Process for the production of SiC coatings on high-strength carbon fibres

摘要

The invention relates to the development of a SiC coating process (Figure 1) in which the initial strengths of the carbon fibres are largely retained, SiC bridges between the monofilaments of the fibre bundle are prevented and high coating rates of the fibre bundles are achieved. It is characterised in that the SiC deposition is carried out in two stages with the aid of a shaking device for the fibres. First of all, in a first stage, the carbon-containing silane required to form a thin but continuous layer, such as for example trichloromethylsilane, is decomposed in an argon atmosphere. In a second stage the layer thickness is enlarge by decomposing the silane in a hydrogen atmosphere. This manner of production achieves a high fibre strength with high deposition rate since the uncoated carbon fibre does not come into contact with hydrogen and is not damaged by the formation of hydrocarbon. Reduction of the penetration depth of the reactands into the fibre bundle due to the increased deposition rate, which leads to non-uniform coating of the fibre bundle and to formation of SiC bridges between the individual filaments, can be avoided by using a shaking device for the C-fibre bundle. <IMAGE>