Fabrication of high- strength alumina composite foams through gel- casting process

A water–soluble gelatin combined with polyethylene microspheres were developed to prepare alumina composite foam. Gelatin was used as the gelling agent and polyethylene was used as pore making template. On the other hand, kaolin was used to provide green strength and CuO was applied to decrease the required temperature as a sinter aid. Alumina bodies need elevate temperature for sintering, increasing the process cost. This process could be carried out at 1000 ºC, therefore more appropriate than that of the previous studies. The effect of CuO amounts on the open porosity, water adsorption, and density as well as on the mechanical strength of sintered foams was evaluated. The resulting samples, with relative densities between 0.97 and 1.16 g/cm3, and compressive strength between 1.4 – 5.5 MPa, comprised microstructures of semi–spherical pores. The phase component of the samples consist ~60 % alumina, 11 – 15 % CuAl2O4, and 24 – 27 % Al2SiO5. The degree of crystallinity measured in range of 66 – 83 %. These changes are related to the CuO/Al2O3 ratio. On the other hand, gelatin and polyethylene as the gelling agent and pore template were used successfully in gel–casting process.