Engineering Science and Materials Commons^™

Investigating The Rheological Behavior Of A Simple Yield Stress Fluid Under Shear Flows, Francesco Accetta

Theses

Many soft materials display unique and complex rheological behavior characterized by a transition from a solid-like to a fluid-like state upon the application of a force that exceeds the threshold to flow, known as the yield stress. Yield stress fluids are found in a wide range of commonly encountered materials including microgels, emulsions, and foams, and have been widely studied by rheologists over the last several decades. Carbopol is a popular polymeric microgel system as it displays simple, non-thixotropic rheological behavior and is typically seen as an ideal yield stress fluid. Previous research has demonstrated the reproducible behavior of shear …

Modeling Of Quad-Station Module Cluster Tools Using Petri Nets, Aung Nay

Theses

The semiconductor industry is highly competitive, and with the recent chip shortage, the throughput of wafers has become more important than ever. One of the tools that the industry has deployed is to use of quad-station modules instead of the traditional single-station modules that allow for higher throughput and better wafer consistency by processing multiple wafers at the same time and distributing work. The industry trend is to use multiple transfer chamber robots to stack the quad-station modules in a series, particularly for etch products. In this work, the quad-station cluster tool wafer movement is modeled by using Petri net …

Investigation Of Topological Phonons In Acoustic Metamaterials, Wenting Cheng

Dissertations

Topological acoustics is a recent and intense area of research. It merges the knowledge of mathematical topology, condensed matter physics, and acoustics. At the same time, it has been pointed out that quasiperiodicity can greatly enhance the periodic table of topological systems. Because quasiperiodic patterns have an intrinsic global degree of freedom, which exists in the topological space called the hull of a pattern, where the shape traced in this topological space is called the phason. The hull augments the physical space, which opens a door to the physics of the integer quantum Hall effect (IQHE) in arbitrary dimensions. In …

Optical Engineering Of Iii-Nitride Nanowire Light-Emitting Diodes And Applications, Ha Quoc Thang Bui

Dissertations

Applications of III-nitride nanowires are intensively explored in different emerging technologies including light-emitting diodes (LEDs), laser diodes, photodiodes, biosensors, and solar cells. The synthesis of the III-nitride nanowires by molecular beam epitaxy (MBE) is investigated with significant achievements. III-nitride nanowires can be grown on dissimilar substrates i.e., silicon with nearly dislocation free due to the effective strain relaxation. III-nitride nanowires, therefore, are perfectly suited for high performance light emitters for cost-effective fabrication of the advanced photonic-electronic integrated platforms. This dissertation addresses the design, fabrication, and characterization of III-nitride nanowire full-color micro-LED (µLED) on silicon substrates for µLED display technologies, high-efficient …

Intermittent Dynamics Of Dense Particulate Matter, Chao Cheng

Dissertations

Granular particle systems are scattered around the universe, and they can behave like solids when there exist strong force-bearing networks, so that the granular system can resist certain stress without deformation. When such a network is not present, particles yield to small stress and behave like a fluid. A wide range of systems exhibit intermittent dynamics as they are slowly loaded, with different dynamical regimes governing many industrial and natural phenomena. While a significant amount of research on exploring intermittent dynamics of granular systems has been carried out, not much is known about the connection between particle-scale response and the …

Investigation Of Topological Phonons In Discrete Mechanical Metamaterials, Kai Qian

Dissertations

The study of topological mechanical metamaterials is a new emerging field that focuses on the topological properties of artificial mechanical structures. Inspired by topological insulators, topological mechanism has attracted intensive attention in condensed matter physics and successfully connected the quantum mechanical descriptions of electrons with the classical descriptions of phonons. It has led to experiments of mechanical metamaterials possessing topological characteristics, such as topologically protected conducting edges or surfaces without back-scattering. This dissertation presents a new experimental approach for mechanically engineering topological metamaterials based on patterning magnetically coupled spinners in order to localize the propagation of vibrations and evaluate different …

