The purpose of this study was to evaluate the treatment efficiency of phenol contaminated soils by electrokinetic (EK) process conducted in sand boxes (60 cm¡Ñ30 cm¡Ñ30 cm; L¡ÑW¡ÑH). The electric field strength, electrode polarity reverse, and Fenton reagent were employed as the experimental factors in this study to assess the variations of soil characteristics, potential difference, and residual phenol concentration distribution during a treatment period of 20 days and after the treatment. It was found that the anode reservoir pH decreased to around 2 and the cathode reservoir pH increased to approximately 12 after 2~3 days of treatment in the no electrode polarity reverse system. However, the variation of pH in the anode and cathode reservoirs was less obvious in the case with electrode polarity reverse. No matter a constant potential system or a constant current system was employed, a general trend of a lower pH at the anode reservoir and a higher pH at the cathode reservoir would be found. The acid front generated at the anode reservoir flushed across the soil specimen toward the cathode and the base front advanced toward the anode. However, in the central region of sand box, unsaturated and saturated soil specimen maintain neutral. For EK or EK-Fenton experiments, under the constant potential conditions, the potential difference relative to the cathode versus the distance from anode was found to have a linear relationship at the beginning of the electrical potential application. As the treatment time elapsed, the potential gradient became non-linear. Nevertheless, there was no remarked potential gradient change in the case with electrode polarity reverse. Although capillarity has resulted in an increase of the moisture content of unsaturated soil (from 25.34% to 30% after 20 days), electroosmotic (EO) flow was not obvious in the unsaturated zone. For the experiments with electrode polarity reverse, they had a much greater EO flow quantity, the electroosmotic permeability coefficients for constant potential and constant current systems were 6.42¡Ñ10-6 cm2/V¡Es and 9.47¡Ñ10-6 cm2/V¡Es, respectively. It was also found that the existence of contaminants did reduce the EO flow quantity. Regardless of the employment of a constant potential or constant current system, the maximum destruction and removal efficiency (DRE) of phenol was obtained for EK-Fenton process. The maximum DRE values of phenol for both constant potential and constant current systems were found to be 78.06% and 80.11%, respectively. However, the DRE of phenol was found to be much lower for the system with electrode polarity reverse. It was postulated that the destruction efficiency of phenol was less obvious than the removal efficiency in the electrode polarity reverse system. In addition, a frequent reverse of electrode polarity also resulted in a frequent change of EO flow direction. Thus, a flow hysteresis of phenol in the soil compartment was found.

A mathematical model for a proton exchange membrane fuel cell is the focus of this thesis. Modeling and simulations are carried out with an aim to understand the influence of operational and geometrical parameters on the inner reaction and performance of a proton exchange membrane fuel cell, and discuss the distributions of physical phenomena in membrane and catalyst layer. Than, the results of modeling are compared and analyzed with the experiments, and discuss the reasons of influences of the performance of PEMFC. The results show that activation overpotential is the major reason of influence of the performance at low current density (less than ), and diffusion and ohmic overpotential are substantially increased at high current density (great than ). The membrane of higher membrane conductivity and more thin, increasing pressure of cathode gas and use oxygen can enhance the performance of a PEMFC. The performance almost no influence for the catalyst layer over 0.3£gm. The catalyst layer thin and uniform can decrease coating of this layer. The results of modeling and experiments show that experiments have contact resistance between materials, and the performance slightly lower than performance of modeling, and the differences that at high current density great than low current density.

Carbon-based materials are currently used for anodes in commercial lithium ion secondary batteries. The theoretical capacity for carbon is only 372mAh/g, and new materials are being developed for anodes to raise the electrical capacity and cycling times. One of the most promising materials is tin oxide that has 50% more electrical capacity and has been studied extensively in the industrial and academic institutions. While most studies have been concentrated on the electrochemical behavior in the charge-discharge process, microstructure evolution along with phase transformation have been emphasized in this work. Tin oxide films are deposited on stainless steel substrate by sputtering and spray. A cell consists of a pure lithium foil as anode and tin oxide film as cathode along with 1M LiClO4 in DMC/EC mixture as electrolyte is fabricated and employed in the charge-discharge test and Cyclic Voltammetry. In the charge-discharge test, we use a constant current of 0.09mA to charge or discharge to the voltage that we need. In the Cyclic Voltammetry test, we change the scanning rate and scanning range. Microstructures developed and phase transformation in different stages of the charge-discharge or CV test process are examined by XRD, SEM and TEM.

