The production of a carbon-coated alumina foam

Abstract

A method for producing ultra light carbon-coated alumina foam with a density of 0.04 g cm −3 and 99% porosity has been developed. It was synthesised from an aqueous aluminum nitrate–sucrose solution. The resin formed by heating this solution underwent foaming and set into solid green foam, which was sintered in the temperature range 1073–1873 K. The thermogram obtained by heating the green foam in argon showed 62 wt% mass loss occurring in three stages. The sintered foam constituted 81 wt% of γ-alumina in three-dimensional network and 19 wt% of carbon present as coating over the alumina framework. Phase analysis by X-ray diffraction revealed that carbon is in outer phase and γ-alumina is in the inner phase. Surface morphology of this foam, examined by scanning electron microscope showed open, fully interconnected and near spherical pores held together by hexagonal edges with a 300 μm average pore size. Energy dispersive X-ray spectroscopy revealed peaks corresponding to carbon, oxygen and aluminum indicating that the foam is free from nitrogen impurity. The surface concentration of carbon is nearly 85 wt% while it coating thickness is about 10 μm.