Researches On Preparation And Properties Of Carbon Material/Polymer Composite Thermoelectric Materials

Thermoelectric(TE)devices can convert heat into electrical energy through the Seebeck effect or cooling through the Peltier effect.TE devices made of TE materials have many advantages,including no pollution,small size,no noise,high reliability,and no moving parts.Carbon nanomaterials have high electrical conductivity and large specific surface area,which have received extensive attentions in TE materials field.3D printing technology,also known as rapid prototyping technology,has the advantages of designability,easy operation,strong applicability,and is suitable for preparation of flexible polymer-based TE materials,whereas few studies have been reported.In this thesis,solution 3D printing process was used to prepare carbon material/polymer composite TE materials.The main conclusions are as follows:(1)MoS₂/SV4 composite TE materials with different MoS₂ content were prepared by a solution 3D printing process,and the composition,microstructure,and TE properties of the composite materials were studied.The results showed that with the content of MoS₂ increasing,the electrical conductivity of the MoS₂/SV4 composites decreased,while the Seebeck coefficient was remained constant.At 360 K,a power factor of 1.2?W/m K² was obtained when the content of MoS₂ was 68.97 wt%.Graphene(GR)was added into the above-mentioned MoS₂/SV4 composite materials,and GR/MoS₂/SV4 composite TE materials were prepared by the same method.It was found that as the content of GR increasing,the Seebeck coefficient of GR/MoS₂/SV4 composite TE materials was basically unchanged,while the electrical conductivity first enhanced and then decreased.At 360 K,a highest power factor of 1.78?W/m K² was obtained for the composite material when the content of GR was 17.1 wt%.When the radius of curvature was 3.02 mm,after being bent for 300 times,the resistance changes rate of the GR/MoS₂/SV4 composite was 5.2%.(2)Single-walled carbon nanotube(SWCNT)/SV4 composite thermoelectric material was prepared by a solution 3D printing process,and the compositions,microstructures and thermoelectric properties of the composite materials were studied.At room temperature,when the volume addition ratio of SWCNT and SV4 is 1:1,the power factor of the SWCNT/SV4composite TE material was 9.19?W/m K².After adding poly(3,4-ethylene dioxythiophene):polystyrene sulfonic acid(PEDOT:PSS),the SWCNT/PEDOT:PSS/SV4composite TE materials were further prepared by the same process.With the volume addition ratio of SWCNT and PEDOT:PSS increasing from 0.5:1 to 5:1,the Seebeck coefficient of the SWCNT/PEDOT:PSS/SV4 composites gradually increased,and the electrical conductivity was first increased and then decreased.When the volume addition ratio of SWCNT and PEDOT:PSS is 1:1,a power factor of 38.51?W/m K² was achieved at 300 K;as the temperature increased from 300 K to 360 K,the electrical conductivity was basically unchanged,while the Seebeck coefficient gradually increased,a maximum power factor of 47.42?W/m K² was obtained at360 K for the SWCNT/PEDOT:PSS/SV4 composite.When the volume addition ratio of SWCNT and PEDOT:PSS is 1:1,the resistance changes rate of the ternary composite was 1.6%after being bent for 300 times at a bending radius of 3.02 mm.(3)The prices of both the SWCNT dispersion and SV4 slurry are high.Considering the economic factors,acrylonitrile-butadiene-styrene(ABS)resins and multi-walled carbon nanotubes(MWCNTs)were used to prepared the TE composite materials.MWCNT/ABS composite TE materials with different MWCNT content were prepared by a solution 3D printing process,and the composition,microstructure and thermoelectric properties of the composite materials were studied.It was found that with the content of MWCNT increasing,the power factor of the MWCNT/ABS composites first increased and then decreased,at 340 K,a power factor of 0.3?W/m K² was obtained for the MWCNT/ABS composite when the content of MWCNT was 37.5 wt%.After being bent for 300 cycles at a curvature radius of 8.1 mm,the resistance changes rate of the MWCNT/ABS composite with 37.5 wt%MWCNT was 3.9%.Moreover,ternary BST/MWCNT/ABS composite materials with different content of bismuth telluride alloys(BST)were prepared by the same process,when the BST content was 20 wt%,the ternary BST/MWCNT/ABS composite obtained a power factor of 7.35?W/m K² at 360 K.