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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.


Two typical distributions of grain size.The polycrystalline graphene with the narrowed grain size distribution is generated from the Voronoi construction, while the polycrystalline graphene with the broad grain size distribution is generated from a continuous nucleation and growth construction that forms a Johnson-Mehl microstructure. For these two grain size distributions, the number of grain and the dimensions of the polycrystalline graphene sheet are maintained to be similar. As a result, the average grain size <d> and the number of GB junctions for both grain size distributions are also the same.
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f4: Two typical distributions of grain size.The polycrystalline graphene with the narrowed grain size distribution is generated from the Voronoi construction, while the polycrystalline graphene with the broad grain size distribution is generated from a continuous nucleation and growth construction that forms a Johnson-Mehl microstructure. For these two grain size distributions, the number of grain and the dimensions of the polycrystalline graphene sheet are maintained to be similar. As a result, the average grain size <d> and the number of GB junctions for both grain size distributions are also the same.

Mentions: We also consider the effect of the distribution of grain sizes on the mechanical properties of polycrystalline graphene. Figure 4 shows two typical grain size distributions of polycrystalline graphene, with the narrowed grain size distribution being generated from the Voronoi construction303132, and the broad grain size distribution being generated from a continuous nucleation and growth construction forming a Johnson-Mehl microstructure33. For both distributions, we maintain similar number of grains and do not vary the dimensions of the polycrystalline graphene sheet. As a result, the average grain size <d> and the number of GB junctions for both grain size distributions are maintained to be similar (note that the number of grains generated in a continuous nucleation and growth process is random and only an expected number of grains is obtained and not a fixed number). The breaking strength, along with the number of the GB junctions, for the polycrystalline graphene with both grain size distributions are listed in Table 1. It is noted that all the values are also averaged from 5 randomly generated samples with different initial grain configurations but the same average grain size and grain size distribution. Apparently, the width of the grain size distribution does not have any significant effect on the breaking strength. This finding further supports our above statement that the breaking strength of polycrystalline graphene is dictated by the GB junctions.


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)

Two typical distributions of grain size.The polycrystalline graphene with the narrowed grain size distribution is generated from the Voronoi construction, while the polycrystalline graphene with the broad grain size distribution is generated from a continuous nucleation and growth construction that forms a Johnson-Mehl microstructure. For these two grain size distributions, the number of grain and the dimensions of the polycrystalline graphene sheet are maintained to be similar. As a result, the average grain size <d> and the number of GB junctions for both grain size distributions are also the same.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

f4: Two typical distributions of grain size.The polycrystalline graphene with the narrowed grain size distribution is generated from the Voronoi construction, while the polycrystalline graphene with the broad grain size distribution is generated from a continuous nucleation and growth construction that forms a Johnson-Mehl microstructure. For these two grain size distributions, the number of grain and the dimensions of the polycrystalline graphene sheet are maintained to be similar. As a result, the average grain size <d> and the number of GB junctions for both grain size distributions are also the same.
Mentions: We also consider the effect of the distribution of grain sizes on the mechanical properties of polycrystalline graphene. Figure 4 shows two typical grain size distributions of polycrystalline graphene, with the narrowed grain size distribution being generated from the Voronoi construction303132, and the broad grain size distribution being generated from a continuous nucleation and growth construction forming a Johnson-Mehl microstructure33. For both distributions, we maintain similar number of grains and do not vary the dimensions of the polycrystalline graphene sheet. As a result, the average grain size <d> and the number of GB junctions for both grain size distributions are maintained to be similar (note that the number of grains generated in a continuous nucleation and growth process is random and only an expected number of grains is obtained and not a fixed number). The breaking strength, along with the number of the GB junctions, for the polycrystalline graphene with both grain size distributions are listed in Table 1. It is noted that all the values are also averaged from 5 randomly generated samples with different initial grain configurations but the same average grain size and grain size distribution. Apparently, the width of the grain size distribution does not have any significant effect on the breaking strength. This finding further supports our above statement that the breaking strength of polycrystalline graphene is dictated by the GB junctions.

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.