Issue 21, 2010
From the journal:

Dalton Transactions

Aluminosilicates with varying alumina–silica ratios: synthesis via a hybrid sol–gel route and structural characterisation

Padmaja Parameswaran Nampi,†*a   Padmanabhan Moothetty,b   Frank John Berry,‡c   Michael Mortimerc  and  Krishna Gopakumar Warriera  

* Corresponding authors

a Materials and Minerals Division, National Institute for Interdisciplinary Science and Technology (NIIST) [Formerly Regional Research Laboratory], Council of Scientific and Industrial Research, Trivandrum, Kerala, India
E-mail: padmavasudev@gmail.com, padmaja@sctimst.ac.in
Fax: +91-471-2491712
Tel: +91-471-2515280

b School of Chemical Sciences, Mahatma Gandhi University, Priyadarshini Hills, Athirampuzha, Kottayam, India

c Department of Chemistry and Analytical Sciences, The Open University, Walton Hall, Milton Keynes, UK

Abstract

Aluminosilicates with varying Al2O3:SiO2 molar ratios (3 : 1, 3 : 2, 3 : 3 and 3 : 4) have been synthesized using a hybrid sol–gel route using boehmite sol as the precursor for alumina and tetraethyl orthosilicate (TEOS) as the precursor for silica. The synthesis of boehmite sol from aluminium nitrate, and its use as the alumina precursor, is cost effective compared to alkoxide precursors. Structural aspects, including bonding and coordination, are studied in detail for samples calcined in the temperature range 400–1400 °C using both NMR and FTIR spectroscopy: the results are correlated with phase formation data (spinel and high temperature phases) obtained from XRD and thermal analysis. FTIR results show a broadening of peaks at 800 °C indicating a disordered distribution of octahedral sites caused by crosslinking between AlO6 octahedral and SiO4 tetrahedral units prior to the formation of mullite. 27Al MAS NMR spectra are consistent with a progressive decrease in the number of AlO6 polyhedra with increasing temperature corresponding to Al in these units being forced to adopt a tetrahedral coordination due to the increasing presence of similarly coordinated Si species. XRD results confirm the formation of pure mullite at 1250 °C for a 3Al2O3:2SiO2 system. At 1400 °C, phase pure mullite is observed for all compositions except 3Al2O3:SiO2 where α-Al2O3 is the major phase with traces of mullite. The synthesis of aluminosilicates through a hybrid sol–gel route and the detailed insight into structural features gained from spectroscopic and diffraction techniques contributes further to the development of these materials in applications ranging from nanocatalysts to high-temperature ceramics.

Graphical abstract: Aluminosilicates with varying alumina–silica ratios: synthesis via a hybrid sol–gel route and structural characterisation

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Article information

DOI
https://doi.org/10.1039/C001219J
Article type
Paper
Submitted
20 Jan 2010
Accepted
25 Mar 2010
First published
21 Apr 2010

Dalton Trans., 2010,39, 5101-5107

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Aluminosilicates with varying alumina–silica ratios: synthesis via a hybrid sol–gel route and structural characterisation

P. P. Nampi, P. Moothetty, F. J. Berry, M. Mortimer and K. G. Warrier, Dalton Trans., 2010, 39, 5101 DOI: 10.1039/C001219J

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