Preparation And Properties Of Ti Doped Lithium Orthosilicate Ceramics By Hydrothermal Method

As a tritium breeding material,lithium-based ceramics are mainly used to provide tritium fuel for the deuterium-tritium fusion reaction ceramics.Lithium orthosilicate(Li4SiO4)ceramics has become one of the preferred materials for solid tritium breeding materials because of its high lithium density and good tritium release property.However,the current lithium orthosilicate ceramics prepared by conventional methods have large crystal grains(up to tens of microns),which seriously affect the tritium release properties,mechanical properties and radiation properties of the materials.Grain refinement is considered to be an effective method to improve the comprehensive performance of tritium breeding ceramics,but high-temperature stability of the fine-grained Li4SiO4 ceramics is insufficient,and it is difficult to meet the requirements of service conditions.Based on the existing problems of Li4SiO4 ceramics prepared by existing methods,hydrothermal method combined with wet freezing molding technology was used to design and prepare Li4Si1-xTixO4 solid solution ceramics and Li4SiO4-yTiO2 ceramics by adjusting the composition and sintering parameters of lithium orthosilicate ceramics.This work aims to prepare lithium orthosilicate ceramics with excellent comprehensive performance and high temperature stability,and study the influence of titanium doping on the microstructure,and properties of lithium orthosilicate ceramics,and also reveal the mechanisms.By introducing Ti4+instead of Si4+,Li4S1-xTixO4 solid solution ceramics(average grain size is 7μm)were prepared.The results show that the introduction of Ti4+can reduce the reaction activation energy and increase the reaction rate,but the solute Ti has a very limited influence on the grain growth;With the increase of titanium content,crushing load of the ceramics continue to increase.When the Ti content is x=0.2,the crushing load is increased by nearly 4 times(51.8N vs 9.43N),Ti solid solution can improve the thermal conductivity and ionic conductivity of lithium orthosilicate.When the Ti content is 0.05 and 0.1,the thermal conductivity and ionic conductivity are the highest;The thermal cycle experiment results show that the introduction of Ti4+can improve the high temperature stability of lithium orthosilicate ceramics(the high temperature stability is the best when the Ti doping amount is 0.05),but as the Ti doping amount increases(x>0.05),obvious Ti segregation will occur in ceramics,forming Li2TiO3.Li4SiO4-yTiO2 ceramics(average grain size is 1μm)were prepared by adding TiO2 nanoparticles.The results show that the prepared ceramics are mainly composed of two phases:Li4SiO4 and Li2TiO3;Doping TiO2 particles can significantly inhibit the growth of Li4SiO4 ceramic grains and improve the ceramic crushing load(when y=0.05～0.1,the crushing load is about 25N);doping TiO2 can improve the room temperature thermal conductivity and ionic conductivity of Li4SiO4;The thermal cycle experiment results show that Li4SiO4-yTiO2 ceramics have better high temperature stability than Li4SiO4.