Development of alpha -Al sub(2) O sub(3) Ceramics for Bottom of Sintering Impeller Furnace

In this work, the processing of alpha -Al sub(2) O sub(3) ceramics is studied in order to attain the microstructure and mechanical and thermal properties suitable for its application as a special refractory material in sintering furnaces. Samples of a commercial powder with addition of 3% polyvinyl alcohol, a binder additive, was compacted by uniaxial cold pressing and sintered in air at 1500 oC. The effects of powder preparation conditions and the consolidation process on density, thermal expansion and conductivity, hardness, flexural strength and microstructure were analyzed. Ceramics with densities of approximately 90% were obtained, with an average hardness of 14.9 + or - 0.6 GPa, characteristic strength of 238 MPa and Weibull modulus of 8. The microstructure had grain sizes between 1 and 2 mu m. Processing and powder consolidation and sintering parameters resulted in alumina ceramic with suitable properties for its intended purpose.