scholarly journals Molecular-Dynamics Study on the Impact Energy Release Characteristics of Fe–Al Energetic Jets

Materials ◽  
2021 ◽  
Vol 14 (18) ◽  
pp. 5249
Author(s):  
Qiang Li ◽  
Chunlan Jiang ◽  
Ye Du
Keyword(s):  
Molecular Dynamics ◽  
Impact Strength ◽  
Energy Release ◽  
Impact Loading ◽  
Molecular Model ◽  
Energetic Material ◽  
Test System ◽  
Dynamics Simulation ◽  
Reaction Products ◽  
The Impact

Fe–Al energetic material releases a large amount of energy under impact loading; therefore, it can replace traditional materials and be used in new weapons. This paper introduces the macroscopic experiment and microscopic molecular-dynamics simulation research on the energy release characteristics of Fe–Al energetic jets under impact loading. A macroscopic dynamic energy acquisition test system was established to quantitatively obtain the composition of Fe–Al energetic jet reaction products. A momentum mirror impacting the Fe–Al particle molecular model was established and the microstructure evolution and impact thermodynamic response of Fe–Al particles under impact loading were analyzed. The mechanism of multi-scale shock-induced chemical reaction of Fe–Al energetic jets is discussed. The results show that the difference in velocity between Fe and Al atoms at the shock wave fronts is the cause of the shock-induced reaction; when the impact strength is low, the Al particles are disordered and amorphous, while the Fe particles remain in their original state and only the oxidation reaction of Al and a small amount intermetallic compound reaction occur. With the increase of impact strength, Al particles and Fe particles are completely disordered and amorphized in a high-temperature and high-pressure environment, fully mixed and penetrated. The temperature of the system rises rapidly, due to a violent thermite reaction, and the energy released by the jet shows an increasing trend; there is an impact intensity threshold, so that the jet release energy reaches the upper limit.

scholarly journals The Impact of the Electric Field on Surface Condensation of Water Vapor: Insight from Molecular Dynamics Simulation

Nanomaterials ◽  
2019 ◽  
Vol 9 (1) ◽  
pp. 64 ◽  
Author(s):  
Qin Wang ◽  
Hui Xie ◽  
Zhiming Hu ◽  
Chao Liu
Keyword(s):  
Molecular Dynamics ◽  
Water Vapor ◽  
Electric Field ◽  
Intermolecular Forces ◽  
Dynamics Simulation ◽  
Water Molecules ◽  
Attraction Force ◽  
Condensation Rate ◽  
Shape Transformation ◽  
The Impact

In this study, molecular dynamics simulations were carried out to study the coupling effect of electric field strength and surface wettability on the condensation process of water vapor. Our results show that an electric field can rotate water molecules upward and restrict condensation. Formed clusters are stretched to become columns above the threshold strength of the field, causing the condensation rate to drop quickly. The enhancement of surface attraction force boosts the rearrangement of water molecules adjacent to the surface and exaggerates the threshold value for shape transformation. In addition, the contact area between clusters and the surface increases with increasing amounts of surface attraction force, which raises the condensation efficiency. Thus, the condensation rate of water vapor on a surface under an electric field is determined by competition between intermolecular forces from the electric field and the surface.

scholarly journals Molecular Dynamics Study on the Mechanism of Nanoscale Jet Instability Reaching Supercritical Conditions

2018 ◽  
Vol 8 (10) ◽  
pp. 1714 ◽  
Author(s):  
Qingfei Fu ◽  
Yunxiao Zhang ◽  
Chaojie Mo ◽  
Lijun Yang
Keyword(s):  
Molecular Dynamics ◽  
Growth Rate ◽  
Theoretical Result ◽  
Molecular Model ◽  
Simulation Method ◽  
Dynamics Simulation ◽  
Jet Instability ◽  
Subcritical Region ◽  
Thermodynamic Conditions ◽  
Spatio Temporal

