Evaluation and Control of Crack Propagation in Dense Porcelain/ Porous Alumina Layered Structures for Dental Material Applications
Layered structures of dense porcelain/porous alumina and dense porcelain/porcelainalumina/ porous alumina are designed and their crack propagation behaviors are investigated. As a substrate, the porous alumina, which is prepared by a gel-casting process using the binary slip of alumina powder and PMMA spherical micro-bead, is dried at room temperature for 24 h and then sintered at 1600 for 2 h. Porcelain is coated on the porous alumina substrate and then re-sintered at 987. Bi- and tri-layered structures are produced by the different dwell times (2 min, 10 min) at re-sintering temperature. There is no delaminating or cracks observed after re-sintering the layered samples. The crack propagation behaviors in the bi- and tri-layered structures are evaluated by micro-indentation. The indentation cracks do not propagate into the porous alumina through interface (porosity; 36~62%) except for another one (porosity; 70%) in the bi-layered samples. In the case of the high porosity bi-layered sample (porosity; 70%), cracks are scattered along the 3-D open-pore channels. However, cracks do not propagate through the interface in the tri-layered samples with a porcelain-alumina buffer layer, because the porcelain-alumina buffer layer plays an important part such as a barrier layer in crack propagation.
T. Ohji, T. Sekino and K. Niihara
J. W. Kim et al., "Evaluation and Control of Crack Propagation in Dense Porcelain/ Porous Alumina Layered Structures for Dental Material Applications", Key Engineering Materials, Vols. 317-318, pp. 457-460, 2006