Ceramic Fiber
Ceramic fiber is the ultimate thermal barrier among commercial fibers — capable of continuous service at 1200–1600°C where glass fiber melts (~850°C) and all organic fibers have long since decomposed. It is produced by sol-gel spinning: a precursor gel of metal oxides (alumina Al₂O₃, silica SiO₂, or silicon carbide SiC) is spun into a green fiber, then sintered at 1000–1600°C to burn off organics and fuse the ceramic grain structure. The result is a polycrystalline, brittle, ultra-high-temperature fiber used for furnace linings, aerospace thermal protection, and hot-gas filtration. Its cost and brittleness confine it to applications where nothing else survives.
Inorganic / Alumina-Silicate High-Temperature Fiber
Quick Facts
| Type | Inorganic; polycrystalline metal oxide fiber; alumina (Al₂O₃), silica (SiO₂), silicon carbide (SiC), or combinations |
| Production | Sol-gel spinning (precursor fiber → dried → sintered at 1000–1600°C); chemical vapor deposition (CVD) for SiC fibers |
| Service temperature | Alumina-silicate: 1200–1400°C continuous; SiC: >1600°C in inert atmosphere; the highest service temperature of any commercial fiber class |
| Density | 2.5–4.0 g/cm³ (alumina ~3.9; SiC ~2.5–3.2) — heavier than organic fibers, lighter than metals |
| Key types | Alumina fiber (Al₂O₃ >70%), alumina-silicate (Al₂O₃ + SiO₂), silicon carbide (SiC), alumina-boria-silicate (Nextel™ 3M) |
Properties
| Property | Rating | Engineering implication |
|---|---|---|
| Heat resistance | ★★★★★ | 1200–1600°C continuous; highest among all commercial fibers; the defining property |
| Strength (high temp) | ★★★★★ | Retains strength at temperatures where all organic fibers have decomposed; strength actually increases for some types up to ~1000°C (grain growth) |
| Chemical stability | ★★★★☆ | Excellent oxidation resistance (oxide ceramics); SiC oxidizes above 1000°C but forms protective SiO₂ layer |
| Brittleness | ★★☆☆☆ | Very brittle; essentially zero plastic deformation; catastrophic failure; requires careful handling |
| Cost | ★★★★☆ | Very expensive; specialty aerospace and industrial material; not for commodity applications |
Applications
| Application | Form | Key criteria |
|---|---|---|
| Furnace linings / kiln insulation | Alumina-silicate blanket/board; 1260–1430°C grade | Thermal insulation at temperatures where glass fiber melts; steel, ceramics, glass industries |
| Aerospace thermal protection | Nextel™ woven fabric; alumina-boria-silicate | Space Shuttle tiles, rocket engine insulation, aircraft fire barriers |
| High-temperature filtration | Ceramic fiber needled felt; SiC or alumina | Hot gas filtration >500°C; power plant flue gas, incinerators |
| Metal matrix composites | SiC continuous fiber; Al or Ti matrix | Aerospace engine components; high specific strength + high temperature capability |
Summary
Ceramic fiber is the ultimate thermal barrier — the only fiber class that operates continuously above 1000°C. Its brittleness and cost confine it to applications where no organic or glass fiber can survive. See the Textile Material framework.