Materials Science and Engineering Commons^™

Inkjet Printing Of Resistive-Type Humidity Sensor For Harsh Environments, Hamed Kazerani

Dissertations

A flexible resistive-type humidity sensor for harsh environments is successfully designed and fabricated by an inkjet printing method using a Dimatix materials printer (DMP-2800 series from Fujifilm). Construction of the sensors is based on inkjet printed interdigitated silver electrodes on a polyimide flexible substrate along with an inkjet printable polyaniline (PANi) as humidity sensitive material. A copolymer of ethylene and vinyl alcohol (EVOH) is used as sensor protective coating. Double strand water- soluble PANi ink is synthesized by polymerization of aniline monomers with poly(4- styrenesulfonic acid) (PSSA) as a template.

Manufactured devices showed high sensitivity (/% @ 45%RH) to humidity …

Development Of X-Ray Holography Methods For Structure Determination : Application Of High Speed Detectors And Novel Numerical Methods, Yuhao Wang

Dissertations

Holographic methods show much promise to enable direct determination of atomic structure with minimal assumptions and approximations. The approach can, in principle, provide three dimensional information on atomic positions. However, significant developments in experimental techniques, instrumentation and in data collection and analysis are needed. A review of the holography method is given with a focus on X-ray fluorescence holography. Methods for analysis of X-ray holographic data are also reviewed. An overview of the detectors relevant to X-ray measurements is also presented. An experimental apparatus for rapid acquisition of X-ray holographs using novel X-ray detectors has been developed. The integration of …

Synthesis And Development Of Boron Nanotubes And Metal/Ceramic-Carbon Nanotube Composites, Jinwen Liu

Dissertations

The first part of this thesis will be focused on developing a facile and scalable solid — solid chemical vapor deposition (CVD) process using a solid boron precursor to synthesize crystalline boron nanotubes (BNTs) mixed with small amounts of boron nanofibers (BNFs). The synthesis involves the use of solid boron precursors - magnesium boride and magnesium borohydride, magnesium and nickel boride as co-catalysts, and porous MCM-41 zeolite as the growth template. Experimental parameters, such as temperature, grinding of constituents and starting precursor-catalyst-template compositions, were studied and optimized. Detailed characterization have been carried out using field-emission scanning electron microscopy (FE-SEM), transmission …

A Study Of Three Transition Metal Compounds And Their Applications, Zhen Qin

Dissertations

The La_5/8-yPr_yCa_3/8MnO₃ with colossal magnetoresistance (CMR) effect has a rich phase diagram and is well studied for its electronic phase separation phenomenon, where the ferromagnetic (FM) metal order co-exists and competes with the charge-ordered (CO) insulator phase. High Pr doping will favor the CO order, leading a sharp FM to CO dominated phase transition around Pr concentration of 0.3 and above. Hydrostatic pressure favors FM metallic order without damaging the sample and can be tuned continuously. In this study, pressurized-magnetic and resistivity measurements was done on a La_0.25Pr_0.375Ca_{0.375 …}

Study Of Mechanisms Of Phytotoxicity Of Alumina Nanoparticles, Anthony Elijius

Dissertations

Plant growth inhibitory effect of alumina nanoparticles has recently been reported (Ling Y, Watts D, 2004) but the mechanisms of such an effect are yet to be established. The phytotoxicity of aluminum and some of its compounds is well known, but the rapid expansion of nanotechnology resulting in the introduction of new sets of materials in the nanometer range has led to the development of new approaches, experimental methods and modes of investigation.

In this study, the observed phytotoxic effects of alumina nanoparticles suspension on five plant species (Zea mays, Cucumis sativus, Daucus carota, Brassica oleracea, Lactuca sativa) …

Mixing Of Nanosize Particles By Magnetically Assisted Impaction Techniques, James V. Scicolone

Dissertations

Nanoparticles and nanocomposites offer unique properties that arise from their small size, large surface area, and the interactions of phases at their interfaces, and are attractive for their potential to improve performance of drugs, biomaterials, catalysts and other highvalue- added materials. However, a major problem in utilizing nanoparticles is that they often lose their high surface area due to grain growth. Creating nanostructured composites where two or more nanosized constituents are intimately mixed can prevent this loss in surface area, but in order to obtain homogeneous mixing, de-agglomeration of the individual nanoparticle constituents is necessary.