Iii-Nitride Ultraviolet Light-Emitting Diodes: Approaches For The Enhanced Efficiency, Moulik Patel

Theses

III-nitride ultraviolet (UV) light-emitting diodes (LEDs) offer marvelous potential for a wide range of applications, including air/water purification, surface disinfection, biochemical sensing, cancer cell elimination, and many more. III-nitride semiconductor alloys, especially AlGaN and AlInN, have drawn significant attention due to their significant advantages that include environmental-friendly material composition, compact in size, longer lifetime, low power consumption, and tunable optical emission. However, the performance of III-nitride UV LEDs in terms of efficiency and output power is still deficient. The presence of high defects and dislocations due to lattice-mismatched epilayers, polarization induced quantum-confined Stark effect, electron overflow with low hole injection …

Calculating Elastic Properties Of Confined Simple Fluids, Christopher D. Dobrzanski

Dissertations

Confinement in nanoporous materials is known to affect many properties of the fluids confined within their pores. The elastic properties are no exception. This dissertation begins with an overview of the relevant literature on ways of obtaining elastic properties of confined fluids. It outlines some fundamental gaps in our understanding. The chapters following address some of these gaps in understanding elastic properties of the confined fluid, in particular, how the shape of the confining pore matters, how supercriticality effects the properties, how an equation of state designed for confined fluids can be used to calculate elastic properties, and if an …

Customized Boron And Magnesium-Based Reactive Materials Prepared By High Energy Mechanical Milling, Xinhang Liu

Dissertations

New reactive materials need to be developed having biocidal combustion products. When ignited, such material can add chemical biocidal effects to the common effects of high temperature and pressure. Biocidal combustion products are capable of deactivating harmful spores or bacteria, which can be released by targets containing biological weapons of mass destruction. Research showed that halogens, especially iodine, are effective as biocidal components of reactive material formulations. Recently, magnesium combustion product MgO is also found to have a biocidal effect. Thus, advanced formulations containing both magnesium and iodine are of interest; such formulations are prepared and investigated here.

Reactive materials …

Enzymatic Biofuel Cells In A Sandwich Geometry With Compressed Carbon Nanotubes/Enzyme Electrodes & Hybrid Patch Applications, Biao Leng

Dissertations

Enzymatic biofuel cells (EBFCs) convert the chemical energy of biofuels, such as glucose and methanol, into electrical energy by employing enzymes as catalysts. In contrast to conventional fuel cells, EBFCs have a simple membrane-free fuel cell design due to the high catalytic specificity of the enzymes, but the power densities obtained are lower. Although the primary goal of research on EBFCs has been to develop a sustainable power source that can be directly implanted in the human body to power bio-devices, other applications such as the use of a flexible film or fuel cell patch as a wearable power source …

Measurement Of Stresses And Their Effect On Transport In Thin Film Battery Electrodes, Subhajit Rakshit

Dissertations

At the moment, there is a significant push towards environmentally friendly energy production and gasoline-free transportation technologies. As a result, there is a renewed interest in energy storage devices such as lithium-ion batteries which will play a key role in providing energy storage capability for these applications. However, the current battery technology is reaching its limits and may not meet future energy storage demands. The increased demand and the limited lithium reserves in geographically remote areas of the earth will lead to higher cost of Li. The alternative battery technologies, such as sodium-ion batteries, are promising due to their low …

Utilizing Gis Technology For Brownfields Redevelopment, Jeffrey J. Duteau

Theses

Typically, when developers, banks and other organizations have an interest in a piece of property they perform an extensive information search to determine if the site is worth purchasing. This search could consist of tax and title information, the location of utilities and major roadways in the area, information on population demographics and environmental contaminant data. An information search of this type could take days, weeks or even months to compile. With a geographic information system (GIS), this search could take a matter of minutes and is displayed in an easy to understand graphic or map form along with a …

Trifluoroiodomethane As An Environmentally Friendly Gas For Water Patterning By Plasma Etching Process, Krit Aryusook

