Study of thermal decomposition of FeC204·2H20

Structural, magnetic and size transformations induced by isothermal treatment of ferrous oxalate dihydrate in static air conditions

“…2b). Generally, any of XRD patterns or Mössbauer spectra did not show the formation of ferric oxalate or magnetite as possible primary oxidation products, in contrary to some literature data [4,5,6,9]. The simultaneous presence of two Fe 2 O 3 polymorphs in the initial conversion stage can be explained by the non-equivalent diffusion conditions on the surface and in the bulk of oxalate particles, although the possible formation of hematite by the isochemical structural transformation of maghemite cannot be excluded.…”

“…Using XRD, many authors have identified maghemite and hematite in the mixture of reaction products after isothermal heating at different temperatures (200-350 °C) with a general agreement that α-Fe 2 O 3 is formed by thermally induced structural transformation of γ-Fe 2 O 3 [5][6][7]11]. Despite the results of dynamic TG analyses (no weight increase), powdered character of samples and static air atmosphere representing good oxidation conditions, two-step formation of maghemite is expected via Fe 3 O 4 , which is considered as the primary oxidation product [5,6,9]. Unfortunately, such surprising conclusion is not supported by experimental data at all [6] or results from XRD analyses [5,9], where distinguishing between Fe 3 O 4 and γ-Fe 2 O 3 spinel structures is problematic, especially in the nanocrystalline state.…”

“…Despite the results of dynamic TG analyses (no weight increase), powdered character of samples and static air atmosphere representing good oxidation conditions, two-step formation of maghemite is expected via Fe 3 O 4 , which is considered as the primary oxidation product [5,6,9]. Unfortunately, such surprising conclusion is not supported by experimental data at all [6] or results from XRD analyses [5,9], where distinguishing between Fe 3 O 4 and γ-Fe 2 O 3 spinel structures is problematic, especially in the nanocrystalline state. On the other hand, formation of magnetite in static air can be expected in the case of the pressed samples as suggested by Rane et al on the basis of electrical conductivity and magnetization measurements [11].…”

Thermal behaviour of iron(ii) oxalate dihydrate in the atmosphere of its conversion gases

“…[1][2][3][4][5][6][7][8][9][10][11][12][13][14][15] In recent years many studies have been published on the thermal behaviour of ferrous oxalate dihydrate (FeC 2 O 4 ?2H 2 O) in various reaction atmospheres. [16][17][18][19][20][21][22][23][24][25][26][27][28][29][30] Depending on the experimental conditions, a diversified scale of reactions resulting in solid products varying in composition and valence state of iron has been reported. From the point of view of the basic research, the mechanism of these solid-state reactions is the key experimental issue as the published data are very controversial.…”

“…It is generally agreed that the transformation process occurs in two steps including dehydration followed immediately by oxidative decomposition resulting in a-Fe 2 O 3 (hematite) as the final decomposition product. [16][17][18][19][20][21] There are however some uncertainties concerning possible intermediates. Thus, FeO [16][17][18] and Fe 3 O 4 19 were suggested to be the primary decomposition products in oxygen or dry air, while c-Fe 2 O 3 (maghemite) was stabilized when a significant amount of water vapour was present in the reaction atmosphere.…”