Explosion of Burning Zirconium Droplets Caused by Nitrogen.

Single droplets of zirconium were photographed as they burned luminously in free fall. When the oxidizer was oxygen containing small amounts of nitrogen (less than 5 percent), the burning droplets exploded only when a threshold concentration of nitrogen was exceeded. Explosions also occurred when the zirconium was partially nitrided before being burned in pure oxygen. These experiments prove that the presence of nitrogen can cause the explosion of zirconium droplets burning in oxygen-rich atmospheres.