EFFECTS OF ATOMIZATION SURFACES AND MODIFIERS ON THE ELECTROTHERMAL ATOMIZATION OF CADMIUM

Atomization of cadmium on tungsten carbide, molybdenum carbide and met allic palladium coated platforms and on pyrolytic graphite coated plat forms with and without tungsten, molybdenum and palladium modifiers ha s been studied. A physical vapour deposition method is used for coatin g. A high thermal stability, a greater appearance temperature and a de crease in sensitivity are found when compared with atomization on conv entional platforms. Diffusion and kinetic parameters are obtained usin g different models. More than one activation energy (E(a),) and freque ncy factor (nu) are obtained depending on the atomization temperature while the atomic vapour appears. These results may indicate that more than one formation process is simultaneously present or that the evolu tion from one formation process to another is temperature dependent. G reater values of E(a) and nu are found during atomization on the molyb denum carbide coated platform and when molybdenum or palladium modifie rs are used. This may suggest that strong cadmium-metal interaction is present. This strong interaction is not present when palladium is use d as a metallic coating, although a similar trend in thermal stability is observed. The contribution of the expansion to the atomic vapour d issipation is also evaluated.