Study On The Fabrication And Properties Of Aligned Carbon Nanotube/Inorganic Oxide Hybrid Fibers

Since the successful fabrication of carbon nanotube（CNT）fibers in 2000,they have attracted a wide range of research interests.They have not only high specific strength and high specific modulus,but also high toughness and large fracture energy absorption ability,as well as better electrical performance.Although CNT fibers have unique structural and functional properties,they are not inherently multifunctional.Therefore,the functionalization of CNT fibers to obtain a broader application is one of the most important issues to be addressed.In recent years,the CNT/inorganic oxide hybrid materials have attracted wide attention in the field of CNTs research.These hybrid materials not only have the performance of each component materials,but also have many peculiar properties,which are not belonging to the components.Therefore,the incorporation of inorganic oxide into the CNT fiber to make full use of the synergistic effect between the aligned CNTs and the inorganic oxide at the interface is an effective means to realize the multifunctional characteristics of the CNT fiber.In this paper,the preparation,composition and properties of CNT/inorganic oxide hybrid fibers including MnO₂/oxidized CNT hybrid fibers,aligned CNT/Al₂O₃ and aligned CNT/TiO₂ hybrid fibers were studied.In the first part,the oxidized CNT fibers with a more roughened surface and containing more oxygen-containing functional groups were prepared by soaking the pristine CNT fibers in an oxidizing solution.In order to further improve the electrochemical performance of the oxidized CNT fibers,MnO₂ nanoparticles were deposited on the fiber surface by liquid alcohol reduction reaction.The specific volumetirc capacitance of the prepared MnO₂-OCF-2 fiber reaches ⁴31.9 F cm-3 at a current density of 3.77 A cm-3.In order to evaluate the potential application of MnO₂/oxidized CNT fiber as a fiber electrode for stretchable fiber supercapacitors,we selected MnO₂-OCF-2 fiber which has the highest capacitance in the three-electrode system to assemble the supercapacitor.The supercapacitor assembled by prestraining-then-buckling method delivers a specific volumetric capacitance of ⁴09.4 F cm-3 at 0.75 A cm-3,which is 33 times of the pristine CNT fiber based fiber supercapacitor.In addition,the supercapacitor can be stretched up to 40% and folded under multiple cycles without compromising its electrochemical stability.In this part,the potential applications of MnO₂/oxidized CNT fibers in wearable supercapacitors are explored.In the second part,a series of aligned CNT/Al₂O₃ and aligned CNT/TiO₂ hybrid fibers with controlled oxide layer thickness were prepared by atomic layer deposition（ALD）technique.The deposition rate of ALD-Al₂O₃ was 0.12 nm/cycle and the deposition rate of ALD-TiO₂ was 0.24 nm/cycle.The tensile strength of the aligned CNT/TiO₂ hybrid fibers had no obvious change with the increase of the atomic layer deposition cycles,while the tensile strength of the aligned CNT/Al₂O₃ hybrid fibers increased with the increase of Al₂O₃ thickness,rising from 0.92 GPa to 1.1 GPa.Compared with the pristine CNT fibers,the electrical conductivity of CNT/Al₂O₃ hybrid fiber（1000 cycles）and CNT/TiO₂ hybrid fiber（715 cycles）decreased by 33% and 28%,respectively.The strength retention of the CNT/Al₂O₃ hybrid fibers（1000 cycles）was increased by 11.6% and 13.2%,respectively,after 1 h treatment at 800 oC and 1000 oC in argon atmosphere.The strength retention of CNT/TiO₂ hybrid fibers（715 cycles）increased by 11.4% and 12.1%,respectively,comparing with the pristine CNT fibers.This part of the research laid the foundation for the application of aligned CNT/Al₂O₃ and aligned CNT/TiO₂ hybrid fiber in advanced fiber reinforced composites.