CHEMICAL INTERACTION IN MIXTURES МF + NaBr (М – K, Rb, Cs) UNDER THERMAL ACTIVATION

Abstract

The chemical interaction of equivalent amounts of MF+NaBr (M – K, Rb, Cs) was studied by differential thermal and X-ray phase analysis. A mechanism of interaction during thermal activation is proposed, including the formation of NaF+MBr products at the contact boundaries of the initial substance grains due to the diffusion of Na+ and M+ followed by contact melting of four substances that form a labile liquid phase below or equal to the melting points of low-melting triple eutectics. The labile liquid occurrence in the sample promotes rapid ionic interaction. The heating curves of equivalent amounts of two substance powdered mixtures corresponding to the unstable diagonals of triple irreversibly reciprocal systems made it possible to obtain data on the appearance of the liquid phase, the onset of exothermic reactions (the melting points of low melting eutectics), the melting temperatures of quasibinary eutectics on stable diagonals, and the melting temperatures of the mixtures. The crystallization of molten mixtures of equivalent amounts of two unstable substances of triple irreversibly reciprocal systems made it possible to determine the liquidus temperature at the point of complete conversion and the temperature of the crossing point on a stable diagonal. Therefore, the heating and cooling curves analysis provides information on the melting points of low-melting triple eutectics (570, 508 and 430 °C), the temperatures of the pass points (654, 644 and 606 °С) and the melting temperatures of the compositions corresponding to the full conversion points (798, 845 and ~840 °C) in the Na+,K+||F–,Br–, Na+,Rb+||F–,Br–, and Na+,Cs+||F–,Br– systems, respectively. Powdered substances exchange reactions can be used as low-potential exothermic compounds, as fuses, which turn off various reactors or plants when the liquid phase appears, and for the synthesis of inorganic substances.