Study on the mechanical and electrical properties of twisted CNT yarns fabricated from CNTs with various diameters

The mechanical and electrical properties of multiwalled carbon nanotube (MWCNT) yarns with a wide variety of MWCNT diameters were studied to understand the relationship between the microscopic structures of MWCNTs and the load/charge transport properties of macroscopic MWCNT assemblies. The MWCNT diameters were varied from 14.6 nm to 41.6 nm by varying the amount of catalyst loaded in the synthesis by the chloride-mediated chemical vapor deposition method. We found a drastic change in the tensile behavior of twisted yarns from nonlinear deformation to elastic manner associated with the increases in the tensile strength, Young's modulus, and electrical conductivity of the twisted MWCNT yarns for smaller-diameter MWCNTs. These improvements are due to the increase in the surface area of MWCNTs in the yarn structure. We also carried out microscopic direct tensile tests on the MWCNTs in a scanning electron microscope to investigate the tensile properties of the individual MWCNTs. The in situ experiments revealed that the obtained high value of the Young's modulus of the yarn originated from that of the individual MWCNTs.