Experimental determination of the H–Hf phase diagram using in situ neutron diffraction

Dottor, Maxime; Crivello, Jean-Claude; Laversenne, L.; Joubert, Jean‐Marc

doi:10.1016/j.jallcom.2022.168353

Cited by 3 publications

(3 citation statements)

References 44 publications

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“…As MgO has a relatively high thermal conductivity of ~44 (W/ m•K) (Cheng et al, 2022) as compared to HfH 2 at ~10 (W/m•K) (Ito et al, 2009) the higher onset sintering temperature can, at least in part, be attributed to a processing thermal gradient from sample periphery of as large as 100 °C (Anselmi-Tamburini et al, 2005). The delay in sintering from Figure 8A Frontiers in Nuclear Engineering frontiersin.org primary lower H-phase has been identified as HfH 1.4 , consistent with the known phase diagram (Dottor et al, 2023). Noting that for similar thermal histories (cf Table 1), complete powder dehydriding occurs for naked (non-composited) HfH 2 powder after heating to above 800 °C, this confirms that compositing retards HfH 2 decomposition kinetics, even prior to full matrix densification.…”

Section: Entraining Hfh 2 Within Mgosupporting

confidence: 74%

“…Moreover, upon increasing the HfH 2 concentration to 55 vol.%, the retained HfH 2 phase (i.e., the amount of HfH 2 that remains HfH 2 ) increases from 3.43% to 16.38%. The hydrogen content quantified from the XRD analysis for the as-sintered CMCs is summarized in Table 2, with reference to the hydrogen content in bulk HfH 2 Frontiers in Nuclear Engineering frontiersin.org (Vetrano, 1971), lower hydrogen containing HfH x phases (Dottor et al, 2023), and H 2 O. The high hydrogen content in the solid shield CMCs compare favorably when compared to the hydrogen in water.…”

Section: Entraining Hfh 2 Within Mgomentioning

confidence: 99%

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Fabrication of neutron absorbing metal hydride entrained ceramic matrix shield composites

Bhardwaj,

Cheng,

Sprouster

et al. 2024

Front. Nucl. Eng.

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With significant improvement in High Temperature Superconductors (HTS), several projects are adopting HTS technology for fusion power systems. Compact HTS tokamaks offer potential advantages including lower plant costs, enhanced plasma control, and ultimately lower cost of electricity. However, as compact reactors have a reduced radial build to accommodate shielding, HTS degradation due to radiation damage or heating is a significant and potentially design limiting issue. Shielding must mitigate threats to the superconducting coils: neutron cascade damage, heat deposition and potentially organic insulator damage due x-rays. Unfortunately, there are currently no hi-performance shielding materials to enable the potential performance enhancement offered by HTS. In this work, we present a manufacturing method to fabricate a new class of composite shields that are high performance, high operating temperature, and simultaneously neutron absorbing and neutron moderating. The composite design consists of an entrained metal-hydride phase within a radiation stable MgO ceramic host matrix. We discuss the fabrication, characterization, and thermophysical performance data for a series of down-selected composite materials inspired by future fusion core designs and their operational performance metrics. To our knowledge these materials represent the first ceramic composite shield materials containing significant metal hydrides.

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Section: Entraining Hfh 2 Within Mgosupporting

confidence: 74%

Section: Entraining Hfh 2 Within Mgomentioning

confidence: 99%

Fabrication of neutron absorbing metal hydride entrained ceramic matrix shield composites

Bhardwaj,

Cheng,

Sprouster

et al. 2024

Front. Nucl. Eng.

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“…The tetragonal structure (deformed cubic δ -phase) of HfH x is observed in a range of 1.48 < x < 1.60. While pure hafnium has an hcp structure, recently, the experimental determination of the H-Hf phase diagram using in situ neutron diffraction was performed in [15]. Hence, detailed measurements and the analysis of the high-temperature behavior of Hf-H systems are urgently needed.…”

Section: Introductionmentioning

confidence: 99%

Titanium Carbide Coating for Hafnium Hydride Neutron Control Rods: In Situ X-ray Diffraction Study

Sidelev,

Pirozhkov,

Mishchenko

et al. 2023

Coatings

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This article considers the possibility of using a magnetron-deposited coating for the protection of hafnium hydrides at high temperatures as a material for neutron control rods. We describe the role of TiC coating in the high-temperature behavior of hafnium hydrides in a vacuum. A 1 µm thick TiC coating was deposited through magnetron sputtering on the outer surface of disk HfHx samples, and then in situ X-ray diffraction (XRD) measurements of both the uncoated and TiC-coated HfHx samples were performed using synchrotron radiation (at a wavelength of 1.64 Å) during linear heating, the isothermal stage (700 and 900 °C), and cooling to room temperature. Quadrupole mass spectrometry was used to identify the hydrogen release from the uncoated and TiC-coated hafnium hydride samples during their heating. We found the decomposition of the HfH1.7 phase to HfH1.5 and Hf and following hafnium oxidation after the significant decrease in hydrogen flow in the uncoated HfHx samples. The TiC coating can be used as a protective layer for HfHx under certain conditions (up to 700 °C); however, the fast hydrogen release can occur in the case of a coating failure. This study shows the temperature range for the possible application of TiC coatings for the protection of hafnium hydride from hydrogen release.

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In situ diffraction studies of phase-structural transformations in hydrogen and energy storage materials: An overview

Yartys

Webb

Cuevas

2023

Journal of Alloys and Compounds

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Experimental determination of the H–Hf phase diagram using in situ neutron diffraction

Cited by 3 publications

References 44 publications

Fabrication of neutron absorbing metal hydride entrained ceramic matrix shield composites

Fabrication of neutron absorbing metal hydride entrained ceramic matrix shield composites

Titanium Carbide Coating for Hafnium Hydride Neutron Control Rods: In Situ X-ray Diffraction Study

In situ diffraction studies of phase-structural transformations in hydrogen and energy storage materials: An overview

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