-solid reactions of Al and Oxygen - Compound formation - Study of Interfacial chemistry -Environmental chamber for in-situ gas reactions – Unique features and capabilities -Collaborations: - Maryland – Sample prepared by Maryland by reacting Si microtips; analysis of samples by ISU - Van Duin group – Use of atom probe results for experimental inputs into ReaxFF simulations
Progress Atom probe experimentation -3D interface analysis of gas solid reactions - Iso surface concentrations -Interfacial chemistry, morphology, etc. -Atomic scale measurement of gas-solid reactions of Si and oxygen -Refinements in Environmental chamber set up for in-situ gas reactions Future Steps -Gas solid reactions of near space environment condition -Surface reactions / orientation dependence of reactions
Chemistry of Gas-Solid Reactions We have analyzed gas-solid reactions of materials and the resulting bonds Oxidation of Aluminum at 450 C, 2.5 x 10- 3 Torr for 10 min. The Al-O compounds shown are from an Al 2 O 3 phase. By measuring the compounds, we get a more local chemical measurement – Al2O3 phase comprised of Al2O, Al2O2, AlO and AlO2 clusters.
Interface from Gas-Solid Reactions Measurement of two dimensional interfaces. Bulk Al 2 O 3 phase Bulk Al phase Interface shown from reaction of O and Al. Identify Al2O3 as bulk phase of gas-solid reaction, and perovskite phase at the interface. We have further developed this approach to imaging of 3D interfaces. - Interface shape - Interface uniformity Interface
Diffusion Profile 3D Interface from Gas-Solid Reactions The shape of the sample --- all collected atoms are imaged
Diffusion Profile 3D Interface from Gas-Solid Reactions Iso surface-Al (41%) Instead of imaging each atom, we are showing the surface corresponding to the concentrations measured in the diffusion profiles.
Diffusion Profile 3D Interface from Gas-Solid Reactions Iso surface-Al (80%)
Diffusion Profile 3D Interface from Gas-Solid Reactions Iso surface- O (1.93%)
Diffusion Profile 3D Interface from Gas-Solid Reactions Iso surface-Al (97%)
Image of changing interfacial isosurfaces with changing interfacial chemistry. Interface is uniform, and the shape of interface does not change significantly with chemistry. Al (41%) Al (80%) Al (97%) O (1.93%)
Future Result: Surface Reactions from Gas-Solid Reactions Results shown for O and Si reaction. Reaction sites identified and resulting compounds / bonds identified. We will expand this approach to consider orientational dependence of reactions and measure compound formations as a function of orientation – expand work beyond chemical reactions to incorporate crystallography.
APT Environmental Chamber Update Improvements made to environmental chamber: Vacuum in chamber improved two orders of magnitude to 10 -8 torr Control of gas pressure enhanced for finer measurement and representation of space conditions Increased possible gas systems that can be introduced into chamber to CO.