Thermal decomposition of ferrous oxalate dihydrate studied by direct current electrical conductivity measurements

Rane, K. S.; Nikumbh, A.K.; Mukhedkar, A. J.

doi:10.1007/bf01113573

Cited by 63 publications

(57 citation statements)

References 17 publications

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“…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].…”

Section: Introductionmentioning

confidence: 91%

“…Such conclusion is based on the paramagnetic component observed in the room temperature Mössbauer spectrum along with a sextet of hematite. 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].…”

Section: Introductionmentioning

confidence: 94%

“…Thermal decomposition of ferrous oxalate dihydrate in oxidizing atmosphere represents one of the most intensively studied processes resulting in the formation of nanocrystalline particles [4][5][6][7][8][9][10][11]. However, published data differ from each other and there are many uncertainties and controversial results concerning oxidation mechanism and identification of primarily formed nanoparticles.…”

Section: Introductionmentioning

confidence: 99%

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

Zbořil

Machala

Mashlan

et al. 2004

phys. stat. sol. (c)

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Thermal decomposition of the FeC 2 O 4 .2H 2 O powder has been studied isothermally in static air conditions at minimum decomposition temperature of 180 °C using 57 Fe Mössbauer spectroscopy, XRD, HRTEM, AFM and BET surface area measurements. Dehydration and liberation of carbon oxides from powdered sample is accompanied by direct oxidation of Fe(II) to nanocrystalline Fe 2 O 3 without any indications of the stabilization of the magnetite (Fe 3 O 4 ) phase. Decomposition process is completed after two hours and as-prepared nanopowder (3-5 nm), with a large surface area of about 250 m 2 /g, is comprised of ultrafine superparamagnetic particles of γ-Fe 2 O 3 (maghemite) and α-Fe 2 O 3 (hematite) as proved by low temperature Mössbauer spectroscopy, XRD and HRTEM analysis. The simultaneous formation of both polymorphs is probably related with the non-equivalent diffusion conditions on the surface and in the bulk of oxalate particles. With increasing time, the particle size induced phase transformation of maghemite to hematite has been observed by AFM and XRD. Mössbauer spectra demonstrate that maghemite particles are formed only in superparamagnetic state (doublet), while magnetic components (sextet) in room temperature spectra can be assigned exclusively to hematite particles with size distribution produced by gradual crystallization of primary superparamagnetic nanoparticles of the same structure as well as by the phase transition of maghemite phase.

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Section: Introductionmentioning

confidence: 91%

Section: Introductionmentioning

confidence: 94%

Section: Introductionmentioning

confidence: 99%

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

Zbořil

Machala

Mashlan

et al. 2004

phys. stat. sol. (c)

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“…One of the most commonly used precursors is ferrous oxalate dihydrate (FeC 2 O 4 ·2H 2 O), which is a typical example of a readily decomposable substance. The course of ferrous oxalate thermolysis has been extensively studied in recent years, [52][53][54][55][56][57][58][59] although it is still difficult to reach an unambiguous conclusion from the published data. Differences in the published results arise due to the different experimental conditions applied, which substantially affect the final composition of the iron oxide product.…”

Section: Introductionmentioning

confidence: 99%

The Effect of Surface Area and Crystal Structure on the Catalytic Efficiency of Iron(III) Oxide Nanoparticles in Hydrogen Peroxide Decomposition

et al. 2010

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Iron(II) oxalate dihydrate has been used as a readily decomposable substance for the controlled synthesis of nanosized iron(III) oxides. The polymorphous composition, particle size and surface area of these iron oxide nanoparticles were controlled by varying the reaction temperature between 185 and 500°C. As-prepared samples were characterized by XRD, low-temperature and in-field Mössbauer spectroscopy, BET surface area and the TEM technique. They were also tested as heterogeneous catalysts in hydrogen peroxide decomposition. At the selected temperatures, the formed nanomaterials did not contain any traces of amorphous phase, which is known to considerably reduce the catalytic efficiency of iron(III) oxide catalysts. As the thickness of the sample (≈ 2 mm) was above the critical value, a temporary temperature increase ("exo effect") was observed during all quasiisothermal decompositions studied, irrespective of the reaction temperature. Increasing the reaction temperature resulted in a shift of the exo effect towards shorter times and an increased content of maghemite phase. The maghemite content decreases above 350°C as a result of a thermally in-

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“…[1][2][3][4][5][6][7][8][9][10][11][12][13][14] In recent years, many studies have been published on the thermal behavior of ferrous oxalate (dihydrate), FeC 2 O 4 ·2H 2 O. [15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30][31][32] However, much less attention has been paid to ferric oxalate, Fe 2 (C 2 O 4 ) 3 , [33][34][35][36][37][38][39][40][41] in spite of an interesting phenomenon, which is the formation of a certain amount of ferrous oxalate during its thermally induced decomposition in an inert atmosphere [35,36,38,39] . Their proportion accurately reflects actual disproportionation/synproportionation/redisproportionation processes likely encouraged by the preserved size and morphology of the initial ferric oxalate crystals and that are dependent on temperature.…”

Section: Introductionmentioning

confidence: 99%

Thermal Decomposition of Ferric Oxalate Tetrahydrate in Oxidative and Inert Atmospheres: The Role of Ferrous Oxalate as an Intermediate

2010

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The thermal decomposition of ferric oxalate tetrahydrate Fe2(C2O4)3·4H2O was studied in dynamic oxidative and inert atmospheres by using a simultaneous thermogravimetric (TG) and differential scanning calorimetric (DSC) analytical device equipped with an evolved gas analyzer (EGA). Solid‐state decomposition products formed during the decomposition were analyzed by 57Fe Mössbauer spectroscopy, in situ and ex situ X‐ray powder diffraction, and magnetic measurements. In the dynamic inert atmosphere, we observed the formation of a tiny amount of superparamagnetic iron oxide (most likely Fe3O4) together with a majority of ferrous oxalate (FeC2O4) and remains of undecomposed Fe2(C2O4)3 after the first decomposition step, which finished at 210 °C. The astonishing presence of the oxidic phase at such low temperatures is a highly probable side effect of the main reduction action of the electrons on the FeIII cations in the ferric oxalate structure, thus resulting in the creation of intermediate FeC2O4. The final product of decomposition of the FeC2O4 intermediate in a dynamic inert atmosphere is a mixture of wüstite (FexO), α‐iron (α‐Fe), and magnetite (Fe3O4). Their proportion accurately reflects actual disproportionation/synproportionation/redisproportionation processes likely encouraged by the preserved size and morphology of the initial ferric oxalate crystals and that are dependent on temperature. In the oxidative atmosphere, the decomposition proceeds in the three overlapped stages that include dehydration, the astonishing reductive formation of FeC2O4 as an intermediate, and final decarboxylation to hematite (α‐Fe2O3). The principal effect of the experimental conditions on the amount of intermediate formation of FeC2O4 in the oxidative atmosphere is also discussed and evaluated from the isothermal experiments carried out at 180 °C.

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Thermal decomposition of ferrous oxalate dihydrate studied by direct current electrical conductivity measurements

Cited by 63 publications

References 17 publications

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

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

The Effect of Surface Area and Crystal Structure on the Catalytic Efficiency of Iron(III) Oxide Nanoparticles in Hydrogen Peroxide Decomposition

Thermal Decomposition of Ferric Oxalate Tetrahydrate in Oxidative and Inert Atmospheres: The Role of Ferrous Oxalate as an Intermediate

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