Effect of holding time on the basic properties of biomorphic SiC ceramic derived from beech wood

Liquid silicon infiltration processing to manufacture biomorphic silicon carbide is a low-cost route and the resulting products have high strength. Holding time is an important factor to fabricate biomorphic ceramics with various strengths and open porosity. In this study, biomorphic SiC ceramics were prepared by infiltrating liquid Si into biocarbon template from beech at 1550 °C for different reaction time (holding time I), and sequentially removing Si at 1700 °C for different time (holding time II). The resulting products have coarse surfaces of the pore walls because of recrystallization of formed SiC. The porosity decreases and the bending strength and fracture toughness enhances as prolonging reaction time. Both bending strength and fracture toughness generally decline, while open porosity increases and the density decreases with removing of unreacted Si in the samples. While removing Si time is prolonged from 20 min to 60 min, the average bending strengths of the axial and radial samples decline by 41.3% and 54.4%, respectively. The average fracture toughness decreases by 45.9% for the axial samples and by 49.7% for the radial samples. The key factors to affect properties of the resulting products are the formed SiC and the residual silicon. The difference of the porosity and density of the axial and radial samples is decided by the relationship of the direction of the channels of samples and the direction of infiltration.