[Paper Review] Interfacial thermal conductance between TiO2 nanoparticle and water: A molecular dynamics study

Mahdi Roodbari, Mohsen Abbasi+3 more|arXiv (Cornell University)|Nov 7, 2021

Thermal properties of materials55 references35 citations

TL;DR

This study uses transient non-equilibrium molecular dynamics (TNEMD) to investigate interfacial thermal conductance between TiO2 nanoparticles and water, revealing it is one order of magnitude higher than for conventional nanoparticles like gold or graphene. The enhanced conductance is primarily due to strong electrostatic interactions between charged Ti and O atoms in TiO2 and water molecules, which significantly reduce thermal relaxation time compared to van der Waals-dominated systems.

ABSTRACT

The interfacial thermal conductance (Kapitza conductance) between a TiO2 nanoparticle and water is investigated using transient non-equilibrium molecular dynamics. It is found that Kapitza conductance of TiO2 nanoparticles is one order of magnitude greater than other conventional nanoparticles such as gold, silver, silicon, platinum and also carbon nanotubes and graphene flakes. This difference can be explained by comparing the contribution of electrostatic interactions between the partially charged titanium and oxygen atoms and water atoms to the van der Waals interactions, which increases the cooling time by about 10 times. The effects of diameter and temperature of nanoparticle, surface wettability on the interfacial thermal conductance are also investigated. The results showed that by increasing the diameter of the nanoparticle from 4 to 9 nm, Kapitza conductance decreased slightly. Also, increasing the temperature of the heated nanoparticle from 400 K to 600 K led to thermal conductance enhancement. It has been found that increasing the coupling strength of Lennard-Jones (LJ) potential from 0.5 to 4 caused the increment of the Kapitza conductance about 20%. It is also shown that a continuum model which its input is provided by molecular dynamics can be a suitable approximation to describe the thermal relaxation of a nanoparticle in a liquid medium.

Motivation & Objective

• To investigate the interfacial thermal conductance between TiO2 nanoparticles and water at the atomic scale.
• To determine the influence of nanoparticle diameter (4–9 nm), temperature (400–600 K), surface wettability, and Coulombic interactions on thermal conductance.
• To evaluate the role of electrostatic forces relative to van der Waals interactions in enhancing heat transfer at the solid-liquid interface.
• To compare molecular dynamics results with a continuum heat conduction model for thermal relaxation prediction.
• To assess the validity of continuum models in approximating nanoparticle cooling dynamics in liquid media.

Proposed method

• Transient non-equilibrium molecular dynamics (TNEMD) was used to compute interfacial thermal conductance between TiO2 nanoparticles and water.
• The TIP4P/2005 water model was employed with Lennard-Jones and Coulombic potentials to describe intermolecular forces.
• LAMMPS was used for large-scale molecular dynamics simulations with nanoparticle diameters ranging from 4 to 9 nm.
• The finite volume method (FVM) solved the transient heat conduction equations in a continuum model, using MD-derived inputs such as interfacial conductance and thermal properties.
• The continuum model assumed a static fluid, while MD accounted for water molecule advection, enabling comparison of cooling dynamics.
• Sensitivity analyses were performed on nanoparticle temperature, diameter, and Lennard-Jones potential strength to assess their effects on conductance.

Experimental results

Research questions

• RQ1 How does the interfacial thermal conductance of TiO2 nanoparticles compare to that of other common nanoparticles like gold, silver, and carbon nanotubes in water?
• RQ2 What is the effect of nanoparticle diameter (4–9 nm) and temperature (400–600 K) on interfacial thermal conductance?
• RQ3 How do electrostatic (Coulombic) interactions between TiO2 and water molecules influence thermal conductance compared to van der Waals forces?
• RQ4 To what extent does the inclusion of water molecule motion (advection) affect the thermal relaxation time of a heated nanoparticle?
• RQ5 Can a continuum heat conduction model, informed by MD simulations, accurately predict the thermal relaxation of a nanoparticle in water?

Key findings

• The interfacial thermal conductance between TiO2 and water is approximately 1682 MW/m²K for a 4 nm nanoparticle, which is one order of magnitude higher than for gold (215 MW/m²K), silver (460 MW/m²K), platinum, silicon, and carbon nanotubes.
• Increasing the nanoparticle diameter from 4 to 9 nm leads to a slight decrease in interfacial thermal conductance, with G dropping from 1682 to 1596 MW/m²K.
• Raising the nanoparticle temperature from 400 K to 600 K enhances thermal conductance, indicating a positive temperature dependence in the heating phase.
• Increasing the Lennard-Jones potential strength from 0.5 to 4 results in a 20% increase in interfacial thermal conductance, indicating strong coupling dependence.
• Excluding Coulombic interactions reduces the thermal conductance by nearly two orders of magnitude, confirming that electrostatic forces dominate over van der Waals interactions in TiO2-water systems.
• The thermal relaxation time from MD simulations closely matches that predicted by a continuum conduction model using MD-derived inputs, validating the use of such models for nanoparticle cooling in liquids.