Microstructures And Properties Of Carbon Fibers And In-Situ Whiskers Reinforced Mullite-Based Castable Composites

With spalling and corrosion during thermal cycles, the castable composites used in injecting lance are easily damaged. In order to solve this problem, we used carbon fibers as additives in the matrix, and prepared mullite- based castables with the addition of anti-oxidant silicon. It was found that the addition of carbon fibers could significantly improve the mechanical properties; the maximum mechanical strength was obtained when 0.1 wt% carbon fibers was added, and the maximum thermal shock resistance was obtained when 0.2 wt% carbon fibers was added. The carbon fibers were oxidized mostly after firing at 1100oC, while after firing at 1450oC, due to the dense oxide layers generated on the surface of the castables, most of the carbon fibers in the castables remained in good combination with the matrix. Some SiC whiskers with SiO2 coating were formed in the matrix after heat treatment at 1100oC in air. The model of the whiskers growth mechanism followed the vapour-solid mechanism.