Solid phase decomposition of ammonium uranate

El-Fekey, S.A.; El-Hakim, M.N.A.; Rofail, N.H.; Khilla, M. A.

doi:10.1016/0040-6031(82)80023-3

Cited by 12 publications

(7 citation statements)

References 14 publications

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“…*'700°C' U308(0) + U308(H) ^ Washed AU ^^^^ ß-U03 ^f^o^^^po^' U308(H) 12 C/min(3)The mechanism and kinetic of thermal decomposition of AU were studied, also by EL-FEKEY et al and published elsewhere[35][36][37][38].…”

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confidence: 99%

Thermal Decomposition of Ammonium Uranate; X-Ray Study

El-Fekey¹,

Khilla

Rofail³

1984

Radiochimica Acta

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confidence: 99%

Thermal Decomposition of Ammonium Uranate; X-Ray Study

El-Fekey¹,

Khilla

Rofail³

1984

Radiochimica Acta

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“…Whereas Dharwadkar et al [16] stated that this decomposition starts above 545 ~ and terminates at about 625 ~ El-Fekey et al [14] found that it starts at 640 ~ . This variation can be attributed to the smaller crystallite size of the gelled UO 3 microspheres, and consequently to the higher specific surface area, which leads to a more active material.…”

Section: Resultsmentioning

confidence: 96%

“…It was found that dry air shifts the deflection towards higher temperatures. Other investigators [8,14,15] reported that the deflection in the region 310-450 ~ is mainly associated with the evolution of ammonia.…”

Section: Resultsmentioning

confidence: 99%

Effects of washing conditions on the thermal decomposition behaviour of gelled UO3 microspheres

Bishay

Halim

Hammad

et al. 1987

Journal of Thermal Analysis

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DTA, TG and DTG curves obtained in various atmospheres using different heating rates were used together with X-ray examinations to study the thermal decomposition mechanisms of two types of gelled UO 3 microspheres: ammonia-washed (UN) and hot water-washed (UH) microspheres.The kinetics of the thermal decompositions were studied. The specific reaction rate constant k r for the decomposition of UO 3 to U30 8 could be expressed in terms of the activation energy and the pre-exponential factor by the expressions: RTDense UO z microspheres for reactor fuels are prepared by wet chemical processes. There are several wet chemical methods that differ considerably from each other. They are generally known as "sol-gel" processes [1,2].They have in common the fact that a solution of uranium (uranyl nitrate) is dispersed into droplets and thereafter solidified by chemical precipitation on reaction. These gel particles are processed into the required ceramic microspheres, mainly by thermal treatment.To achieve good spherical kernels with high density, the precipitation must always be gel-like instead of crystalline, since only a gel structure keeps the particles spherical during drying (via uniform shrinkage) whereas a crystalline precipitate results in imperfect spherical kernels.The wet chemical processes are commonly classified into external [3] and internal [4] gelation, according to the made of precipitation.The aim of the present investigation was to study the effects of washing on the dissooiation mechanism of gelled microspheres and to study some related kinetic parameters.

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“…Also it is clear that ihsEg value of the unwashed samples when calcined at 350 or 500°C are somewhat higher than that of the washed ones. This may be clarified by returning to the thermal and X-ray diffraction analysis of the corresponding samples which proved that at SSO'C the ammonia is still retained [10]. The Xray analysis proved that the impurities in the unwashed samples when calcined at 500 °C hindered the formation ofpureß-U03 [11,12,18].…”

Section: The Energy Gap {Eg) Value Of Ammonium Uranatementioning

confidence: 98%

“…This was done on the AU and samples calcined at 350, 500, 750, 850°C [5,11,12]. The samples were also thermally analyzed [5,10,11 ]. The chemical analysis [12] was done for sample A as a representative one for the presence of NH4 ion.…”

Section: Identification Of the Samplesmentioning

confidence: 99%