熔盐法制备三元层状MAX相陶瓷的研究进展

MAX相是一种兼具金属和陶瓷性能的新型三元层状过渡金属碳氮化物。传统合成MAX相的方法都有一定的局限性,如反应温度较高、合成时间过长、合成样品较少,且大部分无法直接一步制备所需MAX相。近些年来,采用熔盐法合成MAX相的报道越来越多,并且工艺持续改进。本文从传统熔盐法合成MAX相出发,分析并阐述了新熔盐法合成MAX相的研究进展。传统熔盐法利用较低熔点的熔盐作为反应溶剂,提高了反应效率;熔盐屏蔽法以熔盐作为反应溶剂的同时还可防止氧化,使得反应可以在空气中进行;路易斯酸盐法则是将熔盐作为反应原料来合成MAX新相;熔盐电化学法以电脱氧的方式,将合成原料由纯金属改为金属氧化物,降低了生产成本。熔盐法所合成MAX相产物较传统方法所合成产物的产量及纯度更高,所需要的温度、能耗以及成本更低。因此,熔盐合成法是未来大批量合成MAX相以及MAX新相合成的一个重要方法。

Research Progress on Synthesis of Ternary Layered MAX Phase Ceramics by Molten Salt Method

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.