Formation of Mullite from Filled Siloxanes

Abstract

Monolithic mullite with low sintering shrinkage was synthesized from polymer/filler blends-that is, siloxane/ alumina (siloxane/Al 2 O 3 ) (and siloxane/aluminum (siloxane/Al)) mixtures. The synthesis was based on a reactionbonding process of amorphous silica, which formed when the siloxane was oxidized, with Al 2 O 3 (or oxidized aluminum filler) at temperatures >1250°C. Thermodynamic calculations were used to calculate the phase composition at equilibrium. Thermoanalytical, infrared-spectroscopic, and microscopic techniques were applied to reveal the microstructural evolution. The corresponding volume changes were used to evaluate the linear shrinkage, based on the quantitative phase assemblage.

Development of multiphase bioceramics from a filler-containing preceramic polymer

“…In this case, the fillers simply partially reduce the total shrinkage in the component, by diluting the transforming mass [6]. Oxide powders have rarely been added as fillers to produce all-oxide ceramics [7][8][9], probably due to the fact that typically preceramic polymers are processed in inert atmosphere in order to retain the C atoms which play a key role in the development of the unique microstructure and properties of PDCs [10]. However, some www.elsevier.com/locate/ceramint papers have very recently highlighted the potentialities of using such oxide fillers in combination with polymethylsiloxanes.…”

Structure properties relationship in silicon oxycarbide glasses obtained by spark plasma sintering

“…In the case of Al 2 O 3 reinforced samples, the formation of a mullite phase is common in this kind of materials and was also corroborated through infrared spectroscopy [12,20,21]. The formation of mullite inhibits the devitrification of the amorphous matrix [20] and gives as a result a decrease of the pure silica phase available to react with the free carbon phase in the carbothermal reduction.…”

“…2b), but the absence of the aluminum carbide-derived bands indicates that there are no reaction between the Al and C atoms, as occurs at low sintering temperatures when using aluminum as a filler and conventional ceramic route [7]. However, the presence of a sharp peak at 1160 cm À 1 in the spectra on the Al 2 O 3 reinforced samples is interpreted as a sign of formation of a mullite phase, as several authors reported [12,20,21]. Raman spectra of all the obtained nanocomposites show the typical bands of carbon-containing materials, the D and G bands in the first order spectra, and the non resolved resonance modes of the second order spectra, characteristics of highly disordered structures (Fig.…”

Processing of polysiloxane-derived porous ceramics: a review

“…• C to facilitate mullite formation [106,107]. Kim et al adapted this approach to prepare partially interconnected open-cell microcellular mullite ceramics with cell densities greater than 10 9 cells cm −3 and cell size smaller than 20 µm from an Al 2 O 3 -filled polysiloxane [108].…”