ESTIMATION OF THE REACTIVITY OF ALUMINUM SUPERFINE POWDERS FOR ENERGETIC APPLICATIONS

Abstract

A new quantitative method of estimating the reactivity of aluminum superfine powders for energetic applications has been suggested. The method is based on differential thermal analysis-thermogravimetry (DTA-TG) data analysis in air as oxidizers for measurement first of four reactivity parameters (temperature of intensive oxidation onset, maximum rate of oxidation, degree of conversion of metallic aluminum, and specific heat release). After the comprehensive testing of the powders, the most reactive powder was identified. The special features of the oxidation process for the most reactive samples of aluminum superfine powder, obtained with a wires electrical explosion method, are explained and a theoretical mechanism for a new phenomenon, “pulsed oxidation” of superfine aluminum powder in air, is proposed.

Keywords:

• aluminum superfine powders
• oxidation
• thermal analysis
• reactivity
• enthalpy

Acknowledgments

This work was supported by the Korea Research Foundation under grant no. KRF-2002-042-D00074 and was performed using the facilities of the Research Center for Machine Parts and Materials Processing at the University of Ulsan. The authors are also grateful to Prof. H. Gleiter (Institute of Nanotechnology, Forschungszentrum Karlsruhe, Germany) and Drs. D.V. Tikhonov and G.V. Yablunowsky (High Voltage Institute, Tomsk Polytechnic University, Tomsk, Russia) for useful discussions and recommendations.

Notes

^a Mench et al. (1998) data.

^b Produced by method of spraying molten metal (Pokhil et al., 1972).

^c Produced by wires electrical explosion method (Kwon et al., 2001).

^d Produced by physical vapor synthesis method (Gleiter, 1989).

^e a _s = 6/(ρ_Al S _sp) for spherical aluminum particles, where ρ_Al = 2.7 g/cm³.

^a Mench et al. (1998) data.

^b α₂ up to 700 °C.