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Gordon, Margaret Ellen

Publications and source records attributed to Gordon, Margaret Ellen.

At least 19 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2023

Tunable negative coefficient thermal expansion materials and composites

The present disclosure is directed to variable composition ceramics. Zr (2−x) Hf (x) WP 2 O 12 and Hf 2 WP 2 O 12 exhibit large negative thermal expansion that is linear over a large temperature range up to at least 900° C., These new ceramic material particles may be mixed with polymers to make a composite suitable for use in backsheets for photovoltaic modules or in other applications. The thermal expansion coefficient of the composite can be tailored to match that of the solar cell in order to reduce stress resulting from daily thermal cycling.

Gordon, Margaret Ellen↗
DOE OSTI2019

Novel Zoned Waste-forms for High-Priority Radionuclide Waste Streams

This report describes the potential of a novel class of materials—α-ZrW 2 O 8 , Zr 2 WP 2 O 12 , and related compounds that contract upon amorphization as possible radionuclide waste-forms. The proposed ceramic waste-forms would consist of zoned grains, or sintered ceramics with center- loaded radionuclides and barren shells. Radiation-induced amorphization would result in core shrinkage but would not fracture the shells or overgrowths, maintaining isolation of the radionuclide. In this report, we have described synthesis techniques to produce phase-pure forms of the materials, and how to fully densify those materials. Structural models for the materials were developed and validated using DFPT approaches, and radionuclide substitution was evaluated; U(IV), Pu(IV), Tc(IV) and Tc(VII) all readily substitute into the material structures. MD modeling indicated that strain associated with radiation-induced amorphization would not affect the integrity of surrounding crystalline materials, and these results were validated via ion beam experimental studies. Finally, we have evaluated the leach rates of the barren materials, as determined by batch and flow-through reactor experiments. ZrW 2 O 8 leaches rapidly, releasing tungstate while Zr is retained as a solid oxide or hydroxide. Tungsten release rates remain elevated over time and are highly sensitive to contact times, suggesting that this material will not be an effective waste-form. Conversely, tungsten releases rates from Zr 2 WP 2 O 12 rapidly drop, show little dependence on short-term changes in fluid contact time, and in over time, become tied to P release rates. The results presented here suggest that this material may be a viable waste-form for some hard-to-handle radionuclides such as Pu and Tc.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2019

Elucidating Structure–Spectral Property Relationships of Negative Thermal Expansion Zr 2 (WO 4 )(PO 4 ) 2 : A First-Principles Study with Experimental Validation

The phonon, infrared, and Raman spectroscopic properties of zirconium tungsten phosphate, Zr 2 (WO 4 )(PO 4 ) 2 (space group Pbcn , IT No. 60; Z = 4), have been extensively investigated using density functional perturbation theory (DFPT) calculations with the Perdew, Burke, and Ernzerhof exchange–correlation functional revised for solids (PBEsol) and validated by experimental characterization of Zr 2 (WO 4 )(PO 4 ) 2 prepared by hydrothermal synthesis. Using DFPT-simulated infrared, Raman, and phonon density-of-state spectra combined with Fourier transform infrared and Raman measurements, new comprehensive and extensive assignments have been made for the spectra of Zr 2 (WO 4 )(PO 4 ) 2 , resulting in the characterization of its 29 and 34 most intense IR- and Raman-active modes, respectively. DFPT results also reveal that ν 1 (PO 4 ) symmetric stretching and ν 3 (PO 4 ) antisymmetric stretching bands have been interchanged in previous Raman experimental assignments. Negative thermal expansion in Zr 2 (WO 4 )(PO 4 ) 2 appears to have very limited impact on the spectral properties of this compound. Furthermore, this work shows the high accuracy of the PBEsol exchange–correlation functional for studying the spectroscopic properties of crystalline materials using first-principles methods.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