Application of Sol-Gel Method to Investigate the Influence of P₂O₅ on the Course of Reactions in CaO-SiO₂ System

Abstract:

The effect of P₂O₅ addition on the calcium silicate phase equilibrium during the sol-gel synthesis of dicalcium silicate was investigated using Scanning electron microscope and X-ray diffraction. It is established that phosphorous oxide can form solid solution with dicalcium silicate, but its causes the formation of phosphatic calcium silicate phases such as Ca_14.92 (PO₄)_2.35(SiO₄)_5.65 and 5CaO.SiO₂.P₂O₅ also. Local analysis has demonstrated the presence of calcium phosphate epicenters containing silicon oxide and calcium silicate zones with minimum content of phosphorous oxide and intermediary areas of various phosphatic calcium silicates. The formation of two distinct islets of calcium silicate and calcium phosphate is due to the affinity between acid oxides (SiO₂, P₂O₅) and basic one (CaO) during sol-gel process. Then, the formation of various phosphatic calcium silicates result from the diffusion of P₂O₅ towards calcium silicate and that of SiO₂ towards calcium phosphate.

• Periodical: Materials Science Forum (Volume 851)
• Pages: 92-97
• DOI: https://doi.org/10.4028/www.scientific.net/MSF.851.92
• Online since: April 2016
• Authors: Jan Baraček, Martin Palou*, Jiří Másilko, Jaromír Wasserbauer, František Šoukal, Tomáš Opravil, Martin Boháč
• Keywords: Element Distribution, Mechanism of Reaction, Microstructure, Phase Diagram, Reactivity, Sol-Gel Method

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