EFFECTS OF SILICON CARBIDE AND SINTERING TEMPERATURE ON THE PROPERTIES OF SINTERED MULLITE-CARBON COMPOSITE SYNTHESIZED FROM OKPELLA KAOLIN

Abstract

The effects of the addition of silicon carbide and sintering temperatures on the physical and mechanical properties of sintered ceramic composite produced from kaolin and graphite was investigated. The kaolin and graphite of known mineralogical composition were thoroughly blended with 4 and 8 (vol.) % silicon carbide. From the homogeneous mixture of kaolin, graphite and silicon carbide, standard samples were prepared via uniaxial compaction. The test samples produced were subjected to firing (sintering) at 1300˚C, 1400˚C and 1500˚C. It was observed that increase in sintering temperature beyond 1400°C generally lead to reduced porosity of the samples; high contents of silicon carbide especially at temperature from and above 1400°C lead to higher porosity; cold crushing strength of samples with 4% SiC is seen to be better than those of samples with 8% SiC within sintering the temperature range of 1400°C and 1500°C; modulus of elasticity of both samples reached the maxima values at 1400°C but those of samples with 8% SiC is seen to be higher within the sintering temperature range of 1400°C and 1500°C; absorbed energy of both samples generally increased with increased sintering temperature; oxidation indices for both samples reach the maxima at the temperature of 1400°C but the resistance to oxidation is better for samples with 4% SiC within the sintering temperature range of 1400°C and 1500°C. It was concluded that samples with 4% SiC at the sintering temperature of 1400°C exhibit better property and is considered to be optimum.