The Fabrication And Characterization Of Pan Based Mesoporous Carbon Fibers

Activated carbon fibers (ACFs) have uniform pore distribution, large specific surface area and the performance of heat-resisting, acid-resisting, alkali-resisting. ACFs also have good electrical conductivity and chemical stability. So they are widely used in many fields because of their unique chemical structure, physical structure and excellent adsorption performance. But mostly pore size distribution are in1～2nm, the properties have endowed ACFS with high adsorption capacity for small-molecular-size pollutants. However, these features might not always be advantageous, especially when ACFS are being used in medicine, electronic and catalytic fields.To prepare mesoporous ACFs by adding additives has been researched in this paper. Concrete method is as follows:The appropriate pore-forming agents were chosen which had low decomposition temperature, and they mixed with PAN solution and then used wet spinning to prepare fiber precursor. After preoxidation, carbonization and activation, pore-forming agents decomposed and escaped from the fiber to form holes.The selection of pore-forming agents and the compatibility between pore-forming agent and PAN are studied.. Based on the research, polymethyl methacrylate (PMMA), polyvinyl pyrrolidone (K30) and acetylacetone nickel have excellent solubility property in DMSO. They have good compatibility and their decomposition temperature is lower than PAN. So in the process of carbonization and activation, it’s easy to form holes. According to the research, PMMA, K30and acetylacetone nickel are the best choice for pore-forming agents.The content of pore-forming agent, mass ratio of pore-forming agent to PAN were also studied for spinning and rheological properties of spinning dope. Experiments show that, when the concentration of pore-forming agent is5%, the temperature is60℃, it’s the best condition for spinning. Secondly, spinning dope belongs to non-newtonian fluid, its apparent viscosity reduce as the temperature rises. when spinning dope is sheared, the value of complex viscosity has a critical value with the shear rate change. Before critical value, it drops rapidly. while After critical value, complex viscosity decrease slowly and tend to be gentle. The viscosity is almost the same in high shear rate.Next, fiber precursor was prepared by wet spinning and properties were characterized. The results indicate that elongation and strength of fiber precursor reduced by adding pore-forming agent, but increasing draw ratio is benefit for improvement of the fiber strength. After SEM analysis, we found that the surface of fiber precursor by adding PMMA is rough and what’s worse there are holes on the surface, while adding PVP the surface is uniform, when adding PVP and acetyl acetone nickel in the spinning solution,the fiber have better apparent morphology.Finally, the appropriate temperature condition was chosen for carbonization and activation of activated carbon fibers, and its properties were also characterized. The results showed that when the temperature is800℃, it’s the best condition for carbonization and activation. According to FT-IR and TG-DTA analysis, pore-forming agent mostly decomposed. The data of static benzene adsorption showed that, ACF by adding K30adsorb more benzene than ACF adding PMMA, K30decomposed completely than PMMA. While the value of static benzene adsorption for ACF by adding acetyl acetone nickel and K30was larger than ACF adding K30, it showed that acetyl acetone nickel played an important role the control joined to the aperture control of holes.