A study of the oxidation of ultrafine powder of activated aluminum with water to form an IR-opaque aerosol

Abstract

The reaction of oxidation of ultrafine powder of activated aluminum (UFPAA) with water is studied. Activated aluminum is meant to be a juvenile aluminum powder coated with a water-soluble polymer film (polyethylene oxide). When exposed to water, the polymer film dissolves, allowing metallic aluminum to react with water. A method of preparation of UFPAA using a ball mill is described. The reactions of UFPAA with water in closedand open-type reactors are investigated. For the closed-type reactor, the effect of the initial amount of UFPAA and of the Al-to-H2O ratio on the temperature and pressure of the process, as well as the composition of the solid and gaseous reaction products, are determined. It is found that, at a UFPAA sample weight of ≥100 g, the temperature and pressure of the reaction increase above the critical values for water (T = 374.2°C, P = 22.14 MPa). The open-type reactor is demonstrated to produce aerosol. It is shown that, the reaction of 100 g of initial UFPAA with water at Al-to-H2O ratios ranging from 1: 1 to 1: 5 produces aerosol particles containing aluminum in concentrations CAl from 13 to 18 wt %. The dependence of the masking ability of aerosols (MΔλ) in the IR region of the electromagnetic radiation (Δλ = 3–14 μm) on CAl is measured. The MΔλ(CAl) dependence is a monotonically increasing function, with the maximum, MΔλ = 1.9 m2/g, reached at CAl = 18 wt %.