Zur thermischen zersetzung der 3d-übergangsmetalloxalate

Thermal Decomposition of Nickel Oxalate Dihydrate: A Detailed XPS Insight

“…The emergence of NiO during Ni oxalate decomposition under an inert atmosphere (N 2 ) may be considered 16 as an indication of the oxide being the primary product (formed according to NiC 2 O 4 → NiO + CO + CO 2 ), which could partly be reduced to metal by reaction with concurrently released CO (NiO + CO → Ni + CO 2 ). However, since the formation of Ni oxide from NiC 2 O 4 in an oxygen-free environment is thermodynamically unfavorable, 18,25,48 we suggest that at temperatures higher than 410 °C, freshly produced metal, due to its high surface activity, can be oxidized with evolved CO 2 according to Ni + CO 2 → NiO + CO. 8,11,24 Note that the incomplete dehydration may also contribute to the formation of surface NiO according to Ni + H 2 O gas ↔ NiO + H 2 . 28 The occurrence of carbon in the final product was previously reported for the decomposition in an inert atmosphere of rare earth oxalates, 48 cobalt oxalate, 49 and nickel oxalate.…”

“…In pure CO 2 , thermal decomposition yielded mainly Ni or Ni + NiO and NiO . For decomposition in vacuum, the formation of metallic Ni was reported …”

“…12,14−16 The effect of four different atmospheres on thermal decomposition of Ni oxalate was studied in detail. 16,17 In most of the studies, the thermal decomposition of Ni oxalate was performed in N 2 6,8,11,12,14−23 or in air; 10,12−14,16−21,24−27 besides, other environments such as vacuum, 9,11,17,24 Ar, 22,28 He, 26 CO 2 , 11,16,25 H 2 , 16,17,28 O 2 , 23 N 2 + CH 4 , 6 and self-generated atmosphere 29 were also used. For all of these studies, the dehydration step was found to be endothermic.…”

“…16 For decomposition in vacuum, the formation of metallic Ni was reported. 24 Thermogravimetry (TG)/derivative thermogravimetry, differential thermal analysis (DTA), and differential scanning calorimetry are the techniques most commonly used for studying the process of dehydration-decomposition of metal oxalates. Direct current conductivity measurements were also used 21 for monitoring the decomposition process of NiC 2 O 4 • 2H 2 O.…”

“…It was found that the temperatures and activation energies of dehydration and decomposition were dependent on the heating rate, ,,− mass of the sample, and temperature of preparation of Ni oxalate . Typically, when increasing the heating rate, dehydration and decomposition occurred at higher temperatures whatever the environmental atmosphere. ,− The effect of four different atmospheres on thermal decomposition of Ni oxalate was studied in detail. , In most of the studies, the thermal decomposition of Ni oxalate was performed in N 2 ,,,,− or in air; ,− ,− ,− besides, other environments such as vacuum, ,,, Ar, , He, CO 2 , ,, H 2 , ,, O 2 , N 2 + CH 4 , and self-generated atmosphere were also used. For all of these studies, the dehydration step was found to be endothermic.…”