This paper investigates the characteristics of a nitrogen jet (the thermodynamic conditions ranging from subcritical to supercritical) ejected into a supercritical nitrogen environment using the molecular dynamics (MD) simulation method. The thermodynamic properties of nitrogen obtained by molecular dynamics show good agreement with the Soave-Redlich-Kwong (SRK) equation of state (EOS). The agreement provides validation for this nitrogen molecular model. The molecular dynamics simulation of homogeneous nitrogen spray is carried out in different thermodynamic conditions from subcritical to supercritical, and a spatio-temporal evolution of the nitrogen spray is obtained. The interface of the nitrogen spray is determined at the point where the concentration of ejected fluid component reaches 50%, since the supercritical jet has no obvious vapor-liquid interface. A stability analysis of the transcritical jets shows that the disturbance growth rate of the shear layer coincides very well with the classical theoretical result at subcritical region. In the supercritical region, however, the growth rate obtained by molecular dynamics deviates from the theoretical result.

Molecular Dynamics Studies on the Growth and Structural Properties of Hydrogenated DLC Films

2008 ◽  
Vol 373-374 ◽  
pp. 108-112
Author(s):  
Yu Jun Zhang ◽  
Guang Neng Dong ◽  
Jun Hong Mao ◽  
You Bai Xie
Keyword(s):  
Molecular Dynamics ◽  
Structural Properties ◽  
Impact Energy ◽  
Frictional Coefficient ◽  
Carbon Films ◽  
Dynamics Simulation ◽  
Diamond Surface ◽  
Hydrogen Atoms ◽  
Molecular Configuration ◽  
The Impact

The novel frictional properties of hydrogenated DLC (Diamond-like Carbon) films have been reported for nearly ten years. But up to now, researchers still haven’t known the exact mechanism resulting in the super-low frictional performance of hydrogenated DLC films. Especially they have little knowledge on the molecular configuration and structural properties of these kinds of films. In this paper, CH3 radicals with different impact energies are selected as source species to deposit DLC films on diamond (100) by molecular dynamics simulation. Results show hydrogenated DLC films can be successfully obtained when impact energy is in an appropriate scope that is no less than 20eV. The depositing processes involve impinging diamond surface and bonding procedure. Some atoms, instead of bonding with substrate atoms, fly away from the diamond surface. Only suitable impact energy can improve the growth of the film. Within 30eV to 60eV, the maximum deposition ratio is attained. In addition, when carbon atoms act as the deposition sources, the deposition ratio is relatively higher. Furthermore, the authors find that species with higher concentration of carbon atoms in deposition sources lead to a better deposition rate. Carbon atoms are more reactive than hydrogen atoms. Then the relative densities of DLC films are calculated. The density curves indicate that the structures of the films vary obviously as the impact energy augments. The average relative density is generally monotone increase with the increment of impact energy. The hybridization of carbon atoms greatly affects the properties of hydrogenated DLC films. The transition between sp2 and sp3 will result in the graphitization and reduce the frictional coefficient when DLC films are used as tribo-pair in friction.

scholarly journals Material Analysis and Molecular Dynamics Simulation for Cavitation Erosion and Corrosion Suppression in Water Hydraulic Valves

Materials ◽  
2020 ◽  
Vol 13 (2) ◽  
pp. 453 ◽  
Author(s):  
Masoud Kamoleka Mlela ◽  
He Xu ◽  
Feng Sun ◽  
Haihang Wang ◽  
Gabriel Donald Madenge
Keyword(s):  
Molecular Dynamics ◽  
Md Simulation ◽  
Essential Role ◽  
Corrosion Inhibitors ◽  
Cavitation Erosion ◽  
Dynamics Simulation ◽  
Preference Ranking ◽  
Water Hydraulics ◽  
The Impact ◽  
Hydraulic Valves

In the milestone of straggling to make water hydraulics more advantageous, the choice of coating polymer for water hydraulics valves plays an essential role in alleviating the impact of cavitation erosion and corrosion, and this is a critical task for designers. Fulfilling the appropriate selection, we conflicted properties that are vital for erosion and corrosion inhibitors, as well as the tribology in the sense of coefficient of friction. This article aimed to choose the best alternative polymer for coating on the selected substrate, that is, Cr2O3, Al2O3, Ti2O3. By applying PROMETHEE (Preference Ranking Organization Method for Enrichment Evaluations), the best polymer obtained with an analyzed performance attribute is Polytetrafluoroethylene (PTFE) that comes up with higher outranking (0.5932052). A Molecular Dynamics (MD) simulation was conducted to identify the stronger bonding with the regards of the better cleave plane between Polytetrafluoroethylene (PTFE) and the selected substrate. Polytetrafluoroethylene (PTFE)/Al2O3 cleaved in (010) plane was observed to be the strongest bond in terms of binding energy (3188 kJ/mol) suitable for further studies.

