Microstructural characterization and pore structure analysis of nuclear graphite

Kane, Joshua J.; Karthik, Chinnathambi; Butt, Darryl P.; Windes, William E.; Ubic, Rick

doi:10.1016/j.jnucmat.2011.05.053

Cited by 106 publications

(49 citation statements)

References 16 publications

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“…With increasing dose and irradiation temperature (PCIB4.0, PCIB6.8 and PCEA6.8), the narrowing of peaks, reduction in I D /I G ratio and a lower wavenumber G peak position, suggest that the higher irradiation temperature (655 C) allows defects to anneal. These results are in line with previous studies [7,9,17,35].…”

Section: Ramansupporting

confidence: 94%

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Micro to nanostructural observations in neutron irradiated nuclear graphites PCEA and PCIB

Freeman

Mironov

Windes

et al. 2017

Journal of Nuclear Materials

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a b s t r a c tThe neutron irradiation-induced structural changes in nuclear grade graphites PCEA and PCIB were investigated using scanning electron microscopy (SEM), X-ray diffraction (XRD), Raman spectroscopy, transmission electron microscopy (TEM), selected area electron diffraction (SAED) and electron energy loss spectroscopy (EELS). The graphite samples were irradiated at the Advanced Test Reactor at the Idaho National Laboratory. Received doses ranged from 1.5 to 6.8 displacements per atom and irradiation temperatures varied between 350 C and 670 C.XRD and Raman measurements provided evidence for irradiation induced crystallite fragmentation, with crystallite sizes reduced by 39e55%. Analysis of TEM images was used to quantify fringe length, tortuosity, and relative misorientation of planes, and indicated that neutron irradiation induced basal plane fragmentation and curvature. EELS was used to quantify the proportion of sp 2 bonding and specimen density; a slight reduction in planar-sp 2 content (due to the buckling basal planes and the introduction of non-six-membered rings) agreed with the observations from TEM.

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Section: Ramansupporting

confidence: 94%

“…PCIB is petroleumcoke-based, contains ultra-fine grains (ca. 20 mm in length) and is manufactured via isomoulding [7,22]. Since PCEA is an extruded grade the unique direction is with-grain.…”

Section: Methodsmentioning

confidence: 99%

Micro to nanostructural observations in neutron irradiated nuclear graphites PCEA and PCIB

Freeman

Mironov

Windes

et al. 2017

Journal of Nuclear Materials

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“…Electron irradiation causes point defect damage whereas the higher mass and lower dose rate of neutrons causes cascade damage. However, the relatively wide spacing of graphite's basal planes results in a low density of the cascade events, and the low neutron dose rates (10 -7 dpa s -1 ) and high temperatures (~450 °C) in the nuclear reactor allow damage to partially anneal out between cascade events [13][14][15].…”

Section: Irradiation Of Nuclear Graphitementioning

confidence: 99%

“…Transmission electron microscopy is an established tool for characterising both electron and neutron irradiated graphite [15,26]. There are however, very few detailed TEM-EELS studies on nuclear graphites but a significant volume of work on graphitizing and nongraphitizing carbons [27,28].…”

Section: Irradiation Of Nuclear Graphitementioning

confidence: 99%

Electron irradiation of nuclear graphite studied by transmission electron microscopy and electron energy loss spectroscopy

Mironov

Freeman

Brown

et al. 2015

Carbon

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Structural and chemical bonding changes in nuclear graphite have been investigated during in-situ electron irradiation in a transmission electron microscope (TEM); electron beam irradiation has been employed as a surrogate for neutron irradiation of nuclear grade graphite in nuclear reactors. This paper aims to set out a methodology for analysing the microstructure of electron-irradiated graphite which can then be extended to the analysis of neutron-irradiated graphites. The damage produced by exposure to 200 keV electrons was examined up to a total dose of approximately 0.5 dpa (equivalent to an electron fluence of 5.6x 10 21 electrons cm -2 ). During electron exposure, high resolution TEM images and electron energy loss spectra (EELS) were acquired periodically in order to record changes in structural (dis)order and chemical bonding, by quantitatively analysing the variation in phase contrast images and EEL spectra.

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“…Theoretical studies at the nanoscale are an important tool to explain underlying macroscopical phenomena and they can help to get a detailed understanding of the behavior of the irrad iated graphite in order to find an optimal solution for the maximized reactor lifet ime and permanent disposal [6][7]. Also, due to the enormous increase in publications on graphite-based structures and related materials for future applications, the work on modified graphitic surface becomes highly important.…”

Section: Introductionmentioning

confidence: 99%

Vacancy cluster in graphite: Migration energy and aggregation mechanism

El-Barbary

2018

AIP Conference Proceedings

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Abstract. Vacancy clusters in graphite have been investigated using Density Functional T heory (DFT) within B3LYP exchange-functional. The smallest size of vacancy clusters (V 4 ) has been chosen to study the migration energy and aggregation mechanism. Two main types of V 4 vacancy clusters have been modeled, the disc ( ) and the line vacancy clusters; including boat vacancy ( ) and zig-zag vacancy ( ). The results show that the presence of unstable V 3 vacancy may induce the mono-vacancy to migrate with low energy and vanish through forming stable V 4 vacancy cluster. Also, the calculated energy barriers required to form the boat vacancy cluster ( ), the zig-zag vacancy cluster ( ) and disk vacancy cluster ( ) support that the disc and the boat vacancy clusters co-exist. However the zig-zag type might only exist by knocking-out mechanism for highly irradiated graphite.

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Microstructural characterization and pore structure analysis of nuclear graphite

Cited by 106 publications

References 16 publications

Micro to nanostructural observations in neutron irradiated nuclear graphites PCEA and PCIB

Micro to nanostructural observations in neutron irradiated nuclear graphites PCEA and PCIB

Electron irradiation of nuclear graphite studied by transmission electron microscopy and electron energy loss spectroscopy

Vacancy cluster in graphite: Migration energy and aggregation mechanism

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