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graphene

msaeidi's picture

High thermal conductivity through simultaneously aligned polyethylene lamellae and graphene nanoplatelets

The effect of simultaneous alignment of polyethylene (PE) lamellae and graphene nanoplatelets (GnP) on thermal conductivity (k) of PE-GnP composites is investigated. Measurements reveal a large increase of 1100% in k of the aligned PE-GnP composite using 10 weight% GnPs relative to unoriented pure PE. Rate of increase of k with applied strain for the pure PE-GnP composite with 10 wt% GnP is found to be almost a factor of two higher than the pure PE sample, pointing to the beneficial effect of GnP alignment on k enhancement.

Jingjie Yeo's picture

Unusually low and density-insensitive thermal conductivity of three-dimensional gyroid graphene

http://dx.doi.org/10.1039/C7NR04455K Graphene has excellent mechanical, thermal and electrical properties. However, there are limitations in utilizing monolayers of graphene for mechanical engineering applications due to its atomic thickness and lack of bending rigidity. Synthesizing graphene aerogels or foams is one approach to utilize graphene in three-dimensional bulk forms. Recently, graphene with a gyroidal geometry has been proposed.

exw569's picture

Postdoctoral position in nanomechanics of 2D nanomaterials

The School of Engineering and Materials Science at Queen Mary University of London has a vacancy for a Postdoctoral Research Assistant (PDRA) to develop computational models of ultra-flexible 2D nanomaterials in sheared liquids, using techniques borrowed from computational fluid and solid mechanics.

Shuze Zhu's picture

Compressible, Dense, Three-Dimensional Holey Graphene Monolithic Architecture

We demonstrated outstanding compressibility of holey graphene nanosheets, which is impossible for pristine graphene. Holey graphene powder can be easily compressed into dense and strong monoliths with different shapes at room temperature without using any solvents or binders. 

ACS Nano, Article ASAP, http://pubs.acs.org/doi/abs/10.1021/acsnano.7b00227

 

qing.peng's picture

The normal-auxeticity mechanical phase transition in graphene

When a solid object is stretched, in general, it shrinks transversely. However, the abnormal ones are auxetic, which exhibit lateral expansion, or negative Poisson ratio. While graphene is a paradigm 2D material, surprisingly, graphene converts from normal to auxetic at certain strains. Here, we show via molecular dynamics simulations that the normal-auxeticity mechanical phase transition only occurs in uniaxial tension along the armchair direction or the nearest neighbor direction. Such a characteristic persists at temperatures up to 2400 K.

susanta's picture

Funded Ph.D. position in the Department of Mechanical Engineering- Engineering Mechanics at the Michigan Technological University

We are looking for a self-motivated PhD student to study Multi-Scale Material Modeling for different material systems such as Graphene and Polymeric Materials. This position is supported by the MEEM Department at MTU. This project will draw ideas from various subjects including Computational Mechanics and Materials Physics.

The candidate would have access to the advanced computing facilities, collaborations with researchers in other universities, and experimental collaborations. 

On structured surfaces with defects: geometry, strain incompatibility, internal stress, and natural shapes

Given a distribution of defects on a structured surface, such as those represented by 2-dimensional crystalline materials, liquid crystalline surfaces, and thin sandwiched shells, what is the resulting stress field and the deformed shape? Motivated by this concern, we first classify, and quantify, the translational, rotational, and metrical defects allowable over a broad class of structured surfaces. With an appropriate notion of strain, the defect densities are then shown to appear as sources of strain incompatibility.

Jingjie Yeo's picture

Free-standing graphene slit membrane for enhanced desalination

http://dx.doi.org/10.1016/j.carbon.2016.09.043 This study considers two novel ideas to further explore and enhance the graphene membrane for desalination. Firstly, while earlier molecular dynamics (MD) simulations studies have used frozen membranes, free-standing membrane is considered here. Since 2D membranes are usually embedded on porous support in the experimental reverse osmosis (RO) process, the free-standing membrane can more accurately model the behavior expected during operation.

