scholarly journals Extremely anisotropic van der Waals thermal conductors

Nature ◽  
2021 ◽  
Vol 597 (7878) ◽  
pp. 660-665
Author(s):  
Shi En Kim ◽  
Fauzia Mujid ◽  
Akash Rai ◽  
Fredrik Eriksson ◽  
Joonki Suh ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Integrated Circuits ◽  
Thermal Transport ◽  
Van Der Waals ◽  
Management Strategies ◽  
Anisotropy Ratio ◽  
Large Area ◽  
Thermal Anisotropy ◽  
Plane Direction ◽  
Dynamics Simulations

AbstractThe densification of integrated circuits requires thermal management strategies and high thermal conductivity materials1–3. Recent innovations include the development of materials with thermal conduction anisotropy, which can remove hotspots along the fast-axis direction and provide thermal insulation along the slow axis4,5. However, most artificially engineered thermal conductors have anisotropy ratios much smaller than those seen in naturally anisotropic materials. Here we report extremely anisotropic thermal conductors based on large-area van der Waals thin films with random interlayer rotations, which produce a room-temperature thermal anisotropy ratio close to 900 in MoS2, one of the highest ever reported. This is enabled by the interlayer rotations that impede the through-plane thermal transport, while the long-range intralayer crystallinity maintains high in-plane thermal conductivity. We measure ultralow thermal conductivities in the through-plane direction for MoS2 (57 ± 3 mW m−1 K−1) and WS2 (41 ± 3 mW m−1 K−1) films, and we quantitatively explain these values using molecular dynamics simulations that reveal one-dimensional glass-like thermal transport. Conversely, the in-plane thermal conductivity in these MoS2 films is close to the single-crystal value. Covering nanofabricated gold electrodes with our anisotropic films prevents overheating of the electrodes and blocks heat from reaching the device surface. Our work establishes interlayer rotation in crystalline layered materials as a new degree of freedom for engineering-directed heat transport in solid-state systems.

Role of Edge Chirality and Isotope Doping in Thermal Transport and Thermal Rectification in Graphene Nanoribbons

2011 ◽  
Author(s):  
Yan Wang ◽  
Xiulin Ruan
Keyword(s):  
Thermal Conductivity ◽  
Thermal Transport ◽  
Graphene Nanoribbons ◽  
Mass Density ◽  
Transport Processes ◽  
Phonon Modes ◽  
Cross Sectional ◽  
Thermal Rectification ◽  
The Difference ◽  
Dynamics Simulations

Thermal transport processes in graphene nanoribbons (GNRs) within and beyond the linear response regime has been studied using classical molecular dynamics simulations. Zigzag-edged GNRs have higher thermal conductivities than armchair-edged ones, and the difference diminishes with increasing width. Analysis on the cross-sectional distribution of heat flux reveals that edge atoms cannot transport thermal energy as efficiently as interior ones. Edge localization of phonon modes reduces thermal transport through edge carbon atoms, especially on armchair edges, which results in a lower thermal conductivity. Isotope (13C) doping can reduce the thermal conductivity of GNRs by 30%–40% by an addition of only ∼20% isotope atoms. The significant reduction in thermal conductivity is partially attributed to phonon localization induced by isotope defects, which is confirmed by phonon mode participation ratio analysis. We also demonstrate that a GNR asymmetric in edge chirality or mass density can generate considerable thermal rectification, which is essential for developing GNR-based thermal management devices.

Structure, Mechanical Properties, and Thermal Transport in Microporous Silicon Nitride Via Parallel Molecular Dynamics

1995 ◽  
Vol 408 ◽  
Author(s):  
Andrey Omeltchenko ◽  
Aiichiro Nakano ◽  
Rajiv K. Kalia ◽  
Priya Vashishta
Keyword(s):  
Mechanical Properties ◽  
Thermal Conductivity ◽  
Molecular Dynamics ◽  
Silicon Nitride ◽  
Elastic Constants ◽  
Thermal Transport ◽  
Entire System ◽  
Amorphous Silicon Nitride ◽  
Parallel Molecular Dynamics ◽  
Dynamics Simulations

AbstractMolecular dynamics simulations are performed to investigate structure, mechanical properties, and thermal transport in amorphous silicon nitride under uniform dilation. As the density is lowered, we observe the formation of pores below ρ = 2.6 g/cc and at 2.0 g/cc the largest pore percolates through the entire system. Effects of porosity on elastic constants, phonons and thermal conductivity are investigated. Thermal conductivity and Young's modulus are found to scale as ρ1.5 and ρ3.6, respectively.

