Chemical Engineering Commons^™

Printing Functional Electronic Circuits And Components, Ahmed Tausif Aijazi

Dissertations

The purpose of this study was to investigate the challenges in printing reliable multilayer flexible circuits, devices and components. Gravure was used as the primary printing process for this work, but due to some limitations of gravure, other printing methods were also investigated. At first a systematic study was done to determine the optimum parameters for the gravure printing of sub 50 micron lines. Commercially available silver nanoparticle inks were printed on a lab scale gravure printer, Accupress®. The highest resolution line that was electrically conductive was 36μm wide. The 9μm, 18μm and 27μm lines were printed but were not …

Lntegration Of Conventional Lithography And Printing Processes As A Key Enabling Technology For Printed And Flexible Sensing Systems, Binu Baby Narakathu

Dissertations

Sensors, which are used ubiquitously in a wide variety of applications, are revolutionizing the already ever-changing world we live in by providing real-time information about our surroundings. This dissertation focuses on the integration of conventional photolithography and printing processes as a key enabling technology for printed and flexible sensing systems.

Initially, an efficient opto-electrochemical sensing system, for the dual detection of heavy metal compounds was successfully developed. A novel microfluidic flow cell, with a reservoir volume of 25 μl, was designed and fabricated using acrylic. An electrochemical sensor with gold (Au) interdigitated electrodes (IDE) on a glass substrate was photolithographically …

Evaluation Of Environmental Materials As Thermal Witness Materials, Shashank Vummidi Lakshman

Dissertations

New and complex energetic materials are under development for achieving tunable pyrotechnical events for applications such as neutralization of biological weapons, bunker busters and many others. To guide the development of hybrid materials, the pyrotechnical environment they produce requires higher degree of characterization i.e. good description of spatial and temporal temperature distribution.

Temperature measurements in pyrotechnical events are especially challenging, where the temperature of the environment rises more than 2000 K on microseconds to few milliseconds time scale. These environments produce high thermal stress where traditional sensors like thermocouples, optical pyrometers struggle to describe the dynamic changes in the environment. …

Novel Scrubbing Systems For Post-Combustion Co2 Capture And Recovery, Tripura Mulukutla

Dissertations

Power plant emissions of flue gas releases considerable CO₂ to the atmosphere; CO₂ is considered to be the main contributor to global warming. Several gas absorption techniques are being investigated to reduce the capital and operating costs for CO₂ capture from post-combustion flue gas. Conventional method of CO₂ capture by an aqueous solution of monoethanolamine (MEA) and its subsequent stripping in a separate tower with steam at 120°C, is a highly energy intensive process. The low partial pressure of CO₂ in the flue gas inhibits the application of CO₂-selective membranes unless methods are …

Ignition Mechanism In Nanocomposites Thermites, Rayon Williams

Dissertations

Nanocomposite thermites (n-thermites) have been actively investigated for a wide range of potential applications including propellants, explosives, and pyrotechnics. There have been several recent efforts aimed at understanding ignition mechanisms of nanocomposite reactive materials. Although significant progress has been made, ignition mechanisms remain elusive. At the same time, a robust ignition model is required to incorporate these materials in practical energetic formulations. A challenge of this effort is to describe the mechanisms of ignition of n-thermites prepared by Arrested Reactive Milling (ARM) with different stimuli, including heat, spark and impact and also develop a multi-step kinetic model describing different processes …

Synthesis And Characterization Of Metal-Based Reactive Powders, Yasmine Aly

Dissertations

Aluminum added to propellants, explosives, and pyrotechnics, boosts their energy density. Different approaches were investigated that could shorten aluminum ignition delays, increase combustion rates, and decrease the tendency of aluminum droplets to agglomerate. Here, Al-based reactive, mechanically milled materials are prepared and characterized.

For powders with Fe, Ni, or Zn additives, the particles consist of an aluminum matrix and inclusions of Fe, Ni, or Zn comprising 10 at % of the bulk composition. For additives of Ni and Zn, only short milling times can be used to prepare composites; intermetallic phases form at longer milling times. Thermogravimetric analysis shows selective …

Integrating 3d Layered Manufacturing With Photonic Sintering, Precision Machining And Smart Coating Techniques For Rapid Casting Applications, Hemant Bohra

Dissertations

Developments in rapid casting technologies have led to a new era of inclusion of 3D printing. Three-Dimensional (3D) printing provides the flexibility and ease of reproducing a sand mold directly from CAD models, eliminating patterning steps, thus reducing the process time for creating prototypes. In addition to minimizing processing steps, 3D printing provides the advantages of higher precision and the ability to produce complex shaped sand molds, but it simultaneously possesses some limitations and concerns related to throughput, safety and logistics.

