Thermal dehydration and decomposition of nickel chloride hydrate (NiCl2·xH2O)

Abstract

The dehydration and decomposition characteristics of an undried and a partly dried sample of NiC12.xH20 have been investigated by isothermal and non-isothermal (TG and DTA) methods in static air as well as flowing nitrogen environment. While the isothermal weight loss method fails to distinguish between different steps of reaction, TG curves upto 800~ reveal as many as five steps in static air and four steps in nitrogen atmosphere. However, both methods indicate that NiCI2 is stable upto 400~ above which dehydrochlorination takes place in presence of water vapour. The intermediate products of dehydration and decomposition at different temperatures have been characterized by chemical analysis, X-ray diffraction, infrared and diffuse reflectance spectroscopy. All these methods reveal the presence of water in samples calcined at even 400~176 Thermodynamic functions for different steps of dehydration have been calculated and discussed in the light of the possible structural changes occurring in the partially dehydrated products.

Thermodynamic Efficiency of Water Vapor/Solid Chemical Sorption Heat Storage for Buildings: Theoretical Limits and Integration Considerations

“…It is worth mentioning that the latter value is very close to the enthalpy of vaporization of ice at 25 • C i.e., 52 kJ mol −1 . This conclusion is also validated by [25].…”

Investigation of interference mechanisms of nickel chloride on copper determination and of colloidal palladium as modifier in electrothermal atomic absorption spectrometry using a dual cavity platform

“…One of the explanations for that might be that, according to Majidi and colleagues [17,18], NiCl 2 is not completely converted to NiO by the thermal hydrolysis but might in part be present as anhydrous chloride, which however is not in agreement with the findings of Mishra and Kanungo [16]. The more likely explanation is that probably all the copper is present as the chloride after the drying stage, when mixed with a large excess of nickel chloride, and CuCl 2 has a melting point of 620 -C [15] and might hence be lost at pyrolysis temperatures higher than 600 -C. This partial loss of CuCl 2 in the pyrolysis stage could also explain the increase in interference at 800 -C, when copper and nickel were in separate cavities.…”

“…(1) is a gross simplification of the complex processes occurring during thermal treatment of nickel chloride hydrate, it may serve as the basis for the following discussions. Mishra and Kanungo [16], using isothermal decomposition, thermogravimetric and differential thermal analysis as well as X-ray diffraction and other spectrometric techniques, have shown that up to 400 -C nickel chloride hydrate is only loosing crystal water. Above 500 -C, however, there was an increasing loss of chlorine with the formation of the hydroxychloride (Ni(OH)Cl) or oxychloride (Ni 2 OCl 2 ), and finally of the pure oxide NiO.…”

Solid-State NaBH4 Composites as Hydrogen Generation Material: Effect of Thermal Treatment of a Catalyst Precursor on the Hydrogen Generation Rate

“…A comparison of the thermal analysis data for untreated hydrates (Figure 1) with the results of the chemical analysis of the samples after their thermal treatment ( Table 1) showed that a longer thermal treatment under isothermal conditions led to a content of water in the samples that was lower than the one obtained when they were heated at a rate of 10 • C/min. Nevertheless, the samples treated at 300 • C still contained strongly bound water, which could be removed only at temperatures above 500 • C [25,26].…”