Combustion of zirconium foils in oxygen
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U. Anselmi-Tamburini Department of Physical Chemistry, University of Pavia, Pavia, Italy
Z.A. Munira) Facility for Advanced Combustion Synthesis (FACS), Department of Chemical Engineering and Materials Science, University of California, Davis, California 95616 (Received 25 February 2000; accepted 5 July 2001)
The combustion of zirconium foils in an oxygen environment was investigated for foils ranging in thickness from about 22 to 124 m and for oxygen partial pressures ranging from about 0.3 to 0.9 atm. Temperature profile measurements showed indications of an after-burn, which became especially significant in the combustion of thicker foils. The dependence of the combustion wave temperature and velocity on the oxygen partial pressure was determined. For any partial pressure, wave velocity decreased with an increase in foil thickness. Wave propagation in this system is a complex process and is dictated by oxide formation and oxygen dissolution. The results are examined in light of a finite difference model. I. INTRODUCTION 1
In a previous paper, we presented a finite difference model for the combustion of zirconium in oxygen, examining the general effects of dilution, and the equivalent of particle size on the process. In another paper, we presented results of investigations on the combustion of zirconium powders in oxygen.2 In this paper, we present results of experimental work on the combustion of zirconium foils in oxygen and compare these results to those predicted by the finite difference model. While investigations on metal foil combustion in gaseous environments had been made before,3 much of the previous research involving foils focused on reactions between solid components in multilayer systems.4 –7 The combustion of zirconium powder in oxygen and air was recently investigated by Anselmi-Tamburini, et al.8 Pressed powder compacts with various levels of dilution were reacted in an oxygen-containing atmosphere. By quenching the reacting samples at various stages of combustion and examining the microstructure, they proposed a mechanism for the combustion process in this system. It was proposed that for pure zirconium with additions of zirconia as a diluent, the combustion wave is associated only with the reaction of gaseous oxygen and zirconium particles on the surface of the sample. As the wave propagated, heat transfer to the interior of the sample caused a solid-state reaction between the zirconium particles inside the sample and the diluent zirconia. a)
Address all correspondence to this author. e-mail: [email protected] J. Mater. Res., Vol. 16, No. 9, Sep 2001
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This was indicated visually by the discoloration of the oxide and structurally by an increase in the lattice parameter of zirconium, indicating an increase in oxygen content. As the temperature continued to rise, the zirconium inside the sample melted and reacted with the diluent zirconia to form an oxygen-rich zirconium solution. As the oxygen content continued to increase due to oxyg
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