scholarly journals Molecular Dynamics Calculation on the Adhesive Interaction Between the Polytetrafluoroethylene Transfer Film and Iron Surface

2021 ◽  
Vol 9 ◽  
Author(s):  
Zhen Zuo ◽  
Lifen Liang ◽  
Qianqian Bao ◽  
Pengtao Yan ◽  
Xin Jin ◽  
...  
Keyword(s):  
Molecular Dynamics ◽  
Interaction Energy ◽  
Mean Square Displacement ◽  
Transfer Film ◽  
Polymer Chains ◽  
Iron Surface ◽  
Energy Concentration ◽  
Adhesive Interaction ◽  
Dynamics Calculation ◽  
Dynamics Simulations

During the friction process, the polytetrafluoroethylene (PTFE) adhered on the counterpart surface was known as the PTFE transfer film, which was fundamental to the lubricating performance of the PTFE. However, the adhesive interaction between the iron surface and the adhered PTFE transfer film is still unclear. In present study, molecular dynamics simulations were used to reveal the adhesive interaction between the iron surface and PTFE transfer film. Based on the atomic trajectories obtained through the molecular dynamics, the interaction energy, concentration profile, radial distribution function, and mean square displacement were calculated to analyze the structure of the interface. The negative values of the interaction energy demonstrated the adhesive interaction between the PTFE transfer film and Fe surfaces, resulting in the accumulation of the PTFE transfer film on the Fe surface. Among the (100) (110), and (111) surfaces of α-Fe (110) surface owns the strongest adhesive interaction with the PTFE transfer film. Compared with the original PTFE molecule, the chain broken PTFE, hydroxyl substituted PTFE, and carbonyl substituted PTFE exhibited stronger adhesive interaction with Fe surface. The adhesive interaction between the PTFE transfer film and Fe surfaces was mainly originated from the Fe atoms and the F atoms of the adsorbate PTFE transfer film, which was governed by the van der Waals force. The bonding distance between the Fe atom and the F atom of the adsorbate PTFE transfer film is around 2.8 Å. Moreover, the chain broken of PTFE molecule and the rise of temperature can remarkably increase the mobility of polymer chains in the interface system.

scholarly journals Interface Characteristics of Neat Melts and Binary Mixtures of Polyethylenes from Atomistic Molecular Dynamics Simulations

Polymers ◽  
2020 ◽  
Vol 12 (5) ◽  
pp. 1059
Author(s):  
Sanghun Lee ◽  
Curtis W. Frank ◽  
Do Y. Yoon
Keyword(s):  
Molecular Dynamics ◽  
Surface Tension ◽  
Molecular Dynamics Simulations ◽  
Binary Mixtures ◽  
Surface Segregation ◽  
Surface Region ◽  
Polymer Chains ◽  
Methyl Groups ◽  
Free Standing ◽  
Dynamics Simulations

Molecular dynamics simulations of free-standing thin films of neat melts of polyethylene (PE) chains up to C150H302 and their binary mixtures with n-C13H28 are performed employing a united atom model. We estimate the surface tension values of PE melts from the atomic virial tensor over a range of temperatures, which are in good agreement with experimental results. Compared with short n-alkane systems, there is an enhanced surface segregation of methyl chain ends in longer PE chains. Moreover, the methyl groups become more segregated in the surface region with decreasing temperature, leading to the conclusion that the surface-segregation of methyl chain ends mainly arises from the enthalpic origin attributed to the lower cohesive energy density of terminal methyl groups. In the mixtures of two different chain lengths, the shorter chains are more likely to be found in the surface region, and this molecular segregation in moderately asymmetric mixtures in the chain length (C13H28 + C44H90) is dominated by the enthalpic effect of methyl chain ends. Such molecular segregation is further enhanced and dominated by the entropic effect of conformational constraints in the surface for the highly asymmetric mixtures containing long polymer chains (C13H28 + C150H3020). The estimated surface tension values of the mixtures are consistent with the observed molecular segregation characteristics. Despite this molecular segregation, the normalized density of methyl chain ends of the longer chain is more strongly enhanced, as compared with the all-segment density of the longer chain itself, in the surface region of melt mixtures. In addition, the molecular segregation results in higher order parameter of the shorter-chain segments at the surface and deeper persistence of surface-induced segmental order into the film for the longer chains, as compared with those in neat melt films.

Molecular dynamics simulation of aggregation of monocrystal and polycrystal copper nanoparticles

2019 ◽  
Vol 33 (16) ◽  
pp. 1950168
Author(s):  
Linxing Zhang ◽  
Guang Hong ◽  
Shouyin Cai
Keyword(s):  
Molecular Dynamics ◽  
Lattice Structure ◽  
Displacement Vector ◽  
Mean Square Displacement ◽  
Dynamics Simulation ◽  
Gyration Radius ◽  
Mean Square ◽  
Shrinkage Ratio ◽  
Lower Temperature ◽  
Dynamics Simulations

Molecular dynamics simulations were employed to investigate the aggregation of monocrystal and polycrystal nanoparticles. The lattice structure, displacement vector, potential energy, shrinkage ratio, relative gyration radius and mean square displacement of the two systems are compared. The results indicate that the aggregation of polycrystal nanoparticles is more drastic than that of monocrystal nanoparticles. Besides, the polycrystal nanoparticles are found contacted and melted at lower-temperature than that of monocrystal nanoparticles. The reason for all these phenomena is that there is additional surface energy in the grain boundary of polycrystal nanoparticles.

