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Metal/Ceramic Nanocomposites by Sol-Gel Processing of Tethered Metal Ions: Optimization of the Particle-Forming Step

Published online by Cambridge University Press:  15 February 2011

Claus Görsmann
Affiliation:
lnstitut für Anorganische Chemie der Universität, Am Hubland, D-97074 Würzburg, Germany
Ulrich Schubert*
Affiliation:
lnstitut für Anorganische Chemie der Universität, Am Hubland, D-97074 Würzburg, Germany Institut für Anorganische Chemie der Technischen Universität Wien, Getreidemarkt 9, A-1060 Wien, Austria, uschuber@fbch.tuwien.ac.at
Jürgen Leyrerc
Affiliation:
Degussa AG, P.O.Box 1345, D-63403 Hanau 1, Germany
Egbert Lox
Affiliation:
Degussa AG, P.O.Box 1345, D-63403 Hanau 1, Germany
*
+To whom correspondence should be addressed at the Technische Universität Wien
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Abstract

The nanocomposite Pt · 62 SiO2 was prepared by sol-gel processing of Pt(acac)2, two equivalents of H2 NCH2 CH2 NH(CH2)3Si(OEt)3 and 60 equivalents of Si(OEt)4, followed by heating of the obtained metal complex-containing gel in air. When the temperature treatment is performed at T ≥ 550°C, elemental Pt is the only crystalline phase. The influence of the calcination conditions (maximum temperature, period of heating) on the size and size distribution of the resulting Pt particles and on the morphology of the SiO2 matrix (surface area, pore volume) was investigated. When the temperature does not exceed 550°C, small Pt particles (3–5 nm) are formed which have a very narrow size distribution. Their size and size distribution are not affected by the period of heating. Gels heated to 550°C still contain about 0.1 – 0.25 wt% carbon. Carbon-free particles are obtained at 950°C However, at temperatures between 750°C and 950°C the average size of the particle increases considerably, and the size distribution gets very broad, particularly for rxtended periods of heating. The specific surface area increases from about 50 m2 /g in the metal complex-containing gel to about 230 m2/g during the oxidation step. At temperatures above 500°C considerable sintering of the matrix occurs. The pore volumes show the same trend. Heating the gels to 500°C results in the formation of nanopores with radii below 2 nm, which disappear again on heating to higher temperatures.

Type
Research Article
Copyright
Copyright © Materials Research Society 1996

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