Sintering and charaterization of porous alumina ceramics containing carbon black powders

Porous ceramics are the materials, which combine superior properties of ceramics and advantages of porous structure, simultaneously. Porous ceramics can be utilized as ceramic filters, light-weight equipment and thermal insulators due to combination of properties as high hardness, chemical resistance, and high temperature resistance, lightness, low thermal conductivity etc. Aluminum oxide based ceramics are one of the most important materials for such applications and final properties of alumina based porous ceramics strongly depend on size, connection and amount of porosity as well as intrinsic properties of aluminum oxide. The main aim is always to improve lightness and insulation capabilities without compromising mechanical strength. In this study, porous alumina ceramics were manufactured by the addition of carbon black powders as pore forming agent. Then, the carbon black and alumina powder mixtures were sintered via spark plasma sintering (SPS), which is generally performed to obtain high-dense structures. After removal of carbon black particles, porous alumina ceramics were obtained. An inhomogeneous distribution of the carbon black powder throughout the structure was observed when the specific surface area of carbon black powder exceeded 40 m2/gr. On the other hand, there was no any drawback detected on mechanical and thermal properties of ceramics resulted by the inhomogeneous distribution of carbon black powders. Moreover, the strength of SPSed samples was measured at least as two times higher than that of conventionally sintered samples thanks to effective neck formation between alumina particles during partial sintering process.