High-power diode lasers (HPDL) are being increasingly used in industrial applications. Deposition of nickel from nickel carbonyl (Ni(CO)4) precursor by laser-induced chemical vapor deposition (CVD) was studied with emphasis on achieving high deposition rates. An HPDL system was used to provide a novel energy source facilitating a simple and compact design of the energy delivery system. Nickel deposits on complex, 3-dimensional polyurethane foam substrates were prepared and characterized. The resulting “nickel foam” represents a novel material of high porosity (>95% by volume) finding uses, among others, in the production of rechargeable battery and fuel cell electrodes and as a specialty high-temperature filtration medium. Deposition rates up to ~19 µm/min were achieved by optimizing the gas precursor flow pattern and energy delivery to the substrate surface using a 480W diode laser. Factors affecting the transition from purely heterogeneous decomposition to a combined hetero- and homogeneous decomposition of nickel carbonyl were studied. High quality, uniform 3-D deposits produced at a rate more than ten times higher than in commercial processes were obtained by careful balance of mass transport (gas flow) and energy delivery (laser power). Cross-flow of the gases through the porous substrate was found to be essential in facilitating mass transport and for obtaining uniform deposits at high rates. When controlling the process in a transient regime (near the onset of homogenous decomposition), unique morphology features formed as part of the deposits, including textured surface with pyramid-shape crystallites, spherical and non-spherical particles and filaments. Operating the laser in a pulsed mode produced smooth, nano-crystalline deposits with sub-100 nm grains. The effect of H2S, a commonly used additive in nickel carbonyl CVD, was studied using both polyurethane and nickel foam substrates. H2S was shown to improve the substrate coverage and deposit uniformity in tests with polyurethane substrate, however, it was found to have no effect in improving the overall deposition rate compared to H2S-free deposition process. Deposition on other selected substrates, such as ultra-fine polymer foam, carbon nanofoam and multi-wall carbon nanotubes, was demonstrated. The HPDL system shows good promise for large-scale industrial application as the cost of HPDL energy continues to decrease.

High-power diode lasers (HPDL) are being increasingly used in industrial applications. Deposition of nickel from nickel carbonyl (Ni(CO)4) precursor by laser-induced chemical vapor deposition (CVD) was studied with emphasis on achieving high deposition rates. An HPDL system was used to provide a novel energy source facilitating a simple and compact design of the energy delivery system. Nickel deposits on complex, 3-dimensional polyurethane foam substrates were prepared and characterized. The resulting “nickel foam” represents a novel material of high porosity (>95% by volume) finding uses, among others, in the production of rechargeable battery and fuel cell electrodes and as a specialty high-temperature filtration medium. Deposition rates up to ~19 µm/min were achieved by optimizing the gas precursor flow pattern and energy delivery to the substrate surface using a 480W diode laser. Factors affecting the transition from purely heterogeneous decomposition to a combined hetero- and homogeneous decomposition of nickel carbonyl were studied. High quality, uniform 3-D deposits produced at a rate more than ten times higher than in commercial processes were obtained by careful balance of mass transport (gas flow) and energy delivery (laser power). Cross-flow of the gases through the porous substrate was found to be essential in facilitating mass transport and for obtaining uniform deposits at high rates. When controlling the process in a transient regime (near the onset of homogenous decomposition), unique morphology features formed as part of the deposits, including textured surface with pyramid-shape crystallites, spherical and non-spherical particles and filaments. Operating the laser in a pulsed mode produced smooth, nano-crystalline deposits with sub-100 nm grains. The effect of H2S, a commonly used additive in nickel carbonyl CVD, was studied using both polyurethane and nickel foam substrates. H2S was shown to improve the substrate coverage and deposit uniformity in tests with polyurethane substrate, however, it was found to have no effect in improving the overall deposition rate compared to H2S-free deposition process. Deposition on other selected substrates, such as ultra-fine polymer foam, carbon nanofoam and multi-wall carbon nanotubes, was demonstrated. The HPDL system shows good promise for large-scale industrial application as the cost of HPDL energy continues to decrease.

