Pembuatan dan Karakterisasi Mullite dari Kaolin Alam dan Alumina Dross

Abstract

Ceramic mullite has been made using several materials, namely kaolin, pure alumina, and alumina dross. Mullite was prepared with a stoichiometric composition of 2Al2O3.SiO2, with variations in pure alumina and the addition of alumina dross. The raw materials were mixed using a planetary ball mill with distilled water as the medium, then dried at 110 °C. Subsequently, it was dry-pressed with a pressure of 70 kgf and sintered at temperatures of 900, 950, 1000, 1100, 1300, and 1500 °C. XRF characterization results revealed that Bangka Belitung kaolin contained 48,60% silica, 46,90% alumina, and several other compounds in low percentages. In contrast, alumina dross contained 79,71% alumina, 4,04% silica, and other compounds such as Fe2O3 and CaO. Mullite was characterized, including physical tests (density and porosity), mechanical tests (compressive strength), and XRD analysis. Density and porosity test results indicated that with increasing sintering temperature, the density values increased, while the porosity decreased. Compressive strength values showed that higher sintering temperatures led to higher compressive strength. The maximum values of physical and mechanical testing results were obtained in samples with the addition of sintered alumina dross at a temperature of 1500 °C, with respective values for density, porosity, and compressive strength of 2,509 g/cm3, 3,309%, and 85,492 MPa, respectively. XRD analysis revealed the formation of cristobalite, corundum, and mullite phases in the samples.