High-strength alkali-resistant sintered SiC fibre stable to 2,200 °C

The high-temperature stability of SiC-based ceramics has led to their use in high-temperature structural materials and composites(1-3). In particular, silicon carbide fibres are used in tough fibre-reinforced composites. Here we describe a type of silicon carbide fibre obtained by sintering an amorphous Si-Al-C-O fibre precursor at 1,800 degrees C. The fibres, which have a very small aluminium content, have a high tensile strength and modulus, and show no degradation in strength or change in composition on heating to 1,900 degrees C in an inert atmosphere and 1,000 degrees C in air-a performance markedly superior to that of existing commercial SiC-based fibres such as Hi-Nicalon. Moreover, our fibres show better high-temperature creep resistance than commercial counterparts. We also find that the mechanical properties of the fibres are retained on heating in air after exposure to a salt solution, whereas both a representative commercial SiC fibre and a SiC-based fibre containing a small amount of boron were severely degraded under these conditions(4). This suggests that our material is well suited to use in environments exposed to salts-for example, in structures in a marine setting or in the presence of combustion gases containing alkali elements.