Alumina-Doped Silica Aerogels for High-Temperature Thermal Insulation

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.

Ice-Template Crosslinked PVA Aerogels Modified with Tannic Acid and Sodium Alginate

“…As can be observed, after incorporating SA and TA into the aerogel matrix, the apparent densities increased around two-fold compared to the P5 reference. This increment was, to some extent, expected since SA (1.695 g/cm 3 ) and TA (1.560 g/cm 3 ) powder densities are higher than that of PVA (1.281 g/cm 3 ). However, the main reason for the change in density was associated with the higher number of solids in the precursor solutions of the modified aerogels.…”

“…The aerogel moisture absorption can be minimized by applying a hydrophobic coating to the aerogel surfaces [34,35]. In the uncrosslinked aerogels, pure PVA (P5 sample) showed the lowest values (λ = 0.030 W/m•K) and the lowest apparent density (ρ app = 0.075 ± 0.005 g/cm 3 ), whereas P5T3A3 presented the highest conductivity (λ = 0.046 W/m•K) as well as the highest density (ρ app = 0.144 ± 0.009 g/cm 3 ). Despite the density dependence, the large difference between pure PVA and the aerogel blends is attributed to the hydrogen bond interactions between the components (PVA, TA, SA) that can create a continuous thermal network, increasing heat transfer [36].…”

“…Aerogels are ultra-light, highly porous materials characterized by a large specific surface area, which makes them excellent candidates for absorbing media [ 1 ], energy storage [ 2 ], or thermal insulation applications [ 3 ]. Among the different types, inorganic silica aerogels are probably the most studied.…”

Looking for an Optimal Composition of Nickel-Based Catalysts for CO2 Methanation

“…As it is well known, amorphous silicas are largely covalent supports [45] which are usually supposed to be essentially non-dispersive with respect to other more ionic materials. Depending on the preparation method and type of materials, amorphous silicas have high morphological stability towards sintering and loss of surface area up to 873 K or more [46,47]. Silica is active in reversible adsorption, including of CO 2 , with an important role of surface silanol groups as hydrogen bond donors [48], but without any Lewis acidity and basicity [49].…”

Robust SiO2–Al2O3/Agarose Composite Aerogel Beads with Outstanding Thermal Insulation Based on Coal Gangue

“…As a distinctive type of aerogel, SiO 2 –Al 2 O 3 composite aerogel has better thermal stability than native SiO 2 aerogels, which could make it suitable for use in aircraft [ 12 , 13 ]. Moreover, its unique three-dimensional network and nanoporous structure decreases heat conduction, so the thermal conductivity of the SiO 2 –Al 2 O 3 aerogel is extremely low, allowing it to be used in insulation materials [ 14 , 15 ].…”