20 Laminar aromatic (uo) Isotropic 10 sooty Continuously nucleated Low Surface temperature nucleated 0 1,200 1.700 2,200 Temperature(C) Figure 8.3 High temperature transition after Diefendorf(1970) ◆ 30 8 20 No infiltration 6 Smooth laminar (CVD only or soot) 10 Rough laminar 0 Granular Isotropic 000 1,100 1,200 Temperature (C) Figure 8.4 Existence diagram of the low temperature transition demonstrated in infiltration of a felt.After Loll et al.(1977). The structural aspects of the growth mechanisms were studied by Kaae et al.(1972)and Kaae(1975,1985).With increasing temperature,laminar pyrocarbon is more and more regen- erated by gas-phase nucleated particles as shown in sketch of Fig.8.5.Transition occurs from regenerated laminar(Fig.8.6a)to granular(Fig.8.6b)and to isotropic sooty (Fig.8.6c,d). 2.2.1 Granular pyrocarbon It results from a mechanism where most of the carbon still grows directly onto the surface (molecular condensation)but gas phase-grown particles regenerate continuously ©2003 Taylor&FrancisThe structural aspects of the growth mechanisms were studied by Kaae et al. (1972) and Kaae (1975, 1985). With increasing temperature, laminar pyrocarbon is more and more regen￾erated by gas-phase nucleated particles as shown in sketch of Fig. 8.5. Transition occurs from regenerated laminar (Fig. 8.6a) to granular (Fig. 8.6b) and to isotropic sooty (Fig. 8.6c, d). 2.2.1 Granular pyrocarbon It results from a mechanism where most of the carbon still grows directly onto the surface (molecular condensation) but gas phase-grown particles regenerate continuously Figure 8.3 High temperature transition after Diefendorf (1970). 20 Laminar aromatic Isotropic sooty Surface nucleated Low temperature 10 Pressure (torr) Continuously nucleated 0 1,200 1,700 Temperature (°C) 2,200 Figure 8.4 Existence diagram of the low temperature transition demonstrated in infiltration of a felt. After Loll et al. (1977). 1,000 1,100 1,200 0 10 20 30 Temperature (°C) Isotropic Granular Rough laminar No infiltration (CVD only or soot) Smooth laminar Volumic fraction of methane (%) © 2003 Taylor & Francis