Oxidation and ignition of aluminum particles in the presence of water vapor

Document Type

Conference Proceeding

Publication Date

12-1-2008

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. © 2008 by the American Institute of Aeronautics and Astronautics, Inc.

Identifier

77957838094 (Scopus)

ISBN

[9781563479434]

Publication Title

44th AIAA ASME SAE ASEE Joint Propulsion Conference and Exhibit

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