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

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

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

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

mass = 70 and charge=3 resulting in m/n peak in range of Range10= Vol: Al:2 O:1 Color:00FF00 Number=11 Ion1=Al Ion2=O Ion3=H …… [Ranges] Number=23 Range1= Vol: Al:1 Color:33FFFF Range2= Vol: Al:1 Color:33FFFF Range3= Vol: Al:1 Color:33FFFF Range4= Vol: O:1 Color:6666FF Range5= Vol: O:1 Color:6666FF Range6= Vol: H:1 Color:CCCC00 Range7= Vol: H:2 Color:FF0000 Range8= Vol: Al:1 O:1 Color:FF3333 Range9= Vol: Al:1 O:1 Color:FF3333 Range10= Vol: Al:2 O:1 Color:00FF POS file Range File -2.21E E E E E E al2o -4.28E E E E E E E E E E E E E E E o Atom Probe Data XYZm/n

-2.60E E E al2o -1.52E E E al 1.32E E E alo XYZm/n AP Data 1.All the compounds were identified and selected from the POS file 2.Compound ions converted into respective constituent ions at a given position -2.60E E E E E E E E E E E E-02 ReaxFF Data XYZAtom type -2.60E E E E E E E E E E E E E E E o2 Al O Al Al Al