Speaker
Description
The realisation of the breeding blanket system represents one of the crucial points in the design of future generation fusion reactors. At the time being, problems regarding materials compatibility persist. To protect structural materials from the harsh environment of breeding blankets, different materials have been studied as corrosion-resistant, anti-permeation coatings. Among them, Yttrium Oxide (Y2O3) has been proposed, mainly due to its structural and thermodynamic stability (no crystalline transition up to 2350°C and no reduction in the presence of Lithium). Still, traditional Y2O3 films present some drawbacks, like porosity and inhomogeneity, which are detrimental for their application as efficient barriers. Here, we report on advanced Yttrium Oxide coatings deposited by Pulsed Laser Deposition (PLD) technique. Deposited films appear dense, compact and well adherent, without defects. The adhesion is verified through mechanical stress and thermal fatigue. Morphological and crystalline features are evaluated in the case of as-deposited and annealed samples. A deep characterization is performed by Scanning Electron Microscopy (SEM), Energy Dispersive X-ray (EDX), Fourier Transform Infrared spectroscopy (FTIR) and X-ray Diffraction (XRD). The mechanical properties of PLD-grown Yttria are measured with an innovative approach, combining Nano-Indentation and Brillouin spectroscopy. The ceramic material appears quasi-ductile (stiffness comparable to traditional steel) with metal-like behaviour and a remarkable H/E parameter. The electrical characteristics are verified with impedance tests, showing resistance values similar to the ones found in literature (largely above the requirements for breeding blanket insulating coatings). The chemical compatibility of Y2O3 films is tested in the presence of molten Pb-16Li eutectic, showing no degradation, nor corrosion of the steel substrates. At last, preliminary permeation tests suggest the potential of the coating to act as an excellent H2 permeation barrier. To conclude, in this work we present a novel multifunctional Y2O3 coating as a promising candidate for future fusion nuclear systems.
