Abstract

Silsesquioxane (SQ) derivatives possessing intramolecular H2C = CH- groups and Si-H groups were designed as precursors for ternary silicon oxycarbide (SiOC). By using R-Si(OMe)3, H-Si(OEt)3 and (H-Si(Me)2)2O as starting compounds, SQ derivatives of VH-SQ (R = vinyl) and St-H-SQ (R = stylyl) were successfully synthesized through the conventional sol-gel route. Simultaneous thermogravimetric and mass spectroscopic analyses up to 1000 °C revealed that in situ cross-linking via hydrosilylation and demethanation of VH-SQ suppressed the evolution of gaseous hydrocarbon species to afford amorphous SiOC having a composition close to the desired stoichiometric SiO2(1−x)Cx (x = ca. 0.3) with a high yield. The effect of carbon content on the phase separation and crystallization of the SQ-derived amorphous SiOC was studied by several spectroscopic analyses and TEM observation. The results were discussed aiming to develop a novel polymer-derived ceramics (PDCs) route for in situ formation of binary β-SiC-amorphous SiO2 nanocomposites with enhanced thermal and mechanical stability.

Highlights

  • Increasing attention has been directed to organic–inorganic hybrid materials as promising functional materials in diverse fields such as optics, electronics, housing and energy

  • The chemical structures of VH-SQ and St-H-SQ were identified by the attenuated total reflection–infra red (ATR-IR) and 29 Si nuclear magnetic resonance (NMR)

  • These results revealed that VH-SQ and St-H-SQ had possessing a common main architecture study were converted to inorganic groups were eliminated during pyrolysis uppurification to 800 °C, the SQ derivatives synthesized with different compositions that was successfully synthesized as designed

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Summary

Introduction

Increasing attention has been directed to organic–inorganic hybrid materials as promising functional materials in diverse fields such as optics, electronics, housing and energy. The chemical composition of polymer-derived SiOC materials can be tetrahedral [7]. Carbon-rich silicon oxycarbides have oxycarbides have been synthesized [7,8,9] They exhibit an excellent thermal stability in terms of keeping been synthesized [7,8,9]. For improving the thermal and mechanical stability of SiC-amorphous SiO2 composites, it is. SiC-SiO2 composite (according to Equation (1) without excess carbon). 1.5C0.31 possessed a a composition with relatively low carbon content and was close to the SiC-SiO2 tie line (labeled as (B). In Figure 2),with resulting in thelow formation binary and β-SiC nanocrystallites finely dispersed amorphous. 2)—approximately two2(1−x) times higher compared with thosecontent of the (labeled previousas (B)S1and in Figure 2—was synthesized together with a reference material carbon-rich For the synthesis compositions of S1 and S2, silsesquioxane (SQ) derivatives which havereported intramolecular

Chemical of the polymer-derived amorphous in literature
Precursor Synthesis
Experimental
Pyrolysis and Heat Treatment
Characterizations
SQ Preceramic Polymers
29 Si composing the ternary
Pyrolytic
Crystallization
C K-edge showed the spectrumthat typical for amorphous treatment that at 1400
EELS spectra for SQ-derived
Polymeric
Summary
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