Doctor of Philosophy (Ph.D.), University of Dayton, 2019, Materials Engineering

In this study, multiple approaches were explored for building advanced nanocomposite sensors intended for use in fiber reinforced organic matrix composite structures. One expected application of such technology is sensing of chemical penetration in the walls of large chemical tanks. The work described herein involved development and characterization of various novel conductive nanocomposites from polymeric feedstocks as well as carbon nanoparticles. The first approach consisted of using pitch based, liquid crystal molecular additives to polyacrylonitrile (PAN) to create novel electrospun carbon nanofibers. Raman spectroscopy confirmed the increase of an ordered structure in PAN/pitch based carbon nanofibers by analyzing the sharpness of the G band. As a result, the addition of pitch increased the degree of graphene alignment because of the high amount of liquid crystal present in the pitch. This structure led to enhanced physical properties of the carbon nanofibers. The second approach used a conductive network of conjugated polymer (polyaniline, PAni) nanoparticles dispersed in a blend of polyvinylpyrrolidone (PVP) and polyurethane (PU). PAni was synthesized using an in situ polymerization method which resulted in colloidal PAni or PAni nanowires. PAni nanowires self-assembled into scattered fractal networks. After adding PU, a concentrated PAni/PVP phase occurred. Such a phenomenon was attributed to the balance between blocking force and van der Waals force. When the surface tension is the determining factor in the 'island', the round shaped phase separation occurs. The surface tension and van der Waals force were two determining factors in the formation of bi-continuous phase separation. When the forces were in equilibrium, a fractal network structure was formed and the polymer blends were very stable. A flexible conductive fabric was successfully prepared by coating the conductive ternary mixture onto a non-woven fabric. The last approach uses carbon na (open full item for complete abstract)

Committee: Khalid Lafdi (Committee Chair); Donald Klosterman (Committee Member); Erick Vasquez (Committee Member); Vikram Kuppa (Committee Member) Subjects: Materials Science; Nanotechnology; Polymers

Doctor of Philosophy (PhD), Wright State University, 2011, Engineering PhD

Lithium-ion battery anodes with a nanostructure of randomly dispersed carbon nanofibers (CNFs), carbon nanotubes (CNTs), and nanoparticles of tin-oxide or silicon were fabricated and tested in order to develop high capacity, easily manufactured anodes. In these anodes, a mesh of CNTs and CNFs form a conductive network within which the nanoparticles of tin-oxide are suspended. The CNT network directs electron flow to and from the nanoparticles while accommodating their volume changes. The CNFs were intended to aid electron transport by serving as conduction channels between the CNTs and the current collector. Secondarily, the CNFs reinforce the physical structure of the anodes. The nanostructure of the anodes allows the electrolyte to freely penetrate, facilitating ionic transport. In most cases, the components of the anode were held together by Van der Waals forces. Both single-walled carbon nanotubes and multi-walled carbon nanotubes were used in this study in order to determine if there performance would be similar. The anodes take advantage of the specific capacity of tin and tin-oxide, which are 981 mAh/g and 1,491 mAh/g, respectively. Because tin is known to expand to three times its original size when it alloys with lithium, it is used in nanoparticle form for these anodes and thus avoids the tendency of tin to disintegrate. To achieve the desired nanostructure, processing methods based on buckypaper formation were explored. Sonication processes were experimented with to determine the optimum conditions for the fabrication of the anodes. Additionally, additives to aid in the binding of the tin-oxide nanoparticles to the CNTs were explored. These included the addition of polyvinylidene fluoride (PVDF) or carbonized phenolic resins. Anodes were found to exhibit the highest reversible capacity when the processing times were kept to a minimum. This was most likely due to the tendency of CNTs to shorten when sonicated. The shorter sonication times were sufficient (open full item for complete abstract)

Committee: Tarun Goswami DSc (Advisor); Ronald Coutu, Jr. PhD (Committee Member); Hong Huang PhD (Committee Member); Bor Jang PhD (Committee Member); Sharmila Mukhopahyay PhD (Committee Member) Subjects: Engineering