Due to high surface area, …

New Media Icc Profiles Construction And Concerns, Reem El Asaleh

Dissertations

With the advent of the modern digital technology, users can now capture an image and reproduce it between different media, such as display it on LCD monitor or tablet computer, print it on desktop printer or send it to a printing press. The challenge has been then to maintain the accuracy of image colors during this reproduction, which has led to the development of Color Management Systems. Using these systems, the color reproduction across-media will be accomplished using device ICC profiles that describe each device’s color characterization data in a standardized format based on International Color Consortium (ICC) specifications.

ICC …

Atomic And Electronic Structure Studies Of Nano-Structured Systems : Carbon And Related Materials, Sumit Saxena

Dissertations

Modeling in the framework of density functional theory has been conducted on carbon nanotubes and graphene nano-structures. The results have been extended to non-carbon systems such as boron nanostructures. Computational studies are complemented by experimental methods to refine the structural models and obtain a better understanding of the electronic structure.

It is observed that the zigzag edged bilayered graphene nanoribbons are highly unstable as compared to their armchair counterparts. A novel approach has been proposed for the patterning of chirality/diameter controlled single walled carbon nanotubes. Nanotube formation is found to be assisted by edge ripples along with the intrinsic edge …

Novel Micron- And Nano-Scale Energetic Materials For Advanced Gun Propulsion, Their Material Properties, And Their Effects On Ballistic Performance, Thelma Gatuz Manning

Dissertations

This dissertation focused on the investigation of novel materials that are both energetic and inert in their micron- and nano-scale crystalline form. The characterization of the materials properties and its effects on the ballistic performance when incorporated into a composite material were evaluated as a gun propellant for application in a future weapon system for the US Army. Some of these materials may find dual use in civilian applications. Applications in small and medium arms, artillery, tank, aircraft, and shipboard gun systems will all benefit from these advancements. Not only will gun system performance be improved for greater stand-off range …

Formation Of Screen-Printed Contacts On Multicrystalline Silicon (Mc-Si) Solar Cells, Vishal R. Mehta

Dissertations

Commercial multicrystalline silicon (me-Si) solar cells use screen-printing process for depositing both the Ag paste based gridded front and Al based back (whole area) metal contacts.. This thesis relates to experimental and theoretical studies of contact formation mechanisms in silicon solar cells. Temperature distribution studies during optical processing by. attached thermocouples to cells indicates that the maximum temperature reached under the front silver metal is less. than 800°C; this is lower than the eutectic point of Ag-Si (≈835°C). An analysis of the interaction of Ag particles and Si via the constituents of glass is given. This mechanism leaches metallic ions …

Multi-Component Boron Coatings On Low Carbon Steel Aisi 1018, Naruemon Suwattananont

Dissertations

Boronizing and metalizing are thermo-chemical surface hardening treatments in which boron and metal atoms diffuse into the metal substrate forming metallic boride layers, providing complex properties of B-Me-Fe system.

To study multi-component boron coatings on low carbon steel AISI 1018, the simultaneous powder pack method of boronizing and metalizing was selected to perform the coatings. One B-Fe system and eight boron-metal (B-Me-Fe) systems from transition metals group IVB (Ti, Zr, Hf), group VB (Nb, Ta), and group VIB (Cr, Mo, W) were studied. The system specimens were thermo-chemically treated at 950°C for 4 hours in a crucible containing powder mixture …

Synthesis And Characterization Of Metal Oxide Semiconductors For Photoelectrochemical Hydrogen Production, Sudhakar Shet

Dissertations

The goal of this thesis is to investigate the properties of metal-oxide thin films on fluorine-doped tin oxide (FTO)-coated glass substrates, prepared by using radio- frequency (RF) reactive magnetron sputtering for photoelectrochemical (PEC) applications. Metal-oxide thin films as a photoelectrode are of special interest for PEC systems to produce hydrogen in an aqueous solution by solar energy due to their low cost and potential stability.

