Research On The Preparation And Performance Of High-Performance Graphene Fibers

As the one-dimensional macroscopic assembly of graphene,graphene fibers are potentially used in the fields of flexible electronic devices,multifunctional fabrics,biomedicine,aerospace,national defense and so on.Due to their excellent electrical conductivity,thermal conductivity,and outstanding mechanical properties,graphene fibers have aroused the interest of thousands of scientists.Graphene oxide(GO)fibers are often processed by high-temperature thermal reduction to restore the structural defects of the graphene nanosheets caused by oxidation and realize the high mechanical strength and electrical conductivity of the graphene fibers.Although the hightemperature treated graphene fibers exhibit extremely high tensile strength and Young’s modulus,their elongation at break and toughness are quite poor,giving typical hard.and brittle characteristics,which limits their applications in the aspects of flexible electronics or functional fabrics.On the other hand,the temperature of thermal reduction generally reaches above 2000℃,consuming considerable energy and time,which is not beneficial to the efficient preparation of graphene fibers.Therefore,how to fabricate graphene fibers with both high tensile strength and high toughness via simple and efficient methods,has become a huge challenge in the current research on high-performance graphene fibers.Therefore,low-defect graphene oxide nanosheets(SGO)prepared by the modified Staudenmaier method are used as raw materials,and highperformance reduced graphene oxide fibers(RSGOFs)are prepared via a feasible preparation method and efficient reduction strategy,which is low energy-consumption without high-temperature treatment,greatly speeding up the preparation process,broadening the channels for improving the performance of graphene fibers,and providing new ideas for promoting the low-cost and efficient preparation of graphene fibers.The main contents of this work are as follows:1.Using the modified Staudenmaier method to prepare SGO at low temperature,the liquid crystal(LC)texture of SGO dispersions at different concentrations was systematically observed,and the GO dispersions prepared by the modified Hummer’s method and the Staudenmaier method were compared in terms of rheological properties and chemical compositions.It is noted that,compared with HGO,the surface of SGO nanosheets has fewer wrinkles due to the grafting of fewer oxygenated groups,and exhibits stronger sheet rigidity.Therefore,it is conducive for SGO nanosheets to expand the LC region,thereby promoting the flow orientation of the nanosheets,and improving the mechanical properties of the macroscopic fibers.2.Using water as the dispersant and acetic acid as the coagulation bath,the system is relatively safe,and the wet spinning of the small-layer SGO dispersions is realized to obtain the SGO fibers(SGOFs)with both high tensile strength and excellent toughness.The focus is on the effects of coagulation bath,needle diameter,drawing ratio and other experimental conditions on the fiber properties,and the fracture mechanism of SGOFs is explored.Without additives and no post-stretching,spinning with a 24G needle,the acquired SGOFs exhibit a maximum tensile strength of 638.2 MPa,a toughness of 20.8 MJ m-3,and fatigue resistance to some extent.3.To further optimize the arrangement and orientation of the SGO nanosheets along the fiber axis,needles of 27G are used and the ratio of the rotation speed of the coagulation bath to the injection speed is adjusted to control the drawing ratios.Also,the morphological structure,orientation degree,and mechanical properties of SGOFs have been deeply studied.It is found that when the drawing ratio is 1.75,the internal lamellar orientation of SGOFs is highly improved,the tensile strength is up to 791.7±96.1 MPa,and the toughness is 8.3±2.0 MJ m’3,laying a solid foundation for the subsequent preparation of high-performance reduced graphene oxide fibers.4.Using a mild and simple low-temperature-"high temperature" chemical reduction method to reduce SGOFs,the time and the temperature of different stages were controlled to fabricate reduced graphene oxide fibers(RSGOFs)with excellent electrical conductivity and mechanical properties.Benefiting from the low defective degree on the surface of SGO,the tensile strength of RSGOFs is as high as 875.9±15.6 MPa,and the electrical conductivity is increased to 1056.6±56.9 S cm-1,outperforming the mechanical strength and conductivity values of chemically reduced GO fibers in the previous reports.After multiple cyclic tensile cycles,RSGOFs still retain high electrical conductivity and mechanical strength,which is promising in applications of wearable electronic devices and smart fabrics.