Title: Effect of Stress on Irradiation Responses of Highly Oriented Pyrolytic Graphite

Abstract

The effect of stress on irradiation responses of highly oriented pyrolytic graphite (HOPG) was studied by combing molecular dynamics (MD) simulation, proton irradiation, and Raman characterization. MD simulations of carbon knock-on at energies < 60 eV were used to obtain average threshold displacement energies ($$\overline{E}$$_d) as a function of strain ranging from 0 to 10%. Simulations at a higher irradiation energy of 2–5 keV were used to study the effect of strain on damage cascade evolution. With increasing tensile strain,$$\overline{E}$$_d was reduced from 35 eV at 0% strain to 31 eV at 10% strain. The strain-reduced $$\overline{E}$$_d led to a higher damage peak and more surviving defects (up to 1 ps). Furthermore, high strains induced local cleavage around the cavities, as one additional mechanism of damage enhancement. Experimentally, HOPG film was folded, and the folded region with the maximum tensile stress was irradiated by a 2 MeV proton beam. Raman characterization showed significantly enhanced D to G modes in comparison to the stress-free irradiation. Based on the strain dependence of $$\overline{E}$$_d and the Kinchin–Pease model, a formula for displacement estimation under different tensile strains is proposed. The stress effects need to be considered in graphite applications in a reactor’s harsh environment where both neutron damage and stress are present.

Authors:

Hu, Zhihan; Chen, Di; Kim, SeungSu; Chauhan, Rijul; Li, Yongchang ;

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Shao, Lin

Publication Date:

2022-05-10

Research Org.:

Texas A & M Univ., College Station, TX (United States). Texas A & M Engineering Experiment Station

Sponsoring Org.:

USDOE Office of Science (SC), Basic Energy Sciences (BES)

OSTI Identifier:

1867075

Alternate Identifier(s):

OSTI ID: 1904508

Grant/Contract Number:  

SC0006725

Resource Type:

Published Article

Journal Name:

Materials

Additional Journal Information:

Journal Name: Materials Journal Volume: 15 Journal Issue: 10; Journal ID: ISSN 1996-1944

Publisher:

MDPI AG

Country of Publication:

Switzerland

Language:

English

Subject:

36 MATERIALS SCIENCE; radiation damage; graphite; molecular dynamics simulation; Raman