The process of vapor extraction (VAPEX) is a recovery process which targets the heavy oil and bitumen resources. Owing to high viscosity values for these unconventional types of oil, the recovery processes in such reserves are still challenging. The unconventional oil recovery processes usually include a mechanism for reducing the oil viscosity by means of heat, solvent, or both. The process of VAPEX utilizes the injection of a light hydrocarbon solvent into a reservoir for recovering the viscous oil in place by diffusing into the oil and by providing sufficient mobility to the oil upon dilution. Although this process offers a variety of advantages over the alternative thermal recovery processes such as SAGD or CSS, it suffers from two major drawbacks. First, the oil production rates obtained in the VAPEX process are considerably lower than those obtained in the thermal processes. Second, the solvent cost is considerably high. We tried to tackle these two problems during this research and we searched for potentials for an improved VAPEX process. Three potentially improved occurrences of a VAPEX project were found when: 1) the injected solvent was superheated, 2) the wettability of media was altered to oil-wet, and 3) the vugs were distributed in the porous media. Warm VAPEX process is introduced in which the VAPEX process is thermally augmented through superheating the solvent vapor. An attractive feature of this process is the capability of the solvent in being able to condense at the bitumen-solvent interface, which provides the opportunity for the bitumen to be upgraded in-situ through asphaltene precipitation. The asphaltene precipitation was not observed during the conventional vapor extraction process and was only observed during the warm VAPEX process. Upon a moderate level of superheating, the production rate of bitumen was sufficiently improved while the solvent content of the produced oil was significantly decreased as a result of decreased solubility of solvent in the oil at elevated temperatures. Therefore, more oil was produced at lower costs. The warm VAPEX experiments were conducted at 4 temperature levels in high and low permeability media using Cold Lake bitumen and Lloydminster heavy oil blend, n-pentane was used as solvent. The warm VAPEX process was found to be more effective for Cold Lake bitumen and for less permeable media. The potential of in-situ upgrading decreased when the level of superheating increased. The second potential for an improved VAPEX process obtained when the wettability of porous medium was altered to oil-wet conditions. Although this wettability condition is harmful to steam-based recovery processes, such as SAGD, it becomes beneficial to VAPEX. For the application of VAPEX process in fractionally wet media the wettability of glass beads was altered to oil-wet conditions through silylation process, and the VAPEX experiments were conducted in a random packing of water-wet and oil-wet beads of similar size at 7 different compositions. A substantial increase in the oil production rate was observed in a completely oil-wet medium, compared to the water-wet medium. By increasing the fraction of oil-wet beads in the packing up to a critical composition, the production rate of live oil increased linearly with the increase in the fraction of oil-wet beads in the packing during the vapor extraction process. Beyond this critical composition, however, the production rate of live oil did not change significantly with further increase in the fraction of the oil-wet beads in the randomly packed medium. Vugs were also found to be beneficial to the production performance of the VAPEX process. The presence of vugs was investigated in synthesized vugular media at 4 different levels of vuggy-to-total pore volume ratios. The performance of vugular media was compared to that of the homogeneous sintered media. The vugs facilitated the production of oil during the VAPEX process by providing flow communication between the vugs and the surrounding matrix, and therefore, by providing a local high permeability pathways towards the production well. A peak in the oil production rate was observed whenever a series of vugs were simultaneously invaded by the solvent vapor. The overall production rate of oil was higher in vuggy media compared to a homogeneous media at the same overall porosity and permeability. Furthermore, the magnitude of residual oil saturation left behind was also slightly lower in vuggy medium because the vugs were perfectly drained. Finally, a constant rate air injection (CRAI) porosimetry method was developed for characterization of vugs in a vugular media. This method was successfully tested in different synthetic vugular media, and the results illustrated higher accuracy in CRAI porosimetry method compared to constant rate mercury porosimetry. CRAI porosimetry method was also employed for identification of higher permeability regions embedded in a matrix of lower permeability. The analysis of a typical porosimetry signal was also modified.

Piezoelectric actuators (PEA) hold the most promise for precision positioning applications due to their capability of producing extremely small displacements down to 10 pm (1 pm = 10-12 m) as well as their high stiffness and force output. The piezoelectric-driven stick-slip (PDSS) actuator, working on the friction-inertia concept, has the capacity of accomplishing an unlimited range of motion. It also holds the promises of simple configuration and low cost. On the other hand, the PDSS actuator has a relatively low efficiency and low loading capability, which greatly limits its applications. The purpose of this research is to improve the performance of the PDSS actuators by employing specially-designed working surfaces.<p> The working surfaces, referred as anisotropic friction (AF) surfaces in this study, can provide different friction forces depending on the direction of relative motion of the two surfaces, and are used in this research to accomplish the aforementioned purpose. To fabricate such surfaces, two nanostructure technologies are employed: hot filament chemical vapour deposition (HFCVD) and ion beam etching (IBE). The HFCVD is used to deposit diamond on silicon substrates; and the IBE is used to etch the diamond crystalloid with a certain angle with respect to the coating surface to obtain an unsymmetrical-triangle microstructure. <p> A PDSS actuator prototype containing the AF surfaces was developed in this study to verify the function of the AF surfaces and characterize the performance of PDSS actuators. The designed surfaces were mounted on the prototype; and the improvement in performance was characterized by conducting a set of experiments with both the normal isotropic friction (IF) surfaces and the AF surfaces, respectively. The results illustrate that the PDSS actuator with the AF surface has a higher efficiency and improved loading capability compared to the one with the IF surfaces.<p> A model was also developed to represent the displacement of the novel PDSS actuator. The dynamics of the PEA and the platform were approximated by using a second order dynamic system. The pre-sliding friction behaviour involved was investigated by modifying the LuGre friction model, in which six parameters (Note that three parameters are used in the LuGre model) were employed to represent the anisotropic friction. By combining the PEA mechanism model, the modified friction model, and the dynamics of end-effector, a model for the PDSS actuator with the AF surface was developed. The model with the identified parameters was simulated in MATLAB Simulink and the simulation results obtained were compared to the experimental results to verify the model. The comparison suggests that the model developed in this study is promising to represent the displacement of the novel PDSS actuators with AF surfaces.

