Carbon Structure‐Regulated SiC Whiskers From Biochar: Formation Kinetics and Microwave Absorption

ABSTRACT

SiC whiskers were synthesized from Si powder using graphite, carbon black, coconut shell charcoal, and corncob charcoal as carbon sources under carbon‐embedded conditions. The effects of carbon structure on SiC formation kinetics, whisker growth, and microwave absorption behavior were systematically investigated. Compared with conventional carbon sources, biochar‐derived carbons with hierarchical porous structures and abundant surface functional groups promoted the generation and transport of gaseous intermediates, including CO(g) and SiO(g), thereby facilitating SiC formation at lower temperatures. They also favored the formation of abundant SiC whiskers with high aspect ratios and interconnected network structures. Kinetic analysis showed that SiC formation followed a diffusion‐controlled parabolic rate law. The apparent activation energies for corncob and coconut shell charcoals were 386.60 and 292.74 kJ∙mol ⁻¹ , respectively, markedly lower than those for graphite (785.34 kJ∙mol ⁻¹ ) and carbon black (723.15 kJ∙mol ⁻¹ ), confirming the enhanced reaction kinetics induced by biochar‐derived carbon structures. Moreover, coconut shell‐derived SiC whiskers exhibited a minimum reflection loss of −26 dB at 14.8 GHz. These results clarify the role of carbon structure in regulating SiC whisker formation and provide a sustainable route for preparing SiC whiskers with favorable microwave absorption performance.