Superlattice Analysis for Tailored Thermal Transport Characteristics

2006 ◽  
Author(s):  
E. S. Landry ◽  
A. J. H. McGaughey ◽  
M. I. Hussein
Keyword(s):  
Thermal Conductivity ◽  
Thermal Transport ◽  
Direct Method ◽  
Continuum Theory ◽  
Lennard Jones ◽  
Constituent Species ◽  
The Cross ◽  
Dynamics Simulations ◽  
Superlattice Period

Molecular dynamics simulations and the Green-Kubo method are used to predict the thermal conductivity of binary Lennard-Jones superlattices and alloys. The superlattice thermal conductivity trends are in agreement with those obtained through the direct method, verifying that the Green-Kubo method can be used to examine thermal transport in heterostructures. The simulation temperature and the constituent species are fixed while the superlattice period structure is varied with the goals of (i) minimizing the cross-plane thermal conductivity and (ii) maximizing the ratio of in-plane to cross-plane thermal conductivities. The superlattice thermal conductivity in both the cross-plane and in-plane directions is found to be greater than the corresponding alloy value and less than the value predicted from continuum theory. The anisotropy of the thermal conductivity tensor is found to be at a maximum for a superlattice with a uniform layer thickness. Lattice dynamics calculations are used to investigate the role of optical phonons in the thermal transport.

scholarly journals Effect of Phase Transition on the Thermal Transport in Isoreticular DUT Materials

2021 ◽  
Author(s):  
Penghua Ying ◽  
Jin Zhang ◽  
Zheng Zhong
Keyword(s):  
Phase Transition ◽  
Thermal Conductivity ◽  
Transport Property ◽  
Thermal Transport ◽  
Phonon Scattering ◽  
Transition Process ◽  
Thermal Transport Property ◽  
Potential Applications ◽  
Flexible Metal ◽  
Dynamics Simulations

<p></p><p>Soft porous crystals (SPCs) or flexible metal-organic frameworks have great potential applications in gas storage and separation, in which SPCs can undergo phase transition due to external stimuli. Thus, understanding the effect of phase transition on the thermal transport in SPCs becomes extremely crucial, because the latent heat generated in aforementioned applications is needed to be effectively removed. In this paper, taking the isorecticular DUT series as an example, the thermal transport property of SPCs during the phase transition from the large pore (lp) phase to the narrow pore (np) phase is comprehensively investigated by molecular dynamics simulations together with the Green-Kubo method. According to our calculations, all DUT structures exhibit an ultralow thermal conductivity smaller than 0.2 Wm<sup>-1</sup>K<sup>-1</sup>. In addition, we find that the effect of phase transition on the thermal transport property of different DUT materials considered here strongly depends on their porosity. As for DUT-48, its lp phase has a thermal conductivity larger than that of its np phase. However, in other DUT materials, i.e, DUT-47, DUT-49, DUT-50, and DUT-151 the thermal transport property of their lp phase is found to be weaker than that of their np phase. This complicated effect of phase transition on the thermal transport in SPCs can be explained by a porosity-dominated competition mechanism between the increased volumetric heat capacity and the aggravated phonon scattering during the phase transition process.</p><p></p>

scholarly journals Thermal Transport in One-Dimensional Van Der Waals Heterostructures: Effects of Coating Layers on the Thermal Conductivity of Carbon Nanotubes

2020 ◽  
Author(s):  
Penghua Ying ◽  
Jin Zhang ◽  
Yao Du ◽  
Zheng Zhong
Keyword(s):  
Heat Flux ◽  
Thermal Transport ◽  
Van Der Waals ◽  
Thermal Conductance ◽  
One Dimensional ◽  
Interfacial Thermal Conductance ◽  
Quantitative Understanding ◽  
Non Equilibrium Molecular Dynamics ◽  
Dynamics Simulations ◽  
The Individual

