Materials Science and Engineering Commons^™

Computational Studies Of Electronic Structure Of Doped Graphene, Yan Chu

Theses

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

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

Theses

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

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

Simulation Of Electronic And Optical Properties Of Graphene, Biao Leng

Theses

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

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

Theses

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

Optical Properties Of Black Silicon - An Analysis, Suramya Sekhri

Theses

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

Ultracapacitors For Off Grid Wind Power Systems, Hans Tanis

Theses

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

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

Theses

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

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

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

Theses

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

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

Theses

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

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

Theses

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

Thermal Properties Of Graphene, Vishal Vijay Nakhate

Theses

The two-dimensional (2D) monolayer structure of carbon atoms were initially considered as unstable. The 2D materials have recently been discovered and many researchers have started analyzing these materials. Graphene, a two-dimensional allotrope of graphite with sp2 bonded carbon atoms, is arranged in honeycomb structure. Graphene has excellent thermal conductivity and can be considered as a potential material for applications in the electronics industry where heating of materials is a serious concern.

In this study, thermal properties of p and n doped graphene nanosheets and nanoribbons are studied as function of percentage composition of the dopants and the direction of dissipation …

Preparation And Characterization Of Copper-Doped And Silver-Doped Titanium Dioxide Nano-Catalysts For Photocatalytic Applications, Haya Abdel Ra'ouf Ahmed

Theses

The goal of this work was to improve the performance of TiO₂ nanomaterials by increasing their optical activities by shifting the onset of the response from the UV to the visible-light region. Among the several ways to achieve this goal, doping TiO₂ nanomaterials with other elements (e.g. metals) was selected to narrow the band gap and enhance the optical properties of TiO₂ nanomaterials. In this work, we have prepared Cu-doped TiO₂ nano-catalysts, characterized them and studied their properties, and the optical ones in particular. The Ag-doped TiO₂ catalyst was prepared by the sol-gel method while …

Effect Of Temperature On Tunneling And Quantum Efficiency In Cigs Solar Cells, Sizhan Liu

Theses

Utilizing the two-band approximation and Wentzel-Kramers-B ri l l oui n (WKB) approximation, by including the temperature-dependent effective masses and nonparabolicity effects, an investigation of the temperature dependent band-to-band tunneling process is discussed. In comparison with the parabolic approximation and non- parabolic approximation, the tunneling probability is strongly dependent on the non-parabolicity factor. The temperature dependence of the energy band gap, electron effective mass and light hole effective mass is investigated. The tunneling current density function is derived by a series representation of the incomplete gamma function with non-parabolic effect and its variation at low temperature is also investigated. When …

Analysis Of Transport Properties In A Zaz Graphene Nanoribbon Junction Using Various Dopants, Natasha Parikh

Theses

A 12 atom wide ZAZ Graphene Junction was simulated and its transport properties were analyzed. I-V curves, calculated by nonequilibrium Greens function method combined with the density functional theory under external bias, showed varying semiconducting characteristics. Further, the width of the junction also showed significant effects in the determination of the semiconducting nature. A theoretical study was performed on the semiconducting characteristics by analyzing the I-V curve and transport coefficients in the junction.

Optical And Mechanical Investigation Of Inas /Gaas Quantum Dots Solar Cells And Inas Nanowires For The Application Of Photovoltaic Device, Yushuai Dai

Theses

Self-assembled quantum dots (QDs) and nanowires (NWs) are currently the subjects of extensive study due to their promising applications in optoelectronic devices. In order to enhance understanding of the short circuit current improvement in InAs/GaAs quantum dots solar cell (QDSC), the mechanisms of carrier escape by thermal activation and tunneling from InAs quantum dots (QDs) confinements in InAs/GaAs QDSCs are investigated. The fitted activation energy of electrons from temperature dependent photoluminescence (TDPL) is 114 meV. Using this fitted activation energy, calculated thermal escape time and tunneling time of electrons from the ground state of the QDs are 10-12 seconds and …

Measurement Of Gas Flow Through Porous Structures Using Thz Spectroscopy, Yihui Wang

Theses

Comparing THz transmission through a sample with the transmission through free-space allows one to calculate the THz absorbance of a sample. Previous studies have focused on using THz absorbance to measure the diffusion of liquid through materials. In this study, the ability of THz spectroscopy to measure the flow of gas in a porous material, packaging foam, is investigated. Specifically, Terahertz spectroscopy from 0.5 to 0.7 THz is used to measure the THz absorption of 1, 1 -difluoroethane. Several experiments are performed to test the ability of THz spectroscopy to measure the flow of gas in a porous material: (1) …

Current Measurements In Electrospinning, Clinton K. Lien

Theses

Electrospinning provides an economical method of producing nanofibers. The current carried by the main spinning jet is found to be one of the factors in determining the diameter of the fiber product. However, current sources such as the corona discharge and secondary jets will lead to a systematic overestimation of the actual current value.

