title: Tuning array morphology for high-strength carbon-nanotube fibers.
abstract: Vertically aligned carbon-nanotube arrays are synthesized by chemical vapor deposition. Carbon-nanotube fibers are directly spun from the obtained nanotube arrays and then tested mechanically. A strong correlation between the array morphologies and the mechanical properties of the fibers is observed: well-aligned arrays yield fibers with much higher performance, while wavy and entangled arrays give poor fiber properties. More importantly, such array morphologies could be controlled by introducing hydrogen or oxygen during the nanotube synthesis. By simply switching the growth condition from 150 ppm oxygen addition to 2% hydrogen addition, the nanotube array changes from the wavy morphology to the well-aligned morphology, and correspondingly the tensile strength of the resultant fibers could be increased by 4.5 times, from 0.29 GPa for the fibers spun from the oxygen-assistance-grown nanotube arrays to 1.3 GPa for the fibers spun from the hydrogen-assistance-grown nanotube arrays. The detailed effects of hydrogen and oxygen on the nanotube growth, especially on the growth rate and the array spinnability, are extensively studied. The formation mechanism of the different morphologies of the nanotube arrays and the failure mechanism of the nanotube fibers are also discussed in detail.
authors.affiliation: School of Mechanical & Aerospace Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798, Singapore. lxzheng@ntu.edu.sg
authors.forename: Lianxi
authors.initials: L
authors.lastname: Zheng
authors.forename: Gengzhi
authors.initials: G
authors.lastname: Sun
authors.forename: Zhaoyao
authors.initials: Z
authors.lastname: Zhan
mesh_terms: D003460:Crystallization / Q000379:methods*; D055119:Elastic Modulus; D046911:Macromolecular Substances / Q000737:chemistry; D008422:Materials Testing; D008968:Molecular Conformation; D049329:Nanostructures / Q000737:chemistry* / Q000648:ultrastructure*; D036103:Nanotechnology / Q000379:methods*; D010316:Particle Size; D013499:Surface Properties; D013718:Tensile Strength
chemical_list: D046911:Macromolecular Substances