The following list represents some of the accomplishments and results of this work:

• Narrowing of N-incorporated ZnO (ZnO:N) was achieved by reactive sputtering in a O₂/N₂ mixture ambient, and ZnO:N films with …

Surface And Bulk Passivation Of Multicrystalline Silicon Solar Cells By Silicon Nitride (H) Layer : Modeling And Experiments, Chuan Li

Dissertations

The objective of this dissertation is to study passivation effects and mechanisms in Si solar cells, specifically, the surface and bulk passivation by hydrogen-rich PECVD silicon nitride (SiN :H) antireflection layer on multicrystalline silicon (me-Si) solar cells.

The passivation of silicon surface can be achieved in two ways: by field-effect passivation and/or by neutralization of interface states. In other words, the deposition should result in a high value of fixed charge, Qf and /or a low value of interface state density, D1. The surface recombination velocity can be described by Shockley-Read-Hall (SRH) statistics.

Current SRH formalisms have failed to explain …

Modeling Edge Effects Of Mesa Diodes For Silicon Photovoltaics, Jesse S. Appel

Dissertations

A mesa diode has been modeled and its performance under dark and illuminated conditions has been simulated using a commercial finite element software package. These simulations have led to a determination of the self-consistent solution to the continuity equations for electrons and holes using the steady-state drift-diffusion model for carrier dynamics coupled with electric potential determined from Poisson's equation. The purpose of these simulations has been to determine the influence of edge conditions on the overall performance of mesa diodes under dark and illuminated conditions.

Mesa diode arrays are fabricated on crystalline silicon solar cells. They are an array of …

Probing Spin, Charge And Lattice Coupling In Manganites, Zhiqiang Chen

Dissertations

Complex oxides such as the manganites exhibit an intimate coupling of the electron spin, charge and lattice degrees of freedom. The characteristic feature of these materials is the existence of a ground state topology with many closely lying minima. The system can be switched from one minimum to another by the application of external parameters such as strain, temperature, magnetic fields, or electrical fields. These materials thus exhibit large responses to these external parameters and can be used as novel sensors in data storage and other applications. Understanding the couplings will have an impact on the fundamental science of highly …

Ionic Liquids As Additives For Biodegradable Polyactic Acid, Ku-Il Park

Dissertations

In this study, two ionic liquids (IL) with different anions (decanoate, tetrafluoroborate) but with the same phosphonium based cation were evaluated as potential plasticizers and lubricants for polylactic acid (PLA) and also for their effects on its hydrolytic and thermal degradation. Both ILs at 5wt% were well dispersible and partly miscible with PLA as evidenced by scanning electron microscopy/energy dispersive x-ray scattering, SEMIEDX, and glass transition temperature, T_g, characterization, as well as from solubility parameters calculations.

The effects of the IL containing a decanoate anion were more pronounced on lubrication and degradation as evidenced by reduced melt viscosities …

Synthesis And Characterization Of Atmospheric Pressure Chemically Vapor Deposited Aluminum, Sipeng Gu

Dissertations

This study investigates the use of atmospheric pressure chemical vapor deposition (APCVD) to produce high quality aluminum coatings for corrosion protection of steel. The coatings were produced through thermal decomposition of tri-isobutyl-aluminum (TIBAL) over the 275 to 300°C temperature range. Under optimal deposition conditions, growth rates as high as 1.2 um/min were achieved. X-ray photoelectron spectroscopy, auger electron spectroscopy, glow discharge optical emission spectroscopy and nuclear reaction analysis revealed that the coatings consisted essentially of pure aluminum (~99 at.%) with oxygen and carbon present as minor constituents. The coatings were characterized in terms of their morphological, structural, electrical, and mechanical …

Ion Assisted Magnetron Sputtering Of Tantalum Thin Film Deposition And Characterization, Hua Ren

Dissertations

The purpose of this research was to investigate the effects of ion bombardment on the crystallographic phases of tantalum films during their deposition by magnetron sputtering process, and to gain understanding of the mechanism of the ion-solid interactions during the thin film growth. Tantalum (Ta) exists in two distinct crystallographic phases: a stable α-phase with a body centered cubic (bcc) lattice structure and a metastable β-phase with a tetragonal lattice structure. The tough and ductile α-phase Ta is desired in most industrial applications, such as diffusion barrier layers in integrated circuits, metallic corrosion protective layers, and in biomedical devices. The …

