Materials Science and Engineering Commons^™

Optimization Of The Front End Of Cdte Solar Cells, Yunfei Chen

Dissertations

The front end of CdTe solar cells consists of two layers: a transparent conducting oxide (TCO) layer and a window layer. New wider band gap materials, ZnMgO are being used to replace CdS as the window layer for the purpose of removing blue loss. For ZnMgO, three important parameters, including the atomic Mg content (x), thickness (t), and doping concentration (n) can play important roles on the performance of CdTe solar cells. In this dissertation, systematic simulation, by solar cell capacitance simulator (SCAPS), and experiments are used to investigate the influences of these …

Numerical Simulation For Identification Of Insects Using A Cw Lidar System, Christo Videlov

Theses

Mosquitos are the most common vector of disease in the world, causing millions of deaths a year. While curing the diseases they cause is one approach to this problem, another could be to avoid the mosquitos in the first place. Knowing their flight patterns, location, and population in one area could aid in this. Additionally, classifying the mosquitos in an area would be helpful. The age and sex of the mosquito is important to find as they affect the chances of the insect carrying diseases such as malaria or yellow fever.

Many current methodologies to monitor insects are based on …

Corrosion Studies Of Stainless Steel Blades, Dhruv S. Kothari

Theses

Corrosion is a subject of interest to interdisciplinary research communities that includes fields of materials science, chemistry, physics, metallurgy and chemical engineering. In order to understand the mechanisms of corrosion and the function of corrosion inhibitors, the reactions at the interfaces between the corrosive electrolyte and a steel surface, particularly at the initial stages of the corrosion process, need to be described. Naturally, these reactions are strongly affected by the nature and properties of the steel surfaces. It is however seen that the majority of recent corrosion and corrosion-inhibition investigations are limited to electrochemical testing, with ex situ analysis of …

Smart Polymeric Temperature Sensors – For Biological Systems, Greenee Anilkumar Sinha

Theses

The damaged brain is vulnerable to increase in brain temperature after a severe head injury. Continuous monitoring of intracranial temperature depicts functionality essential to the treatment of brain injury Many innovations have been made in the biomedical industry relying on electronic implants in treating condition such as traumatic brain injury (TBI) or other cerebral diseases. Hence, a methodical and reliable way to measure the temperature is crucial to assess the patient’s situation. In this investigation, an analysis of various approaches to detect the change in the temperature due to resistance, current-voltage characteristics with respect to time has been evaluated. Also, …

Memorizing Chromic Response To Pressure, Maulik Kiritkumar Padh

Theses

Almost all appliances are prone to mechanical stress in one form or the other. An increasing dependence on machines in daily life calls for a need to increase their maintenance quality. Various materials, methods and configurations to observe mechanical pressure have been devised and this paper discusses one such technique. The use of gold nanoparticles in its one dimensional array causes plasmonic coupling between the nanoparticles, which when disrupted creates a plasmonic shift in its assembly. Such a film, when casted on a polymer with a known elastic limit, causes deformation by an application of stress. This forces the film …

Development Of Low Alloy Steel By Direct Metal Laser Sintering, Elias Jelis

Dissertations

The US Department of Defense is interested in developing, understanding, and optimizing process parameters for low alloy (4340/4140 steel) for the powder bed fusion process. Low alloy steel is used in parts where high strength and toughness are required. During parameter optimization, several aspects of the process are investigated. Powder size and morphology optimization is important for manufacturability because adequate packing is required to produce full density components. Microstructure evaluation is used in order to provide insight into parameters that lead to optimal mechanical performance and recoating performance. Influence of residual stress is evaluated with this process. Large thermal stress …

Electrical, Electronic And Optical Properties Of Mose2 And Wse2, Sushant Shashikant Rassay

Theses

Transition-metal dichalcogenides (TMDC) crystals have emerged as a new class of semiconductors that display distinctive properties at monolayer thickness. Their electrical, electronic and optical properties are of particular interest and importance for applications in optoelectronics as light emitters, detectors, and photovoltaic devices. Monolayer MoSe₂ and WSe₂ have an intrinsic band-gap in the visible region of the solar spectrum (400nm - 700nm) which makes them distinct from other 2-D materials like graphene.

