Journal Article

Solid State NMR and TG/MS Study on the Transformation of Methyl Groups During Pyrolysis of Preceramic Precursors to SiOC Glasses

Babonneau, Florence, Latournerie, Jerome, Trimmel, Gregor, Parmentier, Julien, Badheka, Rita, Dempsey, Phillip, Bahloul-Houlier, Djamila, Soraru, Gian Domenico

2003

Overview

The sol-gel method was used to prepare two different starting gels containing SiCH3-groups for the preparation of SiOC ceramics. To understand the role of Si—H bonds in the incorporation of carbon into the SiOC network, gels prepared from a 1:2 mixture of triethoxysilane and methyldiethoxysilane (THDH2) and solely methyltriethoxysilane (TMe) were investigated. Thermogravimetric analysis coupled with mass spectroscopy (TG-MS) in inert atmosphere was performed to attain an insight into the decomposition reactions involved during gel-glass transformation. Samples calcined at different temperatures up to 1000°C were characterized by 29Si and 13C magic angle spinning nuclear magnetic resonance (MAS-NMR) spectroscopy. The presence of SiH groups in the starting gel allows an efficient conversion of Si—CH3 groups into CSi4 sites at lower temperatures. As a result, despite a much lower amount of carbon in the starting THDH2 gel (C/Si = 0.33) compared to the TMe gel (C/Si = 1), the amount of carbon inserted into the SiOC network of both glasses is equivalent, but the TMe sample contains the 10 fold amount of free carbon.

• Publisher: Springer,Springer Nature B.V
• Subject: Carbon / Ceramic bonding / Chemistry / Colloidal gels. Colloidal sols / Colloidal state and disperse state / Decomposition reactions / Exact sciences and technology / Gels / General and physical chemistry / Inert atmospheres / NMR / Nuclear magnetic resonance / Pyrolysis / Sol-gel processes / Spectrum analysis / Thermogravimetric analysis / Transformations