Development of mesopores in superfine grain graphite neutron-irradiated at high fluence

Cristian I. Contescu; José D. Arregui-Mena; Anne A. Campbell; Philip D. Edmondson; Nidia C. Gallego; Kentaro Takizawa; Yutai Katoh

doi:10.1016/j.carbon.2018.08.039

Development of mesopores in superfine grain graphite neutron-irradiated at high fluence

Cristian I. Contescu, José D. Arregui-Mena, Anne A. Campbell, Philip D. Edmondson, Nidia C. Gallego, Kentaro Takizawa, Yutai Katoh

Research output: Contribution to journal › Article › peer-review

33 Scopus citations

Abstract

Microstructural changes induced by neutron irradiation of superfine grain graphite G347A (Tokai Carbon, Japan) were examined by nitrogen adsorption at 77 K and by three microscopy techniques (SEM, TEM and FIB-SEM tomography). The specimens were irradiated at doses of up to 30 dpa, covering stages before and after the turnaround fluence at three temperatures (300, 450, 750 °C) of their irradiation envelope. The initial graphite densification at low fluences did not produce any detectable effect in the pore size range (<350 nm) measured by gas adsorption. However, graphite irradiated at high fluences, after turnaround, showed severe structural changes. At all three temperatures and high irradiation fluences, gas adsorption revealed significant increase of the volume of narrow mesopores (<5–20 nm) and up to five times increase of BET surface area, both in linear relationship with the relative volume expansion. Analysis of microscopy images showed multiplication of fine macropores (>50 nm) at high irradiation fluences and more structural changes on multiple scales, from nanometers to microns. This work demonstrates the unique ability of gas adsorption techniques to analyze open pores with sizes between sub-nanometer and sub-micron in bulk nuclear graphite, with supporting microscopy results.

Original language	English
Pages (from-to)	663-675
Number of pages	13
Journal	Carbon
Volume	141
DOIs	https://doi.org/10.1016/j.carbon.2018.08.039
State	Published - Jan 2019

Funding

This work was funded by a Nuclear Science User Facilities (NSUF) Rapid Turnaround Experiment (RTE) award. NSUF is the U.S. Department of Energy, Nuclear Energy Office's only designated nuclear energy user facility. A portion of this research used the resources of the Low Activation Materials Development and Analysis Laboratory (LAMDA), a DOE Office of Science research facility operated by the Oak Ridge National Laboratory (ORNL), and resources at the High Flux Isotope Reactor (HFIR), a DOE Office of Science User Facility operated by ORNL. Partial support from the Advanced Reactor Technologies program of DOE Office of Nuclear Energy is also acknowledged. The authors are grateful to Tokai Carbon Co., Ltd. (Japan) for providing graphite grade G347A. Oak Ridge National Laboratory is managed by UT-Battelle under contract DE-AC05-00OR22725.

Funders	Funder number
Nuclear Energy
UT-Battelle	DE-AC05-00OR22725
U.S. Department of Energy
Oak Ridge National Laboratory

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title = "Development of mesopores in superfine grain graphite neutron-irradiated at high fluence",

abstract = "Microstructural changes induced by neutron irradiation of superfine grain graphite G347A (Tokai Carbon, Japan) were examined by nitrogen adsorption at 77 K and by three microscopy techniques (SEM, TEM and FIB-SEM tomography). The specimens were irradiated at doses of up to 30 dpa, covering stages before and after the turnaround fluence at three temperatures (300, 450, 750 °C) of their irradiation envelope. The initial graphite densification at low fluences did not produce any detectable effect in the pore size range (<350 nm) measured by gas adsorption. However, graphite irradiated at high fluences, after turnaround, showed severe structural changes. At all three temperatures and high irradiation fluences, gas adsorption revealed significant increase of the volume of narrow mesopores (<5–20 nm) and up to five times increase of BET surface area, both in linear relationship with the relative volume expansion. Analysis of microscopy images showed multiplication of fine macropores (>50 nm) at high irradiation fluences and more structural changes on multiple scales, from nanometers to microns. This work demonstrates the unique ability of gas adsorption techniques to analyze open pores with sizes between sub-nanometer and sub-micron in bulk nuclear graphite, with supporting microscopy results.",

author = "Contescu, {Cristian I.} and Arregui-Mena, {Jos{\'e} D.} and Campbell, {Anne A.} and Edmondson, {Philip D.} and Gallego, {Nidia C.} and Kentaro Takizawa and Yutai Katoh",

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doi = "10.1016/j.carbon.2018.08.039",

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AU - Contescu, Cristian I.

AU - Arregui-Mena, José D.

AU - Campbell, Anne A.

AU - Edmondson, Philip D.

AU - Gallego, Nidia C.

AU - Takizawa, Kentaro

AU - Katoh, Yutai

PY - 2019/1

Y1 - 2019/1

N2 - Microstructural changes induced by neutron irradiation of superfine grain graphite G347A (Tokai Carbon, Japan) were examined by nitrogen adsorption at 77 K and by three microscopy techniques (SEM, TEM and FIB-SEM tomography). The specimens were irradiated at doses of up to 30 dpa, covering stages before and after the turnaround fluence at three temperatures (300, 450, 750 °C) of their irradiation envelope. The initial graphite densification at low fluences did not produce any detectable effect in the pore size range (<350 nm) measured by gas adsorption. However, graphite irradiated at high fluences, after turnaround, showed severe structural changes. At all three temperatures and high irradiation fluences, gas adsorption revealed significant increase of the volume of narrow mesopores (<5–20 nm) and up to five times increase of BET surface area, both in linear relationship with the relative volume expansion. Analysis of microscopy images showed multiplication of fine macropores (>50 nm) at high irradiation fluences and more structural changes on multiple scales, from nanometers to microns. This work demonstrates the unique ability of gas adsorption techniques to analyze open pores with sizes between sub-nanometer and sub-micron in bulk nuclear graphite, with supporting microscopy results.

AB - Microstructural changes induced by neutron irradiation of superfine grain graphite G347A (Tokai Carbon, Japan) were examined by nitrogen adsorption at 77 K and by three microscopy techniques (SEM, TEM and FIB-SEM tomography). The specimens were irradiated at doses of up to 30 dpa, covering stages before and after the turnaround fluence at three temperatures (300, 450, 750 °C) of their irradiation envelope. The initial graphite densification at low fluences did not produce any detectable effect in the pore size range (<350 nm) measured by gas adsorption. However, graphite irradiated at high fluences, after turnaround, showed severe structural changes. At all three temperatures and high irradiation fluences, gas adsorption revealed significant increase of the volume of narrow mesopores (<5–20 nm) and up to five times increase of BET surface area, both in linear relationship with the relative volume expansion. Analysis of microscopy images showed multiplication of fine macropores (>50 nm) at high irradiation fluences and more structural changes on multiple scales, from nanometers to microns. This work demonstrates the unique ability of gas adsorption techniques to analyze open pores with sizes between sub-nanometer and sub-micron in bulk nuclear graphite, with supporting microscopy results.

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Development of mesopores in superfine grain graphite neutron-irradiated at high fluence

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