The influence of Zn containing components on the synthesis of Z-phase

Abstract

The influence of Zn containing compounds on the formation of Z-phase during hydrothermal treatment at 200°C temperature was investigated. The molar ratio of primary mixtures was CaO/(SiO2 + ZnO) = 0.55 and ZnO/(SiO2 + ZnO) = 0; 0.025 (it corresponds 2.27 % ZnO in the mixture). Compounds containing Zn2+ ions were used: soluble in water Zn(NO3)2•6H2O and insoluble in water 5ZnO•2CO2•4H2O. It was determined that the formation of Z-phase increases approximately twice due to influence of Zn2+ ions from the mixture. The high crystalline compound formed after 4 hours, while in the mixtures without additives - after 8 h of hydrothermal synthesis at 200°C temperature. Moreover, Zn2+ ions penetrate into Z-phase crystal lattice by exchanging Ca2+ ions. It was observed that insoluble 5ZnO•2CO2•4H2O additive has no essential influence on the begining of Z-phase formation, but it promotes Z-phase recrystallization into gyrolite. The products were characterized using X-ray powder diffraction, simultaneous thermal analysis, FT-IR spectra and scanning electron microscopy.

Keywords

• calcium silicate hidrate (CSH)
• Z-phase
• zinc
• hydrothermal treatment