Low-Temperature Synthesis and Mechanical Properties of SiC Porous Granules from Activated Charcoal with a Na Flux

Abstract

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 -type. Agglomerates of a few dozen nm of SiC grains and an electron diffraction ring pattern of -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 AE 1:0 m 2 /g and a pore volume of 0:006 AE 0:002 cm 3 /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 AE 1:0 GPa.

Synthesis of nitrides and silicon carbide using sodium

“…The structure and texture of the original carbonized wood were well maintained. It was also possible to change activated granular charcoal into bulk β-SiC by heating in a mixture of Si and Na at 973 K. 47) After the heating, Na was removed by evaporation. The density of the obtained SiC granular bulk sample was 69% of the theoretical density of β-SiC.…”

Fabrication of porous SiC ceramics having pores shaped with Si grain templates

“…16 A SiC porous granule, having a porosity of 21%, was synthesized at 700 • C from activated charcoal by using a Na-Si melt. 17 The porous granule exhibited a fracture stress of 47 MPa and a micro-Vickers hardness of 13 GPa. Morito et al proposed a Na-Si binary phase diagram based on thermal analysis and morphology of the products in this system, and revealed the presence of a Na-Si melt phase above 680 • C with a maximum Si content of around 50 at%.…”

“…[15][16][17] Nano-powder of ␤-SiC was prepared from a mixture of Si and fullerene powders in a Na melt. 15 Biomorphic cellular SiC ceramics were prepared by heating carbonized wood at 700 • C with a Na-Si melt.…”

Physicochemical Features in the Synthesis of Nanostructured Sіc Under Nonisothermal Heating from Hydrothermally Carbonized Rice Husk. II. Production of SiC Without Carbon Impurities

“…6. Infrared spectra for SiC synthesized from hydrothermally carbonized rice husk (1) after oxidative annealing (2), produced with addition of liquid glass (3), and partially oxidized at 1200C in air (4) It should be noted that more active reducing agents (except for carbon) make it possible to synthesize SiC from SiO 2 at temperatures below 1000C [7][8][9]. However, these processes require longer holding, at least 24 h. In our case, the process lasts several minutes.…”