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Title: Investigating possible kinetic limitations to MgB 2 hydrogenation

Abstract

An investigation is reported of possible kinetic limitations to MgB 2 hydrogenation. The role of H–H bond breaking, a necessary first step in the hydrogenation process, is assessed for bulk MgB 2, ball-milled MgB 2, as well as MgB 2 mixed with Pd, Fe and TiF 3 additives. The Pd and Fe additives in the MgB 2 material exist as dispersed metallic particles in the size range ~5–40 nm diameter. In contrast, TiF 3 reacts with MgB 2 to form Ti metal, elemental B and MgB 2, with the Ti and the MgB 2 phases proximate to each other and coating the MgB 2 particulates with a film of thickness ~3 nm. Sieverts studies of hydrogenation kinetics are reported and compared to the rate of H–H bond breaking as measured by H-D exchange studies. The results show that H–H bond dissociation does not limit the rate of hydrogenation of MgB 2 because H–H bond cleavage occurs rapidly compared to the initial MgB 2 hydrogenation. The results also show that surface diffusion of hydrogen atoms cannot be a limiting factor for MgB 2 hydrogenation. Instead, it is speculated that it is the intrinsic stability of the B–B extended hexagonal ring structuremore » in MgB 2 that hinders the hydrogenation of this material. This supposition is supported by B K-edge x-ray absorption measurements of the materials, which showed spectroscopically that the B–B ring was intact in the material systems studied. The TiF 3/MgB 2 system was examined further theoretically with reaction thermodynamics and phase nucleation kinetic calculations to better understand the production of Ti metal when TiB 2 is thermodynamically favored. Finally, the results show that there exist physically reasonable ranges for which nucleation kinetics supersede thermodynamics in determining the reactive pathway for the TiF 3/MgB 2 system and perhaps for other additive systems as well.« less

Authors:
 [1];  [2];  [2];  [2];  [2];  [3];  [3];  [3];  [3];  [1];  [3];  [2];  [3]
  1. Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
  2. Sandia National Lab. (SNL-CA), Livermore, CA (United States)
  3. Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
Publication Date:
Research Org.:
Sandia National Lab. (SNL-CA), Livermore, CA (United States)
Sponsoring Org.:
USDOE Office of Energy Efficiency and Renewable Energy (EERE); USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
OSTI Identifier:
1574810
Alternate Identifier(s):
OSTI ID: 1577899
Report Number(s):
SAND2019-5900J
Journal ID: ISSN 0360-3199; 675831
Grant/Contract Number:  
AC04-94AL85000; NA0003525; AC52-07NA27344; AC02–05CH11231; AC02-05CH11231
Resource Type:
Accepted Manuscript
Journal Name:
International Journal of Hydrogen Energy
Additional Journal Information:
Journal Volume: 44; Journal Issue: 59; Journal ID: ISSN 0360-3199
Publisher:
Elsevier
Country of Publication:
United States
Language:
English
Subject:
08 HYDROGEN; hydrogen storage; magnesium diboride; hydrogenation; kinetics; H-D exchange; surface diffusion

Citation Formats

Liu, Y. -S., Klebanoff, L. E., Wijeratne, P., Cowgill, D. F., Stavila, V., Heo, T. W., Kang, S., Baker, A. A., Lee, J. R. I., Mattox, T. M., Ray, K. G., Sugar, J. D., and Wood, B. C. Investigating possible kinetic limitations to MgB2 hydrogenation. United States: N. p., 2019. Web. doi:10.1016/j.ijhydene.2019.09.125.
Liu, Y. -S., Klebanoff, L. E., Wijeratne, P., Cowgill, D. F., Stavila, V., Heo, T. W., Kang, S., Baker, A. A., Lee, J. R. I., Mattox, T. M., Ray, K. G., Sugar, J. D., & Wood, B. C. Investigating possible kinetic limitations to MgB2 hydrogenation. United States. doi:10.1016/j.ijhydene.2019.09.125.
Liu, Y. -S., Klebanoff, L. E., Wijeratne, P., Cowgill, D. F., Stavila, V., Heo, T. W., Kang, S., Baker, A. A., Lee, J. R. I., Mattox, T. M., Ray, K. G., Sugar, J. D., and Wood, B. C. Fri . "Investigating possible kinetic limitations to MgB2 hydrogenation". United States. doi:10.1016/j.ijhydene.2019.09.125.
@article{osti_1574810,
title = {Investigating possible kinetic limitations to MgB2 hydrogenation},
author = {Liu, Y. -S. and Klebanoff, L. E. and Wijeratne, P. and Cowgill, D. F. and Stavila, V. and Heo, T. W. and Kang, S. and Baker, A. A. and Lee, J. R. I. and Mattox, T. M. and Ray, K. G. and Sugar, J. D. and Wood, B. C.},
abstractNote = {An investigation is reported of possible kinetic limitations to MgB2 hydrogenation. The role of H–H bond breaking, a necessary first step in the hydrogenation process, is assessed for bulk MgB2, ball-milled MgB2, as well as MgB2 mixed with Pd, Fe and TiF3 additives. The Pd and Fe additives in the MgB2 material exist as dispersed metallic particles in the size range ~5–40 nm diameter. In contrast, TiF3 reacts with MgB2 to form Ti metal, elemental B and MgB2, with the Ti and the MgB2 phases proximate to each other and coating the MgB2 particulates with a film of thickness ~3 nm. Sieverts studies of hydrogenation kinetics are reported and compared to the rate of H–H bond breaking as measured by H-D exchange studies. The results show that H–H bond dissociation does not limit the rate of hydrogenation of MgB2 because H–H bond cleavage occurs rapidly compared to the initial MgB2 hydrogenation. The results also show that surface diffusion of hydrogen atoms cannot be a limiting factor for MgB2 hydrogenation. Instead, it is speculated that it is the intrinsic stability of the B–B extended hexagonal ring structure in MgB2 that hinders the hydrogenation of this material. This supposition is supported by B K-edge x-ray absorption measurements of the materials, which showed spectroscopically that the B–B ring was intact in the material systems studied. The TiF3/MgB2 system was examined further theoretically with reaction thermodynamics and phase nucleation kinetic calculations to better understand the production of Ti metal when TiB2 is thermodynamically favored. Finally, the results show that there exist physically reasonable ranges for which nucleation kinetics supersede thermodynamics in determining the reactive pathway for the TiF3/MgB2 system and perhaps for other additive systems as well.},
doi = {10.1016/j.ijhydene.2019.09.125},
journal = {International Journal of Hydrogen Energy},
number = 59,
volume = 44,
place = {United States},
year = {2019},
month = {11}
}

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This content will become publicly available on November 29, 2020
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