Constructing secondary-pore structure by in-situ synthesized mullite whiskers to prepare whiskers aerogels with ultralow thermal conductivity |
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Authors: | Hangyuan Zhao Xiaolei Li Huiming Ji Huijun Yu Bo Yu Te Qi |
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Affiliation: | Key Laboratory of Advanced Ceramics and Machining Technology of Ministry of Education, School of Materials Science and Engineering of Tianjin University, Tianjin 300072, PR China |
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Abstract: | Ultralow thermal conductivity and ultralight mullite fibers/mullite whiskers composite aerogels (MF/MW) with secondary-pore structure have been prepared via vacuum impregnation and high-temperature treatment. The in-situ generation of mullite whiskers during vapour-solid reaction process and the mechanism of improving thermal stability have been discussed in detail. Under catalysis condition at 1200 °C, the zero-dimensional nanoparticles of SiO2-Al2O3 aerogels are guided to in-situ transform into one-dimensional mullite whiskers. The secondary-pore structure formed by the overlapped fibers and whiskers in MF/MW reduces the thermal conductivity [as low as 0.0488 W/m?1 K?1 compared with that of MF preform (0.0698 W/m?1 K?1)] and exhibits excellent thermal stability after 1400 °C heat treatment (0.0503 W/m?1 K?1) due to the macropores are decreased and gaseous heat transfer being further weakened effectively. Moreover, the MF/MW exhibits good mechanical performance with high critical compressive stress of 0.2809 MPa, which is more than 317% higher than that of MF preform (0.0673 MPa) at room temperature. |
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Keywords: | Corresponding authors. Aerogels Mullite whiskers Secondary-pore structure Vapour-solid reaction Thermal stability |
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