Research On Preparation And Properties Of Polyaniline-based Thermoelectric Materials

The development of wearable electronic devices has been in full swing since the 21 st century,which has great potential in medical monitoring,bionic prosthesis and other fields.The wearable electronic equipment can't operate without electric energy support.However,energy storage devices such as batteries and capacitors can not satisfy the needs of long-term battery life in military and medical surveillance since they have to be charged or replaced after running for a period of time.Under the action of temperature difference between human skin and the surrounding environment,thermoelectric generator converts human energy into electric energy,which becomes a potential choice for the continuous power supply of wearable devices.In this paper,a conductive organic compound polyaniline(PANI)was used as matrix because of intrinsic flexibility and low thermal conductivity,and the thermoelectric property was improved by adding a skutterudite with a high thermoelectric figure of merit.Doped PANI was synthesized by chemical oxidation method.The influence of different hydrochloric acid concentration on the structure and properties of PANI was investigated.The microstructure of PANI is in the shape of a nanometer rod with a diameter between 50 and 100 nm.With the increase of HCl concentration,the conductivity of polyaniline increased firstly and then decreased.Seebeck coefficient showed the opposite change law,and thermal conductivity decreased gradually.The maximum ZT value reached 3.3×10-6 at 300 K.Multiple-filled skutterudites were synthesized by annealing and melt-spinning respectively followed by hot-pressing process.The mechanism of phase transformation during the peritectic reaction of smelting samples was studied and the thermoelectric properties of the annealed and hot pressed samples with the same nominal filling amount and different filling atom species were tested.The result showed that increasing element species contributed to the improvement of the actual filling fraction.In addition,the component fluctuation was discovered in n type skutterudites.The filling behavior of some elements was related to the Fe content in the framework.The fluctuation of the total filling fraction led to the appearance of bright and dark areas in the skutterudite.Three reasons for the decrease of lattice thermal conductivity were elaborated: nanophase,rattling effect and strain field fluctuation.The effect of melt-spinning speed on the microstructure and properties of samples was investigated and it was found that higher melt-spinning speed could reduce the thermal conductivity.The thermoelectric properties of samples with different compositions by melt-spinning and hot-pressing were evaluated.The skutterudite with a high ZT value of 1.22 at 823 K was successfully prepared.Besides,the ZT value reached 0.25 at 323 K.Skutterudite/polyaniline composites were prepared by mechanical milling.The influence of different skutterudite content and hot-pressing temperature on the structure and properties of composite materials were studied.The ZT value of 10 wt.% skutterudite composites reached 7.39×10-5 at a molding temperature of 373 K,22 times that of polyaniline materials,and a theoretical power generation of 0.73 m W was achieved.