Abstract
The most typical thermal insulating materials used in the cathode lining in aluminium
electrolysis cells are Moler, calcium silicate, or vermiculite. The thermal insulation is
important for the overall thermal and dimensional stability of the cell. The chemical
stability of the thermal insulating materials is important, especially in cases where the
refractory layer above the thermal insulation layer becomes fully penetrated by sodium
vapour. The chemical degradation of thermal insulating materials by sodium vapours has
been investigated in a laboratory test resembling the environments in the cathode lining.
The exposed materials were investigated with respect to changes in the microstructure and
chemical and mineralogical composition by a combination of optical and electronic
microscopy and powder X-ray diffraction. These investigations revealed different reaction
patterns for the three materials and the formation of new mineralogical phases were
identified. Finally, these findings were compared with chemical reactions with sodium
based on computational thermodynamics.
electrolysis cells are Moler, calcium silicate, or vermiculite. The thermal insulation is
important for the overall thermal and dimensional stability of the cell. The chemical
stability of the thermal insulating materials is important, especially in cases where the
refractory layer above the thermal insulation layer becomes fully penetrated by sodium
vapour. The chemical degradation of thermal insulating materials by sodium vapours has
been investigated in a laboratory test resembling the environments in the cathode lining.
The exposed materials were investigated with respect to changes in the microstructure and
chemical and mineralogical composition by a combination of optical and electronic
microscopy and powder X-ray diffraction. These investigations revealed different reaction
patterns for the three materials and the formation of new mineralogical phases were
identified. Finally, these findings were compared with chemical reactions with sodium
based on computational thermodynamics.