Viscoelastic Properties of Novel Silicon Carbodiimide Gels

Abstract

A novel non-oxide sol-gel system based on the reaction of bis(trimethylsilyl)carbodiimide with methyltrichlorosilanes has been examined quantitatively with regard to its viscoelastic properties. The chemistry and phenomenology of this process are completely analogous to the well-known oxide solgel process. The changes of the elastic modulus G′ and the viscous modulus G′′ have been measured with low strain amplitude and constant frequency versus time. At the crossover point, i.e., G′ ) G′′, the gel point is reached. The gelation time is independent of the oscillatory frequency ω. The dynamic moduli G′ and G′′ have also been measured versus strain amplitude and shear stress amplitude. A relaxation exponent of n ) 0.65, strength S ) 0.25, and G′ (end of reaction) ) 10 5 Pa‚s have been determined.

新規な非酸化物系ゾルゲル法によるメソポーラスアモルファス Si-C-N 膜の合成と評価

“…TEOS SiOC 2 H 5 4 or TMOS SiOCH 3 4 based systems, with respect to the phenomenology as well as structural, spectroscopic and rheologic properties. 21,22 In this study, a novel sol-gel process-derived polyorganosilylcarobodiimide is designed and synthesized for fabrication of thermally stable amorphous Si-C-N membranes. The chemical composition as well as viscosity of the polyorganosilylcarobodiimide is adjusted for spin coating without solvent.…”

Nonoxide Sol–Gel Synthesis of Terbium‐Doped Silicon Nitride Phosphors

“…This approach has been used by Bradley and colleagues 18–20 using Si(NH 2 )(NMe 2 ) 3 and by Löffelholz et al 28 with Si(NHMe) 4 . A further variation is to use other nitrogen‐containing bridging groups such as (NCN) 2− , as used by Kroke and colleagues 18–20 to produce carbonitrides: …”

“…This sensitivity is due to the need to base the processing on nitrogen donor groups such as amides, which are readily displaced by water. Published work is largely focused on the production of high surface area silicon nitride powders for catalysis 18–20 and Si/B/C/N ceramics 21,22 . Recently, there have been reports of the production of silicon nitride or carbonitride membranes 23,24 and we have reported the formation of films, 25 monolithic gels, 26 aerogels, 26 and inverse opals 27 in nitride materials.…”

Sol–gel derived Si/C/O/N‐materials: molecular model compounds, xerogels and porous ceramics

“…Owing to the pseudo-chalcogenic character of the carbodiimide group, it adopts the role of the oxygen atom, whereas the trimethylsilyl group can be considered as an analog of the protons in a hydrolytic process. [13,16,17] Several materials in the systems Si/C, [18] B/C/N, [19,20] Si/C/N, [21,22] Si/B/C/N, [23 -25] and Si/Al/C/N [26] possessing high thermal resistance and chemical stability, have been synthesized using this particular kind of sol-gel route. Several further reports on related work on BTSC-derived element carbodimides and their use as precursors for hybrid and ceramic materials have been published.…”