Effect of Phenolic Resin on the Basic Properties of Woodceramics and Biomorphic SiC Ceramics

Biomorphic SiC ceramics were fabricated by infiltrating liquid silicon into woodceramics which were prepared from beech and pine impregnated with phenolic resin (PR) of different viscosity in order to reinforce the cell wall of wood. The viscosity of phenolic resin was adjusted by ethanol according to the weight ratio of PR to ethanol. The samples not impregnated with resin were compared. Effect of viscosity of phenolic resin on the dimension shrinkage, weight loss, porosity and the axial and radial flexural strength were investigated. Microstructural observation and phase identification of woodceramics and biomorphic SiC were performed by SEM and XRD, respectively. The results show that, the lower the viscosity of phenolic resin was, the higher the dimension shrinkage, weight loss and porosity of woodceramics were. Biomorphic SiC was a diphase composite consisting of major phase β-SiC and secondary phase Si. Woodceramics made from pine swelled or broke and strength of woodceramics fabricated from beech declined when higher viscosity resins were impregnated. The flexural strength of biomorphic SiC increased with increasing in viscosity of PR. The axial flexural strength was significantly higher than the radial flexural strength because of anisotropic pore microstructures.