Thermal conductivity of porous alumina ceramics prepared using starch as a pore-forming agent

The thermal conductivity of porous alumina ceramics prepared using different types of starch (potato, wheat, corn, and rice starch) as pore-forming agents is investigated from room temperature up to 500 degrees C. The temperature dependence measured for alumina ceramics of different porosity (in the range 6-47%) is fitted with second-order polynomials and 1/T-type relations, and compared to available literature data for dense alumina. It is found that the porosity dependence of the relative thermal conductivity k(r) = k/k(0) is well described by a modified exponential relation of the form k(r) = exp(-1.5 phi/(1 - phi)), where phi is the porosity. This finding is in agreement with other literature data and seems to indicate a common feature of all porous materials with microstructures resulting from fugitive pore-forming agents. (c) 2008 Elsevier Ltd. All rights reserved.