In this study, the electrical, electronic and optical properties of monolayer and bulk MoSe₂ and WSe₂ are studied. The electronic band structures are presented for …

Heat Transfer In Silicon - Experiments And Simulation, Chihlin Huang

Theses

The purpose of this thesis is to study the heat transfer in silicon. Silicon is the key semiconductor material, and thermal processing is the traditional method that is used in semiconductor processing. In this research, we can predict the temperature of the silicon wafer during heating. This ability to predict wafer temperature during semiconductor processing will facilitate in the following: (a) Process temperature uniformity, (b) Film thickness uniformity, (c) Diffusion, (d) Process yield, (e) Thermally induced stresses, and (f) Device yield - spatially and temporally across the wafer. For low temperature applications, IC chips can be modeled to simulate the …

Electrical, Electronic And Optical Properties Of Mos2 & Ws2, Weitao Tang

Theses

Two dimensional materials such as graphene, boron nitride and transition metal dichalcogenide (TMDCs) monolayers have arisen as a new class of materials with unique properties at monolayer thickness. Their electrical, electronic and optical properties are of great importance for a variety of applications in optoelectronics as light emitters, detectors, and photovoltaic devices. This work focuses on MoS₂ and WS₂, which are two important members of the TMDC class of materials. The properties of monolayer MoS₂ and WS₂ are investigated as well as the properties of bulk MoS₂ and WS₂ to provide an understanding …

Application Of Inkjet Printing Technology To Flexible Batteries, Yuan Gu

Dissertations

Printing technologies have been considered as alternative methods to fabricate thin films in recent years. More and more functional devices like resistors, sensors, antennas and even energy storage devices have been fabricated by printing technologies. As a typical digital printing technology, inkjet printing has much more advantages over the traditional mechanical printing technologies such as: low cost, computer controllable shape design and precise deposition. In this investigation, application of inkjet printing is used to fabricate conductive tracks and rechargeable lithium ion batteries.

Particle free silver ink is developed to solve this problem. In this research, silver complex solution is printed …

Magnetic Augmented Rotation System (Mars ) - Properties And Performance, Ruolei Liu

Theses

Magnetic Augmented Rotation System (MARS) is proposed as a system for conversion of mechanical energy into electrical energy. It works on the principle of magnetic coupling. Because it is contactless, compared with traditional gears, it increases the transfer efficiency from a driver to a rotor; reduces noise, requires no lubrication and has low maintenance cost. In order to assess the performance of MARS, a charging system based on MARS is implemented. This system includes rechargeable batteries in the range of 6 volts to 12 volts, a load in the form of a light bulb, a voltage transformer, and digital multimeter …

A Computational Model For Transdermal Diffusion Of Lidocaine And Tetracaine Topical Patches, Qian Dong

Theses

In recent years, transdermal drug delivery patches (TDDP) have developed rapidly. This is because the TDD system has more advantages than traditional drug delivery systems such as oral medicine and intravenous injection. In order to reach the circulatory system of the human body, drug molecules have to pass through the epidermis (outer layer) of the skin. The barrier properties of epidermis originate from low permeability of stratum corneum (SC) which is the outermost layer of the human skin. The objective of this thesis is to build a Finite Element (FE) model, utilizing commercial FE software (ANSYS), that can be implemented …

Koh Etching Of Silicon, Ying Wang

Theses

In this research, a series of comparative etching experiments on silicon wafers have been carried out using potassium hydroxide (KOH) for different experimental etching conditions for concentration, temperature and time on (100) orientation p-type silicon wafers. Besides the basic etching conditions, the position of the immersed wafer also has unpredictable effect on the etching process. This may be attributed to the relative contact position between the surface of the immersed wafer and the flow patterns of the stirred etching solution.

The surface morphology analysis indicates that the specific position of the wafer, with respect to the flow of the etchant, …

Infrared Imaging - Case Studies And Applications, Shuang Du

Theses

Recent advancements in the manufacture of solid state detectors have led to significant improvements in the use and applications of infrared (IR) imaging. Compared with traditional imaging in visible light, infrared imaging has abilities to convey significant additional information. Applications in medicine require wavelengths in the range of 0.8 to 25 microns while metrology and astronomy, traditionally, require wavelengths in the range of 25 microns to 1 mm.

In this study, infrared imaging has been used as a tool to characterize a variety of objects and systems. Some of these case studies have been considered under conditions of thermodynamic non-equilibrium. …

Diffusivity Of Drug Actives In Transdermal Drug Delivery (Tdd), Natali R. Gendelberg

Theses

Transdermal Drug Delivery (TDD) through skin patches has many advantages including the following: slow and continuous administration of the therapeutic over long periods of time, timely dosage, accessibility, kinetic maneuverability, elimination of the “First Pass Effect” and negative side effects on the digestive tract. All of the above justify investment into further development of TDD therapies, despite the skin permeability restrictions posed on size and charge by the skin. As skin permeability varies between all individuals based on age, ethnicity and lifestyle, the determination of the proper drug dosages to be contained in the skin patch is highly reliant on …

Understanding Bulk Behavior Of Particulate Materials From Particle Scale Simulations, Xiaoliang Deng

Dissertations

Particulate materials play an increasingly significant role in various industries, such as pharmaceutical manufacturing, food, mining, and civil engineering. The objective of this research is to better understand bulk behaviors of particulate materials from particle scale simulations.

