Hydrothermal synthesis of micro-porous spherical particles of calcium silicate

Micro-porous spherical particles of calcium silicate with more than 90% of porosity, consisting of fibrous xonotlite crystals, can be synthesized through dynamic hydrothermal process. The effects of processing parameters on formation of spherical particles are discussed in this paper. It is important to keep the mole ratio of CaO/SiO in reactants equal to 1, otherwise, non-xonotlite phase will appear in the product. Stirring during hydrothermal process is a key point to formation of spherical particles. A tangential shearing moment exerts on the surface of C-S-H gel particle by stirring. The foil-like gel particles are rolled into spherical under the shearing moment. Addition of mineralizer in hydrothermal reactants can reduces the absolute value of ζ potential of gel particles, promoting formation of large coagulated particles. The existence of mineralizer raises the formation temperature of xonotlite from C-S-H gel particles. Thus, there is sufficient time for forming large spherical particles.