Kinetics of foaming process of potassium silicate gel at high temperature

The potassium silicate gel with SiO2/K2O molar ratio of 5 was prepared and then sintered in the furnace. Water is the driving force for the foaming process of potassium silicate gels at high temperature. The sources of water are different at different stages of foaming, including molecular water, adsorbed water and water produced by the polymerization of silanol groups. [Display omitted] •The potassium silicate gel with a modulus of 5 foams with increasing temperature.•The maximum foaming volume at 550 °C is 33.5 times the initial volume.•The evaporation of water is the driving force of the foaming process.•The water includes molecular water, adsorbed water and hydroxyl polymerized water. The potassium silicate gel with a modulus (molar ratio SiO2/K2O) of 5 was prepared and then sintered in the furnace. As the temperature increased, the gel began to foam and its volume reached a maximum at 550 °C, close to 33.5 times the initial volume. After 550 °C, the sharp decrease in foam volume is due to the obvious densification of the gel in the glass transition temperature region. TG-DSC analysis and IR absorption spectra were employed to characterize the foaming process of the gel. The results show that water is the driving force for the foaming process of the potassium silicate gels. The sources of water are different at different stages of foaming, including molecular water, adsorbed water and water produced by the polymerization of silanol groups.