P-CVD/CVI is used to densify model pores and to fabricateNicalon/SiC microcomposites with pyrocarbon or (PyC-SiC)nmultilayered interphases. The gaseous precursors are hydrocarbons(CH4 or C3H8) for pyrocarbon and CH3SiC13-H2 for SiC. The bestdensification conditions for 60 ; 120 and 320 mu m model pores, bypyrocarbon, are T = 900-1000 deg C , P2 = 1-3 kpa and tR = a few s.Even under such conditions, a thickness gradient is always presentalong the pore axis. Filling ratios as high as 90o/o are observed forthe largest pores. Smooth or rough laminar pyrocarbon is depositeddepending on the value of tR and hence the maturation of the gasphase. Multilayered (PyC-SiC)n interphases act as mechanical fusesand are more resistant to oxidation than pyrocarbon interphase. P- CVD/CVI can be used to elaborate highiy engineered new ceramics.
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