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Journal Article•DOI•

Effect of grain boundaries on the interfacial behaviour of graphene-polyethylene nanocomposite

Akarsh Verma1, Avinash Parashar1, Muthukumaran Packirisamy2•
Indian Institute of Technology Roorkee1, Concordia University2
15 Mar 2019-Applied Surface Science (North-Holland)-Vol. 470, pp 1085-1092
TL;DR: In this article, the effect of grain boundaries on the interfacial properties of bi-crystalline graphene/polyethylene based nanocomposites was investigated, where molecular dynamics based atomistic simulations were performed in conjunction with the reactive force field parameters to capture atomic interactions within graphene and polyethylene atoms.
About: This article is published in Applied Surface Science.The article was published on 2019-03-15 and is currently open access. It has received 69 citations till now. The article focuses on the topics: Graphene & Nanocomposite.

Summary (2 min read)

Jump to: [1. Introduction] – [2. Modelling details] – [3.1. Effect of defected graphene on the tensile strength of PE nanocomposites] – [3.2. Effect of defected graphene on the shear strength of PE nanocomposites] – [3.3. Effect of defected graphene on the cohesive strength of PE nanocomposites] and [4.0 Conclusion]

1. Introduction

  • Graphene is a two-dimensional (2D) nanomaterial with honeycomb crystal lattice domain [1, 2] .
  • Due to exceptional mechanical, thermal and electrical properties, graphene is emerging as a potential candidate for the reinforcement of nanocomposites [3] [4] [5] .
  • They attributed higher interfacial strength for relatively stronger covalent bonds formed by the functional groups as compared to weak non-bonded van der Waals interactions.
  • Several computational and experimental works have already been performed to characterize the mechanical properties of bi-crystalline graphene [38] [39] [40] [41] [42] .

2. Modelling details

  • The classical mechanics based MD approach was used to perform all the simulations.
  • In all these aforementioned configurations, the bi-crystals of graphene nanosheets were randomly oriented in the PE matrix for maintaining the realistic condition.
  • Finally, the system was relaxed again under the influence of NPT ensemble at 100 K for a total time period of 25 ps.
  • For avoiding the stress fluctuations during tensile strain analysis, Velocity-Verlet algorithm with a relatively smaller integration time step of 0.15 fs was opted.

3.1. Effect of defected graphene on the tensile strength of PE nanocomposites

  • ReaxFF potential parameters have already been validated for simulating the mechanical properties of pristine and bi-crystalline graphene in their previous articles [41, 57] .
  • Thus, for the same percentage of reinforcement in nanocomposite, a higher degree of interfacial strength is desirable; which can be achieved by either functionalising the interface or inducing geometrical defects in the nanofillers domain.
  • Stress-strain responses for different types of bi-crystalline graphene reinforced PE nanocomposites are plotted in Fig. 3 and Fig. 4 for AC and ZZ configurations of graphene, respectively.
  • These explanations can also be found and related to their earlier research articles [41, 42] in conjunction with the recommendation of Grantab et al. [40] work; hence, it complements their current efforts.
  • In each of the simulations, uniaxial tensile loading was applied perpendicular as well as parallel to the GB.

3.2. Effect of defected graphene on the shear strength of PE nanocomposites

  • After predicting tensile strength of nanocomposites, next set of simulations were performed to investigate the shear strength of the interface between graphene and PE matrix.
  • In order to capture the shear strength at the interface, simulations were performed with periodic boundary conditions imposed only in two principal directions, whereas the third principal direction was used to pull the graphene out of polymer matrix as illustrated in Fig. 7 .
  • In the graphene reinforced PE system, the pristine and bi-crystalline graphene nanosheets were pulled out of the PE matrix with a velocity of 0.0001 Å/fs along x-direction (non-periodic) and the resulting shear force on the graphene nanosheets in the pullout direction was plotted in Fig. 8 .
  • The resulting maximum interfacial shear strength (τ xy-max ) was calculated with the help of surface area of graphene nanosheet as per equation 4.

