Carbon Nano Fiber Enhanced Polymers as Flexible Thermal Interface Materials
This work is focused on carbon nano fiber/polymer composites for applications as thermal interface materials. Vertically grown and aligned carbon nanofibers have been embedded in a PDMS film through spin coating and curing. The thermal contact resistance is then directly measured using a stepped-bar apparatus. Preliminary results (when successfully fabricated) show that the addition of the carbon nanofibers reduces the thermal contact resistance when compared to that of the PDMS film. Future work in this area will explore the use of other carbon nanomaterials like carbon nanotubes and graphene as well as studies at the microscopic level to better understand phonon transport at the carbon nanomaterial/polymer interface.
Thermal Boundary Resistance from Mass and Lattice Difference Scattering
The goal of this work is to understand the individual contributions of mass-difference and lattice-difference phonon scattering at an interfaces. This work focuses on Si/NiSi systems due to the ability to manipulate the mass-difference and lattice-difference independently through varying the fabrication process. Experimental measurements of the thermal conductivity using the 3-omega technique are being performed over a range of frequencies to extract the thermal boundary conductance. This work is supported by the ORAU Ralph E. Powe Junior Faculty Enhancement Award FY2014-141. A portion of this research is being conducted at the Center for Nanophase Materials Science, which is sponsored at Oak Ridge National Laboratory by the Scientific User Facilities Division, Office of Basic Energy Sciences, U.S. Department of Energy.
Waste Heat Recovery using a Combined Nanoenhanced Phase Change Material and Thermoelectric Device
The goal of this work is to develop a thermal energy harvesting system that uses nanoenhanced paraffin based phase change materials to store and release thermal energy and a thermoelectric device to convert the thermal energy to electricity. The approach to this system is two-fold. (1) Enhancing the thermal conductivity of paraffin based phase change materials through the addition of thermally conductivity nanomaterials (like graphene) and (2) to design and optimize a combined phase change material and thermoelectric system to harvest solar and low grade waste heat. Preliminary results show drastic improvements in thermal conductivity with the addition of nanoparticles. The current effort is focused on understanding and optimizing thermal conductivity of the phase change material without a reduction in the latent heat of fusion. Future efforts will focus on a microscopic understanding of the thermal transport at the nanomaterial/paraffin interface and the system design of an energy harvesting system based on heat source and the phase change material.
Facile Synthesis of Carbon Nanomaterial Solutions and Powders
The goal of this work is to develop simple and repeatable processes for the synthesis of carbon nanomaterial solutions and powders. This effort stems from the study of carbon nanomaterial composites highlighted above. The current approach has been applied to the synthesis of graphene through the exfoliation of graphite and the suspension of carbon nanotubes from a chemical vapor deposition process. Both cases use ultrasonication with the addition of a surfactant to produced solutions and vacuum oven dehydration to produce surfactant coated powders that can be used in other liquids or materials.