Microwave-assisted citrate gel-combustion synthesis of nanocrystalline urania

A systematic investigation on the microwave-assisted citrate gel-combustion synthesis of nanocrystalline urania powders is being reported for the first time. Nanocrystalline urania powders were synthesized by microwave-assisted citrate gel-combustion method by using citric acid as a fuel and nitrate...

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Bibliographic Details
Published in:Journal of nuclear materials 2019-04, Vol.516, p.73-83
Main Authors: Hiranmayee, V., Ananthasivan, K., Maji, Dasarath, Joseph, Kitheri
Format: Article
Language:English
Subjects:
Bulk density
Citric acid
Coarsening
Combustion
Combustion synthesis
Crystallites
Crystals
Differential thermal analysis
Differential thermogravimetric analysis
High burn up structures
Infrared analysis
Infrared spectroscopy
Lattice strain
Mass spectrometry
Mass spectroscopy
Microwave-assisted gel-combustion synthesis
Nanocrystalline urania
Nanocrystals
Particle size distribution
Roasting
Size distribution
Specific surface
Spontaneous combustion
Surface area
TEM
Thermal analysis
Thermogravimetry
Transmission electron microscopy
X-ray diffraction
XCS
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Summary:A systematic investigation on the microwave-assisted citrate gel-combustion synthesis of nanocrystalline urania powders is being reported for the first time. Nanocrystalline urania powders were synthesized by microwave-assisted citrate gel-combustion method by using citric acid as a fuel and nitrate as an oxidizer. The fuel to nitrate ratio (R) was varied from 0 to 1 (0, 0.1, 0.25, 0.5, 0.75 and 1.0). It was observed that at a particular stoichiometric ratio (R = 0.1), auto ignition reaction takes place resulting in a porous product. The as-prepared powders were calcined and further reduced under flowing hydrogen. All these powders were characterized for the phases present viz., X-ray diffraction (XRD), size distribution of pores, transmission electron microscopy (TEM), specific surface area (SSA), thermogravimetry-differential thermal analysis-mass spectrometry (TG-DTA-MS) and infrared spectroscopy. It was observed that the microwave-derived powders with an R-value of 0.1 had the lowest bulk density, highest SSA and highest total pore volume. Upon calcination and reduction, the total pore volume decreased. The specific surface area of the calcined powders was the lowest and that of the as-prepared powders was the highest while that of the hydrogen-reduced powders was in between. An opposite trend was observed with the X-ray crystallite size (XCS). The microwave-derived nanocrystalline urania powders showed a lower SSA, higher XCS, higher lattice strain, higher residual carbon and lesser total pore volume than their hot plate derived counterparts. This is probably due to the influence of microwave which accelerates the reaction leading to faster grain coarsening. •Nanocrystalline urania was synthesized through the microwave-assisted citrate gel-combustion method for the first time.•The influences of citric acid to nitrate ratio on the powder characteristics of the final product was investigated.•Volume combustion was observed for the reaction mixture with fuel to oxidant ratio of 0.1.
ISSN:0022-3115
1873-4820
DOI:10.1016/j.jnucmat.2018.12.031