Presentation on theme: "ISU Updates Rupa Dumpala, Scott Broderick, Joaquin Peralta and Krishna Rajan."— Presentation transcript:
1ISU UpdatesRupa Dumpala, Scott Broderick, Joaquin Peralta and Krishna Rajan
2Summary of Previous Results Atom probe experimentationAtomic scale measurement of gas-solid reactions of Al and OxygenCompound formationStudy of Interfacial chemistryEnvironmental chamber for in-situ gas reactions – Unique features and capabilitiesCollaborations:Maryland – Sample prepared by Maryland by reacting Si microtips; analysis of samples by ISUVan Duin group – Use of atom probe results for experimental inputs into ReaxFF simulations
3Progress 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 oxygenRefinements in Environmental chamber set up for in-situ gas reactionsFuture StepsGas solid reactions of near space environment conditionSurface reactions / orientation dependence of reactions
4Chemistry of Gas-Solid Reactions We have analyzed gas-solid reactions of materials and the resulting bondsThe Al-O compounds shown are from an Al2O3 phase. By measuring the compounds, we get a more local chemical measurement – Al2O3 phase comprised of Al2O, Al2O2, AlO and AlO2 clusters.Oxidation of Aluminum at 450 C, 2.5 x 10-3 Torr for 10 min.
5Interface from Gas-Solid Reactions Measurement of two dimensional interfaces.Bulk Al2O3 phaseBulk Al phaseInterfaceInterface 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
63D Interface from Gas-Solid Reactions The shape of the sample --- all collected atoms are imagedDiffusion Profile
73D 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
83D Interface from Gas-Solid Reactions Iso surface-Al (80%)Diffusion Profile
93D Interface from Gas-Solid Reactions Iso surface- O (1.93%)Diffusion Profile
103D Interface from Gas-Solid Reactions Iso surface-Al (97%)Diffusion Profile
11O (1.93%)Al (80%)Al (41%)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.
12Future 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.
13APT Environmental Chamber Update Improvements made to environmental chamber:Vacuum in chamber improved two orders of magnitude to 10-8 torrControl of gas pressure enhanced for finer measurement and representation of space conditionsIncreased possible gas systems that can be introduced into chamber to CO.