Nb2O5 nanoparticles obtained by microwave assisted combustion synthesis under different conditions

Abstract

The microwave assisted combustion synthesis (MACS) as a new, quick and low cost synthesis method was used for preparation of niobium pentoxide (Nb2O5) powders. The present paper investigated the effect of reactant concentrations (ammonium niobium oxalate, urea and ammonium nitrate) on the characteristics of Nb2O5 nanoparticles. Three samples were synthesized with stoichiometric ratio between the fuel and oxidant (C1), excess of oxidant (C2) and excess of fuel (C3). In all samples, Nb2O5 crystalline nanoparticles with irregular morphology were detected. The synthesis of nanoparticles with smaller diameter in the C2 and C3 samples was confirmed by greater values of band gap energy measured through UV-Visible diffuse reflectance spectroscopy (indicating quantum confinement) and by the Rietveld refinement of X-ray diffraction patterns. The results showed that the amounts of oxidant and fuel can change synthesis temperature, influencing the final characteristics of the particles, such as size and existent phases. In these cases the excess of oxidant and fuel in the C2 and C3 samples, respectively, decreases the average synthesis temperature and decelerates the particle growth and the formation of the monoclinic phase.

A review on the synthesis of metal oxide nanomaterials by microwave induced solution combustion

“…Besides, the (002) and (001) planar spacing of C2 and C3 samples were 0.19 and 0.39 nm, respectively. 35 Azizi et al group synthesized ZnO nanoparticles with mean particle size between 27 and 85 nm by different bio-fuels. The microscopic morphology of the ZnO particles synthesized using fruits, seeds and pulp as fuels were ower-like, hexagonal and block nanostructures, respectively.…”

“…Besides, the (002) and (001) planar spacing of C2 and C3 samples were 0.19 and 0.39 nm, respectively. 35 …”

“…Excessive amounts of both oxidant and fuel lowered the reaction synthesis temperature and slowed down the growth of the particles. 35 Nayebzadeh et al group used the microwave combustion method to prepare zirconia-alumina nanocatalysts and investigated the effect of fuel-to-oxidizer ratio (F/O) on their structural and chemical properties during the combustion process. The results showed that when the fuel-to-oxidizer ratio increased from 0.5 to 1.0, the combustion reaction temperature and time increased, leading to the formation of ZrO and α-Al 2 O 3 .…”