Mechanisms of pulsating combustion during synthesis of advanced materials

Gasless combustion is a specific type of combustion, where all initial reac tants, as well as intermediate and final products, remain in condensed (sol id or liquid) state. This process is of great interest because of its prosp ective applications in combustion synthesis of advanced materials. The stab ility of combustion wave propagation is an important factor in determining the quality of materials produced by combustion synthesis. In this work, a digital high-speed microscopic video recording method is used for direct ob servation and quantitative characterization of pulsating combustion in seve ral gasless systems. The experimental data quantitatively describe, for the first time, oscillations of local instantaneous velocity at length scale a bout 10 mu m and time scale similar to 10(-3) s. Three systems investigated were: Ta-C, Nb-B, and Ti-C. Two new mechanisms of pulsating combustion wer e identified: crack-induced oscillations occur in Nb + B and Ta + C syst em s, while ignition-extinction oscillations take place during reaction in Ti + xC system.