The Crystallization Of Amorphous Carbon Fiber And In-situ Growth Of Carbon Nanotubes On Their Surface At Ambient Temperature And Pressure

Extensive attentions have been paid to carbon fibers since their specific mechanic properties,chemical stability,and wide application,and more and more people set to study their surface treatment and modifying recently.Carbon nanomaterials occupy a pivotal position in nanotechnology research because of its unique properties.Carbon nanomaterials have small size effect,surface effect,quantum size effect with nanometer materials and good photoelectric characteristics of carbon materials,such as the excellent performance.It will greatly influence the research of next new generation aerospace materials and electronic equipment.In this paper,a new method("electrochemical method)successfully completed the preparation of carbon nanomaterials.Here,the difference is that two traditional electrodes were connected by carbon fiber(s),which acted as heating source and substrate which the as-prepared coating can grow in-situ on.Besides,the electrolyte not only can be used as a chemical source and quenching medium,but as an isolation medium to avoid the high temperature oxidation of carbon fibers.Their composition and morphology were characterized by High resolution transmission electron microscopy(HRTEM),Scanning electron microscopy(SEM),Raman spectroscopy,Energy dispersive spectroscopy(EDS),respectively.We use ethylene glycol as the electrolyte and single carbon fiber as reaction substrate during the method.CNTs with 3D net-like structure were successfully gown on C fiber without using any catalyst by“electrochemical”method.the influences of processing parameters on their morphology and crystallization were mainly discussed,including voltage condition,reaction time,and electrolyte concentration.The research results show that only at the right time,under the appropriate of voltage,using suitable concentration of electrolyte,can produce carbon nanotube coating "rith good quality.The formation and growth of CNTs are strongly influenced by applied voltage and reaction time,while our synthesis system can provide a suitable heating temperature and desired temperature gradient for their in situ growth.A growth mechanism of carbon nanotube on carbon fiber was proposed,based on variation of carbon nanotube growth with processing parameters and unique structure of our design.We think the region around glowing C fiber can be divided into three parts.This paper discusses the temperature gradient and pentagonal and heptagonal C rings for the synergy of carbon nanotubes formation.We discuss the difference of the optimal process conditions when using glycerol as electrolyte because of its special physical properties(higher relative density,surface tension and high viscosity).The influences of processing parameters on their morphology and crystallization were mainly discussed,including voltage condition,reaction time.Research shows that,through the adjustment of process parameters,the preparation of carbon nano-materials is not restricted by the electrolyte type,so the method has a broad application prospect.Crystal phase transition which amorphous carbon to diamond and graphite successfully be prepared under the condition of atmospheric pressure.The system overcomes the energy barrier because of the resistance of the carbon fiber.We effectively save the diamond of metastable phase by quickly cut off power supply and rapid quenching.The nano diamond particles have a regular shape,distribute evenly in carbon fiber.It is accompanied by certain graphite formation.By discussing the influence of the reaction time of crystallization,prolong the reaction time can lead to the diamond into graphite phase.Further proves that quenching is a key element.And the electrical testing shows that the unit of resistance in the diamond phase generated part of the decline,and fully graphitization decreased significantly,to explain the reaction happen.