Nanoparticle-based materials are of interest because of their unique thermal properties. Possessing the lowest thermal conductivities of any solid materials known, they have been widely used as insulating materials in a variety of macroscale and microscale applications.
The present work focuses on two main aspects of thermal transport between amorphous silica nanoparticles. The first area of focus was to investigate the effect of interfacial force strength on thermal transport between amorphous silica nanoparticles under vacuum. Using non-equilibrium molecular dynamics (NEMD) simulations, we calculate the total thermal resistance and thermal boundary resistance between adjacent silica nanoparticles. Numerical results are compared to interparticle resistances determined from experimental measurements of heat transfer across packed silica nanoparticle beds. The thermal resistance between nanoparticles is shown to increase rapidly as the particle contact radius decreases. More significantly, the interparticle resistance depends strongly on the forces between particles, in particular, the presence or absence of chemical bonds between nanoparticles. In addition, the effect of interfacial force strength on thermal resistance increases as the nanoparticle diameter decreases. The simulations results are shown to be in good agreement with experimental results for 20 nm silica nanoparticles.
The second area of focus was to investigate the effect of water vapor on thermal transport between amorphous silica nanoparticles. Using NEMD simulations, we calculate the total thermal resistance and thermal boundary resistance between adjacent spherical silica nanoparticles when water molecules are allowed to diffuse as vapor into the interstitial pores between particles. The thermal resistance between nanoparticles is shown to decrease rapidly when water vapor is introduced into the pores between particles. Most of the decrease in interparticle resistance occurs as a result of the silanization of the silica particle surfaces. A secondary decrease is attributable to the liquid bridge that forms as water molecules condense around the contact point between nanoparticles. Numerical results are compared to experimental measurements of heat transfer across packed beds of 20 nm silica nanoparticles exposed to water vapor. The simulation results are shown to be consistent with the experimental measurements for relative humidities below 15% rh, while underpredicting the experimental measurements above 15% rh.
|Advisor:||Richards, Robert F., Liu, Jin|
|Commitee:||Richards, Cecilia D.|
|School:||Washington State University|
|School Location:||United States -- Washington|
|Source:||DAI-B 80/03(E), Dissertation Abstracts International|
|Keywords:||Molecular dynamics, Silica nanoparticle, Thermal resistance|
Copyright in each Dissertation and Thesis is retained by the author. All Rights Reserved
The supplemental file or files you are about to download were provided to ProQuest by the author as part of a
dissertation or thesis. The supplemental files are provided "AS IS" without warranty. ProQuest is not responsible for the
content, format or impact on the supplemental file(s) on our system. in some cases, the file type may be unknown or
may be a .exe file. We recommend caution as you open such files.
Copyright of the original materials contained in the supplemental file is retained by the author and your access to the
supplemental files is subject to the ProQuest Terms and Conditions of use.
Depending on the size of the file(s) you are downloading, the system may take some time to download them. Please be