Synthesis of Ca-Al-Si-O Compounds from Local Wastes
The local wastes, which are sources of SiO2, Al2O3 and CaO, are rice husk ash, waste sediment from aluminum anodizing process and dreg from pulp production, respectively. The wastes are mixed in three different compositions in ranges of 20-50 SiO2, 20-35 CaO and 20-45 Al2O3, wet milled, slip casted and then fired at 1,100 °C. Characterization of the fired bodies reveals the formation of calcium-aluminosilicate compounds: gehlenite and anorthite as major phases, in accordance with the SiO2-CaO-Al2O3 ternary diagram. Their bulk densities and % water absorption lies between 0.95-1.42 g/cm3 and 37.40-67.95%, respectively. While flexural strength and coefficient of thermal expansion are between 4.09-9.56 MPa and 6.14 - 10.1 x 10-6 °C-1, respectively. By simple thermal conductivity comparison, the materials themselves have thermal conductivity comparable to alumina ceramics. These wastes, therefore, may be used as precursors for the production of some insulating refractory members, in place of minerals from natural resources.
Hyungsun Kim, JienFeng Yang, Tohru Sekino and Soo Wohn Lee
U.S. Sanewirush and P. Saewong, "Synthesis of Ca-Al-Si-O Compounds from Local Wastes", Materials Science Forum, Vols. 620-622, pp. 121-124, 2009