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The control of porosity at nano scale in resorcinol formaldehyde carbon aerogels

Mirzaeian, Mojtaba and Hall, Peter J. (2009) The control of porosity at nano scale in resorcinol formaldehyde carbon aerogels. Journal of Materials Science, 44 (10). pp. 2705-2713. ISSN 0022-2461

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Abstract

Organic aerogels were synthesized by sol-gel polymerization of resorcinol (R) with formaldehyde (F) catalyzed by sodium carbonate (C) followed by vacuum drying. The influence of the resorcinol/sodium carbonate ratio (R/C) on the porous structure of the resultant aerogels was investigated. The nitrogen adsorption-desorption measurements show that the aerogels possess a well developed porous structure and mesoporosity was found to increase with increasing the R/C ratio. Carbon aerogels were obtained by carbonization of RF aerogels. The carbonization temperature impacts the microstructure of the aerogels by pore transformations during carbonization probably due to the formation of micropores and shrinkage of the gel structure. The results showed that a temperature of 1073 K is more effective in the development of the pore structure of the gel. Activated carbon aerogels were obtained from the CO2 activation of carbon aerogels. Activation results in an increase in the number of both micropores and mesopores, indicative of pore creation in the structure of the carbon. Activation at higher temperatures results in a higher degree of burn off and increases the pore volume and the surface area remarkably without change of the basic porous structure, pore size, and pore size distribution. separation [1, 2], electrode materials for energy storage [3-5], catalyst supports [6], packing materials for chromatography [7], host materials for gas storage[8], thermal and/or phonic insulators [9, 10], etc. For many advanced applications such as double layer supercapacitors the control of porosity at nano-level is very essential. Resorcinol formaldehyde (RF) aerogels are special type of highly cross-linked aromatic polymers with a high pore volume (0.25-1.25 cm3/g) [11], low density (0.06-0.103 g/cm3) [12], large specific surface area (400-1000 m2/g) [13], and mostly amorphous structure [14]. The morphology of RF aerogels can be modified as a function of different synthesis parameters. This characteristic allows the tailoring of the internal structure of these porous materials on a nanometer scale and makes them particularly well suited for a variety of applications. RF aerogels can be used as precursors for the preparation of porous carbons with similar appearance and macrostructure, but having slight differences in microstructure.