Effect of B4C on the properties and microstructure of Al2O3 -SiC-C based trough castable refractories

Abstract

The effect of B4C addition (0.5wt%, 1wt%, 1.5wt%, 2wt%) on properties and microstructure of Al2O3-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 B4C was over 1wt%. The cold modulus of rupture of samples improved significantly with the addition of B4C when the treating temperature was over 1100°C. Among them, sample with 1.5wt% of B4C 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 B4C after firing at 1450°C in air condition. The obtained fibers rooted in the walls of inner micropores of samples with the diameter of 50–200nm, and the lengths of 10–50µm. 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.