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Construction of One-Dimensional Carbon and SnO2-based Nanomaterials via Electrospinning

Author: SongXiaoFeng
Tutor: WangCe
School: Jilin University
Course: Polymer Chemistry and Physics
Keywords: Electrospinning Porous carbon nanofibers Tin oxide fibers PAN PVP
CLC: TB383.1
Type: PhD thesis
Year: 2008
Downloads: 403
Quote: 1
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Abstract


Carbon and tin areⅣgroup in element periodic table, which are important elements in materials science studies. Particularly, one-dimensional (1D) nanostructure porous carbonaceous materials and tin dioxide have been a subject of intensive research due to their unique morphologies and photics and electrics properties. Among the methods generated 1D nanostructure, electrospinning seems to provide the simplest approach to nanofibers with both solid and hollow interiors that are exceptionally long in length, uniform in diameter, and diversified in composition. Comparing with a number of processing technique of fabricating micro fibers such as melt spinning, wet spinning and dry spinning, and nanofibers such as island spinning, template synthesis, etc., electrospinning offers several obvious advantage: (1) the process of fabricating nanofibers is simple and efficient; (2) the diameter of nanofibers fabricated can be controllable; (3) the range of the application is wide. Moreover, these nanofibes may provide a connection between the nanoscale world the macroscale world, science the diameters are in the nanometer range and the lengths are kilometers.In this dissertation, we comined electrospinning process with carbonization, template and sol-gel technique, trying to fabricated 1D micro-nanostructure materials. It involves four parts of works.In the first section, we successfully synthesized porous carbon nanofibers by chemical activation of polyacrylonitrile nanofibers via electrospinning. In the current approach, potassium hydroxide was adopted as activation reagent. Porous carbon nanofibers were systematically evaluated by using scanning electron microscope and the adsorption of nitrogen. The mass ratio of potassium hydroxide to preoxidized fibers(R), activation temperature and activation time are crucial for producing high quality NPCFs. The relationships between porous structure and process parameters are explored. NPCF were applied as the adsorption for nitrogen oxide to be compared to conventional porous carbon fibers.In the second section, This work describes the potential capability of ultrafine porous carbon nanofiber prepared via electrospinning in removal of SO2 from mixture gas stream. A series of conventional PCF(CPCF) and ultrafine PCF(UPCF) were produced under the identical conditions and NPCF was also modified. Compared to the CPCF, experimental results showed that the UPCF had the better adsorption capacity for SO2 due to its higher surface area and microporous volume. After the modification of the UPCF, adsorption capacities of UPCF for SO2 were improved further via increasing N-containing amount of UPCF and substrate which was followed by few changes in its specific surface area. The optimum concentration of modified reagent is 10%.From the results of fatigue test, it has been found that both the UPCF and the modified UPCF showed a good durability. In the third section, mesoporous carbon nanofibers with narrow pore size distribution have been obtained through a facile means that a mixture of polyacrylonitrile (PAN) and polyvinyl butyral (PVB) in dimethylformamide containing tin dichloride was electrospun into submicrometer fibers following oxidation and carbonization. The results of FT-IR and DSC show that PAN and PVB in the blend fibers are coexisted and phase separated, the addition of tin ion weaken impediment between polymers, such as the cyclization temperature of PAN are lowered sharply. The carbonized results also show that carbon fibers derived from PAN/PVB containing tin dichloride blend fibers not only exhibit narrow pore size distribution, but also possess higher BET surface area and pore volume in comparison with those derived from PAN/PVB bicomponent fibers. While the mass ratio of PAN/PVB transforms from 9/1 to 6/4 under the same amount of tin dichloride conditions, BET surface area and pore volume of porous carbon fiber increase, pore size distribution peak shift highly.In the forth section, A novel method for the large-scale fabrication of sensing and mesoporous SnO2 nanofibres has been demonstrated through electrospinning process with P123 or F127 as template agent. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), (FT-IR),X-ray diffraction patterns (XRD), and nitrogen adsorption-desorption confirm the average diameter of obtained mesoporous SnO2 nanofibres with 130nm, the porous structure and the tetragonal rutile structure (SnO2) in nanofibers. Also, the gas sensing properties of m-SnO2 nanofibers for ethanol were evaluated. It can be found that the surface structures of sensor materials have the important effect on sensitivity. The sensitivity of the nanofibers introduced template agent is superior to the pristine SnO2 nanofibers, but the sensitivity of the introduced P123 to ethanol gas is higher than that of the introduced F127.In the last section, a simple method for the large-scale fabrication of photocatalytic and mesoporous ZnO-SnO2 (m-Z-S) composite nanofibres has been demonstrated through electrospinning process with P123 as template agent. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction patterns (XRD), and nitrogen adsorption-desorption confirm the diameter of obtained m-Z-S nanofibres ranging between 100 and 150 nm, the porous structure and the mixture of wurtzite (ZnO) and rutile (SnO2) structure in composite fibers. The surface photovoltage spectroscopy (SPS) and photocatalytic degradation of methyl orange (MO) show the photocatalytic properties of the as-prepared m-Z-S nanofibres are superior to those of pure ZnO nanofibres, SnO2 nanofibres, or the pristine ZnO-SnO2 (Z-S) nanofibres.

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