Role of liquid phase amounts in the pore evolution of lightweight bauxite: Experimental and thermal simulation studies

Abstract

In the present work, the liquid phase amount during the sintering of lightweight bauxite was adjusted by adding fused magnesia micropowder. The addition of fused magnesia led to an increase in the liquid phase amount. The diffusion between the liquid phase and the solid phase increased and, consequently, favoured the migration of grains, which resulted in more pores becoming trapped between the grain boundaries. Therefore, the lightweight bauxite exhibited reduced open porosity, increased closed porosity and decreased pore size. However, when the amount of fused magnesia was further increased, the pinning effect and volume expansion caused by the formed spinel hindered the migration of the boundaries and led to a loose structure. Therefore, the closed porosity decreased and the open porosity increased instead. For our sintering conditions, with a liquid phase amount of around 17 wt%, lightweight bauxite with a low open porosity of 7.5%, a high closed porosity of 15.6% and a small median pore diameter of 5.03 µm can be fabricated.