Factors Controlling the Combustion of Zirconium Powders

Abstract

The activity of zirconium metal powders was studied by measurements of ignition temperature, burning time, and ignition energy on subsieve powders prepared by calcium reduction of and on coarse powders made by grinding fused zirconium. Particle diameter of 10 microns represents approximately the dividing line between hazardous and nonhazardous powder, using 0.01–0.04 joule spark ignition energy as a criterion. Thermal ignition appears to occur by spontaneous combustion, and a theory was developed which accounts qualitatively for the dependence of ignition temperature on a number of variables. The burning time of Zr powders is related to, but not uniquely determined by, the surface area. Ignition sensitivity of Zr powders was not successfully decreased by alloying with Ti, Ni, Cu, Fe, Co, or H2. Hazards are discussed briefly, and details of evaluation methods reported.