Influence of thermal process on particle size distribution of ultrafine magnesium powder prepared by inert gas condensation method

Abstract

Ultrafine magnesium powder has become a research hotspot for the last few years because of its high-activity and low-density. Inert gas condensation method is a better method compared to mechanical pulverization method to produce magnesium ultrafine powder with high-purity, narrow particle size distribution and short production cycle. As particle size distribution is a vital factor when it comes to determine the application area, it is necessary to investigate particle size distribution of ultrafine magnesium powder prepared by inert gas condensation method. The purpose of this research is to determine particle size distribution of ultrafine powder produced by inert gas condensation method under different thermal conditions, then to provide a reliable method for optimum thermal parameter selection. Thermal mechanisms of ultrafine magnesium powder preparation using inert gas condensation method are proposed. Dynamic equations for the nucleation, evaporation/condensation, coagulation and deposition processes are established. This paper develops a convenient way for the prediction of the particle size distribution by deriving a modified Monte Carlo method, which is able to calculate the particle size distribution giving only a relative error less than 3%, compared with the experiments. An attempt to discover the relation between particle size and absolute pressure is conducted in the discussion part. The particle size increases exponentially with the condensation pressure increases. The method derived here may offer a mathematical method to predict particle size distribution of other ultrafine metal powder prepared by inert gas condensation method, then to choose appropriate thermal conditions for different applications.