Chemical vapor deposition (CVD) has been the main method for synthesizing diamond thin films on hetero substrate materials since 1980s. It has been well acknowledged that both nucleation and growth of diamond on non-diamond surfaces without pre-treatment are very difficult and slow. Furthermore, the weak adhesion between the diamond thin films and substrates has been a major problem for widespread application of diamond thin films. Up to now, Si has been the most frequently used substrate for the study of diamond thin films and various methods, including bias and diamond powder scratching, have been applied to enhance diamond nucleation density. In the present study, nucleation and growth of diamond thin films on Ti3SiC2, a newly developed ceramic-metallic material, using Microwave Plasma Enhanced (MPE) and Hot-Filament (HF) CVD reactors were carried out. In addition, synchrotron-based Near Edge Extended X-Ray Absorption Fine Structure Spectroscopy (NEXAFS) was used to identify the electronic and chemical structures of various NCD films. The results from MPECVD showed that a much higher diamond nucleation density and a much higher film growth rate can be obtained on Ti3SiC2 compared with on Si. Consequently, nanocrystalline diamond (NCD) thin films were feasibly synthesized on Ti3SiC2 under the typical conditions for microcrystalline diamond film synthesis. Furthermore, the diamond films on Ti3SiC2 exhibited better adhesion than on Si. The early stage growth of diamond thin films on Ti3SiC2 by HFCVD indicated that a nanowhisker-like diamond-graphite composite layer, different from diamond nucleation on Si, initially formed on the surface of Ti3SiC2, which resulted in high diamond nucleation density. These results indicate that Ti3SiC2 has great potentials to be used both as substrates and interlayers on metals for diamond thin film deposition and application. This research may greatly expand the tribological application of both Ti3SiC2 and diamond thin films. The results demonstrated that NEXAFS is a reliable and powerful tool to identify NCD films.

<p>Controlling the properties of single walled carbon nanotubes (SWNTs) is the major challenge toward their future applications. This dissertation describes several contributions to this chanllenge. </p><p>This dissertation begins with the brief review on carbon nanotubes (CNTs), including discovery, structure, properties, challenges, synthesis and applications. The remaining parts can be divided into three sections. They demonstrate the control of SWNT properties as well as their devices by direct synthesis and metal decoration. </p><p>Two studies are described on the control of SWNT properties by direct synthesis. The first demonstrates the controlled synthesis of SWNTs in terms of their diameter, uniformity, and density by the chemical vapor deposition (CVD) method. The approaches employed include using uniform nanoparticles with specific sizes as catalysts to grow different diameter SWNTs, specially small diameter tubes less than 1 nm; using laser irradiation to grow uniform and high quality SWNTs; and changing the gas flow pattern to obtain different density. The second study demonstrates the growth of aligned SWNTs by flow and substrate guidance. Horizontally aligned ultralong nanotubes are synthesized on Si substrate by both high flow and low flow. The guided growth by the quartz substrate is shown by a large variety of metal catalysts to further the understanding of the growth mechanism. Moreover, top gated FETs have been explored for the selective growth of purely semiconducting, horizontally aligned SWNTs grown on quartz by a ethanol/methanol mixture. </p><p>The control of SWNT device performance is also described, in particular, the correlation between the SWNT field effect transistor (FET) configuration and its gate dependence response. The effects of FET channel length, nanotube density and diameter on the device performance are demonstrated. A model has been constructed in order to simulate the electronic behavior. An interesting metallic behavior has been observed. </p><p>Finally, control of SWNT properties by Palladium decoration after growth is used to manipulate their properties. Moreover, two novel applications including improvement of carbon nanotube film conductivity and catalysis of nanostructure growth are developed.</p> / Dissertation

