K. Shimoda et al./ Composites Science and Technology 68(2008)98-105 Micro 500um Fig. 4. Typical cross-section of SiC/SiC composites fabricated by (a)CVI process and(b)NITE process. 3. Results and discussions 3.2. Density and microstructural evolution 3.. Coating Density and porosity of hot-pressed SiC/SiC composites dre summar ed in Table 3. The matrix in NITE-SiC/Sic is Fig. 2 shows FE-SEM images of uncoated and Pyc consisted of well-crystallized B-Sic grains with small coated fibers formed with CVD coating technique. Most amount of oxide remnants including aluminum and filaments in the tows through CVD were well coated, with yttrium (mostly YAG: yttrium aluminum garnet), from the thickness of appropriately 0. 25, 0.50 and 1.00 um Sur- XRD analysis as shown in Fig. 3. The presence of YAG face of PyC coated fiber was smooth without relation to should improve sinterability of the matrix in composites PyC layer thickness [20]. Such well-crystallized Sic matrix suggests environ- (a) ntra fiber-tows (c) (d) e 50um Fig. 5. SEM images of polished cross-section of SiC/SiC composites with various PyC interface thickness: (a)uncoated, (b)CVD-0 25, (c)CVD-050 and (d)CVD.3. Results and discussions 3.1. Coating on fiber surface Fig. 2 shows FE-SEM images of uncoated and PyC coated fibers formed with CVD coating technique. Most filaments in the tows through CVD were well coated, with the thickness of appropriately 0.25, 0.50 and 1.00 lm. Sur￾face of PyC coated fiber was smooth without relation to PyC layer thickness. 3.2. Density and microstructural evolution Density and porosity of hot-pressed SiC/SiC composites are summarized in Table 3. The matrix in NITE-SiC/SiC is consisted of well-crystallized b-SiC grains with small amount of oxide remnants including aluminum and yttrium (mostly YAG: yttrium aluminum garnet), from XRD analysis as shown in Fig. 3. The presence of YAG should improve sinterability of the matrix in composites [20]. Such well-crystallized SiC matrix suggests environ￾Fig. 4. Typical cross-section of SiC/SiC composites fabricated by (a) CVI process and (b) NITE process. Fig. 5. SEM images of polished cross-section of SiC/SiC composites with various PyC interface thickness: (a) uncoated, (b) CVD-0.25, (c) CVD-0.50 and (d) CVD-1.00. K. Shimoda et al. / Composites Science and Technology 68 (2008) 98–105 101