The transport processes of mass, momentum, and heat in nanoscale systems are dominated by the large surface-to-volume ratio inherent at this length scale. To understand these processes we have to extend our macroscale models to include the effect of the micro structure eg.: surface chemistry, atomic scale corrugation, and fluid- and and solid impurities. In this rearch we study nanoscale heat transfer and we apply tempeture gradients to drive solid and fluid nanoparticles.
Thermophoretic Motion of Gold and Water Nanodroplets Confined inside Carbon Nanotubes
We study the thermophoretic motion of solid gold nanoparticles and water nanodroplets confined inside carbon nanotubes using molecular dynamics simulations. The nanodroplet moves in the direction opposite to the imposed thermal gradient with a terminal velocity that is linearly proportional to the gradient. We find that the motion along the axial is associated with a solid body rotation of the water nanodroplet that follows the helical symmetry of the carbon nanotube.
Thermal Conductivity of Carbon Nanotubes in Aqueous Solutions
Carbon nanotube (CNT) suspensions in alpha-alkene liquids have exhibited marked increases in thermal conductivity, leading to interest in these systems for heat management applications. Pristine CNTs have large thermal conductivity in the axial direction, but small values have been observed in the radial direction between CNTs and surrounding media. The objective of our study is to determine the characteristics of the solution that can maximize this radial heat transfer.
Hexanamine mediates the thermal properties of solvated CNTs. Hexanamine (CH3-(CH2)5-NH2) is added to the system to study the thermal resinstance of solvated CNTs. The results obtained from the NEMD simulations of the pristine carbon nanotube-water system reveal a significant jump in the water temperature at the interface.
Kapitza resistance between water and graphene
Several studies have indicated that graphene is a promising material for improved heat dissipation in integrated chips due to its high thermal conductivity. Of particular interest are suspensions of nanoscale graphene flakes and carbon nanotubes in liquids as they exhibit substantially larger thermal conductivity than that of pure liquids. However, there is a discrepancy of more than an order of magnitude between the theoretically predicted and the measured thermal conductivity of nanofluids. This discrepancy is attributed to uncertainties on the value of the interfacial thermal (Kapitza) resistance.
We have investigated the thermal transport across water−graphene interface through Non-Equilibrium Molecular Dynamics simulations. Among our findings is the fact that the Kapitza resistance is critically affected by the water layering at the interface and more specifically by the value of the first density peak of water adjacent to the interface. The magnitude of the first density peak of a liquid adjacent to the solid may be tuned to control the heat dissipation in micro- and nanofluidic systemsю
People: Alvaro Foletti, Jens Honoré Walther, Jie Chen, Dmitry Alexeev
People: Professor Chriostofer Hierold (ETHZ), Dr. Richard Jaffe (NASA Ames), Professor Eftimios Kaxiras (Harvard), Harvey Zambrano (Technical University of Denmark)
Publications
2016
- J. Chen, J. H. Walther, and P. Koumoutsakos, “Ultrafast cooling by covalently bonded graphene-carbon nanotube hybrid immersed in water,” Nanotechnology, vol. 27, iss. 46, p. 465705, 2016.