Radiation Tolerance of Nanoporous Gadolinium Titanate

Full Details

Principal Investigator

Name:: Jessica Krogstad
Email:: [email protected]
Phone:: (208) 526-6918

Team Members:

Name:	Institution:	Expertise:	Status:
M Li
Y Yang
Nathan Madden	University of Illinois at Urbana-Champaign	Conduct experiments and post analysis of samples	Graduate Student

Experiment Details:

Experiment Title:: Radiation Tolerance of Nanoporous Gadolinium Titanate)
Hypothesis:: We posit that the density and type of defect sinks will effect the amorphization limit of pyrochlores class of ceramics.
Work Description:: Focus ion beam (FIB) lamellas will be created from a single-crystal gadolinium titanate that was irradiated with He ions at 200 kV to a fluence of 1x1017 ions/cm2 with create an amorphous layer. After the lamellas are made, they will be heated at 900C in vacuum to recrystallize the amorphous layer creating three layers, polycrystalline, porous (originally the He-filled bubbles) and pristine single crystal regions. The samples will be irradiated in-situ with 1 MeV Kr with in the TEM with a dose rate or approximately 6.2 x 109 ions/cm2/s to a fluence of 1x1015 ions/cm2. The amorphization kinetics will be studied in four different regimes, low temperature (100 K), room temperature (300 K), intermediate temperature (700 K), and high temperature (1100 K).

Project Summary

The method that will be employed to study the radiation tolerance of the pyrocholore sample (nanoporous gadolinium titanate) is in-situ ion irradiation with in the transmission electron microscopy. This study is enhanced by our sample’s unique microstructure. The sample has three different layers that have different microstructural features: nanograined, nanoporous, and single crystal. Where this study advances on the literature is by introducing the concept of the nanopores as an alternative to other microstructurs with a high density of defect sink. The surface of such pores are expected to act as more efficient/effective defect sinks in comparison to the dense nanograined samples. This unique microstructure has the promise of improving the suitability of pyrocholore ceramic systems for nuclear waste forms. There are many studies that focus on the microstructure-amorphization relationship, but none of them consider a nanoporous structure. Most studies consider a single microstructural characteristic e.g. just single crystal or nanograined. Because our specimen contains three unique microstructural configurations, the in-situ observations will allow us to directly compare the irradiation behavior of the pyrochlore systems under the exact same irradiation conditions. Four different temperature regimes will be explored wherein we will target unique regimes of defects mobilities and recombination rates according to current understanding of radiation enhanced diffusion. The data that will be collected during these experiments include both video and selected area electron diffraction patterns. The in-situ video collected during irradiation can be post-processed to provide detailed information on the microstructural changes, e.g. pore coarsening or grain growth, in the sample as function of irradiation dose. This is an important aspect of the experiment because microstructure changes will affect the effectiveness of the defect sinks, e.g. by increasing the distance between sinks, with in the microstructure. The selected area electron diffraction patterns for each of the unique microstructural configurations will be collected after a set dose. These images will indicate the progress towards amorphization (degree of crystallinity) in each of the areas. These observations have the potential to impact the state of the knowledge base in the nuclear ceramics and fuels communities by showing a new microstructures that can enhance the radiation tolerance of the pyrochlore systems. This enhanced radiation tolerance of the pyrochlore class of ceramics will make the nuclear waste disposal material a stronger candidate.

Relevance

The proposed research will advanced the DOE Office of Nuclear Energy mission by advancing the material development and knowledge that will impact the national strategic fuel cycle by making waste disposal safe and secure. One important aspect of the fuel cycle research and development is the successful disposal of these fuels over geological time scales. Often successful disposal has been hinged upon invariant material properties and/or structures that resist the crystalline to amorphous transition under irradiation. Recent work has indicated that in some cases amorphization can be leveraged to improved structural durability, it is still very difficult to predict the relationship between irradiation and crystallinity, especially within the technically relevant class of pyrochlore-based ceramics. This ceramic system is of interest due to isometric nature with many nuclear fuels but also with many geological formations. Moreover, pyrochlore-based ceramics have demonstrated a very broad amorphization limit—with some crystal chemistries reaching full amorphization at very low radiation doses. Considerable efforts have been invested in understanding the relationship between the amorphization limit and chemistry; however, from a practical sense, the microstructure arising from typical manufacturing processes must also be considered. This work will advance the fuel cycle by extending our current understanding of radiation-induced amorphization to include the influence of microstructural features such as grain boundaries and pores. Once understood, these factors can be used to develop processing routes that may lead to more economical solutions, e.g. via microstructural engineering of waste forms, to long term waste management.

Book / Journal Publications

"N.J. Madden, M.T. Janish, J.A. Valdez, B.P. Uberuaga, J.A. Krogstad. “Radiation Tolerance of Nanoporous Gadolinium Titanate.”" Nathan Madden, Jessica Krogstad, 0

"Measuring radiation enhanced diffusion through in situ ion radiation induced sintering of oxide nanoparticles" Jessica Krogstad, 0 Link

"Ion Irradiation Driven Amorphization-Recrystallization Cycling in Gadolinium Titanate" Nathan Madden, Jessica Krogstad, 0

Conference Publications

"Krogstad, J.A. “Indirectly tracking point defect accumulation and transport in ceramics through in situ ion irradiation an image analysis.” National Academies Condensed Matter and Materials Research Committee Workshop on Materials in Extreme Environments: New Monitoring Tools and Data-Driven Approaches. 2022 Washington, DC. " Jessica Krogstad, National Academies Condensed Matter and Materials Research Committee Workshop on Materials in Extreme Environments: New Monitoring Tools and Data-Driven Approaches [unknown]

"Krogstad, J.A. “Reading between the reflections: Order, disorder, transport and functionality.” 2022 MateriAlZ Seminar Series, Arizona State University and University of Arizona. (via Zoom)" Jessica Krogstad, [unknown]

"Krogstad, J.A., “Seemingly Homogenous Metallic Systems: Subtle Deviations and Their Role in Material Evolution and Functionality.” 2022 Oak Ridge/Knoxville Chapter of ASMI. (via Zoom)" Jessica Krogstad, [unknown]

"In situ ion irradiation of gadolinium titanate: a perspective on microstructure and memory" Nathan Madden, 2021 MS&T Conference [unknown]

"Krogstad, J.A. "Dynamic, radiation tolerant ceramics: Understanding defect mobility and microstructural evolution in ceramics subject to ion irradiation." 2021 International Conference on Advanced Ceramics and Composites. Invited Jubilee Global Diversity Award Lecture. (via Zoom)" Jessica Krogstad, [unknown]

"Krogstad, J.A. “Exploring the potential of concentrated defects: Their role in mass transport, microstructural evolution and material functionality.” 2021 Department Materials Science and Engineering, University of Maryland, MD. (via Zoom)" Jessica Krogstad, [unknown]

Radiation Tolerance of Nanoporous Gadolinium Titanate

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