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 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 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.