Optimization of Alumina and Aluminosilicate Aerogel Structure for High‐Temperature Performance

Abstract

Alumina and aluminosilicate aerogels offer potential for use at temperatures above 700°C, where silica aerogels begin to sinter. Stability of alumina and aluminosilicate pore structures at high temperatures is governed by the starting aerogel structure, which, in turn is controlled by the synthesis route. Structure, morphology, and crystallization behavior are compared for aerogels synthesized from AlCl 3 and propylene oxide with those synthesized from a variety of boehmite precursors. The aerogels possessing a crystalline boehmite structure in the as-synthesized condition retained mesoporous structures to temperatures of 1200°C, while the AlCl 3 -derived aerogels, although exhibiting higher as-synthesized surface areas, crystallized and densified at 980-1005°C.

Phase development and pore stability of yttria‐ and ytterbia‐stabilized zirconia aerogels

“…Prior investigations of alumina and aluminosilicate systems have shown the potential for stabilizing a mesoporous aerogel structure to temperatures of 1100°C‐1200°C 16,17 . The current study investigates the synthesis of yttrium, ytterbium, and co‐doped zirconia aerogels and the influence of phase stability in maintaining a porous microstructure.…”

Synthesis of a novel Al2O3–SiO2 composite aerogel with high specific surface area at elevated temperatures using inexpensive inorganic salt of aluminum

“…At a temperature of 1000 1C, a small amount of large pores with diameters greater than 200 nm emerge in the composite, which stems from the densification and sintering of γ-Al 2 O 3 particles. As the temperature is increased to 1200 1C, the uniform agglomerated structures primarily contain mullite with small amounts of γ-Al 2 O 3 particles, which is probably caused by the growth of mullite grains [11,25]. However, the SEM images reveal that the resulting composite aerogel after heat treatment at 1200 1C presents disordered, porous structures of a typical colloidal gel, and that nanoparticles are uniformly distributed to form a framework surrounded with irregular pores [26,27].…”

“…Because the formed mono-hydroxide is the only material that can be peptized to a clear sol, a highly complex procedure is needed to obtain a clear solution [8][9][10]. Hurwitz et al [11] directly employed boehmite powder as an alumina source to prepare Al 2 O 3 -SiO 2 aerogel. The specific surface area was as high as 33 m 2 /g at 1300 1C, whereas the phase transition of γ-Al 2 O 3 / η-Al 2 O 3 occurred as early as 600 1C.…”

Synthesis of fibre reinforced Al2O3−SiO2 aerogel composite with high density uniformity via a facile high-pressure impregnation approach

“…Fibre reinforced silica aerogel composite, with low thermal conductivity and high mechanical performance, expands its uses especially as an excellent thermal insulation material [1][2][3][4][5][6][7][8][9][10][11]. However, alumina-silica (Al 2 O 3 −SiO 2 ) aerogel, with high specific surface area, high porosity and high temperature stability [12][13][14][15][16][17], is attracting more increased interest in the field of thermal insulation application [18][19][20][21][22][23][24][25] at elevated temperature. As with SiO 2 aerogel, the Al 2 O 3 −SiO 2 aerogel is fragile and difficult to use directly.…”