Thermal decomposition of ammonium fluoroferrates (NH4)xFeF2x (2≤x≤3)

Laptash, N. M.; Polyshchuk, S. A.

doi:10.1007/bf02547272

Cited by 7 publications

(9 citation statements)

References 3 publications

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“…On the basis of the XRD results obtained investigating as-grown anodic films in glycerol solutions, it can be concluded that, except for Fe, Cr, and Ni fluorides, the formation of complex ammonium fluorometallates also takes place. However, in the solutions containing additional water, (NH 4 ) 3 CrF 6 and (NH 4 ) 3 FeF 6 tend to dissolve owing to their higher solubility in aqueous environments. − …”

Section: Results and Discussionmentioning

confidence: 99%

Fabrication and Characterization of Anodic Films onto the Type-304 Stainless Steel in Glycerol Electrolyte

et al. 2013

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Porous films without periodic structuration were formed by direct current anodizing the surface of type-304 stainless steel in glycerol solution containing NH4F and H2O at elevated temperatures. Formed in the solutions containing both NH4F and H2O at the constant voltage mode of up to 50 V, these films are thin (∼1.0–1.2 μm) and yellow, whereas those formed at higher voltages, ca. 60–70 V, are thicker (up to 15 μm) and greenish. Note that these porous films are composed of both amorphous and crystalline species. X-ray diffraction (XRD), energy-dispersive X-ray (EDX), and X-ray photoemission spectroscopy (XPS) investigations and the detailed chemical analysis of incorporated elements revealed the complex nature of these films varied depending on the anodizing solution composition and voltage value applied. On the basis of the obtained data, the possible mechanism of formation of the glycerol anodic films on the SS304 substrate is presented. Compositional and structural transitions of as-grown films to material composed of crystalline Cr1.3Fe0.7O3 and spinel-type species were achieved via calcination procedure of anodized samples in air at 700 °C.

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Section: Results and Discussionmentioning

confidence: 99%

Fabrication and Characterization of Anodic Films onto the Type-304 Stainless Steel in Glycerol Electrolyte

et al. 2013

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“…Laptash and Polyshchuk had reported the reaction mechanism of Fe 2 O 3 and NH 4 HF 2 . 33 The two reactants generate (NH 4 ) 3 FeF 6 at 200 °C, which thermally decomposes to NH 4 FeF 4 at 280 °C and finally to FeF 3 at 410 °C. This phenomenon is similar to the fluorination results as a function of fluorination time (t) in our experiment.…”

Section: Resultsmentioning

confidence: 99%

“…Notably, there was no fluoride ZrF 4 in all groups, which was caused by the insufficient amount of the fluorinating agent NH 4 F with the F/Zr ratio = 2.0. Laptash and Polyshchuk had reported the reaction mechanism of Fe 2 O 3 and NH 4 HF 2 . The two reactants generate (NH 4 ) 3 FeF 6 at 200 °C, which thermally decomposes to NH 4 FeF 4 at 280 °C and finally to FeF 3 at 410 °C.…”

Section: Resultsmentioning

confidence: 99%

Controllable Syntheses, Crystal Structure Evolution, and Photoluminescence of Polymorphic Zirconium Oxyfluorides

Wen

Liu

et al. 2021

Inorg. Chem.

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Precise synthesis of polymorphic phases with similar components but distinct crystal structures is one of the key problems in inorganic chemistry. In this work, we report a fluorination method adopting ZrO2 as the starting material and NH4F as the fluoridation agent that can afford multiphases in the Zr–O–F system, including Zr7O9F10, Zr3O2F8, ZrO0.46F3.08, ZrO0.33F3.33, β-ZrF4, NH4Zr2F9, and NH4ZrF5. A preliminary phase formation diagram was established as a function of the fluorination temperature (T), reaction time (t), and F/Zr ratio after systematic optimization of the preparation conditions. Among the as-obtained phases, the detailed crystal structures of Zr7O9F10 and ZrO0.33F3.33 were refined based on the powder X-ray diffraction patterns. As the F/O ratio increases, the crystal structures of Zr–O–F phases transform gradually from an anion-deficient α-UO3-related structure of Zr7O9F10 to an anion-excess ReO3-related structure of ZrO0.33F3.33. At last, we also prepared Ti-doped ZrO2, Zr7O9F10, ZrO0.46F3.08, and ZrO0.33F3.33 to study the host-lattice-dependent photoluminescence properties of zirconium oxyfluorides. The four materials show distinct photoluminescence in the UV and visible regions due to different local coordination environments of Zr/Ti. This work demonstrates the low-temperature fluorination method as an efficient route to phase-selective polymorphic metal oxyfluorides, which can be employed in further structure–property relationship studies.

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“…FeF₃ can also be prepared via thermal process using anhydrous HF or F₂ gas at high temperature in special corrosion-resistant equipment (Johnson., 1981). NH₄F and NH₄HF₂ are recognized as cheaper and versatile fluorinating agent used at low temperatures (<240°C) (Andreev, 2008;Claux et al, 2016;Gordienko et al, 2017;Juneja et al, 1995;Laptash and Maslennikova, 2012;Laptash and Polyshchuk, 1995;Mukherjee et al, 2011;Pourroy and Poix, 1989;Sophronov et al, 2016). However, excess NH₄F should be added in order to produce oxygen-free fluorides due to the highly hygroscopic nature of NH₄F (Mukherjee et al, 2011;Pourroy and Poix, 1989;Sophronov et al, 2016).…”

Section: Introductionmentioning

confidence: 99%

“…The melting and boiling point of NH₄HF₂ are 126.8°C and 238.8°C, respectively. It is known that that NH₄HF₂ can react with Fe₂O₃ or FeTiO₃ (Andreev, 2008;Gordienko et al, 2017;Juneja et al, 1995;Laptash and Maslennikova, 2012;Laptash and Polyshchuk, 1995) below 230°C to form (NH₄)₃FeF₆ and/or NH₄FeF₃ according to follow reaction:…”

Section: Introductionmentioning

confidence: 99%

Studies on fluorination of Fe3O4 (magnetite) by NH4HF2

Zhang¹,

Zhou²,

Wang³

et al. 2023

J. S. Afr. Inst. Min. Metall.

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Fluorination of magnetite (Fe3O4) by NH4HF2 was investigated using simultaneous thermogravimetry and differential thermal analysis (TG-DTA), and observing the morphology and phase changes using scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDS) and X-ray diffractometry (XRD). The results indicate that fluorination with the involvement of oxygen begins at room temperature, peaks at 1784ºC, and is completed at 200ºC with the formation of only (NH4)3FeF6. On heating, (NH4)3FeF6 gradually releases NH4F by the formation of NH4FeF4 at 259ºC, then (NH4)0.l8FeF3 at 327ºC, and finally FeF3 with minor FeF2 at 400ºC due to the partial reduction of Fe (III) to Fe (II). At 550ºC, FeF3 is oxidized to FeOF/Fe2O3.

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Thermal decomposition of ammonium fluoroferrates (NH4)xFeF2x (2≤x≤3)

Cited by 7 publications

References 3 publications

Fabrication and Characterization of Anodic Films onto the Type-304 Stainless Steel in Glycerol Electrolyte

Fabrication and Characterization of Anodic Films onto the Type-304 Stainless Steel in Glycerol Electrolyte

Controllable Syntheses, Crystal Structure Evolution, and Photoluminescence of Polymorphic Zirconium Oxyfluorides

Studies on fluorination of Fe3O4 (magnetite) by NH4HF2

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