Sintering mechanism of blast furnace slag-kaolin ceramics

Autores: Mostafa, N.Y.|Shaltout, A.A.|Abdel-Aal, M.S.|El-maghraby, A.
Fuente: Materials and design
31 (8), 3677-3682
2010

A general ceramics processing scheme by cold uniaxial pressing and conventional sintering process have been used to prepare ceramics from mixtures of blast furnace slag (BFS) and kaolin (10, 30 and 50% kaolion). The properties of the ceramics were studied by measuring linear shrinkage, bulk density, apparent porosity and mechanical properties of samples heated at temperatures from 800°C to 1100°C. The formed crystalline phases were characterized using X-ray diffraction (XRD) and scanning electron microscope (SEM). Slag melt formed at relatively low temperatures (800-900°C) modified the sintering process to liquid phase sintering mechanism. Combination of BFS with 10% kaolin gave the highest mechanical properties, densification and shrinkage at relatively low firing temperatures. The crystalline phases were identified as gehlenite (Ca2Al2SiO7) in both BFS and BFS with 10% kaolin samples. Anorthite (CaAl2Si2O8) phase increased with increasing kaolin contents. In the case of kaolin-rich mixtures (30% & 50% kaolin), increased expansion took place during firing at temperatures in the range 800-1000°C. This effect could be attributed to the entrapment of released gases.