Porous Ceramics Thermal Conductivity

It varies from 0 1 to 240 w m k.

Porous ceramics thermal conductivity. The thermal conductivity of porous 8ysz ceramics at room temperature as low as 0 053 w m k was one order of magnitude lower than that of dense 8ysz ceramics 2 2 w m k and decreased with. The thermal conductivity of porous ceramics can be tailored by slip casting and uniaxial dry pressing using either fugitive pore formers saccharides or partial sintering. The second method particularly suitable for porous ceramics is based on the extrapolation of the inverse of the thermal conductivity versus temperature to give an intercept with the axis at t 0 k. 1 shows the relative thermal conductivity k r k k 0 of porous alumina ceramics at room temperature in dependence of the porosity.

Porous alumina and zirconia ceramics have been prepared using appropriate powder types ungranulated for casting granulated for pressing and identical firing regimes but. Generally the thermal conductivity decreases as porosity increases 30. With the increase in solid loading of slurries lower porosity was obtained and the compressive strength and thermal conductivity showed a tendency of increase. Porous ceramics were prepared by different methods to achieve pore volume fractions from 4 to 95.

45 note that for the. Thermal treatment of the kaolin foam at 1100 c yields a suitable compromise between low thermal conductivity of 0 054 w m k 1 at room temperature with a compressive yield stress of 0 04 mpa. The viscosities of the original suspensions and the foamed ones with solid loading of 62 5 and 67 5 wt were measured. The radiation component in the effective thermal conductivity is 10 at 20 c increasing to 50 at 500 c.

Decreasing solid loading leads to the porosity of ceramic foams. Table 17 3 shows the thermal conductivity of a range of different ceramics 29 31 33. Incorporation of porosity into a monolithic material decreases the effective thermal conductivity. Zirconia ceramic foams with porosity of 97 9 has low thermal conductivity of 0 027 0 004 w m k 1 which could be used as thermal insulation and refractory material.

After the steps of forming and drying the green bodies were sintered under different temperatures from 1 200 to 1 600 c for 2 h. Porous ysz ceramics with compressive strength of 0 69 3 66 mpa showed low thermal conductivity in the range of 0 137 0 254 w m k at room temperature. Porous mullite ceramics were prepared from an industrial grade mullite powder by foaming and starch consolidation.