Low temperature fabrication of lithium metatitanate and lithium orthosilicate combinatory ceramics for fusion breeding applications

Nuclear fusion could one day satiate the world’s thirst for energy. However, significant hurdles need to be surpassed to arrive at a functional fusion device. All components of a theoretical reactor must be designed with those hurdles in mind. One such component is the breeder blanket, functioning as both fuel — via the transmutation of lithium into tritium — and as a heat recovery system, transferring the kinetic energy of neutrons into usable heat. To this end, a variety of materials have been proposed to function as breeders, but currently ceramic breeders are leading the charge. Out of the many materials considered, two ceramics are generally understood to be the most suitable solutions: Li2TiO3 and Li4SiO4.
Lithium containing materials suffer during fabrication as common methods require high temperatures, which results in lithium loss via vaporisation. This project aims to introduce novel, low-temperature fabrication methods to address this issue and expand the available pathways for ceramic breeder fabrication. In particular, the application of reactive cold sintering (RCS) allows for the facile introduction of different phases, which may enable the tailoring of ceramics composites.
In this project, single phase Li2TiO3 has been synthesised using the DES method. Moreover, cohesive, single phase and multiphase pellets were generated applying the reactive cold sintering method. The capacity for this method to introduce different morphologies and phases through the use of the infill as an independent vector was demonstrated. Dense, single phase Li2TiO3 pellets were produced with maximum temperatures 400 °C below those used in regular sintering. Biphasic, Li 4SiO4 – Li2TiO3, pellets were generated, resulting in exceptionally well-consolidated composites. Incompatibilities between the equipment and the materials used led to unpredictable shifts in stoichiometry, which ultimately led to sub-stoichiometric lithium content in the final pellets. This resulted in complex mechanisms leading to the sequestration and eventual retention of unreacted material.