[en] The combustion wave propagation in Al–CuO and Al–Bi₂O₃ termite mixtures was experimentally investigated. Waveforms of electric current through the reaction area between electrodes with a given potential difference, chronograms of piezo- and photodiode response, the data of pyrometric measurements, as well as photos of the glowing area were obtained and analyzed. There were revealed the advance filtration of the gas component through pores of mixture, the generation of charges providing considerable electrical conductivity of chemical reaction products, the connection of electrical conductivity dynamics with the optical radiation of the chemical conversion region. (paper)

[en] This paper presents the results of experiments carried out to reveal the influence of the initial parameters of the thermite mixture Al–CuO on the signs of a chemical reaction between its components. Initial parameters were the characteristics of the starting components, preparation conditions and characteristics of the mixture and samples, experimental schemes, methods of initiation. The most important parameter was the preliminary mechanical activation of mixture. The prepared mixture with controlled porosity was placed in experimental assemblies and a chemical reaction was initiated. Values and tendencies of the brightness temperature and the propagation rate of reaction area were determined for different initial parameters of mixture and initiation conditions. The reaction in the volume of the experimental assembly goes into flare combustion in open space. Values of brightness temperature at the stage of flare formation have a stochastic character, determined by the random distribution of reaction sites in the initial volume of the components. A high-speed camera, a pyrometer, photoelectronic and electrocontact sensors were used as diagnostic tools. The final goal of the study is to optimize parameters of mechanical activation of mixture for its effective applying in various conditions. (paper)

[en] The regularities of mechanical activation (MA) and the reactivity of an high-energy 15Al + 85Bi₂O₃ (wt %) system have been studied with the use of X-ray diffraction analysis, synchronous thermal analysis, and the measurement of the ignition temperature upon the contact with a hot surface. For the nonactivated system, the intercomponent interaction has not been recorded upon their heating in a DSC cell up to 760°C. When MA is carried out, the reaction partly occurs directly in the course of grinding and upon the subsequent heating. In the course of heating at a rate of 10°C/min, the intercomponent interaction proceeds to yield Bi metal and amorphous Al₂O₃ in a temperature range of 350–800°C, with maxima being observed at 520 and 630°C. At temperatures below 480°C, the reaction occurs in nanolayers, as is evident from the position and shape of the melting curve obtained for formed bismuth. The effects of the duration of MA on the conversion of the components, reaction kinetics upon heating in the DSC cell, the temperature of ignition upon the contact of an activated sample with a hot surface, and the rate of mixture combustion have been determined. The optimal duration of MA, at which the ignition temperature is minimum, has been found.