Missouri University of Science and Technology
Synthesis and applications of ceramic (silicon carbide and silicon nitride), metallic (cobalt(0)) and polymeric (polyurethane) aerogels
Abstract
dc:description.abstract"A new method has been demonstrated for the synthesis of monolithic ceramic and purely metallic aerogels from xerogel powder compacts, and the use of polyurethane aerogels based on cyclodextrins as efficient desiccants.</p><p>I. Highly porous ( > 80%) monolithic SiC and Si<sub>3</sub>N<sub>4</sub>, aerogels were prepared from compressed compacts of polyurea-crosslinked silica xerogel powders. The process is time efficient as solvent-exchange through powders is fast, and energy efficient as it bypasses drying with supercritical fluids. The final ceramic objects were chemically pure, sturdy, with compressive moduli at 37 ±7 MPa and 59 ± 7 MPa, and thermal conductivities at 0.16<sub>3</sub> ± 0.010 W m<sup>-1</sup> K<sup>-1</sup> and 0.070 ± 0.001 W m<sup>-1</sup> K<sup>-1</sup>, for SiC and Si<sub>3</sub>N<sub>4</sub>, respectively.</p><p>II. Monolithic metallic Co(0) aerogels, synthesized from polyurea-crosslinked cobaltia xerogel powder compacts, were porous (69% v/v) and extremely sturdy (compressive modulus at 688 ± 10 MPa). They were infiltrated with molten LiClO<sub>4</sub>, and were ignited with a hot NiCr wire. The temperature during combustion reached 1515 °C. The heat released (-55.17 ± 2.01 kcal mol<sup>-1</sup>) was near the theoretical value for the reaction: 4 Co + LiClO<sub>4</sub> ----> 4 CoO + LiCl (-58.5 kcal mol<sup>-1</sup>).</p><p>III. Polyurethane (PU) aerogels are low-density hierarchical nano-structured solids with high open nanoporosity, and high surface areas. Using α- and β-cyclodextrin (CD) as polyols, an aromatic triisocyanate and dibutyltin dilaurate (DBTDL) as a catalyst we obtained hyperbranched CD-based polyurethane aerogels (α- and β-CDPU-xx). Those materials show high water uptake capacities (108% w/w with α-CDPU-2.5) and can be reused multiple times by regeneration at room temperature by changing the relative humidity of the environment"--Abstract, page v.</p><p>
Degree
thesis:*- Name thesis:degree_name
- Ph. D. in Chemistry
- Grantor
- Missouri University of Science and Technology
Author and committee
dc:creator, dc:contributor.*- Author dc:creator
-
- Rewatkar, Parwani M.
Subjects
dc:subject × 8Identifiers
dc:identifier.*- Repository record dc:identifier
- https://scholarsmine.mst.edu/doctoral_dissertations/2811
- OAI identifier oai:identifier
- oai:scholarsmine.mst.edu:doctoral_dissertations-3816