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Dissertation
Chemically modified carbon nanostructures for electrospun thin film polymer-nanocomposites
Doctor of Philosophy (Ph.D.), Drexel University
Oct 2008
DOI:
https://doi.org/10.17918/etd-2920
Abstract
Various nano-structured carbon materials, most notably carbon nanotubes (CNTs) and nanodiamonds (NDs), are used in preparing polymer-nanocomposites. Surfacemodified NDs, multi-walled (MWCNT), double-walled (DWCNT) and triple-walled (TWCNT) have been incorporated into polymer matrix systems. Treatments include vacuum annealing, thermal oxidation in air and acid treatments (nitric and sulfuric acids for the CNTs and hydrochloric acid for NDs). Acid treatments have led to carboxylic group formation on the surface of CNTs and NDs, promoting improved dispersion. As-received, thermal and acid treated MWCNTs have been incorporated into polyvinylidene fluoride and polyamide-11 and -12 electrospun nanofibers with little improvements in the electrical conductivity. To improve the electrical properties of CNTpolyamide composites, negatively charged CNTs were self-assembled on the nanofiber's surface. At a 2 wt% loading, the electrical resistance of the nanofibers decreased two orders of magnitude (to 154 k[omega]/sq) by increasing the number of MWCNT self-assembly depositions and then another three orders of magnitude by using DWCNTs (700 [omega]/sq). Further heat treatments were used to fuse (110°C) and completely remove the nanofibers (450°C) to produce ~150 nm coatings with improved transparency, ~96% transmission, in the visible spectrum. HCl-purified NDs have also been successfully incorporated in polyamide 11 and polyacrylonitrile nanofibers leading to improvements in the mechanical properties of thefibers. Extremely high loadings of up to 90 wt% ND in the polymer have also been achieved. The Young's modulus of the ND-polyamide-11 composites increased by afactor of four, the hardness doubled and the scratch resistance was improved such that a load three times larger than used on the pure polymer was required to generate a scratch of the identical depth in the composite material. The ND-polymer films have shown about a 50% decrease in transmission in the UV-range, making these thin filmsapplicable in UV protection. Multi-layered structures were produced by using alternating thin films of NDpolymer and CNT-polymer nanofibers. These multi-layers have shown electrical resistances on par with the single-layered films as well as the same improvement in hardness, Young's modulus and scratch resistance making them attractable for multifunctionalcomposites.
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Details
- Title
- Chemically modified carbon nanostructures for electrospun thin film polymer-nanocomposites
- Creators
- Kristopher Behler - DU
- Contributors
- Yury Gogotsi (Advisor) - Drexel University (1970-)
- Awarding Institution
- Drexel University
- Degree Awarded
- Doctor of Philosophy (Ph.D.)
- Publisher
- Drexel University; Philadelphia, Pennsylvania
- Resource Type
- Dissertation
- Language
- English
- Academic Unit
- Materials (Science and) Engineering (Metallurgical Engineering) [Historical]; College of Engineering (1970-2026); Drexel University
- Other Identifier
- 2920; 991014632267104721