PhD, University of Cincinnati, 2005, Engineering : Mechanical Engineering

Carbon Nanotubes (CNT) have unique properties that can be used to form smart materials. This is a recent area of research, and little work has been done beyond the invention of buckypaper electrochemical actuators. The objective of this dissertation is to investigate the piezoresistive and electrochemical properties of Single Wall Carbon Nanotubes (SWNT), Multi-Wall Carbon Nanotubes (MWNT) and nanotube polymer composite materials. Based on these properties, a strain sensor, a corrosion sensor, a power transducer, and an actuator were developed in this dissertation. These new nanotube-based smart materials have unique advantages and also limitations when compared to existing smart materials. One nice advantage is the multi-functionality of the material. This is illustrated by a sensor developed in this study that simultaneously uses both the piezoresistivity and electrochemical impedance properties of carbon nanotubes for Structural Health Monitoring (SHM) applications. In addition, a biomimetic Artificial Neural System (ANS) was proposed that can cover large areas and monitor the health of a structure in real time, much like the neural system in the human body. The nanotube based sensor system can be easily installed on large structures using a spray-on technique, making the sensor low cost and practical. The characteristics of the sensors developed were modeled and verified by experiments. Also, Carbon Nanofibers (CNF), which are similar to nanotubes, were investigated for use as a low cost sensor material in the study. Power generation using nanotubes and nanofibers in aqueous and dry environments was also investigated. The aim was to provide autonomous power for a SHM sensor system. The voltage output of the nanotube power cell was determined for a few different ionic liquids and polymers. An interesting mechanism of power generation for the dry CNT material was found. An electrostatically charged material reciprocating perpendicular to the nanotube film produced (open full item for complete abstract)

Committee: Mark Schulz (Advisor) Subjects: Engineering, Mechanical

Doctor of Philosophy, University of Akron, 2013, Polymer Engineering

Dispersion of nanofillers in rubber nanocomposites and distribution of components and their interaction in rubber blends is known to significantly affect their rheology and performance characteristics. Application of ultrasonic waves during extrusion is considered a possible means to influence compounding of polymer nanocomposites and polymer blends. The present study is devoted to the ultrasonically aided extrusion of natural rubber (NR) and styrene butadiene rubber (SBR) compounds filled with carbon black (CB), carbon nanotube (CNT) and carbon nanofiber (CNF) and NR/SBR blends. The ultrasonic treatment was found to provide a better processibility leading to a significant reduction of the die pressure during extrusion. For SBR nanocomposites, an increase of the ultrasonic amplitude up to certain values caused an increase of the gel fraction and viscosity of compounds, minimum and maximum torques during their curing. Due to the gel formation in SBR under ultrasonic treatment, an increase of the crosslink density, modulus and tensile strength of vulcanizates was observed. In contrast to SBR nanocomposites, the gel formation in NR nanocomposites under ultrasonic treatment was absent, and their properties were little affected by the treatment till an amplitude of 5.0 µm. The ultrasonic treatment of SBR and NR nanocomposites at an amplitude of 7.5 µm led to a decrease of their properties, due to the dominant effect of chain scission. The ultrasonic treatment of SBR/CB and SBR/CNT nanocomposites led to a decrease of the electrical percolation threshold of their vulcanizates due to the ultrasonically induced uneven distribution of fillers as observed by the optical microscopy. The latter was caused by the gel formation in SBR affecting flow behavior of their compounds. The AFM analysis of SBR vulcanizates indicated that the ultrasonic treatment of SBR/CB and SBR/CNT nanocomposites led to a penetration of SBR chains into filler agglomerates. Interestingly, at the same (open full item for complete abstract)

Committee: Avraam Isayev Dr. (Advisor); Robert Weiss Dr. (Committee Member); Erol Sancaktar Dr. (Committee Member); Gary Hamed Dr. (Committee Member); Shing-Chung Wong Dr. (Committee Member) Subjects: Polymers

