Research On The Mechanical And Thermal Properties Of Carbon Nanotube Papers

Carbon nanotube papers(Buckypapers)are porous films composed of randomly oriented carbon nanotubes(CNTs),and have huge application prospects in the fields of scientific research and engineering.To make full use of Carbon nanotube papers,it is necessary to thoroughly learn the mechanical,electrical and thermal properties of Carbon nanotube papers.In addition,the properties of Carbon nanotube papers are needed to be tuned to meet the demands of various applications.In this paper,the mechanical,electrical and thermal properties of Carbon nanotube papers are measured through the uniaxial tensile test and the direct electrical heating method.To study the effect of annealing on the Young's modulus,the electrical conductivity and the thermal conductivity of Carbon nanotube papers,a high-temperature annealing treatment was performed on the Carbon nanotube papers.The annealing effect was confirmed using the Raman spectra and the morphology characterization(SEM characterization and EDX characterization).The results show that the Raman G/D ratio of Carbon nanotube papers increased from 0.8 to 3.9 after annealing at 2800 ?,which indicates that the quality of CNTs has been improved after annealing.However,the results of SEM and EDX characterization showed that the surface morphology and the composition of Carbon nanotube papers did not change significantly before and after the annealing process.Carbon nanotube papers exhibits obvious elastic behavior in the initial stage of stretching,with the increase of deformation,the Carbon nanotube papers show a polymer-like viscoelastic behavior.The ultimate tensile strength of Carbon nanotube papers is 17.7 MPa,the elongation at break is 4.5%,and the Young's modulus is 1.7 GPa.High-temperature annealing treatment can improve the structural quality of CNTs,which makes the Young's modulus of Carbon nanotube papers optimized by 82%.At the same time,the inter-tube interaction between the CNTs is also significantly enhanced after annealing at 2800 ?,which shows that the elongation at break of the annealed Carbon nanotube papers is reduced to about 0.6%.The electrical property and the thermal property of Carbon nanotube papers were measured simultaneously using the direct electrical heating method.The electrical conductivity of Carbon nanotube papers at room temperature is 45.4 S/cm,which is far lower than that of CNTs.This can be attributed to the poor quality of CNTs and the contact resistance between CNTs,among them,the latter dominates.After the variable length test,the intrinsic thermal conductivity of the Carbon nanotube papers is obtained,which is 2.4 W/(m·K).This is also far lower than the thermal conductivity of CNTs,which is attributed to the large contact thermal resistance between CNTs.After the annealing treatment,the electrical conductivity and the thermal conductivity of Carbon nanotube papers increased by 29% and 125%,respectively,indicating that the interaction between CNTs is enhanced after the annealing process.In response to the view that Carbon nanotube papers can be regarded as a special kind of polymers,the paper refers to the research of Ultra-stretched polyethylene to explore the relation of the electrical conductivity and the thermal conductivity to the Young's modulus of Carbon nanotube papers.The Young's modulus of Carbon nanotube papers is determined by the mechanical properties of CNTs,and increases linearly with the annealing temperature.However,the electrical conductivity and the thermal conductivity of Carbon nanotube papers depend on the inter-tube contacts,and increase nonlinearly with the annealing temperature.Therefore,the relation of the electrical conductivity and the thermal conductivity to the Young's modulus of Carbon nanotube papers is nonlinear,which is different from the linear relation between thermal conductivity and modulus of stretching polyethylene.But the electrical conductivity of Carbon nanotube papers increases linearly with the increase of thermal conductivity in the annealing temperature range of 1000 ?-2800 ?,which can be used as a reference for the research of the similarity between Carbon nanotube papers and polymer to a certain extent.