Date of Award
Doctor of Philosophy (PhD)
Materials Science and Engineering
Dr. Fei Peng, Committee Chair
Dr. Kyle S. Brinkman
Dr. Konstantin G. Kornev
For the production of ceramic microspheres for future space travel, new methods of processing must be explored. The sol gel method proves promising for the production of uranium-based ceramic microspheres that are consistent enough in size and shape for such an application. A process for producing these microspheres has already been established, but there are avenues for improvement.
Handling of radioactive material like uranium is not always possible or warranted. As such, a non-radioactive surrogate that greatly resembles the processing of its actual radioactive counterpart. Herein this work a cerium-based surrogate is developed to closely resemble an already established process for producing uranium sol. This surrogate sol is examined to gain an understanding of how it behaves starting from the initial reagents, going forward to when it becomes a gel, and onto after it gets processed into ceramic. It is found that this process produces a homogeneous sol that displays very predictable decomposition behavior in that the point of complete decomposition from amorphous gel to ceramic powder can very easily be determined. It is also determined that the powders obtained from this gel have the potential to be converted from its initial oxide form to other ceramics, such as carbide.
Herein this work, the future capability of scaling up this established sol gel process to large scale production is considered. A new recipe is developed using a nitrate salt based on the past work which utilized an acetate salt. This is to better accommodate the reagents that will be available in an actual production setting as opposed to a laboratory one. This new sol produced from nitrate salt is examined at the initial stages of processing to determine if and how stable, homogeneous sol can be obtained when changing the initial salt used. Once this stable sol is obtained and the steps to do so are established, it is examined in much the same manner as the acetate salt-based sol before it. It is found to be more sensitive and require more careful precision in carrying out the same steps and processes used on the acetate-based sol. This new cerium nitrate sol is especially sensitive to the environment during its drying and during storage. Sol that maintained its stability long enough to be investigated, were examined initially using thermal analysis, heat treatment, and x-ray diffraction. These tests indicated that the cerium nitrate-based sol crystallizes at lower temperatures than compared to its cerium acetate-based predecessor. The sensitivity of this cerium nitrate sol, also affected its ability to be mixed with phenolic resin as easily as the cerium acetate sol. With careful control of the step of adding the resin, this was finally accomplished. The cerium nitrate sol was found to have one major flaw in that it cannot be cross-linked. This concern was investigated using Fourier Transform Infrared Spectroscopy and it was found that the organic stabilizer could be degrading in the presence of the nitrate sol. This stabilizer is essential for the cross-linking of the sol. This flaw leads to some tough considerations that must be made for future scaled up production. However, this new nitrate salt-based sol proves to still be of possible uses, even if it is not necessarily useful for the original reasons it was developed.
Alford, Matthew Brett, "Production and Characterization of Uranium Sol Gel Surrogates Produced with Cerium Acetate and Cerium Nitrate" (2020). All Dissertations. 2834.