PhD, University of Cincinnati, 2017, Arts and Sciences: Chemistry

The dissertation titled Fabrication and Characterization of Plasmonic and Electrochemical Devices Towards Sensing Applications will discuss the fabrication and characterization of patterned gold nanorods, gold nanorings and vertically aligned carbon nanofibers (VACNFs) towards biological and chemical sensing applications. The first two research chapters will discuss the plasmonic studies conducted in the Sagle Laboratory at the University of Cincinnati on the fabrication of patterned gold nanorods and inverted gold nanoring arrays using alumina, hole-mask colloidal lithography (HCL) and/or nanosphere lithography (NSL) as sacrificial templates for biological sensing applications. Additionally, the morphological characterization using atomic force microscopy as well as the characterization of their optical properties using UV-Vis spectroscopy will be elaborated on. The subsequent four research chapters will then focus on the electrochemical studies done in collaboration with the Sagle, Heineman and Koehne Laboratories at the University of Cincinnati and Center for Nanotechnology at the NASA Ames Research Center on the fabrication and characterization of patterned vertically aligned carbon nanofiber electrode arrays using HCL for chemical sensing. Moreover, the surface characterization of the VACNFs using scanning electron microscopy in addition to the electrochemical characterization of VACNFs and employment as sensing arrays using various electrochemical techniques such as cyclic voltammetry, chronoamperometry and anodic stripping voltammetry will be expanded upon.

Committee: William Heineman Ph.D. (Committee Chair); Laura Sagle Ph.D. (Committee Chair); Jessica Koehne Ph.D. (Committee Member); Peng Zhang Ph.D. (Committee Member) Subjects: Chemistry

MS, University of Cincinnati, 2007, Engineering : Industrial Engineering

Precautionary measures should be employed to ensure the health and safety of workers in plants that carry carbon nanofibers. The objective of this paper is to develop a low cost plan to protect the workers in such plants. Collection methods include walkthroughs, company patents and interviews. A preliminary hazard analysis was conducted. Hazards were controlled by administrative controls, personal protective equipment, and other low cost measures. The hazards observed include various forms of carbon nanofibers, raw materials, and carcinogenic intermediate compounds. Proposed control methods include, but are not limited to procedure definition, training, and respirators. Companies should be proactive in addressing the health of their workers. Health and safety plans should be strictly enforced. While the scientific community continues to debate the health effects, companies should take precautionary measures to protect their workers. This paper provides a feasible health and safety plan for an emerging industry.

Committee: Dr. Ashraf Genaidy (Advisor) Subjects: Engineering, Industrial

Doctor of Philosophy in Engineering, University of Toledo, 2011, Chemical Engineering

Polymer nanocomposites (PC) have gained considerable attention recently because of the wide range of properties they can provide. However, design of a high loading PC with uniform dispersion and good interfacial interaction between the nanofibers and polymer has been a challenging issue. In this work, techniques to develop and characterize a novel high loading functional nanofiber network (FNN) with enhanced mechanical strength, conductivity and improved gas transport properties are discussed. These FNN materials consist of polymer matrix, nanofiber network and bound functional groups to nanofiber surface. The nanofibers form a highly connected network or mesh, polymer matrix provides mechanical stability and processiblity to the resulting composite. Functional groups which are covalently bound to the surface of the nanofiber provide compatibility between nanofibers and polymer matrix and also desirable properties such as in the case of gas separation they react reversibly with the target species. Processing methods to in corporate functionalized carbon nanofiber (CNF) poly(dimethylsiloxane) (PDMS) were investigated. Possible applications for FNN were studied and a comprehensive characterization of the composite was performed in order to understand the impact of incorporation of CNF and different surface functionality on the physical and electrical properties on the PDMS matrix. Also, the CNF were functionalized with the following classes of groups to investigate the effect of surface chemistry of interfacial region on the transport properties: 1.No affinity group: this includes pristine CNF (CNF- P), oxidized CNF (CNF-OX) and PDMS (OH) functionalized CNF (CNF- PDMS (OH)). Inclusion of these fibers results in increase in stiffness of matrix and reduction in free volume. This is expected to translate to a decrease in permeability of all gases studied. 2.Small molecule with affinity groups: This includes ionic liquid functionalized CNF, PDMS (NH2) functionalized (open full item for complete abstract)

