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Summary of Previous Results

Summary of Previous Results. Atom probe experimentation Atomic scale measurement of gas-solid reactions of Al and Oxygen Compound formation Study of Interfacial chemistry -3D interface analysis of gas solid reactions - Iso surface concentrations

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Summary of Previous Results

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  1. Summary of Previous Results • Atom probe experimentation • Atomic scale measurement of gas-solid reactions of Al and Oxygen • Compound formation • Study of Interfacial chemistry • -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 • 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

  2. Atom Probe Data for ReaxFF • - Original AP data • Data required for ReaxFF • Modifications • Future Steps • Gas solid reactions of near space environment condition • Surface reactions / orientation dependence of reactions

  3. 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 10-3Torr for 10 min. The 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.

  4. Interface from Gas-Solid Reactions Measurement of two dimensional interfaces. Bulk Al2O3 phase Bulk Al phase Interface 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

  5. Iso surface-Al (41%) Iso surface-Al (80%) Al (97%) O (1.93%) Image of changing interfacial isosurfaces with changing interfacial chemistry. Interface is uniform, and the shape of interface does not change significantly with chemistry.

  6. Atom Probe Data Range File Number=11 Ion1=Al Ion2=O Ion3=H …… [Ranges] Number=23 Range1=13.3740 13.8830 Vol:0.01661 Al:1 Color:33FFFF Range2=8.9770 9.2620 Vol:0.01661 Al:1 Color:33FFFF Range3=26.8780 27.4970 Vol:0.01661 Al:1 Color:33FFFF Range4=15.8811 16.4270 Vol:0.02883 O:1 Color:6666FF Range5=7.9460 8.1220 Vol:0.02883 O:1 Color:6666FF Range6=1.0000 1.0830 Vol:0.00000 H:1 Color:CCCC00 Range7=2.0020 2.0400 Vol:0.00000 H:2 Color:FF0000 Range8=21.3820 21.9550 Vol:0.04543 Al:1 O:1 Color:FF3333 Range9=42.8450 43.5160 Vol:0.04543 Al:1 O:1 Color:FF3333 Range10=23.2730 23.5960 Vol:0.06204 Al:2 O:1 Color:00FF00 ------------- POS file mass = 70 and charge=3 resulting in m/n peak in range of 23.2 - 23.5.  Range10=23.2730 23.5960 Vol:0.06204 Al:2 O:1 Color:00FF00  

  7. AP Data ReaxFF Data Al 4.00948 4.81846 36.33220 1Al 0.27611 4.06606 32.27097 1Al 6.66427 45.77823 34.90955 1 O Al All the compounds were identified and selected from the POS file Compound ions converted into respective constituent ions at a given position

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