Atomic-scale design of radiation-tolerant nanocomposites
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troduction Structural materials used in nuclear reactors must withstand some of the harshest conditions met in existing technology. All of the factors limiting their lifetime and performance at high temperatures and in corrosive media, such as creep and stress corrosion cracking, are exacerbated by irradiation.1,2 These materials are also subject to degradation by mechanisms distinctive to radiation environments, such as volumetric swelling and anisotropic growth.3,4 Decades of traditional alloy development have yielded incremental enhancements in materials performance under irradiation.5 Advanced fission and future fusion reactor designs, however, call for far more dramatic progress, such as materials able to sustain radiation doses up to 10 times higher than in current reactors while withstanding liquid metal corrosion6 or being implanted with up to several atomic percent of helium.7 The last several decades have also witnessed major advances in our understanding of the atomic-scale origins of material behavior under irradiation8,9 thanks to improvements in experimental techniques such as high-resolution transmission electron microscopy and atom probe tomography (APT), as well as computer modeling techniques such as classical potential molecular dynamics (MD) and density functional theory. This knowledge provides a foundation for the emergence of first-principles, atomic-scale design of materials for radiation resistance.
In contrast to purely hit-and-miss materials development, atomic-scale design aims to achieve superior radiation response by purposefully manipulating composition and microstructure to control the behavior of radiation-induced defects. It relies on modeling to determine the impact of these modifications on engineering-level material behavior. Atomic-scale design is being used today to accelerate the improvement of existing materials. In the longer term, however, it seeks to realize unconventional materials that could not have arisen through a series of gradual modifications. Although only fledgling in the area of structural materials, atomic-scale design has already shown success in other energyrelated fields, such as the search for novel battery electrode materials.10 (See the article by Gerbrand Ceder in the September 2010 issue of the MRS Bulletin.) This article illustrates how atomic-scale design for radiation resistance is being pursued in the tailoring of radiation-resistant interfaces, design of stable microstructures, and development of nanostructured ferritic alloys (NFAs). Challenges facing this approach to materials engineering are also discussed.
Atomic-level origin of radiation damage The topic of radiation effects in structural materials encompasses a vast literature dating from 194211 and cannot be fully reviewed in this article. It is well understood, however, that the root causes of radiation damage are individual and clustered
M.J. Demkowicz, Massachusetts Institute of Technology, Cambridge, MA 02139, USA; [email protected] P. Bellon, University of Illinois at Urbana-Champaign, Urba
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