"Ultra-low density, three-dimensional assemblies of nanoparticles are referred to as aerogels, and typically are derived from supercritical fluid (SCF) drying of wet-gels. Aerogels are generally fragile materials, but that issue has been addressed successfully by X-aerogels, in which the inorganic nanoparticle framework plays the role of the template for the accumulation of polymer that connects covalently and crosslinks the nanoparticles. The resulting materials can be 300x stronger than the native network, for a nominal increase in density by a factor of 3x. Since the exceptional mechanical properties of X-aerogels are traced to the conformal polymer coating, it was reasonable to seek organic aerogels of the crosslinker itself. Thus, here we demonstrate a new efficient method for the synthesis of polyurea (PUA) aerogels by reaction of di or triisocyanates with controlled amounts of water, resulting in in-situ amine formation, which reacts further with yet-unreacted isocyanate to form polyurea. PUA aerogels prepared by this method have variable nanomorphology (from fibrous to particulate, depending on the chemical identity and the concentration of the monomer), extremely high mechanical strength and they are flame retardant.
Smelting dates to 3000 B.C. and is used to produce metal from the ore via chemical reduction with carbon. Carbon aerogels are produced by pyrolysis of purely organic resorcinol-formaldehyde (RF) aerogels. Here we have developed interpenetrating networks of RF and metal oxide (MOx) aerogels that upon pyrolysis undergo smelting yielding metal, or carbide aerogels, depending on the chemical identity of M: oxides of Fe, Co, Ni, Sn, Cu yield metal aerogels, refractory Cr, Ti, Hf oxides yield carbides. By casting a conformal polymer coating on the RF-MOx interpenetrating nanoparticle networks, or by controlling the drying process and thus the compactness of the network"--Abstract, page iv.
Winiarz, Jeffrey G.
Kakkatukuzhy, Isaac M.
Ph. D. in Chemistry
Missouri University of Science and Technology
Journal article titles appearing in thesis/dissertation
- Multifunctional polyurea aerogels from isocyanates and water: a structure-property case study
- Smelting in the age of nano: iron aerogels
- One-pot synthesis of interpenetrating inorganic/organic networks of Cuo/resorcinal-formaldehyde aerogels: nanostructured energetic materials
- Effect of compactness on the carbothermal conversion of intepenetrating metal oxide/resourcinol-formaldehyde nanoparticle networks to porous metal and carbides
xvii, 204 pages
© 2011 Naveen K. Chandrasekaran, All rights reserved.
Dissertation - Restricted Access
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Chandrasekaran, Naveen K., "One pot synthesis of metal, carbides and polymeric aerogels" (2011). Doctoral Dissertations. 1801.