High-temperature reactions between molten CaO-B2O3 slag and graphite, SiC, and BN ceramics

Fe-26Si-9B (wt. %) eutectic alloy is a promising high-temperature phase change material (PCM), but its production via metallothermic reduction requires a refractory container that can resist reaction with molten B 2 O 3 -based slags. This study investigated the wetting behavior of molten CaO-B 2 O 3 slag on graphite, SiC, and BN substrates using a sessile drop method at temperatures up to 1500 °C under argon atmosphere. The results showed that the molten CaO-B 2 O 3 slag exhibited good wetting on graphite and SiC, with final contact angles of 10° due to the reactions between the slag and the substrate, while the molten slag had a non-wetting behavior with BN (93° at 1500 °C) . The interfacial reactions led to the formation of boron-based phases and CO gas in graphite and SiC, whereas BN remained chemically stable. However, the thermal decomposition of BN might occur when the partial pressure of N 2 was below 2.53×10 -6 atm at 1500 °C , emphasizing the need for controlled gas environment. These results provide important information for selecting refractories involving B 2 O 3 -based slags at high temperatures.