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- Title
- STRENGTHENING POTENTIAL OF SINGLE-WALLED CARBON NANOTUBES IN PHENOLIC RESIN COMPOSITES.
- Creator
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Kerr, Brittany, Sohn, Yongho, University of Central Florida
- Abstract / Description
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Strengthening potential of single-walled carbon nanotubes (SWCNTs) in a phenolic resin composite was evaluated by characterization of purified and phenyl sulfonated SWCNTs, investigation of the load transfer capability of the purified SWCNTs, and characterization of the composites. Purified and phenyl sulfonated SWCNTs, as well as their composites, were examined by Raman spectroscopy, thermogravimetric analysis, scanning electron microscopy equipped with energy dispersive spectroscopy,...
Show moreStrengthening potential of single-walled carbon nanotubes (SWCNTs) in a phenolic resin composite was evaluated by characterization of purified and phenyl sulfonated SWCNTs, investigation of the load transfer capability of the purified SWCNTs, and characterization of the composites. Purified and phenyl sulfonated SWCNTs, as well as their composites, were examined by Raman spectroscopy, thermogravimetric analysis, scanning electron microscopy equipped with energy dispersive spectroscopy, transmission electron microscopy, X-ray photoelectron spectroscopy and ultra violet-visible spectrometry. Fabrication of the SWCNT/phenolic resin composite was performed by first dispersing the SWCNTs in ethylene glycol and then homogenizing the mixture with phenolic resin. The ethylene glycol was then evaporated from the mixture and the SWCNT/phenolic resin composite was cured at 200°C for 1 hour. The dispersion of SWCNTs in the phenolic resin was reduced with higher SWCNT concentrations. Load was transferred from the phenolic resin to the purified SWCNTs. This demonstrated the potential to strengthen phenolic resin composite with SWCNT reinforcement. The load transfer efficiency in total tension (0.8%) decreased with an increase in SWCNT concentration, while in total compression (-0.8%), the load transfer efficiency remained constant. At very low strain (± 0.2%), the load transfer efficiency remained constant regardless of SWCNT concentration in both tension and compression. Characterization of the phenyl sulfonated SWCNTs indicated that calcium was introduced as a contaminant that interfered with functionalization of the SWCNTs. The use of contaminated phenyl sulfonated SWCNTs resulted in macroscopic inhomogeneity within the composite.
Show less - Date Issued
- 2010
- Identifier
- CFE0003070, ucf:48317
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0003070
- Title
- ARC-DISCHARGE IN SOLUTION: A NOVEL SYNTHESIS METHOD FOR CARBON NANOTUBES AND IN SITU DECORATION OF CARBON NANOTUBES WITH NANOPARTICLES.
- Creator
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Bera, Debasis, Seal, Sudipta, University of Central Florida
- Abstract / Description
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Nanotechnology has reached the status of the 21st century's leading science and technology based on fundamental and applied research during the last two decades. An important feature of nanotechnology is to bridge the crucial dimensional gap between the atomic and molecular fundamental sciences and microstructural scale of engineering. Accordingly, it is very important to have an in-depth understanding of the synthesis of nanomaterials for the use of state-of-the-art high technological...
