Reaction interface for heterogeneous oxidation of aluminum powders

Shasha Zhang, Edward L. Dreizin

Research output: Contribution to journalArticlepeer-review

54 Scopus citations

Abstract

Heterogeneous oxidation of aluminum is rate limited by diffusion through a growing aluminum oxide layer. If inward diffusion of oxygen ions is faster than outward diffusion of aluminum, the reaction will occur at the inner interface of the oxide. Conversely, the reaction will occur at the outer oxide surface if outward diffusion of aluminum is faster. The location of the heterogeneous reaction is identified processing results of thermogravimetric measurements for two oxidizing spherical aluminum powders with different but overlapping particle size distribution. For each experiment, the measured weight gain is distributed among particles of different sizes assuming that the rate of oxidation is proportional to the reactive interface area. Different models are considered to determine the interface area. For a ductile oxide shell, when there is no void between oxide and aluminum, two cases with the reaction occurring at both inner and outer surfaces of the shell were evaluated. In addition, a case with the reaction at the outer surface of a rigid oxide shell is considered, for which a void inside the particle forms when the aluminum core is shrinking. Oxidation weight gains for the same size particles present in different aluminum powders are expected to be identical to each other when the calculated reactive interface area reflects the true oxidation mechanism. It is concluded that the reaction at the outer surface of a rigid oxide shell describes the experiments most accurately. Thus, the outward diffusion of aluminum ions controls the rate of heterogeneous oxidation of aluminum in a wide range of temperatures of approximately 400-1500 C. The conclusion is further supported by the electron microscopy of particles quenched at different temperatures, showing oxide surface features consistent with the identified reaction mechanism.

Original languageEnglish (US)
Pages (from-to)14025-14031
Number of pages7
JournalJournal of Physical Chemistry C
Volume117
Issue number27
DOIs
StatePublished - Jul 11 2013

All Science Journal Classification (ASJC) codes

  • Electronic, Optical and Magnetic Materials
  • Energy(all)
  • Physical and Theoretical Chemistry
  • Surfaces, Coatings and Films

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