Stabilization of kaolin clay slurry with sodium silicate of different silicate moduli

Abstract In the ceramic technological processes, the suspensions with high concentration of ceramic particles (> 60%) play a very important role because this let to obtain inter alia reasonable casting rates what is one of the most important steps during the ceramics manufacturing. The article shows the attempts to modify the rheological properties of concentrated ceramic slurries, based on kaolin KOC. Different alkali sodium silicate based stabilizers, i.e. sodium water glasses ((Na2SiO2)nO) of silicate moduli in the range 1.74–3.25, were used for the research. The flow curves were analyzed and the technological parameters of slurries were described. Special attention was paid to the stabilization of slurries with the use of sodium water glasses of higher silicate moduli (> 2). It was found that the best results of the stabilization of the kaolin slurry can be obtained while using sodium water glass of silicate moduli 2–2.5. Sodium water glasses of the moduli smaller than 2 precipitated free silica in the suspension and increased the alkalinity of ceramic slurry while those larger than 2.5 created independent silicate micelles, co-existing with the dispersed kaolin grains. The mechanisms appearing during the stabilization of ceramic slurry with the use of sodium water glass were ion exchange and, the so called depleted stabilization.