Fig. 1. Rocket nozzle via IR process (U.S. Patent No. 6,598,656, Sandhage, et al.)

1. Fig. 1. Rocket nozzle via IR process (U.S. Patent No. 6,598,656, Sandhage, et al.) Fig. 2. MgAl2O4 particles on an Al2O3 surface after immersion in Al-Mg(liq) for 0.5 h at 1100oC. 12.0 1100oC 10.0 8.0 Cross-section of MgAl2O4 layers (Layer Thickness)2 (X10-11 m2) 6.0 4.0 2.0 Al2O3 0.0 0 5 10 15 20 25 Time (104 sec) Fig. 3. MgAl2O4 layers on Al2O3 after immersion in Al-Mg(liq) for 168 h at 1000oC. Fig. 4. MgAl2O4 thickness vs. reaction time at 1100oC. Mechanisms of Incongruent Reduction (DMR-0341010)K. H. Sandhage, R. L. Snyder, Georgia Institute of Technology “Incongruent Reduction (IR)” refers to a fluid/ solid reaction that results in the reduction of a solid compound via the formation of an inter-mediate solid product. IR reactions have been used by the PI’s to produce very high-melting, erosion-resistant, lightweight rocket nozzles (Fig. 1). Such novel processing is an attractive and cost-effective means of manufacturing advanced ceramic composites with complex 3-D shapes for aerospace, automotive, energy production, and defense industries. This project is aimed at obtaining a basic understanding of the mechanism of IR in a model system: IR of Al2O3 by an Al-Mg melt, which occurs via formation of spinel, MgAl2O4. The spinel initially forms as oriented particles on an Al2O3 surface (Fig. 2). Further MgAl2O4 formation over time leads to a stack of continuous spinel layers on Al2O3 (Fig. 3). The rate of layer thickening obeys a parabolic law (Fig. 4), which is consistent with solid-state diffusion as the rate-limiting step.

2. Mechanisms of Incongruent Reduction (DMR-0341010)K. H. Sandhage, R. L. Snyder, Georgia Institute of Technology • This research has been (Ohio State University, OSU) and is being (Georgia Institute of Technology, GIT) integrated with education via activities such as: • Integration into classroom lectures: l“Principles of Materials Science and Engineering” (MSE 605, Snyder/OSU) l“Materials Characterization” (MSE 715, Snyder/OSU) l”High-Temperature Corrosion” (MSE 736, Sandhage/OSU) • l“Introduction to Engineering” (MSE 1001, Sandhage/GIT) • l “Chemical and Environmental Properties of Materials” (MSE 8003J, Sandhage/GIT) • Integration into undergraduate research projects/senior theses on incongruent reduction-based processing (6 undergraduates have been involved to date): l“Ceramic body armor” (Mr. Jason Zielsdorf, supervised by Sandhage/OSU) l“Bulk metallic glass composites” (Mr. Geoff Lofstrom, Mr. Alex Tsai, supervised by Sandhage/OSU) l“Rocket nozzle composites” (Ms. Erin Beatty, Ms. Wendy Fu, Mr. James Sinclair, supervised by Sandhage/GIT)