Crumpling Defective Graphene Sheets

Upon crumpling, graphene sheets yield intriguing hierarchical structures with high resistance to compression and aggregation, garnering a great deal of attention in recent years for their remarkable potential in a variety of applications. Here, we aim to understand the effect of Stone-Wales (SW) defects, i.e., a typical topological defect of graphene, on the crumpling behavior of graphene sheets at a fundamental level. By employing atomistically informed coarse-grained molecular dynamics (CG-MD) simulations, we find that SW defects strongly influence the sheet conformation as manifested by the change in size scaling laws and weaken the self-adhesion of the sheet during the crumpling process. Remarkably, the analyses of the internal structures (i.e., local curvatures, stresses, and cross-section patterns) of crumpled graphene emphasize the enhanced mechanical heterogeneity and "glass-like" amorphous state elicited by SW defects. Our findings pave the way for understanding and exploring the tailored design of crumpled structure via defect engineering.

Methodology for Molecular Dynamics Simulation of Plastic Deformation of a Nickel/Graphene Composite

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.

Interfacial Bonding Energy on the Interface between ZChSnSb/Sn Alloy Layer and Steel Body at Microscale

To investigate the performance of bonding on the interface between ZChSnSb/Sn and steel body, the interfacial bonding energy on the interface of a ZChSnSb/Sn alloy layer and the steel body with or without Sn as an intermediate layer was calculated under the same loadcase using the molecular dynamics simulation software Materials Studio by ACCELRYS, and the interfacial bonding energy under different Babbitt thicknesses was compared. The results show that the bonding energy of the interface with Sn as an intermediate layer is 10% larger than that of the interface without a Sn layer. The interfacial bonding performances of Babbitt and the steel body with Sn as an intermediate layer are better than those of an interface without a Sn layer. When the thickness of the Babbitt layer of bushing is 17.143 Å, the interfacial bonding energy reaches the maximum, and the interfacial bonding performance is optimum. These findings illustrate the bonding mechanism of the interfacial structure from the molecular level so as to ensure the good bonding properties of the interface, which provides a reference for the improvement of the bush manufacturing process from the microscopic point of view.

Cholesterol Extraction from Cell Membrane by Graphene Nanosheets: A Computational Study

The health risk associated with high cholesterol levels in the human body has motivated intensive efforts to lower them by using specialized drugs. However, little research has been reported on utilizing nanomaterials to extract extra cholesterol from living tissues. Graphene possesses great potential for cholesterol extraction from cell membranes due to its distinct porous structure and outstanding surface adhesion. Here we employ dissipative dynamic simulations to explore pathways for cholesterol extraction from a cell membrane by a sheet of graphene using a coarse-grained graphene nanosheets (CGGN) model. We first demonstrate that the self-assembly process among a single layer of graphene and a group of randomly distributed cholesterol molecules in the aqueous environment, which provides a firm foundation for graphene-cholesterol interactions and the dynamic cholesterol extraction process from the cell membrane. Simulations results show that graphene is capable of removing cholesterol molecules from the bilayer membrane. The interaction between graphene and cholesterol molecules plays an important role in determining the amount of extracted cholesterol molecules from the cell membrane. Our findings open up a promising avenue to exploit the capability of graphene for biomedical applications.

Use of morphological features of carbonaceous materials for improved mechanical properties of epoxy nanocomposites

The mechanical properties of epoxy nanocomposites can be significantly altered by tailoring the morphological features of carbonaceous fillers.