The primary goal of this research was to develop the laser chemical vapor deposition (LCVD) process to be able to directly deposit carbon nanotubes onto substrates selectively. LCVD has traditionally been used to directly deposit complex geometries of other materials, including many metals and ceramics. Carbon nanotube deposits were formed using codeposition and other techniques. Multiwall carbon nanotubes as small as 7 nm were synthesized. Utilizing electron microscopy, deposits were characterized to determine the effects of laser power, catalyst and hydrocarbon concentration, time, pressure, and other variables on the number of nanotubes formed, their size, and their spatial location. The most important variables were shown to be hydrocarbon and catalyst concentration and laser power. These results were analyzed and statistics based models were developed to express these trends. Additionally, the process was also used successfully to deposit linear patterns of carbon nanotubes. Carbon nanotube deposits were also carried out in the presence of an electric field. It was demonstrated that a field of sufficient strength could be used to orient tube growth. LCVD is a thermally driven process and a thermal feedback and control system is typically employed to allow for real time control of the reaction zone temperatures. The current thermal imaging system installed on the LCVD reactor is limited to operation at temperatures above which nanotube deposition occurs. A heat and mass transport model was therefore developed to simulate deposition temperatures and provide an estimate of the desired laser power needed to achieve a desired reaction temperature. This model included all significant modes of heat transport including conduction, natural convection and radiation. Temperature dependant material properties were also employed to help achieve greater accuracy. Additionally, the model was designed to be able to simulate a scanning laser beam which was used to deposit linear patterns of carbon nanotubes. Modeling calculations of laser heating compared favorably with experimental data. The results of this work show that LCVD has potential for use in the commercial market for selective direct deposition of patterns of aligned carbon nanotubes on multiple substrate materials.

The work conducted in this thesis is two-fold. First, binary vapor liquid equilibria of several solvent/CO2 systems are measured at 40 ?? The systems analyzed are all gas-expanded liquids (GXLs) characterized with a Jerguson Cell apparatus. A Jerguson cell is a windowed pressure vessel that allows one to measure the height of the condensed liquid. Using this height and the known overall contents in the cell, one can calculate the liquid composition without using any external sampling. Secondly, this same setup is attached to a sampling system, and solid solubility (fractional crystallization) is measured for various GXL systems. The CO2 acts as an antisolvent in what is commonly known as a gaseous antisolvent (GAS) system. Essentially, this work shows that expansion of the tested solvents with CO2 will cause the precipitation of the solid solute. This work also analyzes the affect two solutes have on each other in a quaternary GAS system. Gas-expanded liquids combine desirable gaseous properties and liquid properties to yield a very useful solvent for many applications. An advantage of GXLs is that a relatively small change in pressure or temperature can greatly affect the solvation properties. The tunability of GXLs increases as the amount of the gas (usually CO2) increases in the liquid phase. With the benign chemical nature and environmental impact of CO2 processing, GXLs and supercritical fluids (SCFs) have garnered a lot of attention for industry and academia. Supercritical fluids in this work refer to pure CO2 above its critical temperature and pressure.

No description available.

Electron Beam Chemical Vapor Deposition (EBCVD) is a process by which an electron beam is used to decompose adsorbed reagent molecules to produce a deposit. The primary electrons from the beam, and especially the secondary electrons emitted from the substrate, dissociate the adsorbed molecules. Important factors for the deposition process include the beam parameters and reagent gas composition. Simple structures are fabricated through utilization of the various scanning modes of an SEM. Fibers (pillar-like structures) can be deposited, and lines (wall-like structures) can be deposited easily. This investigation focuses on the process parameters controlling deposition rate and geometry for platinum and carbon fibers and lines in a modified SEM. Platinum deposition was performed using a system with a small diameter needle that supplied a localized flow of gas from an organometallic platinum compound. Carbon deposition was performed in the Environmental mode, in which the microscope chamber is filled with a specified pressure of reagent gas. Statistically designed experiments were performed for platinum fiber and line deposition. Analysis indicated that the beam current and deposition time were dominant factors in determining the deposition rate. The voltage also had a significant effect on fiber deposition. For platinum line deposition, the effects of the dwell time and line time were also studied. The line time had a significant effect on line height deposited per scan. Optimization analysis was performed, and results indicated that high voltage and high beam current led to higher aspect ratios. Medium voltage and low beam current were preferable for depositing minimal width lines (less than 200 nm). Low voltage and high beam current were preferable for maximum deposition rates. EDS and EELS performed for platinum deposits in a TEM indicated amorphous structure with no carbon detected. This differs significantly from previously reported results. Statistically designed experiments were performed for carbon line deposition. The voltage, beam current, and dwell/line time were studied. Increasing line time led to a significant increase in line height/scan and appeared to be a dominant factor. Lower beam currents appeared to favor higher deposition rates. TEM analysis indicated that carbon deposits were mostly amorphous.