MULLITE-ALUMINA FUNCTIONALLY GRADIENT CERAMICS

Cracks free mullite-alumina Functionally Gradient Ceramics (FGC) have been obtained by sequential slip casting of Mullite-alumina slurries w ith different mullite/alumina ratios. These slurries were prepared wit h 65 % solids content and viscosities ranging from 10 to 40 mPa.s. The presence of cracks perpendicular to the FGC layers have been attribut ed to residual stresses developed because of the mismatch in thermal e xpansion between layers. The microstructure of the different layers, a nd de residual stress value sigma(R) in each layer was also determined .