Theses

Trifluoroiodomethane (CF₃I), a non-global warming gas, has been investigated with study as a substitute for typical CFC etchants, such as CF₄ and C₂F₆, used in wafer pattering technology. This investigation was carried out by exposing dielectric films of silicon oxide (SiO₂) and silicon nitride (Si₃N₄) in CF₃I and C₂F₆/O₂ (used as a reference) plasma environments. The etch rate of these films was ascertained as function of applied rf power, etchant gas flow rate, reaction chamber operating pressure, and O_{2 …}

Microporous Silicon Dioxide/Vycor Membranes For Gas Separation, Justin R. Barone

Theses

This study focused on producing membranes for molecular sieving of gases by reducing the pore size of an already existing membrane structure. To do this, SiO₂ was deposited inside the pores of a Vycor tube with initial pore diameter of 4 nm. The film deposition took place by a low pressure chemical vapor deposition (LPCVD) process where diethylsilane (DES) and nitrous oxide (N₂O) were used as precursor gases. A counterflow reactant geometry was used where the precursor gases were flowed on both sides of the porous membrane. This deposition geometry gave higher selectivities and better mechanical stability. …

Synthesis And Characterization Of Silicon Dioxide Thin Films By Low Pressure Chemical Vapor Deposition, Sutham Niyomwas

Theses

Ditertiarybutylsilane ( DTBS ) and oxygen have been used as precursors to produce silicon dioxide films by low pressure chemical vapor deposition. These films were synthesized in the temperature range of 600°C to 800°C at constant pressure, and at different gas flow composition. The films were found to be uniform with a composition that varied with deposition temperature and gas flow ratio. The growth rate was found to follow an Arrhenius behavior with an apparent activation energy of 2.62 kcal/mol. The growth rate was seen to increase with higher distance between wafers and to vary as a function of square …

Synthesis And Characterization Of Silicon Dioxide Thin Films By Low Pressure Chemical Vapor Deposition Using Ditertiarybutylsilane And Oxygen, Sung-Jun Lee

Theses

This study is focused on the synthesis and characterization of silicon dioxide thin films deposited on silicon wafers by Low Pressure Chemical Vapor Deposition (LPCVD), using ditertiarybutylsilane (DTBS) as a precursor and oxygen as the oxidant. The dependence of film growth rate on various process parameters were studied. The growth rate was found to follow an Arrhenius curve with the variation in the temperature with an activation energy of 12.6 kcal/mol. The growth rate was found to be inversely proportional to the temperature in the range 550-750 °C. The refractive index and density were observed to be close to 1.47 …

Fabrication Of Integrated Optic Sensor To Monitor Pollutant Concentration In Effluents, Kiran Chatty

Theses

An attempt has been made to fabricate an integrated optic sensor to monitor pollutant concentration in effluents. Optic fiber has to be coupled to the waveguide in order to send light through the waveguide. In order to facilitate the easy coupling of the fiber to the waveguide, V-grooves were formed in the silicon substrate. In order to achieve this Silicon nitride was deposited to serve as an etch mask. An attempt was made to obtain low stress silicon nitride films.

This work also attempted to synthesize the materials required to fabricate the waveguide. LPCVD processes were developed to produce undoped …

Effect Of Lamellar Microstructure On The Permeability Of Polyethylene Films, Yufu Li

Theses

Lamellar microstructures can decrease the permeability to gases and vapors by increasing the diffusive path in plastic films, or the so-called "tortuosity" which depends on the aspect ratio, orientation, and the volume fraction of the dispersed material. In this research, different types and percentages of mica with relatively high aspect ratio are used as oxygen barrier materials in blown films. Both high and low density polyethylenes (HDPE and LDPE), as well as their blends are used as the matrix materials.

