Irradiation and Annealing Effects on the <i>c</i>-Axis Electrical Resistivity of Graphite

Iwata, Tatsuya; Nihira, Takuya; Matsuo, Hideto

doi:10.1143/jpsj.36.123

Cited by 18 publications

(9 citation statements)

References 12 publications

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“…The former is due to electron scattering by defects disrupting in-plane bonding and the latter is due to the extra coupling between layers from the interlayer bonds [22]. A longstanding enigma has been that annealing cryogenic (liquid Ne or He) radiation damage does not restore resistivity monotonically to its original values, but rather causes the radiation-induced trends to proceed in the same direction, as if radiation were continuing, in the early stages of annealing [26,27]. There have been attempts to interpret this phenomenon as initial aggregation of interstitials into small clusters which can break up as the temperature is raised.…”

Section: Introductionmentioning

confidence: 99%

Buckle, ruck and tuck: A proposed new model for the response of graphite to neutron irradiation

Heggie

Suarez-Martinez

Davidson

et al. 2011

Journal of Nuclear Materials

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The default theory of radiation damage in graphite invokes Frenkel pair formation as the principal cause of physical property changes. We set out its inadequacies and present two new mechanisms that contribute to a better account for changes in dimension and stored energy. Damage depends on the substrate temperature, undergoing a change at approximately 250 °C. Below this temperature particle radiation imparts a permanent, nano-buckling to the layers. Above it, layers fold, forming what we describe as a ruck and tuck defect. We present first principles and molecular mechanics calculations of energies and structures to support these claims. Necessarily we extend the dislocation theory of layered materials. We cite good experimental evidence for these features from the literature on radiation damage in graphite. © 2011 Elsevier B.V. All rights reserved

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Section: Introductionmentioning

confidence: 99%

Buckle, ruck and tuck: A proposed new model for the response of graphite to neutron irradiation

Heggie

Suarez-Martinez

Davidson

et al. 2011

Journal of Nuclear Materials

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“…The mechanical and electrical properties of graphite, as well as other forms of nanostructured carbon and graphene, can be substantially altered through irradiation [1][2][3]. In the case of graphite, irradiation (with neutrons, electrons, or ions) causes changes to electrical resistance and thermal conductance [2,4,5] and anisotropic changes to both elastic properties and the crystal dimensions, together with expansion in the prismatic direction, balanced by shrinkage in the basal plane [6,7]. These changes arise from a complex evolution of a population of point defects in the graphite structure (Frenkel pairs of lattice vacancies and self-interstitials created when impacting energetic particles displace atoms) into prismatic and basal dislocations [8] and other interstitial and vacancy aggregates [9][10][11].…”

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confidence: 99%

Extended Interplanar Linking in Graphite Formed from Vacancy Aggregates

et al. 2013

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The mechanical and electrical properties of graphite and related materials such as multilayer graphene depend strongly on the presence of defects in the lattice structure, particularly those which create links between adjacent planes. We present findings which suggest the existence of a new type of defect in the graphite or graphene structure which connects adjacent planes through continuous hexagonal sp 2 bonding alone and can form through the aggregation of individual vacancy defects. The energetics and kinetics of the formation of this type of defect are investigated with atomistic density functional theory calculations. The resultant structures are then employed to simulate high resolution transmission electron microscopy images, which are compared to recent experimental images of electron irradiation damaged graphite. The rich variety of structures and topologies that result from the ways that carbon atoms can bond with each other provides us with a multitude of opportunities and challenges. A particularly important problem concerns the response of graphite to damaging radiation, especially where it forms the neutron moderator and reflector blanket in a nuclear fission reactor. In this application, it is essential for the structural integrity of the material to be maintained for decades in a harsh, inaccessible environment. The mechanical and electrical properties of graphite, as well as other forms of nanostructured carbon and graphene, can be substantially altered through irradiation [1][2][3]. In the case of graphite, irradiation (with neutrons, electrons, or ions) causes changes to electrical resistance and thermal conductance [2,4,5] and anisotropic changes to both elastic properties and the crystal dimensions, together with expansion in the prismatic direction, balanced by shrinkage in the basal plane [6,7]. These changes arise from a complex evolution of a population of point defects in the graphite structure (Frenkel pairs of lattice vacancies and self-interstitials created when impacting energetic particles displace atoms) into prismatic and basal dislocations [8] and other interstitial and vacancy aggregates [9][10][11]. The processes involved occur over many time and length scales, and the fundamental mechanisms behind the observed property changes are still unresolved, even after 70 years of intensive research.One of the most useful experimental insights into the evolution of the graphite structure under irradiation comes from high resolution transmission electron microscopy (HRTEM) images [12]. This method can resolve prismatic edge and basal dislocations in the graphite structure when viewing along the c axis (i.e., perpendicular to the planes) and the topology of individual layers and prismatic edge dislocations when viewing along the planes (side on) [13]. HRTEM images typically show evidence for the rupturing and bending of the planes [14,15] as well as dislocation climb and the growth of new planes under irradiation [16]. However, the atomistic mechanisms driving these processes are not re...

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“…It arises from the formation of a metastable mutually trapped I-V configuration as they approach one another, which we term an intimate Frenkel pair. The existence of such a defect in graphite has previously been indirectly inferred [10], but its structure has never before been studied nor has it been linked with Wigner energy release.…”

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confidence: 99%