| With the development of carbon fiber preparation process and the progress of composite material technology,carbon fiber has been widely used in the field of national defense,aerospace,automobile,ship and high-end sporting goods due to its excellent characteristics of light,high strength,corrosion resistance,fatigue resistance and conductivity.However,defects such as wrinkling,splitting and skin-core structure of carbon fiber seriously affect the quality and performance of carbon fiber,so these defects must be reduced or even eliminated.At present,the traditional spinning methods for preparing carbon fibers cannot avoid these defects.Therefore,this topic innovatively proposes to use the micro-nano lamination technology to prepare carbon fiber raw silks with rectangular cross-section,and use polyacrylonitrile(PAN)and mesophase pitch(MP)based mixed gel.The solution was used as the raw material of carbon fiber,and the ribbon-shaped laminated MP/PAN composite carbon fiber was successfully prepared through subsequent pre-oxidation and carbonization processes.The main study contents and findings are as follows:(1)The effects of different ratios of MP and PAN on the ribbon-shaped laminated carbon fiber raw silk were investigated.The study found that the increase of MP and PAN content in the gel solution was beneficial to the increase of C element content in the ribbon-shaped laminated carbon fiber raw silks,and the surface and cross-sectional morphology of the ribbon-shaped laminated carbon fiber raw silks was good,and no skin-core structure was observed,but there are a few microporous defects;TG analysis in oxygen atmosphere shows that the suitable temperature range for pre-oxidation treatment is90 ℃-110 ℃,which is greatly lower than the pre-oxidation temperature of traditional PAN and MP carbon fibers.(2)The effect of different temperatures on pre-oxidation of ribbon-shaped laminated MP/PAN composite carbon fibers was studied.It was found that the content of O element and the orientation of the microcrystal were significantly higher than those of the raw silks.Although there are micropores in the interior,there are no folds,splits and skin core structure.The pre-oxidation temperature of 110 ℃ has been greatly reduced compared with that of traditional carbon fiber production.According to TG analysis in nitrogen atmosphere,the suitable carbonization temperature range is 700 ℃-900 ℃,which is significantly lower than the carbonization temperature of traditional PAN and MP carbon fibers.(3)The effects of different carbonization temperatures on ribbon-shaped laminated MP/PAN composite carbon fibers were studied.The results show that the ribbon-shaped laminated MP/PAN composite carbon fibers have good morphology,and have a more orderly graphite-like microstructure with the increase of carbonization temperature.The conductivity also increases with the increase of MP content and carbonization temperature,and the best conductivity can reach 10.75 S/cm.The above excellent structure and properties are just obtained at the carbonization temperature of 800 ℃,so micro-nano lamination technology has great potential in the preparation of high-performance carbon fibers. |
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