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.

scholarly journals Comparative study of thermal transport in Zea mays straw and Zea mays heartwood (cork) boards

2010 ◽  
Vol 14 (1) ◽  
pp. 31-38 ◽  
Author(s):  
Sunday Etuk ◽  
Louis Akpabio ◽  
Ita Akpan
Keyword(s):  
Thermal Conductivity ◽  
Heat Capacity ◽  
Zea Mays ◽  
Thermal Diffusivity ◽  
Comparative Study ◽  
Specific Heat ◽  
Specific Heat Capacity ◽  
Thermal Transport ◽  
Insulation Material ◽  
Thermal Absorptivity

Thermal conductivity values at the temperature of 301-303K have been measured for Zea mays straw board as well as Zea mays heartwood (cork) board. Comparative study of the thermal conductivity values of the boards reveal that Zea mays heartwood board has a lower thermal conductivity value to that of the straw board. The study also shows that the straw board is denser than the heartwood board. Specific heat capacity value is less in value for the heartwood board than the straw board. These parameters also affect the thermal diffusivity as well as thermal absorptivity values for the two types of boards. The result favours the two boards as thermal insulators for thermal envelop but with heartwood board as a preferred insulation material than the straw board.

Monolayer and bilayer polyaniline C3N: two-dimensional semiconductors with high thermal conductivity

Nanoscale ◽  
2018 ◽  
Vol 10 (9) ◽  
pp. 4301-4310 ◽  
Author(s):  
Yang Hong ◽  
Jingchao Zhang ◽  
Xiao Cheng Zeng
Keyword(s):  
Thermal Conductivity ◽  
Thermal Transport ◽  
Md Simulation ◽  
Transport Processes ◽  
High Thermal Conductivity ◽  
Two Dimensional

Lateral and flexural thermal transport processes in monolayer and bilayer C3N are systematically investigated using MD simulation.

Synthesis and Characterization of Nanofluids Useful in Concentrated Solar Power Plants Produced by New Mixing Methodologies for Large-Scale Production

2018 ◽  
Vol 140 (4) ◽  
Author(s):  
Manila Chieruzzi ◽  
Adio Miliozzi ◽  
Tommaso Crescenzi ◽  
José M. Kenny ◽  
Luigi Torre
Keyword(s):  
Thermal Conductivity ◽  
Thermal Properties ◽  
Specific Heat ◽  
Power Plants ◽  
Large Scale ◽  
Alumina Nanoparticles ◽  
Energy Storage Materials ◽  
Scale Production ◽  
Salt Mixture ◽  
Silica Alumina

In this study, different nanofluids (NFs) were developed by mixing a molten salt mixture (60% NaNO3–40% KNO3) with 1.0 wt % of silica–alumina nanoparticles using different methods. These NFs can be used as thermal energy storage materials in concentrating solar plants with a reduction of storage material if the thermal properties of the base fluid are increased. New mixing procedures without sonication were introduced with the aim to avoid the sonication step and to allow the production of a greater amount of NF with a procedure potentially more suitable for large-scale productions. For this purpose, two mechanical mixers and a magnetic stirrer were used. Each NF was prepared in aqueous solution with a concentration of 100 g/l. The effect of different concentrations (300 g/l and 500 g/l) was also studied with the most effective mixer. Specific heat, melting temperature, and latent heat were measured by means of differential scanning calorimeter. Thermal conductivity and diffusivity in the solid state were also evaluated. The results show that the highest increase of the specific heat was obtained with 100 g/l both in solid (up to 31%) and in liquid phase (up to 14%) with the two mechanical mixers. The same NFs also showed higher amount of stored heat. An increase in thermal conductivity and diffusivity was also detected for high solution concentrations with a maximum of 25% and 47%, respectively. Scanning electron microscopy (SEM) and energy-dispersive X-ray analyses revealed that the grain size in the NFs is much smaller than in the salt mixture, especially for the NF showing the highest thermal properties increase, and a better nanoparticles distribution is achieved with the lowest concentration. NFs with enhanced thermal properties can be synthesized in a cost-effective form in high concentrated aqueous solutions by using mechanical mixers.

