Microstructures and mechanical properties of Al2O3–C refractories with silicon additive using different carbon sources

Graphite flake and carbon black were selected as carbon source in Al2O3–C refractories, respectively. The influences of carbon sources on the morphologies of in situ formed SiC and mechanical properties of Al2O3–C refractories were investigated in this work. The results showed that SiC of different morphologies can be produced via in situ reaction between silicon powder and different carbon sources. The spherical SiC particles were synthesized from carbon black, while SiC whiskers were produced from both graphite flake and derivative carbon pyrolyzed from phenolic resin. Meanwhile, the mechanical properties of Al2O3–C refractories were related to the formation of SiC phase in the matrix. At 1000 °C there is no obvious difference in mechanical properties of the two kind carbon source containing refractories, for they are bonded only by carbon derived from phenolic resin. With increase in temperature, ceramic bond also forms in Al2O3–C refractories gradually owing to the formation of SiC phase in matrix. Larger displacement and greater force can be observed in graphite flake containing Al2O3–C refractories than that in carbon black containing refractories, which is attributed to the formation of much more curved SiC whiskers and the sliding mechanism between graphite layers in the former refractories at higher temperatures.

Research highlights▶ SiC whiskers can be obtained from Si–C system when graphite flake or phenolic resin is used, while only SiC particles can be formed when carbon black is used. ▶ SiC of different morphologies construct different microstructures and lead to different mechanical properties in Al2O3–C refractories with silicon additive. ▶ The mechanical properties in graphite flake containing Al2O3–C refractories are better than those in carbon black containing Al2O3–C refractories because of the formation of much more curved SiC whiskers and the sliding mechanism between graphite layers in the former refractories at higher temperatures. ▶ Controllable microstructures and desirable mechanical properties of carbon containing refractories can be achieved by selecting proper carbon sources.