Committee: Maria Coleman PhD (Committee Chair); Saleh Jabarin PhD (Committee Member); Isabel Escobar PhD (Committee Member); Jamie Hestekin PhD (Committee Member); Yakov Lapitsky PhD (Committee Member) Subjects: Chemical Engineering; Chemistry; Materials Science; Nanotechnology

Master of Science, The Ohio State University, 2009, Mechanical Engineering

Conventional fiber reinforced plastics (FRP's) have long been important if not indispensable in many crucial applications such as transportation, renewable energy, defense applications, as well as many others. Composite materials are of interest to these industries due to their attractive properties including high strength to weight ratio and high modulus to weight ratio. Comprehensive research has been conducted on conventional composite materials to optimize their processing parameters as well as optimize their mechanical behavior and reliability. Although composites provide excellent mechanical properties, certain applications demand improved mechanical behavior as well as the presence of additional properties. Recent developments in polymers have developed nanocomposites, which are composites reinforced by nanoparticles. In these materials, the nanoparticles have shown great enhancements in mechanical properties, thermal properties, and electrical properties. Nevertheless, these composites lack the strength for applications where FRP's are currently used. The addition of nanoparticles as reinforcement to conventional composites shows great promise to not only enhance the existing properties of these composites, but also add many other properties that would maximize their applications. The promise of substantial multifunctional improvements to the behavior of conventional composites does not come without a cost. The effective reinforcement of the desired properties is a direct function of nanoparticle selection and proper dispersion of such nanoparticles. The objective of this research proposal is to develop long fiber reinforced polymer nanocomposites that combine conventional composites with the added benefits of nanocomposites. One of the main challenges involved in the successful enhancement of properties through the addition of nanoparticles is to overcome the problem of poor dispersion in the polymer matrix. Therefore novel state-of-the-art methods of inco (open full item for complete abstract)

Committee: Ly Lee PhD (Advisor); Jose Castro PhD (Committee Member) Subjects: Engineering; Plastics; Polymers

Master of Science (MS), Ohio University, 2007, Mechanical Engineering (Engineering)

This thesis focuses on the design, manufacture, and testing of discharge electrodes made from composites for use in electrostatic precipitators (ESP). Standard industry ESP's use carbon steel, or stainless steel as the base material for constructing discharge electrodes. The electrodes need to be conductive and resist corrosive environments. It is proposed that a conductive polymer matrix composite material can be used in place of the steel to achieve both the necessary conductivity performance, and withstand the corrosive environments in the ESP.

Committee: Khairul Alam (Advisor) Subjects:

Doctor of Philosophy (PhD), Ohio University, 2005, Industrial and Manufacturing Systems Engineering (Engineering)

Vapor grown carbon fiber (VGCF) is a new class of highly graphitic carbon nanofiber and offers advantages of economy and simpler processing over continuous-fiber composites. VGCF used in this work (Pyrograf® III) is grown by means of gas phase catalyst synthesis. The diameter of this fiber ranges from 60 and 200 nanometers and the length varies from 50 to 100 micrometers. There are several issues that must be resolved before VGCF can be a suitable reinforcement. The VGCF must be dispersed in the polymer matrix, a good interface with matrix must be obtained, and the VGCF must be aligned in a specific direction. The object of this study is the extrusion of VGCF/nylon composites. To produce the composite, VGCF and nylon 6 were premixed, and then extruded by twin-screw extruder. An annular converging die was used to produce different volume fractions of VGCF/nylon 6 composite in the form of a continuous strand. SEM analysis and X-ray diffraction results showed that VGCF is well dispersed, wetted, and aligned in the nylon 6 matrix. The tensile strength and modulus for extruded VGCF/nylon 6 composites increased as VGCF volume fraction increased, whereas the ductility decreased. For composite strands subjected to additional extension by drawing, it was seen that both the tensile strength and modulus of composites were increased as draw ratio increased. The theoretical strength prediction performed in this study is a combination of a strength prediction model based on fiber alignment, a model for fiber rotation in the polymer melt, and POLYFLOW simulation, which are sequentially correlated. The theoretical prediction was comparable with experimental results when fiber orientation was evaluated by x-ray diffraction; but the theory overestimated composite strength when fiber rotation was incorporated with the model.

