Strengthening of Al2O3-C slide gate plate refractories with expanded graphite

Expanded graphite, fabricated by microwave irradiation of acidified flaky graphite, was used to partially replace graphite and carbon black in a commercial Al2O3-C refractory slide gate plate composition. The developed refractories exhibited enhanced cold and hot strength, as well as oxidation resistance. X-ray diffraction indicated the formation of SiC phase even at temperatures lower than the melting point of Si. Field emission scanning electron microscopy exhibited homogeneous formation of three dimensionally oriented nanostructured SiC whiskers in the samples fabricated with expanded graphite. The formation of the thicker primary whiskers and thinner secondary whiskers in the inter-aggregate space bridging two particles was observed frequently for the expanded graphite fortified samples. Whisker reinforcement of this nature has rarely been observed in refractory systems, which is credited for a considerable improvement in the hot modulus of rupture of the new compositions. (C) 2014 Elsevier Ltd and Techna Group S.r.l. All rights reserved.