Preparation And Characterization Of Li₂TiO₃ Pebbles For Tritium Breeder Blanket In Fusion Reactor

Li₂TiO₃ceramic pebbles are considered to be one of the promising tritium breeder materials for solid tritium breeder in future fusion reactors.Li₂TiO₃ceramic pebbles have the advantages of high mechanical strength,strong tritium release ability and outstanding chemical stability,etc.Li₂TiO₃ceramic pebbles have widely used in test blanket module（TBM）in ITER project,which has a very important research prospect.In order to find a suitable preparation method of Li₂TiO₃ceramic pebbles for the solid tritium breeder in fusion reactor,this paper studied in detail the preparation scheme of Li₂TiO₃powder by sol-gel method,the preparation scheme of Li₂TiO₃pebbles by polymer-assisted precipitation method and the influence of molar ratio of lithium source and titanium source in the raw material on the product properties.In this paper,several groups of xLi₂O·yTiO₂powders were prepared by sol-gel method with different molar ratios of lithium and titanium materials and sintering process.The sol-gel method can be used to prepare powders with uniform particle size and size in the nanometer scale.The prepared powders were characterized in various ways to explore the influence of different sintering processes and raw material lithium-titanium ratio on the product phase and lithium loss rate and other indicators.The results show that the Li₂TiO₃powder prepared with5%excess lithium source has the highest purity.With 1273 K as sintering temperature,the highly crystalline Li₂TiO₃powder can be obtained when the sintering time exceeds 2h.Too low or too high sintering temperature will lead to the increase of miscellaneous products or products reaching the melting point affect the crystallinity.An improved wet polymer-assisted precipitation method was used to prepare Li₂TiO₃ceramic pebbles,which can be used as solid tritium breeder material.The xLi₂O·yTiO₂powders with different lithium-titanium ratios were used as raw material.It is found that the Li₂TiO₃ceramic pebbles prepared with 5%excess lithium source have the best performance.The optimal sintering temperature of Li₂TiO₃ceramic pebbles should be between 1208K and1562K Under this sintering temperature range,the pores inside the pebbles can be eliminated,and the loss of components and the occurrence of crystal transformation can be avoided.According to mechanical test,complete brittle deformation occurs when the sintering temperature is 1473K.With the prolongation of sintering time,the modulus and crushing load increase continuously.The sample sintered at 1473K for 10h showed the best mechanical properties,and the maximum crushing load reached 18N.However,too long sintering time may produce orthorhombic system Li₂Ti₃O₇as impurities,and even when the sintering time exceeds 24h,impurities will replace Li₂TiO₃as the main phase of the product.The sample sintered at 1473K for 10h has the lowest loss rate of lithium（about 5%）while maintaining excellent mechanical properties.In summary,the optimal sintering condition of Li₂TiO₃ceramic pebbles is 1473K for 10h.The average diameter of ceramic pebbles prepared under this sintering condition is 1.2mm,and the sphericity is about 1.05.