Engineering Commons^™

Production And Characterization Of Composite Nano/Micro Sized Particles By Rapid Expansion Of Supercritical Solutions (Ress) Co-Precipitation, Beidi He

Dissertations

Nanoscale composites of hexahydro-1, 3, 5-trinitro-1, 3, 5-triazine (RDX) and polymer binders were produced by co-precipitation using rapid expansion of supercritical solutions (RESS). The binders used in this study are poly (vinylidene fluoride-co-hexafluoropropylene) (VDF-HFP22), polystyrene (PS) and 7-amino-4-methyl coumarin (AMC). The RDX/VDF-HFP22 and RDX/PS co-precipitated nanoparticles were characterized by Field Emission Scanning Electron Microscopy (FE-SEM) and Transmission Electron Microscopy (TEM). The average size of produced nanoparticles is ca. 100 nm. TEM analysis of RDX/PS nano-composite shows a core-shell structure with RDX as the core material and the shell consisting of the polymeric binder. X-ray Powder Diffraction (XRPD) analysis …

New Screening Methodology For Selection Of Polymeric Materials For Transdermal Drug Delivery Devices, Roberto P. Falcone

Dissertations

As medical advances extend the human lifespan, the level of chronic illnesses will increase and thus straining the needs of the health care system that, as a result, governments will need to balance expenses without upsetting national budgets.

Therefore, the selection of a precise and affordable drug delivery technology is seen as the most practical solution for governments, health care professionals, and consumers.

Transdermal drug delivery patches (TDDP) are one of the best economical technologies that are favored by pharmaceutical companies and physicians alike because it offers fewer complications when compared to other delivery technologies. TDDP provides increased efficiency, safety …

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 …

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 …

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 …

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 …

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 …

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 …

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 …

Polymeric Nitrogen By Plasma Enhanced Chemical Vapor Deposition, El Mostafa Benchafia

Dissertations

With the urgent need for new environmentally-friendly energetic materials, the field of polymeric nitrogen, predicted to be a high energy density energetic, is now at a critical stage in its development. In spite of extensive first principles calculations regarding the existence and stability of different polymeric nitrogen structures, their successful syntheses have been rare. This dissertation describes the first detailed study of a plasma-enhanced chemical vapor deposition (PECVD) approach to the synthesis of polymeric nitrogen. PECVD provides non-equilibrium conditions known to produce high pressure-temperature phases. Molecular nitrogen mixed with hydrogen and argon is used as the gas phase precursor to …

Electronic, Optical, Mechanical And Thermoelectric Properties Of Graphene, Sarang Vilas Muley

Dissertations

Graphene, a two-dimensional allotrope of graphite with sp² bonded carbon atoms, is arranged in honeycomb structure. Its quasi one-dimensional form is graphene nanoribbon (GNR). Graphene related materials have been found to display excellent electronic, chemical, mechanical properties along with uniquely high thermal conductivity, electrical conductivity and high optical transparency. With excellent electrical characteristics such as high carrier transport properties, quantum Hall effect at room temperature and unusual magnetic properties, graphene has applications in optoelectronic devices.

Electronically, graphene is a zero bandgap semiconductor making it essential to tailor its structure for obtaining specific band structure. Narrow GNRs are known to …

Inkjet Printing Multifunctional Chromatic Sensors And Chromism Study, Aide Wu

Dissertations

The thermochromism and chemochromism of polydiacetylene (PDAs) and PDA/ZnO nano composites have been systematically studied by attentuated total reflection (ATR)- Fourier transform infrared (FTIR), temperature-dependent Raman, colorimetric (using optical densitometry) and differential scanning calorimetry (DSC). Reversibility of PDAs has been enhanced by the formation of chelation between the carboxylic groups on side chain of diacetylene and Zn ion. The thermochromatic transition temperature increases with the concentration of ZnO.

Thin films of polydiacetylene (PDAs) and PDA/ZnO nanocomposites have been successfully fabricated by inkjet printing both solution type and suspension type ink. Results suggest that PDA monomers are well-aligned and closely packed …

Continuous Polymer Coating Of Host Particles By Hollow Fiber-Based Crystallizers, Dengyue Chen

Dissertations

Currently, no technique is available to continuously film coat nano-sized drug particles with a polymer to produce large amounts of free-flowing coated particles. In this work, Eudragit RL 100 and Poly (D, L-lactide-co-glycolide) (PLGA) are chosen as the coating polymers; Cosmo 55 (550 nm silica particles), Aerosi l 200 (hydrophilic 12 nm silica), Aerosil R974 (hydrophobic 12 nm silica) and Griseofulvin (10 lam drug particles) are chosen as the host particles. Two novel crystal l izers are designed and fabricated to continuously coat the host particles with different polymers: solid hollow fiber cooling crystallizer (SH FCC) and porous hollow fiber …