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THE FABRICATION OF POLYMER-DERIVED SICN/SIBCN CERAMIC NANOSTRUCTURES AND INVESTIGATION OF THEIR STRUCTURE-PROPERTY RELATIONSHIP

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Date Issued:
2010
Abstract/Description:
Polymer-derived Ceramics (PDCs) represent a unique class of high-temperature stable materials synthesized directly by the thermal decomposition of polymers. This research first focuses on the fabrication of high temperature stable siliconcarbonitride (SiCN) fibers by electrospinning for ceramic matrix composite (CMC) applications. Ceraset™ VL20, a commercially available liquid cyclosilazane, was functionalized with aluminum sec-butoxide in order to be electrospinnable. The surface morphology of the electrospun fibers was investigated using the fibers produced from solvents. The electrospun fibers produced from the chloroform/N,N-dimethylformamide solutions had hierarchical structures that led to superhydrophobic surfaces. A ÂÂÂÂ"dry skinÂÂÂÂ" model was proposed to explain the formation of micro/- and nanostructures. The second objective of the research is to align the multiwalled carbon nanotubes (MWCNTs) in PDC fibers. For this purpose, a non-invasive approach to disperse carbon nanotubes in polyaluminasilazane chloroform solutions was developed using a conjugated block copolymer synthesized by ATRP. The effect of the polymer and CNT concentration on the fiber structure and morphology was also examined. Detailed characterization using SEM and TEM was performed to demonstrate the orientation of CNTs inside the ceramic fibers. Additionally, the electrical properties of the ceramic fibers were investigated. Finally, the structural evolution of polymer-derived amorphous siliconborocarbonitride (SiBCN) ceramics with pyrolysis temperatures was studied by solid-state NMR, Raman and EPR spectroscopy. Results suggested the presence of three major components: (i) hexagonal boron nitride (h-BN), (ii) turbostratic boron nitride (t-BN), and (iii) BN2C groups in the final ceramic. The pyrolysis at higher temperature generated boron nitride (BN3) with a simultaneous decomposition of BN2C groups. A thermodynamic model was proposed to quantitatively explain the conversion of BN2C groups into BN3 and ÂÂÂÂ"freeÂÂÂÂ" carbon. Such structure evolution is believed to be the reason that the crystallization of Si4.0B1.0 ceramics starts at 1500 °C, whereas Si2.0B1.0 ceramics is stable upto 1600 °C.
Title: THE FABRICATION OF POLYMER-DERIVED SICN/SIBCN CERAMIC NANOSTRUCTURES AND INVESTIGATION OF THEIR STRUCTURE-PROPERTY RELATIONSHIP.
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Name(s): Sarkar, Sourangsu, Author
Zhai, Lei, Committee Chair
University of Central Florida, Degree Grantor
Type of Resource: text
Date Issued: 2010
Publisher: University of Central Florida
Language(s): English
Abstract/Description: Polymer-derived Ceramics (PDCs) represent a unique class of high-temperature stable materials synthesized directly by the thermal decomposition of polymers. This research first focuses on the fabrication of high temperature stable siliconcarbonitride (SiCN) fibers by electrospinning for ceramic matrix composite (CMC) applications. Ceraset™ VL20, a commercially available liquid cyclosilazane, was functionalized with aluminum sec-butoxide in order to be electrospinnable. The surface morphology of the electrospun fibers was investigated using the fibers produced from solvents. The electrospun fibers produced from the chloroform/N,N-dimethylformamide solutions had hierarchical structures that led to superhydrophobic surfaces. A ÂÂÂÂ"dry skinÂÂÂÂ" model was proposed to explain the formation of micro/- and nanostructures. The second objective of the research is to align the multiwalled carbon nanotubes (MWCNTs) in PDC fibers. For this purpose, a non-invasive approach to disperse carbon nanotubes in polyaluminasilazane chloroform solutions was developed using a conjugated block copolymer synthesized by ATRP. The effect of the polymer and CNT concentration on the fiber structure and morphology was also examined. Detailed characterization using SEM and TEM was performed to demonstrate the orientation of CNTs inside the ceramic fibers. Additionally, the electrical properties of the ceramic fibers were investigated. Finally, the structural evolution of polymer-derived amorphous siliconborocarbonitride (SiBCN) ceramics with pyrolysis temperatures was studied by solid-state NMR, Raman and EPR spectroscopy. Results suggested the presence of three major components: (i) hexagonal boron nitride (h-BN), (ii) turbostratic boron nitride (t-BN), and (iii) BN2C groups in the final ceramic. The pyrolysis at higher temperature generated boron nitride (BN3) with a simultaneous decomposition of BN2C groups. A thermodynamic model was proposed to quantitatively explain the conversion of BN2C groups into BN3 and ÂÂÂÂ"freeÂÂÂÂ" carbon. Such structure evolution is believed to be the reason that the crystallization of Si4.0B1.0 ceramics starts at 1500 °C, whereas Si2.0B1.0 ceramics is stable upto 1600 °C.
Identifier: CFE0003446 (IID), ucf:48408 (fedora)
Note(s): 2010-12-01
Ph.D.
Sciences, Department of Chemistry
Masters
This record was generated from author submitted information.
Subject(s): Polymer-Derived Ceramics
Poly(organosilazanes)
Poly(organoborosilazanes)
Siliconcarbonitride
Siliconborocarbonitride
Electrospinning
Carbon Nanotubes
Free Carbon
Dangling Bonds
Electron Paramagnetic Resonance
Persistent Link to This Record: http://purl.flvc.org/ucf/fd/CFE0003446
Restrictions on Access: public
Host Institution: UCF

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