Tailoring of Boehmite-Derived Aluminosilicate Aerogel Structure and Properties: Influence of Ti Addition

Abstract

Aluminosilicate aerogels offer potential for extremely low thermal conductivities at temperatures greater than 900˚C, beyond where silica aerogels reach their upper temperature limits. Aerogels have been synthesized at various Al:Si ratios, including mullite compositions, using Boehmite (AlOOH) as the Al source, and tetraethoxy orthosilicate as the Si precursor. The Boehmite-derived aerogels are found to form by a self-assembly process of AlOOH crystallites, with Si-O groups on the surface of an alumina skeleton. Morphology, surface area and pore size varies with the crystallite size of the starting Boehmite powder, as well as with synthesis parameters.Ternary systems, including Al-Si-Ti aerogels incorporating a soluble Ti precursor, are possible with careful control of pH. The addition of Ti influences sol viscosity, gelation time pore structure and pore size distribution, as well as phase formation on heat treatment.

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

“…In both routes, tetraethoxysilane (TEOS) is used as the silicon source. In a preliminary study, 22 use of soluble precursors has been shown to favor gel networks with significant Al-O-Si tetrahedral bonding, while the colloidal approach primarily maintains the AlO 6 octahedral structure characteristic of boehmite. 23,24 Studies of the Al 2 O 3 -SiO 2 system conducted by Roy and Komarneni et al have shown variation in sintering behavior based on the presence of diphasic versus single-phase systems [25][26][27] .…”

Investigation of Insulation Materials for Future Radioisotope Power Systems (RPS)

“…Hence, polymeric aerogels are limited by the decomposition temperature of the particular polymer (> insulating. The group at NASA Glenn Research Center has developed aluminosilicate aerogels which maintain high surface areas and mesoporous structures to temperatures of 1100reaction of boehmite and tetraethyl orthosilicate (TEOS), in which the surface area and pore structure can be controlled by the choice of boehmite precursor and the synthesis parameters 6,7 . The aluminosilicate aerogels in the present study utilize an aluminum to silicon ratio of 3 to 1, the ratio found in mullite.…”