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Molecules 2018, 23(7), 1522; https://doi.org/10.3390/molecules23071522

Thermal Failure Analysis of Fiber-Reinforced Silica Aerogels under Liquid Nitrogen Thermal Shock

1,2,†,* , 1,2,†
,
3,†
,
4
and
1,2,*
1
Shanghai Key Laboratory of Special Artificial Microstructure Materials and Technology, Tongji University, Shanghai 200092, China
2
School of Physics Science and Engineering, Tongji University, Shanghai 200092, China
3
Key Laboratory of Graphene Technologies and Applications of Zhejiang Province, Ningbo Institute of Materials Technology & Engineering (NIMTE), Chinese Academy of Science, Ningbo 315201, China
4
Laboratory of Space Mechanical and Thermal Integrative Technology, Shanghai Institute of Satellite Engineering, Shanghai 200240, China
These authors contributed equally to this work.
*
Authors to whom correspondence should be addressed.
Received: 9 May 2018 / Revised: 9 June 2018 / Accepted: 15 June 2018 / Published: 24 June 2018
(This article belongs to the Special Issue Chemistry of Aerogels and Their Applications)
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Abstract

Aerogel materials are recognized as promising candidates for the thermal insulator and have achieved great successes for the aerospace applications. However, the harsh environment on the exoplanet, especially for the tremendous temperature difference, tends to affect the tenuous skeleton and performances of the aerogels. In this paper, an evaluation method was proposed to simulate the environment of exoplanet and study the influence on the fiber-reinforced silica aerogels with different supercritical point drying (SPD) technology. Thermal conductivity, mechanical property and the microstructure were characterized for understanding the thermal failure mechanism. It was found that structure and thermal property were significantly influenced by the adsorbed water in the aerogels under the thermal shocks. The thermal conductivity of CO2-SPD aerogel increased 35.5% after the first shock and kept in a high value, while that of the ethanol-SPD aerogel increased only 19.5% and kept in a relatively low value. Pore size distribution results showed that after the first shock the peak pore size of the CO2-SPD aerogel increased from 18 nm to 25 nm due to the shrinkage of the skeleton, while the peak pore size of the ethanol-SPD aerogel kept at ~9 nm probably induced by the spring-back effect. An 80 °C treatment under vacuum was demonstrated to be an effective way for retaining the good performance of ethanol-SPD aerogels under the thermal shock. The thermal conductivity increases of the ethanol-SPD aerogels after 5 shocks decreased from ~30 to ~0% via vacuum drying, while the increase of the CO2-SPD aerogels via the same treatments remains ~28%. The high-strain hardening and low-strain soften behaviors further demonstrated the skeleton shrinkage of the CO2-SPD aerogel. View Full-Text
Keywords: thermal shock; fiber-reinforced aerogel; hydrophilic; hydrophobic thermal shock; fiber-reinforced aerogel; hydrophilic; hydrophobic
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Du, A.; Liu, M.; Huang, S.; Li, C.; Zhou, B. Thermal Failure Analysis of Fiber-Reinforced Silica Aerogels under Liquid Nitrogen Thermal Shock. Molecules 2018, 23, 1522.

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