In this research, experiments with different configurations are set up to investigate the influence of various parameters on the measured current. It is noticed that the measured current is nearly independent on the flow rate of the solution and the external cover. A large amount of …

Role Of Materials & Design On Performance Of Baseball Bats, Kim Benson-Worth

Theses

Baseball bat safety has become an increasing area of interest with more than 19 million people in the United States alone participating in this sport. An increase in injuries resulting from bat injuries has brought the performance of the bats into question. A review of several studies focusing on the effects of the material properties of various baseball bats designs were examined. From this review it is evident that player and spectator safety greatly rely on proper baseball bat design. There was a 30% reduction in the Multi-Piece Failures (MPF) of wooden bats once the requirement of a Slope of …

Study Of Poly (L-Lactic Acid)/Poly (D-Lactic Acid) Stereocomplex As Nucleating Agent For Poly (L- Lactic Acid) Crystallization, Yuan Lao

Theses

Poly (lactic acid) (PLA) is a biodegradable polymer with good renewability and processability. However, it has some drawbacks. The Poly (lactic acid) (PLA) stereocomplex formed via the interaction between optical isomers Poly (L-lactic acid) (PLLA) and Poly (D-lactic acid) (PDLA), provides improvements on PLA thermomechanical properties. To investigate the nucleating effect brought by the PLA stereocomplex, samples of PLLA blended with different content of PDLA are prepared by the solution casting method. With different cooling rates (5, 15, 25 °C/min), DSC non-isothermal crystallization experiments are performed. The results suggest that in the presence of the stereocomplex, the PLLA crystallization temperatures …

Nanocluster Production For Solar Cell Applications, Haila M Aldosari

Theses

No abstract provided.

Preparation, Characterization And Catalytic Activity Study Of Transition Metal Doped Porous Γ-Alumina, Seham Nasser Al Hadrami

Theses

Transition-metal ions -doped γ-alumina composites with various dopant concentrations (Cr³⁺, Fe³⁺, Ce³⁺, Zn²⁺, Mn²⁺, V²⁺ and Cu²⁺) were prepared by straightforward tempIate-free sol-gel method. They were characterized by XRD, FTIR, SEM, NMR and N₂ adsorption-desorption isotherm technique. The presence of dopant metal ions, generally, enhanced the gel formation and their behavior was dependent on the nature of the metal ion and its concentration. Certain ions, especially Fe³⁺, resulted in rapid formation of a transparent gel upon hydro lysis. The presence of the acetylacetonate …

Effect Of Microwave Heating On The Migration Of Additives From Ps, Pp And Pet Container Into Food Simulants, Ruoyin Cai

Theses

Microwave food packaging has become a tremendous element in the food manufacturing process. The purpose of any food packaging regulations concerned with the safety of the food is to control and limit the migration of substances from the packaging into the food. The main objective of this thesis is to test three different microwaving packaging materials that are the most common material in the market, viz. polystyrene (PS), polypropylene (PP), and polyethylene terephthalate (PET), migrated into four food simulant solutions. Four different simulant solutions were used based on the food type and FDA recommendations and regulations. These food simulants include …

Magnetic Targeted Drug Delivery System In Gene Therapy, Weilong Lu

Theses

Drug delivery system is a method to transport the drug of the required amount accurately to the targeted diseased part. Recently, the concept of Magnetic Targeted Drug Delivery System (MTDDS), based upon magnetic particles under the action of an external magnetic field, exhibits considerable potential for a wide range of medical applications. Gene therapy is the insertion of genes into an individual's cells and tissues to treat diseases. As the recombinant virus vector has many limits and problems, more studies turn to the nonvirus vectors, which have transfection efficiency and low cytotoxicity. PLLA(poly(L lactic acid)) can be biodegradable and has …

Magnetic Iron Oxide Nanoparticles: Synthesis, Characteristics, Magnetic Behavior, And Biomedical Applications, Chengyin Fu

Theses

Magnetic iron oxide nanoparticles are attracting increasing attention due to their interesting properties that can be applied in a great number of applications such as catalysis and biomedicine. This thesis focuses on the synthesis, characteristics, and biomedical applications of iron oxide nanoparticles. The two most common iron oxides, including magnetite and maghemite, are discussed in this thesis.