Committee: M. Alam (Advisor) Subjects:

Doctor of Philosophy (Ph.D.), University of Dayton, 2010, Materials Engineering

This study explored the use of a high energy electron beam as the only available technique for selective area surface modification of carbon nanofibers through controlled parameters such as radiation dose, sample temperature, and environment. The application of this variable space led to the production of unique morphological features on the nanofiber surfaces. Several analytical techniques were used to establish the mechanism for these surface modifications, including microscopy, spectroscopy, thermal analysis, and gas adsorption. Depending on the exposure parameters, a nanofiber surface rich with some or all of the following was created: i) free radicals, ii) chemisorbed or physisorbed functional groups, iii) surface roughness from peeling and recombination of graphene layers, and iv) activated carbon surface with nano to meso porosity. The demonstrated consequences of these selective modifications were improved dispersion of the nanofibers in liquid and good bonding with epoxy. Ultimately this process will give the user custom control over the surface interaction of carbon nanofibers with other media such as liquids, polymer resins, gas probes, etc.

Committee: Donald Klosterman PhD (Committee Chair); Khalid Lafdi PhD (Committee Co-Chair); Daniel Eylon D.Sc (Committee Member); Charles Browning PhD (Committee Member) Subjects: Materials Science

Doctor of Philosophy, University of Akron, 2011, Polymer Science

Evaporation and the associated solidification are important factors that affect the diameter of electrospun nanofibers. The evaporation and solidification of a charged jet were controlled by varying the partial pressure of water vapor during electrospinning of poly(ethylene oxide) from aqueous solution. As the partial pressure of water vapor increases, the solidification process of the charged jet becomes slower, allowing elongation of the charged jet to continue longer and thereby to form thinner fibers. The morphology and internal structure of electrospun poly(vinylidene fluorides) nanofibers were investigated. Low voltage high resolution scanning electron microscopy was used to study the surface of electrospun nanofibers. Control of electrospinning process produced fibers with various morphological forms. Fibers that were beaded, branched, or split were obtained when different instabilities dominated in the electrospinning process. The high ratio of stretching during electrospinning aligns the polymer molecules along the fiber axis. A rapid evaporation of solvent during electrospinning gives fibers with small and imperfect crystallites. These can be perfected by thermal annealing. Fibers annealed at elevated temperature form plate-like lamellar crystals tightly linked by tie molecules. Electrospinning can provide ultrafine nanofibers with cross-sections that contain only a few polymer molecules. Ultrafine polymer nanofibers are extremely stable in transmission electron microscope. Electrospun nanofibers suspended on a holey carbon film showed features of individual polymer molecules. Carbon fibers with diameters ranging from 100 nm to several microns were produced from mesophase pitch by a low cost gas jet process. The structure of mesophase pitch-based carbon fibers was investigated as a function of heat treatment temperatures. Submicron-sized graphene oxide flakes were prepared by a combination of oxidative treatment and ultrasonic radiation. Because pitch i (open full item for complete abstract)

Committee: Darrell Reneker Dr. (Advisor); Gary Hamad Dr. (Committee Member); Stephen Z. D. Cheng Dr. (Committee Member); Shi-Qing Wang Dr. (Committee Member); George Chase Dr. (Committee Member) Subjects: Polymers

