Migration and aggregation of ruthenium implanted in glassy carbon

Abstract

Glassy carbon is a continuous, isotropic and non-graphitizing carbon that combines the properties of glass and ceramic with those of graphite. It has excellent properties such as high tensile strength, high hardness, good thermal and electrical conductivity, and combined resistance to high temperatures, wear, and corrosion. Glassy carbon is also highly impermeable to gases and liquids. These outstanding properties of glassy carbon make it a good choice for nuclear applications. Glassy carbon has been proposed as a containment material for radioactive fission products. For glassy carbon to be considered a suitable candidate for fission products containment, it must be an effective diffusion barrier for fission products, such as ruthenium (Ru), and its microstructure should not change dramatically under ion bombardment and extreme heat conditions. In summary, this study thoroughly investigated the impact of implantation and annealing temperatures on the microstructure and migration behaviour of Ru implanted in glassy carbon, with a focus on assessing its suitability as a diffusion barrier for Ru fission products. Raman and XRD results revealed amorphization of glassy carbon and structural changes induced by ion bombardment and subsequent annealing, showcasing the transition from tensile to compressive stress. RBS and SIMS elucidated Ru migration, with notable aggregation and segregation at higher annealing temperatures. Remarkably, both low and high-temperature annealing did not lead to significant Ru loss, affirming glassy carbon's efficacy as a storage container for Ru. Surface analyses through SEM and AFM showed a reduction in roughness post-implantation, while annealing-induced variations in roughness were linked to Ru migration or aggregation, surface diffusion and cluster formation. This comprehensive investigation provides valuable insights into Ru migration in glassy carbon, laying the foundation for its potential application as an effective diffusion barrier for Ru fission products.