The behaviour of Boron Carbide under shock compression conditions: MD simulation results

2022 ◽  
Vol 201 ◽  
pp. 110872
Author(s):  
Hüseyin C. Çekil ◽  
Metin Özdemir
Keyword(s):  
Boron Carbide ◽  
Shock Compression ◽  
Md Simulation ◽  
Simulation Results

Thermal Transport in Nanocrystalline Materials

2005 ◽  
Author(s):  
Zhanrong Zhong ◽  
Xinwei Wang
Keyword(s):  
Thermal Conductivity ◽  
Specific Heat ◽  
Thermal Transport ◽  
Nanocrystalline Materials ◽  
Large Scale ◽  
Md Simulation ◽  
Fundamental Physics ◽  
Grain Sizes ◽  
Simulation Results ◽  
Thermal Phenomena

In this work, thermal transport in nanocrystalline materials is studied using large-scale equilibrium molecular dynamics (MD) simulation. Nanocrystalline materials with different grain sizes are studied to explore how and to what extent the size of nanograins affects the thermal conductivity and specific heat. Substantial thermal conductivity reduction is observed and the reduction is stronger for nanocrystalline materials with smaller grains. On the other hand, the specific heat of nanocrystalline materials shows little change with the grain size. The simulation results are compared with the thermal transport in individual nanograins based on MD simulation. Further discussions are provided to explain the fundamental physics behind the observed thermal phenomena in this work.

Thermal Expansion and Isotopic Composition Effects on Lattice Thermal Conductivities of Crystalline Silicon

2006 ◽  
Author(s):  
Yunfei Chen ◽  
Guodong Wang ◽  
Deyu Li ◽  
Jennifer R. Lukes
Keyword(s):  
Thermal Conductivity ◽  
Thermal Expansion ◽  
Md Simulation ◽  
Lattice Thermal Conductivity ◽  
Mass Difference ◽  
Dynamics Simulation ◽  
Temperature Range ◽  
Simulation Results ◽  
Callaway Model ◽  
Thermal Conductivities

Equilibrium molecular dynamics simulation is used to calculate lattice thermal conductivities of crystal silicon in the temperature range from 400K to 1600K. Simulation results confirmed that thermal expansion, which resulted in the increase of the lattice parameter, caused the decrease of the lattice thermal conductivity. The simulated results proved that thermal expansion imposed another type resistance on phonon transport in crystal materials. Isotopic and vacancy effects on lattice thermal conductivity are also investigated and compared with the prediction from the modified Debye Callaway model. It is demonstrated in the MD simulation results that the isotopic effect on lattice thermal conductivity is little in the temperature range from 400K to 1600K for isotopic concentration below 1%, which implies the isotopic scattering on phonon due to mass difference can be neglected over the room temperature. The remove of atoms from the crystal matrix caused mass difference and elastic strain between the void and the neighbor atoms, which resulted in vacancy scattering on phonons. Simulation results demonstrated this mechanism is stronger than that caused by isotopic scattering on phonons due to mass difference. A good agreement is obtained between the MD simulation results of silicon crystal with vacancy defects and the data predicted from the modified Debye Callaway model. This conclusion is helpful to demonstrate the validity of Klemens' Rayleigh model for impurity scattering on phonons.

Shock compression behaviors of boron carbide (B[sub 4]C)

2006 ◽  
Vol 100 (11) ◽  
pp. 113536 ◽  
Author(s):  
Y. Zhang ◽  
T. Mashimo ◽  
Y. Uemura ◽  
M. Uchino ◽  
M. Kodama ◽  
...  
Keyword(s):  
Boron Carbide ◽  
Shock Compression

A scale-up nanoporous membrane centrifuge for reverse osmosis desalination without fouling

TECHNOLOGY ◽  
2018 ◽  
Vol 06 (01) ◽  
pp. 36-48 ◽  
Author(s):  
Qingsong Tu ◽  
Tiange Li ◽  
Ao Deng ◽  
Kevin Zhu ◽  
Yifei Liu ◽  
...  
Keyword(s):  
Angular Velocity ◽  
Reverse Osmosis ◽  
Large Scale ◽  
Md Simulation ◽  
Scale Up ◽  
Scale Separation ◽  
Nanoporous Membrane ◽  
Micron Size ◽  
Simulation Results ◽  
Reverse Osmosis Desalination

