Experimental studies of the quasi-binary system Na2SO4–NiSO4 by differential thermal analysis, calorimetry and X-ray diffraction

Abstract

This work is dedicated to experimental studies of the quasi-binary sub-system Na2SO4–NiSO4 with Differential Thermal Analysis (DTA) with simultaneous Thermal Gravimetry (TG), Differential Scanning Calorimetry (DSC), and X-ray Diffraction (XRD) to obtain the transition temperatures, the phase compositions, and thermodynamic data of Na2Ni(SO4)2, (Fp: 982 ± 3 K, ΔHfus = 59 ± 3 kJ mol−1), compound in this sulfate system. A compound Na6Ni(SO4)4) with the decomposition temperature 682 ± 3 K was confirmed. The lack in the data of the NiSO4-rich region was clarified. The entire composition range could be measured and the structure change at 1243 ± 3 K (“dkostruct”) that enables to describes corrosion processes on Ni-containing alloys in a sulphatic-rich environmental, as well as the melting point of NiSO4 at 1483 ± 3 K could be confirmed in this work. A new and complete phase diagram was determined.