Optical manipulation of nanoscale objects is studied with particular emphasis on the role of plasmon resonance for enhancement of optical forces. The thesis provides an introduction to plasmon resonance and its role in confinement of light to a sub-diffraction volume. The strong light confinement and related enhancement of optical forces is then theoretically studied for a special case of nanoantenna supporting plasmon resonances. The calculation of optical forces, based on the Maxwell stress tensor approach, reveals relatively weak optical forces for incident powers that are used in typical realisations of trapping with nanoantenna. The optical forces are so weak that other non-optical effects should be considered to explain the observed trapping. These effects include heating induced convection, thermoporesis and chemical binding. The thesis also studies the optical effects of plasmon resonances for a fundamentally different application - size-based optical sorting of gold nanoparticles. Here, the plasmon resonances are not utilised for sub-diffraction light confinement but rather for their ability to increase the apparent cross-section of the particles for their respective resonant sizes. Exploiting these resonances, we realise sorting in a system of two counter-propagating evanescent waves, each at different wavelength that selectively guide gold nanoparticles of different sizes in opposite directions. The method is experimentally demonstrated for bidirectional sorting of gold nanoparticles of either 150 or 130 nm in diameter from those of 100 nm in diameter within a mixture. We conclude the thesis with a numerical study of the optimal beam-shape for optical sorting applications. The developed theoretical framework, based on the force optical eigenmode method, is able to find an illumination of the back-focal plane of the objective such that the force difference between nanoparticles of various sizes in the sample plane is maximised.

Metallic nanostructures that employ localized surface plasmon resonances to capture or radiate electromagnetic waves at optical frequencies are termed "plasmonic optical antennas". These structures enhance light-matter interactions in an efficient manner, enabling unique linear and nonlinear optical applications. One such application is surface-enhanced Raman scattering (SERS), which employs plasmonic antennas to enhance Raman cross-section of molecules by orders of magnitude. SERS has attracted a significant amount of research attention since it enables molecules to be identified through their characteristic vibrational spectra, even at the single molecule level. / Engineering and Applied Sciences

The performance of Enhanced Oil Recovery (EOR) processes is adversely affected by the heterogeneous distribution of flow properties of the rock. The effects of heterogeneity are further highlighted when the mobility ratio between the displacing and the displaced fluids is unfavorable. Polymer flooding aims to mitigate this by controlling the mobility ratio resulting in an increase in the volumetric swept efficiency. However, the design of the polymer injection process has to take into account the uncertainty due to a limited knowledge of the heterogeneous properties of the reservoir. Numerical reservoir models equipped with the most updated, yet uncertain information about the reservoir should be employed to optimize the operational settings. Consequently, the optimal settings are uncertain and should be revised as the model is updated. In this report, a feedback-control scheme is proposed with a model updating step that conditions prior reservoir models to newly obtained dynamic data, and this followed by an optimization step that adjusts well control settings to maximize (or minimize) an objective function. An illustration of the implementation of the proposed closed-loop scheme is presented through an example where the rate settings of a well affected by water coning are adjusted as the reservoir models are updated. The revised control settings yield an increase in the final value of the objective function. Finally, a fast analog of a polymer flooding displacement that traces the movement of random particles from injectors to producers following probability rules that reflect the physics of the actual displacement is presented. The algorithm was calibrated against the full-physics simulation results from UTCHEM, the compositional chemical flow simulator developed at The University of Texas at Austin. This algorithm can be used for a rapid estimation of basic responses such as breakthrough time or recovery factor and to provide a simplified characterization the reservoir heterogeneity. This report is presented to fulfill the requirements to obtain the degree of Master of Science in Engineering under fast track option. It summarizes the research proposal presented for my doctorate studies that are currently ongoing. / text

This thesis explores the use of Raman Spectroscopy to study the battery cathode material LiFePO4. Surface Enhanced Raman Spectroscopy (SERS) was incorporated into the study due to fluorescence that traditionally plagues Raman. By imaging LiFePO4 nanoparticles, an understanding can be gained of the complex chemistry taking place when the material is lithiated and delithiated at the nanoscale level and the phase changes of the material that occur during this process. The use of bimetallic (Au/Ag) SERS substrates allowed for more stable substrates with longer shelf life compared single metal Ag substrates. Further tuning of these substrates can be applied to the ever evolving science of energy storage material technology as a way to track phase changes in the material. / text

