Effect of Transition Metal Chlorides on the Formation of β-CaSiO₃ by the TW Method

Abstract

Wollastonite (β-CaSiO₃) was synthesized by the TW method from the mixed solutions of Si(C₂H₅)₄ and CaC1₂ with both the small amount of 2M-HC1 as catalyst and separately the desired quantity of each aqueous solution made up of additives such as MnC1₂, FeC1₃, NiC1₂ or CuC1₂. In the case of the sample obtained without the additives, pure β-CaSi0₃ in a single phase was not obtained at any heat treatment temperature of this study. The acceleration effects of additives on the formation of β-CaSiO₃ were arranged in the order of MnC1₂ > NiC1₂ > CuC1₂ > FeC1₃ at the temperature of 1100°C. MnC1₂ was most effective for the acceleration of β-CaSiO₃ formation among the additives, and in the case of each sample obtained with the addition of MnCl₂ with 7.8 × 10^-3 mole or 9.3 × 10^-3 mole, pure β-CaSiO₃ in single phase was obtained at 1100°C. It was thought that β-CaSiO₃ was formed by reaction of β-Cristobalite with Ca₃Si₂O₇, simultaneously according to the phase transition from α-CaSiO₃ to β-CaSiO₃.