Journal
JOURNAL OF THERMAL ANALYSIS AND CALORIMETRY
Volume 114, Issue 3, Pages 1021-1027Publisher
SPRINGER
DOI: 10.1007/s10973-013-3106-3
Keywords
Chromium nitrate; Thermal decomposition; Computer modeling
Funding
- CNPq (Brazilian agency)
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Thermal decomposition of chromium nitrate nonahydrate was studied by thermal analysis, differential scanning calorimetry, infrared spectroscopy, and high temperature X-ray diffraction, so that mass losses were related to the exactly coincident endothermic effects and vibrational energy levels of the evolved gases. The thermal decomposition of chromium nitrate is a complex process, which begins with the simultaneous dehydration and concurrent condensation of 4 mol of the initial monomer Cr(NO3)(3)center dot 9H(2)O. Soon after that, the resulting product Cr4N12O36 center dot 31H(2)O gradually loses water and azeotrope HNO3 + H2O, and is transformed into tetrameric oxynitrate Cr4N4O16. At higher temperatures, the tetramer loses N2O3 and O-2 and a simultaneous oxidation of Cr(III) to Cr(IV) occurs. The resulting composition at this stage is chromium dioxide dimer Cr4O8. Finally, at 447 A degrees C the unstable dimer loses oxygen and is transformed into 2Cr(2)O(3). The models of intermediate amorphous compounds represent a reasonably good approximation to the real structures and a proper interpretation of experimental data.
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