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Wollastonite from Hydrothermally Synthesized Calcium Hydrometasilicate Obtained from Various Modifications of Silica
Author(s) -
Grigoryan K.,
Harutyunyan G.,
Grigoryan G.
Publication year - 2006
Publication title -
journal of the american ceramic society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.9
H-Index - 196
eISSN - 1551-2916
pISSN - 0002-7820
DOI - 10.1111/j.1551-2916.2005.00689.x
Subject(s) - wollastonite , tridymite , cristobalite , quartz , tobermorite , chemical engineering , mineralogy , calcium , phase (matter) , calcium silicate , chemistry , materials science , cement , raw material , metallurgy , organic chemistry , composite material , engineering
A hydrothermally CaO–SiO 2 –H 2 O system was investigated at 150°–200°C, 2.5 h (CaO:SiO 2 =0.95) using various modifications of SiO 2 in the presence of a mineralizer. Synthetic (stabilized) γ‐tridymite is the most reactive among SiO 2 modifications. In the reaction mixture, the optimal concentration of the mineralizer (KOH) is 2% (versus the solid phase). The binding degree of CaO with SiO 2 practically is 100% at 150°C. It is impossible to synthesize CSH free of C 2 SH on the basis of β‐cristobalite and β‐quartz under the investigation conditions without the use of mineralizer. The calorimetric effects as well as heat of de‐hydration of hydrosilicates were determined during their transformation into wollastonite. The entropy change at the peaks has been calculated.