Fracture mode and compressive strength of ice-templated porous zirconia

Porous zirconia with different porosity and pore architecture were prepared by adjusting the solid loading and the binder concentration of the suspensions, and freezing rate via an ice-templating method. The transition of the fracture mode and the relationship between the compressive strength and process parameters were identified and investigated. The load-displacement curves showed a variation from a buckling fracture at porosity above 70 % to a brittle fracture in the porosity range from 35.3 % to 55.5 %, owning to the increased resistance of the ceramic walls to buckling. As the porosity decreased from 75.0 % to 35.3 %, the mean compressive strength of the samples increased from 4.5 MPa to 197.1 MPa. Under buckling fracture, increasing the binder concentration from 2 wt% to 4 wt% contributed to the improvement of the mean compressive strength from 5.5 MPa to 14.8 MPa, although samples had similar porosity level (~73 %). For brittle fracture, samples with porosity around 54 % exhibited the improvement of mean compressive strength from 45.5 MPa to 75.1 MPa when increasing the freeze velocity from 8 °C/min to 25 °C/min.