Influence of additives on nano-SiC whisker formation in alumina silicate–SiC–C monolithic refractories

This study describes the effect of additives on increasing cold crushing strength (CCS) and bulk density (BD) of alumina silicate–SiC–C monolithic refractories. Two series of carbon-containing monolithics were prepared from Iranian chamotte (sample A) and Chinese bauxite (sample B), as 65 wt.% in each case together with, 15 wt.% SiC-containing material regenerates (crushed sagger) and 10 wt.% fine coke (a total of 90% aggregate) and 10 wt.% resole (phenol formaldehyde resin) as binder. Different values of additives (such as silicon and ferrosilicon metal) are added to the mixture and BD, apparent porosity and CCS are measured after tempering at 200 °C for 2 h and firing at 1100 °C and 1400 °C for 2 h. At low temperature of 200 °C, Si and ferrosilicon contribute to the formation of stronger cross-linking in the resit structure and provide CCS values of as high as about 65 MPa. At 1400 °C, SiC whiskers of nano-sized diameter are formed due to the presence of Si and FeSi2 and improve CCS values of as high as about 3–4 times in sample containing 6 wt.% ferrosilicon metal as additive.