Simple synthesis process for ZnO sphere-decorated CNT fiber and its electrical, optical, thermal, and mechanical properties

Abstract

An easy process to produce ZnO sphere-decorated CNT (ZSDC) fibers was established. The prepared ZSDC fibers showed aggregated ZnO nanoparticles deposited homogenously as spheres on the CNT fiber surfaces and non-aggregated ZnO nanoparticles invading the inside of the fiber and occupying the gaps among the individual CNTs. The ZnO nanoparticles inside the fiber acted as cross linkers of the individual CNTs by chemical bonding, which improved the Young's modulus and tensile strength of the ZSDC fiber by 340% and 60%, respectively, when compared with bare CNT fiber. The ZSDC fiber exhibited superior light absorption properties throughout the entire region of the visible to near-IR (NIR) spectrum (400–2100 nm) as well as higher thermal stability at 880 °C in a nitrogen environment compared to the bare CNT fiber. In addition, the composite fiber showed very high electrical conductivity (983 S cm⁻¹). This high electrical conductivity suggests that electron movement through the fiber is not hampered by the semi-conductive ZnO nanoparticles. A unique high intensity radial breathing mode (RBM) peak was observed in the Raman spectrum of the ZSDC fiber, whereas the bare CNT fiber did not show a RBM peak. This RBM peak of the ZSDC fiber indicates that there is a special arrangement of ZnO nanoparticles caused by chemical bonding that generates this RBM mode of the CNT fiber in ZSDC.