Two-D Analysis of the Thermo-Mechanical Properties of ZrO2-Based Composites

2. Experimental Procedure

The density of the samples was measured in ethanol, according to the Archimedes method. The electrical resistivity of the samples was measured according to the 4-point contact method. The elastic modulus, E and Poisson ratio, υ, of the ceramics was measured using the resonance frequency method (ASTM, 1994). The resonance frequency was measured by the impulse excitation technique.

The thermal expansion coefficient of the samples was determined with commercial thermomechanical analyser equipment (model Q400, TA Instruments, USA). Experiments were conducted in a temperature range from 25 to 900°C with a heating and cooling rate of 2°C/min on rectangular shaped samples of about 2024 mm³ with ground parallel lateral surfaces. The TA instrument was calibrated with a pure aluminium test sample from room temperature up to 500°C.

Thermal residual stresses through the thickness of the ceramic discs (434 mm) were measured by neutron diffraction. The neutron diffraction experiments were performed on the high-resolution SPN100 neutron stress scanner available at the medium-power reactor LVR-15 at NPI in Řež (Czech Republic).The measurement method is based on an experimental examination of the two components of the lattice strain tensor and conversion of the measured lattice strains to stresses (Lukáš, 2005). Expansion or contraction of the lattice constant compared to measured lattice constant on pure phases is translated to residual thermal stresses due to mismatch between thermal expansion coefficients of constituents in the composite.