Keywords and Phrases
Aerogels; Ceramic; Cobalt; Cross-linked polymer; Cyclodextrin polyurethane; Porous polymers
"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.
I. Highly porous ( > 80%) monolithic SiC and Si3N4, 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 0.163 ± 0.010 W m-1 K-1 and 0.070 ± 0.001 W m-1 K-1, for SiC and Si3N4, respectively.
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 LiClO4, and were ignited with a hot NiCr wire. The temperature during combustion reached 1515 °C. The heat released (-55.17 ± 2.01 kcal mol-1) was near the theoretical value for the reaction: 4 Co + LiClO4 ----> 4 CoO + LiCl (-58.5 kcal mol-1).
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.
Winiarz, Jeffrey G.
Rownaghi, Ali A.
Ph. D. in Chemistry
United States. Army Research Office
National Science Foundation (U.S.)
Missouri University of Science and Technology
Journal article titles appearing in thesis/dissertation
- Sturdy, monolithic SiC and Si3N4 aerogels from compressed polymer-crosslinked silica xerogel powders
- A cobalt sunrise: Thermites based on LiClO4-filled Co(0) aerogels prepared from polymer-crosslinked cobaltia xerogel powders
- Polyurethane aerogels based on cyclodextrins: High capacity desiccants regenerated at room temperature by reducing the relative humidity of the environment
xxi, 185 pages
© 2019 Parwani M. Rewatkar, All rights reserved.
Dissertation - Open Access
Electronic OCLC #
Rewatkar, Parwani M., "Synthesis and applications of ceramic (silicon carbide and silicon nitride), metallic (cobalt(0)) and polymeric (polyurethane) aerogels" (2019). Doctoral Dissertations. 2811.