Carbide-derived ceramic nanocomposites represent a specialized class of materials with tunable porosity, mechanical robustness, and thermal stability. These materials are synthesized through controlled pyrolysis of carbide precursors, such as silicon carbide (SiC), transitioning into silicon oxycarbide (SiOC) or related ternary systems. The transformation involves precise thermal decomposition under inert or reactive atmospheres, yielding nanostructured ceramics with tailored properties for demanding applications like filtration and catalysis.

The pyrolysis process is central to the formation of carbide-derived nanocomposites. When SiC undergoes pyrolysis at temperatures between 800°C and 1400°C in an oxygen-limited environment, selective removal of carbon or silicon occurs, leading to the formation of SiOC. The reaction pathway and final composition depend on parameters such as heating rate, dwell time, and gas atmosphere. For instance, argon or nitrogen atmospheres favor retention of carbon-rich phases, while trace oxygen introduces oxide domains. The resulting SiOC nanocomposite exhibits an amorphous network of SiO4, SiO3C, and SiC4 tetrahedra, with nanodomains of free carbon enhancing electrical conductivity and mechanical reinforcement.

Porosity control is achieved through templating or selective etching. Chlorination of SiC at intermediate temperatures (500°C–1000°C) removes silicon as volatile SiCl4, leaving a carbon-rich matrix with micropores (<2 nm) and mesopores (2–50 nm). Alternatively, polymer-derived ceramic routes employ preceramic polymers mixed with sacrificial templates (e.g., polystyrene microspheres), which decompose during pyrolysis to create interconnected macropores. The pore size distribution directly influences permeability and surface area, with BET surface areas ranging from 200 m²/g to 800 m²/g for optimized structures. Narrow pore size distributions (<10 nm) are critical for molecular sieving in gas separation filters, while hierarchical porosity (micro-meso-macro) enhances mass transport in catalyst supports.

Tribological properties of SiOC nanocomposites are governed by their nanoscale heterogeneity. The amorphous SiOC matrix provides hardness (8–12 GPa) and wear resistance, while dispersed carbon nanodomains act as solid lubricants, reducing friction coefficients to 0.1–0.2 under dry sliding conditions. High-temperature stability up to 1200°C makes these materials suitable for abrasive environments where conventional polymers or metals degrade. Wear rates as low as 10⁻⁶ mm³/Nm have been reported for SiOC composites with 15–20 vol% free carbon, attributed to the formation of protective carbon-rich transfer films on counterfaces.

In filtration applications, carbide-derived nanocomposites serve as inert membranes for hot gas or corrosive liquid separation. Their chemical resistance to acids and bases surpasses that of polymeric or metallic filters, with negligible swelling or leaching. For example, SiOC membranes with 5 nm average pore diameters exhibit H₂/N₂ selectivity ratios >50, leveraging kinetic diameter differences. In particulate filtration, gradients in porosity (from macro to micro) enable depth filtration with >99.9% efficiency for submicron particles, while maintaining low pressure drops (<0.1 bar at 1 cm/s flow velocity).

Catalyst supports benefit from the high surface area and thermal conductivity of these materials. Platinum nanoparticles (3–5 nm) dispersed on mesoporous SiOC show improved sintering resistance compared to alumina supports, maintaining 90% activity after 100 hours at 800°C in methane combustion. The carbon phase facilitates electron transfer in electrochemical catalysts, while the ceramic matrix prevents agglomeration. For Fischer-Tropsch synthesis, cobalt-loaded SiOC supports yield C5+ selectivity enhancements of 15–20% relative to silica, due to optimized metal-support interactions.

Processing challenges include minimizing crack formation during pyrolysis, which arises from volumetric shrinkage (15–25%). Strategies like filler incorporation or stepwise heating mitigate stress buildup. Future developments may explore doping with transition metals (e.g., Ti, Zr) to introduce redox-active sites, further broadening catalytic functionality without compromising thermal stability.

Carbide-derived ceramic nanocomposites thus offer a versatile platform for extreme-environment applications, combining the durability of ceramics with the tunable nanostructure of pyrolytic materials. Their performance in filtration and catalysis underscores the importance of precursor selection and pyrolysis control in tailoring functional properties.