Packing properties of assembly of particles are investigated first, focusing on the effects of particle size, surface energy, and aspect ratio on the coordination number, porosity, and packing structures. The simulation results show that particle sizes, surface energy, and aspect ratio all influence the porosity of packing to various degrees. The heterogeneous force networks within particle assembly under external compressive loading are investigated …

Experimental And Theoretical Evaluation Of In-Depth Damage Distribution In Sawn Silicon Wafers, Srinivasamurthy Devayajanam

Dissertations

As-sawn silicon wafers have surface damage that needs to be removed before any further processing into solar cells. This damage distribution can vary with cutting parameters such as wire size, slurry particle/diamond grit size, and wire usage. To date, there is no simple way to measure the degree of damage, damage depth, and damage distribution. But, this information is needed by the wafer manufacturers as well as solar cell manufacturers.

A technique based on sequential etching of silicon wafers and minority carrier lifetime (τ_eff) measurements is used to determine damage depth. In this technique, samples are sequentially etched …

Thermoelectric Properties Of Silicon-Germanium Alloys, Aniket Annasaheb Maske

Theses

Direct energy conversion from thermal to electrical energy, based on thermoelectric effects, is attractive for potential applications in waste heat recovery and environmentally friendly refrigeration. The energy conversion efficiency of thermoelectric devices is related to the thermoelectric figure of merit ZT, which is proportional to the electrical conductivity, the square of the Seebeck coefficient, and the inverse of the thermal conductivity. Currently, the low ZT values of available materials restrict the large scale applications of this technology. Recently, however, significant enhancements in ZT have been reported in nanostructured materials such as super-lattices mainly due to their low thermal conductivities. According …

Production And Characterization Of Composite Nano/Micro Sized Particles By Rapid Expansion Of Supercritical Solutions (Ress) Co-Precipitation, Beidi He

Dissertations

Nanoscale composites of hexahydro-1, 3, 5-trinitro-1, 3, 5-triazine (RDX) and polymer binders were produced by co-precipitation using rapid expansion of supercritical solutions (RESS). The binders used in this study are poly (vinylidene fluoride-co-hexafluoropropylene) (VDF-HFP22), polystyrene (PS) and 7-amino-4-methyl coumarin (AMC). The RDX/VDF-HFP22 and RDX/PS co-precipitated nanoparticles were characterized by Field Emission Scanning Electron Microscopy (FE-SEM) and Transmission Electron Microscopy (TEM). The average size of produced nanoparticles is ca. 100 nm. TEM analysis of RDX/PS nano-composite shows a core-shell structure with RDX as the core material and the shell consisting of the polymeric binder. X-ray Powder Diffraction (XRPD) analysis …

New Screening Methodology For Selection Of Polymeric Materials For Transdermal Drug Delivery Devices, Roberto P. Falcone

Dissertations

As medical advances extend the human lifespan, the level of chronic illnesses will increase and thus straining the needs of the health care system that, as a result, governments will need to balance expenses without upsetting national budgets.

Therefore, the selection of a precise and affordable drug delivery technology is seen as the most practical solution for governments, health care professionals, and consumers.

Transdermal drug delivery patches (TDDP) are one of the best economical technologies that are favored by pharmaceutical companies and physicians alike because it offers fewer complications when compared to other delivery technologies. TDDP provides increased efficiency, safety …

Computational Studies Of Electronic Structure Of Doped Graphene, Yan Chu

Theses

In the literature, extensive studies have been performed to study the electronic properties of doped graphene. This is due to the potentially large number of applications of graphene in p-n junctions, transistors, photodiodes and lasers. By utilizing single heteroatom chemical doping method or electric field-induced method, one can introduce a band gap, ranging from 0.1eV to 0.5eV, in graphene. A tunable bandgap is highly desirable because it would allow significant flexibility in the design and optimization of such devices, particularly if it could be tuned by adjusting the doping configurations. Here, we demonstrate the realization of a widely tunable electronic …

Modeling Of Electrical Behavior Of Graphene-Based Ultracapacitors, Patrick Dzisah

Theses

Graphene has been identified as a promising material for energy storage, especially for high performance ultracapacitors. Graphene-based ultracapacitors show high stability, significantly-improved capacitance and energy density with fast charging and discharging time at a high current density, due to enhanced ionic electrolyte accessibility in deeper regions. The surface area of a single graphene sheet is 2630 m2/g, substantially higher than values derived from Brunauer Emmett Teller (BET) surface area measurements of activated carbons used in the current electrochemical double layer capacitors.

