Study On Preparation And Thermoelectric Properties Of BN Composite Thermoelectric Materials

As the shortage of energy becomes more and more obvious,thermoelectric conversion becomes an important method to solve the problem of energy shortage,and the key to thermoelectric conversion is to prepare high-quality thermoelectric materials.Conventional inorganic thermoelectric materials are brittle and difficult to adhere closely to complex heat source surfaces,limiting their application.In recent years,nanostructure design and nanocomposites have provided the direction for further optimization of traditional thermoelectric materials.Among them,due to the unique hollow structure of carbon nanotubes?CNT?and excellent electrical properties,a large number of CNTs have been used to prepare composite thermoelectric materials to improve the thermoelectric properties of thermoelectric materials.Boron nitride nanotubes?BNNT?have similar structure and properties to CNTs,and have better thermal and chemical stability than CNTs.They can adapt to more complex applications and become a good composite replacement for CNTs.This topic is based on the thermoelectricity study of nano-scale Bi₂Te₃ and BNNT/BCNNT composite films.The composite film was prepared by vacuum suction-hot pressing.Firstly,Bi₂Te₃ nanoparticles were prepared by mechanical ball milling,Bi₂Te₃ nanowires were prepared by AAO template electrodeposition method,BNNT was prepared by catalytic assisted ball milling,and BCNNT was prepared by post-treatment.Then they were prepared into a certain proportion of mixed solution,vacuumed after ultrasonic vibration.After suction filtration,a filter membrane is obtained;finally,hot pressing is performed under certain conditions to obtain a composite film having good compactness.By studying the effects of different hot pressing temperature,Bi₂Te₃ nanoparticle amount and hot pressing time on the thermoelectric properties of the composite film,the optimal hot pressing conditions were determined:hot pressing temperature 180°C,Bi₂Te₃ nanoparticle amount 0.02g,hot pressing time 10min.Under the hot pressing conditions,the effect of BNNT content on the thermoelectric properties of Bi2Te3nanoparticles and BNNT composite films was studied.The results show that with the increase of BNNT content,the Seebeck coefficient of composite films decreases continuously and the BNNT content in 2ml?concentration is 0.3mg/ml?,the composite film has the best power factor.Secondly,the effect of C doping time on the thermoelectric properties of Bi₂Te₃ nanoparticles and BCNNT composite films was studied.The test results show that under the condition of C doping for 15 min,there is the best conductivity and power factor,and the power factor is highest at room temperature.It reached 1843.2nW/mK².Finally,the thermoelectric properties of Bi₂Te₃nanowires and BCNNT composite films were investigated.The results show that the conductivity,Seebeck coefficient and power of the composite films of Bi₂Te₃ nanowires are compared with those of Bi₂Te₃ nanoparticles.The factors have all dropped.