Effects of sodium silicate as liquid phase sintering additives on properties of alumina ceramics

Abstract

This research focused on the production of high-performance alumina products. The feasibility of using soluble alkali silicate in liquid phase sintering of alumina was studied. Liquid soluble alkali silicate was used to enhance the plastic forming of alumina and formed liquid phase sintering to attain fired alumina products with high strength, high alumina content and low water absorption. The methodology consisted of the mixing of organic binder with sodium silicate (Na₂SiO₃), used as liquid phase sintering additive, of 0-15 wt%. Magnesium carbonate (MgCO₃), used as the grain growth inhibitor, of 0-1 wt% were added and followed by alumina powders. The mixtures were kneaded thoroughly creating a dough. Alumina bodies with a diameter sizes of 10 and 35 mm were differently obtained from extrusion and uniaxial pressing techniques. Drying and firing process were carried out at 110°C for 24 h and 1600°C for 2 h. The results demonstrated that the addition of Na₂SiO₃ led to an increase of bulk density, while correspondingly showed a lowering of water absorption. Fired alumina products with water absorption of 0.37% were derived by extrusion with the addition of 1 wt% of MgCO₃ and 10 wt% of Na₂SiO₃ solution.