Evolution of Particle Temperature and internal Composition For Zirconium Burning in Air

摘要

An expeimental study of single zirconium particle condition in air is presented, with emphasis on understanding the mechanism causing particle temperature jumps and the subsequent explosions. The expeiment involved generatin guniform, approx 200 umm-size particles of controlled initial temperature by a pulsed micro-arc, letting them burn in air in free fall, measuring their instantaneous temperatures with a three-wavelength optical pyrometer, quenching the burning particles during various stages of burning, and subsequently analyzing the particle's internal composition using a high-resolution X-ray electron micro-probe. Special techniques were develoepd to separate out the radiation from the gas-phase luminous zone in the temperature determination, and to rapidly quench the particles in order to freeze their internal creases; oxygne and nitrogen are dissolved in the particle temperature first increases and then deinclusins have bene detected. The maximum particle temperature is considerably less than the boiling temperatures of Zr and ZrO_2. It is demonstrated that the occurrence is considerably less than the boiling temperatures of Zr and ZrO_2. it is demosntrated that the occurrence of the particle temperature jumps and explosions is due to the attainment of the eutectic state within the particle interior, which leads to the precipitous formatio of solid alpha Zr and ZrO_2 from supersaturated Zr-O solution, with simultaneous heat release and nitrogen gas release.