As-electrospun AIP/PVP nanofibers calcined at 800°C
had 67.13% of C, 29.37% of O, and 3.5% of Al, and those calcined at 1,200°C had only 61.38% of O and 38.62% of Al, respectively. Figure 2 SEM images and diameter distributions. SEM images of as-electrospun PVP (a), as-electrospun AIP/PVP nanofibers (b), nanofibers calcined at 800°C (c) and 1,200°C (d). Diameter distributions (e). The inset shows EDX quantification. Figure 3 shows the XRD spectra of the alumina nanofibers calcined between 500°C and 1,200°C. There was also no distinct diffraction peak appearing for the samples calcined at 500°C and 600°C, and phase structure was found to be amorphous/microcrystalline. However, with the increase of calcination temperature up to 900°C, the typical peak of γ-Al2O3 was displayed with strong diffraction intensity. The γ-phase structure became weak when the temperature was buy 17DMAG above 1,000°C and completely disappeared at 1,100°C. The XRD spectrum of the sample calcined at 1,200°C ACY-241 mw indicated that α-alumina phase was formed. All the observed diffraction peaks matched well with those reported by Shanmugam et al. (JCPDS card no. 42-1468) . From the above results, the phase transition of alumina nanofibers in this study can be shown as follows: amorphous/microcrystalline → γ-Al2O3 → α-Al2O3. In the process of heat treatment, the trihydroxide undergoes a series of transformation because of the water loss
from hydration. Figure 3 XRD spectra of alumina nanofibers. Calcined at 500°C, 600°C, 700°C, 800°C, and 900°C (a), and 900°C, 1,000°C, 1,100°C, and 1,200°C (b). Figure 4 shows the FT-IR spectra CB-5083 mw of the alumina fibers obtained after calcination of the composite fibers at 500°C to 1,200°C, AIP solution, AIP/PVP solution, and as-electrospun composite fibers. Three
characteristic peaks at 634, 581, and 440 cm−1 for alumina nanofibers calcined at 1,000°C, which it was confirmed α-phase alumina (Figure 4b), were observed, indicating Al-O bending and Al-O stretching. These peaks can be attributed to the presence of alumina; this conclusion is also supported Farnesyltransferase by results of the XRD analysis . Figure 4 FT-IR spectra of alumina fibers. AIP solution, AIP/PVP solution, and as-electrospun AIP/PVP composite nanofibers (a), and alumina nanofibers calcined at different temperatures (b). The nitrogen adsorption and desorption isotherms and the corresponding pore size distribution of the synthesized alumina nanofiber calcined at 800°C and 1,200°C temperatures are shown in Figure 5. As observed in Figure 5a, both the isotherms were types IV and V, which were related to the mesoporous structure. However, the types of hysteresis loops were different from each other as the calcination temperatures changed. The hysteresis loop type of the alumina nanofiber calcined at 800°C and 1,200°C were H2 and H4 . The surface area of two samples calcined at 800°C and 1,200°C were 177.8 and 42.7 m2/g.