Show moreNanotechnology has reached the status of the 21st century's leading science and technology based on fundamental and applied research during the last two decades. An important feature of nanotechnology is to bridge the crucial dimensional gap between the atomic and molecular fundamental sciences and microstructural scale of engineering. Accordingly, it is very important to have an in-depth understanding of the synthesis of nanomaterials for the use of state-of-the-art high technological devices with enhanced properties. Recently, the 'bottom-up' approach for the fabrication of nanomaterials has received a great deal of attention for its simplicity and cost effectiveness. Tailoring the various parameters during synthesis of selected nanoparticles can be used to fabricate technologically important components. During the last decade, carbon nanotubes (CNTs) have been envisioned for a host of different new applications. Although carbon nanotubes can be synthesized using a variety of techniques, large-scale synthesis is still a great challenge to the researchers. Three methods are commonly used for commercial and bulk productions of carbon nanotubes: arc-discharge, chemical vapor deposition and laser ablation. However, low-cost, large-scale production of high-quality carbon nanotubes is yet to be reported. One of the objectives of the present research is to develop a simplified synthesis method for the production of large-scale, low-cost carbon nanotubes with functionality. Herein, a unique, simple, inexpensive and one-step synthesis route of CNTs and CNTs decorated with nanoparticles is reported. The method is simple arc-discharge in solution (ADS). For this new method, a full-fledged optoelectronically controlled instrumen is reported here to achieve high efficiency and continuous bulk production of CNTs. In this system, a constant gap between the two electrodes is maintained using a photosensor which allows a continuous synthesis of the carbon nanostructures. The system operates in a feedback loop consisting of an electrode-gap detector and an analogue electronic unit, as controller. This computerized feed system was also used in single process step to produce in situ-decorated CNTs with a variety of industrially important nanoparticles. To name a few, we have successfully synthesized CNTs decorated with 3-4 nm ceria, silica and palladium nanoparticles for many industrially relevant applications. This process can be extended to synthesize decorated CNTs with other oxide and metallic nanoparticles. Sixty experimental runs were carried out for parametric analysis varying process parameters including voltage, current and precursors. The amount of yield with time, rate of erosion of the anode, and rate of deposition of carbonaceous materials on the cathode electrode were investigated. Normalized kinetic parameters were evaluated for different amperes from the sets of runs. The production rate of pristine CNT at 75 A is as high as 5.89 ± 0.28 g.min-1. In this study, major emphasis was given on the characterizations of CNTs with and without nanoparticles using various techniques for surface and bulk analysis of the nanostructures. The nanostructures were characterized using transmission electron microscopy, high resolution transmission electron microscopy, scanning transmission electron microscopy, energy dispersive spectroscopy and scanning electron microscopy, x-ray photo electron spectroscopy, x-ray diffraction studies, and surface area analysis. Electron microscopy investigations show that the CNTs, collected from the water and solutions, are highly pure except the presence of some amorphous carbon. Thermogravimetric analysis and chemical oxidation data of CNTs show the good agreement with electron microscopy analysis. The surface area analysis depicts very high surface area. For pristine multi-walled carbon nanotubes, the BET surface area is approximately 80 m2.g-1. X-ray diffraction studies on carbon nanotubes shows that the products are clean. Nano-sized palladium decorated carbon nanotubes are supposed to be very efficient for hydrogen storage. The synthesis for in-situ decoration of palladium nanoparticles on carbon nanotubes using the arc discharge in solution process has been extensively carried out for possible hydrogen storage applications and electronic device fabrication. Palladium nanoparticles were found to form during the reduction of palladium tetra-chloro-square planar complex. The formation of such a complex was investigated using ultraviolet-visible spectroscopic method. Pd-nanoparticles were simultaneously decorated on carbon nanotubes during the rolling of graphene sheets in the arc-discharge process. Zero-loss energy filtered transmission electron microscopy and scanning transmission electron microscopy confirm the presence of 3 nm palladium nanoparticles. The deconvoluted X-ray photoelectron spectroscopy envelope shows the presence of palladium. Surface area measurements using BET method show a surface area of 28 m2.g-1. The discrepancy with pristine CNTs can be explained considering the density of palladium (12023 kg.m-3). Energy dispersive spectroscopy suggests no functionalization of chlorine to the sidewall of carbon nanotubes. The presence of dislodged graphene sheets with wavy morphology as observed with high-resolution transmission electron microscopy supports the formation of CNTs through the 'scroll mechanism'.
Show less - Date Issued
- 2005
- Identifier
- CFE0000450, ucf:46388
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0000450
- Title
- Electronic Structure of Metal (Al, Cu) Doped Carbon Nanotubes and the Resultant Conduction of the Hybrid Materials.
