Ceramics-Silikáty

Traditionally, increasing the modulus of water glass solution (soluble sodium silicate) requires increasing the silica content in batches, which is used to melt the binary Na₂O-SiO₂ glass precursor. This is only applicable for large-scale production and inevitably results in a high melting temperature and high energy consumption. Herein, porous silica powder was dissolved in a commercial water glass solution with moderate temperature heating. Thus, the modulus of the water glass solution was easily tuned from 3.06 to 3.87, providing a convenient way that is suitable for obtaining small quantities of water glass solution with a high modulus. The pH, density, viscosity and conductivity of the tuned solution were characterised in detail. The FTIR and ²⁹Si NMR spectroscopy evidenced that the porous silica dissolved in the water glass solution, but its [SiO₄] skeleton was largely preserved.