Sol-gel preparation of mesoporous Al2O3-SiO2 glasses: structural evolution monitored by solid state NMR

Author(s)

Ren, Jinjun ^[1] ; Zhang, Long ^[2] ; Eckert, Hellmut ^{[1, 3]}

Affiliation

^[1] Univ Munster, Inst Phys Chem, D-48149 Munster - Germany

^[2] Chinese Acad Sci, Shanghai Inst Opt & Fine Mech, Shanghai 201800 - Peoples R China

^[3] Univ Sao Paulo, Inst Fis Sao Carlos, BR-13590 Sao Carlos, SP - Brazil

• Document type: Journal article
• Source: Journal of Sol-Gel Science and Technology; v. 70, n. 3, p. 482-490, JUN 2014.
• Web of Science Citations: 7

Abstract

Glasses along the composition line 0.5Al(2)O(3)-xSiO(2) (1 a parts per thousand currency sign x a parts per thousand currency sign 6) were prepared via a novel sol-gel route using tetraethylorthosilicate and aluminum lactate as precursors. The structural evolution from solution to gel to glass is monitored by standard Al-27 and Si-29 nuclear magnetic resonance (NMR) spectroscopies, revealing important insights about molecular level mechanisms occurring at the various stages of glass formation. Under the experimental conditions reported, silica and alumina precursors undergo homoatomic condensation processes when the gel is heat treated at about 100 and 300 A degrees C, respectively, and only little heteroatomic co-condensation occurs in this temperature range. The latter is promoted only upon elimination of the residual lactate and water ligands upon annealing the gels above 300 A degrees C. Following calcination at 650 A degrees C, mesoporous glasses are obtained, having average pore diameter of about 3 nm and a surface areas near 500 m(2)/g. Si-O-Al connectivities are detected by Si-29 magic angle spinning (MAS)-NMR. Al-27 MAS-NMR spectra reveal aluminum in four-, five- and six-coordination. The spectra differ significantly from those of other sol-gel derived Al2O3-SiO2 materials prepared from different precursor routes, suggesting that the lactate route results in a higher degree of compositional homogeneity. (AU)

• FAPESP's process: 13/07793-6 - CEPIV - Center for Teaching, Research and Innovation in Glass
• Grantee: Edgar Dutra Zanotto
• Support Opportunities: Research Grants - Research, Innovation and Dissemination Centers - RIDC