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.

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.

scholarly journals Molecular Dynamics Simulation-Based Study on Enhancing Thermal Properties of Graphene-Reinforced Thermoplastic Polyurethane Nanocomposite for Heat Exchanger Materials

2020 ◽  
Author(s):  
Animesh Talapatra ◽  
Debasis Datta
Keyword(s):  
Thermal Conductivity ◽  
Molecular Dynamics ◽  
Glass Transition ◽  
Thermal Properties ◽  
Transition Temperature ◽  
Glass Transition Temperature ◽  
Md Simulation ◽  
Thermoplastic Polyurethane ◽  
Simulation Based ◽  
Simulation Results

Molecular dynamics (MD) simulation-based development of heat resistance nanocomposite materials for nanoheat transfer devices (like nanoheat exchanger) and applications have been studied. In this study, MD software (Materials Studio) has been used to know the heat transport behaviors of the graphene-reinforced thermoplastic polyurethane (Gr/TPU) nanocomposite. The effect of graphene weight percentage (wt%) on thermal properties (e.g., glass transition temperature, coefficient of thermal expansion, heat capacity, thermal conductivity, and interface thermal conductance) of Gr/TPU nanocomposites has been studied. Condensed-phase optimized molecular potentials for atomistic simulation studies (COMPASS) force field which is incorporated in both amorphous and forcite plus atomistic simulation modules within the software are used for this present study. Layer models have been developed to characterize thermal properties of the Gr/TPU nanocomposites. It is seen from the simulation results that glass transition temperature (Tg) of the Gr/TPU nanocomposites is higher than that of pure TPU. MD simulation results indicate that addition of graphene into TPU matrix enhances thermal conductivity. The present study provides effective guidance and understanding of the thermal mechanism of graphene/TPU nanocomposites for improving their thermal properties. Finally, the revealed enhanced thermal properties of nanocomposites, the interfacial interaction energy, and the free volume of polymer nanocomposites are examined and discussed.

Anisotropic electrical, thermal and magnetic properties of Al13Ru4 decagonal quasicrystalline approximant

2017 ◽  
Vol 232 (7-9) ◽  
Author(s):  
Magdalena Wencka ◽  
Stanislav Vrtnik ◽  
Primož Koželj ◽  
Zvonko Jagličić ◽  
Peter Gille ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Magnetic Properties ◽  
Electrical Resistivity ◽  
Specific Heat ◽  
Thermoelectric Power ◽  
Thermal Transport ◽  
Transport Coefficients

AbstractWe present measurements of the anisotropic electrical and thermal transport coefficients (the electrical resistivity, the thermoelectric power, the thermal conductivity), the magnetization and the specific heat of the Al

scholarly journals Thermal Transport in Polymers: A Review

2021 ◽  
Author(s):  
Xingfei Wei ◽  
Zhi Wang ◽  
Zhiting Tian ◽  
Tengfei Luo
Keyword(s):  
Thermal Conductivity ◽  
Structural Property ◽  
Thermal Transport ◽  
Large Scale ◽  
Applied Research ◽  
Amorphous Polymers ◽  
High Thermal Conductivity ◽  
Molecular Alignments ◽  
Amorphous States ◽  
Engineering Polymers

Abstract In this article, we review thermal transport in polymers with different morphologies from aligned fibers to bulk amorphous states. We survey early and recent efforts in engineering polymers with high thermal conductivity by fabricating polymers with large-scale molecular alignments. The experimentally realized extremely high thermal conductivity of polymer nanofibers are highlighted, and understanding of thermal transport physics from molecular simulations are discussed. We then transition to the discussion of bulk amorphous polymers with an emphasize on the physics of thermal transport and its relation with the conformation of molecular chains in polymers. We also discuss the current understanding of how the chemistry of polymers would influence thermal transport in amorphous polymers and some limited, but important chemistry-structural-property relationships. Lastly, challenges, perspectives and outlook of this field are presented. We hope this review will inspire more fundamental and applied research in the polymer thermal transport field to advance scientific understanding and engineering applications.

