Properties Of The Thermoelectric Composites Based On Carbon Nanotube Film/Conductive Polymer

Thermoelectric（TE）material is a kind of environment-friendly material which can realize the direct conversion between heat energy and electric energy.It has great application potential in the fields of TE power generation and refrigeration.Compared with traditional inorganic TE materials,conductive polymers have the advantages of good flexibility,light weight,low thermal conductivity,and are often used to prepare flexible TE materials.However,the low TE propertis of conducting polymers limites its large-scale application.Carbon nanotubes（CNTs）have outstanding mechanical and conductive properties,and are often used to combine with conductive polymers to prepare flexible TE materials.The traditional CNT powder or dispersion has poor orientation and easy aggregation in polymer matrixes,which seriously limits the enhancement of the TE performance of CNT/conductive polymer composites.In this study,floating catalytic chemical vapor deposited fabricated carbon nanotube film（CNTF）was used to combine with three typical conductive polymers,poly（3,4-ethylenedioxythiophene）-poly（styrenesulfonate）（PEDOT:PSS）,polypyrrole（PPy）and polyaniline（PANI）,for prepararion of the corresponding composites,respectively.The main research contents are as follows:（1）Flexible self-supported CNTF/PEDOT:PSS composites were prepared by using vacuum filtration method.The influence of different content of PEDOT:PSS in PEDOT:PSS/ethanol mixed solution on the TE properties of CNTF/PEDOT:PSS composites was studied.At 320 K,the maximum power factor of CNTF/PEDOT:PSS composite with 60wt%PEDOT:PSS content（S2）was 339.6μWm^-1K^-2,which was 1.5 times that of CNTF(223.3μWm^-1K^-2 at 320 K).The tensile strength and Young’s modulus of S2 were 1.6 and 1.0 times that of CNTF,respectively.Then S2 was post-treated with ethylene glycol,and the effects of treatment times on the TE properties were studied.It was found that the Seebeck coefficient and power factor of S2 treated with ethylene glycol for 1 h were up to 73.1μV/K and 419.7μWm^-1K^-2 at 340 K.（2）Flexible self-supported CNTF/PPy composites was prepared by in-situ polymerization method.The effects of pyrrole concentrations on the TE properties of CNTF/PPy composites were studied.At 300 K,the Seebeck coefficient,electrical conductivity,and power factor of CNTF/PPy composites with the pyrrole concentration of 0.2 mol/L were 48.4μV/K,1578.5S/cm and 369.2μWm^-1K^-2,respectively.The power factor was about 2 times that of CNTF(191.2μWm^-1K^-2 at 300 K).In addition,the tensile strength and Young’s modulus of CNTF/PPy-0.2 composites were 3.9 and 2.1 times that of CNTF,respectively.（3）Flexible self-supported CNTF/PANI composites was prepared by in-situ polymerization method.The effect of polymerization time of PANI on the TE properties of CNTF/PANI composites was studied.It was found that CNTF/PANI-5 composites prepared with PANI polymerization time of 5 h obtain the highest TE performance.At 360 K,the Seebeck coefficient and power factor of CNTF/PANI-5 composite increased to 63.3μV/K and536.8μWm^-1K^-2,respectively.The power factor was about 3 times that of CNTF(181.7μWm^-1K^-2 at 360 K).In addition,tensile strength,Young’s modulus,and toughness of CNTF/PANI-5 composites were 3.5,2.6 and 2.1 times that of CNTF,respectively.