The self-combustion of structurally co-deformed powder mixtures: a direct view of the process

Abstract

The direct observation of the self-combustion of structurally co-deformed elemental powders, in the course of the ball milling treatment, was possible by employing quartz transparent reaction vessels and a high-speed image acquiring system. The synthesis of a titanium–silicon system was chosen as a case study. Whereas the primary ignition appears to be linked to an impact event, the reaction spreads out because of the violent and continuous throwing out of burning particles inside the milling vial. The reaction reaches completion within milliseconds. The use of radiation pyrometers enabled us to register the combustion temperature, which reached the melting temperature of the reaction product and approached the adiabatic temperature of the process. Results indicate that the underlying reaction mechanism relies on liquid–solid diffusion as in the conventional self-sustaining high-temperature synthesis process. Important information of the ball–vial dynamics was also obtained by tracking the trajectory of the ball, which, due to being heated up to luminosity, became visible for several cycles of the reciprocating milling machine.