"Silica aerogels are three-dimensional assemblies of silica nanoparticles with extremely low densities. In some instances, the internal void volume is more than 90% of the total volume. The highly porous structure of the aerogels leads to attractive properties for thermal and noise insulation, due to very low thermal conductivity and very high acoustic impedance. The strength of silica aerogels has been substantially improved by casting a thin conformal polymer coating over the entire internal porous surfaces of the nanostructure. The coating reinforces the interparticle connections without significantly compromising the internal void space. To analyze and compare the properties of several lightweight polymer-crosslinked silica aerogels, spatially resolved T₁ and T₂ relaxation studies were conducted. The polymer-crosslinked aerogels were precision-machined to snugly fit into the lower parts of standard NMR tubes. A mixture of equal amounts of acetone and deuterated acetone was used as the liquid to fill the void volume of the aerogels. Spin-echo and saturation-recovery relaxation sequences were used as part of a standard one-dimensional gradient-recalled echo imaging sequence. For comparison, native aerogels without the polymer coating were examined with the same pulse sequences. Because of the fragile nanoparticle network, native gels could not be machined but were generated directly inside the NMR tubes. The porosity of the gels was determined using the relaxation profiles. The relaxation times were found to have a significant dependence on the coating polymer and also on the formation process of the aerogels. In addition, the relationship between the pore size and relaxation time was also analyzed"--Abstract, page iii.
Schuman, Thomas P.
M.S. in Chemistry
National Science Foundation (U.S.)
Missouri University of Science and Technology. Department of Chemistry
Missouri University of Science and Technology
ix, 79 pages
© 2011 EmmaLou Theresa Satterfield, All rights reserved.
Thesis - Open Access
Library of Congress Subject Headings
Nuclear magnetic resonance
Relaxation (Nuclear physics)
Print OCLC #
Electronic OCLC #
Link to Catalog Record
Satterfield, Emmalou T., "Relaxation imaging to characterize lightweight polymer-crosslinked aerogels" (2011). Masters Theses. 7143.