Single walled carbon nanotubes (SWCNTs) are carbon based nanostructures with extraordinary electronical and mechanical properties. They are used in a wide range of applications, usually embedded in polymer as fillers to form polymer based nanocomposites, in order to affect the electronic behavior of the polymer matrix. However, as the nanotubes properties are directly dependent on their intrinsic structure, it is necessary to select specific nanotubes depending on the application. In addition, as randomly oriented CNTs (as Filler) embedded in the polymer matrix show lower electrical conductivity than expected, alignment of CNTs in the polymer matrix can help to improve the nanocomposite electrical conductivity. In this thesis, focus is placed on the electrical properties of the produced SWCNTs/Polymer nanocomposites. A simple patterning method called nanoimprint lithography is presented which allows the use of extremely low amounts of nanotubes in order to increase the electrical conductivity of isolated polymers such as polystyrene (PS). In addition, a flexible mold to pattern nanocomposite films, leading to the creation of conducting nanotube networks, resulting in Alignment of SWCNTs (from the bottom of the film to the top of the imprinted patterns) inside the polymer matrix. The project further investigated the effect of different imprint temperatures and pressures on the electrical conductivity of produced nanocomposite and a trend is found due to the variation of parameters. Finally an optimum imprint condition based on maximum achieved conductivity is suggested. During different steps of sample preparations, the samples were characterized by different microscopic and spectroscopic techniques such as Atomic Force Microscopy (AFM), optical microscopy, Spectroscopic Ellipsometer, electrical measurements and Raman spectroscopy.

Zero-valent iron (ZVI) has been successfully used for the degradation of a wide range of organic contaminants in groundwaters in recent years. The rate of degradation of contaminants by ZVI may be enhanced by use of nanoscale zero valent iron (nZVI) particles which possess higher surface area than the more widely used granular materials. However, the most widely used method of producing nZVI involves the reduction of FeIII by sodium borohydride is expensive. Dithionite can be used to reduce Fe(II) and produce cost effective nZVI under conditions of high pH and in the absence of oxygen. The efficiency of trichloroethylene (TCE) degradation using dithionite nZVI particles (nZVIS2O4) is similar to that of the conventional borohydride particles (nZVIBH4). Oxidation of benzoic acid using the nZVIS2O4 particles results in different byproducts than those produced when nZVIBH4 particles are used. The high concentration of phenol compared to hydroxybenzoic acids suggests that OH addition is not the primary oxidation pathway when one is using the nZVIS2O4 particles. It is proposed that sulfate radicals (SO4−) are produced as a result of hydroxyl radical attack on the sulfite matrix surrounding the nZVIS2O4 particles, with these radicals oxidizing benzoic acid via electron transfer reactions rather than addition reactions. Low yields of oxidants limit the application of nZVI. It has recently been demonstrated that nZVI oxidative efficiency can be enhanced in presence of ethlylendiaminetetraacetic acid (EDTA). Additional insight into the nZVI-mediated process has been obtained from comparative studies of degradation of benzoic acid by nZVI particles and Fenton reagents in the absence and presence of EDTA at different pH. The efficiency of nZVI degradation is significantly hindered by the rapid aggregation of the iron nanoparticles, which may result in a decrease in available reactive surface area. These effects of aggregation can be overcome by surface modification through adsorption of capping agents which provide steric and electrosteric repulsive interactions between particles. Several high molecular weight (HMW) organic polymers have been used for preventing agglomeration of nZVI particles, such as water soluble starch, sodium carboxymethyl cellulose (CMC) and alginate. The degradation capabilities of different functionalized nZVIS2O4 particle were investigated. Iron-based bimetallic particles in which metals such as Pd and Ni have been combined with Fe, have been found to both enhance rates of halogenated organic contaminants reduction and generate more fully dehalogenated products relative to unamended iron. The results presented in this thesis demonstrate that formation of bimetallic particles with nZVI formed from the more cost effective dithionite reduction of ferrous salts also results in dramatic enhancement in reducing ability. The oxidising ability of nZVIBH4 particles can be enhanced dramatically by addition of polyoxometallates (POMs), redox catalysts which result in enhanced production of hydrogen peroxide. The extent of enhancement is quantified by examination of the oxidation of formic acid (to CO2) and kinetic modelling of the results obtained used to investigate the mechanism of the POM-mediated oxidation process.

