CNTs/Al mixtures containing various amounts of CNTs (0e5
vol. %) were prepared by the spark plasma sintering (SPS)
method (Model 1050, Sumitomo Coal Mining Co. Japan) using
Al powder (purity: 99.9%, particle size: 3 mm) and a CNT
mixture. The SPS process was performed at 500 C for 5 min
with a heating rate of 100 C/min. The applied uniaxial stress
was changed from 20 to 30, and then to 50 MPa.