Investigating wettability of cryolitic melts on carbon/graphite cathode materials in cooperation with image analysis

摘要

Wetting and penetration of cryolitic melts into carbon cathodes during aluminum electrolysis is an important factor for cathode deterioration. This work is aimed to develop a better digital method for characterization of the porous structure and the cryolite wettability on C/G cathode materials for aluminum electrolysis. The wettings by sodium or potassium cryolite melts at 700-960 °C were determined using a modified sessile drop method, which were presented in correlation with image analysis on the internal porosity, pore size distribution, pore shape and direction, pore connectivity, and so on. The results indicated that the wetting process was porous structure and materials dependent, where pores distribution was the strong interaction and potassium cryolite wetted the cathode surface very well. Full graphitic and graphitized cathode samples had similar wetting due to their homologous porous structure and materials, while semi-graphitic cathode sample was different entirely. The profiles of penetrated cryolite across the wetted interface into the cathode samples after wetting were detected using SEM-EDS analysis. It was found that the pores number, specific surface area and graphite content of cathode materials contributed the most to cryolite penetration into the carbon cathodes.