Abstract: The MAX phase Ti2SC is a potential high-temperature structural material and precursor for titanium extraction by molten salt electrolysis due to its special structure and properties. However, the existing preparation methods all involve the use of high-value Ti powder, TiC powder, and TiS powder, since the synthesis of Ti2SC has always been thought to be through the reaction of TiC and TiS. The preparation of high-purity Ti2SC in a low-cost way is the prerequisite for its large-scale application. In this work, with ilmenite concentrate, pyrite, and graphite spherical tailings as the raw materials, high-purity Ti2SC was successfully prepared via the carbo-sulfidation of ilmenite concentrate. Since it was a new reactant system for preparing Ti2SC, the formation mechanism of Ti2SC in the FeTiO3/FeS2/C system was discussed in detail based on the results of XRD and thermodynamic calculation. A new formation mechanism that Ti3O5, the intermediate product of carbothermal reduction of FeTiO3, was directly reconstructed into Ti2SC in the molten FeS was proposed. Then, the effects of graphite proportion, sintering temperature, and holding time on the purity and morphology of products were determined by the orthogonal experiment. Ti2SC with uniform size and purity of up to 96wt% was obtained from the sample containing 27.4wt% graphite after sintering at 1400℃ for 4 h and subsequent pickling treatment continued based on the results of XRD fine-fitting data and SEM. Furthermore, to reduce the amount of acid used in the purification process, the in-situ physical separation of by-product Fe and Ti2SC was realized under 1700℃ high-temperature sintering by taking advantage of the large density difference between Ti2SC and molten Fe. The amount of acid used for purification was reduced by 72.7% according to the comparison of theoretical and actual acid consumption. The results of this study not only proposed a new pathway to synthesize Ti2SC but also provided valuable references for the industrial production of this MAX phase.

Key words: ilmenite concentrate, carbo-sulfidation, MAX phase, Ti2SC, high purity, in-situ physical separation

摘要： 含硫MAX相Ti2SC被认为是很有潜力的高温结构材料及熔盐电解提钛前驱体。但现有制备方法均涉及高值Ti粉、TiC粉及TiS粉的使用，难以实现其规模化应用。本工作以钛精矿为钛源，黄铁矿为硫源，石墨球形尾料为碳源，探索了碳热硫化钛精矿低成本制备高纯Ti2SC的可行性。研究了FeTiO3/FeS2/C体系中Ti2SC的形成机理；石墨添加量、烧结温度与烧结时间对产物纯度与形貌的影响规律；高温原位物理分离副产物Fe对提纯过程酸用量减少的实际占比。结果表明，Ti2SC生成的关键反应是FeTiO3碳热还原中间产物Ti3O5在熔融FeS中直接脱氧重构为Ti2SC；石墨添加量27.4wt%的试样经1400℃下烧结4 h及后续酸洗处理，可以得到纯度大于96wt%的Ti2SC；1700℃下的高温烧结可以实现部分副产物Fe与Ti2SC的分离，酸洗提纯过程酸用量减少72.7%。该方法有望实现高纯Ti2SC的规模化制备。

关键词: 钛精矿, 碳热硫化, MAX相, Ti2SC, 高纯度, 原位物理分离