3. Results and discussion
3.1. Feedstock powder characterization
SEM micrograph of as-received stainless steel feedstock powder
which indicated irregular shape and smooth surface is shown in Fig. 2.
After being synthesized using the CVD method at 800 °C for 120 min in a
presence of a C2H5OH atmosphere, carbon nanotubes were grown and
homogeneously covered stainless steel particles as shown inFig. 3(a), (b).
Diameters of the tubes ranged between 30 and 80 nm (Fig. 3(c)) with an
average value of 44 nm. Normal size distribution of SS/CNT composite
powder and that of as-received stainless steel powder were found to be
identical as shown in Fig. 4 which indicated that CNT growth by the CVD
process did not affect the morphologies of stainless steel particles. The
length of the CNTs was rather long and, therefore, it could not be exactly
measured. Nevertheless, it was obviously longer than 1 μm. TEM
micrograph of CNTs is shown in Fig. 5(a). The result revealed hollow
tubes with many wall layers which confirmed multi-walled type CNTs
having a typical hexagonal structure (Fig. 5(b)).