Preparation of SiC coated graphite flake with much improved performance via a molten salt shielded method

Abstract Oxide‐based castables have been used in high‐temperature furnace linings, especially for steel and iron processing, however, the poor thermal shock resistance and corrosion resistance limited the further enhancement of their service life. Carbon possesses excellent performances including low wettability to slag, low thermal expansion coefficient, which can greatly improve thermal shock resistance and slag resistance of oxide‐based castables. However, it has poor water‐wettability and oxidation resistance, which limited its application in the castables. Many efforts have been attempted to improve water‐wettability of graphite flake used for carbon‐containing castables, but it is still a huge challenge. In this work, a facile method for fabricating silicon carbide (SiC) coated graphite flakes has been firstly proposed by using graphite flake and silicon powder as the precursors via a molten salt shielded synthesis technique in air atmosphere, KCl was chosen to be a salt encapsulation providing a liquid reaction medium and a shield against oxidation of air. Effects of firing temperature, holding time, and molar ratio of Si and graphite flake on the formation of SiC coatings were investigated. The results show that the as‐prepared SiC coated graphite powders were loose and non‐agglomerated, and the coatings with ∼5 μm in thickness were crack‐free and firmly grown on the surface of graphite flake, composed of SiC nanosized particles. Compared to uncoated graphite flake, the SiC coated graphite possessed significantly improved water‐wettability, dispersibility, and oxidation resistance, making it to be a prime carbon form for fabricating carbon‐containing castables.