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Title: Development of low angle grain boundaries in lightly deformed superconducting niobium and their influence on hydride distribution and flux perturbation

This study shows that low angle grain boundaries (LAGBs) can be created by small 5% strains in high purity (RRR ≥ 200) SRF-grade single crystalline niobium (Nb) and that these boundaries act as hydrogen traps as indicated by the distribution of niobium hydrides (Nb 1-xH x). Nb 1-xH x is detrimental to superconducting radio frequency (SRF) Nb cavities due to its normal conducting properties at cavity operating temperatures. By designing a single crystal tensile sample extracted from a large grain (>5 cm) Nb ingot slice for preferred slip on one slip plane, LAGBs and dense dislocation boundaries developed. With chemical surface treatments following standard SRF cavity fabrication practice, Nb1-xHx phases were densely precipitated at the LAGBs upon cryogenic cooling (8-10 K/min). Micro-crystallographic analysis confirmed heterogeneous hydride precipitation, which included significant hydrogen atom accumulation in LAGBs. Magneto-optical imaging (MOI) analysis showed that these sites can then act as sites for both premature flux penetration and eventually flux trapping. However, this hydrogen related degradation at LAGBs did not completely disappear even after a 800 °C/2hrs anneal typically used for hydrogen removal in SRF Nb cavities. These findings suggest that hydride precipitation at a LAGB is facilitated by a non-equilibrium concentration of vacancy-hydrogenmore » (H) complexes aided by mechanical deformation and the hydride phase interferes with the recovery process under 800°C annealing.« less
Authors:
 [1] ;  [2] ; ORCiD logo [1] ; ORCiD logo [1] ; ORCiD logo [1] ;  [3] ; ORCiD logo [1] ;  [2] ; ORCiD logo [1]
  1. National High Magnetic Field Laboratory-Applied Superconductivity Center, Tallahassee, Florida 32310, USA
  2. Mechanical Engineering, College of Engineering, Michigan State University, East Lansing, Michigan 48824, USA
  3. Facility for Rare Isotope Beams, Michigan State University, East Lansing, Michigan 48824, USA
Publication Date:
Report Number(s):
FERMILAB-PUB-17-222-TD
Journal ID: ISSN 0021-8979; JAPIAU; DE-FG02-13ER41973
Grant/Contract Number:
SC0009960; FG02-13ER41973; DMR-1157490; AC02-07CH11359
Type:
Accepted Manuscript
Journal Name:
Journal of Applied Physics
Additional Journal Information:
Journal Volume: 121; Journal Issue: 19; Journal ID: ISSN 0021-8979
Publisher:
American Institute of Physics (AIP)
Research Org:
Florida State Univ., Tallahassee, FL (United States); Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States)
Sponsoring Org:
USDOE Office of Science (SC), High Energy Physics (HEP) (SC-25); State of Florida (United States); National Science Foundation (NSF)
Contributing Orgs:
Michigan State Univ., East Lansing, MI (United States)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; 75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; 43 PARTICLE ACCELERATORS; Niobium; Grain boundaries; Superconductivity; Magnetic flux; Dislocations
OSTI Identifier:
1361685
Alternate Identifier(s):
OSTI ID: 1361680; OSTI ID: 1361893; OSTI ID: 1371587

Sung, Z. -H., Wang, M., Polyanskii, A. A., Santosh, C., Balachandran, S., Compton, C., Larbalestier, D. C., Bieler, T. R., and Lee, P. J.. Development of low angle grain boundaries in lightly deformed superconducting niobium and their influence on hydride distribution and flux perturbation. United States: N. p., Web. doi:10.1063/1.4983512.
Sung, Z. -H., Wang, M., Polyanskii, A. A., Santosh, C., Balachandran, S., Compton, C., Larbalestier, D. C., Bieler, T. R., & Lee, P. J.. Development of low angle grain boundaries in lightly deformed superconducting niobium and their influence on hydride distribution and flux perturbation. United States. doi:10.1063/1.4983512.
Sung, Z. -H., Wang, M., Polyanskii, A. A., Santosh, C., Balachandran, S., Compton, C., Larbalestier, D. C., Bieler, T. R., and Lee, P. J.. 2017. "Development of low angle grain boundaries in lightly deformed superconducting niobium and their influence on hydride distribution and flux perturbation". United States. doi:10.1063/1.4983512. https://www.osti.gov/servlets/purl/1361685.
@article{osti_1361685,
title = {Development of low angle grain boundaries in lightly deformed superconducting niobium and their influence on hydride distribution and flux perturbation},
author = {Sung, Z. -H. and Wang, M. and Polyanskii, A. A. and Santosh, C. and Balachandran, S. and Compton, C. and Larbalestier, D. C. and Bieler, T. R. and Lee, P. J.},
abstractNote = {This study shows that low angle grain boundaries (LAGBs) can be created by small 5% strains in high purity (RRR ≥ 200) SRF-grade single crystalline niobium (Nb) and that these boundaries act as hydrogen traps as indicated by the distribution of niobium hydrides (Nb1-xHx). Nb1-xHx is detrimental to superconducting radio frequency (SRF) Nb cavities due to its normal conducting properties at cavity operating temperatures. By designing a single crystal tensile sample extracted from a large grain (>5 cm) Nb ingot slice for preferred slip on one slip plane, LAGBs and dense dislocation boundaries developed. With chemical surface treatments following standard SRF cavity fabrication practice, Nb1-xHx phases were densely precipitated at the LAGBs upon cryogenic cooling (8-10 K/min). Micro-crystallographic analysis confirmed heterogeneous hydride precipitation, which included significant hydrogen atom accumulation in LAGBs. Magneto-optical imaging (MOI) analysis showed that these sites can then act as sites for both premature flux penetration and eventually flux trapping. However, this hydrogen related degradation at LAGBs did not completely disappear even after a 800 °C/2hrs anneal typically used for hydrogen removal in SRF Nb cavities. These findings suggest that hydride precipitation at a LAGB is facilitated by a non-equilibrium concentration of vacancy-hydrogen (H) complexes aided by mechanical deformation and the hydride phase interferes with the recovery process under 800°C annealing.},
doi = {10.1063/1.4983512},
journal = {Journal of Applied Physics},
number = 19,
volume = 121,
place = {United States},
year = {2017},
month = {5}
}

Works referenced in this record:

Transport in superconducting niobium films for radio frequency applications
journal, April 2005
  • Halbritter, J.
  • Journal of Applied Physics, Vol. 97, Issue 8, Article No. 083904
  • DOI: 10.1063/1.1874292