Experimental investigation of the transient combustion regimes of low-gas heterogeneous systems

Abstract

We used chromium-aluminu m and tungsten-titaniu m thermites and an intermetallic mixture of aluminum and titanium with different component particle sizes. The choice of systems was determined by the relationship between the melting points of the starting components and reaction products and the combustion temperatures* of the corresponding compositions (see Tables I and 2). At the combustion temperatures of the systems selected the end products of the reaction do not usually melt, and of the starting components one (in the chromium-aluminu m thermite and the system Ti + AI) or both (tungsten-titani um thermite) melt. This choice of systems makes it possible to study the ignition and combustion of the heterogeneous mixture in the presence of different component interaction mechanisms. By progressive screening the starting components were divided into fractions. The shape of the particles and the state of their surface were examined under the microscope. The percentage of active aluminum was determined by a standard method (gas evolution on reacting A1 with hydrochloric acid) and the specific particle surface S was found from the gas permeability of the aluminum powder. The parameters of the starting components are presented in Tables 1 and 2. The components were mixed by the tumbling barrel method [7], in some cases with further mixing in a mortar. The mixing time was recorded, and the structure of the mixture prepared was analyzed under the microscope.