3.3. Effect of defected graphene on the cohesive strength of PE nanocomposites

  • In the last subsection, simulations were performed to estimate the cohesive strength of interface for different configurations of nanocomposites.
  • It can be inferred from the trend plotted in Fig. 10 that similar to shear strength, normal interfacial stress of nanocomposite also improved significantly, while reinforced with bicrystalline graphene as compared to pristine graphene.
  • Hence, these GB act as the path for load transfer to take place and helps in establishing a strong mechanical interlocking with high cohesive strength.
  • Higher mis-orientation angle GB configurations possess higher normal interfacial strength and vice-versa.
  • On a comparing note (Fig. 8 and Fig. 10 ), shear stress values at the interface are less than the cohesive/normal stress.

4.0 Conclusion

  • In summary, simulations were performed to study the reinforcing capabilities of bi-crystalline graphene as compared to pristine graphene nanosheet.
  • The authors also perceived that wrinkling with substantial out-of-plane deformation in bi-crystalline graphene containing higher mis-orientation angle GB resulted in more number of adhesion points and better non-bonding interaction at the interface; which were the main mechanisms causing an increment in the tensile strength.
  • But emerges as a superior reinforcement for polymer based nanocomposites.

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Figures (3)
Citations
More filters
Fast parallel algorithms for short-range molecular dynamics

[...]

Steven J. Plimpton1•
Sandia National Laboratories1
01 May 1993
TL;DR: Comparing the results to the fastest reported vectorized Cray Y-MP and C90 algorithm shows that the current generation of parallel machines is competitive with conventional vector supercomputers even for small problems.
Abstract: Three parallel algorithms for classical molecular dynamics are presented. The first assigns each processor a fixed subset of atoms; the second assigns each a fixed subset of inter-atomic forces to compute; the third assigns each a fixed spatial region. The algorithms are suitable for molecular dynamics models which can be difficult to parallelize efficiently—those with short-range forces where the neighbors of each atom change rapidly. They can be implemented on any distributed-memory parallel machine which allows for message-passing of data between independently executing processors. The algorithms are tested on a standard Lennard-Jones benchmark problem for system sizes ranging from 500 to 100,000,000 atoms on several parallel supercomputers--the nCUBE 2, Intel iPSC/860 and Paragon, and Cray T3D. Comparing the results to the fastest reported vectorized Cray Y-MP and C90 algorithm shows that the current generation of parallel machines is competitive with conventional vector supercomputers even for small problems. For large problems, the spatial algorithm achieves parallel efficiencies of 90% and a 1840-node Intel Paragon performs up to 165 faster than a single Cray C9O processor. Trade-offs between the three algorithms and guidelines for adapting them to more complex molecular dynamics simulations are also discussed.

29,323 citations

Journal Article•
Effect of covalent functionalisation on thermal transport across graphene-polymer interfaces

[...]

Ye Wang, Haifei Zhan, Yang Xiang, Chun Yang, C.M. Wang, Yingyan Zhang 
07 May 2015-Science & Engineering Faculty
TL;DR: In this article, the interfacial thermal resistance for polymer composites reinforced by various covalently functionalised graphene was investigated by using molecular dynamics simulations, and the results showed that the covalent functionalization in graphene plays a significant role in reducing the graphene-paraffin interfacial temperature resistance.
Abstract: This paper is concerned with the interfacial thermal resistance for polymer composites reinforced by various covalently functionalised graphene. By using molecular dynamics simulations, the obtained results show that the covalent functionalisation in graphene plays a significant role in reducing the graphene-paraffin interfacial thermal resistance. This reduction is dependent on the coverage and type of functional groups. Among the various functional groups, butyl is found to be the most effective in reducing the interfacial thermal resistance, followed by methyl, phenyl and formyl. The other functional groups under consideration such as carboxyl, hydroxyl and amines are found to produce negligible reduction in the interfacial thermal resistance. For multilayer graphene with a layer number up to four, the interfacial thermal resistance is insensitive to the layer number. The effects of the different functional groups and the layer number on the interfacial thermal resistance are also elaborated using the vibrational density of states of the graphene and the paraffin matrix. The present findings provide useful guidelines in the application of functionalised graphene for practical thermal management.

