Results for “Al-Si-Ti” | Engineering Papers

NASA NTRS2010

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

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.

Hurwitz, Frances I.↗

DOE OSTI2020

Materials Data on Ti20(AlSi3)3 by Materials Project

Ti20(AlSi3)3 crystallizes in the monoclinic Pm space group. The structure is three-dimensional. there are sixteen inequivalent Ti sites. In the first Ti site, Ti is bonded in a 8-coordinate geometry to two equivalent Ti, two Al, and four Si atoms. There are one shorter (2.55 Å) and one longer (2.62 Å) Ti–Ti bond lengths. Both Ti–Al bond lengths are 2.69 Å. There are a spread of Ti–Si bond distances ranging from 2.63–2.67 Å. In the second Ti site, Ti is bonded in a 8-coordinate geometry to two equivalent Ti, one Al, and five Si atoms. There are one shorter (2.57 Å) and one longer (2.60 Å) Ti–Ti bond lengths. The Ti–Al bond length is 2.69 Å. There are a spread of Ti–Si bond distances ranging from 2.64–2.68 Å. In the third Ti site, Ti is bonded in a 8-coordinate geometry to two equivalent Ti, two Al, and four Si atoms. There are one shorter (2.55 Å) and one longer (2.62 Å) Ti–Ti bond lengths. There are one shorter (2.68 Å) and one longer (2.69 Å) Ti–Al bond lengths. There are a spread of Ti–Si bond distances ranging from 2.63–2.69 Å. In the fourth Ti site, Ti is bonded in a 8-coordinate geometry to two equivalent Ti, one Al, and five Si atoms. There are one shorter (2.57 Å) and one longer (2.60 Å) Ti–Ti bond lengths. The Ti–Al bond length is 2.69 Å. There are a spread of Ti–Si bond distances ranging from 2.63–2.66 Å. In the fifth Ti site, Ti is bonded in a 5-coordinate geometry to one Al and four Si atoms. The Ti–Al bond length is 2.75 Å. There are a spread of Ti–Si bond distances ranging from 2.57–2.82 Å. In the sixth Ti site, Ti is bonded in a 5-coordinate geometry to two Al and three Si atoms. There are one shorter (2.65 Å) and one longer (2.74 Å) Ti–Al bond lengths. There are one shorter (2.56 Å) and two longer (2.82 Å) Ti–Si bond lengths. In the seventh Ti site, Ti is bonded in a 5-coordinate geometry to two Al and three Si atoms. There are one shorter (2.63 Å) and one longer (2.74 Å) Ti–Al bond lengths. There are one shorter (2.55 Å) and two longer (2.83 Å) Ti–Si bond lengths. In the eighth Ti site, Ti is bonded in a 5-coordinate geometry to one Al and four Si atoms. The Ti–Al bond length is 2.64 Å. There are a spread of Ti–Si bond distances ranging from 2.56–2.79 Å. In the ninth Ti site, Ti is bonded in a 5-coordinate geometry to two Al and three Si atoms. Both Ti–Al bond lengths are 2.62 Å. There are one shorter (2.70 Å) and two longer (2.79 Å) Ti–Si bond lengths. In the tenth Ti site, Ti is bonded in a 5-coordinate geometry to one Al and four Si atoms. The Ti–Al bond length is 2.63 Å. There are a spread of Ti–Si bond distances ranging from 2.56–2.80 Å. In the eleventh Ti site, Ti is bonded in a 5-coordinate geometry to two equivalent Al and three Si atoms. Both Ti–Al bond lengths are 2.81 Å. There are a spread of Ti–Si bond distances ranging from 2.56–2.73 Å. In the twelfth Ti site, Ti is bonded in a 5-coordinate geometry to two equivalent Al and three Si atoms. Both Ti–Al bond lengths are 2.82 Å. There are a spread of Ti–Si bond distances ranging from 2.56–2.73 Å. In the thirteenth Ti site, Ti is bonded in a 3-coordinate geometry to two equivalent Al and three Si atoms. Both Ti–Al bond lengths are 2.83 Å. There are a spread of Ti–Si bond distances ranging from 2.57–2.72 Å. In the fourteenth Ti site, Ti is bonded in a 5-coordinate geometry to five Si atoms. There are a spread of Ti–Si bond distances ranging from 2.59–2.80 Å. In the fifteenth Ti site, Ti is bonded in a 5-coordinate geometry to five Si atoms. There are a spread of Ti–Si bond distances ranging from 2.61–2.80 Å. In the sixteenth Ti site, Ti is bonded in a 5-coordinate geometry to five Si atoms. There are a spread of Ti–Si bond distances ranging from 2.60–2.80 Å. There are three inequivalent Al sites. In the first Al site, Al is bonded in a 9-coordinate geometry to nine Ti atoms. In the second Al site, Al is bonded in a 9-coordinate geometry to nine Ti atoms. In the third Al site, Al is bonded in a 11-coordinate geometry to nine Ti atoms. There are nine inequivalent Si sites. In the first Si site, Si is bonded in a 9-coordinate geometry to nine Ti atoms. In the second Si site, Si is bonded in a 9-coordinate geometry to nine Ti atoms. In the third Si site, Si is bonded in a 9-coordinate geometry to nine Ti atoms. In the fourth Si site, Si is bonded in a 9-coordinate geometry to nine Ti atoms. In the fifth Si site, Si is bonded in a 9-coordinate geometry to nine Ti atoms. In the sixth Si site, Si is bonded in a 9-coordinate geometry to nine Ti atoms. In the seventh Si site, Si is bonded in a 9-coordinate geometry to nine Ti atoms. In the eighth Si site, Si is bonded in a 9-coordinate geometry to nine Ti atoms. In the ninth Si site, Si is bonded in a 9-coordinate geometry to nine Ti atoms.

36 MATERIALS SCIENCE↗