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Journal of Nuclear Materials 366 (2007) 266–271 www.elsevier.com/locate/jnucmat Characterization of nanocrystalline (Th1ÀxCex)Oy powders synthesized by co-precipitation process q
¨
O. Yildiz
Kocaeli University, Faculty of Engineering, Department of Metallurgical and Materials Engineering,
Veziroglu Yerleskesi, 41040 Kocaeli, Turkey
Received 21 July 2006; accepted 23 January 2007
Abstract
Nanocrystalline thoria–ceria (Th1ÀxCex)Oy powders in a ratio of x = 0.05À0.5 mol% were prepared by a co-precipitation process, which employs thorium and cerium nitrate as thorium and cerium source material, deionized water as solvent and ammonia gas as precipitant. Cerium was used as a simulator for plutonium and the other actinides with a +4 valency. After co-precipitation the aqueous (Th1ÀxCex)(OH)y Æ nH2O cakes had been dried at 110 °C, these powders were separately milled in acetone, carbon tetrachloride, n-dodecane, isopropanol and water before and/or after calcination at different temperatures (300–600 °C). DTA-TG, XRD, TEM and BET analyses were performed to characterize the produced powders. Characterization results revealed that the materials were not crystallized, even the temperature reached up to 600 °C. The crystallization of (Th1ÀxCex)Oy began at about 600 °C. The crystal growth took place between the temperatures 600 °C and 1200 °C. The powders have a range average crystallite sizes from 5 to 115 nm, with a specific surface area from 6 to 111 m2/g depending on the calcination temperature and Ce mol%. In this way the crystallized nano (Th1ÀxCex)O2 powder with a higher specific surface area is able to be produced to obtain the pellets in very high density. Ó 2007 Elsevier B.V. All rights reserved.
1. Introduction
The minor actinides especially Pu, Np and Am, which occur as decay products in nuclear reactors, are the most important nuclides determining the long-time risk of final disposal. Therefore after separation from the fission products the
¨
O. Yildiz
Kocaeli University, Faculty of Engineering, Department of Metallurgical and Materials Engineering,
Veziroglu Yerleskesi, 41040 Kocaeli, Turkey
Received 21 July 2006; accepted 23 January 2007
Abstract
Nanocrystalline thoria–ceria (Th1ÀxCex)Oy powders in a ratio of x = 0.05À0.5 mol% were prepared by a co-precipitation process, which employs thorium and cerium nitrate as thorium and cerium source material, deionized water as solvent and ammonia gas as precipitant. Cerium was used as a simulator for plutonium and the other actinides with a +4 valency. After co-precipitation the aqueous (Th1ÀxCex)(OH)y Æ nH2O cakes had been dried at 110 °C, these powders were separately milled in acetone, carbon tetrachloride, n-dodecane, isopropanol and water before and/or after calcination at different temperatures (300–600 °C). DTA-TG, XRD, TEM and BET analyses were performed to characterize the produced powders. Characterization results revealed that the materials were not crystallized, even the temperature reached up to 600 °C. The crystallization of (Th1ÀxCex)Oy began at about 600 °C. The crystal growth took place between the temperatures 600 °C and 1200 °C. The powders have a range average crystallite sizes from 5 to 115 nm, with a specific surface area from 6 to 111 m2/g depending on the calcination temperature and Ce mol%. In this way the crystallized nano (Th1ÀxCex)O2 powder with a higher specific surface area is able to be produced to obtain the pellets in very high density. Ó 2007 Elsevier B.V. All rights reserved.
1. Introduction
The minor actinides especially Pu, Np and Am, which occur as decay products in nuclear reactors, are the most important nuclides determining the long-time risk of final disposal. Therefore after separation from the fission products the
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