Results And Discussion

Results Figure 1 shows SEM micrographs of as-received stainless steel powder (Fig. 1(a)). After being heated at various temperatures in the presence of ethanol vapor, the nanotubes grew on the stainless powder as shown in Fig. 1(b). TEM micrograph of as-grown CNTs and its selected area diffraction pattern is shown in Fig. 2. The hollow tubes with many wall layers were observed which confirmed that the as-grown CNTs were a multi-walled type (MWNT). It has been suggest by previous works that a growth of nanostructures using the chemical vapor deposition method with a present of carbon source such as C2H5OH, LPG, C2H2 could provide CNTs SEM micrographs of as-grown CNTs at various temperatures can be seen in Fig. 3. Although it was not measured, the observed CNTs length was rather long (> 1 µm) and fully coated on the stainless steel particles. Average diameter of CNTs was found to increase with increasing of synthesized temperature as plotted in Fig.4. The tube diameters were gradually increased from ∼ 31 nm at the growth temperature of 550°C to ∼ 44 nm at the temperature of 800°C. This is believed to cause by an increase of active catalytic sites (i.e. Fe and Ni elements presented in the as-received stainless steel powder as reported by the manufacturer) due to coalescence at high temperature, which allowed a large intake of C atoms and diffuse flux of C though Fe became faster. Tubes with large diameters were then formed at higher-growth temperatures. From the result, the smallest size of CNTs could be produced at 550°C. However, it should be noted that the sizes of CNTs synthesized in between 550-800°C were rather similar if the values of standard deviations were taken into account. Phase characterization by X-Ray diffractometry showed that the synthesized products consisted of only Fe with cubic phase (JCPDS file no. 870721) as shown in Fig. 5 No trace of C was detected by XRD for all samples. This could be a result of too small quantity of C was presented on the surface of stainless steel particles. Figure 6(a) and 6(b) illustrate SEM micrographs and EDS spectrum of as-received stainless steel particle. The particle’s surface was generally smooth. The powder consisted of iron (Fe), carbon (C), Chromium (Cr), oxygen (O) and nickel (Ni) elements. After the powders were growth by CVD method in the C2H5OH atmosphere, the surface was well covered by CNTs as can be seen in Fig. 6(c) and Fig. 6(d) showed EDS spectrum of as-synthesized stainless steel particle. Table 1 as shown the EDS results of as-received particle and as-synthesized at various temperatures, it was found that C

element increased with increasing the synthesis temperature. It can be confirmed assynthesized sample consisted C element using Raman spectroscopy as a result shown in Fig. 7 Raman spectrum obtained from surface of the as-synthesized samples showed that two Raman shifts at ∼ 1350 cm-1 (D band) and ∼ 1580 cm-1 (G band). The ratios of ID/IG varied in between 0.97 to 1.01. The intensity of Raman spectrum increased with increasing the synthesis temperature, suggesting high CNTs content was achieved at higher temperature.