ИСТИНА

Pyrocarbon (PyC) deposition on carbon fibers Zoltek with a diameter of 7.5 μm was carried out by CVI technique. The following conditions for experiment were used: Т=1050 oC, tR=1 sec, p=140 mbar, the whole process duration was of 2-24 hours. The average thickness of PyC layers was estimated by statistical processing of SEM images. Depending on deposition time the PyC layer with a thickness of 3 μm could be formed. The texture of PyC deposited on carbon fiber depends on the distance to carbon fiber. The main tendency is that no matter what support is used the formation of high textured PyC is observed as the distance to the support increases. The layer-by-layer deposition could be clearly observed in alternation of bright and dark areas in SEM images. The following transition of PyC as the distance to carbon fiber grows was shown. The rough laminar PyC layer that is nearest to the carbon fiber is alternated with the smooth laminar PyC and then again with the rough laminar one [1]. The layer-by-layer character of deposition is clearly seen both on cross-sections and breaks. The formation of PyC layers or PyC spherulites with a diameter of several microns was observed depending on the deficiency of carbon fibers surface. The low amount of active centers restricts the PyC deposition. Thus, the contribution of polycondensation processes in gas phase increases resulting in the deposition of spherical particles. PyC deposited on carbon fiber is characterized with crystalline sizes as low as 3 nm and high deficiency evidenced by almost the similar intensities of D- and G-modes in Raman spectra that is in good agreement with [2].