Inflammability of zirconium powders and its alloys in the suspended state

Abstract

1. The values of the lower concentration limits of inflammability (LCL) of aerosols of Zr, Ti, Si, and alloys Zr-Ti and Zr-Si were determined. 2. The character of the dependence of the LCL of aerosols on the alloy's composition coincides with the character of this dependence for the temperature of spontaneous combustion of powder in a layer, which is related with the constitution diagram of the alloy. Inflammability of an alloy is determined primarily by its chemical activity. The induction period and flame propagation rate are also determined by the alloy's activity. 3. Burning of the investigated alloys probably occurs on the surface of molten particles. Oxygen is dissolving in the liquid metal and, when the solubility limit is reached, the oxide phase crystallizes from the melt. As solid films are accumulated, the reaction is slowed down and stops when the liquid-metal phase disappears. Silicon, owing to its high volatility, burns in the vapor phase. 4. The method of partial filling of a spherical bomb with aerosol permits obtaining homogeneous aerosols in a wide range of concentrations and using thin-walled glass bombs facilitates the use of optical methods of investigation.