Fabrication And Thermoelectric Properties Of ZnO Nanowires Based MWNTs/PVDF And PANI/PVDF Thermoelectric Composite Materials

In recent years, along with the advance of nano science and technology, the use of nanosemiconductor materials with the characteristics of the low dimensions and larger specificsurface area to realized electricity and phonon transport property of coordinated control,optimizing the thermoelectric performance, to expand the research field of thermoelectricmaterials, development of higher heat efficiency, low cost, lightweight and stretch of newnanoscale thermoelectric materials research has become one of the important research projectsamong Europe, the United States, Japan and other countries.In order to develop new thermoelectric materials and realize the thermoelectricconversion, and for it can provide sustainable energy for the future of micro-nano mechanicaland electrical systems and electronic devices. Our work studied the ZnO nanowires basedMWNTs/PVDF, ZnO nanowires based PANI/PVDF and ZnO nanowires basedMWNTs/PANI/PVDF polymeric thermoelectric composite materials’ preparation process andthermal properties. My paper’s main work is as follows:(1) In this article, multi-walled carbon nanotubes (MWNTs) and polyvinylidene fluoride(PVDF) were ultrasonic mixed with different concentration. Then the MWNTs/PVDFmixtures were sprayed on the surface of n-type ZnO semiconductor nanowire arrays, and anew-type ZnO nanowire based MWNTs/PVDF thermoelectric composite materials wereprepared. Compared with the previous carbon nanotube/polymer thermoelectric materialsprepared using expensive p-type and n-type single-walled carbon nanotubes (SWNTs) andpolymer hybrid, the prepared ZnO nanowire based MWNTs/PVDF samples presentedexcellent thermoelectric properties. The one dimensional conducting pathways and goodelectrical conductivity of the nanotubes, and the higher carrier density and mobility of ZnOsemiconductor nanowires can effectively help enhance the electronic transport performance,also increase the intensity of the materials’ phonon scattering. The experimental results foundthat the thermoelectric voltage and conductivity increase with increasing the weightconcentration of MWNTs at a certain temperature gradient condition. And the amplitudeof variation of Seebeck coefficient is not too big for the whole range of tested temperature.Because of it didn’t change the characteristics of thermal conductivity of the material whenMWNTs dispersed in polymer to form the one-dimensional electronic transmissioncharacteristics and ZnO nanowires array, MWNTs as well as polymer formed the lots of interfacial potential barriers to enhance conductivity. The ZnO nanowire basedMWNTs/PVDF composite thermoelectric materials are promising to replace previousSWNTs/polymer thermoelectric composites.(2) The different proportions of polyaniline (PANI) mixed with polyvinylidene fluoride(PVDF), then sprayed the mixture on the surface of n-type ZnO semiconductor nanowirearrays, so a new-type ZnO nanowire based PANI/PVDF thermoelectric composite materialswere prepared. Based on multiple samples’ thermoelectric properties research ofthermoelectric voltage, seebeck coefficient, electrical conductivity and the output power, wefound that shown good thermoelectric properties. Added conductive polymers in polymer wecan make new type thermoelectric composite materials and enhance the thermoelectricproperties. Through analyzing we found that PANI particles dispersed in the polymer PVDFformed the interfacial potential barriers, limited the phonon conduction, reduced its thermalconductivity; As combined with conductive ZnO nanowires array, it increased the mean freepath of charge carriers transmission and transmission efficiency, it’s also advantageous to thecharge carriers’ ballistic transport through the grain boundary. These factors will havebeneficial effects of the electrical conductivity and Seebeck coefficient. This study suggests ithopes to develop the lightweight, non-toxic, low-cost and used in micro-nano electronicfields’ power supply of the new type thermoelectric polymer composites.(3) The different proportions of multi-walled carbon nanotubes (MWNTs) andpolyaniline (PANI) mixed with polyvinylidene fluoride (PVDF), then sprayed the mixture onthe surface of n-type ZnO semiconductor nanowire arrays, so a new-type ZnO nanowire basedMWNTs/PANI/PVDF new type thermoelectric composite materials were prepared. Based onthe test analysis of multiple samples’ comparison of different content of MWNTs and PANI,we found that the new type thermoelectric composite materials samples’ conductiveproperties and thermoelectric properties are better than the aforementioned thermoelectriccomposite materials’ of added single MWNTs or PANI. Through retrieval we found the newtype thermoelectric composite materials’ reports are still very few around the world at present,so my paper studys on the preparation and test work of the new type thermoelectric compositematerials to improve electrical conductivity and Seebeck coefficient and lowering thermalconductivity will have beneficial effects. Therefore, my study on the thermoelectric compositematerials will offered reference data for the application.