ISSN print edition: 0366-6352 ISSN electronic edition: 1336-9075 Registr. No.: MK SR 9/7 Published monthly

The System MgO—Si0₂—H₂0 at Temperatures of 150—350°C under Hydrothermal Conditions

J. Petrovič

Institute of Inorganic Chemistry, Slovak Academy of Sciences, Bratislava 9

Abstract:  The mixtures of magnesium oxide and silicon dioxide were prepared by using various forms of the silicon dioxide. The mixtures with the molar ratio M/S* between 0.3 — 2.5 were subjected to a hydrothermal process during 6, 12 and 24 hours and at temperatures of 150, 200, 250, 300 and 350°C. The samples thus obtained were investigated by means of X-ray diffraction, DTA, electron microscopy, as well as by chemical analysis. It was found that the first step reaction product was a compound with the molar ratio M/S = 1.5, regardless the molar ratio of the starting mixture. This compound formed a gel in which singular crystals could not be distinguished even by electron microscopy. It was characterized by an expressive exothermic peak of the DTA curve at 850°C and by a weak endothermic deflection in the temperature interval between 500— 700°C. With the molar ratio M/S = 1.0, the formation of serpentine and talc was found at 300°C and at higher temperatures. With the molar ratio M/S equal or smaller than 0.75 talc was formed as early as after 24 hours at 300°C or at the temperatures over 300°C, respectively.

Full paper in Portable Document Format: 237a515.pdf

Chemical Papers 23 (7) 515–520 (1969)