Stacked storage systems are a viable carbon management operation, especially in regions with potential growth in CO₂ enhanced oil recovery (EOR) projects. Under a carbon constrained environment, the industrial Texas Gulf Coast is an ideal area for development of stacked storage operations, with a characteristically high CO₂ intensity and abundance of aging oil fields. The development of EOR along the Texas Gulf Coast is limited by CO₂ supply constraints. A stacked storage system is implemented with an EOR project to manage the temporal differences between the operation of a coal-fired power plant and EOR production. Currently, most EOR operations produce natural CO₂ from geologic formations. A switch to anthropogenic CO₂ sources would require an EOR operator to handle volumes of CO₂ beyond EOR usage. The use of CO₂ in an EOR operation is controlled and managed to maximize oil production, but increasing injection rates to handle the volume of CO₂ captured from a coal plant can decrease oil production efficiency. With stacked storage operations, a CO₂ storage reservoir is implemented with an EOR project to maintain injection capacity equivalent to a coal plant's emissions under a carbon constrained environment. By adding a CO₂ storage operation, revenue can still be generated from EOR production, but it is considerably less than just operating an EOR project. The challenge for an efficient stacked storage project is to optimize oil production and maximize profits, while minimizing the revenue reduction of pure carbon sequestration. There is an abundance of saline aquifers along the Texas Gulf Coast, including the Wilcox, Vicksburg, and Miocene formations. To make a stacked storage system more viable and reduce storage costs, maximizing injectivity is critical, as storage formations are evaluated on a cost-per-ton injected basis. This cost-per-ton injected criteria, also established as injection efficiency, incorporates reservoir injectivity and depth dependant drilling costs to determine the most effective storage formation to incorporate with an EOR project. With regionally adequate depth to maximize injectivity while maintaining reasonable drilling costs, the Vicksburg formation is typically the preferred storage reservoir in a stacked storage system along the Texas Gulf Coast. Of the eleven oil fields analyzed on a net present value basis, the Hastings field has the greatest potential for both EOR and stacked storage operations. / text

An analysis that is based on the monitoring of dynamic features from in-situ sensors of an industrial PECVD tool is presented. Linear Discriminant Analysis is used to determine which features are the most sensitive to various changes in the tool condition. The concept of Confidence Values (CVs) is used to quantify statistical changes of these dynamic features as the condition of the tool changed. Two data sets were collected from a PECVD tool in the facilities of a well-known equipment supplier. Dynamic features coming from the RF plasma power and matching capacitors’ sensors are shown to be sensitive to various changes in the cleaning cycles for Si-N, Si-O₂, and TEOS depositions. Quantifying the statistical distributions of the sensitive sensor features during tool condition changes is important for determining which sensor features are necessary to monitor in order to predict the tool chamber health. Results show that these RF plasma sensors could be used to track changes inside the tool chamber. / text

With a number of advantages hitherto unrecognized, nanoparticle-stabilized emulsions and foams have recently been proposed for enhanced oil recovery (EOR) applications. Long-distance transport of nanoparticles is a prerequisite for any such EOR applications. The transport of the particles is limited by the degree to which the particles are retained by the porous medium. In this work, experiments that quantify the retention and provide insight into the mechanisms for nanoparticle retention in porous media are described. Sedimentary rock samples (Boise sandstone and Texas Cream limestone) were crushed into single grains and sieved into narrow grain size fractions. In some cases, clay (kaolinite or illite) was added to the Boise sandstone samples. These grain samples were packed into long (1 ft – 15 ft) slim tubes (ID = 0.93 cm) to create unconsolidated sandpack columns. The columns were injected with aqueous dispersions of silica-cored nanoparticle (with and without surface coating) and flushed with brine. The nanoparticle effluent concentration history was measured and the nanoparticle recovery was calculated as a percentage of the injected nanoparticle dispersion. Fifty experiments were performed in this fashion, varying different experimental parameters while maintaining others constant to allow direct comparisons between experiments. The parameters analyzed in this thesis are: specific surface area of the porous medium, lithology, brine salinity, interstitial velocity, residence time, column length, and temperature. Our results indicate that retention is not severe, with an 8% average of the injected amount, for all our experiments. From the parameters analyzed, specific surface area was the most influential variable, with a linear effect on nanoparticle retention independently of lithology. Salinity increased nanoparticle retention slightly and delayed nanoparticle arrival. Velocity, residence time and length are coupled parameters and were studied jointly; they had a minor effect on retention. Temperature had a marginal effect, as we observed an approximate 2% increase in retention at 80°C compared to 21°C. Both surface coated and bare silica nanoparticles were successfully transported, so surface coating does not appear to be a prerequisite for transport for the particle and rock systems studied. / text