Molecular Dynamics Simulations of Structures of Amorphous Carbon Films via Deposition

2011 ◽  
Vol 194-196 ◽  
pp. 2220-2224
Author(s):  
Hui Qing Lan ◽  
Zheng Ling Kang
Keyword(s):  
Molecular Dynamics ◽  
Amorphous Carbon ◽  
Growth Dynamics ◽  
Carbon Films ◽  
Film Structure ◽  
Dynamics Simulation ◽  
Carbon Ions ◽  
Amorphous Carbon Films ◽  
Dynamics Simulations ◽  
The Impact

The growth of amorphous carbon films via deposition is investigated using molecular dynamics simulation with a modified Tersoff potential. The impact energy of carbon atoms ranges from 1 to 50 eV and the temperature of the diamond substrate is 300 K. The effects of the incident energy on the growth dynamics and film structure are studied in a detail. Simulation results show that the mobility of surface atoms in the cascade region is enhanced by impacting energetic carbon ions, especially at moderate energy, which favors the growth of denser and smoother films with better adhesion to the substrate. Our results agree qualitatively with the experimental observation.

Comparison of the effect of poly(N-vinyl caprolactam) and poly(N-isopropyl acrylamide) trimers on the stability of hydrated Na-montmorillonite: A molecular dynamics study

2020 ◽  
pp. 096739112093524
Author(s):  
Jiafang Xu ◽  
Moussa Camara ◽  
Hualin Liao ◽  
Hong Guo ◽  
Kouassi Louis Kra ◽  
...  
Keyword(s):  
Molecular Dynamics ◽  
Conformational Changes ◽  
Stable State ◽  
Dynamics Simulation ◽  
Effect Of Temperature ◽  
Radius Of Gyration ◽  
Molecular Arrangement ◽  
Isopropyl Acrylamide ◽  
The Stability ◽  
The Impact

In the present study, we performed a molecular dynamics simulation of the intercalation of poly( N-isopropyl acrylamide) (NIPAM)3 and poly( N-vinyl caprolactam) (NVCL)3 trimers into Na-montmorillonite (Na-Mt) to evaluate their effects on the interlayer structure and the stability of hydrated Na-Mt. The impact of both trimers on the interlayer species and their dynamics properties at different temperatures in a canonical ensemble (NVT) were investigated. The results showed that the electrostatic forces exerted by Na cations on H2O molecules and the interlayer H2O molecular arrangement are not affected by the rise in temperature after adding both trimers. Trimer addition reinforced the structure of interlayer H2O molecules so that the effect of temperature increase on them became negligible. The structural dynamics evolution of the radius of gyration of both trimers showed the existence of conformation changes when temperature increased. These conformational changes are more complex in the case of (NVCL)3 than (NIPAM)3 due to its large monomers. Both trimers reduced the mobility of interlayer particles with a better inhibition effect obtained for (NVCL)3 compared to (NIPAM)3. The concentration profile of interlayers’ species showed the affinity of Na cations for clay mineral surfaces while H2O molecules moved away. Compared these two trimers, the most stable state of Na-Mt is achieved with (NVCL)3. These results could help highlight the inhibition properties of (NIPAM)3 and (NVCL)3 on hydrated Na-Mt and to predict its stability against changes in environmental conditions.

scholarly journals Experimental Study on the Energy-Release Characteristics of Fine-Grained Fe/Al Energetic Jets under Impact Loading

