Chemistry Weekly Seminar - Farah Mahmood, PhD Candidate
Farah Mahmood, PhD Candidate in the Department of Chemistry, University of Saskatchewan, will present a seminar at 1:30 pm in HLTH GB06.
Title
Investigation of the synthesis of ceramic waste forms by low-temperature methods
Abstract
Nuclear reactors have the potential to be abundant sources of energy with a low carbon footprint. A major challenge of adopting nuclear power is the disposal of radionuclides from spent nuclear fuel. Current plans for managing high-level waste (HLW) involve sequestration in borosilicate glass and potential disposal in geological repositories. However, there is considerable interest in using ceramic oxides, such as pyrochlores (RE2Ti2O7, RE = Gd/Yb) and zirconolites (CaZrTi2O7), as alternative nuclear waste forms due to the high chemical durability and waste loading capabilities of these materials compared to borosilicate glass. The established ceramic method of synthesis of these materials requires a high annealing temperature (1400°C) and long reaction time (~6 days), thus making it difficult to scale up for industrial production. Solution-based synthesis methods, such as co-precipitation and sol-gel synthesis, can significantly reduce the annealing temperature required to prepare these materials.
This talk will present the relevant highlights of my doctoral research examining the effect of low-temperature synthesis on the structure of pyrochlore- and zirconolite-type oxides. Rietveld refinement of powder X-ray diffraction (XRD) patterns was used to elucidate changes to the long-range structure of these materials. Interestingly, Yb2Ti2O7 pyrochlores and zirconolites exhibited a temperature-dependent phase transition to defect fluorite. The local structural changes induced by phase transitions were examined using X-ray absorption near-edge spectroscopy (XANES) and extended X-ray absorption fine structure (EXAFS). Overall, the atomic scale mixing of precursors in the co-precipitation and sol-gel methods can dramatically lower annealing temperature and time required to prepare zirconolites and pyrochlores.
Date: Friday, March 24
Time: 1:30 pm
Place: HLTH GB06