The impregnation of a special grade PAN precursor,fibers wus carried out in a 8 wt% KMnO4 aqueous solution to obtain modified PAN precursor fibers. The effects of modification on the chemical stncture and the mechani...The impregnation of a special grade PAN precursor,fibers wus carried out in a 8 wt% KMnO4 aqueous solution to obtain modified PAN precursor fibers. The effects of modification on the chemical stncture and the mechanical properties of precursor fibers thermally stabilized and their resulting carbon fibers u＇ere characterized by the combiination use of densities, wide-angle X-ray diffraction （WAXD）, X-ray photoelectron speetroscopy （XPS）, elemental analysis （ EA ）, Fourier traasform infrared spectroscopy （FT-IR） and scanning electron microscope （SEM）, etc.KMnO4 as a strong oxidizer can swell, oxidize and corrode the skin of a precursor.fiber, and transform C≡N groups to C≡N ones, meamchile , it can decreuse the crystal .size increuse the orientation index and the costallinity index, furthermore it can increuse the densities of modified PAN precursors and resuhing thermally stabilized fibers. As a result, the carbon fibers developed from modified PAN fibers show an improvement in tensile strength of 31.25 % and an improvement in elongation of 77.78 % , but a decrease of 16. 52% in Young＇s modulus.展开更多
Different polyacrylonitrile （PAN） precursor fibers that displayed various thermal properties were studied by using differential scanning calorimetry （DSC）. Results showed that some commercial PAN precursor fibers ...Different polyacrylonitrile （PAN） precursor fibers that displayed various thermal properties were studied by using differential scanning calorimetry （DSC）. Results showed that some commercial PAN precursor fibers displayed double separated peaks and these fibers were of high quality because of their process stability during their conversion to carbon fibers of high performance. Some fabrication processes, such as spinning, drawing, could not apparently change the DSC features of a PAN precursor fiber. It was concluded that the thermal properties of a PAN precursor fiber was mainly determined from its comonomer content type and compositions.展开更多
Two different PAN precursors with various comonomers were wet-spun. The properties and structurul changes of PAN precursors and their evolution during preoxidation and carbonization process were characterized by the u...Two different PAN precursors with various comonomers were wet-spun. The properties and structurul changes of PAN precursors and their evolution during preoxidation and carbonization process were characterized by the use of DSC , FTIR and traditional parameters, e g, tensile strength. It is demonstrated that acrylamide（ AAM ） is very effective to make the DSC peak be separated compared to methyl acrylate （ MA ）. As a result, carbon fibers developed from AAM-contained precursors have a better tenacity compared to those developed from MAcontained ones.展开更多
Activated carbon fiber(ACF)is undoubtedly one of the most significant carbon nanocomposite materials to consider from the perspective of application in adsorption.Compared to other commercial porous storage materials,...Activated carbon fiber(ACF)is undoubtedly one of the most significant carbon nanocomposite materials to consider from the perspective of application in adsorption.Compared to other commercial porous storage materials,it offers many benefits.With a fiber-like shape and a clearly defined porosity structure,activated carbon fiber(ACF)is a potential microporous material.In general,synthetic carbon fiber(CF)can be used to commercially make ACF with the inclusion of an activation procedure.High packing density,outstanding volumetric capacity,rapid adsorption/desorption,and ease of handling are some of the unique properties of ACF.The production expenses of ACF are made up of fiber processing costs and activation costs,both of which are comparatively more expensive than those of other activated carbons.Recently,researchers have indicated that the manufacturing of ACF from less expensive precursors might be accomplished by preparing activated carbon(AC)from agricultural wastes.In comparison to synthetic ACF,there were fewer details and publicly accessible sources of information about these natural fiber derived ACF.The cost of processing fiber is higher and shaping fiber into the correct shape is challenging.In this study,social and environmental compliance,economic development,advantages of carbon fiber,and applications of carbon fiber are discussed.展开更多
Structural changes in carbon fibers at each stage of, especially, preoxidation process are well known to play a great role in achieving the ultimate product quality. Differential scanning calorimetry (DSC), scanning e...Structural changes in carbon fibers at each stage of, especially, preoxidation process are well known to play a great role in achieving the ultimate product quality. Differential scanning calorimetry (DSC), scanning electron microscope (SEM), density method and optical microscope were used to characterize the preoxidation extent. A conventional approach, e.g., density aim, to evaluate the extent of preoxidation is not very exact. A DSC curve of a PAN precursor only can provide general information, major in the temperature regime of preoxidation reaction. However, the evaluation of a preoxidation extent, especially from conventional preoxidation temperature with a great span regime of 200~400癈, is put forward in this paper, in which the evolution of core/shell morphological structure is a kind of straightforward evidence.展开更多
