Abstract
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.
Highlights
The lack of suitable materials solutions stands as a major challenge for the development of advanced nuclear systems
We report the evolution of the nanometer-scale structural features and the mechanical response of Al2O3 nanoceramic thin films as a function of radiation-induced grain growth
The Bright-Field Transmission Electron Microscopy (TEM) micrographs shown in Fig. 1 display the nanostructure of the as-deposited Al2O3 thin films
Summary
The lack of suitable materials solutions stands as a major challenge for the development of advanced nuclear systems. Most of these coolants are extremely corrosive and detrimental to the reliability of in-core components[7], and their inherently corrosive effects are augmented by high temperatures and radiation damage[8] In this context, ceramics represent a promising class of materials due to their high temperature strength, and due to their chemical inertness in several corrosive environments. In order to ensure the longevity of structures, an ideal coating must be designed to withstand unparalleled radiation damage levels On account of their fine grain size, nanoceramic coatings may benefit from the strength and chemical inertness of ceramics, combined with many favorable deformation modes[14,15,16] and with the generally high radiation tolerance demonstrated in nanomaterials[17,18,19,20,21,22,23,24]
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