Monteiro, R. C. C., M. M. R. A. Lima, and C. S. Clemente. "
Development of structural ceramics from fly ash and shale."
Materials Science Forum. 587-588 (2008): 787-791.
AbstractThe possibility of using fly ash and shale as alternative raw materials for the production of structural ceramics was investigated. Fly ash is a by-product from coal-burning power plants, and shale is a sedimentary rock that if ground finely enough can exhibit a clay-like plasticity. Ceramic samples containing 10-50 wt% fly ash were formed from mechanical mixing of both kinds of powders that were packed and sintered in the temperature range 950-1200°C It was verified that powders with larger fly ash content exhibited lower packing density resulting in compacts with a lower sintered density. Although an increase in fly ash content was associated to a larger presence of porosity in the sintered samples, as confirmed by microstructural analysis, all studied compositions when sintered at the highest temperatures exhibited satisfactory values for water absorption (< 10%), for flexural strength (20-64 MPa) and for hardness (20-30 GPa) indicating that they have potential to be applied in the production of structural ceramics.
Lima, M. M. R. A., and R. C. C. Monteiro. "
Viscous sintering in a glass-alumina system."
Materials Science Forum. 587-588 (2008): 143-147.
AbstractThe densification during sintering of borosilicate glass matrix composites with 25 vol. % alumina (Al2O3) particles was investigated. The powder compacts, isostatically pressed at 200 MPa, were sintered at a temperature within the range 800-1000° C and maintained at this temperature during various times. The sintering behaviour of the composites was investigated by density measurement and by axial and radial shrinkage measurements. The crystalline phases present in the sintered composites were identified by XRD and the microstructure was analyzed by SEM. For temperatures up to 900°C, the relative density of the composites increased continuously with sintering temperature and sintering time, while for higher temperatures, the density increased rapidly and then slowed down to achieve a nearly constant value after sintering the composites for 30 minutes. The composites exhibited isotropic shrinkage behaviour when sintered at 800°C and 850°C, but at higher temperatures slightly higher axial shrinkage than radial shrinkage was observed. The shrinkage behaviour and microstructural characteristics of the composites indicate that densification during sintering can be attributed to the viscous flow of the borosilicate glass.