Thermal Conductivity Of Very Porous Kaolin Based Ceramics

Candidate materials for thermal insulation combine a solid phase of low thermal conductivity with porosity.

Thermal conductivity of very porous kaolin based ceramics. Obtained porous ceramics from al 2 o 3 poly hollow microspheres. A theory is presented relating the effective conductivity to the conductivity of the solid material to the emissivity of the surface of the pores and to the size shape and distribution of the pores. 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 casio 3 as sintering additive coating microspheres via the coprecipitation method which improved the mechanical properties of the obtained porous ceramic.

In this paper a series of high porosity mullite ceramics with overlapped rod like grains were prepared from kaolin as extremely low cost raw material and. The effective thermal conductivity of a porous material is due to both conduction and radiation processes. Thermal conductivity of very porous kaolin based ceramics by julie bourret aurélie michot nicolas tessier doyen benoît nait ali fabienne pennec arnaud alzina jerome vicente claire peyratout and david stanley smith. Porous ceramics were prepared by different methods to achieve pore volume fractions from 4 to 95.

Thermal conductivity of this alumina porous ceramic with high porosity of 60 1 is as low as 2 1 w mk. Candidate materials for thermal insulation combine a solid phase of low thermal conductivity with porosity. A toolbox of analytical relations is proposed to describe the effective thermal conductivity as a function of solid phase thermal conductivity pore thermal conductivity and pore volume fraction ν p. The radiation component in the effective thermal conductivity is 10 at 20 c increasing to 50 at 500 c.

Very porous ceramics based on a commercial clay containing 79 kaolinite were made by a. Very porous ceramics based on a commercial clay containing 79 kaolinite were made by a direct foaming method using methylcellulose drying at 70 c before a consolidation at 1100 c. Candidate materials for thermal insulation combine a solid phase of low thermal conductivity with porosity. Using a guarded plate method norton obtained values for refractory kaolin bricks at 400 c ranging from 0 6 to 2 2 w m 1 k 1.

Hence developing low cost porous mullite ceramics with high mechanical performance low thermal conductivity and good dielectric properties is very important for radome applications.