Doctor of Philosophy, University of Akron, 2010, Chemical Engineering

For environmental protection, the suppression of automotive exhausts such as nitrogen oxides (NOx) and carbon monoxide (CO) is very important. These gases are potential health hazards and green house gases. Burning of hydrocarbon (HC) ideally leads to the formation of water and carbon dioxide; however, due to incomplete combustion and temperatures fluctuations reached in the combustion chamber, the exhaust contains significant amounts of pollutants which need to be transformed into harmless compounds. Hence this concern triggered the need for stringent environmental regulations which resulted in the introduction of catalytic devices in automobiles. Traditionally, the catalyst is impregnated onto a porous substrate. The limitation of this method is the difficulty involved in controlling the catalyst particle size during the sintering or reduction steps that result in high temperature agglomeration effects. In the present work, a novel approach has been developed wherein the noble metal nanocatalysts have been incorporated on ceramic nanofibers by the electrospinning process. The catalysts on ceramic nanofibers increase the overall exposed catalyst area and simultaneously immobilize the catalyst to minimize catalyst loss. A small amount of the catalyst incorporated into ceramic nanofibers was mixed with microfibers to fabricate a filter disk by vacuum molding technique. This filter disk termed as ‘catalytic filter' is a combination of catalytic elements and filter. The catalyzed ceramic nanofiber augmented microfiber filter media can be used for two applications: reduction of NOx and oxidation of CO and for enhanced particulate removal. This filter would include advantages such as light weight structure, optimization of precious metals, high capture efficiency, high surface area, highly interconnected network of pores and high permeability. The key aspects in this dissertation can be divided into six parts: fabrication of catalytic filters and their optimization (open full item for complete abstract)

Committee: Dr. George Chase (Advisor); Edward Evans PhD (Committee Member); Steven Chuang PhD (Committee Member); Subramaniya Hariharan PhD (Committee Member); Rex Ramsier PhD (Committee Member) Subjects: Chemical Engineering; Environmental Engineering

Doctor of Philosophy, University of Akron, 2008, Chemical Engineering

The main sources of NOx are diesel engines, automotives, electric utilities, other industrial, commercial, and residential sources that burn fuels at high temperature. The control and abatement of NOx emissions are important because of their harmful effects on the human body and the environment. The strict regulations of NOx emissions and the growing demand for power compel new design of catalytic materials for pollution removal. The most common method for car exhaust NOx treatment involves wet impregnation of noble metals on ceramic substrates. In this work, catalytic nanoparticles doped on nanofiber enhanced ceramic fibrous filter medium structure are developed as an alternative method. The noble metals, palladium, platinum and rhodium doped ceramic nanofibers, are synthesized using electrospinning and are incorporated into the micro-fibrous filter. We have discovered ceramic nanofiber containing noble metals also work in liquid phase catalysis by converting styrene to ethylbenzene at room temperature and atmospheric pressure. The reaction temperature is varied and the filters are tested for decomposition of nitric oxide and carbon monoxide using nanofiber based fibrous filter. Carbon dioxide, nitrogen and nitrous oxide gases were produced. Produced nitrous oxide gas was consumed by reacting with carbon monoxide. The efficiency of the catalytic fibrous filter was similar to commercial catalytic converter by adding of smaller amount of catalyst doped on alumina microfibers. As the amount of catalyst in the fibrous filter media increases the temperature at which all NO disappears decreases. As the inlet concentration of NO gas decreases, all NO disappears from the outlet at a lower temperature. As the face velocity through the fibrous filter media increases, efficiency becomes lower as the residence time of gases through the media decreases. We also tested a catalytic fibrous filter media containing Pd, Pt and Rh, and the performance is similar to that of catalytic (open full item for complete abstract)

Committee: George G. Chase PhD (Advisor) Subjects: Chemical Engineering; Environmental Engineering

