Abstract: 29Si-NMR and TEM techniques were used to analyze the gelation process of alkaline silica sol and the effects of system pH value, SiO2 concentration and temperature on the sol stability were investigated. It was indicated by 29Si-NMR results that the interior structure of silica sol micelle was consisted of（-Si-O-Si-）, and its surface was covered by –SiOH and -Si(OH)2 groups. Results showed that the stability of alkaline silica sol increased with the increase of system pH value and decreased with the increase of SiO2 concentration and temperature. However, when temperature was below 45℃, little influence of temperature on the stability of alkaline silica sol was observed.

Key words: silica sol, binder, stability, pH value, concentration, temperature