Performance improvement of continuous carbon nanotube fibers by acid treatment

Zhang Qiang^{1, 3}, Li Kewei¹, Fan Qingxia^{1, 3}, Xia Xiaogang^{1, 3}, Zhang Nan¹, Xiao Zhuojian^{1, 3}, Zhou Wenbin¹, Yang Feng^{1, 3}, Wang Yanchun^{1, 2, 3}, Liu Huaping^{1, 2, 3}, Zhou Weiya^{1, 2, 3, †}

(color online) Influences of acid treatment on the twisted fiber’s performance. (a) Tensile strength and (b) electrical conductivity at different acidizing time. (c) The typical stress–strain curves and (d) Raman spectra of the sample at different acidizing time (5 hours for H₂SO₄ and HCISO₃, 2 hours for HNO₃). Inset of panel (d) shows blue shifts of the G band after acid treatment. The D band intensity greatly increases after immersion of the fiber in HNO₃ for 2 hours. All Raman spectra are normalized by the G band intensity.