Li2TiO3 pebble fabrication by freeze granulation & freeze drying method

Lithium titanate (Li2TiO3) ceramic is one of the candidate tritium breeding material for fusion reactor. Li2TiO3 in the form of spherical pebbles are kept inside the canisters of the fusion blanket. Prior to pebble fabrication, Li2TiO3 powder was prepared by using Li2CO3 and TiO2 as precursor materials by solid-state reaction method. To make the powder-fine, they were mixed and milled together inside the high energy planetary ball mill followed by calcination at 1000 °C for 5 h. An experimental setup based on the freeze granulation and freeze-drying method was developed in-house, where the green pebbles of 1.5–2 mm were prepared by dropping Li2TiO3 slurry into liquid nitrogen through the 0.6 mm nozzle opening. The pebble drying was performed by the sublimation process at – 60 °C under vacuum followed by the sintering of green pebbles at 950 °C, 1050 °C, and 1150 °C. Various characterizations of the powder and pebbles were carried out to ascertain its phase purity, surface morphology, porosity, pore-size distribution, etc. The results of those characterizations confirm the single-stage reaction, phase purity, desired dimension of pebbles, and their physical and thermal properties. The details of those characterizations along with the dependence of sintering temperatures with the pore size distribution and bulk density of pebbles are discussed in this paper.