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Morphology and Internal Structure of Polymeric and Carbon Nanofibers

Zhenxin, Zhong

Abstract Details

2011, Doctor of Philosophy, University of Akron, Polymer Science.

Evaporation and the associated solidification are important factors that affect the diameter of electrospun nanofibers. The evaporation and solidification of a charged jet were controlled by varying the partial pressure of water vapor during electrospinning of poly(ethylene oxide) from aqueous solution. As the partial pressure of water vapor increases, the solidification process of the charged jet becomes slower, allowing elongation of the charged jet to continue longer and thereby to form thinner fibers.

The morphology and internal structure of electrospun poly(vinylidene fluorides) nanofibers were investigated. Low voltage high resolution scanning electron microscopy was used to study the surface of electrospun nanofibers. Control of electrospinning process produced fibers with various morphological forms. Fibers that were beaded, branched, or split were obtained when different instabilities dominated in the electrospinning process. The high ratio of stretching during electrospinning aligns the polymer molecules along the fiber axis. A rapid evaporation of solvent during electrospinning gives fibers with small and imperfect crystallites. These can be perfected by thermal annealing. Fibers annealed at elevated temperature form plate-like lamellar crystals tightly linked by tie molecules. Electrospinning can provide ultrafine nanofibers with cross-sections that contain only a few polymer molecules. Ultrafine polymer nanofibers are extremely stable in transmission electron microscope. Electrospun nanofibers suspended on a holey carbon film showed features of individual polymer molecules.

Carbon fibers with diameters ranging from 100 nm to several microns were produced from mesophase pitch by a low cost gas jet process. The structure of mesophase pitch-based carbon fibers was investigated as a function of heat treatment temperatures. Submicron-sized graphene oxide flakes were prepared by a combination of oxidative treatment and ultrasonic radiation. Because pitch is a cheap raw material, graphitic fibers appear to be another useful starting material for mass production of graphene sheets.

Darrell Reneker, Dr. (Advisor)
Gary Hamad, Dr. (Committee Member)
Stephen Z. D. Cheng, Dr. (Committee Member)
Shi-Qing Wang, Dr. (Committee Member)
George Chase, Dr. (Committee Member)
117 p.

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Citations

  • Zhenxin, Z. (2011). Morphology and Internal Structure of Polymeric and Carbon Nanofibers [Doctoral dissertation, University of Akron]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=akron1303156454

    APA Style (7th edition)

  • Zhenxin, Zhong. Morphology and Internal Structure of Polymeric and Carbon Nanofibers. 2011. University of Akron, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=akron1303156454.

    MLA Style (8th edition)

  • Zhenxin, Zhong. "Morphology and Internal Structure of Polymeric and Carbon Nanofibers." Doctoral dissertation, University of Akron, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=akron1303156454

    Chicago Manual of Style (17th edition)