Study On Preparation And Properties Of Carbon-based Composite Thermoelectric Fibers

Thermoelectric technology based on the Seebeck effect provides a unique method to directly convert heat to electrical energy without causing environmental pollution.The maximum electric potential for this electric energy generation way mainly depends on the energy conversion efficiency of the thermoelectric material and actual temperature difference between the hot and the cool ends.The human body,like a continuous constant temperature source,has the potential to provide an inexhaustible energy,if the heat loss can be collected and converted effectively.The electricity generated by the huge population on the earth is quite considerable.It can be directly used to drive the wearable electronics operation and even collected to make up the shortfall in demand for electricity.Therefore,more and more studies have focused on wearable thermoelectric materials for the human body.The inorganic thermoelectric materials usually have high Seebeck coefficient and poor flexibility,and the organic thermoelectric materials are the opposite.One possible way to achieve high performance thermoelectric materials combined with high Seebeck coefficient and flexibility is to design organic-inorganic composite materials.Thermoelectric fibers are easily integrated into flexible textile by mature weaving technologies,due to their unique one-dimensional morphology.As this point it seems that development of thermoelectric fiber is a promising way to apply thermoelectric technology into wearable electronic devices.In this paper,two kinds of flexible and stretchable carbon-based thermoelectric fiber are prepared,which can generate electricity by using temperature difference between human body and environment,and be used as self-power sensor.The main results are as follows:1.Flexible and stretchable carboxylated single-walled carbon nanotube-based thermoelectric fibers are prepared by improved wet-spinning method.The Seebeck coefficient of the thermoelectric fiber remains stable at a tensile strain of about 30%.When the tensile strain is 20%,the resistance change rate of the thermoelectric fiber is only 10%.At a temperature difference of 80 K,the maximum output power is about850 pW.There is no significant change in the open circuit voltage of the thermoelectric fiber when it is stretched or bent.In addition,thermoelectric fibers are used to prepare wearable and compact thermoelectric devices.The thermoelectric device can adapt to surfaces with complex curvatures while also having excellent performance.2.Highly elastic thermoelectric fibers made of a mixture of Ecoflex and highly conductive graphene are prepared by extrusion molding method.The fiber with the Seebeck coefficient of 36.75 ?V/K has the ability to self-powered sensing for temperature based on the Seebeck effect.The experimental results show that the output voltage of the fiber is 36 ?V,when the temperature difference is 1 K.After 100 times bending-releasing cycles,the output voltage is almost unchanged.In addition,the sensitivity of the fiber for tensile behavior is 12% and 56% for tensile strain of 5% and50%,respectively.The combination of sensitivity to temperature and strain gives the graphene-Ecoflex composite fiber the ability to monitor the change of environmental temperature and human motion simultaneously.