A collision model for fume formation in metal oxidation

During the oxidation of copper at high temperatures, two simultaneous mechanisms are observed in the hot stage environmental scanning electron microscope: the nucleation and growth of solid cuprous oxide crystals and the formation of a solid fume composed of very small copper and copper oxide particles. A collision model for fume formation in metal oxidation is presented. By calculating the collision frequency between evaporated copper atoms and oxygen molecules in the gas phase, the amount of fume formed can be estimated. Although the effect of Van der Waals forces between particles has not been quantified, the temperature difference between the two gases was taken into account and yielded a multiplying factor of 4 in the collision frequency for copper oxidation at 950 °C. Unoxidized copper particles were formed from unsuccessful elastic collisions between Cu(v) and O₂. These copper particles are composed of interpenetrating icosohedra and possess a high crystalline perfection. Formerly Graduate Student, Department of Metallurgical Engineering, The Ohio State University, Columbus, OH 43210.