Molecular light emitting diode, including organic light emitting diode (OLED) and polymer light emitting diode (PLED), is commonly consist of one or several molecular layer(s) sandwiched between an anode and a cathode. When electrons and holes are injected respectively from cathode and anode into the molecular layer by a bias voltage, these two types of carriers migrate towards each other and a fraction of them recombine to form light emission. The focus of this study is electrode modifications of molecular light emitting diode. The electrode modifications include using a low work function cathode material, a high work function anode material or inserting a very thin electrode modifier between molecular layer and electrode for enhancing the electron or the hole injection efficiency leading to higher electroluminescence emission and/or lower threshold voltage. Low work function metal, Mg, could effectively reduce the electron injection barrier between molecular layer and cathode leading to better emission brightness and threshold voltage. A monolayer rigid-rod poly-p-phenylenebenzobisthiazole (PBT) or poly-p-phenylenebenzobis- oxazole (PBO) PLED with Mg cathode demonstrated a low threshold voltage of 3 V. Besides, a very thin layer of LiF (or Al2O3) inserted between molecular layer and Al cathode was applied to enhance the electron injection efficiency leading to a stronger electroluminescence intensity and a low threshold voltage of 2.8 V. On anode modification, a thin PBO layer was inserted between molecular layer and the indium-tin-oxide (ITO) substrate for improving the electroluminescence emission brightness and the threshold voltage. The PBO modified anode could effectively enhance the electro- luminescence intensity and lower the threshold voltage to 1 V~ 3 V on several mono- or multi-layer molecular light emitting diodes. Besides, a novel ITO substrate cleaning method via acid treatment was applied for increasing the work function of ITO to effectively enhance the hole injection efficiency.

A novel high-k gate dielectric material, i.e., hafnium-doped tantalum oxide (Hf-doped TaOx), has been studied for the application of the future generation metal-oxidesemiconductor field effect transistor (MOSFET). The film's electrical, chemical, and structural properties were investigated experimentally. The incorporation of Hf into TaOx impacted the electrical properties. The doping process improved the effective dielectric constant, reduced the fixed charge density, and increased the dielectric strength. The leakage current density also decreased with the Hf doping concentration. MOS capacitors with sub-2.0 nm equivalent oxide thickness (EOT) have been achieved with the lightly Hf-doped TaOx. The low leakage currents and high dielectric constants of the doped films were explained by their compositions and bond structures. The Hf-doped TaOx film is a potential high-k gate dielectric for future MOS transistors. A 5 àtantalum nitride (TaNx) interface layer has been inserted between the Hf-doped TaOx films and the Si substrate to engineer the high-k/Si interface layer formation and properties. The electrical characterization result shows that the insertion of a 5 àTaNx between the doped TaOx films and the Si substrate decreased the film's leakage current density and improved the effective dielectric constant (keffective) value. The improvement of these dielectric properties can be attributed to the formation of the TaOxNy interfacial layer after high temperature O2 annealing. The main drawback of the TaNx interface layer is the high interface density of states and hysteresis, which needs to be decreased. Advanced metal nitride gate electrodes, e.g., tantalum nitride, molybdenum nitride, and tungsten nitride, were investigated as the gate electrodes for atomic layer deposition (ALD) HfO2 high-k dielectric material. Their physical and electrical properties were affected by the post metallization annealing (PMA) treatment conditions. Work functions of these three gate electrodes are suitable for NMOS applications after 800°C PMA. Metal nitrides can be used as the gate electrode materials for the HfO2 high-k film. The novel high-k gate stack structures studied in this study are promising candidates to replace the traditional poly-Si-SiO2 gate stack structure for the future CMOS technology node.

