One-step Pyrolysis Carbon-based Nanocomposites And Its Application In Microwave Absorption And Electrochemistry

Carbon nanotubes and graphite are widely known for high electrical conductivity,high strength,high elasticity,high aspect ratio,large specific surface area and high absorption.Introduced iron compounds?Fe₃O₄/Fe₃C?to carbon-based nanocomposites containing carbon nanotubes or graphite,that combined the advantages of both carbon nanomaterials and metal compounds.In this paper,ferrocene-based polymer?PDPFDE?synthesized in our previous work used as the raw material,a new type of carbon-based nanocomposite was prepared by one-step thermal pyrolysis of PDPFDE.The effects of the temperature and time of pyrolysis on its structure were explored,and also investigated application of carbon-based nanocomposites in wave absorption and supercapacitor.The detailed research is as follows:1)In this paper,we prepare carbon-based nanocomposites by one-step pyrolysis of PDPFDE,the structure of carbon-based nanocomposites at different pyrolysis temperatures?550°C-2h,650°C-2h and 750°C-2h?and different pyrolysis times?650oC-1h,650°C-2h and 650oC-3h?were discussed.Among all carbon-based nanocomposites,650°C-2h carbon-based nanocomposites that with the best morphology can be preliminarily determined by SEM,TEM,and XRD analysis.650°C-2h carbon-based nanocomposite contains two special carbon materials of multi-walled carbon nanotubes and graphite,and also formed Fe₃O₄ and Fe₃C phases due to the carbonization of the ferrocene-containing polymer,and its composition is C@Fe₃O₄/Fe₃C/MWCNTs.In addition,Raman showed that the I_D/I_G values of 550°C-2h,650°C-2h and 750°C-2h decreased with increasing temperature,and the degree of graphitization increased.2)X wt%of the carbon-based nanocomposite and?1-X?wt%paraffin matrix are mixed and stirred to make a mold,and then tested the absorbing performance.RL properties,electromagnetic properties,?"-?'curves,attenuation constants?,?''??'?^-2f^-11 curve and Z value of carbon-based nanocomposites were calculated.The two key factors of pyrolysis temperature and pyrolysis time were studied to affect the absorbing performance by influencing the structure.When discussing the effect of different pyrolysis temperatures on the wave absorbing performance?X=40 wt%,550°C-2h,650°C-2h and 750°C-2h?,a minimum RL value?=Maximum absorption?of-40.32 dB was observed at 12.50GHz for 650°C-2h carbon-based nanocomposite with a coating thickness of 2 mm,and effective absorption bandwidth?denoted as EAB?is 3.5GHz.Dielectric loss act as the main loss mechanism of the 650?-2h carbon-based nanocomposite,the high-performance microwave absorption properties of 650oC-2h carbon-based nanocomposites is owing to the good impedance matching and the synergistic effects of magnetic loss,dielectric relaxation loss,conduction loss,and multiple scattering.3)Carbon-based nanocomposite electrode was successfully prepared with 650oC-2h carbon-based nanocomposite:carbon black:polyvinylidene fluoride?PVDF?=8:1:1,and three-electrode system was used for cyclic voltammetry?CV?,galvanostatic charge/discharge tests?GCD?,electrochemical impedance spectroscopy?EIS?and cyclic stability test to study its electrochemical performance.When the current density is 1 A/g,2 A/g,5A/g,10 A/g,and 20A/g,the data of GCD curves show that the specific capacitances of 650°C-2h carbon-based nanocomposites are 443 F/g,385 F/g,208 F/g,159 F/g and 123 F/g,respectively.After 1200charge and discharge cycles when the the current density is 5A/g,the specific capacitance of the 650°C-2h carbon-based nanocomposite electrode is reduced to 153F/g.