Strengthening Effects of Multi-Walled Carbon Nanotubes and Graphene …
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planes of FCC nickel are the only peak present. The 2-theta degree positions of the
peaks observed agree with X-ray diffraction data files of pure nickel [26]. However,
peaks corresponding to carbon have not been observed as very little amount of CNTs
are present in these composites. The absence of any other peak indicates that no
carbide formation has occurred during mechanical alloying as well as spark plasma
sintering processing.
Microstructural Analysis
SEM micrographs of SPS processed pure nickel and Ni-CNT composites are shown in
Fig. 2. In comparison with the pure nickel sample, all Ni-CNT composites exhibited
excellent grain refinement by inhibiting the grain growth during SPS processing. As
CNT volume fraction increases, the decreases in grain size of pure nickel have been
observed in Ni-CNT composites. Figure 2 reveals the uniform dispersion of CNT
throughout the nickel matrix, and CNTs are primarily located along the nickel grain
boundaries. The dispersion of CNTs and the size of clusters vary with CNT content
in the Ni-CNT metal matrix nanocomposites. It is apparent that the grain size of
Fig. 2 SEM micrographs of pure nickel and Ni-CNT composites
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planes of FCC nickel are the only peak present. The 2-theta degree positions of the
peaks observed agree with X-ray diffraction data files of pure nickel [26]. However,
peaks corresponding to carbon have not been observed as very little amount of CNTs
are present in these composites. The absence of any other peak indicates that no
carbide formation has occurred during mechanical alloying as well as spark plasma
sintering processing.
Microstructural Analysis
SEM micrographs of SPS processed pure nickel and Ni-CNT composites are shown in
Fig. 2. In comparison with the pure nickel sample, all Ni-CNT composites exhibited
excellent grain refinement by inhibiting the grain growth during SPS processing. As
CNT volume fraction increases, the decreases in grain size of pure nickel have been
observed in Ni-CNT composites. Figure 2 reveals the uniform dispersion of CNT
throughout the nickel matrix, and CNTs are primarily located along the nickel grain
boundaries. The dispersion of CNTs and the size of clusters vary with CNT content
in the Ni-CNT metal matrix nanocomposites. It is apparent that the grain size of
Fig. 2 SEM micrographs of pure nickel and Ni-CNT composites