Characterization of irradiation defect structures and densities by transmission electron microscopy
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Xiaoou Yi Department of Materials, University of Oxford, Oxford OX1 3PH, UK; and EURATOM/CCFE Fusion Association, Culham Science Centre, Abingdon, Oxfordshire OX14 3DB, UK
Michael Jenkins Trinity College, University of Oxford, Oxford OX1 3BH, UK (Received 13 October 2014; accepted 13 January 2015)
We describe aspects of transmission electron microscopy (TEM) technique to image and quantify the defect state following neutron or ion irradiation with an emphasis on experimental considerations. After outlining various neutron and ion irradiation scenarios, including some sample preparation suggestions, we discuss methods to measure defect densities, size distributions, structures, and interstitial or vacancy nature. The importance of the image simulations of Zhou is suggested for guidance to the most accurate quantification of the defect state. It is hoped that the usefulness of the present paper will be greatest for those experiments that compare defect states in materials after different irradiation conditions, or especially those studies designed to benchmark advanced computer model simulations of defect production and evolution. The successful simulation of the defect state in bulk samples neutron irradiated to high dose at high temperature is a goal to which the suggestions in this paper can contribute.
I. INTRODUCTION
The study of irradiation-produced defects and microstructure by transmission electron microscopy (TEM) has a long history dating back to the late 1950s and early 1960s. A remarkable aspect of this history is the fact that the most useful TEM techniques have changed rather little over this time. Diffraction contrast has proven better suited to imaging irradiation defects than the more recent highresolution methods. The central reason for this is that diffraction contrast, especially as practiced using weakly diffracting beams, is more suited to resolving defect structures by imaging strong contrast from the distorted lattice near the defect and suppressing the contrast from the surrounding matrix. Whereas images produced using the major high-resolution techniques are dominated by the undistorted atomic structure and the defect structure is usually observed as a weak perturbation on the perfect atomic structure. Few radiation-damage defects satisfy the condition for a successful structural determination by high-resolution electron microscopy (HREM), that is, the specimen may be necessarily thin (,20 nm) and oriented such that columns of atoms passing through or close to the defect line up in projection along the beam direction. Contributing Editor: Djamel Kaoumi a) Address all correspondence to this author. e-mail: [email protected] DOI: 10.1557/jmr.2015.19 J. Mater. Res., 2015
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With renewed interest in nuclear power and the need for new materials to improve reactor lifetime costs by resisting material property degradation due to the bombardment by neutrons over long periods of time, the study of the response of new alloys to irradiation has again
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