Doctor of Philosophy, University of Akron, 2006, Polymer Science

Carbon nanofiber (CNF) and carbon nanotube (CNT) composites have interesting mechanical and electrical properties that make these composites interesting for reinforcing applications. These applications require good dispersion of CNF within a polymeric matrix. Presently high shear methods, such as twin screw extrusion, are used to make well dispersed CNF composites but these methods reduce the physical properties due to a reduction in the aspect ratio of the CNF. Low shear methods to functionalize CNT and CNF have been used to obtain good dispersion while maintaining the high aspect ratio. In this research three ways of making CNF/polymer composites by low shear methods were explored. The first reaction used bisphenol A cyclic carbonate oligomer as a low molecular weight precursor. The oligomers were polymerized to disperse the CNF within the matrix. These composites were characterized by electrical resistivity, transmission electron microscopy (TEM), scanning electron microscopy (SEM), thermogravametric analysis (TGA) and gel permeation chromatography (GPC). The composites had a percolation threshold at 6 wt % CNF decreasing the resistivity to 10 4ohm•cm. The second way used heterocoagulation where a cationic polystyrene latex was combined with anionically charged oxidized CNF. The composites were melt pressed and characterized using electrical resistivity, SEM, and TGA. The percolation threshold was 2 wt % and the resitivity dropped to 10 6ohm•cm. Finally, it was found that synthesizing a hyperbranched polyol was possible by chemically modifying oxidized CNF with glycidol and BF 3OEt 2. The resulting polyol CNF were characterized by TGA, Fourier transform infrared spectroscopy (FTIR), TEM, and X-ray photoelectron spectroscopy (XPS). The OH groups were reacted with heptafluorobutyryl chloride to determine the amount of OH in the sample. The resulting fluorinated composite was characterized by FTIR and elemental analysis. The amount of OH for the polyol CNF increased (open full item for complete abstract)

Committee: William Brittain (Advisor) Subjects: Chemistry, Polymer

Doctor of Philosophy, University of Akron, 2013, Polymer Engineering

A new, simple, and effective method was developed for production of fibers from polymer solutions with diameters ranging from a few tens of nanometers to a few micrometers. The process, termed gas jet nanofibers (GJF), bears several similarities and contrasts with electrospinning and melt-blowing processes. The method capitalizes on a high velocity expanding gas jet to turn polymer solutions streaming from nozzles into fibers with smooth or wrinkled fiber surface morphology and with core-shell and side-by-side arrangements. The polymer solution is brought in contact with the gas jet on a flat surface, at the tip of a circular needle, and on the surface a pendant drop. The fiber diameter bears relationship with capillary number of the liquid jet and polymer concentration in the solution. Several levels of fiber conglutination are observed as function of the collection distance from the nozzle. The dynamics of the formation of the fiber in the GJF process was inferred from the high speed video images of the liquid jet emanating from the nozzles. The fiber diameter attenuation was found to originate from flapping and bending instabilities and concurrent solvent evaporation. The fiber is initiated by a single liquid jet formed as the liquid emerges from each nozzle configuration. The liquid jets of diameters from around 40 µm to 600 µm are attenuated to the sub-micrometer level within a small distance from the point of liquid-gas contact. The process adaptability was demonstrated with several case studies. First, the production of compound fibers with core-shell and side-by-side configurations was studied for pair of immiscible polymers. Polyvinyl acetate (PVAc), polyethylene oxide (PEO), and polyvinyl pyrrolidone (PVP) were used to create compound fibers with different sizes and configurations. Second, the production of bi-component nanofibers with controlled morphology produced from homogeneous solutions of an immiscible pair of polymers in a miscible pair o (open full item for complete abstract)

Committee: Sadhan Jana Dr. (Advisor); Darrell Reneker Dr. (Advisor); Avraam Isayev Dr. (Committee Member); Erol Sancaktar Dr. (Committee Member); Ernie Pan Dr. (Committee Member); George Chase Dr. (Committee Member) Subjects: Chemical Engineering; Polymer Chemistry; Polymers