This study proposes an alternative method for creating sand molds by introducing a hybrid rapid prototyping approach to overcome …

Fundamental Investigations Of Clay/Polymer Nanocomposites And Applications In Co-Extruded Microlayered Systems, Jeremy John Decker

Dissertations

The second and fourth generations of hydroxylated dendritic polyesters (HBP2, HBP4) were combined with unmodified sodium montmorillonite clay (Na+MMT) in water to generate a broad range of polymer clay nanocomposites from 0 to 100% wt/wt Na+MMT. X-ray diffraction (XRD) and transmission electron microscopy (TEM) were used to investigate intercalation states of the clay galleries. It was shown that interlayer spacings were independent of generation number and changed over the composition range from 0.5 nm to 3.5 nm in 0.5 nm increments that corresponded to a flattened HBP conformation within the clay tactoids.

The HBP4/Na+MMT systems were investigated to study the …

Improved Efficiency Organic Photovoltaic Cells Through Morphology Control And Process Modification, Qi Wu

Dissertations

Organic photovoltaic (OPV) cells have drawn great attention due to the potential to produce flexible, light weight, affordable solar cells using polymer organic photovoltaic materials; however, the current power conversion efficiency achieved for these systems is too low for widespread implementation of the technology. Morphology and phase separation are key factors determining the performance of organic photovoltaic cells. Precise control of the size and distribution of the phase-separated photoactive domains is necessary for optimum photon-electron conversion. Polyhedral oligomeric silsesquioxane (POSS) nanostructered chemicals have the potential to provide enhanced control of morphology, crystallinity, and phase dispersion in polymeric blend systems. In …

Fluorine Containing Uv-Curable Materials For Advanced Transport Applications, James Thomas Goetz

Dissertations

The characterization of structure, thermal, gas transport, and free volume properties of two unique UV cured polymeric systems are studied and reported. In the initial pursuit of waterproof high water vapor transport membranes, it became apparent that the UV curing of fluorinated materials yielded routes to develop unique materials that fundamentally challenge conventional models for free volume and light gas transport behavior. UV-curing provides a means to rapidly “lock-in” morphologies that are accessible in the small molecule, monomer phase but rapidly become kinetically inaccessible when constraints such as covalent bonding and cross linking limit motion in the polymer system. This …

Kinetic Analysis Of Thiol Oxidation To Study The Effects Of Fluorinated Groups On Metal Phthalocyanine Catalysts, Nellone Eze Reid

Dissertations

The oxidation of thiol (RSH) to disulfide (RSSR) is important biologically and industrially. Corrosive and malodorous thiols exist as contaminants in wastewater discharge from mining facilities, pulp and paper mills, tanneries, and oil refineries. The elimination of thiols from petroleum products is necessary for even cleaner fuels. Thiols in gas products can also inhibit catalyst activity for some downstream processes.

Experiments and mechanistic kinetic studies were conducted for the aerobic oxidation of 2-mercaptoethanol (2-ME) and 4-fluorobenzenethiol (4-FBT) catalyzed by cobalt phthalocyanines: H₁₆PcCo, F₁₆PcCo, and F₆₄PcCo, each exhibiting a metal center subject to increasing Lewis …

Discrete Element Method Based Scale-Up Model For Material Synthesis Using Ball Milling, Priya Radhi Santhanam

Dissertations

Mechanical milling is a widely used technique for powder processing in various areas. In this work, a scale-up model for describing this ball milling process is developed. The thesis is a combination of experimental and modeling efforts.

Initially, Discrete Element Model (DEM) is used to describe energy transfer from milling tools to the milled powder for shaker, planetary, and attritor mills. The rolling and static friction coefficients are determined experimentally. Computations predict a quasi- steady rate of energy dissipation, Ed, for each experimental configuration. It is proposed that the milling dose defined as a product of Ed and milling …

Investigation Of Recycled Paper Deinking Mechanisms, Veronika Husovska

Dissertations

The use of water-based inks is on the rise. Sub-micron pigment particles are used for flexographic and inkjet water-based inks. Conventional deinking eliminates larger particles than those from these new ink systems. Therefore, water-based inks represent recycling difficulty.

