Engineering Commons^™

Multi-Scale Computational Modeling Of Metal/Ceramic Interfaces, Abu Shama Mohammad Miraz

Master's Theses

Multi-scale atomistic calculations were carried out to understand the interfacial features that dictate the mechanical integrity of the metal/ceramic nanolaminates. As such, first principles density functional theory (DFT) calculations were performed to understand the electronic and atomistic factors governing adhesion and resistance to shear for simple metal/ceramic interfaces, whereas molecular dynamics (MD) simulations were performed to observe the impact of interfacial structures, such as misfit dislocation network geometries and orientation relationships, on interfacial mechanical properties.

For the DFT investigation, we choose metals with different crystal structures, namely - Cu (fcc), Cr (bcc) and Ti (hcp) along with a variety of …

Multi-Scale Computational Modeling Of Metal/Ceramic Interfaces, Abu Shama Mohammad Miraz

Doctoral Dissertations

Multi-scale atomistic calculations were carried out to understand the interfacial features that dictate the mechanical integrity of the metal/ceramic nanolaminates. As such, first principles density functional theory (DFT) calculations were performed to understand the electronic and atomistic factors governing adhesion and resistance to shear for simple metal/ceramic interfaces, whereas molecular dynamics (MD) simulations were performed to observe the impact of interfacial structures, such as misfit dislocation network geometries and orientation relationships, on interfacial mechanical properties.

For the DFT investigation, we choose metals with different crystal structures, namely - Cu (fcc), Cr (bcc) and Ti (hcp) along with a variety of …

Nanoengineered Core-Shell Structures Using Tubile Halloysite Clay, Yusuf A. Darrat

Doctoral Dissertations

Halloysite nanotubes are a versatile nanomaterial that can be used in a wide variety of applications. They have a unique structure which could be described as a flat material that consists of silica on one side and alumina on the other; this structure is rolled up in a way naturally forming an internal 10-15 nm lumen and interlayer spacing. This could lead to many potential applications for example incorporating halloysite as a template material or as a support structure. They are an inexpensive clay material that is available in large quantities (thousands of tons), so they may be practically used …

Increasing The Functionality Of Additive Manufacturing Through Atmospheric Microplasma And Nanotechnology, Alexander Jon Ulrich

Doctoral Dissertations

Additive Manufacturing (AM) has been changing the manufacturing landscape for the last 20 years. As the interest and demand for both polymer and metal-based 3D printing has grown, the materials and machines used have increased in capabilities. Despite the growth and advancement, there are still a large number of improvements that can be made to add functionality to 3D printers. Metal AM, a subcategory of 3D printing, has garnered much attention among industrial applications with large companies such as General Electric trying to implement the technology to increase innovative designs for motors. Some of the limitations on AM have to …

Migration And Electropolymerization Of Methyl Methacrylate In Hardened Cement Paste Via Electrokinetic Treatment, Xi Xie

Doctoral Dissertations

Porous concrete structures are susceptible to the intrusion of chemical species, such as sulfates, chlorides, and carbon dioxide. Many technologies have been developed to repair or rehabilitate damaged concrete. These include cathodic protection, corrosion inhibitor addition, or the use of coatings and sealers. In recent years, a developing technology, electrokinetic nanoparticle treatment, has been shown to reduce concrete porosity, increase strength, promote corrosion resistance, and extend durability. This dissertation was conducted to explore a novel treatment to reduce the porosity of concrete via the application of electrokinetic transportation and electro-initiated polymerization of methyl methacrylate (MMA).

Potassium persulfate (PSP) was used …

Investigating The Rapid Curing Possibility Of Geopolymer Concrete, Ashlesh Banjara

Master's Theses

Recent studies of heat-cured fly ash based green geopolymer concrete have shown its suitability for fabrication of structural members. Fabrication of these structural members requires continuous moderate heating (145°F) for 24 hrs, and an oven essential, for a large member can quickly turn into an energy guzzler, potentially eliminating the green credentials of the product. The proposed research involves the development of a frontal polymerization (FP) method that achieves rapid curing of geopolymer at ambient condition after short-term heat application. Initial work shows thermal FP in geopolymer is a possibility and might be a solution to the problem. The process …

Characterization Of Nanomaterials For Thermal Management Of Electronics, Amit Rai