A decrease in permeability of both LDPE and HDPE films to oxygen is achieved with increasing volume fraction of the …

Low Pressure Chemical Vapor Deposition Of Silicon Dioxide And Phosphosilicate Glass Thin Films, Vijayalakshmi Venkatesan

Theses

Silicon dioxide thin films were synthesized on silicon and quartz wafers using Ditertiarybutylsilane(DTBS) and oxygen as precursors. Trimethylphosphite (TMP) was injected to obtain phosphosilicate glass. The films were processed at different temperatures between 700°C and 850°C at a constant pressure, and at different flow ratios of the precursors. The films deposited were uniform, amorphous and the composition of the films varied with deposition temperature and precursor flow ratios. The deposition rate increased with increasing temperature and with increasing TMP flow rate. The stresses were very low tensile in the case of undoped silicon dioxide film and tended towards being less …

Dynamic Mechanical Analysis Of Particulate Dental Composites, Minu Parekh

Theses

Typically, dental composites are used in different configurations and situations. When a cavity forms at the occlusal surface of a posterior tooth, a class I and class II filling is used, depending on the extent and nature of the cavity formed. These fillings have to be designed to resist mechanical abrasion and occlusal stress during chewing, bruxing and other tooth functions. Class IV fillings are also designed to resist biting stress. In these applications composites with high filler loading with filler particles of size >0.6μm are used. These composites are typically known as minifill or midifill composites. When more than …

Plasma Enhanced Chemical Vapor Deposition Of Stress Free Tungsten Films, David Perese

Theses

This study focuses on PECVD to make tungsten film for X-ray absorber for use in X-ray lithography applications. The previous LPCVD study was used for comparison of film properties. A cold wall, single wafer, Spectrum 211 CVD reactor was used for the deposition of tungsten from H2 and WF6. The growth kinetics were determined as a function of temperature, pressure and flow rate ratio. The deposition rate was found to follow an Arrehnius behavior between 300-500°C with an activation energy of 55.7 kJ/mol. The growth rate increased linearly with total pressure and H2 partial pressure. In the H2/WF6 ratio studies …

Characterization Of Low Pressure Chemically Vapor Deposited Boron Nitride Films As Low Dielectric Constant Materials, Manish Narayan

Theses

Boron nitride thin films were synthesized on Si and quartz wafers by low pressure chemical vapor deposition using borane triethylamine complex and ammonia as precursors. The films were processed at 400°C, 475°C and 550°C at a constant pressure of 0.5 Torr and at different precursor flow ratios.

The films deposited were uniform, amorphous and the composition of the films varied with deposition temperature and precursor flow ratios. The thickness of the film increased with increasing flow ratio, but, decreased with increasing temperature. The stresses in the film were either mildly tensile or compressive.

The least dielectric constant for the films …

Synthesis Of Boron Nitride/Vycor Composite Membrane Structures By An Optimized Lpcvd Process, Chenna Ravindranath

Theses

Since the advent of the idea of ultrafiltration, microporous membranes have come through a long way in establishing a niche as an efficient technology for gas separation applications. More and more research is aimed at reducing pore size towards nanolevels, when separation factor is the criterion rather than the permeability. This work is focused at synthesizing and characterizing microporous inorganic membranes for gas separations by molecular sieving. BN was deposited on mesoporous vycor tubes using triethylamine borane complex (TEAB) and ammonia as precursors. Effect of temperature and deposition geometry on permeability of various gases has been studied. Very high selectivities …

Low Pressure Chemical Vapor Deposition Of Tungsten As An Absorber For X-Ray Masks, Hongyu Chen

Theses

Tungsten film is one of promising materials for X-ray absorber in X-ray Lithography technology because of its high X-ray absorption and refractory properties. This study focus on CVD method to make tungsten film for X-ray absorber.

