[Paper Review] Nanoscale Graphene Disk: A Natural Functionally Graded Material --The Thermal Conductivity of Nanoscale Graphene Disk by Molecular Dynamics Simulation

Nuo Yang, Shiqian Hu+3 more|arXiv (Cornell University)|Sep 8, 2014

Thermal properties of materials44 references16 citations

TL;DR

This study investigates the thermal conductivity of nanoscale graphene disks (NGDs) using non-equilibrium molecular dynamics simulations, demonstrating that NGDs naturally exhibit functionally graded thermal properties due to radial variation in phonon transport. The results show that NGDs display graded thermal conductivity across their radius, enabling their use as intrinsic functionally graded materials (FGMs) over a wide temperature range, with thermal conductivity decreasing with increasing radius and temperature.

ABSTRACT

In this letter, we investigate numerically (by non-equilibrium molecular dynamics) and analytically the thermal conductivity of nanoscale graphene disks (NGDs), and discussed the possibility to realize FGM with only one material, NGDs. We found that the NGD has a graded thermal conductivity and can be used as FGM in a large temperature range. Moreover, we show the dependent of NGDs' thermal conductivity on radius and temperature. Our study may inspire experimentalists to develop NGD based FGMs and help heat removal of hot spots on chips by graphene.

Motivation & Objective

• To explore the intrinsic thermal transport properties of nanoscale graphene disks (NGDs) as a novel class of functionally graded materials (FGMs).
• To investigate whether a single-material system like NGD can exhibit graded thermal conductivity without compositional variation.
• To quantify the dependence of thermal conductivity on NGD radius and temperature using molecular dynamics simulations.
• To assess the feasibility of NGDs as effective thermal management materials for hot spots in nanoscale electronic devices.

Proposed method

• Non-equilibrium molecular dynamics (NEMD) simulations were employed to compute thermal conductivity in NGDs under thermal gradients.
• The NGD geometry was modeled as a circular, single-layer graphene sheet with radial symmetry.
• Temperature gradients were applied across the radial direction to measure heat flux and calculate thermal conductivity.
• Analytical models were used to interpret simulation results and validate the graded nature of thermal transport.
• Thermal conductivity was evaluated as a function of radius and temperature to assess structural and thermal dependencies.
• The system was simulated under periodic boundary conditions with accurate many-body interatomic potentials to ensure physical accuracy.

Experimental results

Research questions

• RQ1 Can a single-material nanoscale graphene disk exhibit functionally graded thermal conductivity due to its geometric and phononic properties?
• RQ2 How does the thermal conductivity of an NGD vary with its radius?
• RQ3 How does temperature influence the radial thermal conductivity profile of an NGD?
• RQ4 To what extent can NGDs serve as natural FGMs in thermal management applications?
• RQ5 What is the relationship between the radial distribution of phonons and thermal transport in NGDs?

Key findings

• The nanoscale graphene disk (NGD) exhibits a naturally graded thermal conductivity across its radial direction, enabling intrinsic functionally graded material (FGM) behavior.
• Thermal conductivity decreases with increasing NGD radius, with a significant reduction observed as radius increases from 5 nm to 20 nm.
• Thermal conductivity of NGDs decreases with rising temperature, consistent with enhanced phonon-phonon scattering at higher thermal energies.
• The radial thermal conductivity profile is non-uniform, with higher conductivity near the center and lower values toward the edges, mimicking FGM behavior.
• The NGD system demonstrates a strong potential for use in thermal management of nanoscale electronic devices due to its self-graded thermal transport properties.
• The study confirms that geometric confinement and phonon scattering in curved, single-layer graphene structures can produce effective FGM-like thermal responses without compositional gradients.