- Creator
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Jiang, Jingyin, Chen, Quanfang, Zhai, Lei, Fang, Jiyu, Bai, Yuanli, Stolbov, Sergey, University of Central Florida
- Abstract / Description
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Due to the exceptional strength, stiffness and excellent electrical and thermal properties, carbon nanotubes (CNTs) have been regarded as promising candidates for advanced nanoelectronics and multifunctional nanocomposites. In this dissertation, the interaction of CNTs with metals have been investigated and the resultant electrical conduction have been analyzed, aiming to develop innovative avenues to best utilize CNTs' potential. In order to do so, quantum mechanics calculations have been...
Show moreDue to the exceptional strength, stiffness and excellent electrical and thermal properties, carbon nanotubes (CNTs) have been regarded as promising candidates for advanced nanoelectronics and multifunctional nanocomposites. In this dissertation, the interaction of CNTs with metals have been investigated and the resultant electrical conduction have been analyzed, aiming to develop innovative avenues to best utilize CNTs' potential. In order to do so, quantum mechanics calculations have been carried out to study that how to obtain greater electrical conduction by doping metals (Cu, Al) which tailor the electronic structure of three different types of metal-CNT interactions, : 1) encapsulation of atoms inside the CNTs, 2) adsorption of atoms onto CNT surface, and 3) substitutional doping. Models of different doping methods were built and optimized with Density Functional Theory (DFT). And in conjunction with non-equilibrium Green's function, the electronic structure and the conducting properties were then calculated.Through this study, both metallic and semiconducting CNTs have been used. Metallic CNT (5, 5) encapsulated with copper chains have been first investigated with an emphasis on the electronic structure and the resultant conductance. The Density of States (DOS) have showed that the encapsulation of Cu effectively introduced more states around the fermi level. And due to the interaction between copper and CNTs, the conductance of the metallic CNTs-Cu system can be significantly increased.In addition to copper, aluminum has been also introduced for the study. The electronic structure and transport properties of hybrid nanowires consisting of aluminum chains adsorbed on a single-wall semiconducting CNT (10, 0) have been calculated. The band structure and DOS of the hybrid nanowires have showed that the adsorption of Al can effectively reduce the band gap. And with more than 4 Al chains adsorbed, the CNT has transformed from semiconducting to conducting. The transmission eigenstates further indicated that both Al chains and the modified nanotube were responsible for the increased conduction in the hybrid nanowires. The resultant conductance of CNT (10, 0)/Al hybrid nanowire is about 40% greater than that of pure Cu nanowire with the same diameter. In order to utilize the extraordinary conductance in CNT(10,0)/Al hybrid nanowire, it is also important to investigate the end-contact between the hybrid nanowire with Al electrodes. During this work the transmission spectrum at different bias voltage were calculated to study the I-V characteristics and the electrical contact resistances at the interfaces. The results have suggested that the electrical contact resistances between Al electrodes and the hybrid nanowire is significantly lower than that of Al-pure CNT contacts, although the actual contact resistance is directional dependent that the contact resistance is reduced to 20% of that Al-pure CNT along the longitudinal direction.The possibility of substitutional doping of Cu and Al in both metallic and semiconducting CNTs were also investigated. The formation energies have showed that Al doping was more energy favorable than Cu doping in both cases. And by doping of Al or Cu, a metallic tube experienced a higher conductance and a semiconducting tube has transited to conducting.In summary, different doping methods could modify the conducting property of nanotubes. Encapsulation of Cu in metallic CNT results in a significant conductance increment. Adsorption of Al transforms semiconducting CNT to conducting and reduces the contact resistance between the nanowire and Al electrode. Substitutional doping of Cu or Al transits semiconducting nanotube to conducting and enhance the conductance of metallic nanotube.
Show less - Date Issued
- 2017
- Identifier
- CFE0006607, ucf:51274
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0006607