For most of their applications, the magnetic behavior of iron oxide nanoparticles in a fluid is very important, especially, the high gradient magnetic separation of the particles from a nonmagnetic liquid medium, such as blood in the human body. A 2D model, which …

Simulation Of Polymer Solar Cell Characteristics By Amps-1d, Lu Zhang

Theses

Simulation of polymer solar cell characteristics is presented in this study. The solar cells are made of materials such as the following: Poly (3-hexylthiophene): [6, 6]-phenyl C61- butyric acid methylester (P3HT: PCBM) and poly[2,1,3-benzothiadiazole-4,7-diyl[4,4- bis(2-ethylhexyl)-4H-cyclopenta[2,1-b:3,4-b']dithiophene-2,6-diyl]]: [6, 6]-phenyl C₆₁- butyric acid methylester (PCPDTBT: PCBM) are used as active layer materials. Analysis of Microelectronic and Photonic Structures One Dimension (AMPS-1D) is a computer simulation tool for solar cell device characteristics. The first part of this study focuses on the performance and comparison of current-voltage (I-V) simulations of indium oxide (In₂O₃) and tin oxide (SnO₂) …

Microencapsulation Of The Non-Steroidal Anti-Inflammatory Drugs Into Biodegradable Polymers Using Supercritical Fluid Technology, Safaa Mohamad Al Mahdi Ali Yousif

Theses

Osteoarthritis is a disease that attacks human bones especially in older people and usually nonsteroidal anti-inflammatory drugs (NSAIDS) are being prescribed for patients with Osteoarthritis. These kinds of drugs usually have low aqueous solubility and in order to have their therapeutic effects, their solubility should be enhanced. The purpose of this study was to find solution for this problem and one way to do that is to reduce the particle size by forming micro particles. In this project, one of these types of drugs ibuprofen (isobutyl-propanoicphenolic Acid) was encapsulated into a polymer (PVP polyvinylpyrrolidone) using supercritical fluid technology (Supercritical CO …

Hydrogen Storage In Pt/Carbon Nanotube Sheets, An-Yu Ma

Theses

Three types of self-assembled carbon nanotube (CNT) sheets, for example, carboxylic functionalized multi-walled CNTs (MWNTs-COOH), pure multi-walled CNTs (MWNTs), and pure single-walled CNTs (SWNTs), were prepared as substrates by ambient environment vacuum filtration of suspensions of the nanotubes. To enhance hydrogen storage on the CNTs, platinum particles were deposited on the three types of CNT sheets using two processes: electrodeposition (ED) using a DC power source and electrochemical deposition under cyclic voltammetry (CV). To verify platinum deposition on the surface of the CNT sheets, a Scanning Electron Microscope (SEM) was used to obtain images, and Energy Dispersive X-ray (EDX) spectroscopy …

Fiber-Reinforced Calcium Sulfate Bone Cement Composites With Enhanced Bioactivity, Mechanical Properties And Controlled Biodegradability, Nuha Fathi Hussien

Theses

Hard tissues are natural composites of inorganic and organic components. The inorganic component is a basic Calcium phosphate; known as hydroxyapatite (HAp) while the organic is a natural polymer; known as collagen. The interlocking between the collagen nanofibers and the Hap nanocrystals growing on them offers the known unique mechanical stability of hard tissues. In case of partial fractures; bone or dental cements are often used. Cements such as polymethylmethacrylate (PMMA) has been long used in this regard. However, this polymer is classified as a bio inert material that can be accepted by the human body without having a positive …

Interfacially Polymerized Thin Film Composite Membranes On Microporous Polypropylene Supports For Reverse Osmosis Desalination, Chao Li

Theses

The important technique of interfacial polymerization (IP) is used to fabricate thin film composite (TFC) membranes. In experiments here, microporous polypropylene (PP) flat film membranes were used as a support for fabricating TFC membranes for reverse osmosis by the IP technique. Substantial chemical, pH, and solvent resistance is provided by porous polypropylene membranes. Therefore, it is reasonable to choose porous polypropylene membranes as supports to fabricate TFC membranes for reverse osmosis.

The external and the pore surfaces of polypropylene flat film membrane were hydrophilized first by pre-wetting with acetone, then oxidized with chromic acid solution kept at 65°C. Next, the …

Stress Corrosion Cracking Of Stainless Steels Used In Manufacturing Brine Circulating Pumps Used In Desalination Plants., Ahmed Ibrahim Ahmed Al-Joboury

Theses

In earlier works, characterization and stress corrosion cracking of casings of brine recirculation pumps used in desalination plants was investigated. These casings, which were manufactured from two types of Ni resist ductile irons, were reported to show different service lives. Material selection of casings is believed to be one of possible factors to extend the service lives of these pumps. Two types of stainless steels; UNS S31603 and UNS S32750 were recommended as substitutes to Ni resist ductile irons. In this work, mechanical, metallurgical, electrochemical and stress corrosion cracking (SCC) tests were conducted on as received samples, made from these …