Abstract
Aluminum oxidation and ignition in water vapor and in mixed water/oxygen environments were studied experimentally. Oxidation experiments were performed using a thermogravimetric technique. Samples pre-heated to specific temperatures were also recovered and produced phases were analyzed using x-ray diffraction. Ignition was studied by feeding aluminum particles into a laser jet. The laser power was increased stepwise to determine the threshold power required for particle ignition. Oxidation of aluminum in water occurs in several steps, which is generally similar to the oxidation of aluminum in oxygen. A new oxidation step occurs at the aluminum melting point only when water vapor is present. This new oxidation step is shown to occur because of an unusual permeability of γ-Al2O3 for OH. Stressed γ-Al 2O3 was observed to behave as a semi-permeable membrane allowing preferential transport of OH but no oxygen towards aluminum surface. It was also observed that transition alumina polymorphs were stabilized in presence of water so that formation of α-Al2O3 was delayed and the particles were completely oxidized before the entire oxide coating was transferred to α-Al2O3. Finally, ignition of aluminum particles in water was observed to occur at much higher laser threshold powers compared to ignition of the same particles in air.
Original language | English (US) |
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Title of host publication | 44th AIAA/ASME/SAE/ASEE Joint Propulsion Conference and Exhibit |
State | Published - Dec 1 2008 |
Event | 44th AIAA/ASME/SAE/ASEE Joint Propulsion Conference and Exhibit - Hartford, CT, United States Duration: Jul 21 2008 → Jul 23 2008 |
Other
Other | 44th AIAA/ASME/SAE/ASEE Joint Propulsion Conference and Exhibit |
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Country/Territory | United States |
City | Hartford, CT |
Period | 7/21/08 → 7/23/08 |
All Science Journal Classification (ASJC) codes
- Aerospace Engineering
- Control and Systems Engineering
- Space and Planetary Science
- Energy(all)
- Electrical and Electronic Engineering
- Mechanical Engineering