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Synthesis and Characterization of Co-Cs-Nd-Sr-Doped Perovskite-Rutile-Type Structure

Smolinski T., Zhao L., Rogowski M., Wawszczak D., Olczak T., Brykala M.

Archives of Metallurgy and Materials

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2020

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Vol. 65, iss. 4

1417--1423

EN

The perovskite type matrix is considered as solidification material for high-level radioactive waste. In this work the perovskite-rutile-type matrix doped by Co, Cs, Nd and Sr which simulate nuclear waste was prepared by sol-gel route. The material was characterized by several methods such as: X-ray diffraction, energy dispersive X-ray spectrometer, and particle induced X-ray emission combined with Rutherford backscattering spectrometry. The analyzes confirmed chemical composition Co-Cs-Nd-Sr-doped perovskite-rutile-type structure. A virtual model of the pellet`s structure was created non-destructively by Roentgen computed micro-tomography. The leaching tests confirmed high chemical resistance of the matrix.

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Microspheres and Pellets of UO2 Prepared Via ADU by Complex Sol-Gel Process and ICHTJ Process

Brykala M., Rogowski M., Wawszczak D., Olczak T., Smolinski T.

Archives of Metallurgy and Materials

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2020

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Vol. 65, iss. 4

1397--1404

EN

This study is devoted to synthesis and characterization of uranium dioxide microspheres (Ø < 100 μm) and pellets by application of powder-free process called the Complex Sol-Gel Process. The precursors of prepared sols were ascorbic acid solution with dissolved a freshly precipitated ammonium diuranate. The microspheres of uranyl-ascorbate gel were obtained using the ICHTJ Process. The pellets were formed by pressing and sintering of uranium dioxide powder. Studies allowed determining an optimal heat treatment of calcination, reduction and sintering processes at temperatures of 700°C, 900°C and 1300°C, respectively. The main parameters which play a key role in the process of synthesis method and features of the pellets and microspheres of uranium dioxide are described in this article.

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Carbonization of solid uranyl-ascorbate gel as an indirect step of uranium carbide synthesis

Brykala M., Rogowski M., Olczak T.

Nukleonika

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2015

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Vol. 60, No. 4, part 2

921--925

EN

The studies of the synthesis of uranium carbide from uranyl-ascorbate gels using the complex sol-gel process (CSGP) have been carried out. The synthesis of uranyl-ascorbate mixture as liquid sol from uranium trioxide and ascorbic acid and solid gel by extraction of water from sol were carefully examined. Ascorbic acid was used as a complexing agent in complex sol-gel process and as a carbon source. The crucial step to obtain final uranium carbides from the aforementioned substrates is the carbonization process. The thermal behavior of ascorbic acid and uranyl-ascorbate gels in a nitrogen atmosphere in the temperature range of 25–900°C were investigated using TG-DTG. Furthermore, the products of the carbonization of uranyl-ascorbate gels in nitrogen, argon and vacuum atmosphere were identifi ed by X-ray diffraction. TG-DTG was used also as a method for determining of carbon residues in the samples.

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Application of Pt/Al2O3 catalysts produced by sol-gel process to uranyl ion reduction

Deptuła A., Łada W., Olczak T., Chmielewski A.

Nukleonika

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2006

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Vol. 51,suppl.1

79-82

EN

Various kinds of active alumina supports were obtained by the Institute of Nuclear Chemistry and Technology (INCT) sol-gel process in the following steps: (1) preparation of alumina sols by extraction of nitrates with Primene JMT from aluminium nitrate solution; (2) gelation to spherical particles (with diameter < 100 žm) by extraction of water from sol emulsion in 2-ethyl-1-hexanol; (3) sometimes conversion of NO3 - stabilized gel to OH- form by reaction with ammonia; (4) calcination of gels to ?-Al2O3 with specific surface area > 100 m2/g at 500°C. The powders were then impregnated with chloroplatinic acid and recalcined at 500°C. Catalysts were also prepared by direct gelation of alumina sol containing hydroplatinic acid followed by steps (3) and (4). Pt/Al2O3 catalysts were used for the reduction of 1M UO2(NO3)2 - 0.5M HCOOH solution with hydrogen at atmospheric pressure. The course of the reduction was controlled analytically and by measuring the U(VI)/U(IV) redox potential. It was concluded that the catalysts obtained by impregnation of the supports prepared from nitrate stabilized gels exhibit the best activity and stability.

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Preparation of lithium titanate by sol-gel method

Deptuła A., Łada W., Olczak T., Sartowska B., Chmielewski A., Alvani C., Casadio S.

Nukleonika

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2001

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Vol. 46, nr 3

95-100

EN

Medium sized spherical particles of Li2TiO3 (with diameters below 100 mi m) can be prepared from peroxy lithium titanate solution (stabilized with citric acid) by a modified INCT variant of the sol-gel process. The process consists of the following main steps: (I) formation of aqueous phase emulsion in 2-ethylhexanol-1 containing the surfactants 1v/o SPAN-80 and 1v/o Ethomen S-15 (EH); (II) gelation of emulsion drops by extraction of water with partially dehydrated EH; (III) filtration and washing with carbon tetrachloride or acetone; (IV) non-destructive thermal treatment. The tritium release from sol-gel process preparation of Li2TiO3 micro-spheres was found very close to that observed for other traditional material however, the new process is more efficient than other processes because of the morphology of the sintered specimens.