Preparation of tritium breeding Li₂TiO₃ ceramic pebbles via newly developed piezoelectric micro‐droplet jetting

Abstract

Wet methods as an emerging technique for the preparation of millimeter‐sized tritium breeding ceramic pebbles, but the imposed air pressure as the driving forces to extrude slurry droplets are fluctuating during the reciprocating extrusion process, which caused a slight inconsistency in pebble sizes. In this study, a piezoelectric micro‐droplet jetting approach was proposed by introducing a piezo‐driven valve and modifying the slurry barrel mechanism to realize the air pressure invariable. A self‐developed piezoelectric micro‐droplet jetting device was successfully utilized to prepare Li2TiO3 green pebbles with coefficients of variation being lower than 2.7%. The size of the green pebbles could be precisely controlled in the range of 0.88–1.37 mm by manipulating the nozzle diameter, the air pressure, and the jetting time. The pebbles sintered at 1000°C for 3 h possessed a small grain size of ∼5.9 μm, a satisfied relative density of ∼84.8% T.D., and a high crush load of ∼25.7 N, implying the prepared pebbles could be used as a promising solid tritium breeding material in fusion reactors. These findings are anticipated to provide new opportunities for the highly efficient preparation of size‐controllable tritium breeding ceramic pebbles.

One‐step fabrication of Li2TiO3 ceramic pebbles using pulsed YAG laser

“…The mean crush loads of the pebbles fabricated with 6.9 and 7.9 J input conditions were 7.7 ± 4.7 N ( n = 20) and 5.6 ± 2.8 N ( n = 18), respectively. These values were low compared with the Li 2 TiO 3 pebbles fabricated by the other methods and similar to those of Li 4 SiO 4 –Li 2 TiO 3 biphasic pebbles fabricated by melt process; the crush loads of Li 2 TiO 3 pebbles by emulsion method, 34 Li 2 TiO 3 pebbles by piezoelectric microdroplet jetting, 11 Li‐rich Li 2 TiO 3 pebbles by rolling method, 35 and Li 4 SiO 4 –Li 2 TiO 3 pebbles by melt process 24 are 37.2, 25.7, 10–41, and 5–15 N. Crush load of the pebbles could be improved by an additional heat treatment and/or compositional modification, as reported in the previous studies 22,36 . Particularly, an addition of Li 2 CO 3 to the initial powder as a sintering aid may contribute both to densification and increase of Li/Ti ratio 37 …”

“…Several techniques have been proposed for the fabrication of ceramic breeder pebbles. The wet process [9][10][11][12] is a well-established method which can produce spherical green pebbles by dropping a liquid mixture of Li 2 TiO 3 and polyvinyl-alcohol through a nozzle. In the emulsion method, [13][14][15] green pebbles with a narrow size distribution are produced by cutting the Li 2 TiO 3 slurry flow with oil flow in a T-shaped flow path.…”