Abstract
In this paper, a spark plasma sintering (SPS) method was employed to solidify single-walled carbon nanotubes (SWCNTs) only, and the effect of processing conditions on the mechanical properties of the SWCNT solids were examined using a small punch (SP) testing method. The sintering temperatures used was in the range of 600∼1400°C, and the sintering pressures used was 40 MPa and 120 MPa. It was demonstrated that the SPS method allowed SWCNTs to be solidified, without any additives. The experimental results showed that the purification of raw soot was critically importance. The SWCNT solids prepared from purified raw soot showed significant non-linear deformation response, producing quasi-ductile fracture behavior. In contrast, raw soot produced brittle solids. The Young's modulus, fracture strength and work of fracture increased with the increasing sintering temperature and pressure. The Raman and SEM analyses showed that the amount of the graphite-like materials were observed to increase with the increasing temperature and pressure, which indicate that the structure of the SWCNTs was changed partially into the graphite-like materials. The formation of graphite-like materials increased tendency of brittle fracture in the SWCNT solids. TEM observations revealed that the fracture surfaces of the SWCNT solids were characterized by pull out of SWCNT bundles. This observation suggests that it may be possible to improve the mechanical properties of SWCNT solids by increasing the cohesion between SWCNTs.
