Research On Synthesis And Formation Mechanism Of Carbon Nanotube Fiber And Composite Conductive Elastomer Electrical Performance

Due to gorgeous mechanical and electrical properties,carbon nanotube?CNT?fibers attract the attentions of researchers worldwide.In this paper,CNT fibers were synthesized via floating catalyst chemical vapor deposition and formation mechanism of CNT fibers were studied by thermodynamic and growth mechanism analysis;based on different catalyzing system,the influence of injection rate,C/Fe molar ratio,and addition of ferric chloride on morphology and purity of CNT fibers were investigated;furthermore,the electrical properties of the composite elastomer based on CNT fibers were explored.With ethanol,ferrocene,thiophene,and deionized water working as reaction materials,the nucleation growth mechanism of CNT and the formation mechanism of CNT fibers in this process were investigated.The pyrolysis of feedstock was analyzed through thermodynamic analysis and the results showed that the vapor carbon source was supplied by CO in high temperature.Based on the observation of experimental phenomena,the formation process of CNT fibers was divided into three parts:?1?Fe nanoparticles were free from pyrolysis of feedstock and then C atoms dissolved,namely the nucleation of CNT;?2?C atoms were in highly-supersaturation state and precipitated from Fe nanoparticles to form CNT,namely growth of CNT;?3?long CNTs deposited on the inner wall of alundum tube and Fe catalyst nanoparticles could float in the gas flow catalyzing the growth of ultra-long CNT,then ultra-long CNTs assembled together,namely the formation of CNT fibers.A novel formation mechanism of CNT fibers was proposed as the"deposition-float-assembly"?D-F-A?formation mechanism.The effects of injection rate and C/Fe molar ratio of raw material on morphology and purity of products were investigated using ferrocene as catalyst.The results showed that when the injection rate was 30 mL/h and the raw material C/Fe molar ratio was 523,CNT fibers were obtained stably.There were little sedimentation of catalyst using ferrocene as the catalyst preparing CNT fibers.Thus,ferric chloride was introduced and cooperated with ferrocene to co-catalyze the growth of CNT fibers.The nucleation and growth mechanism of CNT and influence of amount of ferric chloride in this reaction system were also investigated.The results showed that when 0.1 mL ferric chloride was added,the CNT fibers with high aspect ratio were synthesized and the purity of them was up to 97.64%.In the ferrocene and ferric chloride co-catalyst system,Fe free from pyrolysis of catalysts reacted with C to form Fe₃C.C dissolved and penetrated into the metal phase of Fe,and then precipitated from the metal phase to form a graphite layer,catalyzing the nucleation and growth of the CNT fibers.CNT fiber/polydimethylsiloxane?PDMS?composite conductive elastomer was fabricated and the mechanical and electrical properties were studied.The results of mechanical tensile and electrical property tests showed that the maximum tensile stress of the composite conductive elastomer was up to 0.25 MPa,and the maximum tensile strain was 48.9%.Furthermore,the resistance was 0.228 k?without straining,showing good strain sensitivity.The repeatability was great over 180 times stretching-and-releasing cycles up to a prestrain level 6%and showed very little variation within the tensile strain range of 10-25%,indicating the promising application prospect as flexible wire.In conclusion,CNT fibers were synthesized via floating catalyst chemical vapor deposition.Based on the preparation process,we proposed the D-F-A formation mechanism,synthesized the CNT fibers/PDMS composite conductive elastomer,and explored the excellent mechanical and electrical properties of the composite elastomer,contributing to the development of continuous spinning of the CNT fibers and the application of CNT fibers-based composite materials.