SYNTHESIS AND MECHANICAL PROPERTIES OF Electrophoretically deposited ALUMINA/ZIRCONIA LAMINATED COMPOSITES

Abstract

Al2O3/YPSZ laminates were fabricated by electrophoretic deposition (EPD) and pressureless sintering. Laminated composites with non-planar ("wavy") layers were produced by depositing powder from ethanol suspensions, onto a grid of Al2O3 fibres. Laminates with thin (~3 μm) YPSZ and thick (> 10 μm) Al2O3 layers (12 vol % YPSZ) were produced. Deposition mass was a linear function of deposition time and current density. Al2O3-YPSZ interfaces were very strong and no delamination or crack deflection along the interface was observed. The flexural strength of the Al2O3/YPSZ laminates (tested at 25oC, 800oC and 1300oC) were slightly lower than monolithic Al2O3. This is attributed to crack-like defects which form during drying and to the deterioration of the strength of YPSZ at elevated temperatures. The fracture toughness of the Al2O3ZYPSZ laminates were slightly higher than monolithic Al2O3 over the temperature range tested (25oC - 1300oC). This is due to the stress- induced (t)→(m) phase transformation in the YPSZ layers at room temperature and to microplasticity in the YPSZ layers at 1300oC. Room temperature crack trajectories were influenced by the residual thermal, and induced elastic stresses in the laminates. Cracks were deflected towards thin YPSZ layers because of the tensile induced elastic stresses in the thick Al2O3 layers and the tensile thermal residual stresses in the thin YPSZ layers.