【作者】 胡坚；

【导师】 王燕萍；

【作者基本信息】 东华大学 ， 材料加工工程， 2010， 硕士

【摘要】 在纤维工业的发展中,纤维超细化是一个重要发展方向。静电纺丝利用高分子溶液或熔体,在高压静电场条件下,制备亚微米或纳米纤维,成为制备超细纤维非常重要而可行的方法。静电纺丝制备的纤维或膜由于具有非常高的比表面积、孔隙率,非常小的纤维直径、孔隙尺寸,使其在医学修复、过滤、组织支架、药物给送系统、高性能电池、催化、传感器等方面具有巨大的应用前景。而同轴静电纺丝制备的中空超细碳纤维不仅具有气相生长碳纤维所具有的特性,而且在结构、性能和应用方面又与纳米碳管相似,具有更高的强度及模量、热稳定性、化学活性、导电性等特点,可望用在锂离子二次电池阳极材料、双电层电容器电极、高效吸附剂、结构增强材料等方面。本论文采用同轴静电纺丝技术,通过选取不同的电纺溶液和控制电纺参数制备出皮芯复合的超细纤维,再经过合适的浸泡、预氧化和碳化工艺,最终得到形貌规整的中空超细碳纤维。论文首先结合国外同轴静电纺丝技术,自行设计了同轴静电纺丝装置及其工艺流程,确定可行的制备纳米中空纤维的方法。测试了一系列所用溶液的粘度,导电率,表面张力等,探索适合同轴静电纺丝工艺的内液和外液。采用N,N二甲基甲酰胺(DMF)作溶剂,聚丙烯腈(PAN)和聚乙烯吡咯烷酮(PVP)分别作为外液和内液溶质,通过同轴静电纺丝的方法制备了PAN/PVP皮芯超细纤维。将PAN/PVP皮芯超细纤维放入水中浸泡,除去PVP芯层组分,再经过预氧化和碳化工艺制备出中空碳超细纤维。本论文对于同轴静电纺制备中空结构超细纤维最佳工艺的确定,主要从溶液性质、内外毛细管孔径、电压、接收距离、外液和内液的流速比进行了讨论。通过扫描电镜(SEM)分析,讨论了这些参数对电纺纤维形貌的影响,找到了最优工艺参数。当外液PAN_b浓度为16%,内液PVP浓度30%的纺丝溶液,内外针头孔径分别是Φ_内=0.8mm和Φ_外=1.6mm,电压在11kV,接收距离为15cm,外液和内液流速分别为50μl/min和25μl/min时,制备了结构规整的皮芯复合超细纤维。去除芯层后,通过扫描电镜测试,可观察到结构规整的中空超细纤维。将结构规整的PAN/PVP皮芯纤维毡通过浸泡处理去除PVP后,再进行纤维的预氧化,研究了预氧化温度和升温速度对预氧化毡的结构和性能的影响,在预氧化速度为5℃/min,预氧化温度为250℃时,得到的预氧化毡预氧化程度较完全。另外,本文以扫描电子显微镜系统的研究了聚丙烯腈超细纤维毡、预氧化毡和超细碳纤维毡的表面形态。通过红外光谱和X射线衍射表征了静电纺丝、预氧化和碳化过程中,超细纤维化学组成和结晶形态的变化。更多还原

【Abstract】 During the development of fiber industry, microfiber is an important goal. With the rapid development of nanoscience and technology, the preparation and applications of nanofibers become the hot field in research. In order to make fibers with diameters between submicrometer and nanometer, electrospinning is the most important and viable method, in which the microfibers are forming from polymer solutions or melts with the help of high voltage electric field. These electrospun fibers or mats have high surface area and porosity, as well as small diameters. They have enormous potential applications in wound dressing, filtration, protective clothing, tissue scaffolds, drug delivery system, high-performance cells, catalysis, and sensors. The hollow carbon microfibers (HCMFs) prepared by coaxial electrospinning not only have all the characters of the carbon fibers prepared by CVD method, but also have the same structure, capability and application with carbon nanotubes. Many potential applications have been proposed for HCMFs, including the anode of lithium ion battery, double lay capacitor electrode, high effective sorbent and structure strengthen materials, based on their high intensity and module, thermal capability stability, chemical active and electric conductivity.In this paper, using coaxial electrospinning technology, the skin-core composite microfibers were prepared by selecting different spinning solutions and process parameters. Through the appropriate soak, pre-oxidation and carbonization process, the carbon microfibers with hollow structure were gained ultimately.In this paper, by improving the electrospinning devices, we designed a coaxial electrospinning devices and spinning process to determine a viable method of preparation of hollow microfiber. A series of tests were on inner fluid and outer fluid, such as solution viscosity, conductivity, and surface tension, and so on. Using polyacrylonitrile(PAN)/DMF and polyvinylpyrrolidone(PVP)/DMF as outer fluid and inner fluid respectively, PAN/PVP skin-core microfibers was prepared by coaxial electrospinning. The PAN/PVP skin-core microfibers were soaked into the water to remove the PVP core layer component, and then through the pre-oxidation and carbonization process hollow carbon microfibers were prepared.In this paper, in order to determine of optimal process parameters to prepare the coaxial electrospun hollow microfibers, the solution properties, inner and outer capillary diameter, voltage, receiving distance, outer fluid and inner fluid velocity ratio were discussed. The influence of these parameters on the electrospun fibers morphology was discussed, and the optimal process parameters were found finally. When the outer fluid PAN_b concentration of 16%, the inner fluid PVP concentration of 30%, inside and outside needle within the aperture beingΦ_I= 0.8mm andΦ_O=1.6mm respectively, voltage 11kV, receiving distance 15cm, 50μl/min outer and 25μl/min inner fluid velocity, the skin-core composite microfibers were prepared successfully. After removing core layer, regular hollow structure of microfibers can be observed by scanning electron microscopy tests.The PAN/PVP skin-core fibers dried in blast drying box after PVP removed by soaking in water, and then placed in muffle furnace for pre-oxidation. Effects of the temperature and heating rate on the structure and property of pre-oxidation web were discussed in this paper. When the pre-oxidation heating rate was 5℃/ min and pre-oxidation temperature was 250℃, the obtained felt had the fully pre-oxidation treatment.The morphology of electrospun microfibers, pre-oxidized microfibers and carbon microfibers were studied by scanning electron microscope (SEM). The changes of chemical composition and crystalline morphology of electrospun microfibers, pre-oxidized microfibers and carbon microfibers were performed by X-ray diffractometry and infrared spectroscopy respectively.更多还原