Pyrolysis Kinetics for the Conversion of a Polymer into an Amorphous Silicon Oxycarbide Ceramic

Abstract

We present experimental and analytical results for the pyrolysis reactions underlying the conversion of a cross‐linked polymer into an amorphous ceramic material. The activation energies, obtained from thermogravimetric data, and chemical analysis of the volatiles by mass spectroscopy are used to identify the reaction pathways. The reaction is determined to be first‐order, which is consistent with its solid‐state nature. The magnitude of the weight loss is analyzed to calculate the number of molecular sites in the polymer that participate in the reaction. The experiments were conducted on a polymer made from silsesquioxanes that convert into silicon oxycarbide ceramics on pyrolysis. The results show that <2.5% of the silicon atoms in the polymer are removed as volatile silanes, and less than one‐half of the carbon atoms are lost as methane. These results are a first step in understanding the molecular basis for the ceramic yield, as well as the evolution of the nanostructure as the material changes from an organic into a ceramic state by reactions that can occur at <850°C.

Synthesis of SiOC Base Fibers from Silicone Resin with Low Carbon Content and Control of Surface Functionality by Metal Chloride Treatment in Vapor

“…The averaged diameter of the spun fiber is 16.8 µm. The curing process of the spun fiber was performed by placing fiber bundles in a covered vat (800 cm 3 ) with 10ml of SiCl 4 or TiCl 4 in a Teflon dish for 1h. The curing procedure was performed in a glove bag with flowing nitrogen.…”

“…Such resins were used as binding agents for SiC and carbon black filler grains to produce SiC base dense or porous ceramics by molding, shaping and sintering [1]. On the other hand, abnormally high creep resistance of the simple Si-O-C amorphous was reported and analyzed in detail recently [2,3]. In the starting silicone resin precursors, we paid attention to a kind of the polymethylsilsesquioxane -like resin with low carbon content.…”

“…In this article, the properties and structure of the ceramic fibers derived from the melt-spun resin fiber will be described from the viewpoint of curing and pyrolysis conditions. The intrinsic cost of the resin fiber is low, because the starting monomer, CH 3 SiCl 3 , is a major sub product in a silicone industry based on the chemical reaction between metal silicon and CH 3 Cl. In addition, polymerization of CH 3 SiCl 3 does not require special reagents, like sodium or magnesium [6].…”

Effect of filler addition on porosity and strength of polysiloxane-derived porous silicon carbide ceramics

“…The heat treatment allows for the conversion of polysiloxane to silicon oxycarbide in the specimens. 21) The composition of SiOC after pyrolysis at 1400°C was SiO 1.50 C 0.68 . 22) The pyrolyzed specimens were further heat-treated in argon to 1450°C for 1 h at a heating rate of 10°C/min and subsequently annealed at 18001950°C for the liquid-phase sintering of SiC using Al 2 O 3 and Y 2 O 3 .…”

Synthesis and Properties of Porous Hybrid Materials containing Metallic Nanoparticles

“…[8] The transformation of polysiloxanes [RSiO 3/2 ] carrying hydrocarbon groups (R = methyl, phenyl, vinyl) in an inert atmosphere is well investigated and results in the formation of an amorphous silicon oxycarbide (SiOC, 800-1000°C), which decomposes to a ceramic consisting of SiC, SiO 2 and graphite at higher temperatures (1400-1500°C). [9][10][11][12] There are many examples, where a combination of a polysiloxane with a metal or a metal salt was used to prevent shrinkage, crack and pore formation of the resulting dense ceramic following the active filler controlled polymer pyrolysis concept (AFCOP). [2,13,14] Other groups used metal salts to introduce electrical conductivity or magnetic properties to SiOC materials [15] or investigated the Ni catalysed formation of carbon nanotubes in the resulting ceramics, which was observed applying temperatures beyond 800°C.…”