Moreover, pressure is set to 1 bar by Parrinello-Rahman barostat during both thermal equilibration and subsequent non-equilibrium computation.
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Steady-state MD simulations. Dimensionless temperature computed by MD symbols versus temperature profile predicted by continuous model line , Equation Case with computational box 2. We stress that L NH is the axial length of the outermost carbon atom rings coupled to a thermostat at each end of a nanotube. In our case, we find highly efficient nanofins:. The value of thermal boundary conductance between water and a SW-CNT has been assessed by transient simulations as well. Next, an NVE MD ensemble where number of particle N, system volume V and energy E are conserved were performed, where the entire system SWNT plus water was allowed to relax without any temperature and pressure coupling.
Under the assumption of a uniform temperature field T CNT t within the nanotube at any time instant t i. Transient simulations: temperature evolution as predicted by NVE molecular dynamics. It is worth stressing that values for thermal boundary conductance obtained in this study are consistent with both experimental and numerical results found by others for SW-CNTs within liquids [ 20 , 45 ]. However, since the order of magnitude of these results is extremely higher than that involved in macroscopic applications, it may appear as an artifact.
Actually, it is quite simple to realize that continuum-based models diverge in case of nanometer dimensions, because of the effects of singularity. Hence, continuum-based predictions may lead to even higher thermal conductances, and they are not even upper bounded, which is clearly unphysical. For example, let us consider the ideal case of a circular cylinder with diameter D and length L centered in a square solid of equal length, as reported in Table 3.
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The value of thermal boundary conductance can be put into relation with the heat conduction shape factor CSF S f as follows:. The analytic results are even larger than those obtained by the steady-state simulation usually larger than those obtained by the transient method. Moreover, the continuum-based formula prescribes that thermal conductance weakly diverges by reducing the cylinder diameter. On the contrary, MD simulations is in line with the expectation of a bounded thermal boundary conductance.
In fact, in agreement with others [ 45 ], we even observe a slight decrease with the tube diameter. We point out that neither the steady-state method nor the transient method fully reproduce the setup described by the analytic formula In fact, in the steady-state method, the entire water bath is thermostatted while in the analytic formula, only the water boundaries are thermostatted and, in the transient method, the water temperature changes in time while the analytic formula is derived under steady-state condition.
Nevertheless, from the technological point of view, the above results are in line with the basic idea that high aspect-ratio nanostructures such as CNTs are suitable candidates for implementing the above idea of nanofin , and thus can be utilized for exploiting advantageous heat boundary conductances. In this study, we first investigated the thermal conductivity of SW-CNTs by means of classical non-equilibrium MD using both simplified one-dimensional and fully three-dimensional models.
Next, based on the latter results, we have focused on the boundary conductance and thermal efficiency of SW-CNTs used as nanofins within water. Wang L, Fan J: Nanofluids research: key issues. Nanoscale Res Lett , 5: — Small , 3: — Curr Appl Phys , 6: — Int J Thermophys , — Part 1. Synthesis and properties of nanofluids.
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Phys Rev B , Hoboken: Wiley; Nat Mater , 2: — Appl Phys Lett , Stevens R, Zhigilei L, Norris P: Effects of temperature and disorder on thermal boundary conductance at solid-solid interfaces: nonequilibrium molecular dynamics simulations. Savin A, Gendelman O: Heat conduction in one-dimensional lattices with on-site potential. Phys Rev E , Phys Lett A , 85— Liu Z, Li B: Heat conduction in simple networks: the effect of interchain coupling. Phys Rev E Nianbei L: Effective phonon theory of heat conduction in 1 D nonlinear lattice chains.
PhD thesis. National University of Singapore, Department of Physics; Musser D: On propagation of heat in atomistic simulations. Master thesis by University of Akron; Li B, Wang L: Thermal logig gates: computation with phonons.
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Phys Rev E , — J Appl Phys , — Zhong H, Lukes JR: Interfacial thermal resistance between carbon nanotubes: molecular dynamics simulations and analytical thermal modeling. J Mol Graph , 47— Download references. The authors owe their appreciation to Mr. Marco Giardino for his kind assistance whenever the authors had difficulites with computational facilities. The authors also thank Dr. Andrea Minoia and Dr. The authors acknowledge also the inspiring discussions with Dr. Correspondence to Pietro Asinari.
Motivation for investigating the nanofin idea was initially provided by PA, and thereafter refined by an active interaction between both authors. Computations of thermal conductivity with different combinations of interaction potentials, as reported in Figure 5 , were performed by PA. Authors contributed equally in writing the present manuscript. Reprints and Permissions. Search all SpringerOpen articles Search. Nano Express Open Access Published: 22 March Enhancing surface heat transfer by carbon nanofins: towards an alternative to nanofluids?
Abstract Background Nanofluids are suspensions of nanoparticles and fibers which have recently attracted much attention because of their superior thermal properties. Results Toward the end of implementing the above idea, we focus on single carbon nanotubes to enhance heat transfer between a surface and a fluid in contact with it. Figure 1.
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Full size image. Heat conductivity of SW-CNTs: a simplified model In order to significantly downgrade the difficulty of studying energy transport processes within a CNT, some authors often resort to simplified low-dimensional systems such as one-dimensional lattices [ 23 — 28 ]. Figure 3. Table 1 Parameters for carbon-carbon, carbon-water, and water-water interactions are chosen according to Guo et al. Figure 4.
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Figure 5. Table 2 Summary of the results of MD simulations in this study. Full size table.
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Thermal boundary conductance of a carbon nanofin in water Steady-state simulations In this section, we investigate on the heat transfer between a carbon nanotube and a surrounding fluid water. Figure 7. Figure 8. These metrics are regularly updated to reflect usage leading up to the last few days. Citations are the number of other articles citing this article, calculated by Crossref and updated daily.
Find more information about Crossref citation counts. The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric. Find more information on the Altmetric Attention Score and how the score is calculated. We report a method for growing rectangular InAs nanofins with deterministic length, width, and height by dielectric-templated selective-area epitaxy.
These freestanding nanofins can be transferred to lay flat on a separate substrate for device fabrication. A key goal was to regain a spatial dimension for device design compared to nanowires, while retaining the benefits of bottom-up epitaxial growth. The transferred nanofins were made into devices featuring multiple contacts for Hall effect and four-terminal resistance studies, as well as a global back-gate and nanoscale local top-gates for density control.
Hall studies give a 3D electron density 2.