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Journal of Sol-Gel Science and Technology

, Volume 59, Issue 2, pp 371–380 | Cite as

Shrinkage and pore structure in preparation of carbon aerogels

  • Junzong Feng
  • Jian Feng
  • Changrui Zhang
Original paper

Abstract

To aim at thermal insulator applications, the shrinkage and the pore structure of resorcinol–formaldehyde (RF) aerogels and carbon aerogels were investigated during the supercritical drying and the carbonization process. The water (W) molar ratio has small effects on the surface area or the particle size, but has significant effects on the density of the aerogel. Higher W/R ratio leads to lower density and larger pore size, and leads to less shrinkage during the carbonization process. The molar ratio of catalyst sodium carbonate (C) has significant effects on the shrinkage, pore size, and particle size of the aerogel. Lower R/C ratio leads to smaller particle size and smaller pore size, and thus induces more shrinkage both in the supercritical drying and in the carbonization, the obtained CA is much denser. The R/C ratio should be higher than 300 to prevent excessive shrinkage. In order to synthesize carbon aerogels combining with small shrinkage, low density (less than 0.1 g/cm3), and small pore size (less than 150 nm) for thermal insulators, the preferred W/R ratio is between 90 and 100, and the preferred R/C ratio is between 300 and 600.

Keywords

Carbon aerogels Supercritical drying Linear shrinkage Pore size 

Notes

Acknowledgments

The authors gratefully acknowledge financial supports from National Natural Science Foundation (51002187) and National Defense Preliminary Research Foundation (9140C8203051003) of China. Dr. Yonggang Jiang is thanked for helpful discussions and comments. The authors would also like to thank Xiang Zhang for the SEM measurements, and Jirong Ling for the nitrogen sorption measurements.

Supplementary material

10971_2011_2514_MOESM1_ESM.doc (1.2 mb)
Supplementary material 1 (DOC 1187 kb)

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Copyright information

© Springer Science+Business Media, LLC 2011

Authors and Affiliations

  1. 1.Key Lab of Advanced Ceramic Fibers and Composites, College of Aerospace and Materials EngineeringNational University of Defense TechnologyChangshaChina

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