Deinking experiments of water-based inks are carried out. The deinking strategy initially investigated elimination of pressure sensitive adhesive due to similar acrylic polymer chemistry used in water based inks. The impact of pH on stickies and ink agglomeration during deinking is studied. Experiments in acidic regions show growth of acrylic inks and stickies agglomerates, simplifying elimination.

Pre-recycling of water-based inks is explored. …

Batch And Continuous Production Of Stable Dense Suspensions Of Drug Nanoparticles In A Wet Stirred Media Mill, Afolawemi Afolabi

Dissertations

One way to improve the bioavailability of poorly water-soluble drugs is to reduce particle size of drug crystals down to nanoscale via wet stirred media milling. An increase in total surface area per mass loading of the drug and specific surface area as well as reduced external mass transfer resistance allow a faster dissolution of the poorly-water soluble drug from nanocrystals. To prevent aggregation of nanoparticles, polymers and surfactants are dissolved in water acting as stabilizers via adsorption onto the drug crystals.

In the last two decades, ample experimental data were generated in the area of wet stirred media milling …

Pressure Swing Membrane Absorption Process For Separation Of Low Temperature Post-Shift Reactor Syngas, John Chau

Dissertations

This thesis is concerned with a cyclic pressure swing membrane absorption process (PSMAB) for separation of the feed gas mixture containing —40% CO₂-He balance using pure ionic liquid, 1-butyl-3-methylimidazolium dicyanamide ([bmim][DCA]), and its solution containing poly(amidoamine) (PAMAM) dendrimer Gen 0 primarily with a dry feed gas. An advanced pressure swing membrane absorption process is developed to produce purified He as a surrogate for H₂ at a high pressure from simulated low- temperature shifted syngas for different membrane modules. The PSMAB process also simultaneously produces a highly purified CO₂ stream containing bulk of the CO₂ in …

New Approaches On Deinking Evaluations, Roland Gong

Dissertations

Paper recycling in the U.S. is the most successful program of environmental sustainability. Approximately two thirds of consumed paper products were recycled, according to the EPA and AF&PA. However, domestic mills only applied one third of recycled fibers into new products, which is much lower than reported in China (67%). The domestic recycle mills claimed that outdated facilities, poor recycled fiber quality and high manufacturing cost are the major issues. They also said that these recycle mills have been put in a “no-win” position, which threatens the whole recycling loop eventually. A case study about Chinese recycle mills has been …

The Effect Of Nanoclays On The Properties Of Aspirin Modified Enteric Polymer Prepared By Hot-Melt Mixing, Nonjaros Chomcharn

Dissertations

Melt mixing in batch equipment or continuous extruders is a technique that recently gained the attention of the pharmaceutical industry. This dissertation investigates two controlled-release drug delivery systems. The first system, namely the enteric matrix, contains an active pharmaceutical ingredient (API) and plasticizer in an enteric polymer while in the second system a nanoclay is added to the enteric matrix, to produce a polymer nanocomposite. The first system employs hot-melt mixing to prepare a modified enteric matrix, as a delayed-release dosage form. Different concentrations of aspirin (ASP) ranging from 10 – 30% w/w are melt-mixed with a plasticized Eudragit® …

Reaction Mechanisms Of Hydrocarbon And Mercury Systems In The Atmosphere And In Combustion: A Theoretical Study Of Thermochemical And Kinetic Properties, Itsaso Auzmendi Murua

Dissertations

The continuing increase in the world population and the rapidly changing lifestyle and education of this population projects significant increases in energy requirements. Global warming is a worldwide major concern with a very serious potential stress on our climate threatening major changes to the environment. It is, without question, of major importance to improve the efficiency and optimize the current available combustion processes and fuel sources, to develop alternative fuels and to reduce the emissions of toxic pollutants.

