Preparation And Properties Of MWNTs/Cu₂O/PVDF, PANI/Cu₂O/PVDF And PANI/PTh/PVDF Thermoelectric Composites

According to thermoelectric effects of materials, making use of the temperature gradient and remaining heat, can realize the thermoelectric conversion, which is a practical solution to provide sustainable energy for micro/nano-electromechanical systems and electronic devices and some low-power electricity systems, and to solve the question of energy sources.Metal oxide thermoelectric semiconductor material having excellent structural stability and chemical stability. At high temperatures, it has good antioxidant properties. It also has the features of long life, safe, non-toxic and simple preparation. The metal oxide compositing with polymer materials, is expected to fabricate a flexible, inexpensive, a good conversion thermoelectric characteristic of new thermoelectric materials. It will have great potential applications in waste heat utilization of boiler which is high temperature thermoelectric power generation applications.Recently, conducting polymers have attracted much attention, which has high conductivity and good environmental stability, is considered to be new thermoelectric materials which has potential development and utilization prospects. In order to develop new thermoelectric conversion materials, carbon nanotubes can be composited with conductive polymer. Combining the good conductivity of carbon nanotubes with the low thermal conductivity and good flexibility of polymer, the better thermoelectric conversion features of thermoelectric materials can be prepared.Based on the current research, multi-walled carbon nanotubes(MWNTs), cuprous oxide(Cu2O), polyaniline(PANI) and polythiophene(PTh) conductive polymer are composited with polyvinylidene fluoride(PVDF) respectively, MWNTs/Cu2O/PVDF, PANI/Cu2O/PVDF,PANI/PTh/PVDF three kinds of new composite thermoelectric materials films are prepared.We study the influence of all kinds of component ratio and the preparation process of composite thermoelectric materials, and find the best preparation technology and formula of three new kind of composite thermoelectric materials films. The results of the study have important reference values which explores the development of new thermoelectric materials.This thesis mainly works as follows:(1) By using the method of solution blending, a new type of MWNTs/Cu2O/PVDF composite thermoelectric materials is prepared, the different proportions of MWNTs and Cu2 O were respectively mixed with PVDF, MWNTs/PVDF acts as n-type layer,Cu2O/MWNTs/PVDF serves as a p-type layer, and PVDF acts as an insulating layer, the experiment test and theory analysis to the optimal allocation ratio and thermoelectric properties are carried on. The purpose of mixing with a small amount of MWNTs in Cu2 O and compositing with polymer as the p-type layer is to use the p-type conductive properties of Cu2 O and the one dimensional electron transport properties of MWNTs, and improve the transport of the electrons in the composite thermoelectric materials. At the same time, the n-type layer MWNTs/PVDF film and the p-type layer overlap and combine. This improves thermoelectric optimal value of the thermoelectric materials and the thermoelectric potential under a certain temperature gradient. Experiments show that the biggest thermoelectric voltage is 340.03 mV in the 1:1 mass ratio of n-type layers MWNTs/PVDF and the 8:1:1 mass ratio of p-type layers Cu2O/MWNTs/PVDF thermoelectric composite material samples at38.4K temperature gradient.(2) Take advantage of solution blended process, respectively the different proportions of PANI and PVDF polymer blend as the n-type layer, with different proportions of Cu2O/MWNTs/PVDF blend as a p-type layer, using PVDF as the middle insulation, preparing a new type of PANI/Cu2O/MWNTs/PVDF composite thermoelectric materials. The comparative study found that, the PANI/Cu2O/MWNTs/PVDF thermoelectric composite optimal value and other parameters were significantly better than that of MWNTs/Cu2O/PVDF composite thermoelectric materials, is expected to be promoted in the field of new thermoelectric materials. Experiments show that the biggest thermoelectric voltage is 187.67 mV in the 9:1 mass ratio of n-type layers PANI/PVDF and the 8:1:1 mass ratio of p-type layers Cu2O/MWNTs/PVDF thermoelectric composite material samples at38.4K temperature gradient.(3) In order to further improve the Seebeck coefficient of thermoelectric materials and thermoelectric power optimal value, the different proportions of PANI/PVDF as n-type layer remains the same, the p-type layer will be replaced by different proportion of PTh/PVDF.Experiments show that PANI/PTh/PVDF composite thermoelectric materials’ Seebeck coefficient and optimal values are significantly higher than that of the two kinds of thermoelectric materials. Experiments show that the biggest thermoelectric voltage is 2.749 V in the 9:1 mass ratio of n-type layers PANI/PVDF and the 12:1 mass ratio of p-type layers PTh/PVDF thermoelectric composite material samples at 57.1K temperature gradient, the order of magnitude of the open circuit voltage vastly improve. Studies have shown that it can be more laminated thermoelectric devices through the series parallel combination, composed of composite structure.