Membrane electrode assembly (MEA) is the foundation of the single cell as well as the core of the fuel cell when generating electricity. Its work efficiency is the key factor for single cell performance. This study aims to understand the variation between the conventional method and the decal method during the MEA process. By observing the microstructure morphology of electrode and the performance of single cell, as well as analyzing internal resistance and its stabilization, the advantages and disadvantages of MEA in the two methods is analyzed. The decal condition is 135¢XC, 15 kg/cm , 2.5 min at a high temperature (50¢XC 3M methanol), in air-breathing under atmosphere system. The maximum power density is approximately 22.5 mW/cm which is very close to the result of conventional method. The decal method is better than the conventional method particularly in regards to the high current density performance. It shows that there is an efficient influence of the decal method on the methanol mass transfer and it also improves its polarization and enlarges the current. If the single cell is operated in the high temperature, the fuel mass transfer can be advanced in the decal method and its performance can be raised. However, in the manufacturing process, more time has to be spent when producing the MEA. This experiment can be used as a reference on the single cell operation environment and manufacturing time for future studies.

The conventional medical immunoassays (ELISA/CLIA/FPIA) are not only costly (>10,000 USD), large in size (>10,000 cm3), but also require a vast number of sampling (25 £gL/well ¡Ñ 12 well) and long detection time (1~2.5 hr). To develop a biomedical microsensor for the application of portable detecting microsystem, this thesis proposes a flexural plate wave (FPW) microsensor with a novel reflection grating electrode (RGE) microstructure. Comparing to the conventional acoustic microsensors, the FPW based device has higher mass sensitivity, lower operation frequency but higher noise level. To overcome this disadvantages, this study added the RGE microstructure into the design of FPW sensor and investigated its influences on the reduction of insertion loss and noise level. By using the surface and bulk micromachining technologies, this thesis designed and fabricated FPW-based mass-sensing device with a small volume of 0.189 cm3 and a novel RGE microstructure. The main processing steps adopted in this research include six photolithoghaphies and nine thin-film depositions. In this work, a high figure-of-merit C-axial orientation ZnO piezoelectric thin-film was deposited by a commercial magnetic radio-frequency (RF) sputter system. On the other hand, the gold/chrome interdigital transducer (IDT) and RGE aluminum electrode were deposited utilizing a commercial E-beam evaporator system. For the optimization of design specifications of the FPW devices, the space of input and output IDTs, pair number of IDT, length of delay line gap and with/without RGE design were varied and investigated. Under the optimized IDT specification, the FPW microstructure presents lower central frequency (2¡ã4 MHz), insertion loss (-11 dB) and noise level (<-30 dB) than that of the FPW based microsensor without RGE microstructure. In addition, as the sampling volume of the testing DI water is equal to 1 £gL, a high mass sensitivity (-48.3 cm2/g) and short responding time (5 min) of the FPW microsensor with RGE design can be achieved in this work. The excellent characteristics mentioned above demonstrated the implemented FPW microsensor is very suitable for the applications of portable biomedical detecting microsystems.

The continuous trend towards mega-functional, high-performance and ultra-miniaturized system has been driving the need for advances in novel materials with superior properties leading to thin components, high-density interconnect substrates and interconnections. Power supply and management is becoming a critical bottleneck for the advances in such mega-functional systems because power components do not scale down with the rest of the system resulting in bulky and stand-alone power modules. Amongst the power components, thin film capacitors are considered the most challenging to integrate because of several manufacturability concerns. The challenges are related to process compatibility of high permittivity dielectrics with substrates and high surface area electrodes, yield, leakage and losses. This thesis focuses on novel thin film capacitor technologies that address some of these critical challenges. / Thesis advisor has approved the addition of errata to this item. The abstract text in the metadata record has been modified to match the document text.

