Abstract
A bi-modal porous SiC with cylindrical pores and communicated pores were fabricated through unidirectional solidification of water slurry containing CO_2 gas and microwave sintering. The cylindrical pores were formed during the unidirectional solidification under reduced pressure and a composite of ice and SiC powder was obtained. Since the composite was formed by segregation of ice during the solidification, a communicated structure of ice was obtained. The ice was removed by vacuum freeze drying method. The porous bulk with cylindrical pores and communicated pores was sintered using microwave sintering for 5 minutes. Since the dielectric loss factor for SiC is larger than that of the other ceramics, a rapid heating of SiC bulk can be achieved by microwave sintering. The porosity and pore size was well controlled by the pressure during the solidification and sintering time. The degree of shrinkage can be controlled by adding a sintering agent.
