"Pyrolysis at 800 ºC under argon has shown that polyimide (PI), polyacrylonitrile (PAN), polydicyclopentadiene (DCPD) and polybenzoxazine (PBO) aerogels are all viable alternatives to traditional resorcinol-formaldehyde (RF) aerogels as precursors to amorphous carbon aerogels. Subsequent high temperature pyrolysis at 2300 ºC of such carbon aerogels under helium has shown that amorphous carbon from PI and PBO yields the highest degree of graphitization, whereas from RF aerogels yields the lowest.
Those two types of graphite aerogels include also a high concentration of micron-size columnar and helical (screw-like) structures, whose formation is favored by macroporosity and high nitrogen retention in the 800 ºC-carbonized samples. Control experiments were conducted with corannulene and bromo-corannulene in order to integrate cyclopentyl rings on surfaces of activated carbon, PBO-derived carbon aerogels, and carbon black. In most cases the concentration of rod and helical structures increased dramatically (over 50%).
An idealized growth model was formulated for the formation of the rods and screw-like structures, whereas rapid grain growth leads to the formation of cyclopentyl rings and disclinations in the graphitic network. Trivalent nitrogen, when present, assists in the developed of cyclopentyl rings and subsequent growth of the columnar carbon structures."--Abstract, page iv.
Whitefield, Philip D.
Winiarz, Jeffrey G.
Miller, F. Scott, 1956-
Ph. D. in Chemistry
Missouri University of Science and Technology
xxii, 308 pages
© 2014 Clarissa Ann Wisner, All rights reserved.
Dissertation - Open Access
Electronic OCLC #
Wisner, Clarissa Ann, "Graphite aerogels and the formation mechanism of unusual micron-sized rod and helical structures" (2014). Doctoral Dissertations. 2181.