The activated carbon fiber（ACF） was prepared from polyacrylonitrile-based pre-oxidized fiber（PANOF） by KOH direct activation. The influence of activation conditions including impregnation ratio（the mass ratio of ...The activated carbon fiber（ACF） was prepared from polyacrylonitrile-based pre-oxidized fiber（PANOF） by KOH direct activation. The influence of activation conditions including impregnation ratio（the mass ratio of PANOF to KOH）, activation temperature and activation time on the pore structure and electrochemical properties of ACF was investigated, and the corresponding activation mechanism was proposed. The ACF prepared at an activation temperature of 800℃ and an impregnation ratio（the mass ratio of PANOF to KOH） of 1：2 for an activation time of 1 b in 6 mol/L KOH solution exhibits a specific surface area of 3029 m^2/g, a mesoporosity of 84.2% and a specific capacitance of 288 F/g, and shows a good capacitive performance. The prepared ACF can be used as the electrode material for supercapacitors.展开更多
Thermal mechanical analysis,FT-IR,WAXD and some conventional measurements,such as densities and mechanical properties,were used to characterize the effect of the modification using KMnO4 and SnCl4 on the thermal mecha...Thermal mechanical analysis,FT-IR,WAXD and some conventional measurements,such as densities and mechanical properties,were used to characterize the effect of the modification using KMnO4 and SnCl4 on the thermal mechanical behaviors and structural changes during the process of thermal stabilization of modified PAN precursors.Compared to the unmodified original PAN precursors,some conclusions were drawn that the thermal stabilization starts at a lower temperature for modified PAN fibers,for example,the peak of thermal stress changes for modified PAN precursors using KMnO4 displays a decrease of 20℃ and a increase of 30% in the ultimate thermal stress,that chemical modification makes structural transformation perfect and increases by 25% of the thermal stress at the temperature range of 230℃-300℃,that the modified PAN fibers display an increase of 100% in the thermal strain,once after pre-oxidized,show an increase of 7.8% in orientation index,and a decrease of 9.9% in crystal size for identical preload in the region of 13.1-14.5MPa.It was also concluded that the modification using SnCl4 would alleviate the changes in physical and chemical stress regimes and result in improvement in structure and decrease in defects.展开更多
The nanopore structures in precursors Four carbon-fiber precursors are prepared. They are crucial to the performance of PAN-based carbon fibers are bath-fed filaments （A）, water-washing filaments （B） hot-stretchin...The nanopore structures in precursors Four carbon-fiber precursors are prepared. They are crucial to the performance of PAN-based carbon fibers are bath-fed filaments （A）, water-washing filaments （B） hot-stretching filaments （C） and drying-densification filaments （D）. Synchrotron radiation small angle X-ray scattering is used to probe and compare the nanopore structures of the four fibers. The nanopore size, discrete volume distribution, nanopore orientation degree along the fiber axis and the porosity are obtained. The results demonstrate that the nanopores are mainly formed in the water-washing stage. During the processes of the subsequent production technologies, the slenderness ratio of nanopores and their orientation degree along the fiber axis increase further and simultaneously, the porosity decreases. These results are helpful for improving the performance of the final carbon fibers.展开更多
基金Founded by the National Natural Science Foundation of China(No.50333070)
文摘The impregnation of a special grade PAN precursor,fibers wus carried out in a 8 wt% KMnO4 aqueous solution to obtain modified PAN precursor fibers. The effects of modification on the chemical stncture and the mechanical properties of precursor fibers thermally stabilized and their resulting carbon fibers u＇ere characterized by the combiination use of densities, wide-angle X-ray diffraction （WAXD）, X-ray photoelectron speetroscopy （XPS）, elemental analysis （ EA ）, Fourier traasform infrared spectroscopy （FT-IR） and scanning electron microscope （SEM）, etc.KMnO4 as a strong oxidizer can swell, oxidize and corrode the skin of a precursor.fiber, and transform C≡N groups to C≡N ones, meamchile , it can decreuse the crystal .size increuse the orientation index and the costallinity index, furthermore it can increuse the densities of modified PAN precursors and resuhing thermally stabilized fibers. As a result, the carbon fibers developed from modified PAN fibers show an improvement in tensile strength of 31.25 % and an improvement in elongation of 77.78 % , but a decrease of 16. 52% in Young＇s modulus.
基金supported by the National Natural Science Foundation of China under grant No.59783002by the Natural Science Foundation of Henan under grant Nos.200510465008 and 0523021200.
文摘Different polyacrylonitrile （PAN） precursor fibers that displayed various thermal properties were studied by using differential scanning calorimetry （DSC）. Results showed that some commercial PAN precursor fibers displayed double separated peaks and these fibers were of high quality because of their process stability during their conversion to carbon fibers of high performance. Some fabrication processes, such as spinning, drawing, could not apparently change the DSC features of a PAN precursor fiber. It was concluded that the thermal properties of a PAN precursor fiber was mainly determined from its comonomer content type and compositions.
基金Funded bythe National Natural Science Foundation of China(No.50333070 and 50273002)
文摘Two different PAN precursors with various comonomers were wet-spun. The properties and structurul changes of PAN precursors and their evolution during preoxidation and carbonization process were characterized by the use of DSC , FTIR and traditional parameters, e g, tensile strength. It is demonstrated that acrylamide（ AAM ） is very effective to make the DSC peak be separated compared to methyl acrylate （ MA ）. As a result, carbon fibers developed from AAM-contained precursors have a better tenacity compared to those developed from MAcontained ones.
