Mechanical Strength of Nanoporous Graphene as a Desalination Membrane

Cohen-Tanugi, David; Grossman, Jeffrey C.

doi:10.1021/nl502399y

Cited by 244 publications

(172 citation statements)

References 44 publications

(78 reference statements)

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“…The elastic modulus then decreases roughly linearly with increasing defect density. This relationship was similarly found recently in [46] for nanoporous graphene with larger pore sizes. At the largest porosity we considered in this work (12%), the elastic modulus drops by around 80%.…”

Section: Random and Uniformly Distributed Vacancy Defectssupporting

confidence: 86%

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Mechanical properties of pristine and nanoporous graphene

Anastasi

Ritos

Cassar

et al. 2016

Molecular Simulation

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We present molecular dynamics simulations of monolayer graphene under uniaxial tensile loading. The Morse, bending angle, torsion and Lennard-Jones potential functions are adopted within the mdFOAM library in the OpenFOAM software, to describe the molecular interactions in graphene. A well-validated graphene model using these set of potentials is not yet available. In this work, we investigate the accuracy of the mechanical properties of graphene when derived using these simpler potentials, compared to the more commonly used complex potentials such as the Tersoff-Brenner and AIREBO potentials. The computational speed up of our approach, which scales O(1.5N), where N is the number of carbon atoms, enabled us to vary a larger number of system parameters, including graphene sheet orientation, size, temperature and concentration of nanopores. The resultant effect on the elastic modulus, fracture stress and fracture strain is investigated. Our simulations show that graphene is anisotropic, and its mechanical properties are dependant on the sheet size. An increase in system temperature results in a significant reduction in the fracture stress and strain. Simulations of nanoporous graphene were created by distributing vacancy defects, both randomly and uniformly, across the lattice. We find that the fracture stress decreases substantially with increasing defect density. The elastic modulus was found to be constant up to around 5% vacancy defects, and decreases for higher defect densities. ARTICLE HISTORY

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Section: Random and Uniformly Distributed Vacancy Defectssupporting

confidence: 86%

“…This is caused because the latter contains a wider range of defect sizes, having pores which are larger and more susceptible to fracture as noted in [46].…”

Section: Random and Uniformly Distributed Vacancy Defectsmentioning

confidence: 99%

Mechanical properties of pristine and nanoporous graphene

Anastasi

Ritos

Cassar

et al. 2016

Molecular Simulation

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“…1,2,3 Most studies to date have considered an idealized, single-layer system with variations in several key parameters (i.e., nanopore size, separation, chemistry, or substrate morphology), with the hope of guiding the experimental synthesis of NPG membranes. 2,3,4 Although multiple efforts have targeted the synthesis of large-scale graphene films, 5 producing perfect monolayer graphene over large areas remains highly challenging experimentally. In particular, the primary method that has been used to date for synthesizing graphene sheets, chemical vapor deposition (CVD), results in substantial multilayer coverage, in addition to Stone-Wales (5-7 ring) defects, 6 tears, and other intrinsic defects.…”

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confidence: 99%

Multilayer Nanoporous Graphene Membranes for Water Desalination

2016

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While single-layer nanoporous graphene (NPG) has shown promise as a reverse osmosis (RO) desalination membrane, multilayer graphene can be synthesized more economically than the single-layer material. In this work, we build upon the knowledge gained to date toward single-layer graphene to explore how multilayer NPG might serve as a RO membrane in water desalination using classical molecular dynamic simulations.We show that, while multilayer NPG exhibits similarly promising desalination properties to single-layer membranes, their separation performance can be designed by manipulating various configurational variables in the multilayer case. This work establishes an atomic-level understanding of the effects of additional NPG layers, layer separation, and pore alignment on desalination performance, providing useful guidelines for the design of multilayer NPG membranes.

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“…From a practical point of view, it remains crucial to understand the mechanical integrity of CTF membranes and the design of supporting substrates under the large hydraulic pressures of RO desalination processes. 31 In particular, we model the mechanical integrity of CTF--1 membranes against applied hydraulic RO pressure using the approach recently employed by Cohen--Tanugi et al 32 MD simulations were used to estimate the intrinsic mechanical properties of CTF membranes including fracture stress, Young's modulus, and Poisson's ratio, whereas continuum fracture mechanics was used to determine the stress experienced by the CTF--1 membrane as a function of substrate pore radius at a macroscopic scale. In the MD simulations, we used reactive force fields (ReaxFF) with parameters from two different sets (i.e., Budzien et al and Strachan et al) 33,34 to describe the chemical bonding of the CTF--1 framework.…”

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confidence: 99%

Two-dimensional covalent triazine framework as an ultrathin-film nanoporous membrane for desalination

2015

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We computationally demonstrate that two--dimensional covalent traizine frameworks (CTFs) provide opportunties in water desalination. By varying the chemical building blocks, the pore structure, chemistry, and membrane performance can be designed, leading to two orders of mangnutide higher water permeability than polyamide membranes while maintaining excellent ability to reject salts.Water scarcity is one of the most prominent challenges in modern society. 1,2 Due to the rapid growth of the world population and the accelerated industrialization of developing countries, fresh water has become increasingly scarce. Although 75% of the earth's surface is covered with water, more than 97% of it is seawater that cannot be used directly. Much of the remaining fresh water is locked in glaciers and snowfields, leaving less than 1% of the world's water available for human consumption. Despite the vast availability of seawater, the production of fresh water using processes that separate salt ions from saline water (i.e., desalination) remains negligible (less than 1%) when compared to global demand, primarily due to high costs and large energy consumption. 3 To facilitate clean water production via desalination, much recent attention has been given to improving the cost--effectiveness and energy--efficiency of reverse osmosis (RO) desalination processes, which account for roughly two thirds of installed capacity. In particular, new membranes with enhanced water permeability compared to currently available polyamide--based membranes may have an important role to play in lowering energy consumption. 4 Several nanostructured materials have been previously investigated as promising membrane candidates such as carbon nanotubes (CNTs) 5,6,7 and zeolites 8,9 . Despite CNTs' high water permeability, 5 membranes based on CNTs exhibit poor salt rejection, and it remains challenging to fabricate membranes with dense, well--aligned nanotubes. 6,7 Zeolite membranes, on the other hand, possess three--dimensional networks that can effectively reject salt ions 8 but show relatively low water permeability. 9 Recently, nanoporous one--atom--thick graphene, the thinnest possible membrane made from matter, has drawn considerable attention and been shown computationally to provide significantly enhanced permeability compared to polyamide while maintaining excellent ability to reject salt. 10 Moreover, recent work of Surwade et al. has further experimentally realized such single--layered nanoporous graphene membranes and demonstrated their potential in desalination at the lab scale. 11 However, the production of nanoporous graphene membranes with perfectly sized nanopores still remains a great challenge. Moreover, to allow unprecedentedly high water fluxes, it is of great importance to achieve a pore density as high as possible while preventing pores from overlapping, a goal best achieved with a well--ordered pore structure. Seeking membranes with naturally ordered pores of an ideal size presents an important alternative to nanoporous graphene m...

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Mechanical Strength of Nanoporous Graphene as a Desalination Membrane

Cited by 244 publications

References 44 publications

Mechanical properties of pristine and nanoporous graphene

Mechanical properties of pristine and nanoporous graphene

Multilayer Nanoporous Graphene Membranes for Water Desalination

Two-dimensional covalent triazine framework as an ultrathin-film nanoporous membrane for desalination

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