Doctoral Dissertations

Recently, there has been a growing interest in flexible electronic devices as they are light, highly flexible, robust, and use less expensive substrate materials. Such devices are affected by thermal management issues that can reduce the device’s performance and reliability. Therefore, this work is focused on the study of the thermal properties of nanomaterials and the methods to address such issues. The goal is to enhance the effective thermal conductivity by adding nanomaterials to the polymer matrix or by structural modification of nanomaterials. The thermal conductivity of copper nanowire/polydimethylsiloxane and copper nanowire/polyurethane composites were measured and showed more than threefold …

Effective Magnetic And Electric Response Of Composite Materials, Mona Hassan Alsaleh

Doctoral Dissertations

Metamaterials (MMs) are nanocomposite materials consisting of metal-dielectric resonators much smaller in size than the wavelength of the incident light. Common examples of metamaterials are based on split ring resonators (SRRs), parallel wires or strips and fishnet structures. These types of materials are designed and fabricated in order to provide unique optical responses to the incident electromagnetic radiation that are not available in naturally existing materials. The MMs can exhibit unusual properties such as strong magnetism at terahertz (THz) and optical frequencies. Additionally, negative index materials (NIMs) can provide negative index of refraction which can be used in many applications …

Electrical Characterization Of Graphene And Nanodiamond Nanostructures, A Z M Nowzesh Hasan

Doctoral Dissertations

The electrical characterization on two-dimensional carbon-based graphene and nanodiamond materials was performed to improve charge transport properties for the label-free electrical biosensors. The charge transport in solution-gated graphene devices is affected by the impurities and disorders of the underlying dielectric interface and its interaction with the electrolytes. Advancement in field-effect ion sensing by introducing a dielectric isomorph, hexagonal boron nitride between graphene and silicon dioxide of a solution-gated graphene field-effect transistor was investigated. Increased transconductance due to increased charge carrier mobility is accompanied with larger ionic sensitivity. These findings define a standard to construct future graphene devices for biosensing and …

Nanoparticle Catalytic Enhancement Of Carbon Dioxide Reforming Of Methane For Hydrogen Production, Nicholas Groden

Doctoral Dissertations

The U.S. produces 5559.6 million metric tons of carbon dioxide annually, of which 21% is produced by industrial processes. Steam reforming, an industrial process that accounts for 95% of all hydrogen production in industry, produces 134.5 million metric tons of carbon dioxide or around 11% of the total carbon dioxide produced by industry. This carbon dioxide is then either emitted or goes through a sequestration process that accounts for 75% of the plant's operational costs. An alternative reaction to steam reforming is dry reforming, which utilizes carbon dioxide rather than emitting it and can be used in conjunction with current …

Metal Segregation During The Solidification Of Titanium-Aluminum Alloys For 3d Printing Applications, Jwala Parajuli

Master's Theses

Titanium-Aluminum alloys are one of the widely used alloys in multiple engineering applications. They are highly preferred in Selective Laser Melting (SLM) processes due to their low density, high melting temperature, and good strength. Segregation occurs during the solidification of most alloys and produces a non-uniform distribution of atoms. In SLM, segregation may depict the type of adhesion between the two deposited interfacial layers and the strength between the interphase between an already solidified layer and a new one, and overall, the quality of the printed part. In order to avoid segregation, the understanding of the segregation behavior at atomistic …

Studies On The Electrical Transport Properties Of Carbon Nanotube Composites, Taylor Warren Tarlton

Doctoral Dissertations

This work presents a probabilistic approach to model the electrical transport properties of carbon nanotube composite materials. A pseudo-random generation method is presented with the ability to generate 3-D samples with a variety of different configurations. Periodic boundary conditions are employed in the directions perpendicular to transport to minimize edge effects. Simulations produce values for drift velocity, carrier mobility, and conductivity in samples that account for geometrical features resembling those found in the lab. All results show an excellent agreement to the well-known power law characteristic of percolation processes, which is used to compare across simulations. The effect of sample …

Experimental And Numerical Evaluation Of A New Composite Pressure Pipe For A Trenchless Rehabilitation Technology, Xuanchen Yen

Doctoral Dissertations

The information presented in this dissertation is based on research work conducted at Trenchless Technology Center (TTC) at Louisiana Tech University. This work was performed through a contract with China University of Geoscience (CUG) for a gas company. China's gas pipelines need replacement or rehabilitation after 15 to 30 years of service. China's gas industry is looking for suitable techniques to transfer into their market.

