The Preparation Of High Quality Carbon Nanotubes And Aligned Carbon Nanotubes In SWNTs/PMMA Composites

Carbon nanotubes(CNTs)have excellent characteristic and wide applications.At present,researches the preparation of CNT with structural integrity,quasi straight, diameter uniformity,high purity is hotspot of studies.Also the purification of CNT is very important.The alignment of CNT in polymer is a key concerned by scientists.The single walled carbon nanotubes(SWNTs)and SWNTs' bundle were produced by using anode arc plasma method to evaporate graphite rods with Fe,Co,Ni catalyst. The influence of catalyst parameters,kinds of gas,air pressure and electricity intensity were discussed.At the end,the optimal parameters in the synthesis of anode-arc plasma evaporation method for preparing SWNTs were helium pressure 6.0×10⁴pa, argon pressure 5.0×10⁴pa,the catalyst content of W(Fe):W(Co):W(Ni)=1:1:1,arc current intensity 70A,and with good cooling.The purification of SWNTs and SWNTs' bundles were realized by aid oxidizerfor different products.The characteristics of the bundles were studied through TEM, SEM,Raman spectrum and the thermogravimetric analysis(TGA).It was proved that the products was a high quality SWNTs and bundles with homogeneous diameter, less-defection,high-purified and quasi-straight SWNTs.The SWNTs/PMMA composites with good alignment,uniformity and dispersion of SWNTs were fabricated by repeated mechanical stretching method.The SEM and the TEM demonstrated that SWNTs were aligned in the stretching direction and well dispersed in the matrix.Polarized Raman spectra indicated that SWNTs had a good alignment in the composite The mechanism of the realignment of CNTs in electric field strong magnetic field and the shear flow,were studied using different theoretical models. The SWNTs/PMMA composite belongs to the realignment in shear flow.Our experiment is consist with the model in shear flow.The electrical,mechanical and thermal stable properties of the SWNTs/PMMA composites were studied.The composite presented distinct anisotropic electrical and mechanical properties.The SWNTs/PMMA composites presented higher electrical conductivity and the mechanical properties along the stretching direction is higher than that of vertical to it.With the increase of SWNTs concentration(from 0.5%to 8%),the composite's Young's modulus,tensile strength and elongation are improved remarkably. With a content of 8%SWNTs,the Young's modulus increased 210.3%,the tensile strength increases 209.0%and the elongation increases 301.7%along the stretching direction.The composite electrical property was also improved and exhibited anisotropism.The conductivity of composite along the aligning direction of SWNTs increased from 10^-8S/cm to 3×10^-6S/cm as the SWNTs fraction increased from 0.5wt% to 1wt%.The conductivity of composite along the aligning direction was higher than that of vertical to it by 10⁴ times,with SWNTs fraction 1%.The thermal stable properties of SWNTs/PMMA composite was also improved.The temperature of the maximum mass loss rate of the composite with lwt%SWNTs was higher 50℃than that of PMMA.