Large Scale Preparation of [Beta]-CaSiO^sub 3^ Nanostructures by Solid-State Reaction in NaCl-H^sub 2^O(v) System at Lower Temperature

An environmentally friendly NaCl-H2O(v) system was developed to prepare β-CaSiO3 nanostructures from commercially available raw materials, CaCO3 and amorphous SiO2 (a-SiO2), by a one-step solid-state reaction at 575°C for 2 h. The formation of β-CaSiO3 was accelerated by NaCl-H2O(v) system. The results demonstrated that both NaCl and H2O(v) played vital roles in the formation of β-CaSiO3 nanostructures at a lower temperature. NaCl is considered to enhance the diffusivity of starting materials and the rate of solid-state reactions, and promote the crystallization at lower temperature. Water vapor can accelerate the decomposition of CaCO3, and absorbed water on the surface of solid materials can dissolve NaCl to form an aqueous ionic liquid composed of Na and Cl ions, which is similar to a hydrothermal process, and will further increase the diffusivity of components and reduce the reaction temperature.