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Inverse pseudo Hall-Petch relation in polycrystalline graphene.

Sha ZD, Quek SS, Pei QX, Liu ZS, Wang TJ, Shenoy VB, Zhang YW - Sci Rep (2014)

Bottom Line: We also show that its breaking strength and average grain size follow an inverse pseudo Hall-Petch relation, in agreement with experimental measurements.Further, we find that this inverse pseudo Hall-Petch relation can be naturally rationalized by the weakest-link model, which describes the failure behavior of brittle materials.Our present work reveals insights into controlling the mechanical properties of polycrystalline graphene and provides guidelines for the applications of polycrystalline graphene in flexible electronics and nano-electronic-mechanical devices.

View Article: PubMed Central - PubMed

Affiliation: International Center for Applied Mechanics, State Key Laboratory for Strength and Vibration of Mechanical Structures, Xi'an Jiaotong University, Xi'an 710049, China.

ABSTRACT
Understanding the grain size-dependent failure behavior of polycrystalline graphene is important for its applications both structurally and functionally. Here we perform molecular dynamics simulations to study the failure behavior of polycrystalline graphene by varying both grain size and distribution. We show that polycrystalline graphene fails in a brittle mode and grain boundary junctions serve as the crack nucleation sites. We also show that its breaking strength and average grain size follow an inverse pseudo Hall-Petch relation, in agreement with experimental measurements. Further, we find that this inverse pseudo Hall-Petch relation can be naturally rationalized by the weakest-link model, which describes the failure behavior of brittle materials. Our present work reveals insights into controlling the mechanical properties of polycrystalline graphene and provides guidelines for the applications of polycrystalline graphene in flexible electronics and nano-electronic-mechanical devices.

No MeSH data available.


Related in: MedlinePlus

The correlations between the grain size and mechanical properties.(a) The tensile stress-strain curves for polycrystalline graphene with the average grain sizes of 3, 5, 7, 9, and 11 nm. All simulations are performed at a strain rate of 4 × 107 s−1. (b–d) The trends of the Young's modulus, the failure strain, and the breaking strength as a function of the grain size, respectively.
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f2: The correlations between the grain size and mechanical properties.(a) The tensile stress-strain curves for polycrystalline graphene with the average grain sizes of 3, 5, 7, 9, and 11 nm. All simulations are performed at a strain rate of 4 × 107 s−1. (b–d) The trends of the Young's modulus, the failure strain, and the breaking strength as a function of the grain size, respectively.

Mentions: The tensile stress-strain curves for polycrystalline graphene with an average grain size of 3, 5, 7, 9, and 11 nm are plotted in Fig. 2(a). Initially the gradient of the stress-strain curves increases as the applied strain increases, in agreement with the previous MD simulation results1925. This gradient increment is a characteristic of the entropic elastic behavior arising from erasing the wrinkle in a thin membrane structure25. As the applied strain is increased further, the polycrystalline graphene gradually flattens under stretching, the sp2 C–C bonds are directly stretched and as a result, the stress becomes linearly dependent on the applied strain. The slope of the stress-strain curve in this range gives the Young's modulus. Finally the polycrystalline graphene fails due to crack nucleation and propagation. The trends of the Young's modulus, the failure strain, and the breaking strength taken as the peak tensile stress, as a function of the average grain size are plotted in Fig. 2(b–d), respectively. For each selected value of the average grain size, we perform simulations on 5 randomly generated samples with the same average grain size but different initial grain configurations, and use the average of the 5 simulations to consider statistical fluctuations. With increasing grain size, the Young's modulus increases while the failure strain decreases, consistent with the previous MD simulations1619. For the breaking strength, it increases with the grain size, showing an inverse pseudo Hall-Petch relation.


Inverse pseudo Hall-Petch relation in polycrystalline graphene.

Sha ZD, Quek SS, Pei QX, Liu ZS, Wang TJ, Shenoy VB, Zhang YW - Sci Rep (2014)

The correlations between the grain size and mechanical properties.(a) The tensile stress-strain curves for polycrystalline graphene with the average grain sizes of 3, 5, 7, 9, and 11 nm. All simulations are performed at a strain rate of 4 × 107 s−1. (b–d) The trends of the Young's modulus, the failure strain, and the breaking strength as a function of the grain size, respectively.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4125985&req=5

f2: The correlations between the grain size and mechanical properties.(a) The tensile stress-strain curves for polycrystalline graphene with the average grain sizes of 3, 5, 7, 9, and 11 nm. All simulations are performed at a strain rate of 4 × 107 s−1. (b–d) The trends of the Young's modulus, the failure strain, and the breaking strength as a function of the grain size, respectively.
Mentions: The tensile stress-strain curves for polycrystalline graphene with an average grain size of 3, 5, 7, 9, and 11 nm are plotted in Fig. 2(a). Initially the gradient of the stress-strain curves increases as the applied strain increases, in agreement with the previous MD simulation results1925. This gradient increment is a characteristic of the entropic elastic behavior arising from erasing the wrinkle in a thin membrane structure25. As the applied strain is increased further, the polycrystalline graphene gradually flattens under stretching, the sp2 C–C bonds are directly stretched and as a result, the stress becomes linearly dependent on the applied strain. The slope of the stress-strain curve in this range gives the Young's modulus. Finally the polycrystalline graphene fails due to crack nucleation and propagation. The trends of the Young's modulus, the failure strain, and the breaking strength taken as the peak tensile stress, as a function of the average grain size are plotted in Fig. 2(b–d), respectively. For each selected value of the average grain size, we perform simulations on 5 randomly generated samples with the same average grain size but different initial grain configurations, and use the average of the 5 simulations to consider statistical fluctuations. With increasing grain size, the Young's modulus increases while the failure strain decreases, consistent with the previous MD simulations1619. For the breaking strength, it increases with the grain size, showing an inverse pseudo Hall-Petch relation.

Bottom Line: We also show that its breaking strength and average grain size follow an inverse pseudo Hall-Petch relation, in agreement with experimental measurements.Further, we find that this inverse pseudo Hall-Petch relation can be naturally rationalized by the weakest-link model, which describes the failure behavior of brittle materials.Our present work reveals insights into controlling the mechanical properties of polycrystalline graphene and provides guidelines for the applications of polycrystalline graphene in flexible electronics and nano-electronic-mechanical devices.

View Article: PubMed Central - PubMed

Affiliation: International Center for Applied Mechanics, State Key Laboratory for Strength and Vibration of Mechanical Structures, Xi'an Jiaotong University, Xi'an 710049, China.

ABSTRACT
Understanding the grain size-dependent failure behavior of polycrystalline graphene is important for its applications both structurally and functionally. Here we perform molecular dynamics simulations to study the failure behavior of polycrystalline graphene by varying both grain size and distribution. We show that polycrystalline graphene fails in a brittle mode and grain boundary junctions serve as the crack nucleation sites. We also show that its breaking strength and average grain size follow an inverse pseudo Hall-Petch relation, in agreement with experimental measurements. Further, we find that this inverse pseudo Hall-Petch relation can be naturally rationalized by the weakest-link model, which describes the failure behavior of brittle materials. Our present work reveals insights into controlling the mechanical properties of polycrystalline graphene and provides guidelines for the applications of polycrystalline graphene in flexible electronics and nano-electronic-mechanical devices.

No MeSH data available.


Related in: MedlinePlus