Mechanistic study on the formation of silicon carbide nanowhiskers from biomass cellulose char under microwave

Abstract

The paper reports the synthesis of SiC nanowhiskers via a process that utilizes carbon and silica from the same renewable source without the addition of external Si precursors as a sustainable and cost-effective method. This study reports an improved and sustainable method of synthesizing silicon carbide (SiC) nanowhiskers using cornstalk cellulose char under microwave heating. The aim was to optimize the process and gain a deeper understanding of the formation and growth mechanism of SiC nanowhiskers from biomass under microwave treatment in a temperature range of 1200–1400 °C. The synthesized product was then characterized by various analytical techniques. The formation of SiC nanowhiskers (β-SiC) was promoted at higher reaction temperatures, increasing from 6.83 wt% at 1200 °C to 9.35 wt% at 1400 °C. The SiC nanowhiskers displayed straight rod and smooth cylindrical structures. The nanostructure of β-SiC was confirmed along the d-spacing (111) plane, with a characteristic lattice fringe spacing of 0.25 nm. The growth mechanism of the SiC nanowhiskers followed two reaction pathways of vapor-solid (VS) and the vapor-liquid-solid (VLS). Increased CO and CO2 concentrations due to the evolution of gaseous products (SiO and CO) from the reactive cellulose char led to the growth of SiC nanowhiskers under the solid-vapor mechanism. The presence of inherent metallic species, such as Fe in biochar was found to catalyze the formation and growth of SiC nanowhiskers.