107 citations

Journal Article•DOI•
Mechanical, microstructural, and thermal characterization insights of pyrolyzed carbon black from waste tires reinforced epoxy nanocomposites for coating application

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Akarsh Verma1, Kriti Baurai2, M. R. Sanjay3, Suchart Siengchin3•
Indian Institute of Technology Roorkee1, Delhi Technological University2, King Mongkut's University of Technology North Bangkok3
01 Jan 2020-Polymer Composites

103 citations

Journal Article•DOI•
Mechanical and tribological properties of nanocomposites incorporated with two-dimensional materials

[...]

Zhengjia Ji1, Zhengjia Ji2, Lin Zhang2, Guoxin Xie2, Wenhu Xu3, Dan Guo2, Jianbin Luo2, Braham Prakash2 •
Qinghai University1, Tsinghua University2, Nanchang University3
12 Jun 2020-Friction
TL;DR: A critical review of recent mechanical and tribological studies based on 2DNBCs has been undertaken in this article, where the preparation strategies, intrinsic mechanical properties, friction and lubrication performances, strengthening mechanisms, influencing factors, and potential applications have been comprehensively discussed.
Abstract: In recent years, attempts to improve the mechanical properties of composites have increased remarkably owing to the inadequate utilization of matrices in demanding technological systems where efficiency, durability, and environmental compatibility are the key requirements. The search for novel materials that can potentially have enhanced mechanical properties continues. Recent studies have demonstrated that two-dimensional (2D) nanomaterials can act as excellent reinforcements because they possess high modulus of elasticity, high strength, and ultralow friction. By incorporating 2D nanomaterials in a composite, 2D nanomaterial-based composites (2DNBCs) have been developed. In view of this, a critical review of recent mechanical and tribological studies based on 2DNBCs has been undertaken. Matrices such as polymers, ceramics, and metals, as well as most of the representative 2D nanomaterial reinforcements such as graphene, boron nitride (BN), molybdenum disulfide (MoS2), and transition metal carbides and nitrides (MXenes) have been included in this review. Their preparation strategies, intrinsic mechanical properties, friction and lubrication performances, strengthening mechanisms, influencing factors, and potential applications have been comprehensively discussed. A brief summary and prospects are given in the final part, which would be useful in designing and fabricating advanced 2D nanocomposites in the future.

73 citations

Journal Article•DOI•
Experimental and Computational Studies to Analyze the Effect of h-BN Nanosheets on Mechanical Behavior of h-BN/Polyethylene Nanocomposites

[...]

Ankur Chaurasia1, Akarsh Verma1, Avinash Parashar1, Rahul S. Mulik1•
Indian Institute of Technology Roorkee1
25 Jul 2019-Journal of Physical Chemistry C
TL;DR: In this paper, experimental and classical mechanics-based approaches have been used to study the reinforcing capabilities of hexagonal boron nitride (h-BN) nanosheets for polyethylene (PE)-based nanocomposites.
Abstract: In this article, experimental and classical mechanics-based approaches have been used to study the reinforcing capabilities of hexagonal boron nitride (h-BN) nanosheets for polyethylene (PE)-based nanocomposites. Experiments were performed with h-BN nanoflakes and high-density polyethylene-based nanocomposites. Experimental results reported 27.0 and 64.1% improvement in tensile strength and Young’s modulus for 5 wt % h-BN loading in PE, respectively. Experimental analysis helps in developing a micro- and macrolevel understanding of the mechanical behavior of BN/PE nanocomposites, whereas the strength of these nanocomposites is governed by interfacial properties. Interfacial properties can be easily captured using atomistic simulations such as molecular dynamics. Molecular dynamics-based atomistic models were developed to study the effect of aspect ratio, weight fraction, morphology, distribution of h-BN nanosheets, and strain rate loading on mechanical properties of the nanocomposite. A reactive force fie...

