Telluride Nanomaterials:Hydrothermal Preparation And Thermoelectric Properties Of Its Nanofilms

The thermoelectric material can realize the direct conversion of the thermal energy and the electric energy,and is a representative of the green energy technology.Waste heat can be collected effectively and energy saving can be achieved.It is widely used in refrigeration and power generation.Inorganic thermoelectric materials?TE?have been widely studied and applied due to their high thermoelectric properties.Because of the high quantum confinement effect,large specific surface area,strong phonon scattering and the enhancement of energy level spacing,tellurium-based nanomaterials can achieve higher Seebeck coefficient and lower thermal conductivity.It shows great application potential in the research of thermoelectric materials.But its low electrical conductivity limits its application in the field of thermoelectric.The thermoelectric properties can be improved by doping metal atoms.Poly?vinylidene fluoride??PVDF?,as a flexible substrate,plays an important role in enhancing the flexibility of inorganic compounds,and has been widely used in the preparation of flexible inorganic compound films with high performance.This thesis mainly detected and discussed the effects of different conditions on tellurium and tellurium-based nanocomposites of preparation and TE properties and their potential in thermoelectric conversion devices.The major contents and cinclusions are as follows:1.Ultrafine tellurium nanowires?diameter 10³5 nm?were synthesized by hydrothermal method.The freestanding nanofilms were obtained by filtration.Furtherly,the flexible thin films were obtained by the composite with PVDF.The results show that the prepared tellurium nanowires exhibit higher Seebeck coefficient and lower thermal conductivity than the previously reported tellurium nanowires at room temperature,with the values of 551?V K^-1 and 0.16 W m^-11 K^-1,respectively.Low thermal conductivity makes tellurium nanowires with high ZT.In combination with PVDF,the Seebeck coefficient decreased to 469.5?V K^-1,which is still higher than that reported by some reports.The synthesized tellurium nanowires provide a template for the next preparation of telluride.The flexible composite film provides the possibility for the fabrication and formation of flexible devices.2.N-type silver tellurium nanowires were synthesized by a simple galvanic exchange reaction?GER?,using tellurium nanowires as templates at room temperature.The Seebeck coefficient was-93.98?V K^-1 after the optimization of the reaction time and the silver nitrate concentration.Further,a flexible n-type silver telluride nanofilm was obtained directly by pressing with PVDF films.The p-type silver tellurium nanowires were obtained by hydrothermal method,and the power factor of 0.63?W m^-1 K^-2 was obtained.Compared with pure tellurium nanowires,the thermoelectric properties of n-type and p-type composite films have been improved by order of magnitude.Thermoelectric device was consisted of p-type and n-type products,resulting in an output voltage of 65 mV at 75 K.The galvanic exchange reaction provides potential for the preparation of other inorganic flexible composite films.3.Niobium tellurium nanomaterials were synthesized by a simple hydrothermal method.By adjusting the proportion of different reactants,the maximum power factor43.50?W·m^-1·K^-2 was obtained when the ratio was 1.By investigating the placement time,we found that niobium telluride has stable thermoelectric properties,which provides a basis for the further study of thermoelectric properties of niobium telluride.