When compared to conventional excavation pipeline renewal or replacement methods, there are obvious advantages of TRT for gas pipelines that can impact the triple bottom-line of economic, social and environmental benefits. An introduction of TRT …

Clay Nanotube Composites For Antibacterial Nanostructured Coatings, Christen J. Boyer

Doctoral Dissertations

A surging demand for the development of new antimicrobial nanomaterials exists due to the frequency of medical device-associated infections and the transfer of pathogens from highly touched objects. Naturally occurring halloysite clay nanotubes (HNTs) have shown to be ideal particles for polymer reinforcement, time-release drug delivery, nano-reactor synthesis, and as substrate material for nanostructured coatings.

This research demonstrates the feasibility of a novel method for coating HNTs with metals for antibacterial applications. The first ever ability to coat HNTs through electrolysis was developed for customizable and multi-functional antibacterial nanoparticle platforms. HNTs were investigated as substrate for the deposition of copper …

Multi-Scale Characterization Of Nanostructured Sodium Aluminum Hydride, Shathabish Narasegowda

Doctoral Dissertations

Complex metal hydrides are the most promising candidate materials for onboard hydrogen storage. The practicality of this class of materials is counter-poised on three critical attributes: reversible hydrogen storage capacity, high hydrogen uptake/release kinetics, and favorable hydrogen uptake/release thermodynamics. While a majority of modern metallic hydrides that are being considered are those that meet the criteria of high theoretical storage capacity, the challenges lie in addressing poor kinetics, thermodynamics, and reversibility. One emerging strategy to resolve these issues is via nanostructuring or nano-confinement of complex hydrides. By down-sizing and scaffolding them to retain their nano-dimensions, these materials are expected to …

Introducing Porous Silicon As A Sacrificial Material To Obtain Cavities In Substrate Of Soi Wafers And A Getter Material For Mems Devices, Wajihuddin Mohammad

Doctoral Dissertations

Microelectromechanical system (MEMS) resonators have been a subject of research for more than four decades. The reason is the huge potential they possess for frequency applications. The use of a MEMS resonator as the timing element has an experimental history and huge progress has been made in this direction. Vacuum encapsulated MEMS resonators are required for high precision frequency control. Hence, a device with a high quality factor and durability is needed. In this effort, a new process for producing a cavity in the substrate of Silicon on insulator (SOI) MEMS devices and augmenting it with a getter using porous …

Development Of Approximating Functions To Model And Predict The Properties Of Fresh And Hardened Fly Ash-Based Geopolymer Concrete, Eleazar Ivan Diaz Loya

Doctoral Dissertations

The manuscript presented herein is based on the investigation of the mechanical properties of fly ash-based geopolymer concrete and their link to fly ash (FA) characteristics. A database of 32 FA samples was created. Each FA sample was analyzed in terms of chemical composition, crystallographic properties and particle size distribution. The mechanical performance of geopolymer concrete (GPC) made from each FA sample was evaluated in terms of density, setting time, compressive and flexural strength, static elastic modulus and Poisson's ratio. It is worth mentioning that the author has already published preliminary results of this study (Diaz and Allouche, 2010; Diaz …

Analysis Of Conjugated Polymer Nanotubules Formed By Template Wetting Nanofabrication, Steven D. Bearden Jr.

Doctoral Dissertations

Semiconducting and optoelectric conjugated polymers have potential in micro and nano-electronic applications. Their widely tunable physical conformations and orientations make these polymers ideal material for engineering small scale devices. The polymers have been incorporated into several electronic devices including light-emitting diodes, solar cells, and field-effect transistors. Widespread adoption of these materials will not be a reality until the issues of poor device performance, short lifespans, and device degradation are resolved.

Nanostructures have been demonstrated to have improvements in molecular ordering and electronic transport. In the work presented here, tubular nanostructures of conjugated polymers fabricated by the template wetting nanofabrication process …

Computational Study Of Pristine And Titanium-Doped Sodium Alanates For Hydrogen Storage Applications, Gopi Krishna Phani Dathar

Doctoral Dissertations

The emphasis of this research is to study and elucidate the underlying mechanisms of reversible hydrogen storage in pristine and Ti-doped sodium aluminum hydrides using molecular modeling techniques. An early breakthrough in using complex metal hydrides as hydrogen storage materials is from the research on sodium alanates by Bogdanovic et al., in 1997 reporting reversible hydrogen storage is possible at moderate temperatures and pressures in transition metal doped sodium alanates. Anton reported titanium salts as the best catalysts compared to all other transition metal salts from his further research on transition metal doped sodium alanates. However, a few questions remained …

