A low-temperature method of the β-wollastonite synthesis

• Published in: Journal of thermal analysis and calorimetry 2015-10, Vol.122 (1), p.97-104
• Main Authors: Zulumyan, Nshan, Mirgorodski, Andrei, Isahakyan, Anna, Beglaryan, Hayk, Gabrielyan, Arthur, Terzyan, Anna
• Format: Article
• Language: English
• Subjects: Analytical Chemistry; Chemistry; Chemistry and Materials Science; Inorganic Chemistry; Measurement Science and Instrumentation; Physical Chemistry; Polymer Sciences
• ISSN: 1388-6150; 1588-2926
• DOI: 10.1007/s10973-015-4752-4

The two-step procedure of β - wollastonite production includes (1) hydrothermal treatment of the suspension prepared from silicon dioxide (SiO 2 ) and calcium hydroxide [Ca(OH) 2 ] and (2) solid calcination of the Ca-containing silicate compounds produced by hydrothermal synthesis. This method suggests autoclave treatment lasting for hours which inevitably leads to a high expenditure of energy. However, the latter fact can be avoided if the amorphous silica extracted from serpentines [(Mg(Fe)) 6 [Si 4 O 10 ](OH) 8 ] is used as a raw material. Calcium hydro- and hydroxosilicates can be produced from this silica, calcium oxide (CaO) and water (H 2 O) by stirring at the temperature of 95 °C in air at ambient pressure within 2 h. Moreover, on heating these compounds begin transforming into β - wollastonite at the temperatures of 800–810 °C. The central point of the present study is to reveal those structural peculiarities of the considered silica which account for such an intriguing energy effect. The temperature-induced processes and phase transformations in the calcium hydro- and hydroxosilicates were investigated by thermal and X-ray diffraction analyses. The synthesized β - wollastonite was studied by infrared spectroscopy and electron microscopy. The data derived from our experimental investigations allow concluding that those peculiarities are the chain-like fragments of (SiO 3 ) n intrinsic in that form of silica.