Synthesis of beta silicon carbide powders from biomass gasification residue

The synthesis of beta silicon carbide (β-SiC) powders by carbothermal reduction of silica with carbon in a high temperature tube furnace was investigated. As carbon source, fine carbon-containing char from biomass gasification was used, in order to verify the feasibility of producing a high added value material starting from waste residue, and to promote the gasification processes as alternative route of energy production by the proper by-products exploitation. Starting mixture was prepared by mechanically mixing silica and char in the weight ratio of SiO₂:C of 1.514; the mixture then reacted in a tube furnace at temperature of 1,550 °C at different residence times (1, 1.5, 2 and 2.5 h), at a constant flow rate of 0.8 dm³ min⁻¹ of argon. The reaction products were characterised with XRD, FTIR spectroscopy and transmission electron microscopy (TEM). The process turned out to be capable of producing high quality SiC powders, suitable for making ceramic materials and composites; the product shows an uniform spherical shape, a very fine particle size (within the range of 30–100 nm) and a purity degree varying from 70% to 95%, depending on the residence time.