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. 2021 Aug 14;7(3):122.
doi: 10.3390/gels7030122.

Alumina-Doped Silica Aerogels for High-Temperature Thermal Insulation

Yu Wu  1 , Xiaodong Wang  1 , Lin Liu  1 , Ze Zhang  1 , Jun Shen  1
Affiliations

Alumina-Doped Silica Aerogels for High-Temperature Thermal Insulation

Yu Wu et al. Gels. .

Abstract

In this study, we used two methods to prepare alumina-doped silica aerogels with the aim of increasing the thermal stability of silica aerogels. The first method was physical doping of α-Al2O3 nano powders, and the second method was to create a chemical compound via the co-precursor of TEOS and AlCl3·6H2O in different proportions. The shrinkage, chemical composition, and specific surface area (SSA) of samples after heating at different temperatures were analyzed. Our results show that the silicon hydroxyl groups of samples derived from AlCl3·6H2O gradually decreased and nearly disappeared after heating at 800 °C, which indicates the complete dehydration of the silicon hydroxyl. Thus, the samples exhibited a large linear shrinkage and decreased SSA after high-temperature heat treatment. By contrast, samples doped with α-Al2O3 powders retained abundant silicon hydroxyl groups, and the 6.1 wt.% α-Al2O3-doped sample exhibited the lowest linear shrinkage of 11% and the highest SSA of 1056 m2/g after heat treatment at 800 °C. The alumina-doped silica aerogels prepared using a simple and low-price synthesized method pave the way for the low-cost and large-scale production of high-temperature thermal insulation.

Keywords: alumina-doped; high temperature resistance; silica aerogels; thermal stability.

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Conflict of interest statement

The authors declare no conflict of interest.

Figures

Figure 1
Figure 1
Photos of alumina-doped silica aerogels formed with different precursors and proportions without heat treatment (AL and AO represent the samples derived from AlCl3·6H2O and α-Al2O3 powders, respectively. The numbers denote the molar percentage of Al/(Al+Si)).
Figure 2
Figure 2
Photos of alumina-doped silica aerogels after heat treatment at 1000 °C (AL and AO represent the samples derived from AlCl3·6H2O and α-Al2O3 powders, respectively. The numbers denote the molar percentage of Al/(Al+Si)).
Figure 3
Figure 3
Scanning electron microscopy (SEM) images of sample AL7 after heat treatment from 300 to 900 °C: (a) AL7-300, (b) AL7-500, (c) AL7-700 and (d) AL7-900 (EHT: extra high tension, MAG: magnification, SE: secondary electrons, WD: work distance).
Figure 4
Figure 4
Scanning electron microscopy (SEM) images of AO7 sample after heat treatment from 300 to 900 °C: (a) AO7-300, (b) AO7-500, (c) AO7-700 and (d) AO7-900 (EHT: extra high tension, MAG: magnification, SE: secondary electrons, WD: work distance).
Figure 5
Figure 5
The linear shrinkage of (a) AL samples and (b) AO samples after heat treatments from 300 to 1000 °C (AL and AO represent the samples derived from AlCl3·6H2O and α-Al2O3 powders, respectively. The numbers denote the molar percentage of Al/(Al+Si)).
Figure 6
Figure 6
FTIR spectra of the (a) AL4 after heat treatment from 300 to 1000 °C, and FTIR spectra of the (b) AO and AL samples after heat treatment at 800 °C (AL and AO represent the samples derived from AlCl3·6H2O and α-Al2O3 powders, respectively. The numbers denote the molar percentage of Al/(Al+Si)).
Figure 7
Figure 7
XRD patterns of (a) AO and (b) AL samples after heat treatment at 800 °C (AL and AO represent the samples derived from AlCl3·6H2O and α-Al2O3 powders, respectively. The numbers denote the molar percentage of Al/(Al+Si)).
Figure 8
Figure 8
(a) Desorption isotherms and (b) pore size distribution of sample AL4 after heat treatment from 300 to 1000 °C.
Figure 9
Figure 9
(a) Specific surface area (SSA) variation and (b) average pore diameter of sample AL4 with heat treatment from 300 to 1000 °C.
Figure 10
Figure 10
Desorption isotherms and pore size distribution of the (a,b) AL samples and (c,d) AO samples after heat treatment at 800 °C (AL and AO represent the samples derived from AlCl3·6H2O and α-Al2O3 powders, respectively. The numbers denote the molar percentage of Al/(Al+Si)).
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