In an ultracapacitor cell, chemically modified graphene (CMG) materials demonstrate high specific capacitances of 135 and 99 F/g in …

Simulation Of Electronic And Optical Properties Of Graphene, Biao Leng

Theses

Graphene is a recently discovered two-dimensional crystal. Due to its excellent electronic properties, transport properties, optical properties, and many other features, it has tremendous potential for applications in many areas. This thesis discusses the structure and properties of graphene using several different models of graphene and carries out detailed theoretical studies and calculations of its electronic and optical properties. Using two modules of Materials Studio, CASTAP and Doml3, four graphene models have been constructed. Their electronic and optical properties have also been calculated via these two modules. By comparing the results of calculations with experimental results and the literature, the …

Processing And Characterization Of Graphene And Graphene On Silicon, Cheng Peng

Theses

Graphene has become a promising material for applications in many areas including electronic devices, batteries and space crafts. Although it has a bright future, the commercial production of graphene has not yet been realized. In this thesis, an overview of the properties and applications of graphene is presented. The early research of preparing graphene and its composites is summarized, which gives the basis to synthesize graphene and improve the process. In this study, graphene oxide (GO) and graphene have been successfully made using graphite; graphene layer has been coated on the surface of a silicon wafer. The resulting specimens are …

Optical Properties Of Black Silicon - An Analysis, Suramya Sekhri

Theses

Silicon is the preeminent solar cell material of the day because it is the first semiconductor that was learned to commercialize and continues to be the principal semiconducting material used in photovoltaic technology for the manufacture of solar cells. Silicon, an indirect band gap semiconducting material, has a reflectance of about 30% in the visible range of wavelengths. Standard Silicon solar cells are not entirely useful in the infrared spectrum region. In order to enhance the performance of Silicon solar cells, reflectance losses must be minimized and absorption must be maximized. In the solar cell industry, anti-reflection (AR) coating is …

Ultracapacitors For Off Grid Wind Power Systems, Hans Tanis

Theses

The main reason for wind turbine to be not as prevalent as traditional power systems is because they do not have an effective storage capacity. However, researchers in material science and engineering have found ways to resolve this problem by developing “ultracapacitors” that store energy by assembling ions at the surface of a porous material. That is why ultracapacitors coupled with the energy storage battery could present a challenge to the electrical power grid. Such a design allows ultracapacitors to charge in matter of minutes and not hours. This innovation would create a significant impact on electronic items such as …

Bio-Medicinal Application For Plasma Electrolytic Oxidation Of Metals, Zunjian Yang

Theses

Plasma electrolytic oxidation (PEO), a novel method for forming ceramic coatings on metals, has been researched extensively in recent times. By applying high voltage between dielectric thin films, a plasma micro-arc is induced through penetration of breakdown in film boiling layer. Such a method takes advantage of high processing time, low equipment requirement and advanced coating performance.

Titanium alloys, Ti-6Al-4V and pure Titanium Grade 2, are two of most common Titanium alloys in daily use. Both of such Titanium alloys show great potential utilization in bio-medicinal application, especially in implants, for its excellent biocompatibility, high tensile strength, and high elastic …

Design, Construction And Characterization Ofa Magnetic Augmented Rotation System (Mars) Based Wind Turbine, Da Li

Theses

Magnetic Augmented Rotation System (MARS) works by magnetic field coupling, to transfer torque from the driver to the rotor without contact. This characteristic has significant applications to the wind turbine but research in combination of MARS and wind turbine has not been done in the literature. In this thesis, a small-scale wind turbine is designed, built and characterized in a prototype wind tunnel. The test results are analyzed and computer-aided software simulation is used as an auxiliary method to understand the mechanism of MARS. The power coefficient of this new wind turbine is estimated to be about 40%. The “gear …

Design, Construction And Characterization Of A Wind Tunnel, Chang Ge

Theses

The wind tunnel is the most fundamental test equipment for aircraft testing and studying aerodynamics. Because of the complexity of the test-subject's geometry, it is difficult to study the aerodynamic pattern simply based on theoretical calculations. Most of the aerodynamics experiments still use wind tunnels. The progress of the wind tunnel is highly related to the advancements in air crafts. Aircraft manufacturing has pushed the wind tunnel technology forward. Wind tunnels can be categorized by the wind speed limit differences, which are controlled by the mechanism of the driving methods, structure applications, etc. In this case, we built a small …

An Extended Duration Operation For Solid Hollow Fiber Cooling Crystallization Method, Chi Jin

Theses

As recently demonstrated by Chen et al. [1], the solid hollow fiber cooling crystallization method to achieve continuous polymer coating/encapsulation of submicrometer particles, has advantages of no problem with high pressure, easy scale-up and production of free-flowing coated particles. There is a concern whether this crystallization method can be applied for an extended duration coating process; it was not investigated in the previous study. Therefore, in order to examine this problem, in this work, the duration of the whole crystallization coating process has been greatly extended from 5 min to 60 min and 120 min. For the purpose of being …