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Structural Evolution in Carbon Aerogels as a function of Precursor Material and Pyrolysis Temperature

Published online by Cambridge University Press:  10 February 2011

J. Gross ,
C. T. Alviso  and
R. W. Pekala
J. Gross
Affiliation:
Chemistry & Materials Science Department, Lawrence Livermore National Laboratory, Livermore, CA 94550
C. T. Alviso
Affiliation:
Chemistry & Materials Science Department, Lawrence Livermore National Laboratory, Livermore, CA 94550
R. W. Pekala
Affiliation:
Chemistry & Materials Science Department, Lawrence Livermore National Laboratory, Livermore, CA 94550
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Abstract

Several organic reactions that proceed through a sol-gel transition have been identified at LLNL. The most-studied reaction involves the aqueous polycondensation of resorcinol (1,3- dihydroxybenzene) with formaldehyde. Recently, we have shown that phenol can be added to this polymerization as a comonomer. The resultant crosslinked gels are supercritically dried from carbon dioxide (Tc=31°C, Pc = 7.4 MPa) to give resorcinol-phenol-formaldehyde (RPF) aerogels. Because RPF aerogels are composed of a highly crosslinked aromatic polymer, they can be pyrolyzed in an inert atmosphere to form vitreous carbon monoliths (CRPF). The resultant aerogels are black in color and no longer transparent, yet they retain the high porosity (40–98 %), ultrafine cell/pore size (< 50 nm), high surface area (600–800 m2/g), and interconnected particle (˜10 nm) morphology of their organic precursors. In this study, we examine the acoustic and mechanical properties of these materials as a function of precursor material and pyrolysis temperature. It is shown that the elastic moduli of RPF and CRPF is higher than that of pure RF / CRF aerogels at a given density. Upon pyrolysis RPF aerogels tend to shrink to a larger extent.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 431: Symposium P – Microporous and Macroporous Materials , 1996 , 123
Copyright
Copyright © Materials Research Society 1996

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References

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