Mechanical properties of thermally stable cadmium iodoapatite ceramic by reactive spark plasma sintering technique

Abstract

Apatites based materials have been considered as potential waste forms to immobilize the long-lived radioactive iodine isotope. But the thermal instability and phase decomposition at a higher temperature hamper the waste management process. Spark plasma sintering can be a suitable technique compared to conventional sintering processes due to its rapid heating rate, lower sintering temperature and holding time. In this study, we synthesized a highly dense iodine bearing cadmium iodoapatite ceramic pellets by spark plasma sintering (SPS) technique. We successfully consolidated iodoapatite pellets with ~95.5% of theoretical density (TD) without any iodine loss and phase decomposition after low temperature sintering at 350 o C for 15 mins under 100 MPa. The theoretical density, micro-hardness, and yield strength of sintered pellets were investigated for different sintering temperatures of 300 o C, 350 o C, and 400 o C and holding time (15 min) under the pressure of 100 MPa. The densified pellets displayed nanocrystalline grain structures of 30-80 nm size which contributed to enhanced thermal stability and fracture toughness. The X-ray diffraction and EDS analysis also confirms the presence of iodoapatite structures. This advanced fabrication technique using SPS can help to develop thermally durable waste forms and mitigate the challenges to dispose high-level radioactive waste.

Radiation-Induced Grain Growth of Nanocrystalline AlxCoCrFeNi High-Entropy Alloys

“…High-entropy alloys (HEAs) are composed of four or more metallic elements mixed in an equimolar or near-equimolar ratio to form a solid solution. , HEAs exhibit good properties, including high elevated-temperature strength, , low-temperature toughness, excellent wear, , as well as corrosion , and oxidation resistance, which showed the possibility of being structural materials − for nuclear reactors. However, to be nuclear materials, a fundamental requirement is to endure high irradiation dose. − The mixing of elements results in the possibility of achieving an extremely high irradiation resistance via unique damage-healing mechanisms, − compared to a large number of crystal defects in traditional materials in the radiation condition. In addition, the lack of bubbles and the resistance to void swelling make the HEAs show significant promise as nuclear structural materials.…”