Formation Of Rdx Nanoparticles By Rapid Expansion Of Supercritical Solution : In Situ Characterization By Laser Scattering, Takuya Matsunaga

Dissertations

Cyclo-1,3,5-trimethylene-2,4,6-trinitramine (RDX), a well-known energetic material, is highly explosive. Reduction of the sensitivity of RDX is desired for safe handling and

storage in military applications. Data on the sensitivity of RDX in the 10-1000 µm crystal size range suggested that the impact sensitivity could be further reduced by reduction of the crystal size to the sub-micron or nano-scale (Armstrong, 1990). Recent research with nano-RDX obtained using Rapid Expansion of Supercritical Solutions (RESS) confirmed these expectations (Stepanov, 2005).

RESS process appeared to be one out of a few techniques of production of nanoscale energetic materials free of the risk of explosion. …

Nanostructured Composite Materials Based On Carbon Nanotubes And 3-D Photonic Crystals, Jing Chen

Dissertations

Carbon nanotubes (CNT) and in particular, single-wall carbon nanotubes (SWCNT) have been extensively studied, in large part, due to their unique one-dimensional crystalline structures and related electronic and optical properties. Various polymeric composite materials, which were based on carbon nanotubes, have been also developed in an attempt to combine the properties of polymer and CNT in a single film. Such composites were mainly formed by mixing carbon nanotubes within the polymer without special emphasis on the structure and thereby, the nanoscopic properties of the resultant material.

Photonic crystals belong to a class of man-made structures aimed at manipulating the propagation …

The Feasibility Of Micromachined Dynamic Resonant Beam Coriolis True Mass Flow Meter, Sang Hwui Lee

Dissertations

The technological advances of micro-electro-mechanical systems (MEMS) in the past two decades have been remarkable for innovations in microfluidic systems as well as automotive applications such as pressure sensors and accelerometers. MEMS flow sensing has emerged as a field of interest in microfluidics, with a variety of sensing methods being miniaturized, such as thermal anemometry, ultrasonic sensing and flow measurement based on the Coriolis effect. Coriolis sensing is particularly attractive since, unlike most other methods which provide volumetric flow information, Coriolis sensing is capable of providing a direct, true mass flow measurement. Because of this advantage, Coriolis flow sensing has …

In Vitro Drug Delivery Based On A Porous Membrane-Based Aqueous-Organic Partitioning System And Its Enhancements Through Mouse Skin, Qiuxi Fan

Dissertations

Novel approaches for transdermal drug delivery (TDD) based on a porous membrane-based aqueous-organic partitioning system have been investigated and successful deliveries were observed. Doxycycline hydrochloride (HCl), a polar antibiotic drug with a relatively large molecule weight (MW: 480.1) was studied as a basic model agent. Its controlled release using this technique was studied first. Satisfactory release profiles demonstrate the practical potential of such a system to achieve useful controlled release rates. The enhancer linoleic acid was essential to successful release using a mouse skin beneath a porous polymeric membrane. The transport rates of smaller molecules e.g., caffeine and nicotine from …

Optimization Studies Of Thermal Bimorph Cantilevers, Electrostatic Torsion Actuators And Variable Capacitors, Wuyong Peng

Dissertations

In this dissertation, theoretical analyses and optimization studies are given for three kinds of MEMS devices: thermal bimorph cantilevers, electrostatic torsion actuators, and variable capacitors. Calculation, simulation, and experimental data are used to confirm the device behavior and demonstrate the application of the design approaches.

For thermal bimorph cantilevers, an analytical model is presented which allows theoretical analysis and quantitative optimization of the performance based on material properties and device dimensions. Bimorph cantilevers are divided into two categories for deflection optimization: either the total thickness is constant, or the cantilever has one constant and one variable layer thickness. The optimum …

Mechanisms Of Layer-Transfer Related To Silicon-On-Insulator Structures, Bo Chen

Dissertations

The objective of this dissertation was to study the mechanisms that affect an efficient hydrogenation process in silicon and to validate a hypothesis concerning the hydrogenation mechanism of pre-implanted silicon wafers under hydrogen-plasma processing. These studies are related to a general process. A trapping layer for hydrogen was introduced by ion beam implantation into the silicon wafer. Next, this wafer was hydrogenated using a hydrogen plasma. It was hypothesized that the trapping layer acts as a getterer for the hydrogen diffusing into the silicon wafer. It was found that a large amount of hydrogen could be absorbed in the trapping …

