R.f.-sputtered SiC coatings on carbon fibres

Abstract

R.f. sputtering as a new method for the deposition of SiC layers onto carbon fibre substrates was applied at temperatures below 400°C and deposition rates higher than 1 μm h -1. Optimum conditions for high quality SiC films were selected by variation in the r.f. power, r.f. peak voltage, substrate temperature and gas pressure. The SiC layers were characterized using electron probe microanalysis, X-ray photoelectron spectroscopy, secondary ion mass spectrometry, transmission high energy electron diffraction, IR and UV transmission spectroscopy as well as Vickers' hardness measurements. Amorphous SiC layers were obtained. In the case of discontinuous SiC deposition onto carbon monofilaments the film thickness precalculated from the sputtering parameters was achieved, whereas the continuous process results in film thickness of about one-third of the precalculated value. When fibre bundles with different numbers of monofilaments were used no influence on the resulting SiC layer thickness could be observed. Increasing the SiC film thickness, however, led to a strong decrease in the fibre tensile strength for layers more than 50 nm thick.