Fibrous reinforcing phase may be arranged in different structures (unidirectional, 2D, 3D):
Different ceramic materials (silicon carbide, carbon, alumina, silica) provide different combination of the fiber properties: strength, modulus of elasticity, flexibility, creep resistance, chemical stability and oxidation resistance.
Silicon carbide (SiC) and carbon are the most popular fibers materials.
Filaments from organosilicon precursors are used for fabrication of silicon carbide fibers. SiC is formed during the precursor curing (cross-linking) followed by heating in nitrogen atmosphere to a temperature of about 2200°F(~1200°C).
The most popular trade marks of SiC fibers: Hi-Nicalon, Nicalon S, Sylramic, Tyranno.
The properties of SiC fibers:
Carbon fibers are fabricated from organic precursor filaments. At the first stage they are carbonized in nitrogen at a temperature of about 2200 °F (~1200°C) and then graphitized at about 4500°F (~2500°C).
The most popular trade marks of carbon fibers: BP Amoco, Conoco, Grafil, Granoc, Toho, Toray, Zoltek.
The properties of carbon fibers:
Low oxidation resistance is the main drawback of carbon fibers, which oxidize when exposed in air at temperatures exceeding 932°F (500°C).
Alumina fibers, which are the most popular oxide fibers, are manufactured from an organic alumina precursor. The precursor transforms into alumina after heating to 1472°F (800°C). Mullite fibers are fabricated from a mixture of alumina precursor with an organosilicon.
The properties of alumina fibers:
The main disadvantages of alumina fibers are relatively low creep resistance caused by grain growth at high temperatures and relatively high density.