Preparation and characterization of porous, biomorphic SiC ceramic with hybrid pore structure

摘要

Bio-carbon template (charcoal) was prepared by carbonizing pine wood at 1200 deg C under vacuum, and was impregnated with phenolic resin/SiO_2 sol mixture by vacuum/pressure processing. Porous SiC ceramics with hybrid pore structure, a combination of tubular pores and network SiC struts in the tubular pores, were fabricated via sol-gel conversion, carbonization and carbothermal reduction reaction at elevated temperatures in Ar atmosphere. X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR) and scanning electron microscope (SEM) we're employed to characterize the phase identification and microstructural changes during the C/SiO_2 composites-to-porous SiC ceramic conversion. Experimental results show that the density of C/SiO_2 composite increases with the number of impregnation procedure, and increases from 0.32 g cm~(-3) of pine-derived charcoal to 1.5 g cm~(-3) of C/SiO_2 composite after the sixth impregnation. The conversion degree of charcoal to porous SiC ceramic increases as reaction time is lengthened. The resulting SiC ceramic consists of beta-SiC with a small amount of alpha-SiC. The conversion from pine charcoal to porous SiC ceramic with hybrid pore structure improves bending strength from 16.4 to 42.2 MPa, and decreases porosity from 76.1 percent to 48.3 percent.