A distinctive field in the coatings industry is the coating of porous media, with broad applications in paper, apparel, textile, electronics, bioengineering, filtration and energy sector. A primary industrial scale process that can be used to coat porous media in a fast and flexible manner is slot die extrusion. A major concern when coating porous media with a wetting fluid is fluid penetration into the substrate. Although some level of penetration is desirable to obtain specific material properties, inadequate or excessive fluid penetration can negatively affect the strength, functionality or performance of the resulting material. In spite of its apparent industrial importance, limited modeling and experimental work has been conducted to study fluid penetration into porous media during fabrication. The effects of processing parameters on the penetration depth, the effects of penetration on material quality, and the method to predict and control the penetration depth are not well understood. This dissertation is composed of two parts. Part I is an applied study for coating onto porous media. This part focuses on the first objective of this dissertation which is to elucidate clearly the feasibility, advantages and disadvantages of the direct coating method as a potential fabrication route for membrane electrode assembly (MEA). MEA samples are fabricated using both traditional and the direct coating methods. Then, the quality and performance of the MEA samples are examined. Experimental results in Part I demonstrate that it is feasible to fabricate MEAs using the direct coating method. However, Nafion® solution penetrates into the catalyst layer during the coating process and causes lower performance of fuel cells, which is the motivation for Part II of this thesis. The objective of Part II is to fundamentally understand the fluid penetration process and predict the penetration depth when directly coating porous media, using a comprehensive approach. A series of computational and analytical models are developed to predict the penetration depth for both Newtonian and non-Newtonian fluids with or without capillary pressure. Finally the accuracy of developed models are validated through experiments. The relative error between the predicted and experimentally measured penetration depth is generally lower than 20%.

The rising energy consumption worldwide is leading to significant increases in energy production with fossil fuels being the major energy source. The negative environmental impact of fossil fuel use and its finite nature requires the use of alternative sources of energy. Solar energy is a clean alternative energy source; however, its intermittent nature is a major impediment that needs to be reduced or eliminated by the development of cost effective energy storage. Thermal storage in tanks filled typically with molten salt at elevated temperatures is widely used in concentrating solar power plants to generate electricity during periods of low daytime solar radiation or night time. Similarly, electrical storage in batteries, etc. is used in conjunction with photovoltaic solar power plants. Electrochemical supercapacitors can be effectively used for electrical storage, either alone or in a hybrid configuration with batteries, for large scale energy storage as well as in electric vehicles and portable electronics. Unlike batteries’, supercapacitor electrodes can be made of materials that are either less toxic or biodegradable and can provide almost instantaneous power due to their unique charge storage mechanism similar to conventional capacitors found in most electronics. Unfortunately, the same storage mechanism prevents supercapacitors from having high energy density. The purpose of this dissertation is to investigate organic and inorganic electrode materials that can increase the specific capacitance and energy density of supercapacitors. Additionally, certain types of supercapacitor electrode materials store the charges at the electrode/electrolyte interface preventing any deformation of the material and thus increasing its cycle life by two to three orders of magnitude. Transition metal oxides, layered transition metal chalcogenides, and their composites with graphene and conducting polymers have been synthesized, characterized, and their electrochemical performances evaluated for suitability as electrode materials for supercapacitor applications. Morphology and crystalline structure characterization methods used, such as scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), and Fourier transform infrared spectroscopy (FT-IR), were used throughout this work. Electrochemical characterization involved cyclic voltammetry (CV), constant current charge and discharge (CCCD), and electrochemical impedance spectroscopy (EIS) in two and three electrode configuration using aqueous and organic electrolytes. Ruthenium oxide-graphene (RuO2-G) electrodes were tested in the two-electrode cell configuration and exhibit an areal capacitance of 187.5 mF cm-2 in 2M H2SO4 at a RuO2:G ratio of 10:1. Due to RuO2 high toxicity, scarcity, and high cost, manganese oxide-graphene (MnO-G) was used as an alternative but its low specific capacitance remains a major stumbling block. The electrodes’ mass loading was studied in detail to understand the effects of thickness on the measured specific capacitance. Layered transition metal chalcogenides are structurally similar to graphene but possess different characteristics. Molybdenum sulfide (MoS2) is a two-dimensional material that has lower conductivity than graphene but larger sheet spacing making it easy for other materials to intercalate and form composites such as molybdenum sulfide-polyaniline (MoS2-PANI). MoS2-PANI electrodes, with different thicknesses, were measure in a three-electrode cell configuration resulting in gravimetric capacitance of 203 F g-1 for the thinnest electrode and areal capacitance of 358 mF cm-2 for the thickest electrode; all measurements performed using 1M H2SO4 aqueous electrolyte. Attempts were also made to reduce the supercapacitor self-discharge by depositing on the electrode a blocking thin layer of barium strontium titanate (BST). The results were rather inconclusive because of the large thickness of the deposited BST layer. However, they strongly suggest that a very thin BST layer could improve the overall capacitance because of the very large dielectric constant of the BST material. Additional work is required to determine its effects on self-discharge.