Key factors limiting carbon nanotube strength: Structural characterization and mechanical properties of multi-walled carbon nanotubes

Shirasu, Keiichi; Tamaki, Itaru; Miyazaki, Takamichi; Yamamoto, Go; Bekarevich, Raman; Hirahara, Kaori; Shimamura, Yoshinobu; Inoue, Yasuo; Hashida, Toshiyuki

doi:10.1299/mej.17-00029

Cited by 18 publications

(17 citation statements)

References 23 publications

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“…The authors have investigated experimentally the mechanical properties of the individual MWCNTs by conducting uniaxial tensile tests that have been performed with a manipulator inside the vacuum chamber of SEM. The detailed procedure for tensile testing is described elsewhere (Yamamoto, et al, 2010;Shirasu, et al, 2017b). The measured mechanical properties including nominal tensile strength, Young's modulus and failure strain are summarized in Table 2.…”

Section: Resultsmentioning

confidence: 99%

“…It can be seen that no clear difference in the mechanical properties between as-grown and thermally annealed MWCNTs is seen, which suggests that the structural changes observed in this annealing conditions used in this study may lead to no significant effect on both the nominal tensile strength and Young's modulus. This is mainly because the as-grown MWCNTs used in this study include the structural defects, i.e., kinks and bends and discontinuous flaws that are not completely removed by thermal annealing and are still observed in the thermally annealed MWCNTs even though the as-grown MWCNTs possess an intermediate level of crystallinity (R = 0.31) (Shirasu, et al, 2017b). 3.8 ± 1.5 227 ± 103 2.0 ± 0.4 a : Shirasu, et al, (2017b) Next, the thermal expansion property of the aligned MWCNT reinforced epoxy composites was evaluated.…”

Section: Resultsmentioning

confidence: 99%

“…This is mainly because the as-grown MWCNTs used in this study include the structural defects, i.e., kinks and bends and discontinuous flaws that are not completely removed by thermal annealing and are still observed in the thermally annealed MWCNTs even though the as-grown MWCNTs possess an intermediate level of crystallinity (R = 0.31) (Shirasu, et al, 2017b). 3.8 ± 1.5 227 ± 103 2.0 ± 0.4 a : Shirasu, et al, (2017b) Next, the thermal expansion property of the aligned MWCNT reinforced epoxy composites was evaluated. The variations of the thermal strain of the pure epoxy and composites in the MWCNT alignment direction as a function of temperature difference are shown in Fig.…”

Section: Resultsmentioning

confidence: 99%

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Mechanical and thermal expansion properties of aligned carbon nanotube reinforced epoxy composites

Shirasu

Tamaki

Yamamoto

et al. 2019

Mechanical Engineering Journal

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Aligned MWCNT/epoxy composites made with the three types of the multi-walled carbon nanotubes (MWCNTs) with different thermal annealing temperature have been prepared, and the tensile tests and thermal expansion tests of the composites in the MWCNT alignment direction were conducted to evaluate the effects of crystallinity of MWCNTs on the mechanical and thermal expansion properties of aligned MWCNT reinforced epoxy composites. Additionally, the coefficients of thermal expansion (CTEs) of the MWCNTs in the axial direction were computed by using the Young's modulus of the MWCNTs and the CTE of the composites in Turner's model. The annealing temperatures of the MWCNTs were 2400˚C and 2900˚C. It was shown that the thermal annealing of MWCNTs was effective for improving the crystallinity of the MWCNTs, while it had no major effects on both tensile strength and Young's modulus of the composites. This is mainly because the thermally annealed MWCNTs themselves possessed almost comparable nominal tensile strength (~4-5 GPa) and Young's modulus (~200 GPa) compared with the as-grown MWCNTs. On the other hand, we demonstrated by thermal expansion testing that the thermal contraction of the composites in the nanotube alignment direction was observed by the addition of MWCNTs. All the MWCNTs possessed negative CTEs and the CTEs tend to become more negative with increasing annealing temperature. This is probably because of a decrease in the number of small defects (vacancies and Stone-Wales defects) and intershell cross-linking defects associated with sp 3 carbons, and an increase in the sp 2 carbons owing to the high-temperature thermal annealing.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

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Mechanical and thermal expansion properties of aligned carbon nanotube reinforced epoxy composites

Shirasu

Tamaki

Yamamoto

et al. 2019

Mechanical Engineering Journal

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“…In these studies, the tensile strength was calculated from either the fractured cross-sectional area (effective strength) or the cross-sectional area of the outermost layer of the MWCNT. Few research groups have examined the nominal (or engineering) strength and its Weibull distribution, which are required for investigations of crack bridging characteristics and mechanical properties of composites reinforced with MWCNTs (a detailed discussion is given in [52]). Yu et al [37] calculated the nominal tensile strengths to be in the range of 1.4-2.9 GPa, which is much lower than the effective tensile strength (11-63 GPa).…”

Section: Introductionmentioning

confidence: 99%

“…Here, we review our recent studies in which the strength properties of individual MWCNTs synthesized by a CVD method, followed by a series of high-temperature annealing steps that culminate with annealing at 2900°C, are investigated by a manipulator tool operated inside an SEM [52][53][54]. The relationship between the MWCNT structure and strength properties of MWCNTs with a significantly different nanostructure is investigated through tensile tests of individual MWCNTs, transmission electron microscope (TEM) observations, and Raman spectroscopy analysis.…”

Section: Introductionmentioning

confidence: 99%

Mechanical and Fracture Properties of Carbon Nanotubes

Shirasu¹,

Yamamoto²,

Nélias³

et al. 2018

Carbon Nanotubes - Recent Progress

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Carbon nanotubes (CNTs) have attracted much interest because of their superior electrical, thermal, and mechanical properties. These unique properties of CNTs have come to the attention of many scientists and engineers worldwide, eager to incorporate these novel materials into composites and electronic devices. However, before the utilization of these materials becomes mainstream, it is necessary to develop protocols for tailoring the material properties, so that composites and devices can be engineered to given specifications. In this chapter, we review our recent studies, in which we investigate the nominal tensile strength and strength distribution of multi-walled CNTs (MWCNTs) synthesized by the catalytic chemical vapor deposition (CVD) method, followed by a series of high-temperature annealing steps that culminate with annealing at 2900°C. The structural-mechanical relationships of such MWCNTs are investigated through tensile-loading experiments with individual MWCNTs, Weibull-Poisson statistics, transmission electron microscope (TEM) observation, and Raman spectroscopy analysis.

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