Development of High Porosity Alumina Refractory Brick by Gelation of Slurry and Foaming Method

概要

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Alumina has high heat resistance and corrosion resistance compared to silica, mullite and other ceramics. However, it has the high thermal conductivity of about 36 W/mK at room temperature, and necessarily decreases its thermal conductivity for application to refractory bricks. Therefore, high-porosity alumina refractory brick was developed using GS (Gelation of Slurry) method that has been already developed for production of high-porosity metal foam. Appling this method to production of alumina foams, the foams from 94 to 97.5 % porosity was produced, which had the compression strength from 0.1 to 1 MPa. The strength was almost proportional to the square of the densities. Its thermal conductivity was also proportional to the density and obeyed the Ashby-Glicksman model for the open cell structure, though it took the closed cell structure. Its thermal conductivity was about 0.1 W/mK when the density was 0.1 g/cm<SUP>3</SUP>. The high-porosity alumina foam achieved the enough thermally insulating property for the refractory brick, and applications will not be limited to the refractory brick application.