In the past, hardness measurements on nanocrystalline metals were limited to Vickers micro-hardness and nano-indentation tests, mainly due to sample size/thickness limitations. On the other hand, most industries require hardness values on the Rockwell scale and make extensive use of hardness conversion relationships for various hardness scales. However, hardness conversions currently do not exist for nanocrystalline metals. With recent advances in electrodeposition technology, thicker specimens with a wide range of grain sizes can now be produced. In this study, the relationships between Vickers and Rockwell hardness scales have been developed for such materials. In addition, hardness indentations were used to gain further insight into the work hardening of nanocrystalline and polycrystalline nickel. Vickers microhardness and nano-indentation profiles below large Rockwell indentations showed that polycrystalline nickel exhibited considerable strain hardening, as expected. On the other hand, for nanocrystalline nickel the micro-Vickers and nano-indentations hardness profile showed low strain hardening capacity.

In the past, hardness measurements on nanocrystalline metals were limited to Vickers micro-hardness and nano-indentation tests, mainly due to sample size/thickness limitations. On the other hand, most industries require hardness values on the Rockwell scale and make extensive use of hardness conversion relationships for various hardness scales. However, hardness conversions currently do not exist for nanocrystalline metals. With recent advances in electrodeposition technology, thicker specimens with a wide range of grain sizes can now be produced. In this study, the relationships between Vickers and Rockwell hardness scales have been developed for such materials. In addition, hardness indentations were used to gain further insight into the work hardening of nanocrystalline and polycrystalline nickel. Vickers microhardness and nano-indentation profiles below large Rockwell indentations showed that polycrystalline nickel exhibited considerable strain hardening, as expected. On the other hand, for nanocrystalline nickel the micro-Vickers and nano-indentations hardness profile showed low strain hardening capacity.

The effect of silica nanoparticles on corrosion of steel by molten carbonate eutectic (42.7 percent Li2CO3, K2CO3) was investigated. The experimental design was based on static coupon immersion methodology where a coupon (material under study, in this case a rectangular stainless steel specimen of SS304 with dimensions approximately 5X20X.6mm and weight .5gm) is exposed to a static corroding environment for predetermined periods of time. The testing times were 2, 4 and 6 weeks. The temperature during testing was maintained at a constant 520C. The instantaneous corrosion rates were determined by normalizing the mass loss with respect to time and area. The mass loss was determined by descaling the corroded steel coupons using concentrated hydrochloric acid. The instantaneous corrosion rates obtained from all three times showed a reduction in corrosion of steel by molten carbonate eutectics when doped with silica 1 percent by weight in comparison to the molten base carbonate eutectics. The results showed that doping the carbonate eutectic with silica nanoparticles (1 percent by weight) reduced the corrosion of steel by half in comparison to the corrosion without doping.