67 citations

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TL;DR: In this article, a detailed comparison of the forces involved in the two methods is made and it is shown that the stress method makes more efficient use of the data and yields a result of greater precision than does the virial method.
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01 Dec 2014-Carbon
TL;DR: In this paper, the authors performed first-principle calculations based on density functional theory (DFT) to investigate adsorption of lithium (Li) on graphene with divacancy and Stone-Wales defects.

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Frequently Asked Questions (16)
Q1. What contributions have the authors mentioned in the paper "Effect of grain boundaries on the interfacial behaviour of graphene-polyethylene nanocomposite" ?

Aim of this article was to investigate the effect of grain boundaries on the interfacial properties of bi-crystalline graphene/polyethylene based nanocomposites. 

Chemical vapour deposition is the most commonly used technique for synthesising larger size graphene, but it results in polycrystalline structure. 

Due to exceptional mechanical, thermal and electrical properties, graphene is emerging as a potential candidate for the reinforcement of nanocomposites [3-5]. 

Higher mis-orientation angle configurations lead to redistribution of stress uniformly throughout the bi-crystalline graphene sheet that maximizes the load transfer phenomenon and helps in improving the tensile strength. 

It is predicted from the post processing of dump files that higher mis-orientation angle configurations contain more energetic sites (due to high density of dislocations) relative to lower mis-orientation angles for a given weight percentage of graphene in PE; therefore, there would be more wrinkling in higher mis-orientation angles and thus high tensile strength. 

The authors also perceived that wrinkling with substantial out-of-plane deformation in bi-crystalline graphene containing higher mis-orientation angle GB resulted in more number of adhesion points and better non-bonding interaction at the interface; which were the main mechanisms causing an increment in the tensile strength. 

Due to limitations associated with the synthesising techniques, nanomaterials e.g. large size graphene nanosheets are synthesised with geometrical defects such as vacancies, dislocations and grain boundaries (GB) [34, 35]. 

Liu et al. [33] concluded in their work that grafting of graphene with polymer chains helps in improving the shear strength as well as graphene’s dispersion in the polymer matrix. 

Snapshots showing crazing and voids formation in PE when subjected to tensile loadAfter predicting tensile strength of nanocomposites, next set of simulations were performed to investigate the shear strength of the interface between graphene and PE matrix. 

better interfacial properties have been predicted from the interaction energy trend for bi-crystalline graphene nanocomposites as compared to pristine graphene. 

In order to capture the shear strength at the interface, simulations were performed with periodic boundary conditions imposed only in two principal directions, whereas the third principal direction was used to pull the graphene out of polymer matrix as illustrated in Fig.7. 

It was also predicted from the tensile deformation of above designed nanocomposites that after achieving the maximum tensile strength, permanent deformation in the form of voids and crazing starts generating in PE matrix as shown in Fig.6. 

In the graphene reinforced PE system, the pristine and bi-crystalline graphene nanosheets were pulled out of the PE matrix with a velocity of 0.0001 Å/fs along x-direction (non-periodic) and the resulting shear force on the graphene nanosheets in the pullout direction was plotted in Fig.8. 

Due to increased interaction, atoms configuring GB atoms were actually pulled by the PE chains that results in inducing wrinkles (crests and troughs) in the 2D bi-crystalline graphene; in contrast, the pristine graphene structure in PE/GRP nanocomposite relatively remained flattened (minimal out of plane displacement) during tensile deformation as captured in Fig.5. 

It can also be inferred from the stress-strain responses plotted in Fig.3 and Fig.4 that increment in tensile strength of nanocomposites is more prominent in bi-crystalline graphene containing higher mis-orientation angles. 

All the simulations help in concluding that bi-crystalline graphene is a superior reinforcement for developing the future nanocomposites as compared to pristine PE nanocomposites.