Effect of carbon sources on morphology of B4C powders synthesized by magnesiothermic SHS

Based on the magnesiothermic self-propagating in-situ synthesis (SHS) method, we systematically investigated the effects of intrinsic physical properties of five inorganic carbon sources - graphite, charcoal, activated carbon, carbon black, and carbon nanotubes (CNTs)-on the crystal growth behavior of Boron carbide (B 4 C). The results showed that different carbon sources exhibited significant differences in chemical composition, particle size distribution, and microstructure. These differences further affected their chemical reaction activity and significantly regulated the thermodynamic behavior and reaction kinetics during the self-propagating process. The structural characteristics of the carbon sources significantly affect the crystallization behavior and morphology-influenced growth of B 4 C products: Graphite shows low reaction reactivity due to its highly ordered layered structure, yielding B 4   C with the highest free carbon content (16.37 wt%), lowest crystallinity (11.75 wt%), and flake-like morphology. Charcoal and activated carbon have enhanced reactivity by porous structures, producing B 4   C with reduced free carbon content (4.61 wt%), improved crystallinity, and strip-like morphology. Carbon black exhibits excellent reactivity due to its amorphous structure and high defect density, resulting in B 4   C with the lowest magnesium residue (0.35 wt%), relatively high crystallinity, and regular fine-grained morphology. Carbon nanotubes possess high reactivity owing to their tubular nanostructure, generating B 4   C with the highest crystallinity (85.81 wt%) and solid columnar morphology. Starting from the correlation mechanism of carbon sources structure-reaction behavior-product morphology, this study provided a theoretical basis and experimental support for the directional regulation of B 4 C microstructure and properties.