Acta Phys. -Chim. Sin. ›› 2012, Vol. 28 ›› Issue (05): 1189-1196.doi: 10.3866/PKU.WHXB201202292

• SOFT MATTER • Previous Articles     Next Articles

Thermal and Mechanical Properties of Density-Gradient Aerogels for Outer-Space Hypervelocity Particle Capture

DU Ai, ZHOU Bin, GUI Jia-Yin, LIU Guang-Wu, LI Yu-Nong, WU Guang-Ming, SHEN Jun, ZHANG Zhi-Hua   

  1. Shanghai Key Laboratory of Special Artificial Microstructure Materials and Technology, Tongji University, Shanghai 200092, P. R. China
  • Received:2011-11-21 Revised:2012-02-07 Published:2012-04-26
  • Contact: ZHOU Bin
  • Supported by:

    The project was supported by the National Natural Science Foundation of China (51102184, 51172163), National High Technology Research and Development Program of China, National Key Technology Research and Development Program of China (2009BAC62B02), Program for Young Excellent Tatents in Tongji University (2010KJ068), and Doctoral Fund of Ministry of Education of China (20090072110047, 20100072110054).

Abstract: Aerogels with densities in the range 40-175 mg·cm-3 were prepared using a tetraethyl orthosilicate (TEOS) ethanol-water solution as the precursor and hydrofluoric acid as the catalyst via a sol-gel process and CO2 supercritical-fluid drying. The density-gradient aerogels were prepared using layer-by-layer gelation, sol co-gelation, and gradient-sol co-gelation methods and their gradient properties were studied systematically. The results show that aerogels with different densities all have a threedimensional skeleton consisting of spherical particles of diameter about 40-90 nm. The lower the density is, the looser the skeleton and pore-size distributions are, and the larger the peak value of the pore size is. Gradient aerogels prepared via different methods exhibited graded, approximately gradient, or gradient distributions. Dynamic mechanical analysis indicates that the Young's moduli of the aerogels at -100 and 25 °C (changed from 4.6×105 to 1.9×105 Pa and from 5.0×105 to 2.1×105 Pa, respectively) tend to decrease with decreasing density. Thermal constants analysis shows that as the densities of the aerogels decrease, the thermal diffusion coefficients increase and the specific heat capacities decrease, but the thermal conductivities do not change monotonically.

Key words: Gradient, Aerogel, Thermal, Mechanics, Thermal conductivity, Modulus, Low temperature


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