Abstract: MAX phases are a kind of new ternary layered transition metal carbonitrides, which possesses the advantages of both metal and ceramic materials. Traditional methods for synthesizing MAX phases have some limitations, such as higher temperatures, longer reaction time, few synthetic samples, and most required MAX phase can not be directly prepared by one-step. In recent years, there are more and more reports about the synthesis of MAX phases by molten salt method, and its process is continuously improved. In this paper, based on the traditional molten salt synthesis of MAX phase, the research progress of the new molten salt synthesis of MAX phase is analyzed and described. In the traditional molten salt method, the molten salt used as reaction solution with a lower melting point is used as reaction solution, thus the reaction efficiency can be improved. In molten salt shielded method, the molten salt used as reaction solution can prevent the oxidation of raw materials, so that the synthesis process can be carried out in air. Lewis acidic salt method uses molten salt as raw material to synthesize MAX phases. In the molten salts electrochemical method, the raw material changes from pure metals to metal oxides by electro deoxidation, so the cost can be reduced. In summary, the products synthesized by molten salt methods have higher yield and purity, lower reaction temperatures and costs than those synthesized by traditional methods. Therefore, the molten salt method is suitable for the large-scale syntheses of MAX phases in the future.

Key words: MAX phase, synthesis, molten salt method, molten salt shielded method, Lewis acidic salt method, molten salt electrochemical method, two-dimensional material