9176 J. Liu et al. Ceramics intemational 39(2013)9173-9178 Fig. 4. SEM images of S-glass fibers before and after treatment in NaOH solution:(a)original fiber, (b) after I h treatment, and (c) after 5 h treatment. The EDX results of S-glass fiber surface before and after NaOH treatment(wt%; n=not detectable) Element Original fiber 67 19.6 129 0.1 After I h treatment 62.6 19.4 After 5h treatment 194 Fig. 5. SEM images of the fiber cross-sections after 5 h treatment in NaOH solution: (a) ECR-glass fiber and(b)Glass fiber. the alkali corrosion for the fibers. As the water molecules off in several areas. On the contrary, the corrosion layer of the continue to penetrate into corrosion layer and some alkali S-glass fibers looks relatively tough. Thus, it is possible that metal releases, the corrosion layer expands and is scaling off the corrosion layer on the S-glass fibers can provide longer he fiber finally. The corrosion process is put to the next protection than that on the ECr-glass fibers. circulation [12 Fig. 5 shows the SEM images of -sections 3.4. Infrared spectra analysis after 5 h treatment in NaOH solution ently, the ECR glass fibers have bigger diameter and thicker corrosion layer To check whether there is framework damage during the compared to those of the S-glass fibers, which probably lead to treatment, the infrared spectra analysis was performed. Fig.6 lower mass loss From Fig. 5 we also can see that the corrosion shows the FT-IR spectra of the ECR-glass and S-glass fibers layer of the ECR-glass fibers is brittle, which is partially peeled before(upper curves)and after(lower curves)5 h treatment inthe alkali corrosion for the fibers. As the water molecules continue to penetrate into corrosion layer and some alkali metal releases, the corrosion layer expands and is scaling off the fiber finally. The corrosion process is put to the next circulation [12]. Fig. 5 shows the SEM images of the fiber cross-sections after 5 h treatment in NaOH solution. Apparently, the ECR￾glass fibers have bigger diameter and thicker corrosion layer compared to those of the S-glass fibers, which probably lead to lower mass loss. From Fig. 5 we also can see that the corrosion layer of the ECR-glass fibers is brittle, which is partially peeled off in several areas. On the contrary, the corrosion layer of the S-glass fibers looks relatively tough. Thus, it is possible that the corrosion layer on the S-glass fibers can provide longer protection than that on the ECR-glass fibers. 3.4. Infrared spectra analysis To check whether there is framework damage during the treatment, the infrared spectra analysis was performed. Fig. 6 shows the FT-IR spectra of the ECR-glass and S-glass fibers before (upper curves) and after (lower curves) 5 h treatment in Fig. 4. SEM images of S-glass fibers before and after treatment in NaOH solution: (a) original fiber, (b) after 1 h treatment, and (c) after 5 h treatment. Table 3 The EDX results of S-glass fiber surface before and after NaOH treatment (wt%; n.¼not detectable). Element Si Al Mg Na Original fiber 67.4 19. 6 12.9 0.1 After 1 h treatment 62.6 19.4 17.9 0.1 After 5 h treatment 52.5 19.4 28.1 n. Fig. 5. SEM images of the fiber cross-sections after 5 h treatment in NaOH solution: (a) ECR-glass fiber and (b) S-glass fiber. 9176 J. Liu et al. / Ceramics International 39 (2013) 9173–9178