The objective of this dissertation is to present thermochemical, kinetic and modeling results on two reference fuels (the land vehicle fuel isooctane …

Metal Based Reactive Nanocomposites Prepared By Cryomilling, Shasha Zhang

Dissertations

Aluminum is one of the most commonly used metal fuel additives for propellants, explosives, and pyrotechnics. Recent interest has been focused on replacements for aluminum as fuel additives to achieve higher combustion temperatures and stronger pressure pulses for applications in advanced munitions systems. Two applications are addressed in this work. In the applications for explosives designed to defeat stockpiles of chemical and biological weapons, it is of interest to develop multifunctional materials combining the high energy density of metal fuels with the biocidal activity of halogens. A challenge of this effort is to design and prepare powder-like Al-I2 materials which …

Separation Of Various Organic-Organic And Aqueous-Organic Solutions Via Pervaporation, John Tang

Dissertations

Pervaporation, an energy saving separation process, can be useful in pharmaceutical processing. However, the organic solvents involved in pharmaceutical product synthesis are chemically demanding; very few polymers are able to withstand them. An ideal membrane would be polymeric having a high thermal, chemical and mechanical stability. Such a membrane is made of a copolymer of polydimethyldioxole and tetrafluoroethylene known as PDD-TFE of the CMS-3 variety with a very high free volume. This novel membrane is used to separate a variety of organic-organic and aqueous-organic mixtures. An earlier study based on water-ethanol-isopropanol has shown evidence that the membrane selectivity may be …

Particle Engineering Via Surface Modification During Micronization For Pharmaceutical Applications, Xi Han

Dissertations

Improving the dissolution rate of Biopharmaceutics Classification System (BCS) class II drugs is an important research area. Micronization which can increase the specific surface area is a promising method to improve the dissolution rate. Micronization alone, however, can lead to downstream processing problems related to poor flow and dispersion properties. The importance of the flowability of pharmaceutical powders is well-documented in the literature. It is, therefore, important to develop a method that can simultaneously overcome these processing issues and allow for micronizing the API. In this work, dry particle coating technique is investigated in the context of micronizing API powders …

Mathematical Modeling Of Heavy Metals Diffusion And Removal From Cylindrical Cement Forms Coated With Bio-Film, Mojdeh Tabatabaie

Dissertations

A mathematical model is developed to predict bioleachi ng of heavy metals from long cylindrical shape cementitious samples. In this model, the metal concentration difference within the solid and its surface is considered as the main driving force for transport of metals to the surface of a sample at a given temperature and pressure. Fick’s first and second law are applied to explain the motion of contaminants in a long and uniform cylindrical solid. In addition, the model considers Michaelis-Menten type kinetics, a special case of the widely accepted Langmuir-Hinshelwood reaction mechanism, at the surface of the encapsulating cylinder. The …

Gravure Printability Of Indium Tin Oxide Nanoparticles On Glass And Pet Films For Applications In Printed Electronics, Dania Awni Alsaid

Dissertations

The advancements in the field of solution processable electro-active materials and their ability to be printed on different substrates have led to the evolution of printed electronics. In this field, electronic components are manufactured with conventional printing methods. Transparent electrodes made from indium tin oxide (ITO) are part of many electronic devices. Currently in industry, highly conductive ITO films are prepared by sputtering. The sputtering and then patterning of ITO films is a sophisticated process that consumes high energy, generates waste and produces films with limited flexibility. Therefore, there is a need to investigate processing methods for creating ITO films …

Inkjet Printability Of Electronic Materials Important To The Manufacture Of Fully Printed Otfts, Sooman Lim

Dissertations

In this study, the inkjet printability of materials important to fabricating OTFTs was researched. In order to understand the jetting evolution of inkjet printed inks, simulations were performed with a nano copper and nano particle silver ink. To predict the inkjettability of the nano copper ink, Z and Oh numbers at different temperatures were determined. The results from the simulation studies were compared to experimental results obtained using a Dimatix inkjet printer. For the semiconductor ink, the inkjet printability of two organic semiconductors, P2TDC17FT4 (poly[(3,7-diheptadecylthieno[3,2-b]thieno[2',3':4,5]thieno[2,3-d]thiophene-2,6-diyl)[2,2'-bithiophene]-5,5'-diyl] dissolved in 1,2-dichlorobenzene and P3HT (poly-3 hexylthiophene) were compared to determine the relationship between drop …

Investigation Of The Fracture Phenomena During The Milling Process Of Inorganic Particulates And Brittle Fracture Of Polymer Composites Using Fractal Theory, Zheng Qian

Dissertations

This dissertation investigates the applicability and usefulness of applying Fractal mathematics and to the fracture of brittle particulates in Fluid Energy Mill devices, and in particular quantifying the resulting power law particle size distributions, examining the Surface Fractal Dimension of milled particulates, and relating the Izod Impact Strength values of composites of polypropylene and Calcium carbonate particulates which are large un-milled, small milled, as well as small and produced by the simultaneous milling and coating with nano-silica to the Surface Fractal Dimension of the impact fracture surfaces.

