Chemical composition of CNTs was characterized using XRD as
shown in Fig. 6. As-received stainless steel and as-synthesized powders
mainly consisted of Fe with a cubic structure (JCPDS file no. 870721). No
trace of carbon was detected by X-ray. This could be a result of too small
quantity of CNTs present in the sample. However, the EDS spectrum of
the as-synthesized powder (Fig. 7) could confirm not only the Fe
element (~41 wt.%), but also the high content of C (~39 wt.%) with a
small amount of Cr, O and Ni. Cr and Ni were originally incorporated as
alloying elements in stainless steel as mentioned in the experimental
procedure section. It could be noticed that there was also a Si peak
detected in the sample. This element was not originally contained in the
starting stainless steel powder and thus should not be seen in the assynthesized
powders as well. The appearance of Si could be the result of
impacting of X-ray on a solid state SiLi detector which inadvertently
knocked out Si K-shell electrons in the detector and reduced X-ray's
energy measured in the detector by the Si absorption edge energy
(~1.74 keV). Moreover, wall-induced contamination from quartz tube
was also a possible cause since this was the only the part that was
involved with Si-containing material during synthesis of SS/CNT
composite particles.