Probing the mechanical properties of carbon nanohorns subjected to uniaxial compression and hydrostatic pressure

Carbon nanohorns (CNHs) as an important carbon nanostructure have been studied in many fields and shows huge potential for applications. Previous studies exhibit that CNHs consist of single-walled carbon nanohorns in the periphery and a graphene-based core in the center. However, the knowledge of their mechanical properties is still lacking. Here, the mechanical behaviors of CNHs subjected to uniaxial compression and hydrostatic pressure have been probed. Under uniaxial compression, two opposite dynamic responses were found to demonstrate different natures of flexible nanohorns and hard cores. The former shows good elastic recoverability but a hardening effect during multiple cycle loading, while the latter possess good load-bearing ability reflected by high compressive strength (max. Value of 18.8 ± 4.5 GPa) and high stiffness (max. Young' modulus of 84.6 ± 27.8 GPa). In hydrostatic state, the mechanical response is monitored by simultaneous Raman measurements through the shift of either G or 2D phonons of CNHs. The results show that two anomalies at pressures of ∼3 and ∼7.5 GPa have occurred, resulting from the nanohorns' cross-sectional shapes from circular-to-oval and oval-to-peanut-like structural phase transitions, respectively. Analysis based on Grüneisen parameter demonstrates the similarity of hydrostatic behaviors of CNHs and single-walled nanotubes, indicating high structural stability under high pressure.

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