THERMAL-DISSOCIATION OF ULTRAFINE PASSIVATED NI POWDER

Ultrafine metallic nickel was produced by the evaporation/condensation technique and subsequently passivated by controlled exposure to atmos pheric air. The kinetic and thermodynamic properties of this material during heating in inert gas was studied by microgravimetry, differenti al scanning calorimetry and differential thermal analysis. The propert ies were found to be significantly different from the properties of co mmercial nickel oxide, viz. a smaller stability and a higher dissociat ion rare of the ultrafine material. The dissociation upon heating in H e was found to be composed of two steps and the activation energies of the steps were measured to be 136 and 26 kJ/mol respectively.