Absorption of metallic sodium in carbon cathode materials Original Research Article

The absorption of sodium vapour in commercial cathode materials for aluminium electrolysis has been studied within the range 1020–1227 K and 3–600 Torr. The absorption increases strongly with decreasing degree of graphitization. The absorption of sodium in the commercial materials can be described as a BET isotherm with calculated surface area between 9 and 124 m2/g. The measured surface area by helium absorption, however, is less than 1 m2/g. Pure synthetic graphite behaves differently and a minimum sodium pressure is needed before absorption starts.