ELECTROTHERMAL ATOMIZATION OF COPPER FROM GRAPHITE AND TANTALUM SURFACES

The vaporization/atomization characteristics of Cu samples from graphite and Ta-lined tubes using both Ta and graphite platforms have been studied at atmospheric pressure. First order release of Cu from both Ta and graphite surfaces was found. The desorption rate of Cu is faster from Ta in spite of the larger activation energy of desorption for the Cu/Ta system over that for Cu/graphite, 54 and 42 kcal mol respectively. Neither activation energy corresponds to ΔHv for Cu from bulk. Copper is readsorbed onto the graphite and Ta upon secondary collisions with these surfaces. However, with vaporization from the platform, the wall temperature is sufficiently elevated that the Cu desorption rate from the wall is rapid, and Cu collisions with the wall appear to be elastic. The use of a platform may be advantageous from the analytical point of view; however, it may complicate the interpretation of results when fundamental studies on the basic interactions occurring in the furnace are investigated. © 1990.