Polymers play a key role in several EOR processes such as polymer flooding, surfactant-polymer flooding and alkaline-surfactant-polymer flooding due to their critical importance of mobility control in achieving high oil recovery from these processes. Numerical simulators are used to predict the performance of all of these processes and in particular the injection rate of the chemical solutions containing polymer; since the economics is very sensitive to the injection rates. Injection rates are governed by the injection viscosity, thus, it is very important to model the polymer viscosity accurately. For the predictions to be accurate, not only the viscosity model must be accurate, but also the calculation of equivalent shear rate in each gridblock must be accurate because the non-Newtonian viscosity models depend on this shear rate. As the size of the gridblock increases, the calculation of this velocity becomes less numerically accurate, especially close to wells. This research presents improvements in polymer viscosity model. Using the improvements in shear thinning model, the laboratory polymer rheology data was better matched. For the first time, polymer viscosity was modeled for complete range of velocity using the Unified Viscosity Model for published laboratory data. New models were developed for relaxation time, time constant and high shear viscosity during that match. These models were then used to match currently available HPAM polymer's laboratory data and predict its viscosity for various concentrations for full flow velocity range. This research presents the need for injectivity correction when large grid sizes are used. Use of large grid sizes to simulate large reservoir due to computation constraints induces errors in shear rate calculations near the wellbore and underestimate polymer solution viscosity. Underestimated polymer solution viscosities lead to incorrect injectivity calculation. In some cases, depending on the well grid block size, this difference between a fine scale and a coarse simulation could be as much as 100%. This study focuses on minimizing those errors. This methodology although needs some more work, but can be used in accurate predictions of reservoir simulation studies of chemical enhanced oil recovery processes involving polymers. / text

Foam-assisted low interfacial tension and foam-improved sweep efficiency are attractive enhanced oil recovery (EOR) methods with numerous studies and researches have been conducted in the past few decades. For example, CO₂-Enhanced Oil Recovery (CO₂-EOR) is very efficient in terms of oil displacement. However, due to the low viscosity of super critical CO₂, the process usually suffers from poor sweep efficiency. One method of increasing sweep efficiency in CO₂-EOR has been identified through the use of surfactants to create "foams" or more correctly CO₂-in-water (C/W) macroemulsions. Polymer flooding techniques such as Alkali -- Polymer (AP), Surfactant -- Polymer (SP), and Alkali -- Surfactant -- Polymer (ASP) have been the only proven chemical EOR method in sandstone reservoirs with many successful pilot tests and field projects. However, the use of polymer is limited in carbonates due to unfavorable conditions related to natural characteristics of this type of lithology. In this case, foam-assisted EOR, specifically Alkali -- Surfactant -- Gas (ASG) process, can be an alternative for polymer flooding. It is a fact that large amount of the world's oil reserves resides in carbonate reservoirs. Therefore, an increase in oil recovery from carbonates would help meet the world's increasing energy demand. This study consists of two parts: (1) the development of new surfactant for creating CO₂ -- in -- water macroemulsions for improving sweep efficiency in CO₂ -- EOR processes; (2) systematic study of ASG method as a novel EOR technique and an alternative for polymer flooding in carbonate reservoirs. Both studies are related to the use of foam as a mobility control agent. In the first part, the design and synthesis of twin tailed surfactants for use at the CO₂/water interface is discussed. The hydrohobes for these surfactants are synthesized from epichlorohydrin and an excess alcohol. Subsequent ethoxylation of the resulting symmetrical dialkyl glycerin yields the water soluble dual tailed surfactants. The general characteristics of these surfactants in water are described. A comparison is carried out between twin-tailed dioctylglycerine surfactants and linear secondary alcohol surfactant based on results from a core flood. The results show that even above the cloud point of the surfactants, the twin tailed surfactants create a significant mobility reduction, likely due to favorable partitioning into the CO₂ phase. The data covers surfactant structures designed specifically for the CO₂-water interface and can be used by producers and service companies in designing new CO₂-floods, especially in areas that might not have been considered due to problems with reservoir heterogeneity. Second part contains a systematic study of ASG process on carbonate rocks through a series of experiments. The purpose is to demonstrate the performance as well as the potential of ASG as a new EOR technique. In this study, basic concepts in chemical EOR are presented, while the design of chemical formulation, phase behavior, and the role of foam are discussed in details. Experimental results showed relatively good recovery, low surfactant retention. However, pressure drop during chemical injections were high, which indicates the formation of both strong foam and viscous microemulsion at the displacement front when surfactant starts solubilizing oil. Overall, ASG showed good performance on carbonate rocks. Optimization can be made on surfactant formula to form less viscous microemulsion and therefore improve efficiency of the process. / text

This report discusses the use of micro-fabrication techniques for creating experimental test sections containing trees of micro-finned conducting pathways, also referred to as constructal trees, for cooling a heat generating substrate. These trees are made of copper and contain branches that bifurcate at 90° angles to form constructal patterns. The patterns for the finalized test sections were created using photolithography techniques, and copper was deposited via thermal evaporation onto a 1 cm² substrate to create the trees. Certain test section design parameters were varied including the geometric complexity of the constructal trees, the volume of copper used between tree complexities, choice of material for the substrate, and the height, or thickness, of the trees. Also described in this report is an experimental methodology and testing apparatus designed to assess the cooling performance of the test sections. This methodology includes using controlled uniform heating applied to the bottom of each test section, while cooled nitrogen is impinged on the tip of the constructal tree to create a heat sink. / text