Graphite sublimation temperatures, carbon arcs and crystallite erosion

Abstract Past efforts to measure the sublimation temperature of graphite by electric arc and cavity experiments are reviewed. Critical difficulties of interpretation of various anode reflectance measurements are pointed out, and resolved in terms of the emission of small graphite crystallites from graphite, and the existence of a shallow porous layer on the anode. It is argued that crystallites, which may form the major part of the mass loss, can partly obscure the surface from view. Also in the case of the “standard” carbon anode it is reasoned that the temperature of the observed surface can be controlled by thermal conduction to finely divided subliming carbon, which carries the positive charge of the quiet carbon arc close to the anode. It was concluded that the sublimation temperature of graphite at one atmosphere pressure lies between 3895 and 4020 K, and that little further experimental work needs to be done to define it more precisely, and to establish a new high temperature standard.

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