Mechanochemistry of Bi2O3. 2. Mechanical Activation and Thermal Reactions in a High-Energy Al + Bi2O3 System

The regularities of mechanical activation (MA) and the reactivity of an high-energy 15Al + 85Bi(2)O(3) (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 non-activated system, the intercomponent interaction has not been recorded upon their heating in a DSC cell up to 760 degrees 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 degrees C/min, the intercomponent interaction proceeds to yield Bi metal and amorphous Al2O3 in a temperature range of 350-800 degrees C, with maxima being observed at 520 and 630 degrees C. At temperatures below 480 degrees 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.