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We present the results of the molecular dynamics simulation of the deformation behavior of the graphene/Al composite. Morse potential parameters are considered and selected to describe interactions in the graphene/Al system. It is shown that the keeping at room temperature followed by the hydrostatic compression at 300 K and 600 K enables the preparation of strong composite materials. It is found that the graphene/Al composite formed at 600 K has the maximum strength limit and also demonstrates a high plasticity. It is revealed that due to a weak binding energy between graphene and Al during the deformation treatment, Al nanoparticles tend to coagulate. On the one hand, the occurrence of aluminum nanoparticles enhances the plasticity of the composite, but on the other hand, the composite is further destructed just on these nanoparticles. The obtained results contribute to a better understanding of the formation processes of composites based on crumpled graphene and Al nanoparticles. [ABSTRACT FROM AUTHOR]

Interatomic interaction potentials are compared using a molecular dynamics modeling method to choose the simplest, but most effective, model to describe the interaction of copper nanoparticles and graphene flakes. Three potentials are considered: (1) the bond-order potential; (2) a hybrid embedded-atom-method and Morse potential; and (3) the Morse potential. The interaction is investigated for crumpled graphene filled with copper nanoparticles to determine the possibility of obtaining a composite and the mechanical properties of this material. It is observed that not all potentials can be applied to describe the graphene–copper interaction in such a system. The bond-order potential potential takes into account various characteristics of the bond (for example, the angle of rotation and bond lengths); its application increases the simulation time and results in a strong interconnection between a metal nanoparticle and a graphene flake. The hybrid embedded-atom-method/Morse potential and the Morse potential show different results and lower bonding between graphene and copper. All the potentials enable a composite structure to be obtained; however, the resulting mechanical properties, such as strength, are different. [ABSTRACT FROM AUTHOR]

In this study, some features of molecular dynamics simulation for evaluating the mechanical properties of a Ni/graphene composite and analyzing the effect of incremental and dynamic tensile loading on its deformation are discussed. A new structural type of the composites is considered: graphene network (matrix) with metal nanoparticles inside. Two important factors affecting the process of uniaxial tension are studied: tension strain rate (5 × 10 − 3 ps − 1 and 5 × 10 − 4 ps − 1 ) and simulation temperature (0 and 300 K). The results show that the strain rate affects the ultimate tensile strength under tension: the lower the strain rate, the lower the critical values of strain. Tension at room temperature results in lower ultimate tensile strength in comparison with simulation at a temperature close to 0 K, at which ultimate tensile strength is closer to theoretical strength. Both simulation techniques (dynamic and incremental) can be effectively used for such a study and result in almost similar behavior. Fabrication technique plays a key role in the formation of the composite with low anisotropy. In the present work, uniaxial tension along three directions shows a big difference in the composite strength. It is shown that the ultimate tensile strength of the Ni/graphene composite is close to that of pure crumpled graphene, while the ductility of crumpled graphene with metal nanoparticles inside is two times higher. The obtained results shed the light on the simulation methodology which should be used for the study of the deformation behavior of carbon/metal nanostructures. [ABSTRACT FROM AUTHOR]

Defects in two-dimensional structures as graphene can considerably affect their mechanical and physical properties. Therefore, a systematic study of the time evolution of the defect dynamics in graphene is of high importance. The dynamics of edge dislocation dipoles in planar graphene at high temperatures have been studied by means of molecular dynamics simulation. Different dislocation motion scenarios for dislocation dipoles with arm length from 0 to 30 Å are revealed. Among such dislocation dipoles are Stone–Wales defect, where dislocations are strongly interacting in a dipole. The processes of annihilation of dislocations in dipole depending on the arm length and temperature are discussed. It is found that for dislocation dipoles with arm length l > 16 Å annihilation can easily occur at high temperatures. The present work provides a detailed description of dislocation motion at high temperatures. [Display omitted] • The dynamics of the dislocation dipoles at high temperatures is studied by molecular dynamics. • Basic algorithms of the dislocation movement are revealed and de- scribed. • It is shown that temperature can facilitate dislocation movement, but only for dipoles with small dipole arms. [ABSTRACT FROM AUTHOR]

The incorporation of metal nanoparticles into novel carbon structures, such as crumpled graphene (CG), is a promising way to obtain a composite with better mechanical properties. Molecular dynamics simulation is used to investigate the deformation behavior of Ni–graphene composites, obtained by high‐temperature treatment, under uniaxial tension. The effect of temperatures between 1000 and 2000 K as well as the effect of nanoparticle size and anisotropy of the structure on the mechanical properties of the composite are studied. It is found that temperature from 1000 to 2000 K slightly affects the process of composite formation under hydrostatic compression. During the elastic regime of tension of the composite, the same values of Young's modulus are found for structures obtained at different temperatures. However, the ratio of nickel and carbon atoms considerably affects the mechanical properties under uniaxial tension: the less the number of Ni atoms, the higher the composite strength. Two of the three considered morphologies demonstrate close Young modulus and high strength. It is shown that the important advantage of the proposed structure is its homogeneity, which results in almost isotropic deformation. The obtained results open new prospects in using CG for composite fabrication. [ABSTRACT FROM AUTHOR]

