Characterization of sodium and fluoride penetration into carbon cathodes by image analysis and SEM-EDS techniques

Abstract

The porous structure of carbon cathodes is materials dependent, which can be related to sodium and fluoride penetration during aluminum electrolysis. This work is aimed at developing a better digital method for characterization of the pores and the penetration resistance of the cathode products. The profiles of penetrated Na, F, Al versus penetration depth in the cathode samples after aluminum electrolysis were obtained using SEM-EDS analysis. The internal porosity, pore size distribution, pore shape and orientation and pore connectivity were also characterized by image analysis. It is found that the graphitization, total and partial porosity, pore orientation and connectivity can contribute to the sodium and fluoride penetration into the carbon cathodes. The penetration behaviors varied with change in cathode materials (from semi-graphitic, full graphitic to graphitized carbons).