The Thermal Decomposition of Ammonium Meta-Vanadate under Restricted Flow Conditions

Abstract

The products obtained during the thermal decomposition of ammonium meta-vanadate depend on the configuration of the container, the mass of the sample, the heating rate and the composition of the carrier gas. The decomposition in an uncapped container produced (NH 4 ) 2 V 4 O 11 , NH 4 V 3 O 8 , and V 2 O 5 as the apparent stable products while the products in a capped container were NH 4 V 3 O 8 , and V 2 O x where x was between 4 and 5. These differences are attributed to the different amounts of the evolved gases in the cell. EGA-FTIR clearly established that the reduced final product in the capped cell resulted from a reaction between NH 3 and the V 2 O 5 formed during the decomposition. A pre-equilibrium kinetics model where the rate of the reverse reaction depends on the partial pressure of the gaseous products in the cell could explain the different reaction intermediates. This model provides a possible explanation for the different apparent activation energies that have been reported for the thermal decomposition of other compounds where a reversible step could occur in the decomposition mechanism.

Thermolysis-Driven Growth of Vanadium Oxide Nanostructures Revealed by In Situ Transmission Electron Microscopy: Implications for Battery Applications

“…The reaction is much more complicated than shown in the above equation where different intermediate products at intermediate temperatures can be obtained, but these are mostly very poorly crystalline or even amorphous. − This suggests that thermal decomposition of the AMV precursor leads to the growth of the only pure crystalline structure, V 2 O 5 . This is one of the easiest and less complex methods to grow crystalline V 2 O 5 structures, which can be used for various applications.…”

“…A single solid-state precursor, ammonium metavanadate (NH 4 VO 3 , abbreviated as AMV), was heated in the in situ TEM experiments to observe and investigate the growth of crystalline vanadium oxide structures, V 2 O 5 and VO 2 , using a dedicated in situ heating holder. The previous research reported on the thermal decomposition of AMV in different gaseous environments (vacuum, argon, nitrogen, and air) to produce V 2 O 5 , which can be shown with the following simple equation: − 2 normalN normalH 4 normalV normalO 3 ( s ) → normalΔ 2 normalN normalH 3 ( g ) false↑ prefix+ normalH 2 normalO ( g ) false↑ prefix+ normalV 2 normalO 5 ( s ) ( 400 − 500 ° C ) …”

“…Thermolysis of ammonium metavanadate (AMV), an amorphous single solid-state precursor, produces crystalline V 2 O 5 structures. − Decomposing AMV precursor is a quite straightforward and feasible method to produce V 2 O 5 nanostructures with no complex requirements or conditions. This unique and simple synthesis method has not been explored significantly compared to the conventional routes.…”