Thermophysical properties and expansion anisotropy of sintered hafnium hydride compacts
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Published version
Author(s)
Type
Journal Article
Abstract
Thermophysical properties are reported on ε-HfH2 samples fabricated by powder metallurgy. Samples were heat treated in the range 300-550 °C to transform them from ε-HfH2 to δ-HfH1.6-x, allowing comparison of the properties of both phases. Higher molar heat capacity was found in stoichiometric ε-HfH2 compared to literature data on sub-stoichiometric ε-HfH1.83. The δ-phase undergoes a vacancy order-disorder transformation at ~130 C with a transformation enthalpy of ~1.4 kJ mol-1. The room-temperature thermal diffusivity of the ε and δ phases were 0.11 and 0.09 cm2 s-1 respectively. The values are lower than those for literature bulk hydride materials, which is accounted for by pore-phonon scattering. Thermal expansion of ε and δ phases was measured by high-temperature X-ray diffraction to be 9.2 and 11 x10-6 K-1, respectively. The data on the ε phase is the first known data in the literature. The thermal expansion was highly anisotropic, with a negative thermal expansion parallel to the a-axis (Ra = -8.7). Such extreme anisotropy has implications in controlling the microstructure for thermal damage tolerance.
Date Issued
2025-12-01
Date Acceptance
2025-10-20
Citation
Nuclear Materials and Energy, 2025, 45
ISSN
2352-1791
Publisher
Elsevier
Journal / Book Title
Nuclear Materials and Energy
Volume
45
Copyright Statement
© 2025 The Author(s). Published by Elsevier Ltd. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).
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Publication Status
Published
Article Number
102014
Date Publish Online
2025-10-24