Recently, the skills to reduce the solar cell reflectance at oblique incidence to enhance the overall efficiency of solar cells attracted much attention. the relationships between geometric structures, aspect ratios (depth over width) and sizes of the anti-reflective film (AR film) with the angles of incidence by using an optical simulation software "TracePro ". Simulation results showed that the anti-reflection effect produced by the trench structure is much lower than that of the plane structure. Structure of the higher aspect ratio and smaller size can also be effective in improving anti-reflection. PDMS was chosen as the material to construct an anti-reflective layer. Then, the study used optic lithography techniques to produce square-column structures with aspect ratios of 0.5 and 2 and also four pyramid structures of sizes 20,40,60,80 microns. Using a solar simulator we measured and calculated efficiency in generation of power with respect to different angles of incidence. At angle of incidence at 60 degrees, structure with aspect ratio of 2 obtained 14.7% higher efficiency in power generation than that of structure with ratio of 0.5. Decrease in size also enhanced efficiency. Also at 60 degrees of incidence, pyramid structure of 20um obtained over 19.6% of generating capacity than that of pyramid structure of 80um . At last, etching of PDMS surface was completed using carbon tetra fluoride (CF4) plasma. The PDMS surface thus became random nano-structure. Using Electron microscopy, the desired feature was discovered to become a micron-level structure if the processing time of plasma etching exceeds 4 hours. Two types of structures were produced by CF4 plasma etching, that by processing time of 2 hours and 4 hours on the AR film, respectively. At a 60-degree angle of incidence, AR film by 4 hours of etching obtained 18.8% greater generating capacity than that of AR film by 2 hours of etching.

Nano-ESI mass spectrometry is an attractive analytical technique due to its high sensitivity and small sample consumption, which is especially important for research areas such as proteomics. However, current nano-ESI emitters become a bottleneck for nano-ESI to be widely applied because of problems such as clogging, poor robustness, large flow resistance, and poor spray efficiency for highly aqueous solutions. The objective of this thesis study is to address the problems associated with tapered emitters and provide alternative solutions by developing advanced nano-ESI emitters. Two strategies that were explored to improve the clogging resistance and robustness while maintaining comparable electrospray performances include the development of emitters with larger apertures and multiple channels. Following these strategies, five types of emitters were fabricated without tapering either internal or external diameters, which include a roughened open tubular emitter, a porous membrane-assisted emitter, a microstructured multiple channel photonic crystal fiber (MSF) emitter, a packed ODS bead emitter, and an entrapped ODS bead emitter. The successful transformation of MSF fibers to nanoelectrospray emitters demonstrates a new practical approach to expand the application of nano-ESI because of its availability, compatibility, precisely controlled channel dimensions, variety of channel patterns, and feasibility for surface modification. The fundamental mechanism of non-tapered emitters was studied at nano flow rates. The fact that a plume of mist, instead of single Taylor cone, is generated from multiple channel emitters at nano flow rates suggests multiple Taylor cones may be formed. The calculated sensitivity gains from a MSF emitter compared to a single-tip tapered emitter are related to the number of the orifices containing on a MSF emitter. The characterization of impacts of operational parameters on nanoelectrospray performances shows that non-tapered emitters are more robust and less dependent on the emitter’s fine positioning. It was also found that unlike tapered emitters, non-tapered emitters can be positioned ten times further from the orifice of a mass spectrometer, which is greatly beneficial to online sample manipulation and purification. Furthermore, the electrospray efficiency of spraying highly aqueous solutions (e.g. 90%) was greatly improved through the hydrophobic modification of a MSF emitter exit. / Thesis (Ph.D, Chemistry) -- Queen's University, 2008-09-17 19:07:12.847

Research work on fabricating organized and reproducible SERS substrates has been done in this thesis. Nano-aperture arrays with circular, bow-tie and cross bow-tie shapes were fabricated by using FIB milling. These arrays were imaged under SEM and their parameters were measured. The optical transmission properties of these arrays were measured by white light transmission. It was found that the shape of the nano-aperture could determine these arrays’ abilities to support SPR. Different shapes would give different SPR modes and generated optical transmission peaks at varied wavelengths. For nano-aperture array with identical shapes, the varied parameters, such as periodicity or tip-to-tip distances, would affect the position of the transmission peaks. Slight increase or decrease of these parameters can be manipulated to adjust the peak positions, catering to the best resonance of the excitation laser used in Raman spectroscopy. The enhancement properties of these arrays as SERS substrates were measured by Raman spectroscopy. Different SERS enhancement properties could be found across different shaped nano-aperture arrays and cross bow-tie nano-aperture arrays give the best SERS enhancement. For nano-aperture array with identical shapes, the varied parameters would affect its ability of SERS enhancement. Near field simulations were carried out in order to explain the relationship of the SERS results and these arrays’ SPR ability. Electrochemical study on these ordered nano-aperture arrays was also carried out in this thesis. / Graduate