First, the dissertation examines the behavior of un-coated and micron-sized wax pre-coated particulates …

Desalination Of Brine And Produced Water By Membrane Distillation At Lower As Well As Higher Temperatures And Pressures, Dhananjay Singh

Dissertations

Direct contact membrane distillation (DCMD)-based desalination process is a thermally- driven separation process where a hydrophobic microporous membrane separates a hot brine feed and a cold distillate which condenses the water vapor from the hot brine passing through the membrane pores. So far, DCMD has been explored for hot brines and other aqueous solutions below 100oC. For feed solutions above 100oC, DCMD has an extra advantage over other conventional separation processes like reverse osmosis (RO) which requires cooling of the feed solution costing additional energy; further, RO can not utilize the heat available in the feed solution. Produced water obtained …

Single And Multiphase Mixing In Partially Filled Stirred Vessels, Shilan Motamedvaziri

Dissertations

In many industrial applications, mixing vessels have a liquid height-to-tank diameter ratio, H/T, equal to, or larger than 1. However, there are many instances where this ratio is lower than 1, as in all those cases in which the vessel is either emptied or filled. Even when H/T<1, sufficient agitation must still be provided in order to attain the desired process objectives. When the impeller submergence is reduced as a result of lowering the liquid level, the fluid dynamics of even a single-phase stirred liquid can become quite complex, with different regimes possibly existing depending on the geometric characteristics of the system (such as impeller clearance, liquid height, or liquid submergence above the impeller). The objectives of this work were to study in detail the hydrodynamic changes that occur when H/T is decreased, and to determine the minimum liquid levels and the critical impeller submergence for different impeller off-bottom distances, impeller diameters and agitation speeds where adequate mixing process can still be achieved, both in a single liquid phase and in solid-liquid suspensions.

Flat-bottomed, baffled vessels (5L, 12L, 20L and 170L) equipped with a single disk turbine (DT) of four different sizes placed at five different impeller off-bottom clearances were used here to study the system's hydrodynamics and related mixing phenomena. A number of experimental tools were used to analyze the systems under investigation, including: …

Hot-Melt Mixing Of Partially Miscible Active Pharmaceutical Ingredient-Polymer Mixtures, Min Yang

Dissertations

Solid dispersion/solution processes for producing pharmaceutical oral dosages such as hot-met extrusion (HME) have received increasing attention by industry and academe because they can enhance drugs’ solubility and even bioavailability to a great extent by converting drugs from crystalline to amorphous form. HME can be carried out at two process temperature regimes: one where T_process > T_m of the drug and the T_g of the polymer (or the T_m for the case of semi-crystalline polymers); the other at T_m > T_process > T_g (T_m for the case of semi-crystalline polymer). Processing below the drug’s …

Theoretical Prediction Of Drug Release In Gi Tract From Spherical Matrix Systems, Naga Lakshmi Ramana Susarla

Dissertations

The significance of controlled release drug delivery systems (CRDDS) lies in their ability to deliver the drug at a steady rate thus reducing the dosage interval and providing a prolonged pharmacodynamic effect. But despite the steadily increasing practical importance of these devices, little is known regarding their underlying drug release mechanisms. Mathematical modeling of these drug delivery systems could help us understand the underlying mass transport mechanisms involved in the control of drug release. Mathematical modeling also plays an important role in providing us with valuable information such as the amount of drug released during a certain period of time …

Effects Of Operating And Geometric Variables On Hydrodynamics And Tablet Dissolution In Standard And Modified Dissolution Testing Apparatuses 2, Yimin Wang

Dissertations

Dissolution testing is routinely conducted in the pharmaceutical industry to provide critical in vitro drug release information for quality control purposes, and especially to assess batch-to-batch consistency of solid oral dosage forms such as tablets. Among the different types of apparatuses listed in the United States Pharmacopoeia (USP), the most commonly used dissolution system for solid dosage forms is the USP Dissolution Testing Apparatus 2, consisting of an unbaffled, hemispherical-bottomed vessel equipped with a 2-blade radial impeller.

Despite its extensive use in industry and a large body of work, some key aspects of the hydrodynamics of Apparatus 2 have received …