The Mesoscale Structure Evolution of the Carbon Electrode during the Baking Process Based on X-ray Computed Tomography

Abstract

The baking process plays a decisive role in determining the physicochemical properties of the carbon electrode used in aluminum production. Although previous studies have revealed the relationship between the performance of the carbon electrode and the baking process through experimental and numerical modeling approaches, the formation mechanism of the porous structure during the baking process is not yet fully understood, which has hindered further optimization of the electrode performance. To systematically investigate the structure and performance changes of the carbon electrode during the baking process, this study employed computed tomography (CT) scanning technology to reconstruct the three-dimensional grains-matrix-pore system and further revealed its mesoscale structure evolution. Combined with the digital volume correlation (DVC) method and experimental validation, the study accurately characterized structural deformation and the dynamic behaviors of pores, uncovering the pore formation mechanism and clarifying the effects of different baking stages on electrode performance. The results show that the porous structure (pore size >100 μm) primarily formed during the low-temperature baking stage (room temperature to 410 °C). During this process, most newly formed pores exhibited a many-to-many connectivity pattern with the original pores and established a complex gas discharge network. This finding guides the identification of the key temperature range during the baking process of carbon electrodes, particularly between 240 and 410 °C. Measures such as slowing the heating rate to allow for the uniform and gradual release of volatiles may help reduce the formation of large pores, improve the structural integrity of the electrode, and consequently enhance the electrical conductivity and density of the carbon electrode.