Zero-valent iron (ZVI) has been successfully used for the degradation of a wide range of organic contaminants in groundwaters in recent years. The rate of degradation of contaminants by ZVI may be enhanced by use of nanoscale zero valent iron (nZVI) particles which possess higher surface area than the more widely used granular materials. However, the most widely used method of producing nZVI involves the reduction of FeIII by sodium borohydride is expensive. Dithionite can be used to reduce Fe(II) and produce cost effective nZVI under conditions of high pH and in the absence of oxygen. The efficiency of trichloroethylene (TCE) degradation using dithionite nZVI particles (nZVIS2O4) is similar to that of the conventional borohydride particles (nZVIBH4). Oxidation of benzoic acid using the nZVIS2O4 particles results in different byproducts than those produced when nZVIBH4 particles are used. The high concentration of phenol compared to hydroxybenzoic acids suggests that OH addition is not the primary oxidation pathway when one is using the nZVIS2O4 particles. It is proposed that sulfate radicals (SO4−) are produced as a result of hydroxyl radical attack on the sulfite matrix surrounding the nZVIS2O4 particles, with these radicals oxidizing benzoic acid via electron transfer reactions rather than addition reactions. Low yields of oxidants limit the application of nZVI. It has recently been demonstrated that nZVI oxidative efficiency can be enhanced in presence of ethlylendiaminetetraacetic acid (EDTA). Additional insight into the nZVI-mediated process has been obtained from comparative studies of degradation of benzoic acid by nZVI particles and Fenton reagents in the absence and presence of EDTA at different pH. The efficiency of nZVI degradation is significantly hindered by the rapid aggregation of the iron nanoparticles, which may result in a decrease in available reactive surface area. These effects of aggregation can be overcome by surface modification through adsorption of capping agents which provide steric and electrosteric repulsive interactions between particles. Several high molecular weight (HMW) organic polymers have been used for preventing agglomeration of nZVI particles, such as water soluble starch, sodium carboxymethyl cellulose (CMC) and alginate. The degradation capabilities of different functionalized nZVIS2O4 particle were investigated. Iron-based bimetallic particles in which metals such as Pd and Ni have been combined with Fe, have been found to both enhance rates of halogenated organic contaminants reduction and generate more fully dehalogenated products relative to unamended iron. The results presented in this thesis demonstrate that formation of bimetallic particles with nZVI formed from the more cost effective dithionite reduction of ferrous salts also results in dramatic enhancement in reducing ability. The oxidising ability of nZVIBH4 particles can be enhanced dramatically by addition of polyoxometallates (POMs), redox catalysts which result in enhanced production of hydrogen peroxide. The extent of enhancement is quantified by examination of the oxidation of formic acid (to CO2) and kinetic modelling of the results obtained used to investigate the mechanism of the POM-mediated oxidation process.

In this master thesis the effects of the process parameters of pp-HMDSO were studied in the application of corrosion protection of an Al surface. The method for polymerising the HMDSO vapour was RF-PECVD. The following process parameters were studied: RF-power, flow of HMDSO, Oxygen as reactive gas, Ar as inert gas, the effect of applied bias voltage, as well as Ar etch as pre-treatment and subjecting the film to a pure O2 plasma as post-treatment. The results were a prolonging of the total decay time of the Al film when subjected to a 1M NaOH solution. The decay time increased from 5-20s for an unprotected Al film to 140min for the best pp-HMDSO coating. SEM/EDX, XRR, L*a*b* were used when analysing the pp-HMDSO films. The best performing coatings were tested on reflectors and passed the industry standard test of being subjected to a 0.1M NaOH for 5min without visible corrosion or decay.