Primary Study On The Preparation Of Tritium Breeder Material Li₂TiO₃by An In-situ Hydrolysis-phase Transformation Process

Lithium titanate (Li2Ti03) enriched with6Li is considered to be one of the most promising solid tritium breeders because of its reasonable lithium atom density, low activation, excellent chemical stability, good compatibility with structural materials and good tritium release characteristics at low temperatures. At present, Li2Ti03is mainly prepared by solid-state or wet chemical reactions, both synthesis methods using TiO2as main raw material, which, however, increases the cost and results in low homogeneity and poor crystallinity. Therefore, exploring new raw materials and technology for the production of Li2TiO3with small grain size and high specific surface energy has become an intensive research topic. In order to solve this problem, the mechanism for preparation of Li2Ti03by in-situ hydrolysis-phase transformation process was investigated and then the conditions (the dosage of Li, the TiCl4concentration, reaction temperature, holding time, wash condition) for the synthesis of the Li2TiO3were optimized and the prepared samples were characterized by means of XRD, DSC-TGA, SEM, etc., for the purpose of improving the performance of the materials. The experiments and obtained results are reported in this paper.A metastable Li2TiO3procursor in which Li and Ti were chemically combined was synthesized via in-situ hydrolysis-phase transformation process using TiCl4and LiOH-H2O as the raw materials. The samples were subsequently subjected to heat treatment.The optimal synthetic condition were established as follows:for the first program, the feeding Li/Ti molar ratio was1.05times of theoretical Li/Ti molar ratio, reaction temperature was65℃, reaction time was1h, the precipitate washed with washing liquor, the heat treatment was conducted at800℃for6h; for the second program, the feeding Li/Ti molar ratio was1.6times of theoretical Li/Ti molar ratio, reaction temperature was95℃, reaction time was6h, the precipitate left unwashed, the heat treatment was conducted at800℃for6h. After heat treatment, the samples were thoroughly washed with distilled water and then dried in an oven to obtain the Li2Ti03powder samples. The synthesized sample obtained by two program has pure phase, homogeneous composition, and uniform particle size. The average particle size is approximately100-200nm.The sintering characteristics experiments showed that the relative density and themal shrinkage of the Li2TiO3ceramics pellets increased with an increase in temperature. However, sinering time or molding pressure has minor effects on the sinterability of the Li2Ti03ceramics pellets. The binders (PVA) can improve the strength and the surface microstructure of the Li2TiO3pellets, although they may have an effect on the relative densities. The densification behavior of Li2Ti03ceramics pellets was studied and it was concluded that the3wt.%PVA pellets had the highest density and good surface microstructure. The Li2Ti03pellets exhibited a linear shrinkage of14%and was densified to91%of T.D. after the powders compacted at125-150MPa and sintering at1000℃for4h, demonstrating an excellent sinterability.