| AVS 58th Annual International Symposium and Exhibition | |
| Applied Surface Science Division | Monday Sessions |
| Session AS-MoA |
| Session: | Quantitative Surface Chemical Analysis and Technique Development - Part II |
| Presenter: | James Ohlhausen, Sandia National Laboratories |
| Authors: | J. Ohlhausen, Sandia National Laboratories E. Coker, Sandia National Laboratories A. Ambrosini, Sandia National Laboratories J. Miller, Sandia National Laboratories |
| Correspondent: | Click to Email |
A procedure for quantitative ToF-SIMS analysis of the re-oxidation of iron oxide particles in a ceramic matrix is discussed. Iron oxide is reacted with yttria stabilized zirconia (YSZ) to create a composite that facilitates the high temperature decomposition of CO2 and H2O. In the two step process, Fe3O4 is partially reduced to FeO by heating to high temperatures (>1300 °C) under inert atmosphere. It is then re-oxidized at < 1200 °C under CO2 or H2O yielding CO or H2 respectively. The reactivity of this two step solar-thermochemical process is being investigated by varying the concentration of iron in YSZ up to and past its solid solubility point, thus affecting the size of iron oxide particles in the matrix, and hence their rate and extent of re-oxidation. For the SIMS experiment, the YSZ sample containing natural abundance iron oxide was mixed with an organic binder, isostatically pressed into a disc and calcined in air at 1450 °C. This disc (~ 10mm diameter, 2mm thickness) was thermally reduced at 1400 °C and then re-oxidized at 1100 °C in the presence of C18O2. The ratio of 18O to 16O shows the extent of oxygen exchange for each iron oxide particle.
For ToF-SIMS analysis, samples are prepared by cross-sectioning and polishing by conventional metallographic preparation techniques followed by ion milling with Cs+ in the ToF-SIMS. ToF-SIMS data are acquired from the cross section only after surface contaminants are removed and a “bulk” condition exists on the exposed surface. Data are acquired in a fashion that maximizes the ability to correct for detector saturation, thus providing quantitative oxygen isotopic results with little error. Data analysis method uses a combination of multivariate analysis for particle identification and conventional analysis for quantitative isotopic ratioing. Details of analysis procedures will be discussed along with results for a range of iron oxide particle sizes.
Sandia National Laboratories is a multi program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.