Materials ◽  
2019 ◽  
Vol 12 (20) ◽  
pp. 3317
Author(s):  
Li ◽  
Du
Keyword(s):  
Experimental Data ◽  
Energy Release ◽  
Impact Energy ◽  
Impact Loading ◽  
Energetic Materials ◽  
Chemical Properties ◽  
Microscopic Analysis ◽  
Specific Content ◽  
Fine Grained ◽  
The Impact

The energy released by the active metal phase in fine-grained Fe/Al energetic materials enables the replacement of conventional materials in new types of weapons. This paper describes an experiment designed to study the energy-release characteristics of fine-grained Fe/Al energetic jets under impact loading. By means of dynamic mechanical properties analysis, the physical and chemical properties of Fe/Al energetic materials with specific content are studied, and the preparation process is determined. The energy-release properties of fine-grained Fe/Al jets subject to different impact conditions are studied based on experimental data, and energy-release differences are discussed. The results show that for fine-grained Fe/Al energetic materials to remain active and exhibit high strength, the highest sintering temperature is 550 °C. With increasing impact energy, the energy release of fine-grained Fe/Al energetic jets increases. At an impact-energy threshold of 121.1 J/mm2, the chemical reaction of the fine-grained Fe/Al energetic jets is saturated. The experimental data and microscopic analysis show that when the impact energy reaches the threshold, the energy efficiency ratio of Fe/Al energetic jets can reach 95.3%.

Nano-Indentation Simulation Study Based on Parallel Computing

2012 ◽  
Vol 500 ◽  
pp. 696-701
Author(s):  
Ying Zhu ◽  
Sen Song ◽  
Ling Ling Xie ◽  
Shun He Qi ◽  
Qian Qian Liu
Keyword(s):  
Molecular Dynamics ◽  
Parallel Computing ◽  
Molecular Dynamics Simulation ◽  
Large Scale ◽  
Dynamics Simulation ◽  
Parallel Computer ◽  
Nano Indentation ◽  
Simulation Results ◽  
The Impact ◽  
Simulation Time

This method of parallel computing into nanoindentation molecular dynamics simulation (MDS), the author uses a nine-node parallel computer and takes the single crystal aluminum as the experimental example, to implement the large-scale process simulation of nanoindentation. Compared the simulation results with experimental results is to verify the reliability of the simulation. The method improves the computational efficiency and shortens the simulation time and the expansion of scale simulation can significantly reduce the impact of boundary conditions, effectively improve the accuracy of the molecular dynamics simulation of nanoindentation.

Antibacterial Effect of Silver Nanomaterials on Staphylococcal Protein A by Molecular Dynamics Simulation

2020 ◽  
Vol 20 (8) ◽  
pp. 4914-4919
Author(s):  
Weiming Sun ◽  
Xiangli Dong ◽  
Guohua Yu ◽  
Lang Shuai
Keyword(s):  
Molecular Dynamics ◽  
Antimicrobial Activity ◽  
Protein A ◽  
Protein Secondary Structure ◽  
Oral Bacteria ◽  
Dynamics Simulation ◽  
Solvent Accessible Surface Area ◽  
Staphylococcal Protein A ◽  
Staphylococcal Protein ◽  
The Impact

Nanotechnologies have changed this world in various aspects including the oral medicine. It has been demonstrated that silver (Ag) nanomaterials can exhibit strong inhibition and killing effect on oral bacteria. Furthermore, the Ag nanomaterials have superb antimicrobial activity and nonacute toxic effects on human cells. Previously, the impact of Ag on oral bacteria was demonstrated by experiments. In this work, we applied molecular dynamics (MD) simulations to investigate the influence of Ag nanomaterials on oral bacteria. Firstly, by comparing change of molecular structure of staphylococcal protein A (SPA) with and without Ag, we found that Ag nanomaterials have strong effect on evolution of protein secondary structure of SPA. Secondly, it was observed that Ag has negligible effect on Solvent Accessible Surface Area (SASA) of SPA indicating that the Ag only changed its microstructure. Finally, it was found that the average amount of hydrogen bond in SPA was reduced in the presence of Ag which was origin of antimicrobial activity of Ag. It is believed that the growing interest in dental medicine with nanomaterials would lead molecular dynamics simulations to be an effective method for studying inhibition and killing pathological process of nanomaterials on oral bacteria.

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