Fabrication And Characterization Of Porous YSZ Ceramics With Low Density, Low Thermal Conductivity And High Strength

Porous yttria stabilized zirconia (8 mol% Y2O3-ZrO2, YSZ) ceramics were fabricated by tert-butyl alcohol (TBA)-based gel-casting process. The relationship between room-temperature thermal conductivity and porosity was discussed. The temperature dependence of thermophysical properties and the influence of sintering temperature and solid loading on microstructure and properties were also investigated, respectively. Meanwhile, a processing route, using different freezing temperatures during freeze casting, to control the pore channel size in porous YSZ ceramics with unidirectionally aligned pore channels was reported. The objective of this study was to fabricate porous YSZ ceramics with both low thermal conductivity and high strength by adjusting processing parameters. The change of porosity, open porosity, pore size distribution and microstructure were discussed by adjusting solid loading and sintering temperature. The relationships between thermal conductivity, compressive strength and microstructure were discussed. The thermal conductivity of porous YSZ ceramics was 0.05~0.42 W/m?K, which was significantly lower than that of dense YSZ ceramics (~2.2 W/m?K). The corresponding compressive strength was 3~29 MPa. Thermal conductivity (λ) can be calculated from the thermal diffusivity (k), density (ρ) and specific heat at constant pressure (Cp):λ= kρCp。The thermal diffusivity (k) was measured at both ambient and elevated temperatures using laser flash technique. The specific heat (Cp) was also measured in the same temperature range during heating using a differential scanning calorimeter. The temperature dependence of thermal conductivity of porous YSZ ceramics was discussed. The pore structure formation of porous YSZ ceramics with unidirectionally aligned pore channels was discussed. The as-fabricated samples were characterized by observing the microstructure and evaluating pore size, pore size distribution, porosity and the room-temperature thermal conductivity.