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Interdependence of Phase Chemistry, Microstructure, and Oxygen Fugacity in Titanate Nuclear Waste Ceramics
Author(s) -
Buykx William J.,
Levins Desmond M.,
Smart Roger St. C.,
Smith Katherine L.,
Stevens Geoffry T.,
Watson Kenneth G.,
Weedon David,
White Timothy J.
Publication year - 1990
Publication title -
journal of the american ceramic society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.9
H-Index - 196
eISSN - 1551-2916
pISSN - 0002-7820
DOI - 10.1111/j.1151-2916.1990.tb05180.x
Subject(s) - microstructure , mineral redox buffer , calcination , ceramic , dissolution , materials science , durability , fugacity , titanate , plutonium , chemical engineering , oxygen , mineralogy , redox , phase (matter) , reducing atmosphere , metal , metallurgy , chemistry , composite material , nuclear chemistry , catalysis , organic chemistry , engineering
Titanate ceramic waste forms were prepared using several combinations of calcination atmosphere (N 2 , N 2 ‐3.5% H 2 , H 2 ) 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 H 2 calcination atmosphere), a satisfactory product can be produced using any of the preparative routes examined, provided the material is completely densified.