改进熔盐隔离法制备核壳结构SiC@C粉体及其合成机制

Preparation of Core–Shell SiC@C Powder via Modified Molten Salt Shielding Technique

鳞片石墨的水润湿性掣肘了其在耐火浇注料中的应用,用碳化物对石墨改性是解决该问题的较佳方法。针对碳化物改性石墨制备过程中成本高、规模化困难,合成机制不清楚等问题入手,本工作采用改进的熔盐屏蔽技术,在空气中制备了核壳型Si C@石墨粉体,研究了坯体封装工艺对熔盐隔离法合成核壳结构Si C@石墨粉的物相组成及显微形貌的影响。结果表明:以Si粉和鳞片石墨粉为原料,用熔盐封装和无盐封装隔离法合成的核壳结构Si C@C粉体具有较好的水润湿性、分散性和抗氧化性。Si C@C粉体是基于熔盐法的“模板机制”生成,主要由Si经熔盐液相层扩散至Si C层表面,即Si外扩散过程控制。

The application of graphite flakes in refractory castables was inhibited by their poor water-wettability,and carbides modified graphite was considered as the best way to solve this problem.Aimed to solve the high cost,difficulty in scalable fabrication,and unclear synthesis mechanism in the preparation process of carbide-modified graphite,a core–shell SiC@graphite powder was fabricated in air by a modified molten salt shielding technique in this work.Influence of encapsulation method on the phase composition and microstructure of as-obtained SiC@C powders was investigated.The results show that SiC@C powders can be fabricated via modified molten salt shielding method.The as-prepared SiC@C powders possess better water-wettability,dispersibility and oxidation resistance.The microstructural characteristic of SiC@C powders is indicated a core-shell structure,SiC layer is formed on graphite flake.The template-growth mechanism is dominant in molten salt synthesis process,i.e.,a small amount of Si is dissolved in the molten salt,diffused onto the graphite surfaces via a molten salt medium,and then reacted to form in-situ SiC coating layer on graphite flake,which is controlled due to the external diffusion of element Si.