Optimized vacuum/pressure sol impregnation processing of wood for the synthesis of porous, biomorphic SiC ceramics

Pine (Pinus silvestris) wood with shaped sample dimensions of 20 mm × 20 mm × 5 mm (axial) was selected as the raw material. Samples were dried and, for a half of the samples, resin extraction from the sample was applied. SiO2 sol was prepared, and samples were impregnated under different vacuum/pressure conditions. Relative impregnation efficiency was calculated for impregnated samples and varied from 95 up to 105% of the theoretical value for different samples and impregnation conditions. Impregnation and drying procedures were repeated up to three times to increase the SiO2 amount introduced in the sample. Impregnated samples were pyrolyzed at 500 °C under oxygen free atmosphere with the subsequent high temperature treatment at 1600 °C in an Ar atmosphere. Biomorphic SiC ceramics and its precursors were investigated using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR) and scanning electron microscopy (SEM). An experimental result shows that the optimized vacuum/pressure impregnation technique is highly effective for the introduction of SiO2 in the wood.