A Computational Study On Novel Carbon-Based Lithium Materials For Hydrogen Storage And The Role Of Carbon In Destabilizing Complex Metal Hydrides, Mohammed Minhaj Ghouri

Doctoral Dissertations

One of the major impediments in the way of the realization of hydrogen economy is the storage of hydrogen gas. This involves both the storage for stationary applications as well as that of storage onboard vehicles for transportation applications. For obvious reasons, the system targets for the automotive applications are more stringent. There are many approaches which are still being researched for the storage of hydrogen for vehicular applications. Among them are the high pressure storage of hydrogen gas and the storing of liquid hydrogen in super insulated cryogenic cylinders. While both of them have been demonstrated practically, the high …

Rational Design And Investigation Of Polypeptide Multilayer Films And Capsules, Ling Zhang

Doctoral Dissertations

Three major concerns in the science of materials today are control over structure and function at the molecular level, biodegradability, and scalability of production. Polymeric materials, notably polyelectrolyte multilayer films, have shown considerable promise in all these areas, and for rational development of multifunctionality. Polypeptides constitute an especially interesting class of polyelectrolyte, given their inherent biodegradability, means of control over structure, methods of large-scale synthesis, and ability to encode biological information. Relatively little is known, however, about polypeptide multilayer films, despite recent advances in the general area.

In this dissertation, ten heteropolypeptides were designed and synthesized by Fmoc chemistry. These …

Growth And Behavior Of Chondrocytes On Nano Engineered Surfaces And Construction Of Micropatterned Co-Culture Platforms Using Layer-By-Layer Platforms Using Layer -By -Layer Assembly Lift-Off Method, Jameel Shaik

Doctoral Dissertations

Several approaches such as self-assembled monolayers and layer-by-layer assembled multilayer films are being used as tools to study the interactions of cells with biomaterials in vitro. In this study, the layer-by-layer assembly approach was used to create monolayer, bilayer, trilayer, five, ten and twenty-bilayer beds of eleven different biomaterials. The various biomaterials used were poly(styrene-sulfonate), fibronectin, poly-L-lysine, poly-D-lysine, laminin, bovine serum albumin, chondroitin sulfate, poly(ethyleneimine), polyethylene glycol amine, collagen and poly(dimethyldiallyl-ammonium chloride) with unmodified tissue-culture polystyrene as standard control. Three different cell lines—primary bovine articular chondrocytes, and two secondary cell lines, human chondrosarcoma cells and canine chondrocytes were used in …

A Finite Difference Method For Studying Thermal Deformation In Two-Dimensional Micro Scale Metal Thin Films Exposed To Ultrashort Pulsed Lasers, Haojie Wang

Doctoral Dissertations

Ultrashort-pulsed lasers have been attracting worldwide interest in science and engineering because the lasers with pulse durations on the order of sub-picoseconds to femtoseconds possess capabilities in limiting the undesirable spread of the thermal process zone in a heated sample during material processing at the microscale. Prevention of thermal damage is an important factor for success of ultrashort-pulsed lasers in real applications. The thermal damage induced by ultrashort pulses is intrinsically different from that induced by long-pulse or continuous lasers. It occurs after the heating pulse is over and involves the shattering of thin metal layers (without a clear signature …

Nanodot-Based Organic Memory Devices, Zhengchun Liu

Doctoral Dissertations

In this study, resistor-type, diode-type, and transistor-type organic memory devices were investigated, aiming at the low-cost plastic integrated circuit applications. A series of solution-processing techniques including spin-coating, inkjet printing, and self-assembly were employed to fabricate these devices.

