Recently, there has been an increasing interest in the applications of porous SiC ceramics as functional materials. A number of manufacturing approaches have been applied to fabricate porous SiC including polymer pyrolysis, oxidation bonding, and reaction bonding. However, these processes are complicated and conventional porous SiC shows insufficient physical and chemical stability under a high temperature environment. Therefore, from the view point of safety and stability, it is necessary to develop an uncomplicated manufacturing method for high performance porous SiC ceramics. In this study, SiC nano-powder and carbon particles have been used as starting material and pore former, respectively. Mixed powders were hot-pressed under a pressure of 20 MPa at 1900 oC for 1 h. Carbon powder which was added to the sintered body was burned out by a decarburization process in air at 700 oC. The porosity was measured by the Archimedes method with an immersion medium of water and an image analysis method. The microstructure was examined by scanning electron microscopy. Mechanical properties were investigated using three-point bend test. It was established that the critical additive amount of carbon particles for porous SiC ceramics was about 20 vol.%, through the microstructure and thermogravimetric analysis during the decarburization process. The porosity of the porous SiC ceramics could be controlled with a high degree of accuracy, from the relationship between the added amount of carbon particles and porosity. The flexural strength of the porous SiC ceramics with 50% pores, where spherical pores were introduced, was about 170MPa. These porous SiC ceramics exhibited a substantially high strength in comparison with other conventionally processed porous SiC ceramics, due to their robust microstructures consisting of spherical pores.

Keywords: Porous SiC ceramics, SiC nano-powder, Carbon particle, Decarburization process, Spherical pore.