Modelling of thermal conductivities of Si3N4-SiC refractories and Ti3SiC2-SiC composites

Silicon nitride bonded silicon carbide (Si3N4-SiC) refractories are commonly used as the sidewall of aluminium electrolysis cells. They have to withstand an extremely corrosive molten electrolyte bath for long periods. The sidewall is normally protected with a layer of solidified electrolyte (called frozen ledge), which is sensitive to the thermal conductivity of the sidewall. In the present work, a review of the literature on modelling methods for predicting the effective thermal conductivity of dense composites and porous materials was undertaken. Selected modelling methods were then applied to calculate the effective thermal conductivities of commercial Si3N4-SiC refractories and laboratory synthesized Ti3SiC2-SiC composites (titanium silicon carbide bonded silicon carbide). The thermal conductivities of two commercial Si3N4-SiC refractory samples and eight laboratory synthesized Ti3SiC2-SiC composite samples were measured by using laser flash technique and compared with the modelling results