Continuous Preparation Of Graphene Fibers

Graphene is an unique two-dimensional crystal material with excellent mechanical,electrical and thermal properties.These properties of graphene have broad applicationprospects in the fields of matrix reinforcement,thermal and electrical conductivity and sensor.The research of graphene fiber is a hot topic in the field of graphene in recent years.However,there has always been a challenge in the study of graphene fibers: how to convert graphene sheets into fibrous graphene macrostructures.As a highly soluble graphene derivative,graphene oxide(GO)as precursor of graphene provides the possibility for graphene fibers to be prepared through wet spinning.At present,the research on the preparation of graphene fibers by wet spinning has made some progress.However,there were still some challenges in easiness and simplicity of the preparation.It is first presented in this paper that GO fiber formation based on coagulating mechanism through salification.The GO aqueous dispersion was treated with ammonia,and the dispersibility of GO was improved.On the other hand,in the process of wet spinning,de-protonated GO can form salts with ammonium ions and precipitate out,realizing the continuous preparation of GO fiber.Finally,the continuous graphene fiber was obtained by chemical reduction of GO fiber.The main research details and conclutions are as follows:(1)Large size GO was prepared by modified Hummers method.The small size GO was removed through static stratification and GO suspension with large size,narrow distribution and high concentrations was finally prepared.(2)The effect of pH on the deprotonation of GO was investigated.The research results showed that with the increase of pH,the degree of protonation of GO increases,and when the pH increased to 11,the degree of deprotonation of GO is the highest,leading to the best dispersibility of GO.And when the pH of the dispersion continues to increase,the protonation degree of GO is difficult to increase,because the protonated GO would combinewith surplus alkaline cations to form salts.On this basis,we use ammonia as a pH regulator to regulate the deprotonation degree of GO,and finally obtain a well-dispersed GO suspension.(3)A new coagulating mechanism based on salt formation was put forward for the first time to realize easily the continuous preparation of GO fibers by wet-spinning.Just with the addition of a tiny amount of ammonia to GO aqueous solution,dispersibility of GO sheets was efficiently enhanced in the aqueous solution with high pH through de-protonation of GO sheets.Meanwhile coagulating effect of GO fiber was largely improved through the combination of de-protonated GO sheets with ammonium ions to form salts in a newly developed mixture coagulant of methanol and acetone.In this way,GO fibers could be prepared continuously.The obtained GO fiber showed good mechanical properties,while the reduced fiber had much better tensile strength and good electrical conductibility.