Preparation Of Pani-Based Thermoelectric Composites And Their Properties

Thermoeletric (TE) materials have drawn great attentions due to their potential applications in waste heat recovery systems, air conditioning and refrigeration. In comparison with traditional alloy-based thermoelectric materials, conducting polymers, which are of abundant supply, inexpensiveness, low intrinsic thermal conductivity and easy preparation, are excellent candidates for TE materials. However, their low Seebeck coefficients, lead to low comprehensive TE properties, limiting their applications in practice.The dissertation is focused on improving TE properties of conducting polyaniline (PANI) by a simple and effective method. PANI, used as the matrix, was uniformly mixed with different TE oxides particles by ball-milling. Compact bulk composites were successfully fabricated via a hot-pressing route, and their TE properties were studied, which were affected by ingredient, filler content, and interfacial combination of filler and matirx.P-type Ca3Co4O9powder was obtained via a sol-gel method. After ball-milling, agglomerations of Ca3Co4O9were broken, then Ca3Co4O9was dispersed uniformly into PANI matrix. By hot-pressing Ca3Co4O9and PANI were physically combinedl to ensure compact bulks. There are few voids between filler and matrix, unless Ca3Co4O9content is above30wt%. In control of Ca3Co4O9content, Seebeck coefficient and thermal conductivity of the composites are improved, thus the ZT value is40times greater than that of pure PANI.P-type BiCuSeO powder was obtained via a solid-reaction method. After ball-milling and hot-pressing, BiCuSeO particles were evenly imbedded in PANI matrix, to form bulks. Microscopic analysis demonstrates that the physical combination of BiCuSeO and PANI is better than that of Ca3Co4O9and PANI due to the coarse surface of BiCuSeO crystals. There are seldom voids for BiCuSeO/PANI composites, even when the filler content is as high as40wt%. Therefore, Seebeck coefficient of BiCuSeO/PANI composites has improved dramatically, and the electrical conductivity and thermal conductivity change slightly, thus the ZT value is500times greater than that of pure PANI.N-type CaMnO3powder was obtained via a co-precipitation method. The combinations of CaMnO3and PANI were very bad. There is no improvement in the TE performance of CaMnO3/PANI composites. The ZT value of40wt%sample is less than one percent of pure PANI. The main reason lies that CaMnO3and PANI have different types of carrier.