Low-temperature synthesis and mechanical properties of SiC porous granules from activated charcoal with a Na flux

SiC porous granules were synthesized from activated granular charcoal and Si powder at 973 K by using a Na flux. The SiC granules maintained the shape of the charcoal with a dimension of about 5 mm in diameter and 7-10 mm in length. X-ray diffraction showed the structure of the formed SiC to be cubic β-type. Agglomerates of a few dozen nm of SiC grains and an electron diffraction ring pattern of β-SiC were observed with a transmission electron microscope. A micropore size distribution of < 4 nm and mesopores in the range of 20-40 nm were shown by a nitrogen adsorption technique. The SiC granules had a specific surface area of 3.4 ± 1.0 m²/g and a pore volume of 0.006 ± 0.002 cm³/g. The fracture stress of the SiC porous granules was evaluated to be 47 MPa by a compressive test at room temperature. The Vickers hardness of the granule surface was 13.1 ± 1.0GPa.