CNT複合材料開発のためのCNT単体の力学特性評価

抄録

We reported an experimental study in which we investigated the nominal tensile strength of the thin MWCNTs prepared by thermal chemical vapor deposition method, and to provide insight required to enable the development of multi-walled carbon nanotubes (MWCNTs) with superior mechanical properties, we investigate the nominal (engineering) tensile strength–fracture strength–fracture cross-section ratio relationship of MWCNTs by conducting uniaxial tensile tests. The average outer and inner diameters of the MWCNTs are 7 nm and 5 nm, respectively. The fracture strength and nominal tensile strength of the MWCNTs are 13.9 ± 9.6 and 10.8 ± 6.9 GPa, respectively, which is markedly higher than those of previously reported CVD-grown MWCNTs. The MWCNTs have fractured in a clean break manner (i.e. large fracture cross-section ratio), and exhibited the higher fracture strength, which led to the higher nominal tensile strength. This result suggests that the fracture morphology and nominal tensile strength of CNTs are affected by the degree of inter-wall crosslinking, and there is an optimal crosslinking density for increasing the nominal tensile strength; not too low but also not too high, to permit an adequate load transfer between the nanotube walls. Our finding can help in developing better strategies for CNT composites and yarns that effectively exploit the superior mechanical performance of CNTs.