SiOC

Silicon oxycarbide (SiOC) is a family of silicon-based ceramics characterized by a network that combines silicon–oxygen and silicon–carbon bonds. SiOC is typically formed as a glassy or nanocomposite phase and is often produced by pyrolysis of organosilicon polymers or sol-gel derived precursors, as part of the broader field of polymer-derived ceramics (PDCs).

The as-prepared material is largely amorphous, consisting of a Si–O–C network. Depending on processing, it can contain nanocrystalline silicon carbide (SiC) domains and/or a carbon-rich phase, whose amount and form (graphitic or amorphous) can be tuned by heat treatment and precursor chemistry. The microstructure frequently features a heterogeneous mix of an SiOC matrix with embedded carbon or SiC nanostructures, influencing mechanical and conductive properties.

Synthesis methods for SiOC commonly involve pyrolysis of preceramic polymers such as polycarbosilane or polyorganosiloxanes, typically in inert or reducing atmospheres at temperatures around 800–1200 degrees Celsius. Alternative routes include sol-gel processing of silicon-oxygen-carbon precursors followed by heat treatment. The resulting materials can be processed into bulk ceramics, coatings, or composite matrices.

Properties and applications of SiOC arise from its tunable chemistry and microstructure. SiOC offers high-temperature stability, relatively low density, and adjustable hardness. Carbon-rich variants can exhibit electrical conductivity, while silicon-oxide-rich variants can show enhanced oxidation resistance due to silica formation at high temperatures. Applications include protective coatings, high-temperature structural components, abrasive materials, and functional fillers in ceramic composites. Research continues to optimize oxidation resistance, mechanical performance, and scalable fabrication.

See also: polymer-derived ceramics; silicon carbide; ceramic composites.