Basic Research On The Preparation Of High-purity TiSi₂ From Si-Ti Alloy By Electromagnetic Directional Solidification

Ti-bearing blast furnace slag is not only industrial waste,but also an important titanium resource.At present,the preparation of Si-Ti alloy by silicon thermal reduction using Ti-bearing blast furnace slag as raw material is an effective method for recovering titanium,but the prepared Si-Ti alloy is only used as alloying agent and deoxidizer in steel smelting.In addition,impurity elements such as Fe and Mn limit the application of Si-Ti alloy.In this study,Si-Ti alloy obtained by silicothermic reduction of Ti-bearing blast furnace slag,and then separated and purified by electromagnetic directional solidification technology to prepare TiSi₂and eutectic Si-Ti alloy.TiSi₂is expected to become a high-temperature structural material,and can also be used as materials for interconnects,diodes,and ohmic contacts.Eutectic Si-Ti alloy(Si/TiSi₂)is expected to become a high-capacity anode material for Lithium-ion batteries.The method proposed in this paper to separate and purify Si-Ti alloy to prepare TiSi₂and eutectic Si-Ti alloy can effectively expand the application field of Si-Ti alloy,and also provide a new method for efficient utilization of Ti-bearing blast furnace slag.Firstly,the Si-Ti alloy prepared by silicothermic reduction of Ti-bearing blast furnace slag is the research object,and then the experimental study on the preparation of TiSi₂and eutectic Si-Ti alloy by the separation and purification of Si-Ti alloy by electromagnetic directional solidification was carried out.The experimental results show that under the conditions of argon atmosphere,MgO crucible as reaction vessel,no fluxing,and melting temperature of 1823K,the reduction rate of Ti can be more than 95%in the process of silicothermic reduction of Ti-bearing blast furnace slag.When using crucibles of different material(MgO crucible,Al₂O₃crucible and graphite crucible)electromagnetic directional solidification separation and purification of Si-Ti alloy to prepare TiSi₂and eutectic Si-Ti alloy,MgO crucible is more suitable as a kind of reaction vessel for the separation of Si-Ti alloy by electromagnetic directional solidification to prepare high purity TiSi₂(>98%)and eutectic Si-Ti alloy(>97%),most of impurity elements(Fe,Mg,Ca,Mn,Ni and Al,etc.)can also be removed simultaneously.In addition,the obtained eutectic Si-Ti alloy is recycled as a reducing agent and can be continuously used to reduce Ti-bearing blast furnace slag to obtain Si-60.16wt%Ti alloy with higher Ti content.Then,in order to strengthen the separation process of Si-Ti alloy by electromagnetic directional solidification and obtain dense bulk TiSi₂alloy,the experimental study on the separation of Si-Ti alloy by electromagnetic directional solidification was carried out under the condition of graphite crucible of different size and output induced current.The results show that the larger the graphite crucible size(the maximum inner diameter is 32±1mm,the outer diameter is 42±1mm,and the height is 50±1mm)or the larger the output current(the maximum current is 51A),the agglomerated TiSi₂crystals at the bottom of the sample are denser.The mass fraction of TiSi₂crystals in the TiSi₂enriched layer is 99.66%(Si content is 0.34%)and96.81%(Si content is 3.19%)In addition,in order to strengthen the removal of impurities in TiSi₂alloy,Si-39.6wt%Ti alloy prepared by silicothermic reduction of Ti-bearing blast furnace slag is the research object,and the experimental study on the preparation of high-purity TiSi₂crystal by Si-Ti alloy solvent refining coupled with electromagnetic directional solidification was carried out.The results show that the removal rate of impurity elements(Fe,Mn,Ni,Mg,Al and Ca)in the TiSi₂enrichment layer at the bottom of Si-39.6wt%Ti alloy increases obviously with the increase of alloy solvent(industrial silicon)content from 13.4%to 32.2%.In other words,alloy solvent refining method can improve the removal rate of impurities in TiSi₂alloy,so that the purity of the alloy can reach up to 99.33%.