Antonino Favata's picture

Graphene is softer to bend when stretched and bent and harder to stretch when bent and moderately stretched

 

In the attached paper, we have shown that concomitant bending and stretching, whatever their value, concur to make bending stiffness decrease; moreover, concomitant bending and stretching make the stretching stiffness (or the Young modulus) increase until the applied forces reach a threshold value, then they make it decrease. Said differently, graphene is softer to bend when stretched and bent and harder to stretch when bent and moderately stretched.

 

Antonino Favata's picture

An analytical benchmark for MD codes: testing and correcting LAMMPS

In the attached paper, recently appeared on Computer Physics Communications, we have proposed an analytical benchmark and a simple consistent Mathematica program for graphene and carbon nanotubes, that may serve to test any molecular dynamics code implemented with REBO potentials. By exploiting the benchmark, we checked results produced by LAMMPS (Large-scale Atomic/Molecular Massively Parallel Simulator) when adopting the second generation Brenner potential, we made evident that this code in its current implementation produces results which are offset from those of the benchmark by a significant amount, and provided evidence of the reason.

Harley T. Johnson's picture

A critical thickness condition for graphene and other 2D materials

B. C. McGuigan, P. Pochet, and H. T. Johnson, Critical thickness for interface misfit dislocation formation in two-dimensional materials, Phys. Rev. B 93, 214103, 2016.

URL: http://link.aps.org/doi/10.1103/PhysRevB.93.214103

Harold S. Park's picture

Journal Club Theme of June 2016: 2D Materials: Current and Future Directions

Two-Dimensional (2D) materials have been widely studied since the discovery of graphene in 2004.  Many of the initial works on the various 2D materials (graphene, MoS2 and other transition metal dichalcogenides, black phosphorus, and others like the monochalcogenides) by mechanicians focused on issues like ideal strength, and appropriate methods to calculate the bending modulus.  Some of these, and other issues, were reviewed by Sulin Zhang in a J-Club from March 2015 (http://imechanica

Jingjie Yeo's picture

Adsorption and Conformational Evolution of Alpha-Helical BSA Segments on Graphene: A Molecular Dynamics Study

http://dx.doi.org/10.1142/S1758825116500216 Molecular dynamics (MD) simulations are performed to investigate the adsorption mechanics and conformational dynamics of single and multiple bovine serum albumin (BSA) peptide segments on single-layer graphene through analysis of parameters such as the root-mean-square displacements, number of hydrogen bonds, helical content, inter- action energies, and motions of mass center of the peptides.

Harold S. Park's picture

Negative Poisson's Ratio in Single-Layer Graphene Ribbons

The Poisson's ratio characterizes the resultant strain in the lateral direction for a material under longitudinal deformation.  Though negative Poisson's ratios (NPR) are theoretically possible within continuum elasticity, they are most frequently observed in engineered materials and structures, as they are not intrinsic to many materials.  In this work, we report NPR in single-layer graphene ribbons, which results from the compressive edge stress induced warping of the edges.

Antonino Favata's picture

Graphene and Carbon Nanotubes are self-stressed

In the attached paper we have shown that graphene and carbon nanotubes are in a self-stress state in their natural equilibrium state, that is, the state prior to the application of external loads. We have identified different sources of self-stresses and accurately evaluated them; we have shown that they are by no means negligible with respect to load-related nanostresses.

Jingjie Yeo's picture

Peptide–Graphene Interactions Enhance the Mechanical Properties of Silk Fibroin

http://pubs.acs.org/doi/abs/10.1021/acsami.5b05615 Studies reveal that biomolecules can form intriguing molecular structures with fascinating functionalities upon interaction with graphene. Then, interesting questions arise. How does silk fibroin interact with graphene? Does such interaction lead to an enhancement in its mechanical properties?

Shuze Zhu's picture

Pseudomagnetic Fields in a Locally Strained Graphene Drumhead

Recent experiments reveal that a scanning tunneling microscopy (STM) probe tip can generate a highly localized strain field in a graphene drumhead, which in turn leads to pseudomagnetic fields in the graphene that can spatially confine graphene charge carriers in a way similar to a lithographically defined quantum dot (QD). While these experimental findings are intriguing, their further implementation in nanoelectronic devices hinges upon the knowledge of key underpinning parameters, which still remain elusive.

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