S. Wu et al /Composites: Part A 37(2006)1396-140 3.2. Micro-morphology observation and corrosion product Figs. 4 and 5 are some EDs results of surface and cross-section of the specimens after corrosion for 10 h Only silicon and oxygen were detected at 1100C, while Fig 3 shows the surface morphologies of the specimens silicon, sodium and oxygen were detected above before and after corrosion for 10 h. No obvious change was 1200C. From XRD patterns of the specimens surface observed at 1000C. The corrosion generated a smooth after corrosion at different temperature for 10 h as showed glassy surface at 1100C. At 1200C, a vitreous corrosion in Fig. 6, it was clear that the content of Na20. xSio product can be observed around Sic cluster. Above reached its maximum value at 1300C, and then de- 1300C, a viscous thick glassy corrosion product film with creased with an elevated temperature. The content of pores/corrosion pits could be observed in the surface of SiO2 increased quickly and the silica showed a pro- pecimens. Moreover, the concentration and diameter of nounced phase transformation to a-cristobalite. These re- pores/corrosion pits formed in silicate increased with ele- sults revealed that oxidation by water and oxygen was ated temperature. At 1300, 1400 and 1500C, the corre- dominant below 1200C and the corrosion product was sponding maximum pore/corrosion pit diameter in the silica. Above 1200C, the corrosion product was silicate silicate was about 120, 195 and 500 um, respectively containing sodium. They also indicated that the corrosion 口 100um arbor 6162 ey 100m Fig. 4. Surface EDS of CVD SiC after corrosion for 10 h at:(a)1100C:(b)1200oC. Bubble 01 ui scie 1051 cts Cursor 4 307 bev (cts Fig. 5. Cross-section micro-morphology and eDS of CVD Sic after corrosion at 1300C for 10 h.3.2. Micro-morphology observation and corrosion product analysis Fig. 3 shows the surface morphologies of the specimens before and after corrosion for 10 h. No obvious change was observed at 1000 C. The corrosion generated a smooth glassy surface at 1100 C. At 1200 C, a vitreous corrosion product can be observed around SiC cluster. Above 1300 C, a viscous thick glassy corrosion product film with pores/corrosion pits could be observed in the surface of specimens. Moreover, the concentration and diameter of pores/corrosion pits formed in silicate increased with ele￾vated temperature. At 1300, 1400 and 1500 C, the corre￾sponding maximum pore/corrosion pit diameter in the silicate was about 120, 195 and 500 lm, respectively. Figs. 4 and 5 are some EDS results of surface and cross-section of the specimens after corrosion for 10 h. Only silicon and oxygen were detected at 1100 C, while silicon, sodium and oxygen were detected above 1200 C. From XRD patterns of the specimens surface after corrosion at different temperature for 10 h as showed in Fig. 6, it was clear that the content of Na2O Æ xSiO2 reached its maximum value at 1300 C, and then de￾creased with an elevated temperature. The content of SiO2 increased quickly and the silica showed a pro￾nounced phase transformation to a-cristobalite. These re￾sults revealed that oxidation by water and oxygen was dominant below 1200 C and the corrosion product was silica. Above 1200 C, the corrosion product was silicate containing sodium. They also indicated that the corrosion Fig. 4. Surface EDS of CVD SiC after corrosion for 10 h at: (a) 1100 C; (b) 1200 C. Fig. 5. Cross-section micro-morphology and EDS of CVD SiC after corrosion at 1300 C for 10 h. S. Wu et al. / Composites: Part A 37 (2006) 1396–1401 1399