Research Progress on Growth Mechanisms of Helical Carbon Nanofibers

Helical carbon nanofibers (HCNFs), a novel class of nanocarbon materials with a unique three-dimensional helical morphology, inherit many of the intrinsic properties of conventional carbon nanofibers while exhibiting additional characteristics such as superelasticity, unique electromagnetic response behavior, and a highly textured surface topology. These properties make HCNFs highly valuable for applications in electromagnetic shielding, nanosprings, and sensing technologies. Among the various fabrication techniques, chemical vapor deposition remains the most widely used and effective method for producing HCNFs, with structural regulation achieved by controlling parameters such as catalyst type and reaction temperature. Alternative methods such as flame synthesis, electrospinning, and templating have also demonstrated potential in growing HCNFs. Regarding growth mechanisms, the asymmetric carbon deposition and diffusion on catalyst surfaces are considered the primary drivers of the periodic curling behavior observed in HCNFs. Several models, including the three-dimensional growth mechanism, the vapor-liquid-solid-solid mechanism, and the coordination polymerization mechanism, have been proposed to elucidate the formation of helical structures. This review provides a comprehensive overview of recent advancements in HCNF growth mechanisms, emphasizing the roles of precursor materials, catalyst properties, and reaction conditions in achieving precise and controllable synthesis.