Experimental Study On Thermal Conductivity And Thermoelectric Properties Of Carbon Nanotube Macroscopic Materials

Carbon nanotube macromaterials can give full play to their excellent properties under the microscopic morphology at the macroscopic scale,and can show many new characteristics not found in nanomaterials.Because there are a large number of nano-scale phonon interface scatterings between carbon nanotubes,carbon nanotube macromaterials often have a low thermal conductivity,which makes it a promising application in the field of thermoelectric conversion.In recent years,the thermoelectric properties of carbon nanotube macromaterials have received widespread attention from researchers.In this paper,plasma sintered（SPS）carbon nanotube dense bulk materials and carbon nanotube sponge porous materials were prepared experimentally,and their micromorphology was characterized.Their resistivity,Seebeck coefficient,thermal conductivity,The thermal diffusivity,specific heat capacity,etc.were calculated and analyzed for their thermoelectric merit figures and compared with existing carbon nanotube macromaterials.main tasks as follows:（1）The thermal conductivity of single-walled carbon nanotubes（SWCNT）and multi-walled carbon nanotubes（MWCNT）stacked beds were measured at different packing densities.The results show that the thermal conductivity of both single-walled carbon nanotubes and multi-walled carbon nanotubes stacked beds increases linearly with increasing bulk density.At the same time,the thermal conductivity of the SWCNT stacked bed was calculated using a theoretical model,and the trend of the calculation results was basically consistent with the experimental results.（2）Single-walled carbon nanotubes and multi-walled carbon nanotubes densely sintered bulk materials were prepared by the plasma sintering method,and the microstructure was characterized by SEM;the resistivity,Seebeck coefficient,and thermal conductivity rate.The results show that the thermal conductivity of densely sintered carbon nanotube bulk materials is significantly improved compared to that of stacked beds;the Seebeck coefficient of single-walled carbon nanotubes densely sintered bulk materials is significantly higher than that of multi-walled carbon nanotubes densely sintered.The bulk material,while the thermal conductivity of the former is slightly higher than the latter;the single-walled carbon nanotube dense sintered bulk material has a maximum ZT value of 9.33×10^-5 at room temperature and atmospheric pressure,which is better than this and other reports.Wall carbon nanotubes dense sintered bulk material.（3）An ultra-low density,high porosity multi-walled carbon nanotube sponge was prepared,and its microstructure was characterized by SEM;its resistivity,Seebeck coefficient,thermal diffusion coefficient,and specific heat capacity were measured.The results show that the thermal conductivity of the multi-walled carbon nanotube sponge is as low as 0.021 W/（m·K）at room temperature and atmospheric pressure,and its Seebeck coefficient is also significantly higher than that of single-walled carbon nanotubes and multi-walled carbon nanotubes.sintered bulk material。Body material.At the same time,the ZT value of the multi-walled carbon nanotube sponge at room temperature and atmospheric pressure reached a maximum of 8.99×10^-4,which is better than that of single-walled carbon nanotubes and multi-walled carbon nanotubes.sintered bulk material And other pure carbon nanotube macromaterials currently known.