Radiation endurance in Al2O3nanoceramics

The lack of suitable materials solutions stands as a major challenge for the development of advanced nuclear systems. Most issues are related to the simultaneous action of high temperatures, corrosive environments and radiation damage. Oxide nanoceramics are a promising class of materials which may benefit from the radiation tolerance of nanomaterials and the chemical compatibility of ceramics with many highly corrosive environments. Here, using thin films as a model system, we provide new insights into the radiation tolerance of oxide nanoceramics exposed to increasing damage levels at 600 °C-namely 20, 40 and 150 displacements per atom. Specifically, we investigate the evolution of the structural features, the mechanical properties, and the response to impact loading of Al2O3 thin films. Initially, the thin films contain a homogeneous dispersion of nanocrystals in an amorphous matrix. Irradiation induces crystallization of the amorphous phase, followed by grain growth. Crystallization brings along an enhancement of hardness, while grain growth induces softening according to the Hall-Petch effect. During grain growth, the excess mechanical energy is dissipated by twinning. The main energy dissipation mechanisms available upon impact loading are lattice plasticity and localized amorphization. These mechanisms are available in the irradiated material, but not in the as-deposited films

Modification of SiO2 by Kr and Xe implantations

International audienc

Multiple ion beam irradiation and implantation: JANNUS project

JANNUS (Joint Accelerators for Nano-Science and Nuclear Simulation) is a project designed to study the modification of materials using multiple ion beams and in-situ TEM observation. It will be a unique facility in Europe for the study of irradiation effects and ion beam modification of materials, the simulation of damage due to irradiation and in particular of combined effects. The project is also intended to bring together experimental and modelling teams for a mutual fertilisation of their activities. It will also contribute to the teaching of particle-matter interactions and their applications. JANNUS will be composed of three accelerators with a common experimental chamber and of two accelerators coupled to a TEM

Synthesis of mesoporous amorphous silica by Kr and Xe ion implantation: Transmission electron microscopy study of induced nanostructures

Thermally grown amorphous SiO2 was implanted at room temperature with heavy noble gases Kr and Xe in order to create cavities in the oxide and increase its porosity. The implantation energies were chosen in order to have the same implantation depth for both ions. Although both ions induce bubbles in amorphous SiO2, bubble size and spatial distribution depend upon the ion mass. Moreover, Xe implantation leads to the additional formation of "nanoclusters". Thermal stability of bubbles/cavities depends on the implanted ion. The nucleation of bubbles and nanoclusters in amorphous SiO2 is discussed in terms of ion mobility, gas-defect interactions, and chemical interaction. Bubble growth is shown to occur by a migration and coalescence process

Metal-oxide nanoclusters in Fe–10%Cr alloy by ion implantation

International audienceHigh contents of Al+ and O+ ions were implanted sequentially into high purity Fe–10%Cr alloy thin foils at room temperature. The as-implanted foils were then studied by transmission electron microscopy (TEM) using the conventional TEM, energy dispersive X-ray (EDX), energy-filtered TEM (EFTEM) and high-resolution TEM (HRTEM) methods. In contrast to the conventional precipitate ensemble synthesis by implantation/annealing, the synthesis of clusters took place already at the implantation stage without requiring any subsequent thermal annealing in our case. The observed precipitates with diameters in the range of 3–25 nm were enriched in Al and O. The crystal lattice of precipitates corresponded to a cubic crystallographic structure of aluminium-rich oxide. The precipitate lattice alignment with the matrix was revealed for at least a part of precipitates. The early stage of nucleation outside thermal treatment is discussed in terms of point defect enhanced diffusion ensuring sufficient atomic transport to allow solute atom precipitation

In-situ TEM study of the stability of nano-oxides in ODS steels under ion-irradiation

Oxide Dispersion Strengthened (ODS) ferritic-martensitic steels are considered for nuclear applications as structural components for fusion or fission reactors. To ensure good performances in service, the stability under irradiation of the microstructure and especially of Y-Ti-O nanoclusters have to be assessed. In-situ Transmission Electron Microscopy has been performed to follow the Y-Ti-O nano-oxides dispersed in a Fe18Cr1W0.3Ti + 0.6Y2O3 ODS material under ion-irradiation at 500°C. Microstructural examinations using bright and dark field mode showed that Y-Ti-O nano-precipitates (5 nm) are still present after irradiation up to 45 dpa. However, some larger oxides seem to be more affected by irradiation at 45 dpa (creation of point defects, interface and shape modification)