The size effect of nickel nanoparticles on the process of nickel–graphene composite formation is studied by molecular dynamics. It is shown that the best mixing of single structural elements in the general structure is achieved at high temperatures which cause fluctuations resulting in additional chemical bonds between graphene flakes. However, particle size is one of the most important structural factors affecting the composite structure: larger nanoparticles maintain their spherical shape even at high temperatures and prevent the formation of a uniform composite structure. The obtained results enrich our understanding of processes underlying the formation of composites based on crumpled graphene and metal nanoparticles. [ABSTRACT FROM AUTHOR]

Fabrication of Ni-graphene composite by hydrostatic pressure at finite temperatures or by the subsequent annealing is studied by molecular dynamics simulation. Crumpled graphene - the network of folded and crumpled graphene flakes connected by van-der-Waals bonds - is chosen as the matrix for Ni nanoclusters. It is found that hydrostatic compression at zero or room temperature cannot lead to the formation of the composite structure. Even strongly compressed crumpled graphene after unloading returned to the initial state of separated graphene flakes. However, annealing of the compressed structure at high temperature leads to the appearance of the valent bonds between neighbouring flakes. Simultaneously, hydrostatic compression at high temperature between 1000 and 2000 K leads to the better mixing of Ni atoms inside the structure and to the formation of strong covalent bonds between neighbouring flakes. [ABSTRACT FROM AUTHOR]

The effect of the size of nickel nanoparticles on the fabrication of a Ni–graphene composite by hydrostatic pressure at 0 K followed by annealing at 1000 and 2000 K is studied by molecular dynamics simulation. Crumpled graphene, consisting of crumpled graphene flakes interconnected by van der Waals forces is chosen as the matrix for the composite and filled with nickel nanoparticles composed of 21 and 47 atoms. It is found that the main factors that affect composite fabrication are nanoparticle size, the orientation of the structural units, and temperature of the fabrication process. The best stress–strain behavior is achieved for the Ni/graphene composite with Ni 47 nanoparticle after annealing at 2000 K. However, all of the composites obtained had strength property anisotropy due to the inhomogeneous distribution of pores in the material volume. [ABSTRACT FROM AUTHOR]

Understanding the structural behavior of graphene flake, which is the structural unit of bulk crumpled graphene, is of high importance, especially when it is in contact with the other types of atoms. In the present work, crumpled graphene is considered as storage media for two types of nanoclusters—nickel and hydrogen. Crumpled graphene consists of crumpled graphene flakes bonded by weak van der Waals forces and can be considered an excellent container for different atoms. Molecular dynamics simulation is used to study the behavior of the graphene flake filled with the nickel nanocluster or hydrogen molecules. The simulation results reveal that graphene flake can be considered a perfect container for metal nanocluster since graphene can easily cover it. Hydrogen molecules can be stored on graphene flake at 77 K, however, the amount of hydrogen is low. Thus, additional treatment is required to increase the amount of stored hydrogen. Remarkably, the size dependence of the structural behavior of the graphene flake filled with both nickel and hydrogen atoms is found. The size of the filling cluster should be chosen in comparison with the specific surface area of graphene flake. [ABSTRACT FROM AUTHOR]

The effect of the size of nickel nanoparticles on the fabrication of a Ni–graphene composite by hydrostatic pressure at 0 K followed by annealing at 1000 and 2000 K is studied by molecular dynamics simulation. Crumpled graphene, consisting of crumpled graphene flakes interconnected by van der Waals forces is chosen as the matrix for the composite and filled with nickel nanoparticles composed of 21 and 47 atoms. It is found that the main factors that affect composite fabrication are nanoparticle size, the orientation of the structural units, and temperature of the fabrication process. The best stress–strain behavior is achieved for the Ni/graphene composite with Ni47 nanoparticle after annealing at 2000 K. However, all of the composites obtained had strength property anisotropy due to the inhomogeneous distribution of pores in the material volume.

Understanding the structural behavior of graphene flake, which is the structural unit of bulk crumpled graphene, is of high importance, especially when it is in contact with the other types of atoms. In the present work, crumpled graphene is considered as storage media for two types of nanoclusters—nickel and hydrogen. Crumpled graphene consists of crumpled graphene flakes bonded by weak van der Waals forces and can be considered an excellent container for different atoms. Molecular dynamics simulation is used to study the behavior of the graphene flake filled with the nickel nanocluster or hydrogen molecules. The simulation results reveal that graphene flake can be considered a perfect container for metal nanocluster since graphene can easily cover it. Hydrogen molecules can be stored on graphene flake at 77 K, however, the amount of hydrogen is low. Thus, additional treatment is required to increase the amount of stored hydrogen. Remarkably, the size dependence of the structural behavior of the graphene flake filled with both nickel and hydrogen atoms is found. The size of the filling cluster should be chosen in comparison with the specific surface area of graphene flake.