Interdependence of Phase Chemistry, Microstructure, and Oxygen Fugacity in Titanate Nuclear Waste Ceramics |
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| Authors: | William J. Buykx Desmond M. Levins Roger St. C. Smart Katherine L. Smith Geoffry T. Stevens Kenneth G. Watson David Weedon Timothy J. White |
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| Affiliation: | Advanced Materials Program, Australian Nuclear Science and Technology Organization, Menai, New South Wales, 2234, Australia.;School of Chemical Technology, South Australian Institute of Technology, Ingle Farm, South Australia, 5098, Australia.;Julius Kruttschnitt Mineral Research Centre, University of Queensland, St. Lucia, Queensland, 4067, Australia.;National Advanced Materials Analytical Centre, School of Physics, The University of Melbourne, Parkville, Victoria, 3052, Australia |
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| Abstract: | Titanate ceramic waste forms were prepared using several combinations of calcination atmosphere (N2, N2-3.5% H2, H2) and metallic redox buffers (Ni, Fe, Ti, Al) to examine the dependence of microstructure and durability upon oxygen activity. It was found that the microstructures and phase assemblages were mostly insensitive to the fabrication method, although in detail systematic changes were recognized. The correlation of aqueous durability with oxygen fugacity was not straightforward, because of density variations in the hot-pressed ceramics. These fluctuations in density dominated the dissolution characteristics of the waste forms and sometimes obscured the more subtle changes associated with redox potential. It is concluded that although the best durability is achieved at lower fugacities (i.e., Ti metal buffer and H2 calcination atmosphere), a satisfactory product can be produced using any of the preparative routes examined, provided the material is completely densified. |
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| Keywords: | titanates microstructure phases nuclear waste waste disposal |
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