Formation of silicon carbide nanorods from wood-based carbons

Man-made ceramic wood similar to petrified wood found in nature can be used at high temperature as the high oxidation rate of carbon above 500 degrees C is suppressed by a mu m thin SiC coating similar to the shuttle's heat shield. Possible applications are in the field of energy production, e.g., gas filters. In this paper, Japanese cedar was carbonized at 700 degrees C, vacuum infiltrated with tetraethylorthosilicate (TEOS), and heated at 1,500 degrees C for 30min using a pulse current heating device. A FIB-SEM dual beam microscope combination was used to investigate the SiC/C composite micro-texture. By milling away successive slices of material approximately 20nm in thickness, it was possible to confirm that a reaction layer of SiC, about 60nm in thickness, covers uniformly the surface of all cell walls. Furthermore, SiC nanorods were observed, growing more or less randomly in the charcoal pores. Cross-sectional SEM images of the SiC nanorods showed that either hollow or solid structures could be formed, having diameters ranging from 100 to 500nm. The SiC nanorod formation is being initiated by a catalytically operating SiC particle in the SiC coating. TEM analysis confirmed that they were grown along the [I I I] direction and indicated that an additional carbon layer covers the external surface of the rods making the rods more resistant against electron beam damage