Preparation And Characterization Of Lignin-based Orientated Nanocarbon Functional Fibers

Lignin is a rich renewable natural organic resources,widely presenting in plants,and it is the world's second most abundant organic material only less to cellulose in nature.It can be used as a raw material for carbon fiber for its high carbon content.The main contents and results include the following three parts:?1?Lignin as the main raw material,mixed with polyethylene oxide?also known as polyoxyethylene,PEO?dissolved in formic acid,by electrospinning method to prepare lignin-based composite nanofibers and through the pre-oxidation and carbonization to obtain lignin-based carbonized fibers.The influence of solution concentration,receiving distance,positive voltage and rotation speed on the morphology of fibers was discussed.The results showed that the optimum spinning concentration was 20%.The optimum spinning parameters were-2kV negative voltage,20 kV positive voltage,15 cm receiving distance,1000r/min rotary speed.The fibers and the raw materials were characterized by FTIR,TG and DSC.The results showed that hydrogen bonds were formed between lignin and PEO.There was no phase separation between lignin and PEO in the fibers.?2?In order to prevent the fiber from melting and losing the fiber morphology during the carbonization process,it is necessary to pre-oxidize the composite fiber.The effects of air content,heating rate and temperature on the fiber during preoxidation were investigated.The results showed that the optimum preoxidation process in this experiment was that the temperature 300? the heating rate 2?/min and the heat preservation time 120 min.Then,the composite fibers were carbonized at 600°C,700°C,800°C and 900°C,respectively,at a heating rate of 5°C/min.The morphology,carbon content,fiber crystal form,carbon layer order and conductivity of preoxidized and carbonized fibers were characterized by SEM,TG,elemental analysis,XRD,Raman,conductivity and electrochemical measurements.The results showed that in the temperature range used in this experiment,the carbonized fibers were chaotic graphite structures,and the carbon structures are amorphous carbon.As the temperature increased,the carbon content and the electrical conductivity increased.The conductivity of the carbon fibers at temperature 900? is 4.316S/cm,and the specific capacitance is 35F/g.?3?Alikali lignin as the main raw material,mixed with PEO and nickel acetate?C₄H₆NiO₂·4H₂O?dissolved in formic acid,through the electrospinning method to prepare composite nanofibers and by pre-oxidation and carbonization to produce lignin-based functional carbon fibers.The fibers were preoxided at a rate of 2?/min,300? for 120 min in air atmosphere and then carbonized in nitrogen atmosphere at 5?/min heating rate and 800? for 300 min.The EDS,XRD,Raman,conductivity meter and electrochemical workstation were used to characterize the microstructure,crystal morphology,carbon layer order and electrical conductivity of the carbonized fibers.The results showed that there were granular substances on the surface of the fibers after carbonization,the Ni was mainly distributed on the surface of the fibers,the carbon fibers were chaotic graphite structure and the carbon structure was amorphous carbon.After carbonization,the nickel acetate is transformed into NiO and Ni.The electrical conductivity of the fibers was increased as compared with fibers without Ni.The electrical conductivity and the specific capacitance of the fibers was increased to 3.698S/cm and 59F/g.