a1 Department of Materials Science and Engineering, Boise State University, 1910 University Drive, Boise, ID 83725, USA
a2 Center for Advanced Energy Studies, 995 University Blvd., Idaho Falls, ID 83415, USA
a3 Idaho National Laboratory, 2351 N. Boulevard, Idaho Falls, ID 83415, USA
This article reports the microstructural characteristics of various petroleum and pitch based nuclear graphites (IG-110, NBG-18, and PCEA) that are of interest to the next generation nuclear plant program. Bright-field transmission electron microscopy imaging was used to identify and understand the different features constituting the microstructure of nuclear graphite such as the filler particles, microcracks, binder phase, rosette-shaped quinoline insoluble (QI) particles, chaotic structures, and turbostratic graphite phase. The dimensions of microcracks were found to vary from a few nanometers to tens of microns. Furthermore, the microcracks were found to be filled with amorphous carbon of unknown origin. The pitch coke based graphite (NBG-18) was found to contain higher concentration of binder phase constituting QI particles as well as chaotic structures. The turbostratic graphite, present in all of the grades, was identified through their elliptical diffraction patterns. The difference in the microstructure has been analyzed in view of their processing conditions.
(Received March 16 2011)
(Accepted September 16 2011)