Influence of purity and level of disorder on the spinnability of CNTs yarn derived from the CNTs forest grown by a parametrically tuned CVD

The chemical vapour deposition (CVD) grown carbon nanotubes (CNTs) forest can be transformed into its yarn and sheet thus provides a novel way to harness the excellent properties of microscopic CNTs at a macroscopic scale. The long length CNTs yarn and sheet have been developed from a highly drawable and spinnable vertically aligned CNTs forest with millimetre scale array height based on the parametric investigations of a practically viable single-step CVD growth process. The CNTs growth analysis reveals ‘root growth’ type of growth mechanism. The growth temperature, gas residence time tuned with carrier gas flow rate and controlled supply of hydrogen gas are found to predominantly influence the properties of the CNTs forest like purity, defects levels, spinnability which ultimately controls the quality of the developed CNTs yarn and sheet. The CNTs forest grown from parametrically tuned CVD produced the CNTs with very low defect level of 0.26, inferred from Raman studies and high purity of 98%, accessed from TGA. The CNTs forest grown at growth temperature 840 °C with 300:25:300 sccm optimal ratios of gas flow rates for argon, hydrogen and acetylene are highly spinnable into its long length yarn and sheet which demonstrated excellent tensile strength of ~ 1.186 GPa and ~ 210 MPa, respectively, and electrical conductivity of 2.05 × 10⁴ S/m and 2.57 × 10⁴ S/m, respectively, revealing the strong influence of the purity and level of disorder on the quality of the CNTs yarn and sheet. The high degree of alignment of CNTs within its sheet was assessed from the polarized Raman studies. The obtained excellent physical properties of the grown CNTs forest, its yarn and sheet are comparable with the other reports suggesting its suitability for relevant applications.