Effect of B 4 C on the properties and microstructure of Al 2 O 3 -SiC-C based trough castable refractories

Abstract The effect of B 4 C addition (0.5 wt%, 1 wt%, 1.5 wt%, 2 wt%) on properties and microstructure of Al 2 O 3 -SiC-C (ASC) based trough castables was studied in this paper. The results showed that the bulk density of samples after firing at 1450 °C decreased when the addition of B 4 C was over 1 wt%. The cold modulus of rupture of samples improved significantly with the addition of B 4 C when the treating temperature was over 1100 °C. Among them, sample with 1.5 wt% of B 4 C had the best anti-slag performance and thermal shock resistance. The SiC fibers were formed in the non-oxidized zone of ASC castables with addition of B 4 C after firing at 1450 °C in air condition. The obtained fibers rooted in the walls of inner micropores of samples with the diameter of 50–200 nm, and the lengths of 10–50 µm. The experiment revealed the nucleation of SiC started at about 1000 °C, and then the growth of SiC fibers happened at higher temperature in a favorable condition. A stepped twin structure perpendicular to the growth direction of fibers could be observed. Finally, the growth mechanism was interpreted by thermodynamic calculations.