what is the exact role of urea and ammonium fluoride in hydrothermal synthesis
Dear Bandi, thank you for posting this very interesting technical question on RG. The mixed-metal oxides M3V2O8 can be regarded as transition metal divanatates. Thus it is not surprising that they can also be synthesized using a simple and straightforward route by reaction of NiCl2 . 6H2O and CoCl2 . 6H2O with sodium vanadate, Na3VO4 . 12H2O, in aqueous solution. In this context please have a look at the following relevant reference:
Synthesis and characterization of M3V2O8 (M = Ni or Co) based nanostructures: A new family of high performance pseudocapacitive materials
Article Synthesis and characterization of M3V2O8 (M = Ni or Co) base...
This article is freely available as public full text on RG, so that you can download it as pdf file. As you will see, the reactions were carried out at elevated temperatures under normal pressure. No hydrothermal conditions were required, and the addition of urea and ammonium fluoride was also not necessary.
In the following study, Ni3V2O8 was synthesized from stoichiometric amounts of NH4VO3 and nickel(II) acetate in water, again without the need for hydrothermal conditions or addition of other reagents:
Facile One-Step Hydrothermal Synthesis of the rGO@Ni3V2O8 Interconnected Hollow Microspheres Composite for Lithium-Ion Batteries
This paper has been published Open Access and is freely accessible from the internet (see attached pdf file).
Good luck with your research and best wishes, Frank Edelmann
Bandi Hari
A mixture of a solution of urea + ammonium fluoride is needed to obtain nanostructures on the surface of the nickel foam. They are composed of metal fluoride complexes. A solution of ammonium fluoride has slightly acidic properties, and urea makes this solution less acidic, which apparently promotes the formation of complexes.
Thank you, Professor Frank T. Edelmann, for your kind response and it will help me.
Thank you, professor,Yuri Mirgorod and the mixture of urea and ammonium fluoride solution is avoiding the oxidation of ions, right?
Bandi Hari
Urea and ammonium fluoride have no redox properties. It is a medium for obtaining complex compounds of metals with ligands of fluorine ions.
Dear Bandi Hari addition of urea and ammonium fluoride has nothing to do with avoiding oxidation of ions. Especially vanadium with remain pentavalent throughout the reaction. As you can see from the attached reference, urea and ammonium fluoride are added as some kind of "surfactants" in order to influence the morphology of the resulting crystals (i.e. plate-like, rod-like etc.):
Surfactant assisted morphological transformation of rod-like ZnCo2O4 into
hexagonal-like structures for high-performance supercapacitors
(see attachment)
I hope this answers your original question. Good luck and best wishes, Frank Edelmann
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