Design of advanced ceramics for extreme corrosion environments
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Authors
Bryce, Keith, Christopher
Issue Date
2024-05
Type
Electronic thesis
Thesis
Thesis
Language
en_US
Keywords
Nuclear engineering
Alternative Title
Abstract
Corrosion in the case of ceramics is the destructive attack of a ceramic by chemicals within its environment, which, based on the application of the ceramic, may lead to very expensive repair and replacement costs to maintain functionality. Our work here focuses on investigating the underlying corrosion mechanisms of (1) ceramic nuclear waste form materials used for the immobilization of long-lived actinides and (2) Environmental Barrier Coatings (EBCs) used to provide jet engine components with protection from harsh, high temperature, combustion environments. Firstly, accelerated leaching tests were used to measure the chemical durability and identify the leaching mechanisms of amorphous, alpha, beta, and gamma phase yttrium disilicate. Rare earth disilicates may be formed in geological repositories from the reaction of waste actinides and smectite found in clay barriers. Hence, understanding their corrosion mechanism could aid in predicting their long-term retention of actinides ions. Next, high entropy/multicomponent titanate pyrochlores and zirconate fluorites were synthesized as potential host materials for nuclear waste. Accelerated leaching tests were used to measure their elemental release rates and investigate their leaching mechanism. Our results showed that radius size disorder significantly impacts the chemical durability of multicomponent oxide solid solutions. By implementing more controlled design parameters, improvements in the corrosion resistance of these materials may be achieved. The latter part of our work focuses on the design and testing of multicomponent rare earth phosphates as potential EBC candidates. We observed superior molten glass corrosion resistance of (Lu0.2Yb0.2Er0.2Y0.2Gd0.2)PO4 and (Lu0.2Yb0.2Er0.2Dy0.2Gd0.2)PO4 at 1300 °C compared to single component phosphates, with Scandium appearing to have a negative impact of the corrosion resistance of the multicomponent phosphates. Similarly, at 1400 °C (Lu0.2Yb0.2Er0.2Y0.2Gd0.2)PO4 and (Lu0.2Yb0.2Er0.2Dy0.2Gd0.2)PO4 samples showed the least recession of their bulk material after molten glass corrosion. Our water vapor corrosion experiments at 1400 °C revealed the improved corrosion resistance of our designed multicomponent rare earth phosphates compared to LuPO4. Where the multicomponent phosphates showed less mass loss and less porosity increase after 60 hours compared to LuPO4.
Description
May2024
School of Engineering
School of Engineering
Full Citation
Publisher
Rensselaer Polytechnic Institute, Troy, NY