ISSN 0036-0244, Russian Journal of Physical Chemistry A, 2010, Vol. 84, No. 9, pp. 1576–1584. © Pleiades Publishing, Ltd., 2010. Original Russian Text © A.V. Korshunov, A.P. Il’in, N.I. Radishevskaya, T.P. Morozova, 2010, published in Zhurnal Fizicheskoi Khimii, 2010, Vol. 84, No. 9, pp. 1728–1736. 1576 INTRODUCTION Aluminum powders are extensively used as energy admixtures to solid fuels and pyrotechnic composi- tions and in the production of composition materials and intermetallic compounds [1, 2]. An increase in the activity of metal powders (a decrease in the tempera- ture of sintering, oxidation, and ignition) as their dis- persity increases is related to the size effect caused by an increase in the fraction of nanoparticle surface atoms. At the same time, interrelation between the size of powder particles and their reactivity is not unambig- uous. For instance, aluminum nanopowders (ANP) passivated in air, as distinct from nanopowders of some other metals (Fe, Ti), are not pyrophoric and are com- paratively stable to oxidation during storage [2]. For this reason, studies of size effect manifestations in chemical processes are of obvious interest both from fundamental point of view and for practical applica- tions. Works on the oxidation of aluminum nanopowders are not numerous, their results are often contradictory and cannot be used to determine the reason for the dif- ference between the properties of aluminum nanopo- wders and those of coarse-dispersion powders [2–13]. This is primarily related to the conventionality of the term “nanopowders.” This term is usually applied to high-dispersity powders with some (not regulated) fraction of particles 100 nm and less in diameter. It was, for instance, shown in [2–9] with the use of ther- mogravimetry that a substantial increase in the rate of oxidation of aluminum nanopowders in air compared with coarse-dispersion powders was observed over the temperature range 450–600°C, that is, below the melting point of Al (T m = 660°С). Conversely, it was found in [13] using mass spectrometry of separate par- ticles that the oxidation of Al nanoparticles (~50 nm) suspended in a gas flow did not occur up to 800°С. A sharp increase in the rate of oxidation of alumi- num nanopowders at 450–600°С was explained by cracking of the oxide shells of particles caused by the crystallization of an amorphous oxide layer in [2, 5, 13] and by sample ignition in [4, 9]. According to [13], the rapid oxidation of aluminum nanopowders occurs at the moment of metal melting. The expansion of the metallic core of Al particles by 12% then increases excess pressure inside particles to 88000 atm, which contributes to oxide shell breaking. On the other hand, the authors of [8] consider a mathematical model of the dependence of T m of Al nanoparticles on their diameter; this model takes into account the thickness of the surface oxide layer but ignores the difference between the molar volumes of crystalline and liquid Al. An improved calculation procedure was suggested in [14]; according to this procedure, the oxide shell of Al particles should crack at all temperatures under lin- ear heating conditions. An analysis of the literature data shows that the use of the approach based on the temperature dependence of oxide shell characteristics does not clarify the char- acter of the influence of the dispersity of Al powders on their reactivity. There is no literature data on the influ- ence of the special features of the structure of Al parti- cles and particle-size distribution on the kinetics of oxidation of powders. The purpose of this work was to The Kinetics of Oxidation of Aluminum Electroexplosive Nanopowders during Heating in Air A. V. Korshunov a , A. P. Il’in a , N. I. Radishevskaya b , and T. P. Morozova a a Tomsk Polytechnical University, pr. Lenina 30, Tomsk, 634050 Russia e-mail: korshunov@tpu.ru b Department of Structural Macrokinetics, Tomsk Scientific Center, Siberian Division, Russian Academy of Sciences, Tomsk, Russia Received October 17, 2009 Abstract—The rules governing the oxidation of aluminum nanopowders obtained by the electrical explosion of wires during heating in air under the conditions of linearly increasing temperature and in isothermal regime were studied. The influence of the composition and structure of aluminum particle oxide coating and metallic core on the parameters of the process and the phase composition and morphology of oxidation products was determined. Thermal reaction conditions were shown to depend on thermogravimetry regime, and the kinetic data were used to explain this dependence. The kinetics of oxidation was modeled taking into account the aluminum particle-size distribution function. It was shown that the structures of particles of the nanodis- perse and micron electroexplosive powder fractions were different. DOI: 10.1134/S0036024410090244 PHYSICAL CHEMISTRY OF NANOCLUSTERS AND NANOMATERIALS