The organic resistive memory device is based on a novel molecular complex film composed of tetracyanoquinodimethane (TCNQ) and a soluble methanofullerene derivative [6,6]-phenyl C61-butyric acid methyl ester (PCBM). It has an Al/molecules/Al sandwich structure. The molecular layer was formed by spin-coating technique instead of expensive vacuum deposition method. The current-voltage characteristics show that the device switches from the initial 'low' conduction state to …

Integration Of Micro Nano And Bio Technologies With Layer -By -Layer Self -Assembly, Dinesh Shankar Kommireddy

Doctoral Dissertations

In the past decade, layer-by-layer (LbL) nanoassembly has been used as a tool for immobilization and surface modification of materials with applications in biology and physical sciences. Often, in such applications, LbL assembly is integrated with various techniques to form functional surface coatings and immobilized matrices. In this work, integration of LbL with microfabrication and microfluidics, and tissue engineering are explored. In an effort to integrate microfabrication with LbL nanoassembly, microchannels were fabricated using soft-lithography and the surface of these channels was used for the immobilization of materials using LbL and laminar flow patterning. Synthesis of poly(dimethyldiallyl ammonium chloride)/poly(styrene sulfonate) …

Development Of Palladium Nanowires, Chuanding Cheng

Doctoral Dissertations

Inherent limitations of traditional lithography have prompted the search for means of achieving self-assembly of nano-scale structures and networks for the next generation of electronic and photonic devices. The nanowire, the basic building block of a nanocircuit, has recently become the focus of intense research. Reports on nanowire synthesis and assembly have appeared in the scientific literature, which include Vapor-Liquid-Solid mechanism, template-based electrochemical fabrication, solvothermal or wet chemistry, and assembly by fluid alignment or microchannel networks. An ideal approach for practical application of nanowires would circumvent technical and economic constraints of templating. Here we report on the self-assembly of highly-ordered …

A Fe-Fd Hybrid Scheme For Solving Parabolic Two-Step Micro Heat Transport Equations In Irregularly Shaped Three Dimensional Double -Layered Thin Films Exposed To Ultrashort -Pulse Lasers, Brian R. Barron

Doctoral Dissertations

Multi-layer thin films are important components in many micro-electronic devices. These films are often used when a single film layer is insufficient to meet devices specifications. The continued reduction in component size has the side effect of increasing the thermal stress on these films and consequently the devices they comprise. Understanding the transfer of heat-energy at the micro-scale is important for thermal processing using a pulse-laser. Often, micro-voids may be found in processed devices. This is due to thermal expansion. Such defects may cause an amplification of neighboring defects resulting in severe damage and consequently the failure of the device. …

Layer-By-Layer Self -Assembly For Enzyme And Dna Encapsulation And Delivery, Amish Patel

Doctoral Dissertations

Thin wall microcapsules were formed via Layer-by-Layer Self-Assembly of alternate adsorption of oppositely charged polyelectrolyte on microcores. After the core dissolution, empty polymeric shells with 20–25 nm thick walls were obtained. These microcapsules were loaded with Myoglobin, Hemoglobin and Glucose Oxidase by opening capsule pores at low pH and closing them at higher pH. The native structure of the enzyme was not affected due to different treatments. Biocompatible nanoshells were also prepared for encasing DNA. Using the same Layer-by-Layer Self-Assembly approach nanoparticle were constructed containing DNA as one of the layers. The nanoparticles of different architecture were used to deliver …

Computational Approaches To The Design And Analysis Of Stability Of Polypeptide Multilayer Thin Films, Bin Zheng

Doctoral Dissertations

The focus of this research is the development of computational approaches to understanding the physical basis of layer-by-layer assembly (LBL), a key methodology of nanomanufacturing. The results provided detailed information on structure which cannot be obtained directly by experiments.

The model systems chosen for study are polypeptide chains. Reasons for this are that polypeptides are no less polyelectrolytes than the more usual polyions, and one can control the primary structure of a polypeptide on a residue-by-residue basis using modern synthetic methods. Moreover, as peptides constitute one of the four major classes of biological macromolecules, research in this direction is expected …

Fabrication, Characterization, And Modeling Of Organic Capacitors, Schottky Diodes, And Field Effect Transistors, Mo Zhu

Doctoral Dissertations

The objectives of this project are to fabricate, characterize, and model organic microelectronic devices by traditional lithography techniques and Technology Computer Aided Design (TCAD).

Organic microelectronics is becoming a promising field due to its number of advantages in low-cost fabrication for large area substrates. There have been growing studies in organic electronics and optoelectronics. In this project, several organic microelectronic devices are studied with the aid of experimentation and numerical modeling.

Organic metal-insulator-metal (MIM) and metal-insulator-semiconductor (MIS) capacitors consisting of insulating polymer poly(4-vinylphenol) (PVP) have been fabricated by spin-coating, photo lithography, and reactive ion etching techniques. Based on the fabricated …