Nano-Sized Zirconium Carbides: Synthesis, Characterisation and Irradiation
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0908-OO04-05.1
Nano-sized zirconium carbides: synthesis, characterisation and irradiation Mickaël Dollé1, Dominique Gosset1, Christine Bogicevic2, Gianguido Baldinozzi2, Fabienne Karolak2, David Simeone1 1 2
CEA Saclay, DMN/SRMA, F-91191 Gif/Yvette, France SPMS, ECP, F-92295 Chatenay Malabry, France
ABSTRACT The projects of development of a new generation of nuclear plants with improved yield and drastical reduction of waste production makes it necessary the development of materials able to withstand high temperature (1000-1200°C) in normal conditions. For this, new materials such as the refractory transition metal carbides are considered. However, these materials are brittle. A possible way to improve their mechanical properties is to elaborate materials with nano-sized grains. We have then undertaken the elaboration of such materials in order first to compare their behaviour under irradiation with classical, micro-sized ones. As a result, nano-sized powders have been obtained by a sol-gel method and high density materials have been elaborated by two different routes to be compared to micro-sized ones. A simulation of a neutron irradiation has been obtained with low energy heavy ions irradiation. Consequently, the resulting damaged material has a low thickness (100200 nm), requiring surface analysis methods. We present here the results we have obtained using a grazing incidence X-ray diffraction method. The micro-sized materials show a linear volume swelling in the range 20-40 Zr dpa. Nano- and micro-sized materials both show high internal distortions. INTRODUCTION Nano-sized grain materials have shown recently an increasing interest explained by the possibility of new properties, which arise for example from the absence of extended defects in the particles [1]. In fact, unusual mechanical properties are expected for such materials in which the usual characteristic distance between defects (e.g. dislocations) is higher than the grain size and then the proportion of atoms involved in grain boundaries is no longer negligible as compared to the bulk material ones. Controlling the properties of the grain boundaries then leads to new properties such as superplasticity [2] or toughening even in the case of brittle matrix materials. The development of a new generation of nuclear reactors (Gen-IV project [3]), with improved thermodynamic yield and a drastical reduction of waste production, makes it necessary to consider new materials able to withstand very high temperatures (1000-1200°C in normal conditions, up to 1500°C in incidental ones). Moreover, in the case of fast-neutron reactors to be used for nuclear waste burning, low-Z materials can no longer be used due to too high neutron slowing-down efficiency. Compounds, among which the transition metal carbides ZrC and TiC, are then to be considered. Those materials are highly refractory, have good thermal conductivity [4], low neutron absorption or scattering cross sections, low damage under irradiation [5]. Unfortunately, they have a brittle mechanical behaviour. We
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