文摘Activated carbon fiber(ACF)is undoubtedly one of the most significant carbon nanocomposite materials to consider from the perspective of application in adsorption.Compared to other commercial porous storage materials,it offers many benefits.With a fiber-like shape and a clearly defined porosity structure,activated carbon fiber(ACF)is a potential microporous material.In general,synthetic carbon fiber(CF)can be used to commercially make ACF with the inclusion of an activation procedure.High packing density,outstanding volumetric capacity,rapid adsorption/desorption,and ease of handling are some of the unique properties of ACF.The production expenses of ACF are made up of fiber processing costs and activation costs,both of which are comparatively more expensive than those of other activated carbons.Recently,researchers have indicated that the manufacturing of ACF from less expensive precursors might be accomplished by preparing activated carbon(AC)from agricultural wastes.In comparison to synthetic ACF,there were fewer details and publicly accessible sources of information about these natural fiber derived ACF.The cost of processing fiber is higher and shaping fiber into the correct shape is challenging.In this study,social and environmental compliance,economic development,advantages of carbon fiber,and applications of carbon fiber are discussed.
基金the National Natural Science Foundatlon of China under grant No.50172004,50273002 ,50333070.
文摘Structural changes in carbon fibers at each stage of, especially, preoxidation process are well known to play a great role in achieving the ultimate product quality. Differential scanning calorimetry (DSC), scanning electron microscope (SEM), density method and optical microscope were used to characterize the preoxidation extent. A conventional approach, e.g., density aim, to evaluate the extent of preoxidation is not very exact. A DSC curve of a PAN precursor only can provide general information, major in the temperature regime of preoxidation reaction. However, the evaluation of a preoxidation extent, especially from conventional preoxidation temperature with a great span regime of 200~400癈, is put forward in this paper, in which the evolution of core/shell morphological structure is a kind of straightforward evidence.
基金Supported by the National Natural Science Foundation of China（No.21273097） and the Key Project of Jilin Province, China（No.20126010）.
文摘The activated carbon fiber（ACF） was prepared from polyacrylonitrile-based pre-oxidized fiber（PANOF） by KOH direct activation. The influence of activation conditions including impregnation ratio（the mass ratio of PANOF to KOH）, activation temperature and activation time on the pore structure and electrochemical properties of ACF was investigated, and the corresponding activation mechanism was proposed. The ACF prepared at an activation temperature of 800℃ and an impregnation ratio（the mass ratio of PANOF to KOH） of 1：2 for an activation time of 1 b in 6 mol/L KOH solution exhibits a specific surface area of 3029 m^2/g, a mesoporosity of 84.2% and a specific capacitance of 288 F/g, and shows a good capacitive performance. The prepared ACF can be used as the electrode material for supercapacitors.
基金HAIPURT (No2006KYCX009)National Natural Science Foundation of Henan,China (No200510465008)Henan Innovation Project of China(No0523021300)
文摘Thermal mechanical analysis,FT-IR,WAXD and some conventional measurements,such as densities and mechanical properties,were used to characterize the effect of the modification using KMnO4 and SnCl4 on the thermal mechanical behaviors and structural changes during the process of thermal stabilization of modified PAN precursors.Compared to the unmodified original PAN precursors,some conclusions were drawn that the thermal stabilization starts at a lower temperature for modified PAN fibers,for example,the peak of thermal stress changes for modified PAN precursors using KMnO4 displays a decrease of 20℃ and a increase of 30% in the ultimate thermal stress,that chemical modification makes structural transformation perfect and increases by 25% of the thermal stress at the temperature range of 230℃-300℃,that the modified PAN fibers display an increase of 100% in the thermal strain,once after pre-oxidized,show an increase of 7.8% in orientation index,and a decrease of 9.9% in crystal size for identical preload in the region of 13.1-14.5MPa.It was also concluded that the modification using SnCl4 would alleviate the changes in physical and chemical stress regimes and result in improvement in structure and decrease in defects.
基金Supported by National Natural Science Foundation of China (10835008)Knowledge Innovation Program of Chinese Academy of Sciences (KJCX3-SYW-N8)Momentous Equipment Program of Chinese Academy of Sciences (YZ200829)
文摘The nanopore structures in precursors Four carbon-fiber precursors are prepared. They are crucial to the performance of PAN-based carbon fibers are bath-fed filaments （A）, water-washing filaments （B） hot-stretching filaments （C） and drying-densification filaments （D）. Synchrotron radiation small angle X-ray scattering is used to probe and compare the nanopore structures of the four fibers. The nanopore size, discrete volume distribution, nanopore orientation degree along the fiber axis and the porosity are obtained. The results demonstrate that the nanopores are mainly formed in the water-washing stage. During the processes of the subsequent production technologies, the slenderness ratio of nanopores and their orientation degree along the fiber axis increase further and simultaneously, the porosity decreases. These results are helpful for improving the performance of the final carbon fibers.
