SYNTHESIS, CHARACTERIZATION AND PROCESSING OF THERMAL MANAGEMENT MATERIALS

Due to increasing average global temperatures, the energy used for space cooling in buildings will increase by 300% by 2050 and account for 13% of all electricity usage worldwide. Consequently, to meet global cooling demand, fossil fuels and refrigerants, which release carbon dioxide and volatile chemicals with large global warming potentials, will be used at higher rates. This increase in greenhouse gas emissions results in a growing demand for space cooling. Several energy consumption models indicate the importance of reducing energy usage to slow the rate of global warming.[1] Improving the performance of thermal materials can directly reduce the amount of energy required for space cooling by reducing the thermal load on buildings.[2]. Therefore, the synthesis, characterization and processing of passive and dynamic thermal management materials will be critical in efforts to reduce these thermal loads in buildings. In this thesis, the theoretical framework that predicts the effective thermal conductivity of superinsulating hollow silica nanoparticles in a binary matrix is first presented. Discussion of the framework is then followed by the synthesis process needed to achieve the designated particle parameters. Additionally, electromagnetic properties of thin films are presented to inform the design parameters for dielectric mirrors. This thesis addresses four specific questions to contribute to working scientific knowledge of passive and dynamic insulating materials. First, a parametric study was completed to investigate the physical parameters that govern the effective thermal conductivity of hollow silica nanoparticles. Second, the thermal assessment of ternary composite materials consisting of hollow silica nanoparticles with carbon fillers in between particle clusters was evaluated. Third, the means for characterizing the mechanism and degree of thermal switchability achieved by polymer dielectric mirrors used to variably reflect solar radiation over a tunable range was elicited and detailed. Lastly, in-situ techniques to characterize the dielectric mirror’s thermal conductivity and chemical state as a function of switching degrees is presented. The thesis provides a deeper understanding of the relationship between hollow silica nanoparticles design and performance and provide necessary information to further develop the foundation of thermally switching used for dynamic thermal conduction and radiation management.Ph.D

Hollow Silica Particles: A Novel Strategy for Cost Reduction

Thermal insulation materials are highly sought after for applications such as building envelopes, refrigerators, cryogenic fuel storage chambers, and water supply piping. However, current insulation materials either do not provide sufficient insulation or are costly. A new class of insulation materials, hollow silica particles, has attracted tremendous attention due to its potential to provide a very high degree of thermal insulation. However, current synthesis strategies provide hollow silica particles at very low yields and at high cost, thus, making the particles unsuitable for real-world applications. In the present work, a synthesis process that produces hollow silica particles at very high yields and at a lower cost is presented. The effect of an infrared heat absorber, carbon black, on the thermal conductivity of hollow silica particles is also investigated and it is inferred that a carbon black–hollow silica particle mixture can be a better insulating material than hollow silica particles alone