In this paper, we conduct a comprehensive investigation on the thermal transport in one-dimensional (1D) van der Waals (vdW) heterostructures by using non-equilibrium molecular dynamics simulations. It is found that the boron nitride nanotube (BNNT) coating can increase the thermal conductance of inner carbon nanotube (CNT) base by 36%, while the molybdenum disulfide nanotube (<a>MSNT</a>) coating can reduce the thermal conductance by 47%. The different effects of BNNT and MSNT coatings on the thermal transport behaviors of 1D vdW heterostructures are explained by the competition mechanism between improved heat flux and increased temperature gradient in 1D vdW heterostructures. By taking CNT@BNNT@MSNT as an example, thermal transport in 1D vdW heterostructures containing three layers is also investigated. It is found that the coaxial BNNT-MSNT coating can significantly reduce the thermal conductance of inner CNT base by 61%, which is even larger than that of an individual MSNT coating. This unexpected reduction in thermal conductance of CNT@BNNT@MSNT can be explained by the suppression of heat flux arising from the possible compression effect, since BNNT-MSNT coating in CNT@BNNT@MSNT can more significantly suppress the vibration of inner CNT when compared to the individual MSNT coating in CNT@MSNT. In addition to the in-plane thermal transport, the interfacial thermal conductance between inner and outer nanotubes in 1D vdW heterostructures is also examined to provide a quantitative understanding of the thermal transport behaviors of1D vdW heterostructures. This work is expected to provide molecular insights into tailoring the heat transport in carbon base 1D vdW heterostructures and thus facilitate their broader applications as thermal interface materials.

Optimized Design of Composite Materials for Heat Transport Applications

2011 ◽  
Author(s):  
Babak Kouchmeshky ◽  
Peter Kroll ◽  
Ibukun Olubanjo
Keyword(s):  
Thermal Conductivity ◽  
Composite Materials ◽  
Thermal Transport ◽  
Elevated Temperatures ◽  
Phonon Scattering ◽  
Optimized Design ◽  
Individual Contributions ◽  
Non Equilibrium Molecular Dynamics ◽  
Dynamics Simulations ◽  
The Individual

Careful design of composite materials offers a chance for engineering phonon band gaps and controlling phonon scattering. Taking advantage of this strategy, we study properties of SiC composite materials for engineering applications in which the control of thermal transport is important. In particular, knowledge of the individual contributions of phonons on thermal transport provides us the necessary information to focus on most significant phonon frequencies. In our study, we select a series of candidate model geometries and use a virtual testing method for elevated temperatures to support the design process. Integrating atomistic non-equilibrium molecular dynamics simulations to determine thermal conductivity we provide a proof-of-concept study and deliver best design scenarios of SiC composite materials with very low-thermal conductivity.

Thermal Transport in Nanotube Composites for Large-Area Macroelectronics

2005 ◽  
Author(s):  
Satish Kumar ◽  
Muhammad A. Alam ◽  
Jayathi Y. Murthy
Keyword(s):  
Thermal Conductivity ◽  
Effective Thermal Conductivity ◽  
Thermal Transport ◽  
Channel Length ◽  
Tube Length ◽  
Finite Volume Scheme ◽  
Large Area ◽  
Contact Conductance ◽  
Channel Lengths ◽  
Contact Parameters

Thermal transport in a new class of nanocomposites composed of isotropic 2D ensembles of nanotubes or nanowires in a substrate is considered for use as the channel region of thin film transistors. The random ensemble is generated numerically and simulated using a finite volume scheme. The effective thermal conductivity of a nanotube network embedded in a thin substrate is computed. Percolating conduction in the composite is studied as a function of wire/tube densities and channel lengths. The conductance exponents are validated against available experimental data for long channels devices. The effect of tube-tube contact conductance, tube-substrate contact conductance and substrate-tube conductivity ratio is analyzed for various channel lengths. It is found that beyond a certain limiting value, contact parameters do not result in any significant change in the effective thermal conductivity of the composite. It is also observed that the effective thermal conductivity of the composite saturates beyond a limiting channel-length/tube length ratio for the range of contact parameters under consideration.

