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Title: Size and shape of rhenium nanoparticles.

Abstract

In this paper the results from a detailed XAFS characterization of supported rhenium nanoparticles are presented. The Re nanoparticles are formed by the reduction of dispersed supported rhenium oxide in the presence of moist hydrogen. The shape of the wet-reduced Re clusters is determined by comparing the EXAFS spectra of Re-metal to the Re-wet-reduced clusters to 6 {angstrom}. A decrease in the signal from the 4th and 7th Re shells is an indication of sheet-like rather than spherical-like particles.

Authors:
; ; ; ; ; ; ; ; ; ; ;
Publication Date:
Research Org.:
Argonne National Lab. (ANL), Argonne, IL (United States)
Sponsoring Org.:
USDOE Office of Science (SC)
OSTI Identifier:
970771
Report Number(s):
ANL/XSD/CP-118912
TRN: US201003%%110
DOE Contract Number:
DE-AC02-06CH11357
Resource Type:
Conference
Resource Relation:
Conference: 13th International Conference on X-ray Absorption Fine Structure (XAFS 13); Jul. 9, 2006 - Jul. 14, 2006; Stanford, CA
Country of Publication:
United States
Language:
ENGLISH
Subject:
08 HYDROGEN; ABSORPTION; FINE STRUCTURE; HYDROGEN; RHENIUM; RHENIUM OXIDES; SHAPE; SPECTRA

Citation Formats

Yang, N., Mickelson, G. E., Greenlay, N., Kelly, S. D., Vila, F. D., Kas, J., Rehr, J. J., Bare, S. R., X-Ray Science Division, UOP LLC, EXAFS, and Univ. of Washington. Size and shape of rhenium nanoparticles.. United States: N. p., 2007. Web. doi:10.1063/1.2644602.
Yang, N., Mickelson, G. E., Greenlay, N., Kelly, S. D., Vila, F. D., Kas, J., Rehr, J. J., Bare, S. R., X-Ray Science Division, UOP LLC, EXAFS, & Univ. of Washington. Size and shape of rhenium nanoparticles.. United States. doi:10.1063/1.2644602.
Yang, N., Mickelson, G. E., Greenlay, N., Kelly, S. D., Vila, F. D., Kas, J., Rehr, J. J., Bare, S. R., X-Ray Science Division, UOP LLC, EXAFS, and Univ. of Washington. Mon . "Size and shape of rhenium nanoparticles.". United States. doi:10.1063/1.2644602.
@article{osti_970771,
title = {Size and shape of rhenium nanoparticles.},
author = {Yang, N. and Mickelson, G. E. and Greenlay, N. and Kelly, S. D. and Vila, F. D. and Kas, J. and Rehr, J. J. and Bare, S. R. and X-Ray Science Division and UOP LLC and EXAFS and Univ. of Washington},
abstractNote = {In this paper the results from a detailed XAFS characterization of supported rhenium nanoparticles are presented. The Re nanoparticles are formed by the reduction of dispersed supported rhenium oxide in the presence of moist hydrogen. The shape of the wet-reduced Re clusters is determined by comparing the EXAFS spectra of Re-metal to the Re-wet-reduced clusters to 6 {angstrom}. A decrease in the signal from the 4th and 7th Re shells is an indication of sheet-like rather than spherical-like particles.},
doi = {10.1063/1.2644602},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Mon Jan 01 00:00:00 EST 2007},
month = {Mon Jan 01 00:00:00 EST 2007}
}

Conference:
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  • In this paper the results from a detailed XAFS characterization of supported rhenium nanoparticles are presented. The Re nanoparticles are formed by the reduction of dispersed supported rhenium oxide in the presence of moist hydrogen. The shape of the wet--reduced Re clusters is determined by comparing the EXAFS spectra of Re-metal to the Re-wet-reduced clusters to 6 A. A decrease in the signal from the 4th and 7th Re shells is an indication of sheet-like rather than spherical-like particles.
  • Abstract not provided.
  • A common misconception is that as size decreases, quartz grains become progressively more angular. All possible size/shape relationships can and do occur including: 1) no relationship, 2) fine sizes, more rounded, 3) finer sized more angular, and 4) size/shape discontinuities where shape is constant over a wide range and then changes and stays constant over the remaining range. Detritus from large, long established flood plains (Mississippi, Ganges, Amazon) display a continuous change in shape with size. Detritus from primary sources generally display no size/shape effect. Small rivers commonly exhibit size/shape discontinuities. The origin of a particular size/shape relationship arises frommore » two opposing tendencies. Finer detritus travel much faster than coarser sands. Thus silts from one provenance can overtake coarser material of different provenance. If flood plains are large and long-lived, the contribution of individual tributaries is diluted almost to indetectibility and all sizes have time enough to reach the sea. In such situations the size/shape relationship reflects a steady state of equilibrium. In smaller rivers individual tributaries can provide significant proportions of grains to flood plains with characteristic sizes and shapes leading to discrete shifts in the size/shape curve.« less
  • Pure Re is being used in the SP-100. To obtain the desired final grain size it is necessary to both control the grain size of the starting Re strip and to avoid excessive grain growth during subsequent fabrication. It was found that the as-received strip, supplied by commerical vendors, typicall showed a large amount of scatter in its grain size. It was also observed that considerable grain growth often occurred during fabrication. The latter was due to strain induced grain boundary migration. A program was undertaken to develop a procedure to produce Re strip with a small and uniform grainmore » size. In addition pure Re tapered tensile specimens were fabricated and tested to qunatify the effects of the grain boundary migration. Results of the work with Re strip showed that its grain size could be made fine and uniform by following a rolling procedure that employs relatively large reductions between short intermediate anneals. The tapered tensile specimen tests showed that the amount of grain growth due to grain boundary migration increases greatly with higher annealing temperatures. Also the critical strain regime varies inversely with this temperature-- that is the critical strain regime decreases to a lower range of strain values at higher annealing temperatures.« less
  • No abstract prepared.