The Effects of Magnesium Fluoride on the Thermal Behavior of Serpentine

Abstract

Abstract By means of thermogravimetric, differential thermal, and X-ray diffraction techniques, the thermal behavior of a mixture of serpentine (heated at 730°C for 1 hr.) with 31 per cent magnesium fluoride and or mixtures of serpentine with 10, 15.5, 20, 31, 40, and 62 per cent magnesium fluoride were examined at various temperatures up to 1450°C and for various heating periods. The presence of magnesium fluoride affects the shapes of serpentine thermogravimetric and differential thermal curves, but it hardly affects the starting temperatures of the dehydroxylation of the serpentine (730°C) at all. The thermogravimetric curves showed a gradual weight loss above the dehydroxylation temperature of serpentine. In the differential thermal curves, the height reduction of two serpentine exothermic peaks (830°C and 1100°C), and the appearance of two or three endothermic peaks above 1000°C were observed; moreover, a mixture of the preheated serpentine with 31 per cent magnesium fluoride showed a new exothermic peak at 775°C. These effects of magnesium fluoride were discussed. The main heating products of serpentine in the presence of magnesium fluoride were fluorine norbergite, forsterite, magnesioferrite, and magnesium oxide, whereas those of serpentine alone were forsterite and enstatite.