Boron And Phosphorous Implantation Into (100) Germanium : Modeling And Investigation Of Dopant Annealing Behavior, Yong Seok Suh

Dissertations

Germanium is increasingly being considered at this time for future silicon compatible optoelectronic and complementary metal oxide semiconductor (CMOS) device application. Germanium implantation will be a critical process for future device fabrication. However, critical properties like Pearson parameters and dopant activation temperatures are not well established. In this study, boron and phosphorus were implanted into (100) germanium with energies ranging from 20 to 320 keV and doses of 5 x 10¹³ to 5 x 10¹⁶ cm^-2. The behavior of the boron and phosphorus before and after annealing for 3 hours at 400, 600 or 800°C in …

A Micromachined Thermo-Optical Light Modulator Based On Semiconductor-To-Metal Phase Transition, Lijun Jiang

Dissertations

In this research, a micromachined thermo-optical light modulator was realized based on the semiconductor-to-metal phase transition of vanadium dioxide (VO₂) thin film. VO₂ undergoes a reversible phase transition at approximately 68 0C, which is accompanied with drastic changes in its electrical and optical properties. The sharp electrical resistivity change can be as great as five orders. Optically, VO₂ film will switch from a transparent semiconductor phase to a reflective metal phase upon the phase transition. The light modulator in this research exploits this phase transition related optical switching by using surface micromachined low-thermal-mass pixels to achieve …

Reactive Modification Of Polyesters And Their Blends, Chen Wan

Dissertations

As part of a broader research effort to investigate the chemical modification of polyesters by reactive processing a low molecular weight (MW) unsaturated polyester (UP) and a higher MW saturated polyester, polyethylene terephthalate (PET), alone or blended with polypropylene (PP) were melt processed in a batch mixer and continuous twin screw extruders. Modification was monitored by on-line rheology and the products were characterized primarily by off-line rheology, morphology and thermal analysis. Efforts were made to establish processing/property relationships and provide an insight of the accompanying structural changes. The overall response of the reactively modified systems was found to be strongly …

Fabrication And Characterization Of Microcrystalline Silicon Solar Cells, Liwei Li

Dissertations

In this study, single junction p-i-n μc-Si:H solar cells were prepared using plasma of silane diluted by hydrogen in a low-cost, single chamber, non-load-locked RF-PECVD system. Direct structural characterization of μc-Si:H solar cells, rather than stand-alone films, was conducted using Raman Spectroscopy, XRD, and AFM. Strong correlations among device deposition, i-layer structural properties, and device performance have been established. With such correlations, critical issues in fabricating low-cost, large-scale, high performance μc-Si:H solar cells were identified.

The critical importance of seeding processes in determining the microstructure of μc-Si:H i-layers and performance of μc-Si:H solar cells has been demonstrated. Using …

Effects Of Implementation Of Decaborane Ions In Silicon, Cheng Li

Dissertations

The next generations of Si microelectronic devices will require ultra shallow p-type junctions formed by implantation of B ions with energies below 1 keV, at which available beam currents are severely limited by space charge effects. To solve this problem, decaborane (B₁₀H₁₄) cluster ion implantation has been suggested as an attractive alternative to conventional B implants, because one decaborane ion implants ten B atoms simultaneously and each of the B atoms only carries approximately 1/11 of the total ion energy. Thus the same implantation depth and dose as with monomer B ions can be obtained using …

Development Of An Integrated Photonic Sensor For Monitoring Hazardous Organics, Dianhong Luo

Dissertations

In this study, an integrated photonic sensor has been designed and fabricated for the purpose of monitoring hazardous organics in the environment. The operation of the sensor is based on the principles of the Mach-Zehnder interferometry. The sensor consists of a patterned waveguide structure made of phosphosilicate core and silica cladding. LPCVD processes were developed to produce undoped cladding and doped core silicon dioxide films. Diethylsilane (DES), Trimethylphosphite (TMP) and oxygen were used as the precursors for the deposition process. The effects of the O₂/DES ratio and deposition temperature on the properties Of SiO₂ films were investigated. …