A scale-up nanoporous membrane centrifuge is designed and modeled. It can be used for nanoscale scale separation including reverse osmosis desalination. There are micron-size pores on the wall of the centrifuge and nanoscale pores on local graphene membrane patches that cover the micron-size pores. In this work, we derived the critical angular velocity required to counter-balance osmosis force, so that the reverse-osmosis (RO) desalination process can proceed. To validate this result, we conducted a large scale (four million atoms) full atom molecular dynamics (MD) simulation to examine the critical angular velocity required for reverse osmosis at nanoscale. It is shown that the analytical results derived based on fluid mechanics and the simulation results observed in MD simulation are consistent and well matched. The main advantage of such nanomaterial based centrifuge is its intrinsic anti-fouling ability to clear [Formula: see text] and [Formula: see text] ions accumulated at the vicinity of the pores due to the Coriolis effect. Analyses have been conducted to study the relation between osmotic pressure, centrifugal pressure, and water permeability.

Analysis of the Instability for Two Nano-Scale Liquid Threads Coexisting in a Periodic Fundamental Cell

2011 ◽  
Author(s):  
Chun-Lang Yeh
Keyword(s):  
Stability Criterion ◽  
Md Simulation ◽  
Density Field ◽  
Stability Criteria ◽  
Stable Domain ◽  
Nano Scale ◽  
Critical Wavelength ◽  
Molecular Scale ◽  
Vaporization Process ◽  
Simulation Results

This paper investigates the vaporization process of two nano-scale liquid threads coexisting in a periodic fundamental cell by molecular dynamics (MD) simulation. The influences of liquid thread radius, fundamental cell length, and relative position of the two threads are discussed. Snapshots of molecules, the number of liquid particles formed, and density field are analyzed. Two linear stability criteria, namely, Rayleigh’s stability criterion and Kim’s stability criterion, are accessed for their validity in molecular scale. It is found that more liquid particles are formed when the separation of the two threads is larger. Moreover, vaporization is slower when the two liquid threads are close to each other. It is also found that the trends of Rayleigh’s stability criterion and Kim’s stability criterion agree with MD simulation results. However, when the two threads coalesce into a single thread and remain intact, the critical wavelength of perturbation may be increased and the stable domain is broadened. Under such a situation, Rayleigh’s stability criterion and Kim’s stability criterion underpredict the stable domain.

Multiple Time-Scale Molecular Simulations: Modeling Realistic Loading Rates

2007 ◽  
Author(s):  
S. N. Medyanik ◽  
E. Guleryuz
Keyword(s):  
Time Scales ◽  
Md Simulation ◽  
Multiple Time ◽  
Strain Rates ◽  
Simulation Methods ◽  
Multiple Time Scale ◽  
Loading Rates ◽  
Simulation Results ◽  
Experimental Values

The vast gap between the molecular dynamics (MD) and experimental time scales poses serious problems to direct comparison between the MD simulation and experimental results. The inability of the traditional MD simulation methods to model long enough time scales also results in modeling unrealistically high loading rates and strain rates that are usually at least six or seven orders of magnitude higher than the corresponding experimental values. This may have a tremendous effect on the realism and quality of the simulation results.

scholarly journals Simulation Study of Helium Effect on the Microstructure of Nanocrystalline Body-Centered Cubic Iron

Materials ◽  
2018 ◽  
Vol 12 (1) ◽  
pp. 91 ◽  
Author(s):  
Chunping Xu ◽  
Wenjun Wang
Keyword(s):  
Lattice Constant ◽  
Tensile Strain ◽  
Room Temperature ◽  
Md Simulation ◽  
Uniaxial Tensile ◽  
Body Centered Cubic ◽  
X Ray Diffraction ◽  
X Ray ◽  
Swelling Rate ◽  
Simulation Results

Helium (He) effect on the microstructure of nanocrystalline body-centered cubic iron (BCC-Fe) was studied through Molecular Dynamics (MD) simulation and simulated X-ray Diffraction (XRD). The crack generation and the change of lattice constant were investigated under a uniaxial tensile strain at room temperature to explore the roles of He concentration and distribution played in the degradation of mechanical properties. The simulation results show that the expansion of the lattice constant decreases and the swelling rate increases while the He in the BCC region diffuses into the grain boundary (GB) region. The mechanical property of nanocrystalline BCC-Fe shows He concentration and distribution dependence, and the existence of He in GB is found to benefit the generation and growth of cracks and to affect the strength of GB during loading. It is observed that the reduction of tensile stress contributed by GB He is more obvious than that contributed by grain interior He.

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