The h- sc (Hydrogen- Scandium) system

Manchester, F. D.; Pitre, J. M.

doi:10.1007/bf02665706

Cited by 18 publications

(15 citation statements)

References 61 publications

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“…al. 15 explain that the (αSc+ δ / δ) boundary at room temperature is located at x=1.68 (62.7%H) for ScH x . The boundary extends to lower values of x at higher temperatures, such as that used during deposition.…”

Section: Scandium Deuteride Thin Film Growth Experimentsmentioning

confidence: 88%

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Microstructure, Phase Formation, and Stress of Reactively-Deposited Metal Hydride Thin Films

Adams¹,

Romero²,

Rodriguez³

et al. 2002

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Section: Scandium Deuteride Thin Film Growth Experimentsmentioning

confidence: 88%

“…15 In that publication, the authors summarize previous work and their own to generate a T-χ phase diagram for P < 0.13 MPa. This is shown in Figure 6.…”

Section: Sc-h Systemmentioning

confidence: 99%

Microstructure, Phase Formation, and Stress of Reactively-Deposited Metal Hydride Thin Films

Adams¹,

Romero²,

Rodriguez³

et al. 2002

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“…Niobium hydrides have been studied extensively and a number of different hydride phases have been identified [ 69 ]. However, the niobium-hydrogen phase diagram has not been completely determined and there are a number of phases that authors have identified by one technique or another that have not been confirmed or the phase field clearly identified.…”

Section: Discussionmentioning

confidence: 99%

“…However, the niobium-hydrogen phase diagram has not been completely determined and there are a number of phases that authors have identified by one technique or another that have not been confirmed or the phase field clearly identified. Manchester and Pitre [ 69 , 70 ] reviewed the literature on niobium-hydrogen phases and compiled the data into the assessment of the temperature-composition diagram shown in Fig. 7(a) .…”

Section: Discussionmentioning

confidence: 99%

Evaluation of the propensity of niobium to absorb hydrogen during fabrication of superconducting radio frequency cavities for particle accelerators

Ricker¹,

Myneni²

2010

J. Res. Natl. Inst. Stand. Technol.

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The propensity of active metals to absorb hydrogen during service in environments containing water or water vapor is a well-known and thoroughly studied phenomenon [3][4][5], but the possibility of similar processes occurring during fabrication is frequently overlooked. During the fabrication of niobium (Nb) superconducting radio frequency (SRF) cavities for use in particle accelerators, there are a number of processing steps where the passivating film of niobium pentoxide (Nb 2 O 5 ) is removed by chemical or mechanical means. When this occurs, the underlying metal is put into direct contact with the processing environment and is free to react with this environment. If the metal is sufficiently active, then the subsequent reactions may produce hydrogen at activities that may result in the metal absorbing hydrogen and in some cases, the hydrogen activity may be sufficient to supersaturate the metal with respect to hydride phases. When the passive Volume 115, Number 5, September-October 2010 Journal During the fabrication of niobium superconducting radio frequency (SRF) particle accelerator cavities procedures are used that chemically or mechanically remove the passivating surface film of niobium pentoxide (Nb 2 O 5 ). Removal of this film will expose the underlying niobium metal and allow it to react with the processing environment. If these reactions produce hydrogen at sufficient concentrations and rates, then hydrogen will be absorbed and diffuse into the metal. High hydrogen activities could result in supersaturation and the nucleation of hydride phases. If the metal repassivates at the conclusion of the processing step and the passive film blocks hydrogen egress, then the absorbed hydrogen or hydrides could be retained and alter the performance of the metal during subsequent processing steps or in-service. This report examines the feasibility of this hypothesis by first identifying the postulated events, conditions, and reactions and then determining if each is consistent with accepted scientific principles, literature, and data. Established precedent for similar events in other systems was found in the scientific literature and thermodynamic analysis found that the postulated reactions were not only energetically favorable, but produced large driving forces. The hydrogen activity or fugacity required for the reactions to be at equilibrium was determined to indicate the propensity for hydrogen evolution, absorption, and hydride nucleation. The influence of processing conditions and kinetics on the proximity of hydrogen surface coverage to these theoretical values is discussed. This examination found that the hypothesis of hydrogen absorption during SRF processing is consistent with published scientific literature and thermodynamic principles.Key words: corrosion; diffusion; electropolishing; fabrication; hydrogen absorption; niobium; particle accelerator cavities; superconducting radio frequency. film reforms, this film may block egress of the absorbed hydrogen allowing it to remain in the metal and infl...

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“…Sc forms a solid solution (ScH x , x ≤ 0.43), a dihydride (ScH 2 ), and a trihydride (ScH 3 ) [6][7][8][9][10]. The crystal structure and electrical properties of ScH 3 are not well studied because a high hydrogen gas pressure is required for trihydrogenation, and ScH 3 reversibly decomposes into the dihydride upon releasing hydrogen gas pressure.…”

Section: Introductionmentioning

confidence: 99%

Pressure-induced structural change from hexagonal to fcc metal lattice in scandium trihydride

Ohmura

Machida

Watanuki

et al. 2007

Journal of Alloys and Compounds

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The h- sc (Hydrogen- Scandium) system

Cited by 18 publications

References 61 publications

Microstructure, Phase Formation, and Stress of Reactively-Deposited Metal Hydride Thin Films

Microstructure, Phase Formation, and Stress of Reactively-Deposited Metal Hydride Thin Films

Evaluation of the propensity of niobium to absorb hydrogen during fabrication of superconducting radio frequency cavities for particle accelerators

Pressure-induced structural change from hexagonal to fcc metal lattice in scandium trihydride

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