Materials Science and Engineering Commons^™

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 …

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 …

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 …

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.

Characterization Of Neural Ion Regulation Dysfunction During Insult And Evaluation Of Micro-Opioid Receptor Activation During Simulated Ischemia In The Pre-Botzinger Complex, Kyle F. Dobiszewski

Dissertations

The health and vitality of brain tissue is dependent upon the cells' abilities to maintain ionic homeostasis across their plasma membranes. Even slight alterations in intracellular or extracellular can have a devastating effect on excitability and neural vitality. This thesis investigates several concepts related to ion flux. First, it investigates how ion flux affects characterization of brain tissue by dielectric spectroscopy and what can be done to overcome that effect. Second, it investigates how ion flux can be used to describe the state of health of the tissue. Finally, it investigates if pharmacological intervention can attenuate some of the deleterious …

Influence Of Sinx/Si Interface States On Si Solar Cells, Santosh Sahoo

Dissertations

Impact of the SiN_x/n⁺-Si interface on silicon solar cell performance was investigated, where SiN_x is used as a passivation layer. Significant shifts in capacitance, conductance and leakage current characteristics were observed for metal/SiN:H/n⁺-Si MOS capacitor when it was subjected to a constant voltage stress (CVS) of +10V at room temperature. The interface trap density (D_it) across the SiN:H/n⁺-Si interface increased from 6.3 x 10⁹ to 7.5 x 10⁹ cm^-2 eV^-1 after a 500-second stress whereas the n⁺/p junction diode remained unaffected by the …

Synthesis And Characterization Of Novel Boron-Based Nanostructures And Composites, Rajen B. Patel

Dissertations

A number of nanomaterials have been synthesized by using a method that has been previously utilized to make pure boron nanostructures through the addition of different reactant gases to the process. This method was pioneered by Iqbal-Liu and will be referred to as the IL method in this dissertation. The IL method successfully created boron nanowires, boron nanoflakes, and boron nanotubes. In this dissertation, by adding methane, hydrogen sulfide, and ammonia to the process, an entire family of nanomaterials is prepared. These include nanowires, nano-heterostructures, and thin nanoplatelets of a variety of elemental compositions. These materials can be integrated with …

The Effects Of Rapid Stretch Injury On Rat Neocortical Cultures, George Constandinos Magou

Dissertations

Several key biological mechanisms of traumatic injury to axons have been elucidated using in vitro stretch injury models. These models, however, are based on the experimentation of single cultures keeping productivity slow. Indeed, low yield has hindered important and well founded investigations requiring high throughput methods such as proteomic analyses. To meet this need, a multi-well high throughput injury device is engineered to accelerate and accommodate the next generation of traumatic brain injury research. This modular system stretch-injures neuronal cultures in either a 24-well culture plate format or six individual wells simultaneously. Custom software control allows the user to accurately …

Foaming Of Amorphous Drug Delivery Systems Prepared By Hot Melt Mixing And Extrusion, Graciela Terife

Dissertations

Currently there is considerable interest from both academe and pharmaceutical industry in exploring foaming processes and their products in drug delivery applications. However, there is still little knowledge of the impact of the morphology of the foamed structures on the performance of drug products in spite of some publications in this area. Therefore, the main objective of this dissertation is to gain a fundamental understanding of the correlation between foam morphology and performance of amorphous drug delivery systems, which are comprised of an Active Pharmaceutical Ingredient (API) and Polymer excipient.

The Hot Melt Extrusion (HME) process is used to compound …

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 …

The Incorporation Of Electrohydrodynamics And Other Modifications Into A Dry Spinning Model To Develop A Theoretical Framework For Electrospinning, Yuki Imura

Dissertations

The objective of this research was the development of a mathematical model of the electrospinning process using dry spinning modeling principles as a basis. This model is directed at the identification of parameters which influence final fiber characteristics, e.g., solvent concentration, temperature, spin line tension, and electric field. Preliminary computer simulations were performed; however, the generated data was inconclusive and was determined to be due in part to the complexity of the modeled system and the subsequent computational difficulties encountered. Although a comprehensive computational model of the electrospinning process has not yet been demonstrated, the theoretical development that was undertaken …

Synthesis, Molecular And Solid State Structures, And Magnetic Properties Of Sandwich Lanthanide Phthalocyanines Lacking C-H Bonds, Wycliffe A. Graham

Dissertations

A new class of sandwich phthalocyanine (Pc) compounds without C-H bonds was synthesized and characterized. They are the bis[octakis(perfluoro i-C₃F₇) octakis(perfluoro)phthalocyaninato(2−)]M(III) complexes, formulated as (F₆₄Pc)₂MH, M = Tb, Dy, Lu, Y. Single molecular magnetic (SMM) behavior in the (F₆₄Pc)₂TbH and (F₆₄Pc)₂DyH complexes was confirmed through slowed relaxation response of their magnetization in an applied time varying magnetic field during alternating current (AC) magnetic testing in the range 2 - 50 K. The energy barrier to magnetic reversal, Δ = 215 cm^-1 and …

Rational Design Of Hydrogen-Free Catalytic Active Sites, Andrei Ioan Loas

Dissertations

Materials that are organic-based and exhibit oxidative catalytic activity, including free-radical pathways, while being refractory to the activated oxygen species are not known. The synthesis of several classes of such materials, their electronic and structural characterizations as well as catalytic properties are reported. Their rational molecular design and biologically inspired reactivity are based on enzymatic active sites, which are reengineered into robust metal-organic fluoroalkylated scaffolds that, for the first time, exhibit structural asymmetry and tunable π-π interactions both in solution and solid state. In these complexes, labile C-H bonds are replaced with chemically and thermally resistant C-F bonds to create …

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 …

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) …

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 …

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 …

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, …

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 …