scholarly journals Rapid Prediction of Anisotropic Lattice Thermal Conductivity: Application to Layered Materials

2018 ◽  
Author(s):  
Robert McKinney ◽  
Prashun Gorai ◽  
Eric S. Toberer ◽  
Vladan Stevanovic
Keyword(s):  
Thermal Conductivity ◽  
Speed Of Sound ◽  
Thermal Transport ◽  
Large Scale ◽  
Lattice Thermal Conductivity ◽  
Layered Materials ◽  
Layered Structures ◽  
Polycrystalline Materials ◽  
Anisotropic Lattice ◽  
Average Factor

<div> <div> <div> <p>Thermal conductivity plays a crucial role in many applications; use of single-crystal and textured polycrystalline materials in such applications necessitate understanding the anisotropy in thermal transport. Measurement of anisotropic lattice thermal conductivity is quite challenging. To address this need through computations, we build upon our previously developed isotropic model for <i>k<sub>L</sub></i> and incorporate the directional (angular) dependence by using the elastic tensor obtained from <i>ab initio</i> calculations and the Christoffel equations for speed of sound. With the anisotropic speed of sound and intrinsic material properties as input parameters, we can predict the direction-dependent <i>k<sub>L</sub></i>. We validate this new model by comparing with experimental data from the literature – predicted <i>k<sub>L</sub></i> is within an average factor difference of 1.8 of experimental measurements, spanning 5 orders of magnitude in <i>k<sub>L</sub></i>. To demonstrate the utility and computational-tractability of this model, we calculate <i>k<sub>L </sub></i>of ~2200 layered materials that are expected to exhibit anisotropic thermal transport. We consider both van der Waals and ionic layered structures with binary and ternary chemistries and analyze the anisotropy in their <i>k<sub>L</sub></i>. The large-scale study has revealed many layered structures with interesting anisotropy in <i>k<sub>L</sub></i>.</p> </div> </div> </div>

scholarly journals Rapid Prediction of Anisotropic Lattice Thermal Conductivity: Application to Layered Materials

2018 ◽  
Author(s):  
Robert McKinney ◽  
Prashun Gorai ◽  
Eric S. Toberer ◽  
Vladan Stevanovic
Keyword(s):  
Thermal Conductivity ◽  
Speed Of Sound ◽  
Thermal Transport ◽  
Large Scale ◽  
Lattice Thermal Conductivity ◽  
Layered Materials ◽  
Layered Structures ◽  
Polycrystalline Materials ◽  
Anisotropic Lattice ◽  
Average Factor

<div> <div> <div> <p>Thermal conductivity plays a crucial role in many applications; use of single-crystal and textured polycrystalline materials in such applications necessitate understanding the anisotropy in thermal transport. Measurement of anisotropic lattice thermal conductivity is quite challenging. To address this need through computations, we build upon our previously developed isotropic model for <i>k<sub>L</sub></i> and incorporate the directional (angular) dependence by using the elastic tensor obtained from <i>ab initio</i> calculations and the Christoffel equations for speed of sound. With the anisotropic speed of sound and intrinsic material properties as input parameters, we can predict the direction-dependent <i>k<sub>L</sub></i>. We validate this new model by comparing with experimental data from the literature – predicted <i>k<sub>L</sub></i> is within an average factor difference of 1.8 of experimental measurements, spanning 5 orders of magnitude in <i>k<sub>L</sub></i>. To demonstrate the utility and computational-tractability of this model, we calculate <i>k<sub>L </sub></i>of ~2200 layered materials that are expected to exhibit anisotropic thermal transport. We consider both van der Waals and ionic layered structures with binary and ternary chemistries and analyze the anisotropy in their <i>k<sub>L</sub></i>. The large-scale study has revealed many layered structures with interesting anisotropy in <i>k<sub>L</sub></i>.</p> </div> </div> </div>

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