Li4SiO4 breeder pebbles fabrication by a sol-gel supported drip casting method

Abstract

Lithium orthosilicate (Li4SiO4) is widely considered a potential candidate as tritium breeding material for blankets in thermonuclear fusion reactors. In this study, a low-temperature methodology based on the drip casting forming technique was proposed for Li4SiO4 pebbles fabrication. The hydrolytic sol-gel method (starting from tetraethyl orthosilicate and lithium hydroxide) was applied to synthesize Li4SiO4 precursor powders, which were used to prepare an aqueous suspension for dripping in calcium chloride/lithium acetate solution. Spherical Li4SiO4 pebbles were obtained after sintering (900-950°C) and exhibited regular roundness, high phase purity, and no macroscopic defects. A high density (> 70 % of the theoretical Li4SiO4 density) and a good crush load (35 N) were achieved when cellulose fibers were added to the precursor suspension and the sintering step was conducted up to 950°C. Results indicate that the produced Li4SiO4 pebbles can be suitable for the use in breeding blankets in future fusion reactors.