Effects of alumina slag (Valoxy) and rice husk ash as substitute resources on mechanical properties of mullite based ceramics

In this study, mullite-based ceramics were prepared by substituting alumina slag (valoxy) and rice husk ash (RHA) for commercially pure alumina and quartz, respectively. Five body compositions containing 5, 10, 15, and 20% valoxy: RHA were created. At 75MPa load, the formulated bodies were thoroughly mixed homogeneously and uniaxially compacted to produce cylindrical shaped samples 30 mm diameter and 50 mm high. After compacting the samples, they were sintered in a muffle furnace at 1200 ℃ at a rate of 10 ℃/min for 2 hours before being allowed to cool to room temperature before offloading. Mechanical properties such as microhardness and compressive strength was conducted on the samples to determine the effects the substitute materials have over the formulated mullite ceramics. The results showed maximum hardness (16 GPa) and compressive strength (56.76 GPa) was observed for samples containing 2.5 % valoxy: 2.5 % RHA respectively while decline in hardness and compressive strength was observed for the remaining compositions. Thus, indicating that the use of these wastes materials is only beneficial at lower percent inclusion.