In this work, a cold wall, single wafer, Spectrum 211 CVD reactor was used for the deposition of tungsten from H, and WF6. The growth kinetics were determined as a function of temperature, pressure and flow ratio. The deposition rate of as deposited tungsten films was found to follow an Arrehnius behavior in the range of 300-500°C with an activation energy of 55.7 kJ/mol. …

The Photolithographic Patterning Of Porous Silicon Using Silicon Nitride And Silicon Carbide Films As Masks, Hong Wang

Theses

In this study, a simple photolithographic pattern process for porous silicon is described. The process utilizes silicon nitride or silicon carbide coated on the top of silicon wafer as a masks. Then a test pattern was projected on the sample by illumination during anodic etching in HF:ethanol solution which produced microcracks in regions illuminated during anodization. Creation of these microcracks resulted in formation of porous silicon in the underlying regions. The cracking is related to the stress in the thin film. The films with tensile stress exhibit cracking while compressive stress samples do not. Compared to silicon carbide films, silicon …

Aeration And Operation Of An Immobilized Cell Oxidative Bioreactor, James Joseph Woods

Theses

The primary purpose of this work is to help define the optimum window of operations for an immobilized cell oxidative bioreactor. The analytical technique employed requires no outside verification (such as G.C. analysis) and is independent of liquid flow rate. Method of aeration has been determined to be an important parameter for optimizing bioreactor efficiency, and optimization of the quantity of hydrogen peroxide added to provide oxygen during bio-oxidation has been investigated. Ammonium hydroxide as a fixed nitrogen source can be used to restore the vitality of the bioreactor under certain conditions.

The effects of several different methods of providing …

Low Pressure Chemical Vapor Deposition Of Copper Films From Cu(I)(Hfac)(Tmvs), Wei-Shang King

Theses

Recently, copper has been found as a possible substitute for Al alloys because of its low resistivity (1.67 μΩ • cm) and potentially improved resistance to electromigration. Conventional physical vapor deposition (PVD) method do not provide the conformal deposition profile for the high density integrated circuit, therefore, chemical vapor deposition (CVD) has become the most promising method for the resulting conformal profile.

In this work, a cold wall, single wafer, CVD tungsten reactor was used for the deposition of copper with Cu(I)(hfac)(tmvs). Film growth rates were between 100 to 800 A/min depending on processing conditions, and an Arrhenius type activation …

Synthesis Of Silicon Oxide/Vycor Composite Membrane Structures By An Optimized Lpcvd Process, Abhijit Datta

Theses

This study is focused on development of highly selective ceramic membrane structures consisting of silicon dioxide films synthesized by low pressure chemical vapor deposition (LPCVD) on mesoporous Vycor substrates. The ability of easily altering the composition of such films by varying the LPCVD processing parameters affords the opportunity of microengineering the pore structure by reducing the diameters of pre-existing pores in the support. The process parameters investigated include, deposition temperature, total pressure, and flow rate of oxygen. Both the kinetics and select properties of the deposits were examined. The growth rate as a function of temperature was seen to follow …

Artificial Dielectric Materials : Synthesis And Optical Characterization Of Small Metal Clusters Embedded In Polymeric Matrix, Nazneen Karim Shilpee

Theses

This study is concerned with the fabrication of films made of gold, nickel, and silicon clusters dispersed in a polymeric matrix. The films were fabricated by use of metal or semiconductor sputtering and plasma polymerization of Methyl Methacrylate monomer in a capacitively coupled RF (13.56 MHz) sputtering system. Optical transmittance and optical reflectance were measured as a function of wavelength. The optical absorption of metal or silicon clusters was studied as a function of cluster size. Cluster size and content were determined from Transmission Electron Micrographs (TEM). The absorption band resulting from a plasma resonance in the clusters was found …

Expert System For Preventive Maintenance The Aluminum Extrusion Press And Related Equipment, E-Ping Lin

Theses

ESPM is an Expert System for Preventive Maintenance that provides the framework for application-specific equipment maintenance tools. The expert system for preventive maintenance and diagnosis was developed for the Aluminum Extrusion Press and Related Equipment. The system is built in VP-Expert and is implemented on a personal computer.

The expert system includes many characteristics of an expert system cell because it can be expanded easily by adding new information to its knowledge base or by changing the existing information. The expert system can be connected directly with a PC system through a VP-Expert software package and can interact with C …