H. Li et al. /Ceramics International 35(2009)2277-2282 Table 1 particles in the composites(Fig. 3b). ZrC slurry prefers to fill Combustion gas composition large pores between the fiber bundles. Hence, the channels from he surface to the inner of composite can be easily blocked by Zrc O Other and pyrolysized SiC. Further infiltration of the slurry thus becomes much difficult after several PlP cycles. The density 16.1 55.3 27.6 .0 measured by the Archimedes method for the final composite about 2.34 g/cm with an open porosity of about 12% which was formed by CVd process is obviously observed (Fig. 3b). Furthermore, it can be seen that there are still few pores 3.2. Microstructure of coatings in the composite(Fig 3a). During the PIP process, the liquid PCS will fill surrounding both the Cvd Sic matrix and the Zrc The cross-sections of different coating structures are show particles. After pyrolysis, the derived Sic integrates ZrC in Fig. 4. ZrC coating with a thickness of about 8 um is p200u Fig 3. Cross-sections of as-received C/ZrC-SiC composites CF: carbon fiber, (a)a low magnification and(b)a high magnification. Pyrolysized Sic CVD SIC 经态100 Fig. 4. Cross-sections of different coating structures (a)#I CVD ZrC coating, (b)#2 Sic-ZrC mixture coating, (c)#3 ZrBx-SiC mixture coating and surface morphologies for(d)#l (e)#2, and (f)#3 specimenswhich was formed by CVD process is obviously observed (Fig. 3b). Furthermore, it can be seen that there are still few pores in the composite (Fig. 3a). During the PIP process, the liquid PCS will fill surrounding both the CVD SiC matrix and the ZrC particles. After pyrolysis, the derived SiC integrates ZrC particles in the composites (Fig. 3b). ZrC slurry prefers to fill large pores between the fiber bundles. Hence, the channels from the surface to the inner of composite can be easily blocked by ZrC and pyrolysized SiC. Further infiltration of the slurry thus becomes much difficult after several PIP cycles. The density measured by the Archimedes method for the final composite is about 2.34 g/cm3 with an open porosity of about 12%. 3.2. Microstructure of coatings The cross-sections of different coating structures are shown in Fig. 4. ZrC coating with a thickness of about 8 mm is Table 1 Combustion gas composition. Components O2 H2O CO2 Other mol.% 16.1 55.3 27.6 1.0 Fig. 3. Cross-sections of as-received C/ZrC–SiC composites. CF: carbon fiber, (a) a low magnification and (b) a high magnification. Fig. 4. Cross-sections of different coating structures (a) #1 CVD ZrC coating, (b) #2 SiC–ZrC mixture coating, (c) #3 ZrB2–SiC mixture coating and surface morphologies for (d) #1 (e) #2, and (f) #3 specimens. H. Li et al. / Ceramics International 35 (2009) 2277–2282 2279