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Advanced AlO3 coatings under extreme conditions - EMIR

Advanced AlO3 coatings under extreme conditions
Francisco Garcia Ferre1, Alexander Mairov2, Cedric Baumier3, Odile Kaitasov3, Dario
Gastaldi4, Pasquale Vena4, Patrick Trocellier5, Yves Serruys5, Lucile Beck5, Kumar
Sridharan2, Marco G. Beghi6 and Fabio Di Fonzo1
Center for Nanoscience and Technology, Istituto Italiano di Tecnologia,Via G. Pascoli 70/3, 20133
Milano (MI), Italia
Department of Engineering Physics, University of Wisconsin-Madison, Madison, WI 53706, USA
CNRS/IN2P3/CSNSM/SEMIRAMIS, Université Paris Sud, Bat 108, 91400 Orsay, France
Dipartimento di Chimica, Materiali e Ingegneria Chimica, Politecnico di Milano, Piazza Leonardo Da
Vinci 2, 20133 Milano (MI), Itaia
Service de Recherches de Metallurgie Physique, Laboratoire JANNUS, CEA, DEN, F-91191, Gif-SurYvette, France
Dipartimento di Energia, Politecnico di Milano, Via Ponzio 34/3, 20133 Milano (MI), Italia
[email protected]
In future generation nuclear systems cooled by Heavy Liquid Metals (HLMs), such as lead or leadbismth eutectic (LBE), fuel cladding will be exposed to an extremely harsh environment, in which
radiation dose will approach 150 displacements per atom (dpa) at a temperature of up to 800°C. In
addition, corrosion of structural steels by HLMs stands as a major bottleneck.
In this work, we propose the use of a nanocrystalline Al 2O3/amorphous Al2O3 composite coating as a
corrosion barrier for high temperature operation of steels in HLMs [1]. The barrier layer is grown by
Pulsed Laser Deposition (PLD) at room temperature. The mechanical properties of the coating are
assessed with high accuracy and precision trough a novel opto-mechanical method [2], based on the
combination of ellipsometry, Brillouin spectroscopy and nanoindentation. The adhesive strength is
evaluated by nanoscratch tests. The coating attains an unusual combination of compactness, strong
interfacial bonding, moderate stiffness (E=195±9 GPa and ν=0,29±0,02) and significant hardness
(H=10±1 GPa), resulting in superior plastic behavior and a relatively high ratio of hardness to elastic
modulus (H/E=0,049). These features are correlated to the nanostructure of the coating, which
comprises a regular dispersion of ultra-fine crystalline Al2O3 nano-domains (2-5 nm) in a dense and
amorphous alumina matrix. Corrosion aspects are examined by short- and mid-term exposure of
samples to stagnant HLMs at 600°C. Post-test analysis reveal no signs of corrosion, confirming the
strong chemical inertia of the coatings [1]. The performance of the alloy substrate-ceramic coating
system under high dose radiation damage is studied by irradiation with heavy ions up to 20, 40 and
150 dpa at 600°C. Structural features and mechanical properties are evaluated respectively by in-situ
and ex-situ TEM analysis and nanoindentation.
[1] F. García Ferré, M. Ormellese, F. Di Fonzo, M.G. Beghi. Corros. Sci. 77 (2013), 375.
[2] F. García Ferré et al. Acta. Mater. 61 (2013), 2662.
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