Computational Investigation of Interfacial Cracks Changes of TiAl Alloy

2017 ◽  
Vol 727 ◽  
pp. 93-97
Author(s):  
Gen Zong Song ◽  
Lin Zhang
Keyword(s):  
Molecular Dynamics ◽  
Tial Alloy ◽  
Average Energy ◽  
Causative Factor ◽  
Heating Process ◽  
Experimental Conditions ◽  
Embedded Atom ◽  
Interfacial Cracks ◽  
Dynamics Calculation ◽  
Dynamics Simulations

In an effort to develop into a practical application of TiAl alloys for aerospace materials, Researchers at home and abroad in the use of alloying and thermal processing methods to improve the brittleness and other areas a lot of work.The existence of cracks which led to the kinds of material degradation of the major causative factor. However, it is difficult for us to observed the change of the local atom structure of the material by experiments in the limitation from our experimental conditions, nevertheless, computational research provide us the possibility that we can observe the evolution of the structure. Molecular dynamics calculation is considered to be well suited to describe the change of potential energy of the atoms in such a system. Embedded atom method (EAM) and canonical ensemble (NVT) molecular dynamics simulations have been carried out to obtain pre-cracks of different lengths of the structure of TiAl alloy. According to the average energy of atoms and the radial density distribution function, with increasing temperature the changes, analysis of TiAl alloy films of micro-cracks in the heating process, the structure changes with temperature.

Molecular insight into the Mullins effect: irreversible disentanglement of polymer chains revealed by molecular dynamics simulations

2017 ◽  
Vol 19 (29) ◽  
pp. 19468-19477 ◽  
Author(s):  
Chi Ma ◽  
Tuo Ji ◽  
Christopher G. Robertson ◽  
R. Rajeshbabu ◽  
Jiahua Zhu ◽  
...  
Keyword(s):  
Molecular Dynamics ◽  
Molecular Dynamics Simulations ◽  
Molecular Model ◽  
Polymer Chains ◽  
Mullins Effect ◽  
Key Characteristics ◽  
Dynamics Simulations ◽  
First Time ◽  
Insight Into

For the first time, the key characteristics associated with the Mullins effect are captured by a molecular model.

Simulation study on the subdiffusion of polymer chains in crowded environments containing nanoparticles

2021 ◽  
Author(s):  
Rong-Xing Lu ◽  
Jian-Hua Huang ◽  
Meng-Bo Luo
Keyword(s):  
Molecular Dynamics ◽  
Molecular Dynamics Simulations ◽  
Simulation Study ◽  
Polymer Chains ◽  
Dynamics Simulations ◽  
Crowded Environments

Polymer chains in crowded environments often show subdiffusive behavior. We adopt molecular dynamics simulations to study the conditions for the subdiffusion of polymer chains in crowded environments containing randomly distributed,...

Molecular Dynamics Simulations of Polypropylene and Talcum Nanocomposite

2012 ◽  
Vol 466-467 ◽  
pp. 161-164
Author(s):  
Na Song ◽  
Qing Wang ◽  
Xiao Ji Zhang ◽  
Peng Ding
Keyword(s):  
Molecular Dynamics ◽  
Molecular Modeling ◽  
Binding Energy ◽  
Potential Energy ◽  
Total Energy ◽  
Polymer Chains ◽  
Nanocomposite System ◽  
Modeling Techniques ◽  
Dynamics Simulations ◽  
Simulation Time

Molecular modeling techniques were applied to predicting binding energy for PP/talc and PP-MAH/talc. A supercell containing talc and two polymer chains of 25 repeating units length was constructed. The COMPASS forcefield has been used to represent the interactions in the nanocomposite system. The interactions are improved between the polymer and the clay in the presence of functional groups. And the total energy and potential energy between PP and the talc decreases almost linearly with the simulation time.

Nonbond interactions between graphene nanosheets and polymers: a computational study

e-Polymers ◽  
2014 ◽  
Vol 14 (3) ◽  
pp. 169-176 ◽  
Author(s):  
Yong-Fang Mo ◽  
Chuan-Lu Yang ◽  
Yan-Fei Xing ◽  
Mei-Shan Wang ◽  
Xiao-Guang Ma
Keyword(s):  
Molecular Dynamics ◽  
Electrostatic Interaction ◽  
Computational Study ◽  
Graphene Nanosheets ◽  
Polymer Chains ◽  
Flexible Polymers ◽  
Graphene Nanosheet ◽  
Dynamics Simulations ◽  
Nonbond Interactions ◽  
Vdw Interaction

AbstractBased on the geometries from molecular dynamics simulations and a package compiled by us, the interactions between graphene nanosheet (GNS) and nine types of flexible polymers have been investigated with force field. Both the van der Waals (vdW) interaction and the electrostatic interaction (EI) for two same polymer chains and between a polymer and a GNS were calculated and compared. The effect of cut-off distance was explored. It was found that the cut-off distance plays a significant role in EI energy, but a less important role in vdW energy when the cut-off distance is over 9.5 Å. The reasonable cut-off distances for EI and vdW interactions for simulation are suggested.

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