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Abstract  

This work studied a way to reclaim uranium from contaminated UO2 oxide scraps as a sinterable UO2 powder for UO2 fuel pellet fabrication, which included a dissolution of the uranium oxide scraps in a carbonate solution with hydrogen peroxide and a UO4 precipitation step. Dissolution characteristics of reduced and oxidized uranium oxides were evaluated in a carbonate solution with hydrogen peroxide, and the UO4 precipitation were confirmed by acidification of uranyl peroxo–carbonate complex solution. An agglomerated UO4 powder obtained by the dissolution and precipitation of uranium in the carbonate solution could not be pulverized into fine UO2 powder by the OREOX process, because of submicron-sized individual UO4 particles forming the agglomerated UO4 precipitate. The UO2 powder prepared from the UO4 precipitate could meet the UO2 powder specifications for UO2 fuel pellet fabrication by a series of steps such as dehydration of UO4 precipitate, reduction, and milling. The sinterability of the reclaimed UO2 powder for fuel pellet fabrication was improved by adding virgin UO2 powder in the reclaimed UO2 powder. A process to reclaim the contaminated uranium scraps as UO2 fuel powder using a carbonate solution was finally suggested.

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Abstract  

A complex oxalate precursor, CaCu3(TiO)4(C2O4)8·9H2O, (CCT-OX), was synthesized and the precipitate that obtained was confirmed to be monophasic by the wet chemical analyses, X-ray diffraction, FTIR absorption and TG/DTA analyses. The thermal decomposition of this oxalate precursor led to the formation of phase-pure calcium copper titanate, CaCu3Ti4O12, (CCTO) at ≥680°C. The bright-field TEM micrographs revealed that the size of the as synthesized crystallites to be in the 30–80 nm range. The powders so obtained had excellent sinterability resulting in high density ceramics which exhibited giant dielectric constants upto 40000 (1 kHz) at 25°C, accompanied by low dielectric losses, <0.07.

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Abstract  

Calcination conditions of the precursor powders, i.e. temperature, type of atmosphere and duration, were determined with a view to obtain superconducting powders with the most advantageous physico-chemical properties. Investigated were powders in the Y−Ba−Cu−O system prepared by the sol-gel method. Thermogravimetric examinations of the powders have revealed that the decomposition kinetics of BaCO3 determines the formation rate of the superconducting YBa2Cu3O7−x (‘123’) phase. It follows from the decomposition kinetics of BaCO3 that the process is the most intensive in argon, whereas in static air and oxygen it is the slowest. The phase composition analysis (XRD) and low-temperature magnetic susceptibility measurements of the calcinated powders, confirm the above mentioned changes in the decomposition kinetics. The reaction of barium carbonate can be completed if the calcination process is conducted at the temperature of 850°C for 25 h, yielding easily sinterable powders for obtaining single-phase superconducting bulk samples with advantageous functional parameters.

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influence of the zirconia content: in the sinterability, some mechanical properties and thermal behavior, particularly to study the effects of the zirconia martensitic transformation from m–t and from t–m. The porosity, mean grain size, and distribution

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, Redford , KC . Physical properties of some thoria powders and their influence on sinterability . J Nucl Mater . 1974 ; 52 : 241 10.1016/0022-3115(74)90171-8 . 3. Das , RN

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at low temperature employing microwave heating technique [ 9 – 12 ]. The compounds synthesized at low temperature have certain advantages like high surface area, small particle size, good sinterability and they are more reactive. This article reports

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Journal of Thermal Analysis and Calorimetry
Authors: Adney Luís A. da Silva, Guilherme G. G. Castro, and Mariana M. V. M. Souza

, Lal , R 2006 Sinterable La 0.8 Sr 0.2 CrO 3 and La 0.7 Ca 0.3 CrO 3 powders by sucrose combustion synthesis . J Mater Sci 41 : 6300 – 6304 10.1007/s10853-006-0336-9 . 32. Worayingyong

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Journal of Thermal Analysis and Calorimetry
Authors: Abdelhamid Harabi, Djamel Belamri, Noureddine Karboua, and Fatima-Zohra Mezahi

on the stability and sinterability of HA. Experimental procedure Material The HA powder was produced by calcination of bovine bone at 800 °C for 4 h followed by wet ball milling. The average particle

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during calcination at 1300 °C. The results of the microscopic analyses and their interpretation are corroborated by XRD results ( Fig. 1 a, d). The synthesized ferrite powder exhibited high sinterability; the density of the Mn–Zn ferrite sintered at 1300

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toughness, flexural strength, sinterability, and impact resistance, which renders the Al 2 O 3 − reinforced diboride composites a promising candidate for a variety of applications including cutting tools, wear-resistant parts, heat exchangers, and high

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