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Title: Precession electron diffraction for SiC grain boundary characterization in unirradiated TRISO fuel

Precession electron diffraction (PED), a transmission electron microscopy-based technique, has been evaluated for the suitability for evaluating grain boundary character in the SiC layer of tristructural isotropic (TRISO) fuel. Although the ultimate goal is to determine the grain boundary characteristics of fission product containing grain boundaries of neutron irradiated SiC, our work reports the effect of transmission electron microscope (TEM) lamella thickness on quality of data and establishes a baseline comparison on grain boundary characteristics determined previously using a conventional EBSD scanning electron microscope (SEM) based technique. In general, it was determined that the lamella thickness produced using the standard FIB fabrication process, is sufficient to provide reliable PED measurements with thicker lamellae (~120 nm) produce higher quality orientation data. Analysis of grain boundary character from the TEM-based PED data showed a much lower fraction of low angle grain boundaries compared to SEM-based EBSD data from the SiC layer of the same TRISO-coated particle as well as a SiC layer deposited at a slightly lower temperature. The fractions of high angle and CSL-related grain boundaries determined by PED are similar to those found using SEM-based EBSD. Since the grain size of the SiC layer of TRSIO fuel can be asmore » small as 250 nm [12], depending on the fabrication parameters, and grain boundary fission product precipitates can be nano-sized, the TEM-based PED orientation data collection method is preferred to determine an accurate representation of the relative fractions of low angle, high angle and CSL-related grain boundaries. It was concluded that although the resolution of the PED data is better by more than an order of magnitude, data acquisition times may be significantly longer or the number of areas analyzed significantly larger than the SEM-based method to obtain a statistically relevant distribution. Also, grain size could be accurately determined but significantly larger analysis areas than those used in this study would be required.« less
Authors:
 [1] ;  [2] ;  [3]
  1. Idaho National Lab. (INL), Idaho Falls, ID (United States). Materials Science and Engineering Dept.
  2. Idaho National Lab. (INL), Idaho Falls, ID (United States). Fuel Performance and Design Dept.
  3. Boise State Univ., ID (United States). Micron School of Materials Science and Engineering; Center for Advanced Energy Studies, Idaho Falls, ID (United States)
Publication Date:
Report Number(s):
INL/JOU-15-36696
Journal ID: ISSN 0029-5493; PII: S002954931630142X
Grant/Contract Number:
AC07-05ID14517
Type:
Accepted Manuscript
Journal Name:
Nuclear Engineering and Design
Additional Journal Information:
Journal Volume: 305; Journal Issue: C; Journal ID: ISSN 0029-5493
Publisher:
Elsevier
Research Org:
Idaho National Lab. (INL), Idaho Falls, ID (United States)
Sponsoring Org:
USDOE Office of Nuclear Energy (NE)
Country of Publication:
United States
Language:
English
Subject:
11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS; energy dispersive spectroscopy (EDS); SiC; transmission electron microscope (TEM); tristructural isotropic (TRISO)
OSTI Identifier:
1357463
Alternate Identifier(s):
OSTI ID: 1426298

Lillo, T. M., van Rooyen, I. J., and Wu, Y. Q.. Precession electron diffraction for SiC grain boundary characterization in unirradiated TRISO fuel. United States: N. p., Web. doi:10.1016/j.nucengdes.2016.05.027.
Lillo, T. M., van Rooyen, I. J., & Wu, Y. Q.. Precession electron diffraction for SiC grain boundary characterization in unirradiated TRISO fuel. United States. doi:10.1016/j.nucengdes.2016.05.027.
Lillo, T. M., van Rooyen, I. J., and Wu, Y. Q.. 2016. "Precession electron diffraction for SiC grain boundary characterization in unirradiated TRISO fuel". United States. doi:10.1016/j.nucengdes.2016.05.027. https://www.osti.gov/servlets/purl/1357463.
@article{osti_1357463,
title = {Precession electron diffraction for SiC grain boundary characterization in unirradiated TRISO fuel},
author = {Lillo, T. M. and van Rooyen, I. J. and Wu, Y. Q.},
abstractNote = {Precession electron diffraction (PED), a transmission electron microscopy-based technique, has been evaluated for the suitability for evaluating grain boundary character in the SiC layer of tristructural isotropic (TRISO) fuel. Although the ultimate goal is to determine the grain boundary characteristics of fission product containing grain boundaries of neutron irradiated SiC, our work reports the effect of transmission electron microscope (TEM) lamella thickness on quality of data and establishes a baseline comparison on grain boundary characteristics determined previously using a conventional EBSD scanning electron microscope (SEM) based technique. In general, it was determined that the lamella thickness produced using the standard FIB fabrication process, is sufficient to provide reliable PED measurements with thicker lamellae (~120 nm) produce higher quality orientation data. Analysis of grain boundary character from the TEM-based PED data showed a much lower fraction of low angle grain boundaries compared to SEM-based EBSD data from the SiC layer of the same TRISO-coated particle as well as a SiC layer deposited at a slightly lower temperature. The fractions of high angle and CSL-related grain boundaries determined by PED are similar to those found using SEM-based EBSD. Since the grain size of the SiC layer of TRSIO fuel can be as small as 250 nm [12], depending on the fabrication parameters, and grain boundary fission product precipitates can be nano-sized, the TEM-based PED orientation data collection method is preferred to determine an accurate representation of the relative fractions of low angle, high angle and CSL-related grain boundaries. It was concluded that although the resolution of the PED data is better by more than an order of magnitude, data acquisition times may be significantly longer or the number of areas analyzed significantly larger than the SEM-based method to obtain a statistically relevant distribution. Also, grain size could be accurately determined but significantly larger analysis areas than those used in this study would be required.},
doi = {10.1016/j.nucengdes.2016.05.027},
journal = {Nuclear Engineering and Design},
number = C,
volume = 305,
place = {United States},
year = {2016},
month = {6}
}