scholarly journals Impact of screw and edge dislocations on the thermal conductivity of individual nanowires and bulk GaN: a molecular dynamics study

2018 ◽  
Vol 20 (7) ◽  
pp. 5159-5172 ◽  
Author(s):  
Konstantinos Termentzidis ◽  
Mykola Isaiev ◽  
Anastasiia Salnikova ◽  
Imad Belabbas ◽  
David Lacroix ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Molecular Dynamics ◽  
Molecular Dynamics Simulations ◽  
Transport Properties ◽  
Thermal Transport ◽  
Thermal Transport Properties ◽  
Bulk Gan ◽  
Dynamics Simulations ◽  
Edge Dislocations

The thermal transport properties of nanowires and bulk GaN in the presence of different dislocations using molecular dynamics simulations are reported.

scholarly journals Lattice thermal transport in two-dimensional alloys and fractal heterostructures

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Aravind Krishnamoorthy ◽  
Nitish Baradwaj ◽  
Aiichiro Nakano ◽  
Rajiv K. Kalia ◽  
Priya Vashishta
Keyword(s):  
Thermal Conductivity ◽  
Thermal Transport ◽  
Lattice Thermal Conductivity ◽  
Material Design ◽  
Two Dimensional ◽  
Scale Free ◽  
Dopant Atoms ◽  
Non Equilibrium Molecular Dynamics ◽  
Dynamics Simulations ◽  
The Impact

AbstractEngineering thermal transport in two dimensional materials, alloys and heterostructures is critical for the design of next-generation flexible optoelectronic and energy harvesting devices. Direct experimental characterization of lattice thermal conductivity in these ultra-thin systems is challenging and the impact of dopant atoms and hetero-phase interfaces, introduced unintentionally during synthesis or as part of deliberate material design, on thermal transport properties is not understood. Here, we use non-equilibrium molecular dynamics simulations to calculate lattice thermal conductivity of $${\mathrm {(Mo|W)Se_2}}$$ ( Mo | W ) Se 2 monolayer crystals including $${\mathrm {Mo}}_{1-x}{\mathrm {W}}_x{\mathrm {Se_2}}$$ Mo 1 - x W x Se 2 alloys with substitutional point defects, periodic $${\mathrm {MoSe_2}|\mathrm {WSe_2}}$$ MoSe 2 | WSe 2 heterostructures with characteristic length scales and scale-free fractal $${\mathrm {MoSe_2}}|{\mathrm {WSe_2}}$$ MoSe 2 | WSe 2 heterostructures. Each of these features has a distinct effect on phonon propagation in the crystal, which can be used to design fractal and periodic alloy structures with highly tunable thermal conductivities. This control over lattice thermal conductivity will enable applications ranging from thermal barriers to thermoelectrics.

Thermal Transport in Graphene Supported on Copper

2012 ◽  
Author(s):  
Liang Chen ◽  
Satish Kumar
Keyword(s):  
Thermal Conductivity ◽  
Thermal Transport ◽  
Copper Substrate ◽  
Interaction Strength ◽  
Thermal Coupling ◽  
Phonon Modes ◽  
Large Wave ◽  
Relaxation Time Approximation ◽  
Out Of Plane ◽  
Dynamics Simulations

The present study investigates the thermal transport in suspended graphene and graphene supported on copper substrate using equilibrium molecular dynamics simulations, Green-Kubo method and relaxation time approximation (RTA) approach. The thermal coupling between graphene and copper substrate was investigated by varying the interaction strength between the carbon atoms and Cu atoms at the interface. The contribution of different phonon modes to the thermal conductivity of suspended and supported graphene was analyzed in order to elucidate the graphene-substrate thermal interactions. The thermal conductivity of graphene decreases with the increasing strength of the interfacial interaction. The analysis shows that the interactions with copper substrate can reduce the thermal conductivity by up to 44%. The decrease of thermal conductivity is primarily due to the suppression of contribution from out-of-plane acoustic (ZA) phonons in the large wave vector region.

Sign in / Sign up

Export Citation Format

Share Document