A COLLISION MODEL FOR FUME FORMATION IN METAL OXIDATION

During oxidation of copper at high temperatures, two simultaneous mechanisms were 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 small copper and copper oxide particles. 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 at 950 degree C. Unoxidized copper particles were formed from unsuccessful elastic collisions between Cu(v) and O//2. These particles are composed of interpenetrating icosohedra and possess a high crystalline perfection.